Microglia and HIV/AIDS

1. Morner A, Thomas JA, Bjorling E, Munson PJ, Lucas SB, McKnight A (2003) Productive HIV-2 infection in the brain is restricted to macrophages/Microglia. AIDS 17:1451-1455
   Abstract: OBJECTIVES: HIV-2 can use a broader range of co-receptors than HIV-1 in vitro, and is less dependent on CD4 for infection. The aim of this study was to detect productive HIV-2 infection in the brain and investigate whether HIV-2 has an expanded tropism for brain cells in vivo, in comparison with HIV-1, which productively infects macrophages/Microglia. DESIGN: Brain samples taken at autopsy from eight patients who died from AIDS, six HIV-2 and two HIV-1/HIV-2 dually seropositive, with HIV encephalitis (HIVE), collected in Abidjan, Cote d'Ivoire in 1991, were examined for the presence and localization of productive HIV-2 infection. METHODS: Using immunohistochemistry, the presence of HIV-2 p26 in formalin-fixed, wax-embedded brain tissue sections was investigated. Double-staining with glial fibrillary acidic protein (GFAP),

2. Bell JE, Arango JC, Robertson R, Brettle RP, Leen C, Simmonds P (2002) HIV and drug misuse in the Edinburgh cohort. J.Acquir.Immune.Defic.Syndr. 31 Suppl 2:S35-S42
   Abstract: The Edinburgh cohort of intravenous drug users (IVDUs) became infected with HIV between 1983 and 1984. Before the era of effective therapy, many of these infected IVDUs displayed cognitive impairments on progressing to AIDS and were found to have HIV encephalitis (HIVE). Full autopsies were conducted on these patients, providing an opportunity to study the intersecting pathology of pure HIVE and drug use. High proviral load in the brain correlated well with the presence of giant cells and HIV p24 positivity. In presymptomatic HIV infection, IVDUs were found to have a lymphocytic infiltrate in the central nervous system (CNS). Apart from the expected Microglial activation in the presence of HIV infection of the CNS, drug use in its own right was found to be associated with Microglial activation. Examination of HIV-negative IVDUs revealed a number of neuropathologic features, including Microglial activation, which may underpin HIV-related pathology in the CNS. HIV isolated from different regions of the brain was exclusively of R5-tropic type throughout the course of infection. Detailed studies of p17 and V3 sequences suggest that viral sequestration occurs in the CNS before the onset of AIDS and that increasing diversity of HIV variants within the brain is associated with increasing severity of HIVE. Because brain isolates have proved to be different from those in lymphoid tissue (and blood), it is likely that selective neuroadaptive pressures operate before HIVE supervenes. Drug abuse may be synergistic in this process through activation of Microglia, breakdown of the blood-brain barrier, and direct neurotoxicity. Collections of clinically well-characterized HIV-infected tissues such as those in the Edinburgh Brain Bank are a vital resource to support ongoing studies of viral pathogenesis in the CNS and interactions with drug abuse

3. Clements JE, Babas T, Mankowski JL, Suryanarayana K, Piatak M, Jr., Tarwater PM, Lifson JD, Zink MC (2002) The central nervous system as a reservoir for simian immunodeficiency virus (SIV): steady-state levels of SIV DNA in brain from acute through asymptomatic infection. J.Infect.Dis. 186:905-913
   Abstract: Latent reservoirs of human immunodeficiency virus (HIV) present significant challenges for eradicating HIV from infected persons, particularly reservoirs in the brain established during acute infection. A simian immunodeficiency virus (SIV)/macaque model of HIV dementia was used to show that viral DNA levels in the brain remained at constant levels from acute through asymptomatic infection, despite significant down-regulation of viral RNA in the brain after the acute phase of infection. Viral replication in the brain coincided with activation of macrophages and Microglia in the central nervous system; down-regulation of viral replication coincided with increased infiltration of cytotoxic lymphocytes and reduced activation of macrophages and Microglia in the brain. Comparison of viral genotypes in the central nervous system and peripheral blood mononuclear cells suggests that recrudescence of viral replication in brain occurs by reactivation of latent viral DNA. Latent virus in the brain must be considered in therapeutic strategies to eliminate HIV from infected persons

4. Cosenza MA, Zhao ML, Si Q, Lee SC (2002) Human brain parenchymal Microglia express CD14 and CD45 and are productively infected by HIV-1 in HIV-1 encephalitis. Brain Pathol. 12:442-455
   Abstract: Microglia are endogenous brain macrophages that show distinct phenotypes such as expression of myeloid antigens, ramified morphology, and presence within the neural parenchyma. They play significant roles in a number of human CNS diseases including AIDS dementia. Together with monocyte-derived (perivascular) macrophages, Microglia represent a major target of HIV-1 infection. However, a recent report challenged this notion based on findings in SIV encephalitis. This study concluded that perivascular macrophages can be distinguished from parenchymal Microglial cells by their expression of CD14 and CD45, and that macrophages, but not Microglia, are productively infected in SIV and HIV encephalitis. To address whether parenchymal Microglia are productively infected in HIV encephalitis, we analyzed expression of CD14, CD45 and HIV-1 p24 in human brain. Microglia were identified based on their characteristic ramified morphology and location in the neural parenchyma. We found that parenchymal Microglia are CD14+ (activated), CD45+ (resting and activated), and constitute approximately two thirds of the p24+ cells in HIV encephalitis cases. These results demonstrate that Microglia are major targets of infection by HIV-1, and delineate possible differences between HIVE and SIVE. Because productively infected tissue macrophages serve as the major viral reservoir, these findings have important implications for AIDS

5. D'Aversa TG, Weidenheim KM, Berman JW (2002) CD40-CD40L interactions induce chemokine expression by human Microglia: implications for human immunodeficiency virus encephalitis and multiple sclerosis. Am.J.Pathol. 160:559-567
   Abstract: CD40 is a protein on Microglia that is up-regulated with interferon (IFN)-gamma and is engaged by CD40L, found on CD4+ T cells, B cells, and monocytes. These interactions may be important in central nervous system inflammatory diseases. Microglia have been shown to be a source of chemokines, whose expression plays a key role in central nervous system pathologies. We examined the expression of CD40 on Microglia in human immunodeficiency virus (HIV) encephalitic brain, and the effects of CD40-CD40L interactions on the expression of chemokines by cultured Microglia. We found significantly increased numbers of CD40-positive Microglia in HIV-infected brain tissue. Treatment of cultured Microglia with IFN-gamma and CD40L increased expression of several chemokines. IFN-gamma- and CD40L-induced MCP-1 protein was mediated by activation of the ERK1/2 MAPK pathway, and Western blot analysis demonstrated phosphorylation of ERK1/2 upon stimulation of Microglia. In contrast, IFN-gamma- and CD40L-induced IP-10 protein production was mediated by the p38 MAPK pathway. Our data suggest a mechanism whereby CD40L+ cells can induce Microglia to secrete chemokines, amplifying inflammatory processes seen in HIV encephalitis and multiple sclerosis, and implicate CD40-CD40L interactions as a target for interventional strategies

6. Garden GA (2002) Microglia in human immunodeficiency virus-associated neurodegeneration. Glia 40:240-251
   Abstract: Infection with the human immunodeficiency virus (HIV) is associated with a syndrome of cognitive and motor abnormalities that may develop in the absence of opportunistic infections. Neurons are not productively infected by HIV. Thus, one hypothesis to explain the pathophysiology of HIV-associated dementia (HAD) suggests that signals released from other infected cell types in the CNS secondarily lead to neuronal injury. Microglia are the predominant resident CNS cell type productively infected by HIV-1. Neurologic dysfunction in HAD appears to be a consequence of Microglial infection and activation. Several neurotoxic immunomodulatory factors are released from infected and activated Microglia, leading to altered neuronal function, synaptic and dendritic degeneration, and eventual neuronal apoptosis. This review summarizes findings from clinical/pathological studies, animal models, and in vitro models of HAD. Most of these studies support the hypothesis that altered Microglial physiology is the nidus for a cascade of events leading to neuronal dysfunction and death. Several molecular mediators of neuronal injury in HAD that emanate from Microglia have been identified, and strategies for altering the impact of these neurotoxins are discussed

7. Garden GA, Budd SL, Tsai E, Hanson L, Kaul M, D'Emilia DM, Friedlander RM, Yuan J, Masliah E, Lipton SA (2002) Caspase cascades in human immunodeficiency virus-associated neurodegeneration. J.Neurosci. 22:4015-4024
   Abstract: Many patients infected with human immunodeficiency virus-1 (HIV-1) develop a syndrome of neurologic deterioration known as HIV-associated dementia (HAD). Neurons are not productively infected by HIV-1; thus, the mechanism of HIV-induced neuronal injury remains incompletely understood. Several investigators have observed evidence of neuronal injury, including dendritic degeneration, and apoptosis in CNS tissue from patients with HAD. Caspase enzymes, proteases associated with the process of apoptosis, are synthesized as inactive proenzymes and are activated in a proteolytic cascade after exposure to apoptotic signals. Here we demonstrate that HAD is associated with active caspase-3-like immunoreactivity that is localized to the soma and dendrites of neurons in affected regions of the human brain. Additionally, the cascade of caspase activation was studied using an in vitro model of HIV-induced neuronal apoptosis. Increased caspase-3 proteolytic activity and mitochondrial release of cytochrome c were observed in cerebrocortical cultures exposed to the HIV coat protein gp120. Specific inhibitors of both the Fas/tumor necrosis factor-alpha/death receptor pathway and the mitochondrial caspase pathway prevented gp120-induced neuronal apoptosis. Caspase inhibition also prevented the dendrite degeneration observed in vivo in transgenic mice with CNS expression of HIV/gp120. These findings suggest that pharmacologic interventions aimed at the caspase enzyme pathways may be beneficial for the prevention or treatment of HAD

8. Gartner S, Liu Y (2002) Insights into the role of immune activation in HIV neuropathogenesis. J.Neurovirol. 8:69-75
   Abstract: How does HIV infection lead to the development of central nervous system disease? Central to this question is identification of the relative contributions of (1) the virus, (2) its host cells, and (3) secondary or downstream events to the pathological process. These are re-examined in this brief review. Also, a greater appreciation for the role of systemic events in neuroinflammation is emerging, with likely relevance to HIV-associated dementia. We propose here a model for HIV neuropathogenesis that highlights the role of systemic monocyte activation and subsequent neuroinvasion in initiating the disease

9. Grassi MP, Clerici F, Vago L, Perin C, Borella M, Nebuloni M, Moroni M, Mangoni A (2002) Clinical aspects of the AIDS dementia complex in relation to histopathological and immunohistochemical variables. Eur.Neurol. 47:141-147
   Abstract: To correlate cerebral histopathological and immunohistochemical changes in the neuroclinical features of the AIDS dementia complex (ADC), autopsy results of 28 ADC patients were related, in a retrospective analysis, to scores on a standardised neurological examination performed at neurologic onset. From a histopathological point of view, the cases were classified as follows: 9 cases of HIV leucoencephalopathy (HIVL; diffuse myelin damage and rare Microglial nodules), 7 cases of HIV encephalitis (HIVE; several Microglial nodules and no myelin damage) and 12 cases of mixed HIVL and HIVE (HIVL-E). The groups differed significantly with respect to symptoms and CD4 count at neurologic onset, survival and neurological impairment. Immunohistochemically, the interstitial component (p24-positive cells scattered singly within the white matter) was significantly more prevalent in HIVL, and the micronodular component (p24-positive cells confined within Microglial nodules) in HIVE. Neurological damage was worse in cases with a high prevalence of interstitial component or a low prevalence of micronodular component. HIVE, HIVL and HIVL-E are distinct clinical forms of ADC. Neurological impairment is related to white matter damage

10. Hatori K, Nagai A, Heisel R, Ryu JK, Kim SU (2002) Fractalkine and fractalkine receptors in human neurons and glial cells. J.Neurosci.Res. 69:418-426
    Abstract: Fractalkine has been identified as a novel chemokine that exhibits cell adhesion and chemoattractive properties in the central nervous system (CNS), and the fractalkine receptors, CX3CR1, are also expressed in the CNS. In the present study, the expression of fractalkine and fractalkine receptors was investigated in enriched populations of human CNS neurons, astrocytes, and Microglia. In addition, the regulatory role played by protein kinase C (PKC) in fractalkine secretion in neurons was determined in A1 human hybrid neuronal cell line produced between a human cerebral neuron and a human neuroblastoma cell. Human neurons and astrocytes expressed fractalkine mRNA as determined by the revserse transcriptase-polymerase chain reaction (RT-PCR) analysis, while human Microglia preparation did not express the fractalkine message. Human neurons and Microglia expressed CX3CR1 mRNA, but astrocytes did not. These results suggest that fractalkine secreted by CNS neurons and astrocytes produce biological effects in neurons and Microglia. Although phorbol ester did not change the expression of fractalkine mRNA level in A1 hybrid neurons, it did upregulate fractalkine secretion over unstimulated controls. This upregulation of fractalkine production was suppressed by the treatment with Ro32-0432, a PKC inhibitor. These results indicate that intracellular signals transduced by PKC play an important role in the regulation of soluble fractalkine at the post-transcriptional level in human neurons. As for the biological function of fractalkine, extracellularly applied fractalkine increased the number of bromodeoxyuridine-labeled Microglia 3-fold over the untreated controls, indicating fractalkine induces proliferation of human Microglia. These observations suggest that fractalkine released by injured neurons could induce proliferation, activation and/or migration of Microglia at the injured brain sites

11. Hughes PM, Botham MS, Frentzel S, Mir A, Perry VH (2002) Expression of fractalkine (CX3CL1) and its receptor, CX3CR1, during acute and chronic inflammation in the rodent CNS. Glia 37:314-327
    Abstract: In this study, we investigate the expression of fractalkine (CX3CL1) and the fractalkine receptor (CX3CR1) in the naive rat and mouse central nervous system (CNS). We determine if the expression of this chemokine and its receptor are altered during chronic or acute inflammation in the CNS. In addition, we determine if CX3CL1, which has been reported to be chemoattractant to leukocytes in vitro, is capable of acting as a chemoattractant in the CNS in vivo. Immunohistochemistry was performed using primary antibodies recognizing soluble and membrane-bound CX3CL1 and the N-terminus of the CX3CR1. We found that neurons in the naive rodent brain are immunoreactive for CX3CL1 and CX3CR1, both showing a perinuclear staining pattern. Resident Microglia associated with the parenchyma and macrophages in the meninges and choroid plexus constituitively express CX3CR1. In a prion model of chronic neurodegeneration and inflammation, CX3CL1 immunoreactivity is upregulated in astrocytes and CX3CR1 expression is elevated on Microglia. In surviving neurons, expression of CX3CL1 appears unaltered relative to normal neurons. There is a decrease in neuronal CX3CR1 expression. Acute inflammatory responses in the CNS, induced by stereotaxic injections of lipopolysaccharide or kainic acid, results in activation of Microglia and astrocytes but no detectable changes in the glial expression of CX3CL1 or CX3CR1. The expression of CX3CL1 and CX3CR1 by glial cells during inflammation in the CNS may be influenced by the surrounding cytokine milieu, which has been shown to differ in acute and chronic neuroinflammation

12. Kandanearatchi A, Zuckerman M, Smith M, Vyakarnam A, Everall IP (2002) Granulocyte-macrophage colony-stimulating factor enhances viral load in human brain tissue: amelioration with stavudine. AIDS 16:413-420
    Abstract: BACKGROUND: Granulocyte-macrophage colony-stimulating factor (GM-CSF) is elevated in cerebrospinal fluid in HIV- associated dementia; in addition, therapeutic GM-CSF elevates plasma viral load. OBJECTIVE: To assess the effect of GM-CSF on viral replication and the potential ameliorative effect of antiretroviral therapy. DESIGN: A primary human brain aggregate system is used as a model of the in vivo situation. METHOD: Cultured aggregates were infected with the macrophage tropic strain HIV-1SF162 and then exposed to varying GM-CSF concentrations and 0.3 micromol/l stavudine. Viral replication was assessed by p24 expression in the supernatant and aggregates. Immunohistochemistry identified neurons, astrocytes, Microglia and oligodendrocytes. RESULTS: A GM-CSF concentration of 1 ng/ml resulted in a fivefold increase in Microglial cells, the main HIV cellular reservoir (P = 0.0001). Prior GM-CSF exposure before infection of the aggregates resulted in sixfold increase in p24 levels compared with non-GM-CSF-exposed infected aggregates. Infected aggregates with or without GM-CSF had significant neuronal loss of 50% and 45%, respectively, and astrocytosis. Addition of stavudine to the infected aggregates, even in the presence of GM-CSF, reduced p24 levels to zero and prevented neuronal loss and astrocytosis. CONCLUSIONS: This study demonstrates that GM-CSF enhances viral replication while addition of stavudine prevents this potentially detrimental process

13. Kanmogne GD, Kennedy RC, Grammas P (2002) Infection of baboon Microglia with SIV-HIV recombinant viruses: role of CD4 and chemokine receptors. AIDS Res.Hum.Retroviruses 18:557-565
    Abstract: Microglia constitute the primary cell type infected with HIV in the brain and play a major role in viral persistence in the CNS and in the development of AIDS dementia. Lack of a suitable animal model and limitations in the availability of human tissues hinder most HIV/AIDS studies investigating the neuropathogenesis of AIDS dementia. The aims of this study were to determine whether baboon Microglia can be productively infected with SIV-HIV (SHIV) recombinant viruses in vitro and whether they express HIV-1 receptors and coreceptors. Our results show the presence of mRNA for CD4, CCR5, and CXCR4 chemokine receptors on baboon Microglial cells. Microglia lacked mRNA for the CCR3 chemokine receptor. We also show productive infection of baboon Microglial cells by two SHIV isolates, SHIV-KU and SHIV-89.6P, and blockade of the infection with soluble CD4 protein, CCR5, and CXCR4 monoclonal antibodies. This study demonstrating the feasibility of infecting baboon Microglia with SHIV isolates is an important first step in using the baboon as an alternative nonhuman primate model to study HIV neuropathogenesis

14. Kolson DL (2002) Neuropathogenesis of central nervous system HIV-1 infection. Clin.Lab Med. 22:703-717
    Abstract: Neuronal damage and death are consistent pathologic findings in the brains of patients with ADC, and multiple cell model systems have demonstrated neurotoxicity through the effects of HIV-1 infection in macrophages and Microglia. Brain MRI studies (1H-MRS) indicate that reversible neuronal cell dysfunction occurs early during the course of HIV-1 infection, long before overt symptoms of ADC appear. Epidemiologic studies suggest that a high viral load in the CNS is a major risk factor for ADC and that HAART may significantly reduce, but not eliminate, the risk of developing ADC. Targeted adjunctive therapies administered early are likely necessary to maximize CNS protection against HIV, and rational approaches to such therapy are rapidly evolving through in vitro analysis of the mechanisms of HIV-associated neurotoxicity. Soluble factors released by infected cells may directly or indirectly damage neurons and induce apoptosis at the level of NMDA subtype of glutamate receptors, and NMDA receptor antagonists represent a major therapeutic option currently under intense clinical investigation. Likewise, drugs with antioxidant or free radical scavenging effects offer another rational approach to adjunctive therapy and are also under intense clinical scrutiny. Finally, agents that inhibit neuronal death-signaling pathways (e.g., p38 MAPK inhibitors) and that stimulate cell survival pathways (e.g., Akt/PKB) may represent the next investigational step in designing anti-ADC therapies

15. Li Y, Wang X, Tian S, Guo CJ, Douglas SD, Ho WZ (2002) Methadone enhances human immunodeficiency virus infection of human immune cells. J.Infect.Dis. 185:118-122
    Abstract: Opiate abuse has been postulated to be a cofactor in the immunopathogenesis of acquired immunodeficiency syndrome (AIDS). This study evaluated whether methadone, a drug widely prescribed for the treatment of drug abusers with opioid dependence, affects human immunodeficiency virus (HIV) infection of human immune cells. When added to human fetal Microglia and blood monocyte-derived macrophage cultures, methadone significantly enhanced HIV infection of these cells. This enhancement was associated with the up-regulation of expression of CCR5, a primary coreceptor for macrophage-tropic HIV entry into macrophages. Most importantly, the addition of methadone to the cultures of latently infected peripheral blood mononuclear cells from HIV-infected patients enhanced viral activation and replication. Although the in vivo relevance of these findings remains to be determined, the data underscore the necessity of further studies to define the role of opioids, including methadone, in the immunopathogenesis of HIV infection and AIDS

16. Mankowski JL, Queen SE, Tarwater PM, Fox KJ, Perry VH (2002) Accumulation of beta-amyloid precursor protein in axons correlates with CNS expression of SIV gp41. J.Neuropathol.Exp.Neurol. 61:85-90
    Abstract: Axonal damage represented by accumulation of beta-amyloid precursor protein (beta-APP) develops in numerous central nervous system (CNS) diseases including human immunodeficiency virus (HIV) infection. To study the underlying mechanisms of axonal damage associated with HIV CNS infection, the amount of axonal beta-APP immunostaining in the corpus callosum of 24 simian immunodeficiency virus (SIV)-infected macaques and 3 control macaques was measured by computerized image analysis. The amounts of beta-APP accumulation were then compared with time post-inoculation, extent and character of CNS inflammation, and viral load in the CNS measured by the amount of immunohistochemical staining for the viral transmembrane protein gp41. Significant increases over control values were present in 10 of 24 SIV-infected animals. SIV encephalitis was present in 9 of the 10 animals with elevated beta-APP Increases in beta-APP correlated most strongly with levels of SIV gp41 in the brain (p = 0.005), but significant associations with macrophage infiltration and Microglial activation (p = 0.04) and infiltration by cytotoxic lymphocytes (p = 0.05) also were identified. These data demonstrate that beta-APP accumulation in the white matter of SIV-infected macaques develops during SIV infection in close correlation with levels of viral replication and may serve as a sensitive marker of neuronal/axonal damage mediated by viral proteins

17. McCarthy M, He J, Auger D, Geffin R, Woodson C, Hutto C, Wood C, Scott G (2002) Cellular tropisms and co-receptor usage of HIV-1 isolates from vertically infected children with neurological abnormalities and rapid disease progression. J.Med.Virol. 67:1-8
    Abstract: The longitudinal evolution of HIV-1 phenotypes was studied in a cohort of six vertically infected children with early onset and rapid progression of clinical disease. Among 30 viral isolates obtained from peripheral blood, tropisms for both human blood-derived cells (macrophages, T-lymphocytes), and for human neural (brain-derived) cells (Microglia, astrocytes) were determined, as was chemokine co-receptor usage. All children harbored from birth macrophage-tropic isolates using the CCR5 co-receptor. Two children later developed T-cell tropic isolates with CXCR4 and CCR3 usage. While all six patients developed neurological abnormalities, only three produced neural cell tropic isolates, which used CCR5. However, early and persistent finding of both astrocyte- and Microglia-tropic isolates in one patient did associate with the most rapid progression to brain atrophy among the six patients. Viral phenotypic properties determined in cell culture did not specifically predict clinical features or course, and the development of AIDS did not coincide with, or depend on, the appearance T-tropic, syncytia-inducing viruses

18. Nath A (2002) Human immunodeficiency virus (HIV) proteins in neuropathogenesis of HIV dementia. J.Infect.Dis. 186 Suppl 2:S193-S198
    Abstract: Human immunodeficiency virus (HIV) infection of the nervous system is unique when compared with other viral encephalitides. Neuronal cell loss occurs in the absence of neuronal infection. Viral proteins, termed "virotoxins," are released from the infected glial cells that initiate a cascade of positive feedback loops by activating uninfected Microglial cells and astrocytes. These activated cells release a variety of toxic substances that result in neuronal dysfunction and cell loss. The virotoxins act by a hit and run phenomenon. Thus, a transient exposure to the proteins initiates the neurotoxic cascade. High concentrations of these proteins likely occur in tight extracellular spaces where they may cause direct neurotoxicity as well. The emerging concepts in viral protein-induced neurotoxicity are reviewed as are the neurotoxic potential of each protein. Future therapeutic strategies must target common mechanisms such as oxidative stress and dysregulation of intracellular calcium involved in virotoxin-mediated neurotoxicity

19. Rauer M, Pagenstecher A, Schulte-Monting J, Sauder C (2002) Upregulation of chemokine receptor gene expression in brains of Borna disease virus (BDV)-infected rats in the absence and presence of inflammation. J.Neurovirol. 8:168-179
    Abstract: Infection of adult rats with Borna disease virus (BDV) causes CD8 T cell-mediated meningoencephalitis. Previously, we described a complex pattern of chemokine gene expression in the central nervous system (CNS) of such rats. We now found that expression of chemokine receptor genes CXCR3, CCR5, CX(3)CR1, and CXCR4 was also upregulated, which is in agreement with the predominance in brains of adult infected rats of T cells and monocytes/macrophages that express these receptors. In contrast to these rats, neonatally infected rats (designated PTI-NB) develop a persistent CNS infection associated with neurodegenerative processes in the absence of inflammation. In brains of PTI-NB rats, sustained expression of chemokines also takes place. We therefore analyzed mRNA expression of selected chemokine receptor genes, as well as of the chemokine fractalkine in brains of PTI-NB rats. We observed a marked increase of CCR5 and CX(3)CR1 transcripts in brains of these rats. CX(3)CR1 expressing cells were predominantly Microglia, and upregulation of CX(3)CR1 was mainly due to an increase in the number of CX(3)CR1 expressing Microglia. Fractalkine gene expression was found to be reduced to similar extents in brains of adult and newborn infected rats. These findings might be of relevance with respect to the selective neuronal cell loss observed in brains of PTI-NB rats

20. Ryan LA, Cotter RL, Zink WE, Gendelman HE, Zheng J (2002) Macrophages, chemokines and neuronal injury in HIV-1-associated dementia. Cell Mol.Biol.(Noisy.-le-grand) 48:137-150
    Abstract: Human immunodeficiency virus type-one (HIV- 1)-associated dementia (HAD) is manifested as a spectrum of behavioral, motor and cognitive dysfunctions. The disorder commonly occurs during late stage HIV disease and remains an important complication despite highly active antiretroviral therapies. A metabolic encephalopathy, fueled by neurotoxic secretions from brain mononuclear phagocytes (MP) (macrophages and Microglia) underlies HIV- I neuropathogenesis. One pivotal question, however, is how brain MP evolve from neurotrophic to neurotoxic cells. The interplay between the virus, the macrophage and the neuron has just recently begun to be unraveled. Along with a multitude of other MP secretory products, chemokines effect neuronal function by engaging neuronal receptors then activating pathways that alter synaptic transmission, cell growth, injury and protection. Both neurons and glia secrete chemokines. Interestingly, HIV-1 and its gene products can mimic chemokine neuronal signaling by binding to neuronal chemokine receptors or by other non-specific mechanisms. The elucidation of mechanisms involved in chemokine-mediated neural compromise will likely provide unique insights into the pathogenesis and treatment, not only of HAD, but of a wide range of neurodegenerative disorders

21. Ryzhova EV, Crino P, Shawver L, Westmoreland SV, Lackner AA, Gonzalez-Scarano F (2002) Simian immunodeficiency virus encephalitis: analysis of envelope sequences from individual brain multinucleated giant cells and tissue samples. Virology 297:57-67
    Abstract: Simian immunodeficiency virus (SIV)-infected macaques develop an encephalitis (SIVE) that is pathologically virtually indistinguishable from that associated with HIV infection, with multinucleated giant cells (MNGCs) being the principal histopathological manifestation. To dissect SIV variants responsible for MNGC development, we examined the relationships between env sequences transcribed in individual MNGCs and those from genomic DNA of brain and spleen tissues. The brain-specific variant found in all brain clones was dominant among the clones from MNGCs, suggesting a role in the formation of giant cells. Furthermore, two additional minor groups of sequences were present in MNGCs. One group consisted of sequences closely related to those from spleen, indicating recent and probably multiple episodes of neuroinvasion. The second group represented clones similar or identical to the initial inoculum. The survival of arcHIVal sequences and their activation presumably by the fusion of productively and quiescently infected macrophages/Microglia identify the central nervous system as a possible anatomical reservoir for latent infection

22. Sharshar T, Gray F, Poron F, Raphael JC, Gajdos P, Annane D (2002) Multifocal necrotizing leukoencephalopathy in septic shock. Crit Care Med. 30:2371-2375
    Abstract: OBJECTIVE: Multifocal necrotizing leukoencephalopathy, characterized by multiple microscopic foci of necrosis involving the white matter of the pons, has been described mainly after chemotherapy or radiotherapy for brain cancer and in HIV infection. The role of circulating cytokines has been suggested but remains to be assessed. DESIGN: Prospective case series. SETTING: A 26-bed general medical intensive care unit at a university hospital. PATIENTS: Septic shock patients. MEASUREMENTS AND PATIENTS: In three patients who died from septic shock, careful postmortem examination of the brain was performed, including studies of neuronal apoptosis and cytokine expression. MAIN RESULTS: In one patient, typical lesions of multifocal necrotizing leukoencephalopathy were seen. As compared with control 1 and control 2 who did not have multifocal necrotizing leukoencephalopathy, marked lesions of the pons, including vacuolization, apoptosis, Microglial activation, and expression of tumor necrosis factor-alpha and interleukin-1beta, were observed in the case. Simultaneously, case 1 had markedly increased circulating levels for tumor necrosis factor-alpha, interleukin-1beta, interleukin-6, interleukin-8, interleukin-10, soluble tumor necrosis factor receptor II, and for interleukin-1 receptor antagonist. CONCLUSION: Septic shock is a newly described cause of multifocal necrotizing leukoencephalopathy, probably mediated by an excessive systemic inflammatory response

23. Si Q, Kim MO, Zhao ML, Landau NR, Goldstein H, Lee S (2002) Vpr- and Nef-dependent induction of RANTES/CCL5 in Microglial cells. Virology 301:342-353
    Abstract: Microglia are pivotal in the pathogenesis of AIDS dementia, as they serve as the major target of HIV infection in the CNS. In addition, activation of Microglia correlates best with clinical dementia. Although the beta-chemokine RANTES/CCL5 is important in modulating HIV infection as well as cellular activation, no information is available regarding how its expression is regulated in Microglia by HIV-1. Here we report that RANTES/CCL5 expression is induced in Microglia by HIV-1, but that this requires infection by HIV-1. This conclusion was supported by (1) the delayed kinetics coinciding with viral replication; (2) the lack of effect of X4 viruses; (3) inhibition by the reverse transcriptase inhibitor AZT, and (4) the lack of effect of cytokine antagonists or antibodies. Interestingly, RANTES/CCL5 production was dependent on the viral accessory protein Vpr, in addition to Nef, demonstrating a novel role for Vpr in chemokine induction in primary macrophage-type cells. Furthermore, the specific p38 MAP kinase inhibitor SB203580 augmented chemokine expression in Microglia, indicating a negative role played by p38. These data suggest unique features of RANTES/CCL5 regulation by HIV-1 in human Microglial cells

24. Si Q, Cosenza M, Zhao ML, Goldstein H, Lee SC (2002) GM-CSF and M-CSF modulate beta-chemokine and HIV-1 expression in Microglia. Glia 39:174-183
    Abstract: Significant numbers of patients with acquired immunodeficiency syndrome (AIDS) develop CNS infection primarily in macrophages and Microglial cells. Therefore, the regulation of human immunodeficiency virus type 1 (HIV-1) infection and activation of the brain mononuclear phagocytes subsequent to infection are important areas of investigation. In the current report, we studied the role of granulocyte-macrophage colony-stimulating factor (GM-CSF) and macrophage-CSF (M-CSF) in the expression of antiviral beta-chemokines and HIV-1 p24 in cultures of primary human fetal Microglia. We found that stimulation with GM-CSF or M-CSF induced macrophage inflammatory proteins (MIP-1alpha and MIP-1beta) and augmented RANTES expression, after HIV-1 infection of Microglia. This was not due to the effect of GM-CSF on viral expression because GM-CSF was neither necessary nor stimulatory for viral infection, nor did GM-CSF enhance the expression of env-pseudotyped reporter viruses. Blocking GM-CSF-induced Microglial proliferation by nocodazole had no effect on beta-chemokine or p24 expression. The functional significance of the GM-CSF-induced beta-chemokines was suggested by the finding that, in the presence of GM-CSF, exogenous beta-chemokines lost their anti-HIV-1 effects. We further show that although HIV-1-infected Microglia produced M-CSF, they failed to produce GM-CSF. In vivo, GM-CSF expression was localized to activated astrocytes and some inflammatory cells in HIV-1 encephalitis, suggesting paracrine activation of Microglia through GM-CSF. Our results demonstrate a complex interplay between CSFs, chemokines, and virus in Microglial cells and may have bearing on the interpretation of data derived in vivo and in vitro

25. Su ZZ, Kang DC, Chen Y, Pekarskaya O, Chao W, Volsky DJ, Fisher PB (2002) Identification and cloning of human astrocyte genes displaying elevated expression after infection with HIV-1 or exposure to HIV-1 envelope glycoprotein by rapid subtraction hybridization, RaSH. Oncogene 21:3592-3602
    Abstract: Neurodegeneration and dementia are common complications of AIDS caused by human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system. HIV-1 target cells in the brain include Microglia, infiltrating macrophages and astrocytes, but rarely neurons. Astrocytes play an important role in the maintenance of the synaptic micro-environment and in neuronal signal transmission. To investigate potential changes in cellular gene expression associated with HIV-1 infection of astrocytes, we employed an efficient and sensitive rapid subtraction hybridization approach, RaSH. Primary human astrocytes were isolated from abortus brain tissue and low-passage cells were infected with HIV-1. To identify genes that display both early and late expression modifications after HIV-1 infection and to avoid cloning genes displaying normal cell cycle fluctuations in astrocytes, RNAs were isolated and pooled from 6, 12, 24 h and 3 and 7 day uninfected and infected cells and used for RaSH. Temporal cDNA libraries were prepared from double-stranded cDNAs that were enzymatically digested into small fragments, ligated to adapters, PCR amplified, and hybridized by incubation of tester and driver PCR fragments. By subtracting temporal cDNAs derived from uninfected astrocytes from temporal cDNAs made from HIV-1 infected cells, genes displaying elevated expression in virus infected cells, termed astrocyte elevated genes (AEGs), were identified. Both known and novel AEGs, not reported in current DNA databases, are described that display early or late expression kinetics following HIV-1 infection or treatment with recombinant HIV-1 envelope glycoprotein (gp120). For selected AEGs, expression of their protein products was also tested by Western blotting and found to display elevated expression following HIV-1 infection. The comparable pattern of regulation of the AEGs following HIV-1 infection or gp120 treatment suggest that HIV-1 exposure of astrocytes, even in the absence of productive infection, can induce changes in cellular gene expression

26. Tarozzo G, Campanella M, Ghiani M, Bulfone A, Beltramo M (2002) Expression of fractalkine and its receptor, CX3CR1, in response to ischaemia-reperfusion brain injury in the rat. Eur.J.Neurosci. 15:1663-1668
    Abstract: Fractalkine is a neuronally expressed chemokine that acts through its G-protein-coupled receptor CX3CR1, localized on Microglial and immune cells. Fractalkine might be involved in neuroinflammatory processes secondary to neuronal damage, which normally occur in a time frame of days after ischaemia. We evaluated by in situ hybridization and immunohistochemistry the expression of fractalkine and CX3CR1 in the rat brain, after a transient occlusion of the middle cerebral artery. We found that at 12 h after ischaemia neuronal fractalkine expression was transiently increased in scattered necrotic neurons of the cortex and lost from the ischaemic striatum. At 24 and 48 h after ischaemia, fractalkine immunoreactivity was strongly increased in morphologically intact cortical neurons of the ischaemic penumbra where also the stress-inducible HSP-72 was strongly up-regulated. The intensity of fractalkine immunoreactivity of neurons in the penumbra returned to basal levels at 7 days after ischaemia. Fractalkine synthesis was also induced in endothelial cells of the infarcted area, at 48 h and 7 days after ischaemia. CX3CR1 expression was detected in the activated Microglial cells of the ischaemic tissue 24 and 48 h after ischaemia, and became strongly up-regulated in macrophages/phagocytic Microglia inside the infarcted tissue 7 days after ischaemia. These data suggest that fractalkine may participate in the activation and chemoattraction of Microglia into the infarcted tissue, and contribute to the control of leucocyte trafficking from blood vessels into the injured area

27. Vilhardt F, Plastre O, Sawada M, Suzuki K, Wiznerowicz M, Kiyokawa E, Trono D, Krause KH (2002) The HIV-1 Nef protein and phagocyte NADPH oxidase activation. J.Biol.Chem. 277:42136-42143
    Abstract: Nef, a multifunctional HIV protein, activates the Vav/Rac/p21-activated kinase (PAK) signaling pathway. Given the potential role of this pathway in the activation of the phagocyte NADPH oxidase, we have investigated the effect of the HIV-1 Nef protein on the phagocyte respiratory burst. Microglia (cell line and primary culture) were transduced with lentiviral expression vectors. Expression of Nef did not activate the NADPH oxidase by itself but led to a massive enhancement of the responses to a variety of stimuli (Ca(2+) ionophore, formyl peptide, endotoxin). These effects were not caused by up-regulation of phagocyte NADPH oxidase subunits. Nef mutants lacking motifs involved in the interaction with Vav and PAK failed to reproduce the effects of wild type Nef, suggesting a role for the Vav/Rac/PAK signaling pathway. The following results suggest a key role for Rac in the priming effect of Nef. (i) Inactivation of Rac by Clostridium difficile toxin B abolished the Nef effect. (ii) The fraction of activated Rac1 was increased in Nef-transduced cells, and (iii) the dominant positive Rac1(V12) mutant mimicked the effect of Nef. These results are to our knowledge the first analysis of the effect of Rac activation on the NADPH oxidase in intact phagocytes. Rac activation is not sufficient to stimulate the phagocyte NADPH oxidase; however, it markedly enhances the NADPH oxidase response to other stimuli

28. Weiss RA (2002) HIV receptors and cellular tropism. IUBMB.Life 53:201-205
    Abstract: Viruses use specific cell surface receptors to bind to and subsequently gain entry into their host cells. Some retroviruses such as HIV-1 and HIV-2 utilize one receptor for high-affinity binding (CD4), and a separate coreceptor to mediate fusion of the viral envelope with the cell membrane (CCR5 or CXCR4). The identification of these receptors explains the cellular tropism of HIV, and hence its pathogenesis leading to immune deficiency (T-helper cell depletion), the wasting syndrome (macrophage infection), and dementia (Microglia infection). HIV can infect cells by membrane fusion at the cell surface and by receptor-mediated endocytosis. Knowledge of the HIV receptors has led to practical developments such as inhibitory drugs, reasons for genetic resistance to infection, and should inform the judicious choice of candidate vaccines

29. Williams K, Schwartz A, Corey S, Orandle M, Kennedy W, Thompson B, Alvarez X, Brown C, Gartner S, Lackner A (2002) Proliferating cellular nuclear antigen expression as a marker of perivascular macrophages in simian immunodeficiency virus encephalitis. Am.J.Pathol. 161:575-585
    Abstract: Brain perivascular macrophages are a major target of simian immunodeficiency virus (SIV) infection in rhesus macaques and HIV infection in humans. Perivascular macrophages are distinct from parenchymal Microglia in their location, morphology, expression of myeloid markers, and turnover in the CNS. In contrast to parenchymal Microglia, perivascular macrophages are continuously repopulated by blood monocytes, which undergo maturation to macrophages on entering the central nervous system (CNS). We studied differences in monocyte/macrophages in vivo that might account for preferential infection of perivascular macrophages by SIV. In situ hybridization for SIV and proliferating cellular nuclear antigen (PCNA) immunohistochemistry demonstrated that SIV-infected and PCNA-positive cells were predominantly found in perivascular cuffs of viremic animals and in histopathological lesions that characterize SIV encephalitis (SIVE) in animals with AIDS. Multilabel techniques including double-label immunohistochemistry and combined in situ hybridization and immunofluorescence confocal microscopy revealed numerous infected perivascular macrophages that were PCNA-positive. Outside the CNS, SIV-infected, PCNA-expressing macrophage subpopulations were found in the small intestine and lung of animals with AIDS. While PCNA is used as a marker of cell proliferation it is also strongly expressed in non-dividing cells undergoing DNA synthesis and repair. Therefore, more specific markers for cell proliferation including Ki-67, topoisomerase IIalpha, and bromodeoxyuridine (BrdU) incorporation were used which indicated that PCNA-positive cells within SIVE lesions were not proliferating. These observations are consistent with perivascular macrophages as terminally differentiated, non-dividing cells and underscores biological differences that could potentially define mechanisms of preferential, productive infection of perivascular macrophages in the rhesus macaque model of neuroAIDS. These studies suggest that within CNS and non-CNS tissues there exist subpopulations of macrophages that are SIV-infected and express PCNA

30. Williams KC, Hickey WF (2002) Central nervous system damage, monocytes and macrophages, and neurological disorders in AIDS. Annu.Rev.Neurosci. 25:537-562
    Abstract: This review focuses on the role of the extended macrophage/monocyte family in the central nervous system during HIV or SIV infection. The accumulated data, buttressed by recent experimental results, suggest that these cells play a central, pathogenic role in retroviral-associated CNS disease. While the immune system is able to combat the underlying retroviral infection, the accumulation and widespread activation of macrophages, Microglia, and perivascular cells in the CNS are held in check. However, with the collapse of the immune system and the disappearance of the CD4(+) T cell population, productive infection reemerges, especially in CNS macrophages. These cells, as well as noninfected macrophages, are stimulated to high levels of activation. When members of this cell group become highly activated, they elaborate a wide spectrum of deleterious substances into the neural parenchyma. In the final phases of HIV or SIV infection, this chronic, widespread, and dramatic level of macrophage/monocyte/Microglial activation constitutes a self-sustaining state of macrophage dysregulation, which results in pathological alterations and the emergence of various neurological problems

31. Albright AV, Martin J, O'Connor M, Gonzalez-Scarano F (2001) Interactions between HIV-1 gp120, chemokines, and cultured adult Microglial cells. J.Neurovirol. 7:196-207
    Abstract: HIV dementia (HIVD), a disease that is apparently mediated by neurotoxins and viral proteins secreted by HIV infected Microglia, is characterized neuropathologically by an increased number of activated Microglia in the brains of affected individuals. Consequently, the rational design of potential therapeutic strategies should take into account the mechanisms that lead to Microglial activation and to their increased prominence in the adult brain. In this regard, one leading hypothesis proposes that Microglia are recruited to specific sites in the central nervous system (CNS) as a result of interactions between Microglial chemokine receptors and chemokines, or even the viral glycoprotein gp120, which binds chemokine receptors in the process of cellular entry. Adult Microglia express the functional chemokine receptors CCR5 and CXCR4 molecules that mediate chemotaxis in these and other cell types. We determined that purified adult Microglial cultures contain a heterogeneous population with respect to their ability to respond to the alpha- and beta-chemokines, SDF1alpha, and MIP-1beta. A mean of 14.6% of the Microglia assayed responded to both alpha- and beta-chemokines (CCR5(+)CXCR4(+) phenotype); 45.4% of Microglia were phenotyped as CCR5(+)CXCR4(-); 12.9% of the Microglia were CXCR4(+)CCR5(-); and 27.0% of Microglia did not respond to either chemokine. No increase in intracellular calcium levels was seen in the vast majority of Microglia exposed to the soluble HIV envelope protein, gp120, or to HIV envelope (gp120/gp41) expressed on MLV virus pseudotypes. However, exposure of Microglia to soluble fractalkine or to other chemokines resulted in an intracellular calcium flux. Our results raise the possibility of Microglial heterogeneity with respect to their response to chemokines, and indicate that any effects due to gp120 are likely to be considerably less robust than the response of Microglia to the natural ligands of their chemokine receptors, for example SDF1alpha and MIP-1beta

32. Allen NJ, Attwell D (2001) A chemokine-glutamate connection. Nat.Neurosci. 4:676-678

33. An SF, Osuntokun O, Groves M, Scaravilli F (2001) Expression of CCR-5/CXCR-4 in spinal cord of patients with AIDS. Acta Neuropathol.(Berl) 102:175-180
    Abstract: The discovery that chemokines and their receptors (in particular CXCR-4 and CCR-5) play a role in HIV infection challenges traditional views on the pathogenesis of HIV infection in man and identifies new potential targets for therapeutic intervention. Several groups as well as our pilot study have found that increased numbers of CCR-5 positive macrophage/Microglia correlate with disease severity in brains of patients with AIDS. Among HIV-related disorders, vacuolar myelopathy (VM) is the most common spinal cord disorder in patients with AIDS. The purpose of this study was to investigate the possible relationship between the expression of CCR-5/CXCR-4 and spinal cord pathology in patients with AIDS. Thirty-four spinal cords (forming two groups: without and with VM) of patients with AIDS and 6 HIV-1-negative controls were investigated by routine histological examination and immunohistochemistry. Elevated expression of CXCR-4 was found in most AIDS cases with/without neuropathological disorders (8/17 and 13/16, respectively). No CCR-5 expression was detected in HIV-1-negative controls. Among 34 cases with AIDS, expression of CCR-5 was detected in 1/16 HIV-1-positive normal spinal cords and 5/18 with VM. Despite the lack of statistical significance between the two groups (P=0.1019), our results suggest that CCR-5/CXCR-4 are present in spinal cord of patients with AIDS and that CCR-5 is more frequently found in association with VM

34. Antinori A, Giancola ML, Alba L, Soldani F, Grisetti S (2001) Cardiomyopathy and encephalopathy in AIDS. Ann.N.Y.Acad.Sci. 946:121-129
    Abstract: HIV encephalopathy has been in the past years the most typical CNS disorder in patients with AIDS. Histologic abnormalities consist in astrocytosis, myelin pallor, infiltration by infected macrophages, resident Microglia and multinucleated giant cells, generally in absence of direct infection of neurons. Mononuclear phagocytes in the brain are the main target of HIV-1 infection and the site of productive viral replication, and viral stimulation leads to the release of neurotoxic products causing neurologic damage. Subclinical cardiac abnormalities are common in HIV+ patients and several studies suggested a role for cytokines and other inflammatory products as mediators of cardiac abnormalities. The common pathway for neurologic and cardiac manifestations supports the relationship between neurologic disease and cardiac dysfunction in HIV infection. Clinical observations suggest that cardiomyopathy could be associated with encephalopathy in HIV+ patients and that it may affect survival. Antiretroviral therapy may reduce impact of neurologic and cardiac abnormalities by suppressing plasma HIV-1 viral load

35. Asensio VC, Maier J, Milner R, Boztug K, Kincaid C, Moulard M, Phillipson C, Lindsley K, Krucker T, Fox HS, Campbell IL (2001) Interferon-independent, human immunodeficiency virus type 1 gp120-mediated induction of CXCL10/IP-10 gene expression by astrocytes in vivo and in vitro. J.Virol. 75:7067-7077
    Abstract: The CXC chemokine gamma interferon (IFN-gamma)-inducible protein CXCL10/IP-10 is markedly elevated in cerebrospinal fluid and brain of individuals infected with human immunodeficiency virus type 1 (HIV-1) and is implicated in the pathogenesis of HIV-associated dementia (HAD). To explore the possible role of CXCL10/IP-10 in HAD, we examined the expression of this and other chemokines in the central nervous system (CNS) of transgenic mice with astrocyte-targeted expression of HIV gp120 under the control of the glial fibrillary acidic protein (GFAP) promoter, a murine model for HIV-1 encephalopathy. Compared with wild-type controls, CNS expression of the CC chemokine gene CCL2/MCP-1 and the CXC chemokine genes CXCL10/IP-10 and CXCL9/Mig was induced in the GFAP-HIV gp120 mice. CXCL10/IP-10 RNA expression was increased most and overlapped the expression of the transgene-encoded HIV gp120 gene. Astrocytes and to a lesser extent Microglia were identified as the major cellular sites for CXCL10/IP-10 gene expression. There was no detectable expression of any class of IFN or their responsive genes. In astrocyte cultures, soluble recombinant HIV gp120 protein was capable of directly inducing CXCL10/IP-10 gene expression a process that was independent of STAT1. These findings highlight a novel IFN- and STAT1-independent mechanism for the regulation of CXCL10/IP-10 expression and directly link expression of HIV gp120 to the induction of CXCL10/IP-10 that is found in HIV infection of the CNS. Finally, one function of IP-10 expression may be the recruitment of leukocytes to the CNS, since the brain of GFAP-HIV gp120 mice had increased numbers of CD3(+) T cells that were found in close proximity to sites of CXCL10/IP-10 RNA expression

36. Bezzi P, Domercq M, Brambilla L, Galli R, Schols D, De Clercq E, Vescovi A, Bagetta G, Kollias G, Meldolesi J, Volterra A (2001) CXCR4-activated astrocyte glutamate release via TNFalpha: amplification by Microglia triggers neurotoxicity. Nat.Neurosci. 4:702-710
    Abstract: Astrocytes actively participate in synaptic integration by releasing transmitter (glutamate) via a calcium-regulated, exocytosis-like process. Here we show that this process follows activation of the receptor CXCR4 by the chemokine stromal cell-derived factor 1 (SDF-1). An extraordinary feature of the ensuing signaling cascade is the rapid extracellular release of tumor necrosis factor-alpha (TNFalpha). Autocrine/paracrine TNFalpha-dependent signaling leading to prostaglandin (PG) formation not only controls glutamate release and astrocyte communication, but also causes their derangement when activated Microglia cooperate to dramatically enhance release of the cytokine in response to CXCR4 stimulation. We demonstrate that altered glial communication has direct neuropathological consequences and that agents interfering with CXCR4-dependent astrocyte-Microglia signaling prevent neuronal apoptosis induced by the HIV-1 coat glycoprotein, gp120IIIB. Our results identify a new pathway for glia-glia and glia-neuron communication that is relevant to both normal brain function and neurodegenerative diseases

37. Bruce-Keller AJ, Barger SW, Moss NI, Pham JT, Keller JN, Nath A (2001) Pro-inflammatory and pro-oxidant properties of the HIV protein Tat in a Microglial cell line: attenuation by 17 beta-estradiol. J.Neurochem. 78:1315-1324
    Abstract: Microglia are activated in humans following infection with human immunodeficiency virus (HIV), and brain inflammation is thought to be involved in neuronal injury and dysfunction during HIV infection. Numerous studies indicate a role for the HIV regulatory protein Tat in HIV-related inflammatory and neurodegenerative processes, although the specific effects of Tat on Microglial activation, and the signal transduction mechanisms thereof, have not been elucidated. In the present study, we document the effects of Tat on Microglial activation and characterize the signal transduction pathways responsible for Tat's pro-inflammatory effects. Application of Tat to N9 Microglial cells increased multiple parameters of Microglial activation, including superoxide production, phagocytosis, nitric oxide release and TNF alpha release. Tat also caused activation of both p42/p44 mitogen activated protein kinase (MAPK) and NF kappa B pathways. Inhibitor studies revealed that Tat-induced NF kappa B activation was responsible for increased nitrite release, while MAPK activation mediated superoxide release, TNF alpha release, and phagocytosis. Lastly, pre-treatment of Microglial cells with physiological concentrations of 17 beta-estradiol suppressed Tat-mediated Microglial activation by interfering with Tat-induced MAPK activation. Together, these data elucidate specific components of the Microglial response to Tat and suggest that Tat could contribute to the neuropathology associated with HIV infection through Microglial promulgation of oxidative stress

38. Cambien B, Pomeranz M, Schmid-Antomarchi H, Millet MA, Breittmayer V, Rossi B, Schmid-Alliana A (2001) Signal transduction pathways involved in soluble fractalkine-induced monocytic cell adhesion. Blood 97:2031-2037
    Abstract: Fractalkine displays features that distinguishes it from the other chemokines. In particular, besides its chemoattractant action it promotes, under physiologic flow, the rapid capture and the firm adhesion of a subset of leukocytes or intervenes in the neuron/Microglia interaction. This study verified that indeed the human monocytic MonoMac6 cell line adheres to fibronectin-coated filters in response to soluble fractalkine (s-FKN). s-FKN stimulates, with distinct time courses, extracellular signal-related kinases (ERK1 and ERK2) and stress-activated protein kinases (SAPK1/JNK1 and SAPK2/p38). Both p60 Src and p72 Syk were activated under s-FKN stimulation with a rapid kinetic profile compatible with a downstream regulation on the mitogen-activated protein kinase (MAPK) congeners. The use of specific tyrosine kinase inhibitors revealed that the ERK pathway is strictly controlled by Syk, whereas c-Src up-regulated the downstream SAPK2/p38. In contrast, the SAPK1/JNK1 pathway was not regulated by any of these nonreceptor tyrosine kinases. The s-FKN-mediated increased adherence of MonoMac6 cells was partially inhibited by SB202190, a broad SAPKs inhibitor, PD98059, an MEK inhibitor, LY294002, a phosphatidyl inositol 3-kinase inhibitor, and a pertussis toxin-sensitive G protein. These data highlight that the integration of a complex array of signal transduction pathways is necessary to complete the full s-FNK-dependent adherence of human monocytic cells to fibronectin. (Blood. 2001;97:2031-2037)

39. Corasaniti MT, Maccarrone M, Nistico R, Malorni W, Rotiroti D, Bagetta G (2001) Exploitation of the HIV-1 coat glycoprotein, gp120, in neurodegenerative studies in vivo. J.Neurochem. 79:1-8
    Abstract: Neuronal loss has often been described at post-mortem in the brain neocortex of patients suffering from AIDS. Neuroinvasive strains of HIV infect macrophages, Microglial cells and multinucleated giant cells, but not neurones. Processing of the virus by cells of the myelomonocytic lineage yields viral products that, in conjunction with potentially neurotoxic molecules generated by the host, might initiate a complex network of events which lead neurones to death. In particular, the HIV-1 coat glycoprotein, gp120, has been proposed as a likely aetiologic agent of the described neuronal loss because it causes death of neurones in culture. More recently, it has been shown that brain neocortical cell death is caused in rat by intracerebroventricular injection of a recombinant gp120 coat protein, and that this occurs via apoptosis. The latter observation broadens our knowledge in the pathophysiology of the reported neuronal cell loss and opens a new lane of experimental research for the development of novel therapeutic strategies to limit damage to the brain of patients suffering from HIV-associated dementia

40. Corasaniti MT, Piccirilli S, Paoletti A, Nistico R, Stringaro A, Malorni W, Finazzi-Agro A, Bagetta G (2001) Evidence that the HIV-1 coat protein gp120 causes neuronal apoptosis in the neocortex of rat via a mechanism involving CXCR4 chemokine receptor. Neurosci.Lett. 312:67-70
    Abstract: The HIV-1 coat protein, gp120 (100 ng given intracerebroventricularly (i.c.v.) daily for seven consecutive days) causes DNA fragmentation in the brain neocortex of rat. In neocortical cells bearing ultrastructural features typical of apoptosis, electron microscopy revealed specific immunopositivity for neurofilament cytoskeletal proteins, suggesting the neuronal nature of dying cells. Neuronal apoptosis by gp120 implicates CXCR4 chemokine receptors; in fact, in rats receiving a single daily, non-neurotoxic, dose of SDF-1alpha (0.25 pmoles given i.c.v. for 7 days before gp120), the natural ligand of CXCR4 receptor, apoptosis was significantly hindered. The mechanism of SDF-1alpha protection involves inhibition of gp120-enhanced expression of IL-1beta, a cytokine implicated in the mechanisms of apoptosis induced by the viral protein in the neocortex of rat

41. Cross AK, Woodroofe MN (2001) Immunoregulation of Microglial functional properties. Microsc.Res.Tech. 54:10-17
    Abstract: Microglia are the resident tissue macrophages of the central nervous system (CNS) parenchyma and are key players in the initiation of an inflammatory response. Microglia rapidly transform from a resting to an activated morphology in response to a variety of disease states. However, they can also be the target of infections, as in the case of HIV. Many of the effector properties of Microglia can be attributed to the array of substances they secrete in response to stimuli such as bacterial lipopolysaccharide, cytokines, and chemokines. The products of activated Microglia include: cytokines (pro- and anti-inflammatory), chemokines, nitric oxide, superoxide radicals, and proteases. Furthermore, Microglia have the ability to present antigen to T cells, migrate in response to chemotactic stimuli, and phagocytose cell debris. This report focuses on the immunomodulatory functions of Microglia, with particular attention to chemokines, and highlights their pivotal role in the CNS

42. Dugas N, Lacroix C, Kilchherr E, Delfraissy JF, Tardieu M (2001) Role of CD23 in astrocytes inflammatory reaction during HIV-1 related encephalitis. Cytokine 15:96-107
    Abstract: Soluble factors released by intra-cerebral activated cells are implicated in neuronal alterations during central nervous system inflammatory diseases. In this study, the role of the CD23 pathway in astrocyte activation and its participation in human immunodeficiency virus-1 (HIV-1)-induced neuropathology were evaluated. In human primary astrocytes, CD23 protein membrane expression was dose-dependently upregulated by gp120. It was also upregulated by gamma-interferon (gamma-IFN) and modulated by interleukin-1-beta (IL-1beta) whereas Microglial cells in these stimulation conditions did not express CD23. Cell surface stimulation of CD23 expressed by astrocytes induced production of nitric oxide (NO) and IL-1beta which was inhibited by a specific inducible NO-synthase (iNOS) inhibitor (aminoguanidine), indicating the implication of this receptor in the astrocyte inflammatory reaction. On brain tissues from five out of five patients with HIV-1-related encephalitis, CD23 was expressed by astrocytes and by some Microglial cells, whereas it was not detectable on brain tissue from five of five HIV-1-infected patients without central nervous system (CNS) disease or from two of two control subjects. In addition, CD23 antigen was co-localized with iNOS and nitrotyrosine on brain tissue from patients with HIV1-related encephalitis, suggesting that CD23 participates in iNOS activation of astrocytes in vivo. In conclusion, CD23 ligation is an alternative pathway in the induction of inflammatory product synthesis by astrocytes and participates in CNS inflammation

43. Fischer-Smith T, Croul S, Sverstiuk AE, Capini C, L'Heureux D, Regulier EG, Richardson MW, Amini S, Morgello S, Khalili K, Rappaport J (2001) CNS invasion by CD14+/CD16+ peripheral blood-derived monocytes in HIV dementia: perivascular accumulation and reservoir of HIV infection. J.Neurovirol. 7:528-541
    Abstract: Increases in circulating CD14+/CD16+ monocytes have been associated with HIV dementia; trafficking of these cells into the CNS has been proposed to play an important role in the pathogenesis of HIV-induced neurological disorders. This model suggests that events outside the CNS leading to monocyte activation initiate the process leading to HIV dementia. To investigate the role of this activated monocyte subset in the pathogenesis of HIV dementia, we examined brain specimens from patients with HIV encephalopathy (HIVE), HIV without encephalopathy, and seronegative controls. An accumulation of perivascular macrophages was observed in HIVE. The majority of these cells identified in Microglial nodules and in the perivascular infiltrate were CD14+/CD16+. P24 antigen colocalized with both CD14 and CD16 suggesting that the CD14+/CD16+ macrophage is a major reservoir of HIV-1 infection in CNS. Using CD45/LCA staining, the perivascular macrophage was distinguished from resident Microglia. In addition to perivascular and nodular localizations, CD16 also stained ramified cells throughout the white matter. These cells were more ramified and abundant than cells positive for CD14 in white matter. Double staining for p24 and CD16 suggests that these cells were often infected with HIV-1. The prominent distribution of CD14+ cells in HIVE prompted our analysis of soluble CD14 levels in cerebrospinal fluid. Higher levels of soluble CD14 (sCD14) were observed in patients with moderate-to-severe HIV dementia, suggesting the utility of sCD14 as a surrogate marker. CD14+/CD16+ monocytes may play a role in other neurological disorders and sCD14 may be useful for evaluating these conditions

44. Giralt M, Carrasco J, Penkowa M, Morcillo MA, Santamaria J, Campbell IL, Hidalgo J (2001) Astrocyte-targeted expression of interleukin-3 and interferon-alpha causes region-specific changes in metallothionein expression in the brain. Exp.Neurol. 168:334-346
    Abstract: Transgenic mice expressing IL-3 and IFN-alpha under the regulatory control of the GFAP gene promoter (GFAP-IL3 and GFAP-IFNalpha mice) exhibit a cytokine-specific, late-onset chronic-progressive neurological disorder which resemble many of the features of human diseases such as multiple sclerosis, Aicardi-Goutieres syndrome, and some viral encephalopathies including HIV leukoencephalopathy. In this report we show that the metallothionein-I+II (MT-I+II) isoforms were upregulated in the brain of both GFAP-IL3 and GFAP-IFNalpha mice in accordance with the site and amount of expression of the cytokines. In the GFAP-IL3 mice, in situ hybridization analysis for MT-I RNA and radioimmunoassay results for MT-I+II protein revealed that a significant upregulation was observed in the cerebellum and medulla plus pons at the two ages studied, 1-3 and 6-10 months. Increased MT-I RNA levels occurred in the Purkinje and granular layers of the cerebellum, as well as in its white matter tracts. In contrast to the cerebellum and brain stem, MT-I+II were downregulated by IL-3 in the hippocampus and the remaining brain in the older mice. In situ hybridization for MT-III RNA revealed a modest increase in the cerebellum, which was confirmed by immunohistochemistry. MT-III immunoreactivity was present in cells that were mainly round or amoeboid monocytes/macrophages and in astrocytes. MT-I+II induction was more generalized in the GFAP-IFNalpha (GIFN12 and GIFN39 lines) mice, with significant increases in the cerebellum, thalamus, hippocampus, and cortex. In the high expressor line GIFN39, MT-III RNA levels were significantly increased in the cerebellum (Purkinje, granular, and molecular layers), thalamus, and hippocampus (CA2/CA3 and especially lacunosum molecular layers). Reactive astrocytes, activated rod-like Microglia, and macrophages, but not the perivenular infiltrating cells, were identified as the cellular sources of the MT-I+II and MT-III proteins. The pattern of expression of the different MT isoforms in these transgenic mice differed substantially, demonstrating unique effects associated with the expression of each cytokine. The results indicate that the MT expression in the CNS is significantly affected by the cytokine-induced inflammatory response and support a major role of these proteins during CNS injury

45. Gorry PR, Bristol G, Zack JA, Ritola K, Swanstrom R, Birch CJ, Bell JE, Bannert N, Crawford K, Wang H, Schols D, De Clercq E, Kunstman K, Wolinsky SM, Gabuzda D (2001) Macrophage tropism of human immunodeficiency virus type 1 isolates from brain and lymphoid tissues predicts neurotropism independent of coreceptor specificity. J.Virol. 75:10073-10089
    Abstract: The viral determinants that underlie human immunodeficiency virus type 1 (HIV-1) neurotropism are unknown, due in part to limited studies on viruses isolated from brain. Previous studies suggest that brain-derived viruses are macrophage tropic (M-tropic) and principally use CCR5 for virus entry. To better understand HIV-1 neurotropism, we isolated primary viruses from autopsy brain, cerebral spinal fluid, blood, spleen, and lymph node samples from AIDS patients with dementia and HIV-1 encephalitis. Isolates were characterized to determine coreceptor usage and replication capacity in peripheral blood mononuclear cells (PBMC), monocyte-derived macrophages (MDM), and Microglia. Env V1/V2 and V3 heteroduplex tracking assay and sequence analyses were performed to characterize distinct variants in viral quasispecies. Viruses isolated from brain, which consisted of variants that were distinct from those in lymphoid tissues, used CCR5 (R5), CXCR4 (X4), or both coreceptors (R5X4). Minor usage of CCR2b, CCR3, CCR8, and Apj was also observed. Primary brain and lymphoid isolates that replicated to high levels in MDM showed a similar capacity to replicate in Microglia. Six of 11 R5 isolates that replicated efficiently in PBMC could not replicate in MDM or Microglia due to a block in virus entry. CD4 overexpression in Microglia transduced with retroviral vectors had no effect on the restricted replication of these virus strains. Furthermore, infection of transfected cells expressing different amounts of CD4 or CCR5 with M-tropic and non-M-tropic R5 isolates revealed a similar dependence on CD4 and CCR5 levels for entry, suggesting that the entry block was not due to low levels of either receptor. Studies using TAK-779 and AMD3100 showed that two highly M-tropic isolates entered Microglia primarily via CXCR4. These results suggest that HIV-1 tropism for macrophages and Microglia is restricted at the entry level by a mechanism independent of coreceptor specificity. These findings provide evidence that M-tropism rather than CCR5 usage predicts HIV-1 neurotropism

46. Gray F, Adle-Biassette H, Chretien F, Lorin dlG, Force G, Keohane C (2001) Neuropathology and neurodegeneration in human immunodeficiency virus infection. Pathogenesis of HIV-induced lesions of the brain, correlations with HIV-associated disorders and modifications according to treatments. Clin.Neuropathol. 20:146-155
    Abstract: A variety of HIV-induced lesions of the central nervous system (CNS) have been described, including HIV encephalitis, HIV leukoencephalopathy, axonal damage, and diffuse poliodystrophy with neuronal loss of variable severity resulting, at least partly, from an apoptotic process. However, no correlation could be established between these changes and HIV dementia (HIVD). From our study of HIV infected patients, it appeared that neuronal apoptosis is probably not related to a single cause. Microglial and glial activation, directly or indirectly related to HIV infection, plays a major role in neuronal apoptosis possibly through the mediation of oxidative stress. In our patients with full-blown AIDS, this mechanism predominated in the basal ganglia and correlated well with HIVD. Axonal damage, either secondary to Microglial activation, or to systemic factors also contributes to neuronal apoptosis. Although massive neuronal loss may be responsible for HIVD in occasional cases, we conclude that neuronal apoptosis is a late event and does not represent the main pathological substrate of HIVD. The dementia more likely reflects a specific neuronal dysfunction resulting from the combined effects of several mechanisms, some of which may be reversible. Introduction of highly active antiretroviral therapy dramatically improved patient survival, however, its impact on the incidence and course of HIVD remains debatable. In our series, the incidence of HIVE has dramatically decreased since the introduction of multitherapies, but a number of cases remain whose cognitive disorders persist, despite HAART. The poor CNS penetration of many antiretroviral agents is a possible explanation, but irreversible "burnt out" HIV-induced CNS changes may also be responsible

47. Herzberg U, Sagen J (2001) Peripheral nerve exposure to HIV viral envelope protein gp120 induces neuropathic pain and spinal gliosis. J.Neuroimmunol. 116:29-39
    Abstract: Painful sensory neuropathy is a common and debilitating consequence of human immunodeficiency virus (HIV). The underlying causes of neuropathic pain are most likely not due to direct infection of the nervous system by active virus. The goal of this study was to determine whether epineural exposure to the HIV-1 envelope protein gp120 could lead to chronic painful peripheral neuropathy. Two doses of gp120 or BSA control were transiently delivered epineurally via oxidized cellulose wrapped around the rat sciatic nerve. Animals were assessed for neuropathic pain behaviors at several intervals from 1-30 days following nerve surgery. Allodynia and hyperalgesia were observed within 1-3 days following gp120 and sustained throughout the testing period. The gp120-exposed sciatic nerve exhibited early but transient pathology, notably axonal swelling and increased tumor necrosis factor alpha (TNF-alpha) within the nerve trunk. In contrast, intense astrocytic and Microglial activation was observed in the spinal cord, and this gliosis persisted for at least 30 days following epineural gp120, in parallel with neuropathic pain behaviors. These findings demonstrate that limited peripheral nerve exposure to HIV protein can induce persistent painful sensory neuropathy that may be sustained and magnified by long-term spinal neuropathology

48. Heyes MP, Ellis RJ, Ryan L, Childers ME, Grant I, Wolfson T, Archibald S, Jernigan TL (2001) Elevated cerebrospinal fluid quinolinic acid levels are associated with region-specific cerebral volume loss in HIV infection. Brain 124:1033-1042
    Abstract: Neuronal injury, dendritic loss and brain atrophy are frequent complications of infection with human immunodeficiency virus (HIV) type 1. Activated brain macrophages and Microglia can release quinolinic acid, a neurotoxin and NMDA (N-methyl-D-aspartate) receptor agonist, which we hypothesize contributes to neuronal injury and cerebral volume loss. In the present cross-sectional study of 94 HIV-1-infected patients, elevated CSF quinolinic acid concentrations correlated with worsening brain atrophy, quantified by MRI, in regions vulnerable to excitotoxic injury (the striatum and limbic cortex) but not in regions relatively resistant to excitotoxicity (the non-limbic cortex, thalamus and white matter). Increased CSF quinolinic acid concentrations also correlated with higher CSF HIV-1 RNA levels. In support of the specificity of these associations, blood levels of quinolinic acid were unrelated to striatal and limbic volumes, and CSF levels of beta(2)-microglobulin, a non-specific and non-excitotoxic marker of immune activation, were unrelated to regional brain volume loss. These results are consistent with the hypothesis that quinolinic acid accumulation in brain tissue contributes to atrophy in vulnerable brain regions in HIV infection and that virus replication is a significant driver of local quinolinic acid biosynthesis

49. Kaul M, Garden GA, Lipton SA (2001) Pathways to neuronal injury and apoptosis in HIV-associated dementia. Nature 410:988-994
    Abstract: Human immunodeficiency virus-1 (HIV-1) can induce dementia with alarming occurrence worldwide. The mechanism remains poorly understood, but discovery in brain of HIV-1-binding sites (chemokine receptors) provides new insights. HIV-1 infects macrophages and Microglia, but not neurons, although neurons are injured and die by apoptosis. The predominant pathway to neuronal injury is indirect through release of macrophage, Microglial and astrocyte toxins, although direct injury by viral proteins might also contribute. These toxins overstimulate neurons, resulting in the formation of free radicals and excitotoxicity, similar to other neurodegenerative diseases. Recent advances in understanding the signalling pathways mediating these events offer hope for therapeutic intervention

50. Langford D, Masliah E (2001) Crosstalk between components of the blood brain barrier and cells of the CNS in Microglial activation in AIDS. Brain Pathol. 11:306-312
    Abstract: During the progression of AIDS, a majority of patients develop cognitive disorders such as HIV encephalitis (HIVE) and AIDS dementia complex (ADC), which correlate closely with macrophage infiltration into the brain and Microglial activation. Microglial activation occurs in response to infection, inflammation and neurological disorders including HIVE, Alzheimer's disease, Parkinson's disease and multiple sclerosis. Microglia can be activated by immunoreactive cells independent of, but enhanced by HIV infection, from at least two routes. Activation may occur from signals originating from activated monocytes and lymphocytes in the blood stream, which initiate a cascade of stimuli that ultimately reach Microglia in the brain or from activated macrophages/Microglia/astrocytes within the brain. Effects of Microglial activation stemming from both systemic and CNS HIV infection act together to commence signaling feedback, leading to HIVE and increased neurodegeneration. Most recent data indicate that in AIDS patients, Microglial activation in the brain with subsequent release of excitotoxins, cytokines and chemokines leads to neurodegeneration and cognitive impairment. Since the presence of HIV in the brain results from migration of infected monocytes and lymphocytes across the vascular boundary, the development of novel therapies aimed at protecting the integrity of the blood brain barrier (BBB) upon systemic HIV infection is critical for controlling CNS infection

51. Levin MC, Rosenblum MK, Fox CH, Jacobson S (2001) Localization of retrovirus in the central nervous system of a patient co-infected with HTLV-1 and HIV with HAM/TSP and HIV-associated dementia. J.Neurovirol. 7:61-65
    Abstract: Persons co-infected with HTLV-1 and HIV are at increased risk for neurologic disease. These patients may develop HAM/TSP and/or HIV-associated dementia. In this study, we localized cells infected with retrovirus in the central nervous system (CNS) of a patient with both HAM/TSP and HIV-associated dementia. HTLV-1 was localized to astrocytes and HIV to macrophage/Microglia. There was no co-infection of a single cell phenotype in this patient. These data suggest that mechanisms other than co-infection of the same CNS cell may play a role in the development of neurologic disease in patients dual infected with HTLV-1 and HIV

52. Martin J, LaBranche CC, Gonzalez-Scarano F (2001) Differential CD4/CCR5 utilization, gp120 conformation, and neutralization sensitivity between envelopes from a Microglia-adapted human immunodeficiency virus type 1 and its parental isolate. J.Virol. 75:3568-3580
    Abstract: Human immunodeficiency virus type 1 (HIV-1) infects and induces syncytium formation in Microglial cells from the central nervous system (CNS). A primary isolate (HIV-1(BORI)) was sequentially passaged in cultured Microglia, and the isolate recovered (HIV-1(BORI-15)) showed high levels of fusion and replicated more efficiently in Microglia (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. Gonzalez-Scarano, J. Virol. 70:7654-7662, 1996). The parent and adapted viruses used CCR5 as coreceptor. Recombinant viruses demonstrated that the syncytium-inducing phenotype was associated with four amino acid differences in the V1/V2 region of the viral gp120 (J. T. C. Shieh, J. Martin, G. Baltuch, M. H. Malim, and F. Gonzalez-Scarano, J. Virol. 74:693-701, 2000). We produced luciferase-reporter, env-pseudotyped viruses using plasmids containing env sequences from HIV-1(BORI), HIV-1(BORI-15), and the V1/V2 region of HIV-1(BORI-15) in the context of HIV-1(BORI) env (named rBORI, rB15, and rV1V2, respectively). The pseudotypes were used to infect cells expressing various amounts of CD4 and CCR5 on the surface. In contrast to the parent recombinant, the rB15 and rV1V2 pseudotypes retained their infectability in cells expressing low levels of CD4 independent of the levels of CCR5, and they infected cells expressing CD4 with a chimeric coreceptor containing the third extracellular loop of CCR2b in the context of CCR5 or a CCR5 Delta4 amino-terminal deletion mutant. The VH-rB15 and VH-rV1V2 recombinant viruses were more sensitive to neutralization by a panel of HIV-positive sera than was VH-rBORI. Interestingly, the CD4-induced 17b epitope on gp120 was more accessible in the rB15 and rV1V2 pseudotypes than in rBORI, even before CD4 binding, and concomitantly, the rB15 and rV1V2 pseudotypes were more sensitive to neutralization with the human 17b monoclonal antibody. Adaptation to growth in Microglia--cells that have reduced expression of CD4 in comparison with other cell types--appears to be associated with changes in gp120 that modify its ability to utilize CD4 and CCR5. Changes in the availability of the 17b epitope indicate that these affect conformation. These results imply that the process of adaptation to certain tissue types such as the CNS directly affects the interaction of HIV-1 envelope glycoproteins with cell surface components and with humoral immune responses

53. Milligan ED, O'Connor KA, Nguyen KT, Armstrong CB, Twining C, Gaykema RP, Holguin A, Martin D, Maier SF, Watkins LR (2001) Intrathecal HIV-1 envelope glycoprotein gp120 induces enhanced pain states mediated by spinal cord proinflammatory cytokines. J.Neurosci. 21:2808-2819
    Abstract: Perispinal (intrathecal) injection of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein gp120 creates exaggerated pain states. Decreases in response thresholds to both heat stimuli (thermal hyperalgesia) and light tactile stimuli (mechanical allodynia) are rapidly induced after gp120 administration. gp120 is the portion of HIV-1 that binds to and activates Microglia and astrocytes. These glial cells have been proposed to be key mediators of gp120-induced hyperalgesia and allodynia because these pain changes are blocked by drugs thought to affect glial function preferentially. The aim of the present series of studies was to determine whether gp120-induced pain changes involve proinflammatory cytokines [interleukin-1beta (IL-1) and tumor necrosis factor-alpha (TNF-alpha)], substances released from activated glia. IL-1 and TNF antagonists each prevented gp120-induced pain changes. Intrathecal gp120 produced time-dependent, site-specific increases in TNF and IL-1 protein release into lumbosacral CSF; parallel cytokine increases in lumbar dorsal spinal cord were also observed. Intrathecal administration of fluorocitrate (a glial metabolic inhibitor), TNF antagonist, and IL-1 antagonist each blocked gp120-induced increases in spinal IL-1 protein. These results support the concept that activated glia in dorsal spinal cord can create exaggerated pain states via the release of proinflammatory cytokines

54. Mitchell W (2001) Neurological and developmental effects of HIV and AIDS in children and adolescents. Ment.Retard.Dev.Disabil.Res.Rev. 7:211-216
    Abstract: HIV-related encephalopathy is an important problem in vertically infected children with HIV. Infected infants may manifest early, catastrophic encephalopathy, with loss of brain growth, motor abnormalities, and cognitive dysfunction. Even without evidence of AIDS, infected infants score lower than serorevertors on developmental measures, particularly language acquisition. Children with perinatal or later transfusion-related infection generally are roughly comparable developmentally to their peers until late in their course. Symptoms similar to adult AIDS dementia complex are occasionally seen in adolescents with advanced AIDS, including dementia, bradykinesia, and spasticity. Opportunistic CNS infections such as toxoplasmosis and progressive multifocal leukoencephalopathy are less common in children and adolescents than in adults. Increasing evidence suggests that aggressive antiretroviral treatment may halt or even reverse encephalopathy. Neuroimaging changes may precede or follow clinical manifestations, and include early lenticulostriate vessel echogenicity on cranial ultrasound, calcifying microangiopathy on CT scan, and/or white matter lesions and central atrophy on MRI. Differential diagnosis of neurological dysfunction in an HIV-infected infant includes the effects of maternal substance abuse, other CNS congenital infections, and other causes of early static encephalopathy. Initial entry of HIV into the nervous system occurs very early in infection. The risk of clinical HIV encephalopathy increases with very early age of infection and with high viral loads. Virus is found in Microglia and brain derived macrophages, not neurons. The neuronal effect of HIV is probably indirect, with various cytokines implicated. Apoptosis is the presumed mechanism of damage to neurons by HIV

55. Mrak RE, Griffinbc WS (2001) The role of activated astrocytes and of the neurotrophic cytokine S100B in the pathogenesis of Alzheimer's disease. Neurobiol.Aging 22:915-922
    Abstract: Activated astrocytes, overexpressing the neurotrophic signaling molecule S100beta, are invariant components of the Abeta plaques of Alzheimer's disease. Even early, nonfibrillar amyloid deposits in Alzheimer's disease contain such astrocytes, and the numbers and degree of activation of these wax and wane with the subsequent neuritic pathology of plaque evolution. Astrocytic overexpression of S100B in the neuritic plaques of Alzheimer's disease correlates with the degree of neuritic pathology in Abeta plaques in this disease, suggesting a pathogenic role for S100B's neurotrophic properties in the evolution of these lesions. Astrocytic overexpression of S100B, in turn, is promoted by high levels of interleukin-1 (IL-1), originating from activated Microglia that are also constant components of Abeta plaques in Alzheimer's disease. Similar patterns of astrocyte activation, S100B overexpression, Microglial activation, and IL-1 overexpression are seen in conditions that confer risk for Alzheimer's disease (aging, head trauma, Down's syndrome), in conditions that predispose to accelerated appearance of Alzheimer-like neuropathologic changes (chronic epilepsy, HIV infection), and in animal models of Alzheimer's disease. These cells and molecules are an important components of a cytokine cycle of molecular and cellular cascades that may drive disease progression in Alzheimer's disease

56. Nebuloni M, Pellegrinelli A, Ferri A, Bonetto S, Boldorini R, Vago L, Grassi MP, Costanzi G (2001) Beta amyloid precursor protein and patterns of HIV p24 immunohistochemistry in different brain areas of AIDS patients. AIDS 15:571-575
    Abstract: OBJECTIVES: To evaluate the correlation between immunohistochemical positive patterns (globular and filamentous structures) of beta-amyloid precursor protein (beta-APP), used as a marker of axonal damage, and the different distribution of HIV p24 antigens, in three different brain areas of AIDS patients. METHODS: Eighteen AIDS patients with HIV-related brain lesions were included in the study. Forty-nine sections from basal ganglia, frontal cortex and hippocampus were selected. After microwave oven pre-treatment, the sections were incubated with anti-HIV p24 and anti-beta-APP monoclonal antibodies; the reactions were developed with peroxidase/3,3'diaminobenzidine. The positivity was graded by semi-quantitative scores. Double immunohistochemical staining was used to evaluate the co-localization of the antigens. RESULTS: HIV p24 immunohistochemistry was positive in 44 of 49 sections (89%), with a prevalence of interstitial positive cells and positive Microglial nodules in 27 and 13 sections respectively. beta-APP-positive structures were demonstrated in 23 of 44 sections (52%) with HIV-related lesions, and were absent from the five sections without viral expression. Globular and filamentous lesions were observed in 21 of 23 sections and 10 of 23 lesions respectively. Moreover, a high grade of globular type lesion was related to an elevated presence of diffuse interstitial HIV p24-positive cells in basal ganglia; double immunohistochemical reactions demonstrated the co-localization of beta-APP globules and HIV p24 antigens. CONCLUSIONS: The data obtained confirm the coexpression of beta-APP and viral antigens in particular areas of the brain with HIV-related lesions; there is a strict correlation between beta-APP globules (indicating chronic cerebral damage) and the interstitial pattern of HIV p24 immunohistochemistry

57. Orenstein JM (2001) The macrophage in HIV infection. Immunobiology 204:598-602
    Abstract: Macrophages play a key role in several critical aspects of HIV disease. They appear to be the first cells infected by HIV and perhaps the very source of HIV production when CD4+ cells are markedly depleted in the patient. Macrophages and Microglial cells are the cells infected by HIV in the CNS. In tonsils and adenoids of HIV-infected patients, macrophages fuse into multinucleated giant cells that produce copious amounts of virus. Finally, opportunistic pathogens can cause an upregulation of HIV production by macrophages, often in the multinucleated form

58. Patrizio M, Colucci M, Levi G (2001) Human immunodeficiency virus type 1 Tat protein decreases cyclic AMP synthesis in rat Microglia cultures. J.Neurochem. 77:399-407
    Abstract: We have studied the modulation of cyclic AMP (cAMP) accumulation by the human immunodeficiency virus type 1 (HIV 1) protein Tat in Microglia and astrocyte cultures obtained from neonatal rat brain. Pretreatment of Microglia with recombinant Tat resulted in a dose- and time-dependent decrease of cAMP accumulation induced by subsequent exposure to isoproterenol (1 microM). The inhibitory action of 100 ng/mL Tat approached 50% after 4 h of preincubation and reached a maximum of 70% after 24 h. The Tat-induced time- and dose-dependent decrease of cAMP accumulation was observed also when Microglial cultures were stimulated with the adenylyl cyclase activator forskolin (100 microM). In both cases, Tat inhibitory action was 70% reverted by a specific monoclonal anti-Tat antibody, but was not prevented either by the phosphodiesterase inhibitor 3-isobutyl-1-methyl-xantine (100 microM) or by a 16-h pretreatment of Microglial cultures with the Gi protein inhibitor pertussis toxin (10 ng/mL). All these results suggested that the viral protein acts at a step of the cAMP transduction pathway other than receptors, G proteins and phosphodiesterases. The target of Tat appeared to be adenylyl cyclase, whose activity was markedly reduced (up to 60%) in membranes prepared from Tat-treated Microglial cells, both in basal conditions and after stimulation with isoproterenol and forskolin. The inability of the competitive inhibitor of nitric oxide synthase N(G)-monometyl- L-arginine (20 and 200 microM) to revert Tat action on forskolin-induced cAMP accumulation, and of two potent nitric oxide donors, PAPA and DETA (0.1-2 m M), to alter forskolin-induced cAMP accumulation, excluded an involvement of nitric oxide in Tat-induced adenylyl cyclase inhibition. On the contrary, two inhibitors of nuclear factor kappaB activation, N-tosyl-( L)-phenylalanine chloromethyl ketone (10 microM) and SN50 (25 microM), markedly prevented the reduction of forskolin-evoked cAMP accumulation by Tat, suggesting a possible role for this nuclear transcriptional factor in the regulation of adenylyl cyclase by Tat in Microglia. This assumption was strengthened by the ability of lipopolysaccharide (100 ng/mL, 4 h) to mimic the inhibitory effect of the viral protein. Conversely, astrocyte cAMP accumulation was unaffected by the viral protein, as tested at various concentrations and time points. Finally, Tat inhibition of Microglial adenylyl cyclase was not due to non-specific cytotoxicity. As cAMP has been reported to exert a neuroprotective role in several in vivo and in vitro models of brain pathologies, and Microglia is believed to mediate Tat-induced neurotoxicity, these results suggest that the ability of Tat to inhibit cAMP synthesis in Microglia may contribute to neuronal degeneration and cell death associated with HIV infection

59. Peterson KE, Robertson SJ, Portis JL, Chesebro B (2001) Differences in cytokine and chemokine responses during neurological disease induced by polytropic murine retroviruses Map to separate regions of the viral envelope gene. J.Virol. 75:2848-2856
    Abstract: Infection of the central nervous system (CNS) by several viruses can lead to upregulation of proinflammatory cytokines and chemokines. In immunocompetent adults, these molecules induce prominent inflammatory infiltrates. However, with immunosuppressive retroviruses, such as human immunodeficiency virus (HIV), little CNS inflammation is observed yet proinflammatory cytokines and chemokines are still upregulated in some patients and may mediate pathogenesis. The present study examined expression of cytokines and chemokines in brain tissue of neonatal mice infected with virulent (Fr98) and avirulent (Fr54) polytropic murine retroviruses. While both viruses infect Microglia and endothelia primarily in the white matter areas of the CNS, only Fr98 induces clinical CNS disease. The pathology consists of gliosis with minimal morphological changes and no inflammation, similar to HIV. In the present experiments, mice infected with Fr98 had increased cerebellar mRNA levels of proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), TNF-beta, and interleukin-1 alpha and chemokines macrophage inflammatory protein-1 alpha (MIP-1 alpha), MIP-1 beta, monocyte chemoattractant protein 1 (MCP-1), gamma-interferon-inducible protein 10 (IP-10), and RANTES compared to mice infected with Fr54 or mock-infected controls. The increased expression of these genes occurred prior to the development of clinical symptoms, suggesting that these cytokines and chemokines might be involved in induction of neuropathogenesis. Two separate regions of the Fr98 envelope gene are associated with neurovirulence. CNS disease associated with the N-terminal portion of the Fr98 env gene was preceded by upregulation of cytokines and chemokines. In contrast, disease associated with the central region of the Fr98 env gene showed no upregulation of cytokines or chemokines and thus did not require increased expression of these genes for disease induction

60. Petito CK, Roberts B, Cantando JD, Rabinstein A, Duncan R (2001) Hippocampal injury and alterations in neuronal chemokine co-receptor expression in patients with AIDS. J.Neuropathol.Exp.Neurol. 60:377-385
    Abstract: Hippocampal neurons express high levels of HIV chemokine co-receptors, activation of which causes injury or death in vitro. To determine if their in vivo expression correlates with injury, we evaluated neuronal CXCR4 and CCR5 immunoreactivity and reactive gliosis in autopsy hippocampus of 10 control cases, 11 AIDS cases without HIV encephalitis (HIVnE) or opportunistic infections/lymphomas (OI/L), and 11 AIDS cases with HIV encephalitis (HIVE). All groups had higher CXCR4 and CCR5 expression in CA3 and CA4 neurons than CA1 neurons (p < 0.05). HIVE cases had increased neuronal CXCR4 and decreased neuronal CCR5 expression as well as increased numbers of hippocampal GFAP-positive astrocytes and LN3-positive Microglia. Changes were most severe in CA3 and CA4 and lowest in CA1 regions. These findings also were noted in the 4 HIVE cases with neither hippocampal HIVE nor brain OI/L and in the HIVnE groups. This study quantitates the regional distribution of hippocampal neuronal CXCR4 and CCR5 and shows their respective increase and decrease in AIDS. It suggests a relationship between neuronal loss and gliosis with intensity of neuronal chemokine expression and raises the possibility of a selective vulnerability of hippocampal neurons to AIDS-related injury

61. Power C, Johnson RT (2001) Neuroimmune and neurovirological aspects of human immunodeficiency virus infection. Adv.Virus Res. 56:389-433
    Abstract: Like most lentiviruses, HIV-1 causes both immune suppression and neurological disease. Neurological disease may occur at any stage of HIV infection but is most apparent with severe immune suppression. Cognitive impairment, reflected strikingly by HIV-associated dementia, has attracted intense interest since the outset of the HIV epidemic, and understanding of its pathogenesis has been spurred on by the emergence of several hypotheses outlining potential pathogenic mechanisms. The release of inflammatory molecules by HIV-infected Microglia and macrophages and the concurrent neuronal damage play central roles in the conceptualization of HIV neuropathogenesis. Many inflammatory molecules appear to contribute to the pathogenic cascade and their individual roles remain undefined. At the same time, the abundance of virus in the brain and the type or strain of virus found in the brain may also be important codeterminants of neurological disease, as shown for other neurotropic viruses. Coreceptor use by HIV found in the brain appears to closely mirror what has been reported in systemic macrophages. The impact of HAART on viral genotype and phenotype found in the brain, and its relationship to clinical disease, remain uncertain. Several interesting animal models have been developed, using other lentiviruses, transgenic animals, and HIV-infected SCID mice, that may prove useful in future pathogenesis and therapeutic studies. Despite the progress in the understanding of HIV neuropathogenesis, many questions remain unanswered

62. Pulliam L, Irwin I, Kusdra L, Rempel H, Flitter WD, Garland WA (2001) CPI-1189 attenuates effects of suspected neurotoxins associated with AIDS dementia: a possible role for ERK activation. Brain Res. 893:95-103
    Abstract: Individuals infected with the human immunodeficiency virus (HIV) often experience a dementia characterized by mental slowing and memory loss. Motor dysfunction may also accompany this condition. The pathogenesis of the dementia is not known, but microscopic examination of brain tissue from those afflicted shows evidence of chronic inflammation, reactive gliosis and cell death. Neurotoxic factors produced from activated macrophage or Microglial cells such as tumor necrosis factor-alpha (TNFalpha), gp120 and quinolinic acid have been implicated as agents for the cell death which often appears to occur by an apoptotic mechanism. CPI-1189, a drug currently undergoing clinical evaluation as a treatment for the dementia associated with AIDS, is shown in this paper to mitigate apoptosis induced by TNFalpha, gp120, and necrosis induced by quinolinic acid. In addition, CPI-1189 mitigates the cell death produced by supernatants from cultured macrophages obtained from patients with AIDS dementia. The exact mechanism by which CPI-1189 prevents neurotoxicity is not known; however, protection from TNFalpha and supernatant-induced toxicity does not appear to involve NFkappaB translocation, and appears to be associated with an increase in activated ERK-MAP kinase. These findings may have implications for other neurological diseases where apoptotic cell death contributes to neurodegeneration

63. Ruff MR, Melendez-Guerrero LM, Yang QE, Ho WZ, Mikovits JW, Pert CB, Ruscetti FA (2001) Peptide T inhibits HIV-1 infection mediated by the chemokine receptor-5 (CCR5). Antiviral Res. 52:63-75
    Abstract: Peptide T, which is derived from the V2 region of HIV-1, inhibits replication of R5 and dual-tropic (R5/X4) HIV-1 strains in monocyte-derived macrophages (MDMs), Microglia, and primary CD4(+)T cells. Little to no inhibition by peptide T was observed with lab adapted X4 viruses such as IIIB, MN, or NL4-3 propagated in CD4(+) T cells or in the MAGI entry assay. The more clinically relevant R5/X4 early passage patient isolates were inhibited via either the X4 or R5 chemokine receptors, although inhibition was greater with R5 compared to X4 receptors. Virus inhibition ranged from 60 to 99%, depending on the assay, receptor target, viral isolate and amount of added virus. Peak inhibitory effects were detected at concentrations from 10(-12) to 10(-9) M. Peptide T acted to block viral entry as it inhibited in the MAGI cell assay and blocked infection in the luciferase reporter assay using HIV virions pseudotyped with ADA envelope. These results using early passage virus grown in primary cells, together with two different entry reporter assays, show that peptide T selectively inhibits HIV replication using chemokine receptor CCR5 compared to CXC4, explaining past inconsistencies of in vitro antiviral effects

64. Wang TH, Donaldson YK, Brettle RP, Bell JE, Simmonds P (2001) Identification of shared populations of human immunodeficiency virus type 1 infecting Microglia and tissue macrophages outside the central nervous system. J.Virol. 75:11686-11699
    Abstract: Infection of Microglia and other cells of the macrophage/monocyte lineage in the central nervous system (CNS) by human immunodeficiency virus type I (HIV-1) underlies the development of giant cell encephalitis (GCE). It is currently unknown whether GCE depends on the emergence of virus populations specifically adapted to replicate in cells of the monocyte/macrophage lineage and whether this also leads to the specific targeting of macrophages in other nonlymphoid tissues. Autopsy samples from lymph node, brain (frontal region), lung, and full-thickness colon sections were obtained from nine study subjects with GCE and from nine without. The two groups showed no significant differences in CD4 counts, disease progression, or treatment history before death. Genetic relatedness between variants recovered from lymph node and nonlymphoid tissues was assessed by sequence comparison of V3 and p17(gag) regions using a newly developed method that scores the sample composition at successive nodes in a neighbor-joining tree. The association index enabled objective, numerical comparisons on the degree of tissue compartmentalization to be made. High proviral loads and p24 antigen expression in the brain were confined to the nine individuals with GCE. GCE was also associated with significantly higher proviral loads in colon samples (median of the GCE(+) group: 1,010 copies/10(6) cells; median of GCE(-) group, 10/10(6) cells; P = 0.006). In contrast, there were no significant differences in proviral load between the GCE(+) and GCE(-) groups in lymph node or lung samples, where HIV infection was manifested predominantly by infiltrates of lymphoid cells. V3 sequences from brain samples of individuals with GCE showed the greatest compartmentalization from those of lymph node, although samples from other tissues, particularly the colon, frequently contained variants phylogenetically related to those found in brain. The existence of shared, distinct populations of HIV specifically distributed in cells of the monocyte/macrophage lineage was further indicated by immunocytochemical detection of CD68(+), multinucleated giant cells expressing p24 antigen in samples of lung and colon in two individuals with GCE. This study provides the basis for future investigation of possible phenotypic similarities that underline the shared distributions of HIV variants infecting Microglia and tissue macrophages outside the CNS

65. Wesselingh SL, Thompson KA (2001) Immunopathogenesis of HIV-associated dementia. Curr.Opin.Neurol. 14:375-379
    Abstract: This review provides a subjective analysis of the advances in our understanding of the immunopathogenesis of HIV-associated dementia that have occurred over the past 12 months. The review will focus on the following areas: (i) the role of chemokines and cytokines; (ii) the role of astrocytes, astrocyte cell death and non-productive infection of astrocytes; (iii) a model of the neuropathogenesis of HIV-associated dementia and its impact on treatment paradigms and future research. The requirements for the development of HIV-associated dementia are immunosuppression, the loss of macrophage regulation, central nervous system HIV infection of Microglia and macrophages with a neurovirulent HIV strain, restricted HIV infection of astrocytes, and astrocyte cell death, all of which lead to an intracellular milieu that is neurotoxic. This cascade can be prevented and probably reversed by the use of highly active antiretroviral therapy, which controls viral replication both systemically and centrally. However, for those patients who have resistant virus and persistently high levels of replication, or who develop resistance or toxicity, other treatment strategies need to be developed. The control of excessive Microglial and macrophage activation or a diminution of astrocyte and neuronal apoptosis could have benefits in terms of cognitive function. We therefore need to develop further our understanding of the immunopathogenesis of HIV-associated dementia so that we can control a number of other steps in the cascade rather than simply controlling the viral replication

66. Williams K, Alvarez X, Lackner AA (2001) Central nervous system perivascular cells are immunoregulatory cells that connect the CNS with the peripheral immune system. Glia 36:156-164
    Abstract: Perivascular cells are a heterogeneous population found in the central nervous system (CNS) and the peripheral nervous system (PNS). Several terms are used for these cells, including perivascular cells, perivascular macrophages, perivascular Microglia, fluorescent granular perithelial cells (FGP), or Mato cells. Different terminology used may reflect subpopulations of perivascular cells within different anatomic regions and experimental paradigms, neuropathological conditions, and species studied. Different terminology also points to the lack of clear consensus of what cells are perivascular cells in different disease states and models, especially with breakdown of the blood-brain barrier (BBB). Despite this, there is consensus that perivascular cells, although a minor component of the CNS, are important immunoregulatory cells. Perivascular cells are bone marrow derived, continuously turn over in the CNS, and are found adjacent to CNS vessels. Thus, they are potential sensors of CNS and peripheral immune system perturbations; are activated in models of CNS inflammation, autoimmune disease, neuronal injury and death; and are implicated as phagocytic and pinocytotic cells in models of stroke and hypertension. Recent evidence from our laboratory implicate perivascular cells as primary targets of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) infection in the CNS of humans and macaques. This article reviews current knowledge of perivascular cells, including anatomic location and nomenclature and putative immunoregulatory roles, and discusses new data on the infection of these cells by SIV, their accumulation after SIV infection, and a possible role of the immune system in SIV encephalitis

67. Williams KC, Corey S, Westmoreland SV, Pauley D, Knight H, deBakker C, Alvarez X, Lackner AA (2001) Perivascular macrophages are the primary cell type productively infected by simian immunodeficiency virus in the brains of macaques: implications for the neuropathogenesis of AIDS. J.Exp.Med. 193:905-915
    Abstract: The macrophage is well established as a target of HIV and simian immunodeficiency virus (SIV) infection and a major contributor to the neuropathogenesis of AIDS. However, the identification of distinct subpopulations of monocyte/macrophages that carry virus to the brain and that sustain infection within the central nervous system (CNS) has not been examined. We demonstrate that the perivascular macrophage and not the parenchymal Microglia is the primary cell productively infected by SIV. We further demonstrate that although productive viral infection of the CNS occurs early, thereafter it is not easily detectable until terminal AIDS. The biology of perivascular macrophages, including their rate of turnover and replacement by peripheral blood monocytes, may explain the timing of neuroinvasion, disappearance, and reappearance of virus in the CNS, and questions the ability of the brain to function as a reservoir for productive infection by HIV/SIV

68. Zhao ML, Kim MO, Morgello S, Lee SC (2001) Expression of inducible nitric oxide synthase, interleukin-1 and caspase-1 in HIV-1 encephalitis. J.Neuroimmunol. 115:182-191
    Abstract: Inflammatory cytokines and enzymes such as IL-1 and inducible nitric oxide synthase (iNOS) may play an important role in the pathogenesis of AIDS dementia, a condition associated with infection of the CNS cells by the HIV-1. In this report, we investigated the expression of iNOS, IL-1, and caspase-1 (interleukin-1 converting enzyme) in HIV-1 encephalitis (HIVE) by immunocytochemistry and analyzed their expression with respect to HIV-1 infection and glial activation. In HIVE, all three molecules were expressed at high levels in areas of HIV-1 infection (Microglial nodules with HIV-1 p24 immunoreactivity) and in areas of diffuse white matter gliosis. Expression was cell-type specific, with IL-1 and caspase-1 being expressed in macrophages and Microglia, and iNOS in activated astrocytes. Multinucleated giant cells, a hallmark of virally infected cells, showed intense staining for both IL-1 and caspase-1, suggesting induction of these molecules by HIV-1. Double immunocytochemistry demonstrated a regional co-localization of astrocyte iNOS and Microglial IL-1 and caspase-1. These results support the notion that autocrine and paracrine interactions between HIV-1 infected macrophages and Microglia, activated Microglia, and astrocytes lead to expression of proinflammatory and neurotoxic molecules. iNOS and caspase-1 may provide additional therapeutic targets for HIVE

69. Zink MC, Coleman GD, Mankowski JL, Adams RJ, Tarwater PM, Fox K, Clements JE (2001) Increased macrophage chemoattractant protein-1 in cerebrospinal fluid precedes and predicts simian immunodeficiency virus encephalitis. J.Infect.Dis. 184:1015-1021
    Abstract: Macrophage chemoattractant protein-1 (MCP-1) may be a key trigger for the influx of macrophages into the brain in human immunodeficiency virus (HIV) encephalitis. In this study, simian immunodeficiency virus-infected macaques that developed moderate-to-severe encephalitis had significantly higher MCP-1 levels in cerebrospinal fluid (CSF) than in plasma as early as 28 days after inoculation, which was before the development of brain lesions. In contrast, CSF:plasma MCP-1 ratios remained constant at preinoculation levels in macaques that developed minimal or no encephalitis. Abundant MCP-1 protein and mRNA were detected in both macrophages and astrocytes in the brain. Macaques with increased MCP-1 in CSF had significantly greater expression of markers of macrophage and Microglia activation and infiltration (CD68; P= .003) and astrocyte activation (glial fibrillary acidic protein; P= .019 and P= .031 in white and gray matter, respectively). The results suggest that the CSF:plasma MCP-1 ratio may be a valuable prognostic marker for the development of HIV-induced central nervous system disease

70. Albright AV, Shieh JT, O'Connor MJ, Gonzalez-Scarano F (2000) Characterization of cultured Microglia that can be infected by HIV-1. J.Neurovirol. 6 Suppl 1:S53-S60
    Abstract: Parenchymal Microglia are targets of HIV infection. We, as well as others, have used in vitro Microglia culture systems to study the tropism and replication of HIV. Characterization of perivascular and parenchymal Microglia surface markers in vivo, in vitro, and ex vivo, has led to the understanding that these cell populations are different, and data from both the HIV and SIV models support the hypothesis that they may play different roles in infection of the CNS. We determined that human adult parenchymal Microglia cultured from temporal lobe tissue for use in HIV replication studies, were CD11c+, CD45+, CD68+,

71. Albright AV, Erickson-Viitanen S, O'Connor M, Frank I, Rayner MM, Gonzalez-Scarano F (2000) Efavirenz is a potent nonnucleoside reverse transcriptase inhibitor of HIV type 1 replication in Microglia in vitro. AIDS Res.Hum.Retroviruses 16:1527-1537
    Abstract: The objective of this study was to determine whether reverse transcriptase inhibitors (RTIs) could decrease viral replication in Microglia. Human Microglia obtained from individuals undergoing temporal lobectomy were cultured and infected with HIV-1 isolates from the central nervous system (CNS) as previously described (Strizki JM, et al. J Virol 1996;70:7654-7662). These Microglial cultures were treated with one of three nucleoside RTIs (NRTIs) or with efavirenz, a nonnucleoside RTI (NNRTI), at various time points before and during HIV-1 infection. The drug levels sufficient to provide > 90% inhibition of Microglial HIV replication (IC90) were determined by comparison of p24(gag) release in the cultures among treated and untreated Microglia. Infectious virus released from the infected cultures was also measured with U373-MAGI-CCR5 cells. Efavirenz, an NNRTI, blocked HIV-1(DS-br) infection of Microglia with an IC(90) of 0.7-7 nM. This value is similar to the efavirenz IC(90) values for inhibition of laboratory and clinical isolates in lymphocytes, is 2-3 logs lower than the IC90 values of AZT and d4T, and is 1-2 logs lower than that of ddC in Microglia. Efavirenz also inhibited infection with other neurotropic isolates, and with viruses isolated from other compartments that also replicated well in Microglia. Thus, efavirenz is a potent inhibitor of HIV-1 infection in Microglia. Furthermore, efavirenz IC(90) drug levels are present in the cerebrospinal fluid (CSF) of patients taking this once daily NNRTI

72. Boutet A, Altmeyer R, Hery C, Tardieu M (2000) Direct role of plasma membrane-expressed gp120/41 in toxicity to human astrocytes induced by HIV-1-infected macrophages. AIDS 14:2687-2697
    Abstract: OBJECTIVE: To compare astrocyte toxicity induced by plasma membrane-expressed gp120/41 and soluble gp120. DESIGN: Analysis of morphological alterations and lactate dehydrogenase (LDH) release from astrocytes in culture with monocytes infected with HIV-1, Microglia expressing Env of a macrophage-tropic HIV-1 isolate or soluble Env. METHODS: Primary human embryonic astrocytes were cultured with: monocytes infected with two M-tropic HIV-1 isolates (HIV-1(9533), HIV-1(BX08)); human Microglia infected with the defective Semliki Forest virus (SFV) vector coding for the env gene of HIV-1(BX08) isolate (SFVenvBX08); and soluble gp140 purified from baby hamster kidney cells transfected with the env gene of HIV-1(BX08) lacking the intracytoplasmic region of gp41 (SFVdelta envBX08). Gp120 mRNA levels were assessed by quantitative reverse transcriptase-polymerase chain reaction and the protein was detected by immunofluorescence in infected monocytes or Microglia. RESULTS: Contact of HIV-infected monocytes induced morphological changes in astrocytes and a 137% increase in LDH release at day 2 of co-culture compared with controls (uninfected monocytes). Gp120/41(BX08)-expressing Microglia induced a 170% increase in LDH release (relative to SFVLacZ-infected Microglia). Pretreatment of co-cultures with an anti-gp120 monoclonal antibody (mAb; NEA-9305) directed against the V3 loop inhibited LDH release. Soluble purified gp140 from BX08 isolate induced only a weak LDH release (104%). Finally, cytotoxicity was not blocked by treatment of the co-culture with Bordetella pertussis toxin, an inhibitor of Gi alpha protein-dependent receptors. CONCLUSION: HIV envelope glycoprotein expressed at the plasma membrane induced astrocyte damage more efficiently than its soluble counterpart. The V3 loop was involved in toxicity induction through a pathway independent of the Gi alpha protein-coupled receptor

73. Buch S, Pinson D, Hou Y, Adany I, Li Z, Mukherjee S, Jia F, Mackay G, Silverstein P, Kumar A, Narayan O (2000) Neuropathogenesis of chimeric simian human immunodeficiency virus infection in rhesus macaques. J.Med.Primatol. 29:96-106
    Abstract: Comparative studies were performed to determine the neuropathogenesis of infection in macaques with simian human immunodeficiency virus (SHIV)89.6P and SHIV(KU). Both viruses utilize the CD4 receptor and CXCR4 co-receptor. However, in addition, SHIV89.6P uses the CCR5 co-receptor. Both agents are dual tropic for CD4+ T cells and blood-derived macrophages of rhesus macaques. Following inoculation into macaques, both caused rapid elimination of CD4+ T cells but they varied greatly in mechanisms of neuropathogenesis. Two animals infected with SHIV89.6P developed typical lentiviral encephalitis in which multinucleated giant cell formation, nodular accumulations of Microglial cells, activated macrophages and astrocytes, and perivascular accumulations of mononuclear cells were present in the brain. Many of the macrophages in these lesions contained viral RNA. Three macaques infected with SHIV(KU) and killed on days 6, 11 and 18, respectively, developed a slowly progressive infection in the CNS but macrophages were not productively infected and there were no pathological changes in the brain. Two other animals infected with this virus and killed several months later showed minimal infection in the brain even though one of the two developed encephalitis of unknown etiology. The basic difference in the mechanisms of neuropathogenesis by the two viruses may be related to co-receptor usage. SHIV89.6P, in utilizing the CCR5 co-receptor, caused neuropathogenic effects that are similar to other neurovirulent primate lentiviruses

74. Chao CC, Hu S, Gekker G, Lokensgard JR, Heyes MP, Peterson PK (2000) U50,488 protection against HIV-1-related neurotoxicity: involvement of quinolinic acid suppression. Neuropharmacology 39:150-160
    Abstract: The pathogenesis of human immunodeficiency virus type 1 (HIV-1) encephalopathy has been associated with multiple factors including the neurotoxin quinolinate (an endogenous N-methyl-D-aspartate [NMDA] receptor ligand) and viral proteins. The kappa opioid receptor (KOR) agonist U50,488 recently has been shown to inhibit HIV-1 p24 antigen production in acutely infected Microglial cell cultures. Using primary human brain cell cultures in the present study, we found that U50,488 also suppressed in a dose-dependent manner the neurotoxicity mediated by supernatants derived from HIV-1-infected Microglia. This neuroprotective effect of U50,488 was blocked by the KOR selective antagonist nor-binaltorphimine. The neurotoxic activity of the supernatants from HIV-1-infected Microglia was blocked by the NMDA receptor antagonists 2-amino-5-phosphonovalerate and MK-801. HIV-1 infection of Microglial cell cultures induced the release of quinolinate, and U50,488 dose-dependently suppressed quinolinate release by infected Microglial cell cultures with a corresponding inhibition of HIV-1 p24 antigen levels. These findings suggest that the kappa opioid ligand U50,488 may have therapeutic potential in HIV-1 encephalopathy by attenuating Microglial cell production of the neurotoxin quinolinate and viral proteins

75. Choe W, Albright A, Sulcove J, Jaffer S, Hesselgesser J, Lavi E, Crino P, Kolson DL (2000) Functional expression of the seven-transmembrane HIV-1 co-receptor APJ in neural cells. J.Neurovirol. 6 Suppl 1:S61-S69
    Abstract: APJ is a recently described seven-transmembrane (7TM) receptor that is abundantly expressed in the central nervous system (CNS). This suggests an important role for APJ in neural development and/or function, but neither its cellular distribution nor its function have been defined. APJ can also serve as a co-receptor with CD4 for fusion and infection by some strains of human immunodeficiency virus (HIV-1) in vitro, suggesting a role in HIV neuropathogenesis if it were expressed on CD4-positive CNS cells. To address this, we examined APJ expression in cultured neurons, astrocytes, oligodendrocytes, Microglia and monocyte-derived macrophages utilizing both immunocytochemical staining with a polyclonal anti-APJ antibody and RT - PCR. We also analyzed the ability of a recently identified APJ peptide ligand, apelin, to induce calcium elevations in cultured neural cells. APJ was expressed at a high level in neurons and oligodendrocytes, and at lower levels in astrocytes. In contrast, APJ was not expressed in either primary Microglia or monocyte-derived macrophages. Several forms of the APJ peptide ligand induced calcium elevations in neurons. Thus, APJ is selectively expressed in certain CNS cell types and mediates intracellular signals in neurons, suggesting that APJ may normally play a role in signaling in the CNS. However, the absence of APJ expression in Microglia and macrophages, the prinicpal CD4-positive cell types in the brain, indicates that APJ is unlikely to mediate HIV-1 infection in the CNS

76. Cota M, Kleinschmidt A, Ceccherini-Silberstein F, Aloisi F, Mengozzi M, Mantovani A, Brack-Werner R, Poli G (2000) Upregulated expression of interleukin-8, RANTES and chemokine receptors in human astrocytic cells infected with HIV-1. J.Neurovirol. 6:75-83
    Abstract: Human immunodeficiency virus (HIV) infection of the central nervous system (CNS) affects primarily Microglial cells and astrocytes. Infection of these latter cells occurs independently of CD4 and is characterised by preferential accumulation of 2 Kb mRNA, encoding mostly Nef, and by low levels of 4.5 and 9 Kb RNAs. We have investigated the potential role of chronic HIV infection of human astrocytic cells on the expression of pro-inflammatory cytokines, chemokines and their receptors by comparing the infected TH4-7-5 with its parental uninfected 85HG66 cell lines. Upregulated levels of tumour necrosis factor-alpha (TNF-alpha) and of certain chemokines, namely interleukin-8 (IL-8) and regulated upon activation normal T cell expressed and secreted (RANTES), were observed in the infected versus uninfected cells, whereas monocyte chemotactic protein-1 (MCP-1) was comparably expressed in both cell lines. This pattern of expression was confirmed in primary foetal astrocytes transiently transfected with HIV. In addition, CXCR1, CXCR2 and CCR2b, receptors for IL-8 and MCP-1, respectively, were also found to be upregulated in TH4-7-5 versus 85HG66. CXCR4, the receptor of stromal cell derived factor-1 (SDF-1) and co-receptor for syncytium inducing HIVs, was comparably expressed in infected and uninfected astrocytic cells, whereas CCR5 was not detected in either cell line. Furthermore, treatment of TH4-7-5 cells with TNF-alpha or IL-1beta stimulated RNA and protein secretion of IL-8, MCP-1, and RANTES as well as HIV expression. Thus, our findings suggest that HIV infection of astrocytic cells can contribute to the establishment of a chronic inflammatory state in the CNS, eventually resulting in HIV encephalitis, by increasing the secretion of pro-inflammatory cytokines, such as TNF-alpha and several chemokines. Overexpression of chemokine receptors including CCR2b, CXCR1 and CXCR2 in infected astrocytic cells may contribute to HIV-induced damage of the CNS via autocrine/paracrine activation of astrocytes

77. Gabuzda D, Wang J (2000) Chemokine receptors and mechanisms of cell death in HIV neuropathogenesis. J.Neurovirol. 6 Suppl 1:S24-S32
    Abstract: Several chemokine receptors are used as coreceptors for HIV-1 entry in the central nervous system (CNS). CCR5 is the major coreceptor together with CD4 for HIV-1 infection of Microglia, the major target cells for HIV-1 infection in the CNS. CXCR4 and CCR3 are also expressed on Microglia and can mediate infection by certain HIV-1 isolates but at lower efficiency than CCR5. Additional chemokine coreceptors are expressed in the brain, but their role in HIV-1 neuropathogenesis has not been defined. The expression of CXCR4, and possibly other chemokine receptors, on subpopulations of neurons and glial cells may render neurons vulnerable to mechanisms of CNS injury induced by the HIV-1 gp120 Env protein. HIV-1 viruses which use CXCR4 and emerge during the late stages of HIV-1 infection may impact disease progression in the CNS by inducing apoptosis of neurons and other cell types. The neurodegenerative mechanisms may involve infection of Microglia by certain CXCR4 tropic viruses in addition to cellular dysfunction and apoptosis induced by HIV-1 gp120 binding to CXCR4. Understanding the role of CXCR4 and other chemokine receptors in HIV-1 neuropathogenesis will help to advance the development of new therapeutic strategies for the prevention and treatment of neurologic disorders associated with HIV-1 infection

78. Gray F, Adle-Biassette H, Brion F, Ereau T, le M, I, Levy V, Corcket G (2000) Neuronal apoptosis in human immunodeficiency virus infection. J.Neurovirol. 6 Suppl 1:S38-S43
    Abstract: Neuronal apoptosis has been shown to occur in HIV infection by a number of in vivo and in vitro studies, however, the cause of neuronal damage in AIDS is still unclear and its relationships with the cognitive disorders characteristic of HIV dementia remain a matter of debate. In this review, based on our experience, we analyse the techniques used to identify neuronal apoptosis on post-mortem AIDS brains and describe the relationships of neuronal apoptosis with the stage of disease, a history of HIV-dementia, the degree of productive HIV infection, Microglial activation, blood-brain barrier involvement and axonal damage. We conclude that the severity of neuronal apoptosis in the cerebral cortex correlates with the presence of cerebral atrophy, but not with the cognitive disorders. There is no global quantitative correlation between neuronal apoptosis and HIV encephalitis, Microglial activation or axonal damage. However we found some topographical correlation between these changes. We conclude that neuronal apoptosis and consequent neuronal loss, in HIV infected patients, are probably not related to a single cause. It seems likely that Microglial activation, directly or indirectly related to HIV infection of the CNS, plays a major role in its causation possibly through the mediation of oxidative stress. Axonal damage, either secondary to Microglial activation, or to the intervention of systemic factors may also contribute to neuronal apoptosis

79. Grulich AE, Dore GJ, Brew BJ (2000) Human Herpesvirus 8 and Protection from AIDS Dementia Complex. Herpes. 7:38-40
    Abstract: Infection with human herpesvirus 8 (HHV-8) has been associated with the development of three distinct conditions: Kaposi's sarcoma, body cavitybased lymphoma and Castleman's disease. HHV-8 produces chemokinelike proteins including viral macrophage inflammatory protein II, which has been shown to block human immunodeficiency virus 1 (HIV-1) infection of CD4-positive cells expressing CCR-3. As CCR-3 is a receptor for HIV-1 into Microglial cells, it has been hypothesized that HHV-8 infection may inhibit HIV-1 infection of the brain, thereby decreasing the incidence of AIDS dementia complex. We reviewed published studies of the incidence of AIDS dementia complex in individuals with and without Kaposi's sarcoma. The data are consistent in showing a negative association between Kaposi's sarcoma and AIDS dementia complex and, although sparse, support the hypothesis that productive HHV-8 infection decreases HIV-1 infection of the brain sufficiently to decrease the incidence of AIDS dementia complex. This negative association should be examined in further cohorts of HIV-1-infected subjects, to exclude alternative explanations

80. Guillemin GJ, Smith DG, Kerr SJ, Smythe GA, Kapoor V, Armati PJ, Brew BJ (2000) Characterisation of kynurenine pathway metabolism in human astrocytes and implications in neuropathogenesis. Redox.Rep. 5:108-111
    Abstract: The role of astrocytes in the production of the neurotoxin quinolinic acid (QUIN) and other products of the kynurenine pathway (KP) is controversial. Using cytokine-stimulated human astrocytes, we assayed key enzymes and products of the KP. We found that astrocytes lack kynurenine-hydroxylase so that large amounts of kynurenine (KYN) and kynurenic acid (KYNA) were produced, while minor amounts of QUIN were synthesised that were completely degraded. We then showed that kynurenine added to macrophages led to significant production of QUIN. These results suggest that astrocytes alone are neuroprotective by minimising QUIN production and maximising synthesis of KYNA. However, it is likely that, in the presence of macrophages and/or Microglia, astrocytes are neurotoxic by producing large concentrations of KYN that can be metabolised by neighbouring monocytic cells to QUIN

81. Hegg CC, Hu S, Peterson PK, Thayer SA (2000) Beta-chemokines and human immunodeficiency virus type-1 proteins evoke intracellular calcium increases in human Microglia. Neuroscience 98:191-199
    Abstract: Activation of beta-chemokine receptors, co-receptors for human immunodeficiency virus type-1 (HIV-1), stimulates movement and secretion in Microglia, possibly through a Ca(2+)-dependent mechanism. We studied chemokine activation of Ca(2+) signaling processes in Microglia. Human fetal Microglia were grown in primary culture and chemokine-induced increases in intracellular calcium concentration ([Ca(2+)](i)) were measured in single cells using indo-1-based microfluorimetry. Application of 50 ng/ml regulated on activation, normal T expressed and secreted (RANTES; 120 s) evoked responses in 26% of the Microglia (187/719 cells). [Ca(2+)](i) increased from a basal level of 66+/-6 nM to peak at 268+/-23 nM (n=187). Chemokine-evoked responses rapidly desensitized as indicated by the rapid return to basal [Ca(2+)](i) levels in the maintained presence of RANTES. The removal of extracellular Ca(2+) or stimulation in the presence of Ni(2+) (2mM) or La(3+) (100 microM) blocked the RANTES-elicited [Ca(2+)](i) increase. The L-type calcium channel antagonist nimodipine (10 microM) inhibited the RANTES-mediated increase in [Ca(2+)](i) by 80+/-16%. Thus, the RANTES-evoked calcium transient appears to result from Ca(2+) influx with little if any release from intracellular stores. Application of gp120(clade) (E) and gp120(CM235) (50 ng/ml) neither mimicked nor antagonized the RANTES-evoked response. Application of 50 ng/ml eotaxin (120 s) evoked an increase in [Ca(2+)](i) in 13% of the human Microglia in culture (61/469 cells). The HIV-1 regulatory protein Tat (50 ng/ml) increased the [Ca(2+)](i) in a subset of eotaxin-responsive cells (16/30). The L-type calcium channel antagonist nimodipine (3 microM) inhibited eotaxin- and Tat-mediated increases in [Ca(2+)](i) by 88+/-6% and 93+/-6%, respectively. Thus, activation of CCR3 appears to evoke Ca(2+) influx through L-type Ca(2+) channels.These results indicate that beta-chemokines, RANTES and eotaxin, activate a nimodipine sensitive Ca(2+) influx pathway in human fetal Microglia. HIV-1 Tat protein mimicked chemokine-mediated Ca(2+) signaling and may modulate the migratory and secretory responses of Microglia

82. Hein A, Martin JP, Koehren F, Bingen A, Dorries R (2000) In vivo infection of ramified Microglia from adult cat central nervous system by feline immunodeficiency virus. Virology 268:420-429
    Abstract: Infection of Microglial cells by the human immunodeficiency virus (HIV) is supposed to play an important role in the pathogenesis of AIDS-related central nervous system (CNS) complications. So far, however, experimental data about interactions between HIV and ramified Microglia from the adult CNS were only occasionally reported, making it difficult to understand the exact nature of pathogenic events contributing to HIV-encephalopathy. Therefore, we used the animal model of feline immunodeficiency virus (FIV) infection of domestic cats to establish an experimental system which is suitable for studying the relationships between an immunodeficiency virus and the mature ramified Microglia of the central nervous system. By means of density gradient centrifugation approximately 95% pure Microglial cells could be isolated from adult feline brain that were characterized by their CD45(low) phenotype. Resident Microglia extracted from the CNS of experimentally infected cats harbored FIV-specific DNA and cocultivation with mitogen-activated, but uninfected peripheral blood mononuclear cells (PBMC) resulted in recovery of high-titered infectious virus. Double labeling of brain cell monocultures explanted from persistently infected animals for both Microglia and FIV markers disclosed less than 1% of viral antigen expressing Microglial cells. This suggests that during the subclinical phase of the infection only a small number of brain-resident macrophages are productively infected. However, interaction of FIV-infected Microglia and inflammatory lymphocytes may promote viral replication, thus supporting viral spread in brain tissue

83. Ito M, Baker JV, Mock DJ, Goodman AD, Blumberg BM, Shrier DA, Powers JM (2000) Human herpesvirus 6-meningoencephalitis in an HIV patient with progressive multifocal leukoencephalopathy. Acta Neuropathol.(Berl) 100:337-341
    Abstract: Human herpesvirus 6 (HHV6) has been reported as a rare cause of meningoencephalitis and leukoencephalitis. We present an HIV-infected patient with lesions of progressive multifocal leukoencephalopathy (PML), but also meningoencephalitis apparently due to HHV6. Immunohistochemistry for HHV6 antigens and in situ polymerase chain reaction for HHV6 genome showed many positive lymphocytes and Microglia in the meningeal and cortical lesions. More importantly, dead and dying neurons were conspicuous; some were undergoing neuronophagia and some displayed evidence of HHV6 infection. A pathogenic role for this almost universal, and usually commensal, virus in inflammatory brain lesions and PML is briefly discussed

84. Jones MV, Bell JE, Nath A (2000) Immunolocalization of HIV envelope gp120 in HIV encephalitis with dementia. AIDS 14:2709-2713
    Abstract: Numerous studies have shown that the HIV envelope glycoprotein, gp120, is a potent neurotoxin. However, its role in the pathogenesis of HIV dementia had been questioned due to the lack of demonstration of its presence in vivo. We now demonstrate conclusively the presence of gp120 by immunohistochemistry in the brain of patients with HIV encephalitis who also had dementia. A highly specific anti-gp120 polyclonal sera was used on formalin fixed tissue. Gp120 staining cells were predominantly perivascular and included macrophages, Microglia and multinucleated giant cells. These studies provide an important missing link for the role of gp120 in the neuropathogenesis of HIV infection

85. Jung S, Aliberti J, Graemmel P, Sunshine MJ, Kreutzberg GW, Sher A, Littman DR (2000) Analysis of fractalkine receptor CX(3)CR1 function by targeted deletion and green fluorescent protein reporter gene insertion. Mol.Cell Biol. 20:4106-4114
    Abstract: The seven-transmembrane receptor CX(3)CR1 is a specific receptor for the novel CX(3)C chemokine fractalkine (FKN) (neurotactin). In vitro data suggest that membrane anchoring of FKN, and the existence of a shed, soluble FKN isoform allow for both adhesive and chemoattractive properties. Expression on activated endothelium and neurons defines FKN as a potential target for therapeutic intervention in inflammatory conditions, particularly central nervous system diseases. To investigate the physiological function of CX(3)CR1-FKN interactions, we generated a mouse strain in which the CX(3)CR1 gene was replaced by a green fluorescent protein (GFP) reporter gene. In addition to the creation of a mutant CX(3)CR1 locus, this approach enabled us to assign murine CX(3)CR1 expression to monocytes, subsets of NK and dendritic cells, and the brain Microglia. Analysis of CX(3)CR1-deficient mice indicates that CX(3)CR1 is the only murine FKN receptor. Yet, defying anticipated FKN functions, absence of CX(3)CR1 interferes neither with monocyte extravasation in a peritonitis model nor with DC migration and differentiation in response to microbial antigens or contact sensitizers. Furthermore, a prominent response of CX(3)CR1-deficient Microglia to peripheral nerve injury indicates unimpaired neuronal-glial cross talk in the absence of CX(3)CR1

86. Kitai R, Zhao ML, Zhang N, Hua LL, Lee SC (2000) Role of MIP-1beta and RANTES in HIV-1 infection of Microglia: inhibition of infection and induction by IFNbeta. J.Neuroimmunol. 110:230-239
    Abstract: Microglia are the major target of HIV-1 infection in the brain. Microglial infection is CD4-dependent, but the role of chemokine receptors CCR5 and CCR3 and their natural ligands in modulating HIV-1 infection in Microglia has been questioned. In primary human fetal Microglial cultures, we demonstrate that HIV-1 infection of these cells is dependent on CCR5, since an antibody to CCR5 completely blocked productive infection. Anti-CCR3, in contrast, had a smaller inhibitory effect which was not statistically significant. The chemokine ligands for CCR5, RANTES and MIP-1beta, also potently inhibited HIV-1 infection in Microglia, but the third ligand MIP-1alpha failed to show inhibition. Interestingly, when Microglial cultures were treated with antibodies specific to each of these chemokines, HIV-1 infection was enhanced by anti-RANTES and anti-MIP-1beta, but not by anti-MIP-1alpha. These results demonstrate the presence of endogenous chemokines that act as endogenous inhibitors of HIV-1 infection in Microglia. Additionally, IFNbeta, a known anti-viral cytokine, also provided potent inhibition of viral infection as well as induction of all three chemokines in Microglia. These results suggest the possibility that type I interferon can down-modulate Microglial HIV-1 infection in vivo by multiple mechanisms

87. Kolson DL, Gonzalez-Scarano F (2000) HIV and HIV dementia. J.Clin.Invest 106:11-13

88. Major EO, Rausch D, Marra C, Clifford D (2000) HIV-associated dementia. Science 288:440-442

89. Mayne M, Holden CP, Nath A, Geiger JD (2000) Release of calcium from inositol 1,4,5-trisphosphate receptor-regulated stores by HIV-1 Tat regulates TNF-alpha production in human macrophages. J.Immunol. 164:6538-6542
    Abstract: HIV-1 protein Tat is neurotoxic and increases macrophage and Microglia production of TNF-alpha, a cytopathic cytokine linked to the neuropathogenesis of HIV dementia. Others have shown that intracellular calcium regulates TNF-alpha production in macrophages, and we have shown that Tat releases calcium from inositol 1,4, 5-trisphosphate (IP3) receptor-regulated stores in neurons and astrocytes. Accordingly, we tested the hypothesis that Tat-induced TNF-alpha production was dependent on the release of intracellular calcium from IP3-regulated calcium stores in primary macrophages. We found that Tat transiently and dose-dependently increased levels of intracellular calcium and that this increase was blocked by xestospongin C, pertussis toxin, and by phospholipase C and type 1 protein kinase C inhibitors but not by protein kinase A or phospholipase A2 inhibitors. Xestospongin C, BAPTA-AM, U73122, and bisindolylmalemide significantly inhibited Tat-induced TNF-alpha production. These results demonstrate that in macrophages, Tat-induced release of calcium from IP3-sensitive intracellular stores and activation of nonconventional PKC isoforms play an important role in Tat-induced TNF-alpha production

90. McManus CM, Weidenheim K, Woodman SE, Nunez J, Hesselgesser J, Nath A, Berman JW (2000) Chemokine and chemokine-receptor expression in human glial elements: induction by the HIV protein, Tat, and chemokine autoregulation. Am.J.Pathol. 156:1441-1453
    Abstract: Human immunodeficiency virus (HIV) encephalitis is a prominent pathology seen in children infected with HIV. Immunohistochemical analyses of pediatric brain tissue showed distinct differences in expression of C-C chemokines and their receptors between children with HIV encephalitis and those with non-CNS-related pathologies. Evidence suggests that soluble factors such as HIV Tat released from HIV-infected cells may have pathogenic effects. Our results show Tat effects on chemokines and their receptors in Microglia and astrocytes as well as chemokine autoregulation in these cells. These results provide evidence for the complex interplay of Tat, chemokines, and chemokine receptors in the inflammatory processes of HIV encephalitis and illustrate an important new role for chemokines as autocrine regulators

91. Meucci O, Fatatis A, Simen AA, Miller RJ (2000) Expression of CX3CR1 chemokine receptors on neurons and their role in neuronal survival. Proc.Natl.Acad.Sci.U.S.A 97:8075-8080
    Abstract: Recent in vitro and in vivo studies have shown that the chemokine fractalkine is widely expressed in the brain and localized principally to neurons. Central nervous system expression of CX(3)CR1, the only known receptor for fractalkine, has been demonstrated exclusively on Microglia and astrocytes. Thus, it has been proposed that fractalkine regulates cellular communication between neurons (that produce fractalkine) and Microglia (that express its receptor). Here we show, for the first time, that hippocampal neurons also express CX(3)CR1. Receptor activation by soluble fractalkine induces activation of the protein kinase Akt, a major component of prosurvival signaling pathways, and nuclear translocation of NF-kappaB, a downstream effector of Akt. Fractalkine protects hippocampal neurons from the neurotoxicity induced by the HIV-1 envelope protein gp120(IIIB), an effect blocked by anti-CX(3)CR1 antibodies. Experiments with two different inhibitors of the phosphatidylinositol 3-kinase, a key enzyme in the activation of Akt, and with a phospholipid activator of Akt demonstrate that Akt activation is responsible for the neuroprotective effects of fractalkine. These data show that neuronal CX(3)CR1 receptors mediate the neurotrophic effects of fractalkine, suggesting that fractalkine and its receptor are involved in a complex network of both paracrine and autocrine interactions between neurons and glia

92. Milligan ED, Mehmert KK, Hinde JL, Harvey LO, Martin D, Tracey KJ, Maier SF, Watkins LR (2000) Thermal hyperalgesia and mechanical allodynia produced by intrathecal administration of the human immunodeficiency virus-1 (HIV-1) envelope glycoprotein, gp120. Brain Res. 861:105-116
    Abstract: Astrocytes and Microglia in the spinal cord have recently been reported to contribute to the development of peripheral inflammation-induced exaggerated pain states. Both lowering of thermal pain threshold (thermal hyperalgesia) and lowering of response threshold to light tactile stimuli (mechanical allodynia) have been reported. The notion that spinal cord glia are potential mediators of such effects is based on the disruption of these exaggerated pain states by drugs thought to preferentially affect glial function. Activation of astrocytes and Microglia can release many of the same substances that are known to mediate thermal hyperalgesia and mechanical allodynia. The aim of the present series of studies was to determine whether exaggerated pain states could also be created in rats by direct, intraspinal immune activation of astrocytes and Microglia. The immune stimulus used was peri-spinal (intrathecal, i.t.) application of the Human Immunodeficiency Virus type 1 (HIV-1) envelope glycoprotein, gp120. This portion of HIV-1 is known to bind to and activate Microglia and astrocytes. Robust thermal hyperalgesia (tail-flick, TF, and Hargreaves tests) and mechanical allodynia (von Frey and touch-evoked agitation tests) were observed in response to i.t. gp120. Heat denaturing of the complex protein structure of gp120 blocked gp120-induced thermal hyperalgesia. Lastly, both thermal hyperalgesia and mechanical allodynia to i.t. gp120 were blocked by spinal pretreatment with drugs (fluorocitrate and CNI-1493) thought to preferentially disrupt glial function

93. Minami M, Satoh M (2000) [Chemokines as mediators for intercellular communication in the brain]. Nippon Yakurigaku Zasshi 115:193-200
    Abstract: Chemokines constitute a large and still growing family of structurally-related small (8-10 kDa) cytokines that have chemotactic activity for leukocytes. Recently, some receptors for chemokines were reported to be used as a co-receptor by HIV at infection. In addition to their well-established role in inflammatory response and recently-reported role as a co-receptor for HIV, recent data suggest that chemokines and their receptors physiologically and pathologically play crucial roles as the mediators for intercellular communication among the cells intrinsic to and recruited into the brain; i.e., neurons, astrocytes, Microglia, endothelial cells and leukocytes. Some chemokines such as SDF-1 and fractalkine are constitutively produced in the brain, implicating that they have an important role in maintenance of CNS homeostasis or determination of the patterning of neurons and/or glial cells in developing brain and normal adult brain. Chemokines such as MCP-1, MIP-1 alpha and CINC were shown to be induced by various neuroinflammatory stimuli, suggesting that they are involved in various neurodegenerative diseases such as multiple sclerosis, Alzheimer's disease, stroke and AIDS dementia syndrome. Chemokines and their receptors are potential targets for therapeutic intervention in neurodegenerative diseases

94. Nebuloni M, Pellegrinelli A, Ferri A, Tosoni A, Bonetto S, Zerbi P, Boldorini R, Vago L, Costanzi G (2000) Etiology of Microglial nodules in brains of patients with acquired immunodeficiency syndrome. J.Neurovirol. 6:46-50
    Abstract: Microglial nodules associated with opportunistic and HIV-related lesions are frequently found in the brains of AIDS patients. However, in many cases, the causative agent is only presumptively suspected. We reviewed 199 brains of AIDS patients with micronodular lesions to clarify their etiology by immunohistochemistry (to Toxoplasma gondii, cytomegalovirus, herpes simplex virus I/II, varicella zoster virus and HIV-p24 core protein), PCR (for herpetic viruses and Mycobacterium tuberculosis) and electron microscopy. Productive HIV infection was observed in 110 cases (55.1%): 30 cases with Toxoplasma gondii encephalitis, 30 with cytomegalovirus encephalitis, eight with multiple cerebral diseases, while in the remaining 42 cases HIV was the only pathogenetic agent. Multinucleated giant cells (hallmark of HIV infection) were found in the MGNs of 85/110 cases with HIV-related lesions; the remaining 25 cases had only p24 positive cells but no multinucleated giant cells. In these latter cases the micronodular lesions had been initially attributed to the main opportunistic agent found in the brain, or defined as subacute encephalitis. Individual Microglial nodules positive for an opportunistic pathogen were generally negative for HIV antigens. In 13 cases no opportunistic agent or HIV productive infection was found. In these cases, PCR and electron microscopy examination for HIV and other viral infections were negative. Our data suggest that HIV-immunohistochemistry should be used for the etiological diagnosis of micronodular lesions in AIDS brains, even in the presence of other pathogens. After extensive search, the etiology of the Microglial nodules remains unknown in only a small percentage of cases

95. Pugh CR, Johnson JD, Martin D, Rudy JW, Maier SF, Watkins LR (2000) Human immunodeficiency virus-1 coat protein gp120 impairs contextual fear conditioning: a potential role in AIDS related learning and memory impairments. Brain Res. 861:8-15
    Abstract: Many AIDS patients suffer from cognitive impairments including deficits in learning and memory. The Human Immunodeficiency Virus-1 (HIV-1) envelope glycoprotein gp120 is one possible mediator of these impairments. This is because gp120 activates brain Microglial cells and astrocytes, and in vivo activation of glia leads to the release of the proinflammatory cytokine interleukin-1 beta (IL-1beta). gp120 induced IL-1beta release could be involved in producing memory impairments associated with AIDS because central IL-1beta activity adversely affects cognitive function. The reported experiments evaluated the effects of i.c.v. gp120 administration and subsequent IL-1beta activity on learning and memory processes in the rat. Intracerebroventricular gp120 produced memory impairments on hippocampally dependent contextual fear conditioning, but not hippocampally independent auditory-cue fear conditioning following post-conditioning gp120 administration. Central gp120 administration also caused increases in IL-1beta protein levels in the hippocampus and frontal cortex but not in the hypothalamus. gp120 induced memory impairments were blocked by 2 different IL-1 antagonists, alpha melanocyte stimulating hormone (alphaMSH) and interleukin-1 receptor antagonist (IL-1ra). Finally, heat denaturation of the tertiary structure of gp120 abolished its effects on fear conditioning, suggesting that gp120 impairs contextual fear conditioning by binding to its receptors on glia

96. Rostasy K, Monti L, Yiannoutsos C, Wu J, Bell J, Hedreen J, Navia BA (2000) NFkappaB activation, TNF-alpha expression, and apoptosis in the AIDS-Dementia-Complex. J.Neurovirol. 6:537-543
    Abstract: The role of NFkappaB activation and its relationship to inflammatory mediators and apoptosis in the HIV-infected brain have remained uncertain. The cellular and regional distribution of NFkappaB, TNF-alpha, and apoptosis was examined in the frontal cortex (FC), deep white matter (DWM) and the basal ganglia (BG) of 17 patients with ADC. Nuclear staining for NFkappaB was localized predominantly to perivascular Microglia/macrophages in the BG and DWM and correlated with ADC severity. Correlations were further found with HLA-DR, iNOS, TNF-alpha, and gp41 expression in these regions. The number of TUNEL-positive cells, particularly in the BG, correlated with ADC stage. Logistic regression analysis further showed a significant relationship between the likelihood of TUNEL staining in the BG and worsening cognitive impairment

97. Sheng WS, Hu S, Hegg CC, Thayer SA, Peterson PK (2000) Activation of human Microglial cells by HIV-1 gp41 and Tat proteins. Clin.Immunol. 96:243-251
    Abstract: The viral proteins, Tat (HIV-1 nuclear protein) and gp41 (HIV-1 coat protein), detected in the brains of HIV-1-infected patients have been shown to be neurotoxic. We investigated the effects of HIV-1 Tat and gp41 proteins on cytokine, chemokine, and superoxide anion (O(-)(2)) production by Microglia, the resident macrophages of the brain. Tat and gp41 dose-dependently stimulated cytokine and chemokine production by Microglia. Peak production of these cytokines and chemokines differed in Microglial cells treated with gp41 and Tat. Expression of cytokine and chemokine mRNA was also stimulated in gp41- and Tat-treated Microglia. Neither gp41 nor Tat alone stimulated O(-)(2) production by Microglia. Treatment of Microglial cells with Tat but not with gp41 evoked an increase in intracellular Ca(2+). The results of this study suggest that HIV-1 Tat and gp41 proteins impact several key functions of Microglial cells which could contribute to the neuropathogenesis of HIV-1

98. Shieh JT, Martin J, Baltuch G, Malim MH, Gonzalez-Scarano F (2000) Determinants of syncytium formation in Microglia by human immunodeficiency virus type 1: role of the V1/V2 domains. J.Virol. 74:693-701
    Abstract: Microglia are the main reservoir for human immunodeficiency virus type 1 (HIV-1) in the central nervous system (CNS), and multinucleated giant cells, the result of fusion of HIV-1-infected Microglia and brain macrophages, are the neuropathologic hallmark of HIV dementia. One potential explanation for the formation of syncytia is viral adaptation for these CD4(+) CNS cells. HIV-1(BORI-15), a virus adapted to growth in Microglia by sequential passage in vitro, mediates high levels of fusion and replicates more efficiently in Microglia and monocyte-derived-macrophages than its unpassaged parent (J. M. Strizki, A. V. Albright, H. Sheng, M. O'Connor, L. Perrin, and F. Gonzalez-Scarano, J. Virol. 70:7654-7662, 1996). Since the interaction between the viral envelope glycoprotein and CD4 and the chemokine receptor mediates fusion and plays a key role in tropism, we have analyzed the HIV-1(BORI-15) env as a fusogen and in recombinant and pseudotyped viruses. Its syncytium-forming phenotype is not the result of a switch in coreceptor use but rather of the HIV-1(BORI-15) envelope-mediated fusion of CD4(+)CCR5(+) cells with greater efficiency than that of its parental strain, either by itself or in the context of a recombinant virus. Genetic analysis indicated that the syncytium-forming phenotype was due to four discrete amino acid differences in V1/V2, with a single-amino-acid change between the parent and the adapted virus (E153G) responsible for the majority of the effect. Additionally, HIV-1(BORI-15) env-pseudotyped viruses were less sensitive to decreases in the levels of CD4 on transfected 293T cells, leading to the hypothesis that the differences in V1/V2 alter the interaction between this envelope and CD4 or CCR5, or both. In sum, the characterization of the envelope of HIV-1(BORI-15), a highly fusogenic glycoprotein with genetic determinants in V1/V2, may lead to a better understanding of the relationship between HIV replication and syncytium formation in the CNS and of the importance of this region of gp120 in the interaction with CD4 and CCR5

99. Speth C, Joebstl B, Barcova M, Dierich MP (2000) HIV-1 envelope protein gp41 modulates expression of interleukin-10 and chemokine receptors on monocytes, astrocytes and neurones. AIDS 14:629-636
    Abstract: OBJECTIVE: To analyse the effect of HIV-1 transmembrane protein gp41 on cytokine production and chemokine receptor expression in blood and brain. DESIGN: Because previous results had demonstrated that recombinant gp41 contributes to HIV-induced dysfunction of blood immune cells we investigated its effect on interleukin (IL)-10 synthesis and expression of the HIV coreceptors CCR5 and CXCR4 in different human brain cells. METHODS: Astrocytic, Microglial and neuronal cell lines were incubated with the extracellular domain of gp41 (aa565-647). Secretion of IL-10 into the medium was measured by ELISA. Chemokine receptor expression was analysed by fluorescence activated cell sorting and by RT-PCR. RESULTS: Incubation of the astrocytic cell line U87 with gp41 induced more than a 10 fold up-regulation of IL-10 secretion. This modulation was shown to be time- and dose-dependent. Use of inhibitors for different signal transduction pathways indicated a similar transduction cascade for the alteration of IL-10 production in astrocytes as in monocytes with participation of cAMP/adenylate cyclase and activation of p70S6 kinase. To a lesser extent IL-10 synthesis was also up-regulated by gp41 in the neuronal cell line SK-N-SH. In all cell types up-regulation of IL-10 paralleled by an enhanced expression of the chemokine receptor and HIV-1 coreceptor CCR5. This up-regulation was driven by IL-10 as shown by use of an IL-10 antibody. Expression of the chemokine receptor CXCR4 was only slightly altered. CONCLUSIONS: These findings suggest a role for gp41 in the modulation of brain-specific host defence, cell migration and cell infectivity by HIV

100. van der MP, Ulrich AM, Gonzalez-Scarano F, Lavi E (2000) Immunohistochemical analysis of CCR2, CCR3, CCR5, and CXCR4 in the human brain: potential mechanisms for HIV dementia. Exp.Mol.Pathol. 69:192-201
     Abstract: The CXC chemokine receptor CXCR4 was the first molecule identified as a coreceptor working in conjunction with CD4 to mediate cellular entry for the human immunodeficiency virus (HIV-1). Since that original discovery, 11 other seven-mtransmembrane domain molecules, many of which are chemokine receptors, have been shown to facilitate HIV entry into cells. These include CCR5, CCR3, CCR2, CCR1, CCR8, CX3CR1, STRL33 (BONZO), GPR15 (BOB), GPR1, US28, and APJ. In studies done by this and other labs, CCR3, CCR5, and CXCR4 have been identified in CNS Microglia and several laboratories, including ours, have shown that CXCR4 is expressed in neurons. Neuronal expression of CCR2, CCR3, and CCR5 has been less consistent. We performed a semiquantitative immunohistochemical analysis of the expression of CCR2, CCR3, CCR5, and CXCR4 in 23 regions of the brain and in two sections of the spinal cord. Hippocampal neurons were positive for CCR2, CCR3, and CXCR4, but not for CCR5. In other regions of the brain, neurons, and glial cells reacted with anti-CCR2, anti-CCR3, and anti-CXCR4 antibodies, whereas only glial cells (primarily Microglia) were positive for CCR5. The areas of highest expression, however, seem to be subcortical regions and the limbic system. The limbic system plays a key role in memory, and the presence of CXCR4-which can bind the viral envelope protein gp120-min a subset of neurons from this system may play a role in the development of HIV-related dementia

101. Vicenzi E, Alfano M, Ghezzi S, Gatti A, Veglia F, Lazzarin A, Sozzani S, Mantovani A, Poli G (2000) Divergent regulation of HIV-1 replication in PBMC of infected individuals by CC chemokines: suppression by RANTES, MIP-1alpha, and MCP-3, and enhancement by MCP-1. J.Leukoc.Biol. 68:405-412
     Abstract: We investigated the role of different CC chemokines, including regulated upon activation normal T cell expressed and secreted (RANTES), macrophage inflammatory protein-lalpha (MIP-1alpha), monocyte chemotactic protein-1 (MCP-1), and MCP-3 on virus replication in cultures established from CD8+ T cell-depleted peripheral blood mononuclear cells (PBMC) of HIV-infected individuals that were either cocultivated with allogeneic T cell blasts (ATCB) of uninfected individuals or directly stimulated by mitogen plus interleukin-2. RANTES was the only chemokine that showed a clear-cut suppressive effect on HIV replication in both culture systems, although inhibitory effects were frequently also observed with MIP-1alpha, MCP-3, and, occasionally, with MCP-1. In contrast, MCP-1 frequently enhanced HIV production in most patients' cultures or cocultures that were characterized by secreting relatively low levels (<20 ng/mL) of MCP-1. When CD8-depleted PBMC of HIV+ individuals were cocultivated with ATCB of uninfected healthy donors, a positive correlation was observed between MCP-1 concentrations and the enhancement of HIV-1 replication occurring after depletion of CD8+ cells from donors' cells. Depletion of CD14+ cells (monocytes) from ATCB resulted in the down-regulation of virus replication during co-cultivation with CD8-depleted PBMC of infected individuals. Of interest, MCP-1 up-regulated HIV production in these CD14-depleted ATCB cocultures. Altogether these observations suggest that MCP-1 may represent an important factor enhancing HIV spreading, particularly in anatomical sites, such as the brain, where infection of macrophages and Microglial cells plays a dominant role

102. Wiley CA, Achim CL, Hammond R, Love S, Masliah E, Radhakrishnan L, Sanders V, Wang G (2000) Damage and repair of DNA in HIV encephalitis. J.Neuropathol.Exp.Neurol. 59:955-965
     Abstract: Neuronal damage and dementia are common sequelae of HIV encephalitis. The mechanism by which HIV infection of CNS macrophages results in neuronal damage is not known. We examined the brains from 15 AIDS autopsies (8 with HIV encephalitis and 7 without) and 4 non-infected control autopsies for the presence of DNA strand breaks, for associated changes in the expression of the DNA repair enzymes KU80 and Poly (ADP-ribose) polymerase (PARP), and for accumulation of amyloid precursor protein (APP). Abundant DNA damage was observed with terminal transferase-mediated dUTP nick end-labeling (TUNEL), however, there was no morphologic evidence of significant neuroglial apoptosis. The DNA repair enzyme KU80 was immunocytochemically detectable in neuronal and glial cells in autopsy brains from patients with and without HIV encephalitis; however, in cases with HIV encephalitis the staining was more prominent than in the infected or non-infected controls without encephalitis. There was no difference in KU80 immunostaining in oligodendroglia from autopsies with and without encephalitis. Immunostaining for PARP was more intense in gray and white matter of cases with HIV encephalitis. No clear spatial relationship existed between expression of DNA repair enzymes and the spatial proximity of Microglial nodules or HIV-infected macrophages. The cytoplasm of cortical and subcortical neurons immunostained for APP Stronger cortical neuronal APP staining was observed in cases without HIV encephalitis. Staining of deep gray matter neurons was similar, irrespective of the presence or absence of encephalitis. While foci of intense APP staining were noted in white matter not related to HIV infection, they were associated with foci of opportunistic infections (e.g. due to CMV or PML). We conclude that damaged DNA and altered patterns of expression of DNA repair proteins and APP are common findings in the brains of AIDS patients at autopsy, but do not have a spatial relationship to HIV-infected macrophages

103. Wittekindt B, Betz H, Laube B (2000) Subunit-dependent inhibition of recombinant rodent N-methyl-D-aspartate receptors by a HIV-1 glycoprotein 120 derived peptide. Neurosci.Lett. 280:151-154
     Abstract: Considerable evidence suggests that low (picomolar) concentrations of the HIV-1 envelope glycoprotein gp120 induce neuronal cell death by stimulating the release of Microglial toxins, which in turn activate N-methyl-D-aspartate (NMDA) receptors. Conversely, high (micromolar) concentrations of gp120 have been reported to directly inhibit NMDA receptor-mediated currents and do not induce neurotoxicity. Here we show that micromolar concentrations of a synthetic peptide corresponding to the V3-loop of gp120 (V3-pep) inhibited agonist responses of recombinant heteromeric rodent NMDA receptors expressed in Xenopus laevis oocytes by decreasing their apparent glycine affinity. Different combinations of NMDA receptor subunits displayed differential sensitivities to inhibition by V3-pep, with a potency rank order of NR1/2B > NR1/2D > NR1/2C > or = NR1/2A. Our observations may provide an explanation for the reduced neurotoxicity of high doses of gp120 in cell cultures and may be useful for the pharmacological discrimination of NMDA receptor subtypes

104. Xiong H, Zeng YC, Lewis T, Zheng J, Persidsky Y, Gendelman HE (2000) HIV-1 infected mononuclear phagocyte secretory products affect neuronal physiology leading to cellular demise: relevance for HIV-1-associated dementia. J.Neurovirol. 6 Suppl 1:S14-S23
     Abstract: Viral and cellular products from HIV-1-infected and/or immune competent mononuclear phagocytes (MP) (brain macrophages and Microglia) affect neuronal function during HIV-1-associated dementia (HAD). Neurotoxic MP factors include, but are not limited to, pro-inflammatory cytokines, chemokines, platelet activating factor, arachidonic acid and its metabolites, nitric oxide, progeny virions and viral structural and regulatory proteins. The mechanisms for immune-mediated neural injury in HAD, only now, are being unraveled. In this regard, we reviewed the current knowledge of how postmitotic neurons, which can neither divide nor be replaced, are damaged by MP secretory activities. Linking neuronal function with brain MP activation was made possible by placing viral and/or immune products onto neurons and measuring cell signaling events or through ex vivo electrophysiological tests on MP-treated brain slices. Such linkages are shown, in this report, by select demonstrations of MP factors which cause neuronal dysfunction in HAD

105. Yeh MW, Kaul M, Zheng J, Nottet HS, Thylin M, Gendelman HE, Lipton SA (2000) Cytokine-stimulated, but not HIV-infected, human monocyte-derived macrophages produce neurotoxic levels of l -cysteine. J.Immunol. 164:4265-4270
     Abstract: Approximately one-quarter of individuals with AIDS develop neuropathological symptoms that are attributable to infection of the brain with HIV. The cognitive manifestations have been termed HIV-associated dementia. The mechanisms underlying HIV-associated neuronal injury are incompletely understood, but various studies have confirmed the release of neurotoxins by macrophages/Microglia infected with HIV-1 or stimulated by viral proteins, including the envelope glycoprotein gp120. In the present study, we investigated the possibility that l -cysteine, a neurotoxin acting at the N-methyl-d -aspartate subtype of glutamate receptor, could contribute to HIV-associated neuronal injury. Picomolar concentrations of gp120 were found to stimulate cysteine release from human monocyte-derived macrophages (hMDM) in amounts sufficient to injure cultured rat cerebrocortical neurons. TNF-alpha and IL-1beta, known to be increased in HIV-encephalitic brains, as well as a cellular product of cytokine stimulation, ceramide, were also shown to induce release of cysteine from hMDM in a dose-dependent manner. A TNF-alpha-neutralizing Ab and an IL-1betaR antagonist partially blocked gp120-induced cysteine release, suggesting that these cytokines may mediate the actions of gp120. Interestingly, hMDM infected with HIV-1 produced significantly less cysteine than uninfected cells following stimulation with TNF-alpha. Our findings imply that cysteine may play a role in the pathogenesis of neuronal injury in HIV-associated dementia due to its release from immune-activated macrophages but not virus-infected macrophages. Such uninfected cells comprise the vast majority of mononuclear phagocytes (macrophages and Microglia) found in HIV-encephalitic brains

106. Zujovic V, Benavides J, Vige X, Carter C, Taupin V (2000) Fractalkine modulates TNF-alpha secretion and neurotoxicity induced by Microglial activation. Glia 29:305-315
     Abstract: Among the chemokine family, fractalkine shows unusual properties: it exists as a membrane-bound and soluble protein, and both fractalkine and its receptor CX(3)CR1 are expressed predominantly in the central nervous system. In rat cell culture models, the chemokine fractalkine was expressed in neurons and Microglia, but not in astrocytes and its receptor exclusively localized to Microglial cells, where its expression was downregulated by treatment with the bacterial endotoxin (LPS). In Microglial cultures, LPS (10 ng/ml) induced a marked increase in the release of the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). The effects of LPS on TNF-alpha secretion were partially blocked (30%) by fractalkine and the effects of fractalkine were reversed by a polyclonal anti-fractalkine antibody. When Microglial-associated fractalkine was neutralized by anti-fractalkine antibody, the LPS response was increased by 80%, suggesting tonic activation of Microglial fractalkine receptors by endogenous fractalkine. The effects of the antibody were antagonized by the addition of fractalkine. LPS-activated Microglia were neurotoxic when added to neuronal hippocampal culture, producing 20% neuronal death, as measured by NeuN-positive cell counting. An anti-fractalkine antibody produced neurotoxic effects of similar magnitude in this co-culture system and also markedly potentiated the neurotoxic effects of LPS-activated Microglia (40% neuronal death). These results suggest that endogenous fractalkine might act tonically as an anti-inflammatory chemokine in cerebral tissue through its ability to control and suppress certain aspects of Microglial activation. These data may have relevance to degenerative conditions such as multiple sclerosis, in which cerebral inflammatory processes may be activated

107. Adamson DC, McArthur JC, Dawson TM, Dawson VL (1999) Rate and severity of HIV-associated dementia (HAD): correlations with Gp41 and iNOS. Mol.Med. 5:98-109
     Abstract: BACKGROUND: Fifteen to thirty percent of AIDS patients develop some type of neurologic disorder during the course of their illness and the vast majority of these neurologic disorders will be HIV-associated dementia (HAD). These patients can exhibit varying degrees of severity and rates of progression of HAD. Neuropathologic variables that are associated with the rate of progression of HAD are not known. MATERIALS AND METHODS: Tissue was collected at autopsy from the Johns Hopkins University HIV Neurology Program. Seventy-one AIDS patients of this prospectively characterized population were followed until death to obtain information on dementia severity and the rate of neurological progression. Immunoblot analysis of immunological nitric oxide synthase (iNOS), HAM56, gp41, p24, gp120, and beta-tubulin was performed and the levels of iNOS, HAM56, gp41, and p24 were normalized to beta-tubulin and analyzed for significance by means of the Kruskal-Wallis test for multiple groups. RESULTS: We have identified unique groups within this spectrum and designated them slow, moderate, and rapid progressors. Slow and moderate progressors' neurological progression occurs over a course of months to years, whereas the rapid progressors' disease shows rapid increases in severity over weeks to months. In the present study we demonstrate that the severity and rate of progression of HAD correlates significantly with levels of the HIV-1 coat protein, gp41, iNOS, and HAM56, a marker of Microglial/macrophage activation. CONCLUSION: The severity and rate of progression of HAD correlates with indices of immune activation as well as levels of iNOS and gp41. There appears to be a threshold effect in which high levels of gp41, iNOS, and immune activation are particularly associated with severe (Memorial Sloan-Kettering score 3 to 4) and rapidly progressive HAD

108. Adle-Biassette H, Chretien F, Wingertsmann L, Hery C, Ereau T, Scaravilli F, Tardieu M, Gray F (1999) Neuronal apoptosis does not correlate with dementia in HIV infection but is related to Microglial activation and axonal damage. Neuropathol.Appl.Neurobiol. 25:123-133
     Abstract: To characterize the distribution of apoptotic neurons and their relationships with the stage of disease, a history of HIV-dementia, and the degree of productive HIV infection, Microglial activation and axonal damage, we examined the brains of 40 patients. Samples of frontal and temporal cortex, basal ganglia and brain stem were taken post-mortem from 20 patients with AIDS (including three with HIV-dementia, and eight with cognitive disorders that did not fulfil the criteria for HIV-dementia), 10 HIV-positive asymptomatic cases and 10 seronegative controls. Neuronal apoptosis was demonstrated by in situ end labelling in 18 AIDS cases and two pre-AIDS cases; a single apoptotic neuron was present in the temporal cortex of a control. Semiquantitative evaluation showed that the severity of neuronal apoptosis in the cerebral cortex correlated with the presence of cerebral atrophy, but not with a history of HIV dementia. There was no global quantitative correlation between neuronal apoptosis and HIV encephalitis or Microglial activation. However, there was some topographical correlation between these changes. In the basal ganglia, apoptotic neurons were much more abundant in the vicinity of multinucleated giant cells and/or p24 expressing cells. Microglial activation was constantly present in these areas. Axonal damage was identified using beta-amyloid-precursor protein (betaAPP) immunostaining in 17 AIDS and eight pre-AIDS brains. Although no global quantitative correlation could be established between axonal damage and neuronal apoptosis there was an obvious topographic correlation supporting the view that axonal damage, either secondary to local Microglial activation or due to the intervention of systemic factors, may also contribute to neuronal apoptosis

109. Albright AV, Frank I, Gonzalez-Scarano F (1999) Interleukin-2 treatment of Microglia has no effect on in vitro HIV infection. AIDS 13:527-528

110. Albright AV, Shieh JT, Itoh T, Lee B, Pleasure D, O'Connor MJ, Doms RW, Gonzalez-Scarano F (1999) Microglia express CCR5, CXCR4, and CCR3, but of these, CCR5 is the principal coreceptor for human immunodeficiency virus type 1 dementia isolates. J.Virol. 73:205-213
     Abstract: Microglia are the main human immunodeficiency virus (HIV) reservoir in the central nervous system and most likely play a major role in the development of HIV dementia (HIVD). To characterize human adult Microglial chemokine receptors, we analyzed the expression and calcium signaling of CCR5, CCR3, and CXCR4 and their roles in HIV entry. Microglia expressed higher levels of CCR5 than of either CCR3 or CXCR4. Of these three chemokine receptors, only CCR5 and CXCR4 were able to transduce a signal in Microglia in response to their respective ligands, MIP-1beta and SDF-1alpha, as recorded by single-cell calcium flux experiments. We also found that CCR5 is the predominant coreceptor used for infection of human adult Microglia by the HIV type 1 dementia isolates HIV-1DS-br, HIV-1RC-br, and HIV-1YU-2, since the anti-CCR5 antibody 2D7 was able to dramatically inhibit Microglial infection by both wild-type and single-round luciferase pseudotype reporter viruses. Anti-CCR3 (7B11) and anti-CXCR4 (12G5) antibodies had little or no effect on infection. Last, we found that virus pseudotyped with the DS-br and RC-br envelopes can infect cells transfected with CD4 in conjunction with the G-protein-coupled receptors APJ, CCR8, and GPR15, which have been previously implicated in HIV entry

111. Altmeyer R, Mordelet E, Girard M, Vidal C (1999) Expression and detection of macrophage-tropic HIV-1 gp120 in the brain using conformation-dependent antibodies. Virology 259:314-323
     Abstract: HIV-1 envelope proteins gp120 and gp41 are likely to play a role in the pathogenesis of HIV-associated neurocognitive disorders. While detection of gp120 in HIV-infected cell cultures is easy, it has not yet been possible to identify gp120 in human or animal brains in situ. The difficulty in detecting gp120 could be due to low expression levels of the protein, to the shedding of gp120 from infected macrophages/Microglia, or to the use of inappropriate gp-specific antibodies. We addressed these questions by analyzing the subcellular localization, oligomeric structure, and shedding behavior of gp120 from a macrophage-tropic, CCR5-dependent primary isolate, BX08, expressed by a Semliki Forest virus replicon (SFVenvBX08) in vitro. We used the same SFV system injected in vivo into the rat brain in an attempt to detect gp120 in situ. Our results show that gp120/41 is expressed as monomers, dimers, and trimers in cell culture. Immunocytochemical analysis revealed that intracytoplasmic gp120 can be recognized by an anti-V3 antibody, whereas gp120 at the plasma membrane is detected exclusively by a conformation-dependent antibody. In the rat brain, the SFV vector allows gene expression in neurons from day 3 to day 9 after injection without any apparent brain damage nor reactive astrogliosis. In SFVenvBX08-infected neurons only conformation-dependent antibodies allowed gp120 labeling. These results suggest that previous difficulties in detecting gp120 in brain tissues may be due to the use of antibodies which were unable to recognize gp120 at the plasma membrane

112. An SF, Groves M, Giometto B, Beckett AA, Scaravilli F (1999) Detection and localisation of HIV-1 DNA and RNA in fixed adult AIDS brain by polymerase chain reaction/in situ hybridisation technique. Acta Neuropathol.(Berl) 98:481-487
     Abstract: In the brain of patients with AIDS, HIV-1 is localised in a productive form in mononuclear cells. One issue that still needs clarification is whether HIV is localised in cells other than those of mononuclear lineage. Gene amplification by polymerase chain reaction/in situ hybridisation (PCR-IS) could shed light on it. In this study, formalin-fixed, paraffin-embedded brain tissue from ten adult AIDS sufferers was used. Five of them showed evidence of HIV encephalitis (HIVE), five did not show any abnormality. Nested PCR revealed HIV-1 DNA in all HIVE cases and in three of the group without HIVE. HIV-1 DNA and RNA were also detected in situ in seven cases (all seven were also HIV-1 DNA positive in tube). A higher signal was located in the white than in the grey matter. HIV-1 DNA was found in Microglia, macrophages, perivascular cells, multinucleated gaint cells (MGC) and in CD68-negative cells. Some of them were identified as endothelial cells, astrocytes and oligodendrocytes. Reverse transcriptase-PCR-IS was positive in macrophages, MGC, endothelial and glial cells. These results confirm infection of endothelial cells and other glial cells and give clues about the route of entry of virus into the central nervous system and the pathogenesis of the disease. This study did not give any convincing evidence supporting an infection of neurons by HIV-1

113. An SF, Groves M, Gray F, Scaravilli F (1999) Early entry and widespread cellular involvement of HIV-1 DNA in brains of HIV-1 positive asymptomatic individuals. J.Neuropathol.Exp.Neurol. 58:1156-1162
     Abstract: There is overwhelming evidence that invasion of the central nervous system (CNS) by HIV-1 takes place at an early stage of the infection. It has been demonstrated that HIV-1 DNA is present in brains of asymptomatic individuals. Evidence of immune activation and increased expression of cytokines suggested that neuropathological changes and neuronal and axonal damage could be the effect of the presence of the virus. The purpose of the study is to ascertain whether target cells for HIV-1 in brain of patients at early stage of the infection are the same as those found in AIDS sufferers or if the distribution seen in AIDS patients results from the late spreading of the infection from cells considered traditionally the reservoir of the virus, i.e. Microglial cells. Eighteen brains, all HIV-1 DNA positive, as shown by nested polymerase chain reaction (PCR), were selected among the group of HIV-1 positive asymptomatic cases. In 6 of them, HIV-1 DNA was detected by PCR in situ. Positive cells included astrocytes and endothelial cells, in addition to Microglial cells. We conclude that astrocytes and endothelial cells are already infected at an early (asymptomatic) stage of the infection and suggest that they might contribute to the damage of the CNS

114. Bagetta G, Corasaniti MT, Berliocchi L, Nistico R, Giammarioli AM, Malorni W, Aloe L, Finazzi-Agro A (1999) Involvement of interleukin-1beta in the mechanism of human immunodeficiency virus type 1 (HIV-1) recombinant protein gp120-induced apoptosis in the neocortex of rat. Neuroscience 89:1051-1066
     Abstract: The effect of subchronic intracerebroventricular injection of the human immunodeficiency virus type 1 (HIV-1) recombinant protein gp120 (100 ng, given daily for up to seven consecutive days) on interleukin-1beta expression was studied by immunohistochemistry in the brain of adult rats. In comparison to control, bovine serum albumin (300 ng, given intracerebroventricularly for up to seven days) -treated animals (n=6), interleukin-1beta immunoreactivity increased in the brain cortex and hippocampus of rats (n=6) receiving a single injection of the viral protein 24 h before analysis with more substantial increases being observed in these regions of the brain (n=6) after seven days treatment. Double-labelling immunofluorescence experiments support a neuronal and, possibly, a Microglial cell origin for gp120-enhanced interleukin-1beta expression. Transmission electron microscopy analysis of brain tissue sections revealed that combination treatments (given intracerebroventricularly daily for seven days) with gp120 (100 ng) and interleukin-1 receptor antagonist (80 ng) or with the interleukin converting enzyme inhibitor II (100 pmol), but not with leupeptin (100 pmol), prevented apoptotic death of rat (n=6/group) brain cortical cells typically elicited by the viral protein. These data demonstrate that gp120 enhances interleukin-1beta expression in the brain and this may be involved in the mechanism underlying apoptosis induced by gp120 in the brain cortex of rat. Further support to this hypothesis comes from the evidence that intracerebroventricular injection of murine recombinant interleukin-1beta (200 U, given daily for seven consecutive days) produces DNA fragmentation in the brain cortex of rat (n=6). Interestingly, the latter treatment enhanced nerve growth factor level in the hippocampus but not in the cerebral cortex and this coincides with a similar effect recently reported in identical brain areas of rats treated likewise with gp120. In conclusion, the present data demonstrate that treatment with gp120 enhances interleukin-1beta expression and this participates in the mechanism of apoptotic cell death in the brain cortex of rat. By contrast, in the hippocampus, gp120-enhanced interleukin-1beta expression elevates nerve growth factor that may prevent or delay apoptosis in this plastic region of the rat brain

115. Bencheikh M, Bentsman G, Sarkissian N, Canki M, Volsky DJ (1999) Replication of different clones of human immunodeficiency virus type 1 in primary fetal human astrocytes: enhancement of viral gene expression by Nef. J.Neurovirol. 5:115-124
     Abstract: Dementia is a common complication of AIDS which is associated with human immunodeficiency virus type 1 (HIV-1) infection of brain macrophages and Microglia. Recent studies have shown that astrocytes are also infected in the brain but HIV-1 replication in these cells is restricted. To determine virus specificity of this restriction we tested the expression of 15 HIV-1 molecular clones in primary human fetal astrocytes by infection and DNA transfection. Infection with cell-free viruses was poorly productive and revealed no clone-specific differences. In contrast, transfected cells produced transiently high levels of HIV-1 p24 core antigen, up to 50 nanograms per ml culture supernatant, and nanogram levels of p24 were detected 3-4 weeks after transfection of some viral clones. The average peak expression of HIV-1 in astrocytes varied as a function of viral clone used by a factor of 15 but the differences and the subsequent virus spread did not correlate with the tropism of the viral clones to T cells or macrophages. Functional vif, vpu, and vpr genes were dispensable for virus replication from transfected DNA, but intact nef provided a detectable enhancement of early viral gene expression and promoted maintenance of HIV-1 infection. We conclude that primary astrocytes present no fundamental barriers to moderate expression of different strains of HIV-1 and that the presence of functional Nef is advantageous to virus infection in these cells

116. Berman NE, Marcario JK, Yong C, Raghavan R, Raymond LA, Joag SV, Narayan O, Cheney PD (1999) Microglial activation and neurological symptoms in the SIV model of NeuroAIDS: association of MHC-II and MMP-9 expression with behavioral deficits and evoked potential changes. Neurobiol.Dis. 6:486-498
     Abstract: HIV-1 causes cognitive and motor deficits and HIV encephalitis (HIVE) in a significant proportion of AIDS patients. Neurological impairment and HIVE are thought to result from release of cytokines and other harmful substances from infected, activated Microglia. In this study, the quantitative relationship between Microglial activation and neurological impairment was examined in the simian immunodeficiency model of HIVE. Macaque monkeys were infected with a passaged, neurovirulent strain of simian immunodeficiency virus, SIV(mac)239(R71/17E). In concurrent studies, functional impairment was assessed by motor and auditory brainstem evoked potentials and by measurements of cognitive and motor behavioral deficits. Brain tissue was examined by immunohistochemistry using two markers of Microglia activation, MHC-II and matrix metalloproteinase-9 (MMP-9). The inoculated animals formed two groups: rapid progressors, which survived 6-14 weeks postinoculation, and slow progressors, which survived 87-109 weeks. In the rapid progressors, two patterns of MHC-II expression were present: (1) a widely disseminated pattern of MHC-II expressing Microglia and Microglial nodules in cortical gray matter and subcortical white matter, and (2) a more focal pattern in which MHC-II expressing Microglia were concentrated into white matter. Animals exhibiting both patterns of Microglial activation showed mild to severe changes in cognitive and motor behavior and evoked potentials. All rapid progressors showed expression of MMP-9 in Microglia located in subcortical white matter. In the slow progressors MHC-II and MMP-9 staining was similar to uninoculated control macaques, and there was little or no evidence of HIVE. These animals showed behavioral deficits at the end of the disease course, but little changes in evoked potentials. Thus, increases in MHC-II and MMP-9 expression are associated with development of cognitive and motor deficits, alterations in evoked potentials, and rapid disease progression

117. Boddeke EW, Meigel I, Frentzel S, Biber K, Renn LQ, Gebicke-Harter P (1999) Functional expression of the fractalkine (CX3C) receptor and its regulation by lipopolysaccharide in rat Microglia. Eur.J.Pharmacol. 374:309-313
     Abstract: Functional expression of CX3CR1, a recently discovered receptor for the chemokine fractalkine, was investigated in cultured rat Microglia. Reverse transcriptase polymerase chain reaction (PCR) experiments show abundant expression of fractalkine receptor mRNA in Microglia. mRNA expression of fractalkine was undetectable in astrocytes and Microglia but was very strong in cortical neurons. Incubation of Microglia with lipopolysaccharide (100 ng/ml) transiently suppressed expression of fractalkine receptor mRNA. Fractalkine induced a concentration-dependent (10(-10)-10(-8) M) and, at high concentrations, oscillatory mobilization of intracellular Ca2+ in Microglia The concentration-response curve of fractalkine was shifted to the right after 12 h incubation with lipopolysaccharide. It is concluded that treatment with endotoxin downregulates expression of fractalkine receptor mRNA in rat Microglia and suppresses the functional response to fractalkine

118. Bonwetsch R, Croul S, Richardson MW, Lorenzana C, Valle LD, Sverstiuk AE, Amini S, Morgello S, Khalili K, Rappaport J (1999) Role of HIV-1 Tat and CC chemokine MIP-1alpha in the pathogenesis of HIV associated central nervous system disorders. J.Neurovirol. 5:685-694
     Abstract: Two syndromes affecting cognitive and motor function in the setting of AIDS have been described as HIV encephalopathy (HIVE) and progressive multifocal leukoencephalopathy (PML). HIVE is characterized by the presence of Microglial nodules with accompanying astrocytosis. PML is a fatal demyelinating disease of the white matter induced by the human papovavirus JCV which causes cytolytic destruction of glial cells. In addition to the effect of HIV-1 induced immune suppression, HIV may act directly as a co-factor for stimulation of JCV replication in AIDS patients, in part due to Tat-induced activation of JCV gene transcription. Since Tat has been implicated in CNS pathogenesis, we examined its localization in CNS specimens from HIV infected patients with HIVE and PML as well as controls. Based on the observation of CC chemokine induction in monocytes by Tat, we also examined the cellular localization of the CC chemokine Macrophage Inflammatory Protein-1alpha (MIP-1alpha) and its cognate receptor CCR-5 in these samples. In HIVE, Tat was primarily localized in astrocytes and Microglia, within the nodular lesions. In PML, a marked increase in the number of Tat positive astrocytes was observed. In both HIVE and PML, prominent expression of MIP-1alpha and CCR-5 was found within areas containing histopathological lesions. CCR-5 positivity of Microglia was localized primarily to nodular lesions in HIVE. In PML, increased numbers of cells with monocyte/Microglial morphology were observed relative to HIVE. The increased MIP-1 alpha positivity, and potentially other chemokines, may contribute to the pathogenesis of PML in the setting of HIV infection. Tat may play an important role in the pathogenesis of both HIV associated CNS disease states, acting indirectly through cytokine and chemokine dysregulation

119. Boven LA, Gomes L, Hery C, Gray F, Verhoef J, Portegies P, Tardieu M, Nottet HS (1999) Increased peroxynitrite activity in AIDS dementia complex: implications for the neuropathogenesis of HIV-1 infection. J.Immunol. 162:4319-4327
     Abstract: Oxidative stress is suggested to be involved in several neurodegenerative diseases. One mechanism of oxidative damage is mediated by peroxynitrite, a neurotoxic reaction product of superoxide anion and nitric oxide. Expression of two cytokines and two key enzymes that are indicative of the presence of reactive oxygen intermediates and peroxynitrite was investigated in brain tissue of AIDS patients with and without AIDS dementia complex and HIV-seronegative controls. RNA expression of IL-1beta, IL-10, inducible nitric oxide synthase, and superoxide dismutase (SOD) was found to be significantly higher in demented compared with nondemented patients. Immunohistochemical analysis showed that SOD was expressed in CD68-positive Microglial cells while inducible nitric oxide synthase was detected in glial fibrillary acidic protein (GFAP)-positive astrocytes and in equal amounts in Microglial cells. Approximately 70% of the HIV p24-Ag-positive macrophages did express SOD, suggesting a direct HIV-induced intracellular event. HIV-1 infection of macrophages resulted in both increased superoxide anion production and elevated SOD mRNA levels, compared with uninfected macrophages. Finally, we show that nitrotyrosine, the footprint of peroxynitrite, was found more intense and frequent in brain sections of demented patients compared with nondemented patients. These results indicate that, as a result of simultaneous production of superoxide anion and nitric oxide, peroxynitrite may contribute to the neuropathogenesis of HIV-1 infection

120. Brenneman DE, Hauser J, Spong CY, Phillips TM, Pert CB, Ruff M (1999) VIP and D-ala-peptide T-amide release chemokines which prevent HIV-1 GP120-induced neuronal death. Brain Res. 838:27-36
     Abstract: Vasoactive intestinal peptide (VIP) and DAPTA (D-ala(1)-peptide T-amide, a gp120-derived octapeptide homologous to VIP) prevent neuronal cell death produced by five variants of HIV-1 (human immunodeficiency virus) envelope protein (gp120). VIP or DAPTA treatment of astrocyte cultures resulted in the release of macrophage inflammatory protein-1alpha (MIP-1alpha) and RANTES, beta chemokines known to block gp120 interactions with Microglial chemokine receptors. In rat cerebral cortical cultures, gp120-induced neuronal killing was partially or completely prevented by chemokines that stimulate the CXCR4, CCR3 or CCR5 chemokine receptors. Chemokines exhibited marked differences in potency and efficacy in preventing toxicity associated with five gp120 variants (LAV/BRU, CM243, RF, SF2, and MN). RANTES had the broadest and most potent inhibition (IC(50)<3 pM for RF isolate). An octapeptide derived from RANTES also exhibited neuroprotection from gp120 (RF isolate) toxicity (IC(50)=0.3 microM). Treatment with chemokines alone had no detectable effect on neuronal cell number. However, antiserum to MIP-1alpha produced neuronal cell death that was prevented by co-treatment with MIP-1alpha, suggesting that this endogenous chemokine exerts a tonic regulation important to neuronal survival. The neuroprotective action of VIP on gp120 was attenuated by co-treatment with anti-MIP-1alpha. These studies suggest that the neuroprotective action of VIP is linked in part to its release of MIP-1alpha. Furthermore, neuroprotection produced by chemokines is dependent on both the type of chemokine and the variant structure of gp120 and may be relevant to drug strategies for the treatment of AIDS dementia

121. Carson MJ, Sutcliffe JG, Campbell IL (1999) Microglia stimulate naive T-cell differentiation without stimulating T-cell proliferation. J.Neurosci.Res. 55:127-134
     Abstract: A major question relevant to the initiation and progression of inflammation and autoimmune processes within the central nervous system (CNS) is whether resident Microglia or only infiltrating macrophage can productively interact with T-cells that enter the CNS either actively through extravasation or passively through defects in the blood brain barrier (BBB). We isolated Microglia and macrophage from the brains of healthy adult mice and transgenic mice that displayed many features of multiple sclerosis and HIV leukoencephalopathy due to the astrocytic expression of interleukin (IL)-3 and compared their antigen-presenting cell (APC) functions. We found that unactivated Microglia isolated from healthy nontransgenic mice and activated Microglia isolated from transgenic siblings are relatively weak stimulators of naive T-cell proliferation compared to macrophage populations. The APC function of activated, but not unactivated, Microglia could be increased by treatment acutely with lipopolysaccharide (LPS)/interferon gamma (IFN-gamma). However, this treatment also induced the apparent production of prostaglandins, which reduced T-cell proliferation when indomethacin was absent from the assay cultures. Strikingly, even in the absence of stimulated T-cell proliferation, both unactivated and activated Microglia stimulated the differentiation of naive T-cells into Th1 effector cells, although neither Microglial population was a more effective inducer than macrophages or splenic APCs. Thus, while Microglia are clearly capable of productively interacting with naive T-cells, macrophages have a more robust APC function

122. Clifford DB (1999) Central Neurologic Complications of HIV Infection. Curr.Infect.Dis.Rep. 1:187-191
     Abstract: Human immunodeficiency virus enters the brain at the time of infection and remains in the central nervous system (CNS) throughout the infection. Three currently active topics of clinical importance will be reviewed. First, the role of cerebrospinal fluid (CSF) viral loads as a function of brain infection and performance will be assessed. Evidence is building that CSF viral load is a useful measure in assessing CNS infection in clinical trial settings with possible application to monitoring the effect of therapy in neurologically symptomatic subjects. Second, potential roles of cytokines and their receptors for CNS disease will be updated. The impact of cytokine receptors on modes of invasion of endothelial cells, monocytes, Microglia, and neurons will be discussed. Finally, recently reported controlled therapeutic trials will be reviewed including the impact of antiretroviral therapy and hypothesis-driven neuroprotective strategy studies

123. Conant K, McArthur JC, Griffin DE, Sjulson L, Wahl LM, Irani DN (1999) Cerebrospinal fluid levels of MMP-2, 7, and 9 are elevated in association with human immunodeficiency virus dementia. Ann.Neurol. 46:391-398
     Abstract: Pathological evidence suggests that alterations of the blood-brain barrier (BBB) may occur in association with human immunodeficiency virus (HIV) dementia (HIVD). Increased BBB permeability could contribute to the development of dementia by facilitating the entry of activated and infected monocytes, as well as potentially toxic serum proteins, into the central nervous system. One mechanism by which BBB permeability may be altered is through increased activity of select matrix metalloproteinases (MMPs). In the present study, we examined the possibility that MMPs that target critical BBB proteins, including laminin, entactin, and collagen type IV, are elevated in the cerebrospinal fluid (CSF) of patients with HIVD. We also examined the possibility that such MMPs could be produced by brain-derived cells, and that MMP production by these cells might be increased by tumor necrosis factor-alpha, an inflammatory cytokine that is produced by HIV-infected monocytes/Microglia and is elevated in HIVD. By using western blot and enzyme-linked immunosorbent assay, we observed that CSF levels of pro-MMP-2 and pro-MMP-7 were increased in association with HIVD. In addition, through the use of gelatin substrate zymography, a sensitive functional assay for MMP-2 and MMP-9, we observed that MMP-2 or pro-MMP-9 activity was more frequently detectable in the CSF of individuals with HIV dementia (9/16) than in the CSF from either nondemented seropositive (2/11) or seronegative (0/11) controls. Although the presence of MMPs in the serum could contribute to elevated levels in the CSF, we also show that brain-derived cells release MMP-2, 7, and 9, and that such release is increased after their stimulation with tumor necrosis factor-alpha. Together, these results suggest that elevated CSF levels of select MMPs may reflect immune activation within the central nervous system. They also suggest that further studies may be warranted to determine whether these proteins may play a role in the development of symptomatic neurological disease

124. Epstein LG, Gelbard HA (1999) HIV-1-induced neuronal injury in the developing brain. J.Leukoc.Biol. 65:453-457
     Abstract: HIV-1 infection of the nervous system causes neuronal injury and death, resulting in cognitive, motor, and behavioral dysfunction in both adults and children. In infants a characteristic feature of HIV-1 infection is impaired brain growth resulting in secondary microcephaly with onset between 2 and 4 months of age. This post-natal period of brain development is particularly vulnerable to excitotoxic neuronal injury due to the active synaptogenesis and pruning that takes place at this age associated with over-expression of excitatory amino acid (EAA) receptors. HIV-1 infection of brain Microglia and perivascular macrophages results in chronic inflammation manifest pathologically as diffuse Microglial activation and reactive astrogliosis. Several inflammatory products of activated Microglia, including tumor necrosis factor alpha (TNF-alpha) and platelet-activating factor (PAF) have been shown to act as neuronal toxins. This toxic effect can be antagonized by blocking NMDA (or AMPA) glutamate receptors, suggesting that (weak) excitotoxicity leads to oxidative stress, neuronal injury, and apoptosis. HIV-1 infection and chronic inflammation may also contribute disruption of the blood-brain barrier and could result in further entry into the CNS of toxic viral or cellular products or additional HIV-1-infected cells. We hypothesize that prolonged Microglial activation during HIV-1 infection underlies the neuronal injury and impaired brain growth in affected infants. Further investigation of the interaction between HIV-1-infected/activated Microglia and developing neurons seems warranted. The current understanding of HIV neuropathogenesis implies that therapeutic strategies should target the sustained immune activation in Microglia, attempt to repair the integrity of the blood-brain barrier, and provide "neuroprotection" from excitotoxic neuronal injury

125. Gabuzda D, Wang J (1999) Chemokine receptors and virus entry in the central nervous system. J.Neurovirol. 5:643-658
     Abstract: Several members of the chemokine receptor family are used as coreceptors together with CD4 for HIV and SIV entry in the central nervous system (CNS). CCR5 is the major coreceptor for HIV-1 infection of macrophages and Microglia, the major target cells for HIV-1 infection in the CNS. CXCR4 and CCR3 are also expressed on Microglia and can mediate infection by certain HIV-1 isolates but at lower efficiency than CCR5. Additional chemokine receptors that can function as HIV-1 and SIV coreceptors for a subset of viruses are expressed in the brain (i.e. Apj, CX3CR1, STRL33/BONZO, and gpr1), but their role in CNS infection has not been defined. The expression of CXCR4, and possibly other chemokine receptors, on subpopulations of neurons and glial cells may contribute to mechanisms of CNS injury that are independent of viral infection. Understanding the role of chemokine receptors and their chemokine ligands in HIV-1 and SIV infection of the CNS will elucidate mechanisms of viral tropism and pathogenesis and advance the development of new therapeutic strategies

126. Gonzalez-Scarano F, Baltuch G (1999) Microglia as mediators of inflammatory and degenerative diseases. Annu.Rev.Neurosci. 22:219-240
     Abstract: Microglia are the principal immune cells in the central nervous system (CNS) and have a critical role in host defense against invading microorganisms and neoplastic cells. However, as with immune cells in other organs, Microglia may play a dual role, amplifying the effects of inflammation and mediating cellular degeneration as well as protecting the CNS. In entities like human immunodeficiency virus (HIV) infection of the nervous system, Microglia are also critical to viral persistence. In this review we discuss the role of Microglia in three diseases in which their activity is at least partially deleterious: HIV, multiple sclerosis, and Alzheimer's disease

127. Hao HN, Lyman WD (1999) HIV infection of fetal human astrocytes: the potential role of a receptor-mediated endocytic pathway. Brain Res. 823:24-32
     Abstract: HIV infects Microglia and astrocytes both in vivo and in vitro. Although there is a significant amount of information about Microglial infection, data regarding astrocytes are more limited. For example, little is known about the initial membrane events occurring between HIV and astrocytes. Also, the mechanism by which HIV enters these cells remains to be determined. To address these questions, we exposed human astrocyte cultures to either HIV or to the HIV glycoprotein gp120. The cultures were analyzed for viral infection and gp120 binding to cultured cells by light and electron microscopy (EM) with and without immunocytochemistry, respectively; ligand-receptor biochemistry; and, Western, Northern and Southern blot analyses. The results of these studies showed that HIV binds to astrocytes via gp120 and a cell surface molecule weighing approximately 65 kDa that is neither CD4 nor galactocerebroside. Furthermore, binding of gp120 to astrocytes was concentration dependent and displayed a curve consistent with ligand-receptor binding. Additionally, radiolabeled gp120 binding was displaced by unlabeled gp120 but not by deglycosylated gp120, suggesting that the binding was specific. By EM, HIV virions were seen in clathrin-coated pits and in cytoplasmic vacuoles. This suggests linkage, in astrocytes, between a plasma membrane-associated protein that can act as a receptor for HIV and an endosomal pathway

128. Hibbitts S, Reeves JD, Simmons G, Gray PW, Epstein LG, Schols D, De Clercq E, Wells TN, Proudfoot AE, Clapham PR (1999) Coreceptor ligand inhibition of fetal brain cell infection by HIV type 1. AIDS Res.Hum.Retroviruses 15:989-1000
     Abstract: The capacity of a panel of HIV-1 isolates to infect primary mixed fetal brain cell cultures was estimated and their sensitivity to inhibition by a range of coreceptor ligands assessed. Our results show that (1) HIV-1 strains that predominantly use CCR5 or only CXCR4 are able to infect Microglia in primary brain cell cultures, and (2) ligands to these two coreceptors can inhibit brain cell infection. CCR5 ligands (including AOP-RANTES, a potent inhibitor of CCR5-dependent infection), however, blocked infection only weakly, raising the possibility that alternative unidentified coreceptors are also used. Interestingly, vMIP-II, a chemokine encoded by the Kaposi sarcoma-associated herpes virus (KSHV), reduced brain cell infection by all HIV-1 strains tested, including both R5 and X4 viruses. Our results therefore indicate that novel drugs targeted to the major HIV-1 coreceptors will influence HIV replication in the brain, if they cross the blood-brain barrier

129. Howard SA, Nakayama AY, Brooke SM, Sapolsky RM (1999) Glucocorticoid modulation of gp120-induced effects on calcium-dependent degenerative events in primary hippocampal and cortical cultures. Exp.Neurol. 158:164-170
     Abstract: The HIV coat protein gp120 has been implicated in damaging the nervous system and may play a role in AIDS-related dementia complex. The glycoprotein triggers the release of a glutamatergic agent from infected Microglia and macrophages, causing NMDA receptor- and calcium-dependent excitotoxic damage to neurons. We have previously shown that glucocorticoids, the adrenal steroids secreted during stress, worsen gp120 neurotoxicity and calcium mobilization in various brain regions. This study explores events down-stream of gp120-induced calcium mobilization, specifically, generation of reactive oxygen species (ROS) and subsequent lipid peroxidation, destruction of the cytoskeleton through spectrin proteolysis, and the glucocorticoid modulation of these events in primary hippocampal cultures. We observe that 200 pM gp120 causes a significant accumulation of ROS, including superoxide, and of lipid peroxidation. Counter to our predictions, pretreatment with the glucocorticoid corticosterone (CORT) did not worsen the effects of gp120 on ROS accumulation, but did increase lipid peroxidation. We also observed that neither gp120 alone nor gp120 plus CORT caused detectable proteolysis of the cytoskeletal protein spectrin, whose breakdown has been shown to be a damaging consequence of calcium excess in other models of necrotic neuronal injury

130. James HJ, Sharer LR, Zhang Q, Wang HG, Epstein LG, Reed JC, Gelbard HA (1999) Expression of caspase-3 in brains from paediatric patients with HIV-1 encephalitis. Neuropathol.Appl.Neurobiol. 25:380-386
     Abstract: Apoptosis of neurones, macrophages, and Microglia occurs in the brains of paediatric patients with human immunodeficiency virus (HIV) type 1 encephalitis, which is often associated with pre-mortem neurological disease (progressive encephalopathy). We have previously reported that TUNEL-positive neurones in brain tissue from paediatric patients with HIV type 1 encephalitis and progressive encephalopathy are strikingly devoid of the pro-apoptotic gene product Bax, in marked contrast to brain-resident macrophages and Microglia. Using immunocytochemical methods, the present study demonstrate that neurones in patients with HIV type 1 encephalitis and progressive encephalopathy, as well as macrophages and Microglia, but not astrocytes, overexpress caspase-3, a pro-apoptotic enzyme that is proteolytically activated downstream of Bax-Bcl-2 dysregulation. Co-localization of neuronal cytoplasmic caspase-3 and nuclear TUNEL staining, a marker for fragmented DNA, was also infrequently observed in brain tissue from patients with HIV type 1 encephalitis and progressive encephalopathy. These findings suggest that vulnerable neurones in brain tissue from patients with HIV virus type 1 encephalitis and progressive encephalopathy undergo apoptosis by a mechanism that involves upregulation of caspase-3 in a pathway that is independent of Bax-Bcl-2 dysregulation. Furthermore, caspase-3 upregulation in apoptotic neurones likely occurs prior to DNA fragmentation

131. Kaul M, Lipton SA (1999) Chemokines and activated macrophages in HIV gp120-induced neuronal apoptosis. Proc.Natl.Acad.Sci.U.S.A 96:8212-8216
     Abstract: HIV-1 glycoprotein gp120 induces injury and apoptosis in rodent and human neurons in vitro and in vivo and is therefore thought to contribute to HIV-associated dementia. In addition to CD4, different gp120 isolates bind to the alpha- or beta-chemokine receptors CXCR4 and CCR5, respectively. These and other chemokine receptors are on brain macrophages/Microglia, astrocytes, and neurons. Thus, apoptosis could occur via direct interaction of gp120 with neurons, indirectly via stimulation of glia to release neurotoxic factors, or via both pathways. Here we show in rat cerebrocortical cultures that recapitulate the type and proportion of cells normally found in brain, i.e., neurons, astrocytes, and macrophages/Microglia, that the beta-chemokines RANTES (regulated on activation, normal T cell expressed and secreted) and macrophage inflammatory protein (MIP-1beta) protect neurons from gp120SF2-induced apoptosis. The gp120SF2 isolate prefers binding to CXCR4 receptors, similar to the physiological alpha-chemokine ligands, stromal cell-derived factor (SDF)-1alpha/beta. SDF-1alpha/beta failed to prevent gp120SF2 neurotoxicity, and in fact also induced neuronal apoptosis. We could completely abrogate gp120SF2-induced neuronal apoptosis with the tripeptide TKP, which inhibits activation of macrophages/Microglia. In contrast, TKP or depletion of macrophages/Microglia did not prevent SDF-1 neurotoxicity. Inhibition of p38 mitogen-activated protein kinase ameliorated both gp12

132. Koutsilieri E, Sopper S, Heinemann T, Scheller C, Lan J, Stahl-Hennig C, ter M, V, Riederer P, Gerlach M (1999) Involvement of Microglia in cerebrospinal fluid glutamate increase in SIV-infected rhesus monkeys (Macaca mulatta). AIDS Res.Hum.Retroviruses 15:471-477
     Abstract: Cerebrospinal fluid (CSF) samples were collected from 24 uninfected and 24 SIV251 MPBMC-infected rhesus monkeys during early infection and from 6 animals in a longitudinal design up to 7 months postinfection to investigate excitatory and inhibitory amino acid neurotransmitter levels. During the early infection period CSF amino acid concentrations of infected animals were not significantly different from those of uninfected animals. However, long-term studies demonstrated that gamma-aminobutyric acid (GABA) concentrations were decreased while glutamate concentrations were increased late in infection compared with the preinfection values of the same animals. Moreover, we showed that the source of increased glutamate in animals with AIDS is, at least partially, Microglial cells. Our data support the hypothesis that excitotoxicity is involved in immunodeficiency virus-induced neurological disease and propose Microglia as a contributor to excitotoxic damage

133. McArthur JC, Sacktor N, Selnes O (1999) Human immunodeficiency virus-associated dementia. Semin.Neurol. 19:129-150
     Abstract: HIV-associated dementia will eventually develop in 15-20% of individuals with advanced HIV disease. It has become one of the leading causes of dementia in the young, with 10,000 new cases annually in the USA. The clinical syndrome includes progressive development of psychomotor slowing and memory impairment, eventually with brain atrophy and neurol loss. The pathology is characterized by infection of macrophages and Microglia, marked activation of macrophages, and release of a variety of postinflammatory cytokines into the parenchyma. Antiretroviral therapy has impacted positively on the incidence rates, and at least partial reversal of neurologic deficits can be achieved in established dementias

134. Mengozzi M, De Filippi C, Transidico P, Biswas P, Cota M, Ghezzi S, Vicenzi E, Mantovani A, Sozzani S, Poli G (1999) Human immunodeficiency virus replication induces monocyte chemotactic protein-1 in human macrophages and U937 promonocytic cells. Blood 93:1851-1857
     Abstract: We have recently described a significant correlation between human immunodeficiency virus-1 (HIV-1) RNA replication and monocyte chemotactic protein-1 (MCP-1) levels in the cerebrospinal fluid (CSF) of individuals with the acquired immunodeficiency syndrome (AIDS) with HIV encephalitis (E). Because local macrophages (Microglia) are the cells predominantly infected in the brain, we investigated whether in vitro HIV infection affects MCP-1 production in mononuclear phagocytes (MP). MCP-1 secretion and expression were consinstently upregulated over constitutive levels in human monocyte-derived macrophages (MDM) infected with the M-tropic R5 BaL strain of HIV-1. HIV replication was required for this effect, as demonstrated by the absence of chemokine upregulation after infection in the presence of 3'-azido-3'-deoxythimidine (AZT) or cell-exposure to heat-inactivated (triangle up degrees ) virus. MCP-1 induction was not restricted to HIV-1 BaL, but was also observed during productive infection of MDM with two primary isolates differing for entry coreceptor usage and of U937 cells with the X4 HIV-1 MN strain. Based on the observation that exogenous HIV-1 Tat induced MCP-1 expression in astrocytes, we also investigated its role in MDM and U937 cells. Exogenous Tat induced MCP-1 production from MDM in a concentration-dependent manner, however, it was not effective on uninfected U937 cells or on the chronically infected U937-derived cell line U1. Transfection of Tat-expressing plasmids moderately activated HIV expression in U1 cells, but failed to induce MCP-1 expression in this cell line or in uninfected U937 cells. HIV replication-dependent expression of MCP-1 in MP may be of particular relevance for the pathogenesis of HIV infection in nonlymphoid organs such as the brain

135. Miller RJ, Meucci O (1999) AIDS and the brain: is there a chemokine connection? Trends Neurosci. 22:471-479
     Abstract: Many HIV-1-positive individuals suffer from a variety of neurological problems known collectively as the HIV-1-related cognitive-motor complex. However, the molecular mechanisms that underlie HIV-1-induced neuropathology are unclear. They might include a combination of indirect effects, which result from the release of neurotoxins from activated astrocytes and Microglia, and the direct effects of HIV-1-related proteins, such as gp120, on neurons. As the interaction of gp120 with immune cells has been shown to require the participation of chemokine receptors, this article explores the possibility that such receptors participate in the events underlying HIV-1-induced neuropathology. It is now clear that many types of cell in the brain possess chemokine receptors, including Microglia, glia and neurons, and the interaction of gp120 with neuronal chemokine receptors initiates apoptotic death of neurons in vitro. Such effects might be modified by the actions of chemokines that act at these same receptors. However, the importance of this direct interaction with neurons in vivo and its relevance in the pathogenesis of AIDS-related dementia still needs to be established. Furthermore, the existence of chemokine receptors on neurons suggests that chemokines might regulate neuronal functions physiologically

136. Nath A (1999) Pathobiology of human immunodeficiency virus dementia. Semin.Neurol. 19:113-127
     Abstract: The pathobiology of dementia that accompanies infection with the human immunodeficiency virus involves complex interactions of the virus with the host. The virus enters the brain either as free viral particles or hidden in infected monocytes (the "Trojan Horse" mechanism). Within the brain it infects Microglial cells, causing a productive and cytopathic infection, and infects astrocytes, causing a latent or restricted infection. The brain thus acts as an important reservoir for the virus. These infected cells release several viral proteins, some of which are toxic to neurons and are called "virotoxins." These virotoxins activate glial cells to release a number of soluble factors that are either toxic to neurons or cause chemotaxis of monocytes into the brain. Because the glial cells outnumber the neurons by 10:1, this is an important mechanism by which the virotoxins amplify their toxic potential and initiate a self-perpetuating cascade of events, resulting in a "domino effect" on the brain. Only a transient exposure to virotoxins is necessary to initiate these positive feedback loops. Thus, a "hit and run" phenomenon may be operative within the brain. Therapeutic approaches are based on decreasing the viral burden in the brain and blocking the actions of the key neurotoxic substances at various levels within the various cascades

137. Persidsky Y (1999) Model systems for studies of leukocyte migration across the blood - brain barrier. J.Neurovirol. 5:579-590
     Abstract: The blood - brain barrier (BBB) plays a crucial role in central nervous system (CNS) homeostasis. Serving as the brain's protective shield it regulates soluble factor and cellular exchanges from blood to brain. Critical to its function, the BBB is composed of brain microvascular endothelial cells (BMVEC), a collagen matrix, and astrocytes. Astrocytic endfeet surround the BMVEC abluminal surface and influence the 'tightness' and trafficking role of the barrier. In neurodegenerative disorders (for example stroke, multiple sclerosis and HIV encephalitis) the BBB becomes compromised. This is, in part, immune mediated. An accumulating body of evidence demonstrates that the cellular components of the BBB are themselves immunocompetent. Perivascular cells (astrocytes, macrophages and Microglial cells) and BMVEC produce inflammatory factors that affect BBB permeability and expression of adhesion molecules. These affect cell trafficking into the CNS. Leukocyte BBB migration can be influenced by cytokines and chemokines produced by glia. Astrocytes and macrophages secrete a multitude of factors that affect brain immune responses. Interactions between BMVEC, leukocytes and/or glia, immunological activation and noxious (infectious, toxic and immune-mediated) brain insults all appear to play important roles in this BBB cell trafficking. New information gained into the mechanisms of leukocyte-brain penetration may provide novel insights in the pathogenesis and treatment strategies of neurodegenerative disorders

138. Peterson PK, Gekker G, Hu S, Lokensgard J, Portoghese PS, Chao CC (1999) Endomorphin-1 potentiates HIV-1 expression in human brain cell cultures: implication of an atypical mu-opioid receptor. Neuropharmacology 38:273-278
     Abstract: Endogneous delta and kappa opioid peptides possess a variety of immunomodulatory properties, and kappa-opioid receptor ligands recently were shown to suppress the expression of human immunodeficiency virus type 1 (HIV-1) in Microglial cells, the resident macrophages of the brain. To determine whether the newly discovered endogenous mu-opioid receptor ligands endomorphin-1 and -2 would affect HIV-1 replication, these peptides were added to acutely infected brain cell cultures. Endomorphin-1 potentiated viral expression, in a bell-shaped dose-response manner with maximal enhancement approximately equal to 35% at 10(-10) M, in both mixed glial/neuronal cell and purified Microglial cell cultures. Endomorphin-1's amplifying effect was blocked by pretreatment of brain cells with either the mu-opioid receptor selective antagonist beta-funaltrexamine or the G protein inhibitor pertussis toxin. However, the classical mu receptor agonists morphine and DAMGO (Tyr-d-Ala-Gly-N-Me-Phe-Gly-ol) had no effect on viral expression or on endomorphin-1's amplifying effect. Taken together, these findings suggest that in this in vitro model of HIV-1 brain infection, endomorphin-1 potentiates viral expression via activation of an atypical mu-selective opioid receptor. They also provide evidence, for the first time, that an endogenous mu-opioid peptide has neuroimmunomodulatory activity

139. Petito CK, Kerza-Kwiatecki AP, Gendelman HE, McCarthy M, Nath A, Podack ER, Shapshak P, Wiley CA (1999) Review: neuronal injury in HIV infection. J.Neurovirol. 5:327-341

140. Saadati HG, Khan IA, Lin XH, Kadakia AB, Heller KB, Sadun AA (1999) Immunolocalization of IL-1beta and IL-6 in optic nerves of patients with AIDS. Curr.Eye Res. 19:264-268
     Abstract: PURPOSE. Immunohistochemical procedures were employed to test the hypothesis that cytokines such as interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) are involved in AIDS-related optic neuropathy and to determine the primary cell types involved. METHODS. Fixed sections of six human HIV-1 infected optic nerves were immunostained for the presence of IL-1beta and IL-6, using horseradish peroxidase and diaminobenzidine as markers. RESULTS. IL-1beta and IL-6 were found in astrocytes, macrophages, Microglia, and endothelial cells. The great majority of astrocytes demonstrated strong immunoreactivity. CONCLUSION. Our findings support the premise that IL-1beta and IL-6 are significant pro-inflammatory mediators in AIDS-related optic neuropathy. This finding supports the theory that HIV infection stimulates the release of IL-1beta and IL-6 in astrocytes, macrophages, and endothelial cells in the optic nerve which ultimately leads to demyelination, astrogliosis, and neuronal destruction

141. Sabri F, Tresoldi E, Di Stefano M, Polo S, Monaco MC, Verani A, Fiore JR, Lusso P, Major E, Chiodi F, Scarlatti G (1999) Nonproductive human immunodeficiency virus type 1 infection of human fetal astrocytes: independence from CD4 and major chemokine receptors. Virology 264:370-384
     Abstract: Human immunodeficiency virus type 1 (HIV-1) infection of the brain is associated with neurological manifestations both in adults and in children. The primary target for HIV-1 infection in the brain is the Microglia, but astrocytes can also be infected. We tested 26 primary HIV-1 isolates for their capacity to infect human fetal astrocytes in culture. Eight of these isolates, independent of their biological phenotype and chemokine receptor usage, were able to infect astrocytes. Although no sustained viral replication could be demonstrated, the virus was recovered by coculture with receptive cells such as macrophages or on stimulation with interleukin-1beta. To gain knowledge into the molecular events that regulate attachment and penetration of HIV-1 in astrocytes, we investigated the expression of several chemokine receptors. Fluorocytometry and calcium-mobilization assay did not provide evidence of expression of any of the major HIV-1 coreceptors, including CXCR4, CCR5, CCR3, and CCR2b, as well as the CD4 molecule on the cell surface of human fetal astrocytes. However, mRNA transcripts for CXCR4, CCR5, Bonzo/STRL33/TYMSTR, and APJ were detected by RT-PCR. Furthermore, infection of astrocytes by HIV-1 isolates with different chemokine receptor usage was not inhibited by the chemokines SDF-1beta, RANTES, MIP-1beta, or MCP-1 or by antibodies directed against the third variable region or the CD4 binding site of gp120. These data show that astrocytes can be infected by primary HIV-1 isolates via a mechanism independent of CD4 or major chemokine receptors. Furthermore, astrocytes are potential carriers of latent HIV-1 and on activation may be implicated in spreading the infection to other neighbouring cells, such as Microglia or macrophages

142. Starling I, Wright A, Arbuthnott G, Harkiss G (1999) Acute in vivo neurotoxicity of peptides from Maedi Visna virus transactivating protein Tat. Brain Res. 830:285-291
     Abstract: Lentiviruses such as Maedi Visna virus (MVV) in sheep, and human immunodeficiency virus (HIV) in man often cause a variety of neurological syndromes in later stages of infection. Neuropathological investigations reveal damage to myelin and astrocytosis in both white and grey matter. MVV infection induces axonal damage with some areas of necrosis while neuronal loss, and synaptic damage have been reported in HIV-1 infection. It is not clear, at present, how this neurodegeneration is mediated but, as these viruses do not directly infect neurons, an indirect neurotoxic action of the viruses is indicated. Previous experiments have shown that the intra-striatal injection in rats of a synthetic peptide derived from the basic region of the MVV transactivating protein Tat causes considerable neurotoxicity 1 week post-operatively. By in vivo stereotaxic injections of the same synthetic peptide, and subsequent immunocytochemical detection of neurons, astrocytes and Microglia, we show that this neurotoxicity displays a distinctive and unusual lesion profile and is evident as rapidly as 0.5 h post-operatively. Furthermore, neuroprotection studies suggest that the early effects of the MVV tat peptide may involve glutamate neurotoxicity via the N-methyl-D-aspartate (NMDA) receptors since the application of dizolcipine (MK801) reduces the volume of the lesion seen at 1 h after the injection of neurotoxic peptide, while L-NAME is ineffective. The mechanism of this early neurotoxicity is thus different from the longer term actions already described

143. Swindells S, Zheng J, Gendelman HE (1999) HIV-associated dementia: new insights into disease pathogenesis and therapeutic interventions. AIDS Patient.Care STDS. 13:153-163
     Abstract: Remarkable progress was made in recent years in the therapeutics of HIV-1-associated dementia (HAD) and in unraveling the complex pathophysiology that follows viral invasion of the central nervous system (CNS). Viral replication in and outside of the CNS was significantly reduced in HIV-1 infected subjects by new potent antiretroviral therapies. This has resulted in partial repair of cellular immune function with improvement in, and the prevention of, neurologic deficits associated with progressive HIV-1 disease. In regard to HAD pathophysiology, it is now known that CNS damage induced by HIV-1 infection occurs indirectly. Neuronal loss is mediated through immune activation and viral infection of mononuclear phagocytes (MPs) (brain macrophages and Microglia). Cellular and viral factors secreted by brain MPs produce, over time, neuronal damage and drop out. Viral growth in the brain appears necessary, but not sufficient, to produce cognitive and motor impairments in affected individuals. Indeed, the best predictor for neurologic impairment following HIV-1 infection is the absolute number of immune-competent macrophages; not the level of viral production in affected brain tissue. As yet, an understanding of macrophage-related neurodegeneration has not translated into significant improvements in the treatment of this devastating complication of HIV disease. Nonetheless, adjunctive antiinflammatory and neuroprotective therapies are being developed. New ideas regarding HAD neuropathogenesis, and implications for the diagnosis and treatment of HAD are summarized in this article

144. Tomlinson GS, Simmonds P, Busuttil A, Chiswick A, Bell JE (1999) Upregulation of Microglia in drug users with and without pre-symptomatic HIV infection. Neuropathol.Appl.Neurobiol. 25:369-379
     Abstract: It is generally thought that infection of the central nervous system (CNS) by HIV-1 can occur early, even around the time of seroconversion, and evidence from animal studies supports this. However, the mode and timing of viral entry remain poorly understood since there have been comparatively few studies of the early neuropathology of HIV infection. In this study, samples of frontal and temporal lobes, and basal ganglia, were selected from 12 HIV-positive drug users who had been infected for 4-130 months before death, 10 HIV-negative drug users and 10 non-drug using controls, all age and sex matched. Routine and immunocytochemical staining showed that leptomeningeal and perivascular lymphocytic infiltrate was upregulated in HIV-infected cases compared with the two control groups, and choroid plexitis was confined to the HIV-positive subjects, suggesting an association with viral infection. In contrast, CD68-positive Microglia were enhanced in both HIV- positive and HIV-negative drug users, considerably above the baseline seen in normal controls. However, there was no statistical difference between the three groups in relation to astrocytes. Screening and competitive polymerase chain reaction (PCR) undertaken on multiple samples including brain tissue, choroid plexus and leptomeninges from four of the HIV-positive subjects and one control case showed that the pro-viral burden was never more than 13 copies/microg DNA and was negative in multiple samples from one HIV-positive case and one control case. All the basal ganglia samples were PCR-negative. This study has not revealed any t spots' of viral load in brain tissue, choroid plexus or meninges, either early or late in the course of pre-symptomatic HIV infection. Drug use alone is associated with significant upregulation of Microglia and this may predispose to HIV infection of the nervous system in drug users

145. Vincent VA, De Groot CJ, Lucassen PJ, Portegies P, Troost D, Tilders FJ, Van Dam AM (1999) Nitric oxide synthase expression and apoptotic cell death in brains of AIDS and AIDS dementia patients. AIDS 13:317-326
     Abstract: OBJECTIVES: To determine the occurrence and cellular localization of inducible nitric oxide synthase (iNOS), NOS activity and its association with cell death in brains of AIDS and AIDS dementia complex (ADC) patients. DESIGN AND METHODS: Post-mortem cerebral cortex tissue of eight AIDS patients, eight ADC patients and eight control subjects was processed for iNOS immunocytochemistry, NADPH-diaphorase activity staining as an index of NOS activity, and in situ end-labelling to detect cell death. RESULTS: iNOS-positive cells were present in the white matter of 14 out of 16 AIDS and ADC patients, whereas two out of eight control subjects showed iNOS-positive cells. iNOS immunoreactivity was exclusively localized in activated macrophages and Microglial cells that both showed NADPH-diaphorase activity. In addition, NADPH-diaphorase activity, not related to iNOS immunoreactivity, was observed in astrocytes in both white and grey matter of AIDS and ADC patients. All AIDS and ADC patients, and only one control subject showed characteristic features of apoptotic cell death. CONCLUSIONS: Different forms of NOS are present in Microglial cells and astrocytes of AIDS and ADC patients but are largely absent in control subjects. Although more NOS-expressing cells occur in ADC than in AIDS patients, apoptotic cell death was found in both patient groups to the same extent. We postulate that NO production in brains of AIDS patients results in cumulative cortical cell loss, which becomes neurologically evident at later stages of disease and is expressed as ADC

146. Wiley CA, Achim CL, Christopherson C, Kidane Y, Kwok S, Masliah E, Mellors J, Radhakrishnan L, Wang G, Soontornniyomkij V (1999) HIV mediates a productive infection of the brain. AIDS 13:2055-2059
     Abstract: BACKGROUND: Approximately one quarter of patients with AIDS develop severe cognitive deficits called HIV-associated dementia complex. There is some controversy regarding the importance of viral load and distribution in mediating this neurologic disease. OBJECTIVE: Brain HIV proviral and RNA loads were compared to define the molecular nature of HIV infection of the brain. METHOD: Neuropathologic examination was performed on brains from 10 autopsies of patients with AIDS that had short post-mortem intervals and no evidence of opportunistic infection. Viral DNA and RNA were extracted and quantified from multiple brain regions. These findings were compared with triple-label immunofluorescence for viral and cell markers. RESULTS: Brains with histopathologic evidence of HIV encephalitis contained abundant HIV RNA and DNA. Regions without productive HIV infection showed minimal proviral load. By immunocytochemistry, only brain macrophages/Microglia double labeled for viral proteins. CONCLUSIONS: HIV mediates a productive infection of brain macrophages/Microglia. There was no evidence supporting the hypothesis of substantial neuronal or macroglial infection, or evidence of substantial proviral burden prior to the development of productive infection

147. Xiong H, Zheng J, Thylin M, Gendelman HE (1999) Unraveling the mechanisms of neurotoxicity in HIV type 1-associated dementia: inhibition of neuronal synaptic transmission by macrophage secretory products. AIDS Res.Hum.Retroviruses 15:57-63
     Abstract: The cognitive and motor impairments of HIV-1-associated dementia (HAD) often result from neuronal damage of drop-out. In the infected human host, virus-infected immune-competent mononuclear phagocytes (MPs) (brain macrophages and Microglia) are the target cells for HIV-1 and the producers of bioactive molecules that mediate neural damage. Indeed, in laboratory experiments, activated HIV-1-infected macrophages placed into human or rodent brain tissues induce neuronal apoptosis. Nonetheless, the mechanisms for neuronal dysfunction in HAD have yet to be discerned. To these ends, we studied the effects of HIV-1-infected monocyte-derived macrophage (MDM) secretions, electrophysiologically, on neuronal synaptic transmission. Bath application of HIV-1-infected MDM culture fluids onto rat hippocampal brain slices resulted in inhibition of evoked field excitatory postsynaptic potentials (EPSPs). In contrast, fluids from uninfected MDMs showed mild effects on the EPSPs. HIV-1-associated inhibition of EPSPs was enhanced by LPS activation, both for HIV-1-infected and uninfected MDMs. Importantly, paired-pulse facilitation ratio tests showed that factors secreted by HIV-1-infected MDMs acted transiently on presynaptic terminals, providing insights into the site of action and mechanism of the MDM-induced neuronal dysfunction. These results, taken together, demonstrate that factors produced as a consequence of MDM infection and activation affect neuronal synaptic transmission

148. Zink WE, Zheng J, Persidsky Y, Poluektova L, Gendelman HE (1999) The neuropathogenesis of HIV-1 infection. FEMS Immunol.Med.Microbiol. 26:233-241
     Abstract: HIV encephalitis is the common pathologic correlate of HIV-dementia (HAD). HIV-infected brain mononuclear phagocytes (MP) (macrophages and Microglia) are reservoirs for persistent viral infection. When activated, MP contribute to neuronal damage. Such activated and virus-infected macrophages secrete cellular and viral factors, triggering neural destructive immune responses. Our Center's laboratories have begun to decipher the molecular and biochemical pathways for MP-mediated neuronal damage in HAD. This review will discuss the salient clinical and pathological features of HAD and highlight the recent advances made, by our scientists and elsewhere, in unraveling disease mechanisms, including the role of chemokines and their receptors in the neuropathogenesis of HIV-1 encephalitis

149. Andersson LM, Fredman P, Lekman A, Rosengren L, Gisslen M (1998) Increased cerebrospinal fluid ganglioside GD3 concentrations as a marker of Microglial activation in HIV type 1 infection. AIDS Res.Hum.Retroviruses 14:1065-1069
     Abstract: Human immunodeficiency virus type 1 (HIV-1) invades the central nervous system (CNS) early in the infectious course. The predominant, productively infected cell type within the CNS is the Microglial cell. We have analyzed the cerebrospinal fluid (CSF) levels of the ganglioside GD3, a Microglia/macrophage and astrocyte marker, in 22 HIV-1-infected individuals at different stages of the disease, and in 44 age-matched HIV-negative, healthy controls. To distinguish between Microglial/macrophage and astroglial involvement, the GD3 levels were compared with CSF levels of the glial fibrillary acidic protein (GFAp), which is expressed exclusively in astrocytes. A significantly higher mean CSF concentration of GD3 was found in HIV-1-infected patients compared to controls (56.7 and 40.1 nmol/L, respectively, p < 0.001). Seven of 22 HIV-1-infected patients had increased CSF levels of GD3 (above mean + 2 SD in controls), all but one of these had normal levels of GFAp, indicating a Microglial activation or proliferation as the major source of the increased GD3 levels

150. Avgeropoulos N, Kelley B, Middaugh L, Arrigo S, Persidsky Y, Gendelman HE, Tyor WR (1998) SCID mice with HIV encephalitis develop behavioral abnormalities. J.Acquir.Immune.Defic.Syndr.Hum.Retrovirol. 18:13-20
     Abstract: Severe combined immunodeficient (SCID) mice inoculated intracerebrally (i.c.) with HIV-infected human monocytes develop brain pathology similar to that in humans with HIV encephalitis. This includes HIV-positive macrophages and multinucleated giant cells, astrogliosis, Microglial nodules, and neuronal dropout. These xenografts survive about 1 month. To develop a model of chronic HIV encephalitis and to assay the resulting behavioral abnormalities, we reinoculated SCID mice i.c. every 4 weeks for 3 months with either HIV-infected human monocytes (n = 5) or uninfected human macrophages (n = 4) or administered no inoculation (n = 6); these three groups were monitored for behavioral abnormalities. Tests of cognitive function in a Morris water maze 3.5 months after the first inoculation suggested that HIV-infected mice performed poorly compared with controls. Following testing in the water maze on days 4 and 5 of acquisition, motor activity of infected mice was reduced in comparison with that of controls. Retention of goal location when tested 1 week later was impaired in HIV-infected mice compared with controls. Histopathologic analysis of brains revealed significant astrogliosis and strongly suggested higher numbers of major histocompatibility complex (MHC) class II-positive multinucleated macrophages in HIV-infected compared with control mice. Thus, our preliminary studies indicate that SCID mice with HIV encephalitis develop behavioral abnormalities reminiscent of human disease. These behavioral abnormalities are associated with significantly increased astrogliosis, the presence of HIV, and probably multinucleated giant cells. These studies further support the use of this SCID animal model system for studies of the pathogenesis of HIV encephalitis and for drug interventions

151. Bell JE (1998) The neuropathology of adult HIV infection. Rev.Neurol.(Paris) 154:816-829
     Abstract: Since the onset of the acquired immune deficiency syndrome (AIDS) epidemic fifteen years ago, much has been learned about the effects of the human immunodeficiency virus (HIV) in the nervous system. This review summarizes the pathology findings in the central nervous system (CNS). There is now abundant evidence that HIV can infect the CNS directly, leading to a characteristic HIV encephalitis (HIVE) which occurs in 10-50 p. 100 of AIDS autopsy series. Multinucleated giant cells are the pathognomonic feature of HIVE and are found predominantly in the central white matter and deep grey matter. Evidence of productive HIV infection in the CNS is confined to cells of the Microglial/macrophage lineage, from which the giant cells are almost certainly derived. These cells are known to express both CD4 and beta-chemokine receptors, which act in conjunction to permit HIV entry. Restricted infection of astrocytes has also been identified by a variety of methods. HIVE is frequently associated with white matter damage ranging from inflammatory (Microglia, macrophages and sparse lymphocytes) to degenerative (myelin loss and axonal damage) pathology. Although giant cells are seen less frequently in neocortical grey matter, significant neuronal loss has been established in a number of studies. Recent investigations using markers of apoptosis, (including TUNEL, Bcl-2 and BAX), have established the presence of DNA damage in some neurons and in other cell types. Axonal damage has also been confirmed by evidence of amyloid precursor protein expression. The CNS is also vulnerable to opportunistic infections and high grade B-cell lymphomas as a result of the immune suppression of advanced HIV infection. Cytomegalovirus (CMV) infection is reported in 10-30 p. 100 of AIDS cases at autopsy, toxoplasma in 10-25 p. 100, progressive multifocal leucoencephalopathy in about 5 p. 100 and lymphomas, usually primary, in up to 10 p. 100. A wide variety of other infections has also been reported. These may coexist with HIVE and may be difficult to diagnose in life. CMV gives rise to Microglial nodular encephalitis, ventriculitis, necrotising encephalitis and myelo-radiculitis. Presymptomatic HIV positive patients do not show HIVE or opportunistic infections or lymphomas in the CNS. They frequently display a low-grade T-cell infiltrate in the leptomeninges and parenchyma, particularly around vessels. This lymphocytic infiltrate has been attributed to presumed early invasion of the CNS by HIV although the exact timing of entry is uncertain. It is possible that reported abnormalities in presymptomatic cases such as gliosis, Microglial activation and rising proviral load may anticipate the onset of HIVE but most studies show that significant CNS damage and HIV-related pathology is confined to patients with AIDS. HIV-related pathology in the spinal cord includes not only HIV myelitis, opportunistic infections and lymphomas, but also vacuolar myelopathy (VM) which affects predominantly the dorsolateral white matter tracts. The cause of VM is not understood and has not been unequivocally linked with HIV infection. It is noted that none of these neuropathological features (including HIVE) correlates exactly with the clinical expression of AIDS-related dementia (ARD). The exact contribution of macrophage activation and cytokine release, astrocytic infection, neuronal loss and axonal damage to the neuropsychiatric syndromes of advanced HIV infection remain to be determined. While the current understanding of the pathogenesis of HIVE and ARD is beyond the scope of this review it is axiomatic that accurate documentation of neuropathology findings will help to resolve the outstanding dilemmas relating to HIV infection of the CNS. There is considerable optimism that progress in therapeutic regimes for HIV-infected patients will succeed in eliminating the virus from the blood and from lymphoid tissue. (ABSTRACT TRUNCATED)

152. Bell JE, Brettle RP, Chiswick A, Simmonds P (1998) HIV encephalitis, proviral load and dementia in drug users and homosexuals with AIDS. Effect of neocortical involvement. Brain 121 ( Pt 11):2043-2052
     Abstract: In this consecutive autopsy study, the pathological evidence of HIV encephalitis, which included the presence of giant cells and/or HIV p24 immunopositivity, was found more frequently in drug users (25 of 45; 56%) than in homosexual men (6 of 35; 17%) with AIDS (P < 0.01). Productive infection, as shown by HIV p24 positivity, was found in frontal lobe white matter in 29 of the 31 HIV encephalitis cases, but was also present in grey matter in 50% of the HIV encephalitis cases. Immunopositivity was confined to Microglia, monocytes and most but not all giant cells. HIV-1 proviral load was determined by quantitative PCR in 65 of the 80 cases (separately in grey and white matter in 49 of these), and correlated well with the presence of HIV encephalitis (P < 0.001). Twenty-five patients with AIDS (13 male homosexuals, 12 drug users) showed no HIV encephalitis, opportunistic infection or cerebral lymphoma, while 18 (2 male homosexuals, 16 drug users) showed pure HIV encephalitis. Cognitive function had been assessed prospectively in this cohort and graded as normal or mildly, moderately or severely impaired. Because opportunistic infections and lymphomas of the brain may also lead to dementia, patients found to have these conditions at autopsy were excluded from the final analysis of the cases with dementia, so that the precise correlation between cognitive impairment and pure HIV encephalitis could be determined in this cohort without possible confounding variables. Fourteen of 18 patients with pure HIV encephalitis had shown cognitive impairment. Severe dementia correlated better with pure HIV encephalitis in cases in which grey matter involvement was present (7 out of 9) than in those in which only white matter was involved (2 out of 9) (P < 0.05), although milder degrees of cognitive impairment had been present in a further 5 HIV encephalitis cases. No correlation was found between zidovudine therapy and the degree of cognitive impairment. Systemic and cerebral opportunistic infections and lymphoma showed a negative association with HIV encephalitis, being more common in homosexuals than in drug users, despite comparable CD4 counts in the two groups. These findings suggest that neocortical productive HIV infection is a significant factor in AIDS-related dementia, although this may reflect merely a higher overall viral burden in the brain

153. Bertrand E, Lewandowska E, Nerurkar V, Bratosiewicz J, Yanagihara R, Zaborski J, Liberski PP (1998) Progressive multifocal leukoencephalopathy (PML) and cerebral toxoplasmosis in an adult patient, with no symptoms of underlying immunosuppressing illness. Folia Neuropathol. 36:229-234
     Abstract: We present a case of the coincidence of progressive multifocal leukoencephalopathy (PML) and central nervous system (CNS) toxoplasmosis in an adult patient, without a detectable cause of cell-mediated immunity impairment. The proper diagnosis was made postmortem on the basis of histological changes typical of both pathological processes. PML was characterized by the presence of subcortical focal demyelination, containing enlarged, densely basophilic oligodendrocyte nuclei, often with intranuclear inclusion, and bizarre astrocytes, mimicking neoplastic cells. PML was confirmed by detecting numerous papova virus particles in oligo- and astroglial nuclei by thin-section electron microscopy. Cerebral toxoplasmosis was characterized by the presence of multiple well-circumscribed necrotizing abscesses. Numerous Toxoplasma gondii (T. gondii) cysts and free, non-encysted protozoan parasites were found among the inflammatory infiltrates. The diagnosis of cerebral toxoplasmosis was further confirmed by immunocytochemistry. In order to detect putative immunosuppressive background underlying both pathological processes, HIV infection was taken into consideration, however, no histopathological changes indicative of AIDS either in the CNS or in the peripheral organs were eventually found. Moreover no HIV provirus genome was identified in the formalin-fixed, paraffin embedded brain tissue by the polymerase chain reaction (PCR). Current view on the selected aspects of the pathogenesis of both disorders were discussed

154. Bjugstad KB, Flitter WD, Garland WA, Su GC, Arendash GW (1998) Preventive actions of a synthetic antioxidant in a novel animal model of AIDS dementia. Brain Res. 795:349-357
     Abstract: Accumulating evidence indicates that the mechanism for causing AIDS dementia complex (ADC) involves the release of damaging inflammatory-related agents by HIV-infected Microglia in the brain resulting in CNS oxidative damage. One such agent, tumor necrosis factor alpha (TNF-alpha) is consistently elevated in the brains of ADC patients compared to non-demented HIV patients. To model this aspect of ADC in rats, chronic ventricular infusions of TNF-alpha were given and found to induce several aspects of ADC, including weight loss, learning/memory impairment, enlarged lateral ventricles, and increased apoptosis. Concurrent oral treatment with the antioxidant CPI-1189 prevented all of these TNF-alpha induced effects. The results support TNF-alpha as a key toxic agent in ADC and provide the first in vivo evidence that chronic treatment with a synthetic antioxidant may protect HIV-infected patients against ADC. Our findings may also have implications in other neurological diseases where brain TNF-alpha levels are elevated and inflammation/oxidative stress is suspected to be a contributing cause, such as Alzheimer's disease and Parkinson's disease

155. Buttini M, Westland CE, Masliah E, Yafeh AM, Wyss-Coray T, Mucke L (1998) Novel role of human CD4 molecule identified in neurodegeneration. Nat.Med. 4:441-446
     Abstract: The human CD4 molecule (hCD4) is expressed on T lymphocytes and macrophages and acts as a key component of the cellular receptor for HIV. At baseline, hCD4 transgenic mice expressed hCD4 on Microglia, the resident mononuclear phagocytes of the brain, and showed no neuronal damage. Activation of brain Microglia by peripheral immune challenges elicited neurodegeneration in hCD4 mice but not in nontransgenic controls. In post-mortem brain tissues from AIDS patients with opportunistic infections, but without typical HIV encephalitis, hCD4 expression correlated with neurodegeneration. We conclude that hCD4 may function as an important mediator of indirect neuronal damage in infectious and immune-mediated diseases of the central nervous system

156. Cinque P, Vago L, Mengozzi M, Torri V, Ceresa D, Vicenzi E, Transidico P, Vagani A, Sozzani S, Mantovani A, Lazzarin A, Poli G (1998) Elevated cerebrospinal fluid levels of monocyte chemotactic protein-1 correlate with HIV-1 encephalitis and local viral replication. AIDS 12:1327-1332
     Abstract: OBJECTIVE: To investigate whether the CC-chemokine monocyte chemotactic protein (MCP)-1 could play a role in the pathogenesis of HIV infection of the central nervous system. This hypothesis was suggested by previous observations, including our finding of elevated cerebrospinal fluid (CSF) levels of this chemokine in patients with cytomegalovirus (CMV) encephalitis. DESIGN AND METHODS: CSF levels of MCP-1 were determined in 37 HIV-infected patients with neurological symptoms, and were compared with both the presence and severity of HIV-1 encephalitis at post-mortem examination and CSF HIV RNA levels. MCP-1 production by monocyte-derived macrophages was tested after in vitro infection of these cells by HIV. RESULTS: CSF MCP-1 levels were significantly higher in patients with (median, 4.99 ng/ml) than in those without (median, 1.72 ng/ml) HIV encephalitis. Elevated CSF MCP-1 concentrations were also found in patients with CMV encephalitis and with concomitant HIV and CMV encephalitis (median, 3.14 and 4.23 ng/ml, respectively). HIV encephalitis was strongly associated with high CSF MCP-1 levels (P = 0.002), which were also correlated to high HIV-1 RNA levels in the CSF (P = 0.007), but not to plasma viraemia. In vitro, productive HIV-1 infection of monocyte-derived macrophages upregulated the secretion of MCP-1. CONCLUSIONS: Taken together, these in vivo and in vitro findings support a model whereby HIV encephalitis is sustained by virus replication in Microglial cells, a process amplified by recruitment of mononuclear cells via HIV-induced MCP-1

157. Corasaniti MT, Bagetta G, Rotiroti D, Nistico G (1998) The HIV envelope protein gp120 in the nervous system: interactions with nitric oxide, interleukin-1beta and nerve growth factor signalling, with pathological implications in vivo and in vitro. Biochem.Pharmacol. 56:153-156
     Abstract: The neuronal loss often described at post-mortem in the brain neocortex of patients suffering from AIDS has been proposed to be responsible for the development of the AIDS dementia complex. Neuroinvasive strains of the HIV virus infect macrophages, Microglial cells, and multinucleated giant cells, but not neurones. Processing of the virus by cells of the myelomonocytic lineage yields viral products known to initiate a complex network of events that may lead to the death of neurones and to the development of AIDS-associated neurological syndrome. The HIV-1 coat protein gp120, in particular, has been proposed as a likely etiologic agent of the described neuronal loss because it causes the death of neurones in culture. More recently, it has been shown that brain cortical cell death caused in rats by intracerebroventricular injection of gp120 occurs via apoptosis. This observation broadens our knowledge of the pathophysiology of the reported neuronal cell loss and opens a new avenue of experimental research for the development of novel therapeutic strategies for the treatment of patients suffering from AIDS-associated neurological syndrome

158. Couraud PO (1998) Infiltration of inflammatory cells through brain endothelium. Pathol.Biol.(Paris) 46:176-180
     Abstract: The blood-brain barrier (BBB) restricts exchanges of soluble factors and cells between the blood and the brain, thus playing a crucial role in maintenance of cerebral homeostasis. It is composed of the endothelial cells that line the cerebral capillaries. Cerebral capillaries have a number of distinctive morphological characteristics, including the presence of tight intercellular junctions. Also, the cerebral capillaries are surrounded by astrocytic projections that exert a positive regulatory effect on BBB tightness. One effect of the BBB is that the number of leukocytes that patrol the central nervous system is far lower than in peripheral organs. Nevertheless, massive leukocyte infiltration occurs in some disease states: for instance, numerous activated leukocytes are found in the cerebral parenchyma in patients with multiple sclerosis, and HIV encephalitis is probably due to passage of HIV-infected monocytes through the BBB. Compelling evidence has been obtained that the perivascular astrocytes and Microglial cells, as well as the cerebral endothelial cells, locally produce inflammatory cytokines that increase BBB permeability. Advances have also been made in the identification of leukocyte adhesion molecules expressed at the surface of cerebral endothelial cells. Expression of these molecules is induced by inflammatory cytokines. Interactions between these adhesion molecules and their leukocyte ligands may induce modifications within endothelial cells, including cytoskeleton reorganization and opening of intercellular junctions, which may allow leukocytes to cross the BBB. It is to be hoped that the new insights gained into the mechanisms of leukocyte penetration through the BBB may help to develop novel treatment strategies for neuroinflammatory disorders

159. Epstein LG (1998) HIV neuropathogenesis and therapeutic strategies. Acta Paediatr.Jpn. 40:107-111
     Abstract: Human immunodeficiency virus (HIV)-1 neuropathogenesis can be divided into three important components: (i) virus entry into the nervous system; (ii) the role of viral proteins and/or cellular products in neural tissue damage; (iii) the mechanisms of neuronal injury/death. Both blood derived macrophages or trafficking HIV-1 infected T-lymphocytes have been implicated in viral entry to the central nervous system (CNS). The major cell type harboring productive HIV-1 infection in the nervous system is the perivascular macrophage/Microglia. The HIV-1 infection of brain astrocytes, restricted to the expression of regulatory gene products, may cause astrocyte dysfunction and contribute to neuronal injury or to disruption of the blood-brain barrier (BBB). Studies of cerebrospinal fluid and postmortem tissues reveal chronic inflammation/immune activation in the nervous system during the later stages of HIV-1 infection associated with disruption of BBB integrity. Blood-brain barrier damage may underlie the white matter pallor described in HIV-1 infection and could result in further entry into the CNS of toxic viral or cellular products, or additional HIV-1 infected cells. The HIV infected and activated macrophages/Microglia produce excessive amounts of pro-inflammatory cytokines, including tumor necrosis factor alpha, and platelet activating factor. These products are directly toxic to human neurons in vitro. The HIV-1 envelope glycoprotein, gp 120 may stimulate the release of toxic factors from brain macrophages. Blocking N-methyl-D-aspartate (NMDA; or AMPA) glutamate receptors can antagonize candidate toxins of both viral and cellular origin. It has been postulated that (weak) excitotoxicity leads to oxidative stress in neurons and ultimately to apoptosis. Neuronal apoptosis occurs in the brains of both children and adults with HIV-1 infection. This understanding of HIV neuropathogenesis implies that therapeutic strategies should include: (i) anti-retroviral medications to decrease systemic and CNS virus load, and possibly to prevent perinatal transmission of HIV; (ii) anti-inflammatory compounds to decrease the chronic immune activation in Microglia and allow the restoration of BBB integrity; and (iii) neuroprotective compounds to reduce neuronal injury and apoptotic death

160. Galasso JM, Harrison JK, Silverstein FS (1998) Excitotoxic brain injury stimulates expression of the chemokine receptor CCR5 in neonatal rats. Am.J.Pathol. 153:1631-1640
     Abstract: Chemokines interact with specific G-protein-coupled receptors to activate and direct recruitment of immune cells. Some chemokines are up-regulated in pathological conditions of the central nervous system, and recently several chemokine receptors, including CCR5, were identified in the brain. However, little is known about the regulation of expression of chemokine receptors in the brain. Direct intracerebral injection of N-methyl-D-aspartate (NMDA), an excitatory amino acid agonist, elicits reproducible focal excitotoxic brain injury; in neonatal rats, intrahippocampal NMDA injection stimulates expression of pro-inflammatory cytokines and elicits a robust Microglia/monocyte response. We hypothesized that NMDA-induced neurotoxicity would also stimulate expression of CCR5 in the neonatal rat brain. We evaluated the impact of intrahippocampal injections of NMDA on CCR5 expression in postnatal day 7 rats. Reverse transcription polymerase chain reaction revealed an increase in hippocampal CCR5 mRNA expression 24 hours after lesioning, and in situ hybridization analysis demonstrated that CCR5 mRNA was expressed in the lesioned hippocampus and adjacent regions. Western blot analysis demonstrated increased CCR5 protein in hippocampal tissue extracts 32 hours after lesioning. Complementary immunocytochemistry studies identified both infiltrating Microglia/monocytes and injured neurons as the principal CCR5-immunoreactive cells. These results provide the first evidence that acute excitotoxic injury regulates CCR5 expression in the developing rat brain

161. Ghorpade A, Xia MQ, Hyman BT, Persidsky Y, Nukuna A, Bock P, Che M, Limoges J, Gendelman HE, Mackay CR (1998) Role of the beta-chemokine receptors CCR3 and CCR5 in human immunodeficiency virus type 1 infection of monocytes and Microglia. J.Virol. 72:3351-3361
     Abstract: Human immunodeficiency virus type 1 (HIV-1) infection in mononuclear phagocyte lineage cells (monocytes, macrophages, and Microglia) is a critical component in the pathogenesis of viral infection. Viral replication in macrophages serves as a reservoir, a site of dissemination, and an instigator for neurological sequelae during HIV-1 disease. Recent studies demonstrated that chemokine receptors are necessary coreceptors for HIV-1 entry which determine viral tropism for different cell types. To investigate the relative contribution of the beta-chemokine receptors CCR3 and CCR5 to viral infection of mononuclear phagocytes we utilized a panel of macrophage-tropic HIV-1 strains (from blood and brain tissue) to infect highly purified populations of monocytes and Microglia. Antibodies to CD4 (OKT4A) abrogated HIV-1 infection. The beta chemokines and antibodies to CCR3 failed to affect viral infection of both macrophage cell types. Antibodies to CCR5 (3A9) prevented monocyte infection but only slowed HIV replication in Microglia. Thus, CCR5, not CCR3, is an essential receptor for HIV-1 infection of monocytes. Microglia express both CCR5 and CCR3, but antibodies to them fail to inhibit viral entry, suggesting the presence of other chemokine receptors for infection of these cells. These studies demonstrate the importance of mononuclear phagocyte heterogeneity in establishing HIV-1 infection and persistence

162. Gold LH, Fox HS, Henriksen SJ, Buchmeier MJ, Weed MR, Taffe MA, Huitron-Resendiz S, Horn TF, Bloom FE (1998) Longitudinal analysis of behavioral, neurophysiological, viral and immunological effects of SIV infection in rhesus monkeys. J.Med.Primatol. 27:104-112
     Abstract: A model is proposed in which a neurovirulent, Microglial-passaged, simian immunodeficiency virus (SIV) is used to produce central nervous system (CNS) pathology and behavioral deficits in rhesus monkeys reminiscent of those seen in humans infected with human immunodeficiency virus (HIV). The time course of disease progression was characterized by using functional measures of cognition and motor skill, as well as neurophysiologic monitoring. Concomitant assessment of immunological and virological parameters illustrated correspondence between impaired behavioral performance and viral pathogenesis. Convergent results were obtained from neuropathological findings indicative of significant CNS disease. In ongoing studies, this SIV model is being used to explore the behavioral sequelae of immunodeficiency virus infection, the viral and host factors leading to neurologic dysfunction, and to begin testing potential therapeutic agents

163. Gray F, Belec L, Chretien F, Dubreuil-Lemaire ML, Ricolfi F, Wingertsmann L, Poron F, Gherardi R (1998) Acute, relapsing brain oedema with diffuse blood-brain barrier alteration and axonal damage in the acquired immunodeficiency syndrome. Neuropathol.Appl.Neurobiol. 24:209-216
     Abstract: A 38-year-old homosexual male with AIDS suffered four neurological episodes including headaches, confusion, visual impairment, memory disturbances, and dysarthria which resolved spontaneously in a few days. He was admitted to hospital during a fifth episode. Neurological examination revealed a cerebellar syndrome. General examination was normal. CD4 count was 90. CSF contained two WBCs/mm(3) and 12.30 mg/dL protein. MRI revealed diffuse ill defined increased signal on T2-weighted images in the white matter. His condition worsened rapidly with vomiting and he died 1 month after admission. Neuropathological examination revealed diffuse brain oedema with ventricular compression, central diencephalic herniation and bilateral tonsilar herniation in the absence of a focal lesion. Microscopical examination revealed predominant involvement of the white matter with diffuse myelin pallor and massive perivascular dilatation containing an exudate expressing serum proteins and occasional macrophages. The same exudate was also diffuse in the leptomeninges. Parenchymal damage predominated around the perivascular spaces and included loosening of tissue, axonal damage with spheroids and reactive astrocytosis. There was no evidence of productive HIV encephalitis, no multinucleated giant cells; p24 immunostaining and RT-PCR for HIV genome were negative. There was neither significant inflammation nor Microglial activation. In this illustrative case, the relapsing course of the neurological signs, the diffuse topography of the blood-brain barrier breakdown and the absence of local cause make it likely that the diffuse leak and axonal damage could be related to circulating factors

164. Gray F (1998) [Dementia and human inmmunodeficiency virus infection]. Rev.Neurol.(Paris) 154 Suppl 2:S91-S98
     Abstract: HIV-associated neurological manifestations: dementia, myelopathy, and neuropathy, have become one of the commonest causes of neurological disorders in young people. Cognitive impairment develops in about 30 p. 100 of patients with AIDS and frank dementia in 15 to 20 p. 100 with an annual incidence after AIDS of approximatively 7 p. 100. Typically, the onset of dementia is relatively abrupt over a few weeks or months. The clinical manifestations of the encephalopathy now termed "HIV-dementia", suggest predominant subcortical or frontal involvement. Typical presentation includes apathy and inertia, memory loss and cognitive slowing, minor depressive symptoms and withdrawal from usual activities. Neurological examination may show hypertonia of lower limbs, tremor, clonus, frontal release signs and hyperactive reflexes. Terminally, the patient is bedbound, incontinent, abulic or mute with decorticate posturing leading to death over 3 to 6 months. However, a stabilisation and even a regression of the cognitive disorders have been observed following antiretroviral treatment. Radiological features of HIV dementia include both central and cortical atrophy and white matter rarefaction. However they are neither invariable nor specific. Together with CSF examination, they are more important to exclude opportunistic infections. Indeed, although a completely normal CSF profile may reasonably exclude the diagnosis; at present, no single test or combination of tests can reliably diagnose HIV dementia. Although the clinical characteristics of HIV-dementia are now clearly established, its pathogenesis is unclear and its pathological counterpart remains a matter of debate. A number of "HIV-induced" lesions may be found in the brain of AIDS patients and their causative role in HIV-dementia has been considered. They include HIV encephalitis due to productive CNS infection by the virus, diffuse white matter pallor "HIV-leukoencephalopathy" reflecting an abnormality of the blood brain barrier, involvement of the grey matter, "diffuse poliodystrophy", with neuronal loss that results, at least partly, from a process of programmed cell death and axonal damage. These changes are variably associated in patients with HIV dementia, however none of them can be closely related to the cognitive disorders. This suggests that the neuronal dysfunction underlying HIV-dementia results from different mechanisms that are variably associated and may interact mutually. These include production of viral proteins, Microglial activation with consequent production of neurotoxic factors such as proinflammatory cytokines, free radicals, derivates of arachidonic acid, or quinoleic acid, and blood borne neurotoxic factors in particular cytokines

165. Janabi N, Di Stefano M, Wallon C, Hery C, Chiodi F, Tardieu M (1998) Induction of human immunodeficiency virus type 1 replication in human glial cells after proinflammatory cytokines stimulation: effect of IFNgamma, IL1beta, and TNFalpha on differentiation and chemokine production in glial cells. Glia 23:304-315
     Abstract: Although evidence for human immunodeficiency virus 1 (HIV-1) presence in the central nervous system (CNS) of infected patients is well established, the intensity of viral replication within the brain is not usually known. In vitro, human embryonic Microglial cells internalized HIV-1 through a CD4-dependent pathway but were not permissive to viral replication. We observed that HIV replication was induced when CNS cell cultures were stimulated for 14 days by a combination of proinflammatory cytokines including IFNgamma, IL1beta, and TNFalpha. After long-term cytokine stimulation, morphologically differentiated glial cells appeared, in which HIV-1 tat antigen was detected after infection. Thus, variations in the stage of maturation/activation of CNS cells under inflammatory conditions probably play a major role in facilitating massive production of HIV-1. We then studied the effect of prolonged cytokine stimulation on the secretion of inflammatory mediators by glial cells. An early increased secretion of prostaglandin F2alpha and chemokines (RANTES>>MIP-1alpha>>MIP-1beta) was observed, due to both Microglia and astrocytes. In contrast to persistent PGF2alpha production, an extinction of RANTES and MIP-1beta but not of MIP-1alpha secretion occurred during the 14 days of stimulation and was inversely correlated with the ability of glial cells to replicate HIV-1. The study of the secretory factors produced in response to a persistent inflammation could provide a better understanding of the modulation of HIV replication in glial cells

166. Kolson DL, Lavi E, Gonzalez-Scarano F (1998) The effects of human immunodeficiency virus in the central nervous system. Adv.Virus Res. 50:1-47
     Abstract: More than a decade after the first description of HIV DNA in the nervous system the pathophysiology of HIVD remains largely enigmatic, with data supporting a number of potential mechanisms for the development of neuronal dysfunction. Nevertheless, a few key findings have considerable support in the literature devoted to this subject: 1. HIV dementia is caused by HIV itself; no other pathogen has been consistently found in the brains of patients with HIVD. 2. In comparison with other viral encephalopathies, there appears to be a significant discordance between the amount of virus being produced in the brains of patients with HIVD and the degree of neurological deterioration. 3. The key cell types responsible for viral production within the CNS are the resident macrophages or Microglial cells. 4. Other elements within the CNS, particularly astrocytes, are probably infected with HIV as well, but all of these infections are highly restricted in terms of production of virus or viral structural proteins. 5. At least one component of the pathogenesis of HIVD may be the generation of neurotoxins by infected Microglia, although the type of neurotoxin, and the specific compound most likely to be involved, are quite controversial. Advances with combination antiviral therapy have successfully reduced plasma viral load in a high proportion of individuals, leading to the speculation (previously almost heretical) that it may be possible to eradicate HIV completely from the systemic immune system. If that were the case, potential "sanctuary" sites such as the immunologically protected CNS might remain as important reservoirs for reseeding of lymphoid tissues. Microglia may be particularly suited for this purpose because they are long lived, can produce HIV for several weeks (at least in culture), and they are apparently relatively immune to virus-induced cytopathology such as syncytium formation. One can speculate about several scenarios resulting from the continued presence of replication-competent HIV within brain. In the worst case, a smoldering infection of the nervous system could lead to neurological deterioration without reinfection of systemic immune cells. The epidemiological data indicating that HIVD is a disease primarily associated with immunodeficiency suggest that the systemic immune system plays a role in maintaining virus residing within the CNS under control. Thus it is quite possible that this scenario would not occur for many years after the systemic infection is controlled. Alternatively, virus could be transported from the CNS by circulating lymphocytes and monocytes and reinfect systemic organs. This would necessitate restarting therapy for those individuals who were previously thought to be cured, but presumably virus within the CNS would not have developed resistance to antivirals. In either case, the techniques currently available do not permit an accurate assessment of CNS HIV load in living people, and this question will remain unanswered until antivirals are discontinued in a few individuals with persistently negative tests for systemic virus. In addition to this most critical question, the relationship between viral levels and HIVD is largely unexplored, as is the possibility that some strains are particularly virulent or neuroinvasive. Furthermore, the potential contribution of host genotype in the development of dementia is unknown. In view of the strong influence of major chemokine receptor (CCR5) truncations on HIV replication, it is entirely possible that more discrete genetic polymorphisms have a subtle effect on either brain invasion or virulence

167. Lanjewar DN, Jain PP, Shetty CR (1998) Profile of central nervous system pathology in patients with AIDS: an autopsy study from India. AIDS 12:309-313
     Abstract: OBJECTIVE: To study the spectrum of neuropathological brain lesions in HIV/AIDS cases. DESIGN: Retrospective autopsy study between 1988 and mid-1996 at a tertiary level public hospital. METHODS: Eighty-five adult brains, with at least 21 sections from each, were examined using routine and special stains. RESULTS: Risk factors in 64 men (75%) and 21 women (25%) included heterosexual contact with multiple sexual partners (83 cases, 98%), homosexual behaviour (one case, 1%) and blood transfusion (one case, 1%). Central nervous system (CNS) lesions were observed in 67 cases (79%). Opportunistic infections were present in 33 cases (39%), which included toxoplasmosis (11 cases, 13%), tuberculosis (10 cases, 12%), cryptococcosis (seven cases, 8%), and cytomegalovirus infection (six cases, 7%). Multifocal myelin loss was observed in 18 cases (21%), Microglial nodules in 15 cases (18%), and angiocentric pallor in five cases (6%). Infarcts/haemorrhages were present in 13 cases (15%), choroid plexitis in 21 cases (25%), lymphocytic meningitis without opportunistic infection in 21 cases (25%), and calcification in four cases (5%). A dual infectious pathology was observed in one case (1%). Multinucleated giant cells and primary CNS lymphoma were not found in any of our cases. CONCLUSIONS: Patient profile and risk factors for AIDS in India differ from those reported in industrialized countries. Although not reported from India in the pre-AIDS era, toxoplasmosis was the most frequently observed CNS opportunistic infection in our study. CNS tuberculosis is frequently observed in Indian AIDS cases compared with reports from industrialized countries where its occurrence is uncommon. Death due to systemic opportunistic infections may punctuate the course of HIV encephalitis and prevent its full-blown morphological expression

168. Lavi E, Kolson DL, Ulrich AM, Fu L, Gonzalez-Scarano F (1998) Chemokine receptors in the human brain and their relationship to HIV infection. J.Neurovirol. 4:301-311
     Abstract: Chemokine receptors have been recently identified as the important co-factors which in conjunction with CD4, mediate entry of HIV into its target cells. The brain is one of the most prominent targets of HIV infection, where it leads to HIV encephalitis (HIVE) and HIV-associated dementia. Knowledge of the distribution, physiology, and pathology of chemokines and chemokine receptors in the human brain is fundamental for understanding the pathogenesis of the interaction between HIV and the central nervous system (CNS). There is also increasing evidence that chemokine receptors expression in the CNS increases during pathological, especially inflammatory, conditions. The major co-factors for HIV infection, CCR5, CCR3, and CXCR4 have been detected in the human brain in a variety of cell types including Microglia, astrocytes, neurons, and vascular endothelial cells. Furthermore, antibodies to chemokine receptors can also block HIV infectivity in cultured CNS cells. This indicates that chemokine receptors are likely to have a functional role in the pathogenesis of HIVE

169. Levi G, Minghetti L, Aloisi F (1998) Regulation of prostanoid synthesis in Microglial cells and effects of prostaglandin E2 on Microglial functions. Biochimie 80:899-904
     Abstract: Brain prostanoid levels are normally low but can increase after ischemia and during inflammatory and infectious diseases. High prostanoid levels can affect brain function in several ways. In particular, prostaglandin E2 (PGE2) might exert both immunodepressive and proinflammatory actions. The present short review focuses on the regulation of prostanoid synthesis in Microglial cultures and on the possible role of PGE2 in the down-regulation of Microglial activation induced by lipopolysaccharide (LPS). Our studies were carried out using purified mouse or rat Microglial cultures. LPS induced a dose-dependent expression of the inducible isoform of cyclooxygenase (COX-2), both in neonatal and adult Microglial cultures. In the latter, the inducibility of COX-2 increased with time in culture, paralleling the acquisition of a more 'activated' Microglial phenotype, and appeared to account for the time-dependent increase in the PGE2/TXB2 production ratio. The LPS-induced COX-2 expression and prostanoid production were down-regulated by potentially neurotoxic agents, such as nitric oxide (NO), the proinflammatory cytokine IFN-gamma (which acted both directly and indirectly, through its NO-inducing activity) and the HIV regulatory protein tat. On the other hand, COX-2 expression was up-regulated by the macrophage-deactivating cytokine TGF-beta 1, by exogenous PGE2 itself, which acted through EP2 receptors linked to cyclic AMP generation, and by non steroidal anti-inflammatory drugs. Interestingly, PGE2 utilized the same EP2 receptor-mediated signal transduction mechanism to down-regulate the expression of the inducible NO synthase and the production of NO. Largely, but not exclusively, through its effect on cyclic AMP, PGE2 can also: i) depress the expression of major histocompatibility complex class II antigens and of the costimulatory molecule B7-2; ii) down-regulate TNF and up-regulate IL-10 Microglial production; iii) inhibit Microglial IL-12 secretion. These observations, together with literature data on in vivo models of central nervous system (CNS) diseases, suggest a neuroprotective role of PGE2 in pathological conditions

170. Liestael K, Goplen AK, Dunlop O, Bruun JN, Maehlen J (1998) Kaposi's sarcoma and protection from HIV dementia. Science 280:361-362

171. Lipton SA (1998) Neuronal injury associated with HIV-1: approaches to treatment. Annu.Rev.Pharmacol.Toxicol. 38:159-177
     Abstract: Mounting evidence suggests that cognitive dysfunction developing as a result of HIV-1 infection is mediated at least in part by generation of excitotoxins and free radicals in the brain. This syndrome is currently designated HIV-1-associated cognitive/motor complex, was originally termed the AIDS Dementia Complex, and for simplicity, is called AIDS dementia in this review. Recently, brains of patients with AIDS have been shown to manifest neuronal injury and apoptotic-like cell death. How can HIV-1 result in neuronal damage if neurons themselves are only rarely, if ever, infected by the virus? Experiments from several different laboratories have lent support to the existence of HIV- and immune-related toxins in a variety of in vitro and in vivo paradigms. In one recently defined pathway to neuronal injury, HIV-infected macrophages and Microglia, or immune-activated macrophages and astrocytes (activated by the shed HIV-1 envelope protein, gp120, or other viral proteins and cytokines), appear to secrete excitants and neurotoxins. These substances may include arachidonic acid, platelet-activating factor, free radicals (NO. and O2.-), glutamate, quinolinate, cysteine, amines, and as yet unidentified factors emanating from stimulated macrophages and reactive astrocytes. A final common pathway for neuronal susceptibility is operative, similar to that observed in stroke and several neurodegenerative diseases. This mechanism involves excessive activation of N-methyl-D-aspartate (NMDA) receptor-operated channels, with resultant excessive influx of Ca2+ and the generation of free radicals, leading to neuronal damage. With the very recent development of clinically tolerated NMDA antagonists, there is hope for future pharmacological intervention

172. Lokensgard JR, Chao CC, Gekker G, Hu S, Peterson PK (1998) Benzodiazepines, glia, and HIV-1 neuropathogenesis. Mol.Neurobiol. 18:23-33
     Abstract: Although the precise mechanisms whereby HIV-1 infection induces neurodegeneration have yet to be determined, a great deal of evidence has incriminated glial cells and the production of proinflammatory mediators in this pathologic process. For this reason, ideal therapeutic agents for the treatment of AIDS dementia would attenuate HIV-1 neuropathogenesis through both direct inhibition of viral expression and suppression of brain cell-produced immune mediators. Benzodiazepines (BDZs), such as Valium, are extensively prescribed drugs for anxiety disorders, which readily cross the blood-brain barrier and have demonstrated immunomodulatory properties. BDZs bind to primary human Microglial cells, the principal site of HIV-1 replication in the brain, and inhibit lipopolysaccharide (LPS) induced tumour necrosis factor (TNF-alpha) production by these cells in a concentration-dependent manner. Treatment of HIV-1-infected primary human Microglial, as well as mixed glial/neuronal, cell cultures with BDZs inhibits the expression of HIV-1 p24 antigen. BDZ-induced inhibition of HIV-1 expression in chronically infected promonocytic (U1) cells has been found to be associated with decreased activation of the nuclear transcription factor kappa B (NF-kappa B). Because HIV-1 expression is critically dependent on the cellular transcription machinery, inhibition of the activation of transcription factors, which participate in both HIV-1 expression and the production of neurotoxic immune mediators, by BDZ analogs may provide new therapeutic options for AIDS dementia

173. McCarthy M, He J, Wood C (1998) HIV-1 strain-associated variability in infection of primary neuroglia. J.Neurovirol. 4:80-89
     Abstract: Qualitative differences among strains of Human Immunodeficiency Virus type 1 (HIV-1) may influence viral infectivity for cells of the central nervous system (CNS) and determine or at least significantly influence the neuropathogenesis of brain infection. In this study, we compared infectivity for these cells in vitro among several different laboratory-adapted HIV-1 strains differing in cellular tropism. These strains included three lymphotropic strains (SF2, NL4-3, and SG3.1), two macrophage-tropic strains (SF128A, SF162), and one brain-derived strain (YU2). In Microglia, macrophage-tropic strain SF128A established productive infection while the lymphotropic strain SF2 did not. In infected astrocytes, all HIV-1 strains transiently produced variable and much lower levels of p24 antigen. Viral DNA env or tat gene sequences were amplified from infected astrocytes; the amplified signals varied among HIV-1 strains, but the strongest viral DNA signals were obtained from cells infected by the lymphotropic strains SF2 and SG3.1. Transfection of astrocytes with infectious HIV-1 proviral DNA clones confirmed the observation that HIV-1 strains differ in their ability to replicate in astrocytes. Transfection revealed post-entry blocks to replication by macrophage-tropic proviruses pSF128A and pSF162. However, cytomegalovirus (CMV) superinfection of transfected astrocytes enhanced p24 production by lymphotropic HIV-1 proviruses twofold and stimulated p24 production by the otherwise inactive macrophage-tropic proviruses. This study demonstrates the spectrum of HIV-1 strain-associated variation in infectivity for neuroglia, and suggests, in addition, that herpesviral factors or viral-induced cellular factors may stimulate HIV-1 infection in astrocytes and expand the neural cell tropism of certain HIV-1 strains

174. McManus CM, Brosnan CF, Berman JW (1998) Cytokine induction of MIP-1 alpha and MIP-1 beta in human fetal Microglia. J.Immunol. 160:1449-1455
     Abstract: Leukocyte infiltration into the central nervous system (CNS) is a key event in the inflammatory processes of neuroimmunologic diseases. Microglia, resident macrophages of the CNS, may contribute to this process by elaborating chemoattractants that are capable of recruiting leukocytes across the blood-brain barrier. Such factors have been detected in the CNS of animal models of multiple sclerosis and in the brains of human and nonhuman primates with AIDS encephalitis. As the expression of these chemoattractants may play an important role in the initiation and progression of neuroimmunologic diseases, we analyzed expression of the chemokines MIP-1 alpha, MIP-1 beta, MCP-1, and RANTES in human fetal Microglial cultures. Unstimulated Microglia expressed minimal levels of MIP-1 alpha, MIP-1 beta, and MCP-1, while RANTES was undetectable. In response to LPS, TNF-alpha, or IL-1 beta, both MIP-1 alpha and MIP-1 beta were induced at the mRNA and protein levels in a dose- and time-dependent manner. IFN-gamma did not significantly induce chemokine expression. MCP-1 was detectable in LPS- and cytokine-treated Microglia. TGF-beta, a cytokine with down-modulatory effects on other cell types, had little effect on chemokine expression in Microglia when used concomitantly before or during treatment with LPS. These results illustrate the ability of certain inflammatory stimuli to induce expression of MIP-1 alpha, MIP-1 beta, and MCP-1 by human fetal Microglia. The expression of these chemoattractants may function to recruit inflammatory cells into the CNS during the course of neuroimmunologic diseases and may modulate the ability of HIV to infect the CNS

175. Montgomery MM, Wood A, Stott EJ, Sharp C, Luthert PJ (1998) Changes in neuron size in cynomolgus macaques infected with various immunodeficiency viruses and poliovirus. Neuropathol.Appl.Neurobiol. 24:468-475
     Abstract: Human immunodeficiency virus (HIV) infection leads to clinically significant neuronal pathology, but the underlying mechanism remains unclear. Infection of rhesus macaques with the simian immunodeficiency virus SIVmac251 has been shown to cause atrophy of hippocampal pyramidal cells. The aim of the current investigation was to determine whether SIVmac251 and other viruses with differing abilities to cause immune suppression or encephalitis could cause neuronal atrophy in cynomolgus macaques. Animals infected with SIVmac251 (n = 22), HIV-2 (n = 6). SIVmac239 (n = 7) and poliovirus (n = 10) were investigated, together with 16 controls. Hippocampal pyramidal cell diameter, averaged across the four CA subfields, was reduced by 16.6% in the SIVmac251 group (P < 0.0001) and by 13.3% in the HIV-2 group (P < 0.001), even though the latter virus does not generally cause immunosuppression. Conversely, SIVmac239, which does cause immunosuppression, caused an average neuronal hypertrophy of 6.8% (P = 0.033). Of possible relevance to the different behaviour of the two SIVs is that SIVmac239 is lymphocyte tropic and does not infect CNS Microglia in vivo whereas SIVmac251 does. Animals inoculated with poliovirus into the lumbar spinal cord for polio vaccine neurovirulence testing acted as positive controls for CNS inflammation and they also showed an increase in neuronal diameter (4.1%, P = 0.025). The atrophy seen with SIVmac251 and HIV-2 involved all CA subfields but the hypertrophy following SIVmac239 or poliovirus infection was restricted to CA1 and CA2. These observations show a dissociation between the ability of immunodeficiency viruses to cause immune suppression and neuronal pathology and demonstrate that CNS inflammation per se may cause neuronal hypertrophy

176. Nishiyori A, Minami M, Ohtani Y, Takami S, Yamamoto J, Kawaguchi N, Kume T, Akaike A, Satoh M (1998) Localization of fractalkine and CX3CR1 mRNAs in rat brain: does fractalkine play a role in signaling from neuron to Microglia? FEBS Lett. 429:167-172
     Abstract: Localization of the mRNAs for fractalkine, a CX3C chemokine, and for its receptor CX3CR1 was investigated in the rat brain. In situ hybridization study revealed that fractalkine mRNA was dominantly expressed in neuronal cells particularly in the olfactory bulb, cerebral cortex, hippocampus, caudate putamen and nucleus accumbens. In vitro study using enriched neuronal or glial culture supported the dominant expression of fractalkine mRNA in neurons. On the other hand, CX3CR1 mRNA was dominantly expressed in glial cells throughout the whole brain. The in vitro study suggested the cells expressing CX3CR1 mRNA are Microglia, not astrocytes or neurons. Fractalkine appears to function as a signal molecule from neuron to Microglia

177. Power C, McArthur JC, Nath A, Wehrly K, Mayne M, Nishio J, Langelier T, Johnson RT, Chesebro B (1998) Neuronal death induced by brain-derived human immunodeficiency virus type 1 envelope genes differs between demented and nondemented AIDS patients. J.Virol. 72:9045-9053
     Abstract: Human immunodeficiency virus type 1 (HIV-1) infection of the brain results in viral replication primarily in macrophages and Microglia. Despite frequent detection of viral genome and proteins in the brains of AIDS patients with and without HIV dementia, only 20% of AIDS patients become demented. To investigate the role of viral envelope gene variation in the occurrence of dementia, we examined regions of variability in the viral envelope gene isolated from brains of AIDS patients. Brain-derived HIV-1 V1-V2 envelope sequences from seven demented and six nondemented AIDS patients displayed significant sequence differences between clinical groups, and by phylogenetic analysis, sequences from the demented group showed clustering. Infectious recombinant viruses containing brain-derived V3 sequences from both clinical groups were macrophagetropic, and viruses containing brain-derived V1, V2, and V3 sequences from both clinical groups spread efficiently in macrophages. In an indirect in vitro neurotoxicity assay using supernatant fluid from HIV-1-infected macrophages, recombinant viruses from demented patients induced greater neuronal death than viruses from nondemented patients. Thus, the HIV-1 envelope diversity observed in these patient groups appeared to influence the release of neurotoxic molecules from macrophages and might account in part for the variability in occurrence of dementia in AIDS patients

178. Rafalowska J (1998) HIV-1-infection in the CNS. A pathogenesis of some neurological syndromes in the light of recent investigations. Folia Neuropathol. 36:211-216
     Abstract: The main factors in the pathogenesis of AIDS-dementia complex (ADC) are analyzed. The author suggests that these factors can be divided into two groups. The "nonspecific" factors present in every immunologic processes manifested by inflammation compose the first group. They are cytotoxic lymphocytes T, the immunoactivation of infected macrophages, cytokines, NO, NOS and iNOS, the increase of the BBB permeability, the accumulation of beta-amyloid precursor protein, excitotoxic amino acids, various and numerous cells adhesion molecules. The second group may contain factors connected with HIV-1 infection of CNS. In the pathogenesis of AIDS an important role is played by toxic glycoproteins gp 120 and gp 41 which are in the coat of HIV-1 virus, nucleotide sequences variability, possibility of various virus replication in various parts of CNS, the participation of lymphokines IL-4 and IL-10, and presence of co-receptors to HIV-1 virus on lymphocytes, macrophages, neurons and Microglial cells

179. Sanders VJ, Pittman CA, White MG, Wang G, Wiley CA, Achim CL (1998) Chemokines and receptors in HIV encephalitis. AIDS 12:1021-1026
     Abstract: BACKGROUND: Chemokines are involved in the migration of leukocytes and have been implicated in several inflammatory diseases of the central nervous system. Some of their receptors have been proposed to mediate HIV infection. OBJECTIVE: To determine changes in chemokine and receptor expression in HIV encephalitis, and to determine whether upregulation leads to recruitment of infected monocytes across the blood-brain barrier and participates in HIV neuropathology. METHODS: Immunocytochemistry and double-label immunofluorescent laser confocal microscopy was performed with antibodies to chemokines and their receptors on brain tissues from patients who died with or without HIV encephalitis. In vivo distribution was compared with in vitro cultures of human neuroglial cells. RESULTS: The beta-chemokines monocyte chemotactic protein-1, macrophage inflammatory protein-1alpha, and RANTES were detected on brain macrophages. Their presence was associated with the histopathological signs of HIV encephalitis. The alpha-chemokines IP-10 (10 kDa inflammatory protein) and interleukin-8 were expressed by astrocytes in all tissues, including controls. Presence of the CXC-chemokine receptor (CXCR)-4 was seen on brain macrophages/Microglia, neurons, and astrocytes. CC-Chemokine receptor (CCR)-5 was detected only on macrophages/Microglia. CCR-3 and CCR-1 were expressed by macrophages and endothelial cells. In vitro studies examining the presence of CCR-3, CCR-5, and CXCR-4 on human brain cell cultures demonstrated abundant neuronal and Microglial expression. CONCLUSIONS: Expression of a variety of chemokines and receptors was shown to be increased in HIV encephalitis brain tissues particularly in areas of neuroglial reaction. The expression pattern supported their involvement in the recruitment of inflammatory infiltrates and formation of Microglial nodules. Presence of chemokine receptors on neurons may be involved in the pathogenesis of neurologic damage in AIDS patients

180. Scorziello A, Florio T, Bajetto A, Schettini G (1998) Intracellular signalling mediating HIV-1 gp120 neurotoxicity. Cell Signal. 10:75-84
     Abstract: During the last few years several studies have been undertaken to characterise the role of gp120, the HIV-1 envelope glycoprotein, in the pathogenesis of neurological defects associated with AIDS. However, neurons did not appear to be the main target of the virus, since the widespread neuronal damage is not associated with a productive viral infection in neurons. The current opinion supports the hypothesis that an indirect mechanism exists to explain the neuronal cell death which occurs in patients infected by HIV-1. In particular, several reports suggest that gp120 may be the main candidate as mediator of the neurological deficits during HIV-1 infection and demonstrate that this molecule affects neuronal survival through a direct interaction with non-neuronal cell types such as monocytes, macrophages/Microglia and astrocytes

181. Shieh JT, Albright AV, Sharron M, Gartner S, Strizki J, Doms RW, Gonzalez-Scarano F (1998) Chemokine receptor utilization by human immunodeficiency virus type 1 isolates that replicate in Microglia. J.Virol. 72:4243-4249
     Abstract: The role of human immunodeficiency virus (HIV) strain variability remains a key unanswered question in HIV dementia, a condition affecting around 20% of infected individuals. Several groups have shown that viruses within the central nervous system (CNS) of infected patients constitute an independently evolving subset of HIV strains. A potential explanation for the replication and sequestration of viruses within the CNS is the preferential use of certain chemokine receptors present in Microglia. To determine the role of specific chemokine coreceptors in infection of adult Microglial cells, we obtained a small panel of HIV type 1 brain isolates, as well as other HIV strains that replicate well in cultured Microglial cells. These viruses and molecular clones of their envelopes were used in infections, in cell-to-cell fusion assays, and in the construction of pseudotypes. The results demonstrate the predominant use of CCR5, at least among the major coreceptors, with minor use of CCR3 and CXCR4 by some of the isolates or their envelope clones

182. Soontornniyomkij V, Wang G, Pittman CA, Wiley CA, Achim CL (1998) Expression of brain-derived neurotrophic factor protein in activated Microglia of human immunodeficiency virus type 1 encephalitis. Neuropathol.Appl.Neurobiol. 24:453-460
     Abstract: The role of neurotrophic factors and their therapeutic potential have been investigated in various neurodegenerative disorders. In neurodegeneration associated with human immunodeficiency virus (HIV) infection, neuronal function and survival may be affected by abnormal neurotrophic regulation involving HIV-infected Microglia and reactive astrocytes. To characterize the cellular localization of brain-derived neurotrophic factor (BDNF) and its high-affinity tyrosine kinase receptor, trkB, proteins in HIV-1 encephalitis, we examined post-mortem brains from patients with acquired immunodeficiency syndrome and brains from non-HIV-infected controls. Using double immunofluorescent confocal microscopy, we found that BDNF immunoreactivity was distributed in neocortical neuronal perikarya and neuritic processes, while in the striatum only neurites were BDNF-immunoreactive. Additionally, the striatum with HIV infection was characterized by BDNF immunoreactivity in infiltrating activated Microglia/macrophages and multinucleated giant cells. Catalytic trkB receptor immunoreactivity was observed in neuronal perikarya in the neocortex and striatum, as well as in reactive astrocytes within HIV-infected regions. Our findings suggest that expression of BDNF by activated Microglia in HIV-1 encephalitis may affect neuronal survival and astroglial response through corresponding trkB receptors

183. Suzumura A, Sawada M, Makino M, Takayanagi T (1998) Propentofylline inhibits production of TNFalpha and infection of LP-BM5 murine leukemia virus in glial cells. J.Neurovirol. 4:553-559
     Abstract: We examined the effects of a xanthine derivative, propentofylline, on TNFalpha production by glial cells and on infection ofglial cells with a murine leukemia virus, LP-BM5, which induces murine AIDS in susceptible mice. Propentofylline suppressed TNFalpha production in glial cells and also effectively suppressed infection ofglial cells with LP-BM5 in vitro. Addition ofTNFalpha, but not IL-1 or IL-6, abolished the suppressive effects ofpropentofylline. Anti-TNFalpha antibody also suppressed infection of LP-BM5 in these cells. These findings suggest that propentofylline suppressed LP-BM5 infection in glial cells by suppressing TNFalpha production by these cells. Because propentofylline reportedly passes through the blood-brain barrier, it may be useful in the treatment of central nervous system involvement by HIV infection or neurological diseases in which TNFalpha plays a causative role, such as multiple sclerosis

184. Tan SV, Guiloff RJ (1998) Hypothesis on the pathogenesis of vacuolar myelopathy, dementia, and peripheral neuropathy in AIDS. J.Neurol.Neurosurg.Psychiatry 65:23-28
     Abstract: Certain aspects of the clinical syndrome of dementia, cerebral atrophy, predominantly sensory neuropathy, and vacuolar myelopathy in AIDS resemble those seen in vitamin B12 deficiency. Pathologically, there are similarities not only in the changes in the spinal cord, but also in the brain and peripheral nerves. The pathogenesis of vacuolar myelopathy may be secondary to a combination of immune mediated myelin and oligodendrocyte injury, and simultaneous impairment of repair mechanisms due to a deficiency of S-adenosylmethionine (SAM). Products derived from macrophages may interfere directly with the methyl transfer cycle through the generation of reactive oxygen intermediates and reactions involving nitric oxide and peroxynitrite which may limit the supply of methionine for conversion to SAM, both by direct interaction as well as through inhibition of methionine synthase. Macrophage activation with secretion of cytokines and other biologically reactive substances within the nervous system is sustained in the late stages of HIV infection by the general effects of immune depletion, including loss of T cells (with concomitant reduction of macrophage regulatory molecules) and recurrent opportunistic infections, and may be further augmented by the local presence of the virus itself (or its surface glycoprotein gp120). This would account for the common, but not exclusive, occurrence of vacuolar myelopathy in AIDS. The ability of the virus and its products to stimulate macrophage and Microglial activation may also explain the association between severity of vacuolar myelopathy and the presence of HIV encephalitis. A similar mechanism may underlie the pathogenesis of dementia, cerebral atrophy, and peripheral neuropathy. Local factors or differential susceptibility between the central and peripheral nervous system may determine whether myelinotoxic or neurotoxic processes predominate; the prominence of myelin involvement in the spinal cord, and axonal involvement peripherally may reflect both ends of this range, with the brain manifesting a more equal balance of both processes

185. Yeung MC, Geertsma F, Liu J, Lau AS (1998) Inhibition of HIV-1 gp120-induced apoptosis in neuroblastoma SK-N-SH cells by an antisense oligodeoxynucleotide against p53. AIDS 12:349-354
     Abstract: OBJECTIVES: This study examines the cytotoxicity potential and the mechanism of toxicity of the HIV-1 gp120 on human neuroblastoma cells. DESIGN: Previous data from our group have suggested that the HIV-1 envelope protein gp120 promotes the secretion of tumor necrosis factor-alpha and other factors by astrocytes and Microglial cells present in primary human brain cell cultures, thereby contributing to the injury of neurons in these cultures. This study investigates the cytotoxicity potential and the mechanism of toxicity of gp120 on human neuroblastoma cells. METHODS: SK-N-SH cells were treated with HIV-1 gp120, and was followed by in situ DNA fragmentation staining and small molecular weight DNA extraction studies to ascertain the induction of apoptosis by gp120 in these cells. To evaluate a potential role of the growth suppressor gene p53, gp120-treated SK-N-SH cells were subjected to reverse transcription polymerase chain reaction (RT-PCR) and Western blot analyses for the induction of p53. An antisense oligodeoxynucleotide against p53 was used to investigate the role of p53 in the gp120-induced apoptosis in these cells. RESULTS: Data from T7 DNA polymerase staining and small molecular weight DNA extraction studies demonstrated that gp120-induced DNA breakage in SK-N-SH cells with fragmentation patterns characteristic of apoptosis. RT-PCR and Western blot analyses revealed that the gp120-mediated induction of apoptosis was dependent on a gp120-induced and gp120-sustained upregulation of p53. The induction of p53 by gp120 was specific, since an antibody against gp120 prevented both the induction of p53 and subsequent apoptosis in SK-N-SH cells. The critical role of p53 was further illustrated by the effectiveness of a p53 antisense oligodeoxynucleotide to inhibit the gp120-induced apoptosis. As a control, the apoptosis-inducing potential of gp120 on SK-N-SH cells was not seen in the HIV-1 Gag proteins even when used at up to 5 nM. CONCLUSIONS: These results established that HIV-1 gp120 is potentially cytotoxic to human neuronal cells through the induction of p53, which may eventually lead to induction of apoptosis

186. Belichenko PV, Miklossy J, Celio MR (1997) HIV-I induced destruction of neocortical extracellular matrix components in AIDS victims. Neurobiol.Dis. 4:301-310
     Abstract: Neurological dysfunction is not uncommon in patients suffering from acquired immunodeficiency syndrome (AIDS) and, when manifested, intimates involvement of the central nervous system. Here, the human immunodeficiency virus (HIV) infects preferentially Microglial cells, which thereby release substances known to interfere with neuronal function. One class of agents set free in this manner are proteases; these degrade certain components within, and thereby undermine the integrity of, the extracellular matrix (ECM) compartment, which plays a vital role in cell-to-cell communication. We wished to ascertain whether the ECM compartment is indeed disrupted in the brains of AIDS victims. We examined the neocortical areas of 27 AIDS autopsy cases, including 9 with diagnosed HIV-encephalopathy (HIVE); 8 HIV-seronegative cases with various types of brain lesion, including viral infections, were also included in this study. HIV-antigens and DNA were identified by use of immunohistochemistry and in situ hybridization, and ECM components by lectin staining and immunohistochemistry. Of the 27 AIDS cases examined, each of the 9 with HIVE was completely devoid of labeled ECM components; 8 of the 18 without HIVE had incurred substantial losses, and only 2 manifested a normal complement of constituents within this compartment. With respect to stratal and topographic variations, layers II and III were less affected than layers V to VII, as was the frontal cortex relative to other areas. These findings confirmed our expectations of the brain's ECM undergoing degradation following HIV infection, and these changes may well underlie the neurological disturbances manifested in AIDS patients

187. Cunningham AL, Naif H, Saksena N, Lynch G, Chang J, Li S, Jozwiak R, Alali M, Wang B, Fear W, Sloane A, Pemberton L, Brew B (1997) HIV infection of macrophages and pathogenesis of AIDS dementia complex: interaction of the host cell and viral genotype. J.Leukoc.Biol. 62:117-125
     Abstract: AIDS dementia complex (ADC) develops in only a third of HIV-infected patients who progress to AIDS. Macrophages and Microglial cells are the major cellular sites of productive HIV replication in brain. Using 11 blood isolates of HIV from asymptomatic patients there was marked variation in tropism and the level of productive infection in recently adherent monocytes and monocyte-derived macrophages cultured in vitro. However, less variation was seen with 19 blood isolates from advanced HIV infection and 11 postmortem tissue isolates from brain, cerebrospinal fluid, spleen, and lung. Newly adherent monocytes expressed CCR5 in all seven patients tested, consistent with their susceptibility to infection but not explaining the above variability. There is, also marked regional variability in neuropathology in the brain of patients with ADC. We have demonstrated that there was marked variation in the V3 sequences of HIV clones from different regions of the cortex of a patient with ADC, suggesting independent evolution of HIV replication in brain. Furthermore, production of the neurotoxin quinolinic acid from HIV-infected macrophages varied, depending on the host and source of HIV isolate. Hence variations in viral genotype, production by infected macrophages, and subsequent toxin production may contribute to the variability in neuropathology between individuals and between different regions of the brain in the same individual

188. Dal Canto MC (1997) Mechanisms of HIV infection of the central nervous system and pathogenesis of AIDS-dementia complex. Neuroimaging Clin.N.Am. 7:231-241
     Abstract: In many patients with AIDS, severe neurologic deficits develop that have been designated the cf2HIV-associated cognitive-motor complex. cf1 Pathologically, these symptoms correlate with a low-grade inflammatory condition, referred to as cf2HIV encephalitis,cf1 in which the most characteristic change is the presence of multinucleated giant cells. Cortical changes include neuronal loss and alterations of dendrites and synapses. There is pallor of white matter generally associated with the mononuclear inflammatory infiltrates. The only cells that seem to be directly infected by HIV are the Microglia/monocyte and the giant cells derived from fusion of monocytes. It is hypothesized, therefore, that cortical and white matter alterations in patients with this syndrome depend on the production of injurious soluble factors liberated by these cells and by astrocytes under the influence of many of these same factors. This article reviews recent advances in the understanding of these secondary effects and discusses pathogenetic mechanisms of tissue injury

189. Dick AD, Pell M, Brew BJ, Foulcher E, Sedgwick JD (1997) Direct ex vivo flow cytometric analysis of human Microglial cell CD4 expression: examination of central nervous system biopsy specimens from HIV-seropositive patients and patients with other neurological disease. AIDS 11:1699-1708
     Abstract: OBJECTIVE: To define a clear ex vivo flow cytometric phenotype for adult human Microglia that would distinguish it from all other macrophage lineage cells in the central nervous system (CNS) or blood, and to utilize this phenotype to examine the activation state and CD4 expression of Microglia freshly derived from CNS tissue of HIV-positive patients and those with other neurological diseases. DESIGN: Fresh human CNS tissue from both HIV-uninfected and HIV-infected individuals was obtained by biopsy or resection, and cells isolated immediately, labelled for flow cytometry and analysed. METHODS: A Percoll density gradient isolation technique and phenotypic characteristics used for rodent Microglia were applied and modified. RESULTS: Resident Microglia could clearly be defined by the flow cytometric phenotype CD45low CD4- CD11b+ CD11chigh major histocompatibility complex (MHC) class II+

190. Fiala M, Looney DJ, Stins M, Way DD, Zhang L, Gan X, Chiappelli F, Schweitzer ES, Shapshak P, Weinand M, Graves MC, Witte M, Kim KS (1997) TNF-alpha opens a paracellular route for HIV-1 invasion across the blood-brain barrier. Mol.Med. 3:553-564
     Abstract: BACKGROUND: HIV-1 invades the central nervous system early after infection when macrophage infiltration of the brain is low but myelin pallor is suggestive of blood-brain-barrier damage. High-level plasma viremia is a likely source of brain infection. To understand the invasion route, we investigated virus penetration across in vitro models with contrasting paracellular permeability subjected to TNF-alpha. MATERIALS AND METHODS: Blood-brain-barrier models constructed with human brain microvascular endothelial cells, fetal astrocytes, and collagen I or fibronectin matrix responded in a dose-related fashion to cytokines and ligands modulating paracellular permeability and cell migration. Virus penetration was measured by infectious and quantitative HIV-1 RNA assays. Barrier permeability was determined using inulin or dextran. RESULTS: Cell-free HIV-1 was retained by the blood-brain barrier with close to 100% efficiency. TNF-alpha increased virus penetration by a paracellular route in a dose-dependent manner proportionately to basal permeability. Brain endothelial cells were the main barrier to HIV-1. HIV-1 with monocytes attracted monocyte migration into the brain chamber. CONCLUSIONS: Early after the infection, the blood-brain barrier protects the brain from HIV-1. Immune mediators, such as TNF-alpha, open a paracellular route for the virus into the brain. The virus and viral proteins stimulate brain Microglia and macrophages to attract monocytes into the brain. Infiltrating macrophages cause progression of HIV-1 encephalitis

191. Gelman BB, Wolf DA, Rodriguez-Wolf M, West AB, Haque AK, Cloyd M (1997) Mononuclear phagocyte hydrolytic enzyme activity associated with cerebral HIV-1 infection. Am.J.Pathol. 151:1437-1446
     Abstract: In patients with HIV encephalitis, activated macrophages and Microglial cells in the brain are infected by the human immunodeficiency virus (HIV-1). Immune activation can release neurotoxic chemicals including cytokines, free radicals, autocoids, and hydrolytic enzymes. In this study, the presence of hydrolytic enzymes in acquired immune deficiency syndrome (AIDS)-related neurodegeneration was addressed. Activities of four lysosomal hydrolases were assayed in the frontal lobe of 69 males who died with AIDS and 31 age-matched control men. Activities of all four enzymes were increased significantly (1.6 to 3.6 times) in white matter of patients with AIDS. Less pronounced increases were present in cerebral cortex. Of 69 of the subjects with AIDS, 50 (72%), had at least one abnormally active enzyme. Patients with HIV encephalitis and other neuropathological changes were affected as were many subjects without any clear neuropathological anomaly. Lysosomal cathepsin D immunostaining revealed increased lysosomes within perivascular macrophages, multinucleated cells, activated Microglial cells, and hypertrophic astrocytes. Increased enzyme activity was correlated significantly with assay results for HIV-1 DNA using the polymerase chain reaction. The release of acid hydrolases associated with cerebral HIV-1 infection could lead to unopposed hydrolysis of matrix and surface proteins. These post-translational disturbances could contribute to white matter and synaptic injury in AIDS

192. Gonzalez-Scarano F, Strizki JM, Albright A, Shieh J (1997) Use of primary CNS cultures to investigate HIV neurotropism. J.Neurovirol. 3 Suppl 1:S11-S13

193. Goodkin K, Wilkie FL, Concha M, Asthana D, Shapshak P, Douyon R, Fujimura RK, LoPiccolo C (1997) Subtle neuropsychological impairment and minor cognitive-motor disorder in HIV-1 infection. Neuroradiological, neurophysiological, neuroimmunological, and virological correlates. Neuroimaging Clin.N.Am. 7:561-579
     Abstract: HIV-1 infection of brain may be associated with multiple treatment targets, only the most severe of which is represented by HAD. Focusing on earlier treatment targets such as MCMD and cognitive-motor impairment in the absence of any clinical disorder (as well as neuroprotection) may prove to be of greater clinical utility in the treatment and prevention of such impairment than a focus on later-stage cognitive-motor disease, when neuronal cell death is already extensive. This may be especially important now that improvements using the protease inhibitors in triple-drug combination regimens have reduced plasma viral load to unmeasurable levels, while these drugs do not penetrate the CSF well. Currently, peripheral blood markers do not appear to be highly sensitive for central nervous system impairment, and specific CSF laboratory markers have some limited value at present-while requiring a lumbar puncture to obtain. Hence, a role for noninvasive techniques using neuroimaging exists in the clinical management of HIV-1-infected patients. To date, structural imaging techniques have proven limited in value for HIV-1-specific impairment. Several functional techniques (PET, SPECT, and MR spectroscopy) have now provided promising results for the purposes of identifying clinically significant dysfunction, relating such dysfunction to clinical neuropsychiatric symptom status, and for treatment response monitoring. Further studies are needed to examine the extent to which such imaging modalities not only parallel clinically relevant aspects of HIV-1 disease progression, but also match specific types of neuropsychologic performance deficits with potential significance for neuroanatomical localization. It is particularly important to include neurophysiological, neuroimmunological, and virological measures in studies that examine clinical neuropsychiatric status with neuroimaging techniques. In addition, the inclusion of neuropathology data, where possible, is important because demonstration of HIV-1 encephalitis cannot be equated with clinical disorder and because specific HIV-1-associated pathological changes have not yet been proven to be assessed well with neuroimaging techniques (e.g., the extent of Microglial cell and macrophage activation). Also, treatment response studies are needed in conjunction with primary antiretroviral therapy regimens specifically aimed at central nervous system penetration (e.g., GW1592, GW141, and nevirapine). The results of such work will provide the data required to determine whether these promising functional neuroimaging techniques will aid in meeting the expected, imminent increase in clinical burden of this frequent complication of HIV-1 infection

194. Gray F (1997) [Lesions of the central nervous system in the early stages of human immunodeficiency virus infection]. Rev.Neurol.(Paris) 153:629-640
     Abstract: Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remains neurologically unimpaired during the so called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, there are very few neuropathological studies in the early pre-AIDS stages and the natural history of central nervous system changes in HIV-1 infection remains poorly understood. Examination of brains of asymptomatic HIV-1 positive individuals who died accidentally and of rare cases with acute fatal encephalopathy revealing HIV infection, and comparison with experimental simian immunodeficiency virus and feline immunodeficiency virus infections suggest that invasion of the CNS by HIV-1 occurs at the time of primary infection and induces an immunological process in the central nervous system. This includes an inflammatory T-cell reaction with vasculitis and leptomeningitis, and immune activation of brain parenchyma with increased number of Microglial cells, upregulation of major histocompatibility complex class II antigens and local production of cytokines. Myelin pallor and gliosis of the white matter are usually found are likely to be the consequence of opening of the blood brain barrier due to vasculitis; direct damage to oligodendrocytes by cytokines may also interfere. These white matter changes may explain, at least partly, the early cerebral atrophy observed, by magnetic resonance imaging, in asymptomatic HIV-1 carriers. In contrast, cortical damage seems to be a late event in the course of HIV-1 infection. There is no significant neuronal loss at the early stages of the disease, no accompanying increase in glial fibrillary acid protein staining in the cortex, and only exceptional neuronal apoptosis. Although HIV-1 proviral DNA may be demonstrated in a number of brains, viral replication remains very low during the asymptomatic stage of HIV-1 infection. This makes it likely that, although opening of the blood brain barrier may facilitate viral entry into the brain, specific immune responses including both neutralising antibodies and cytotoxic T-lymphocytes, continuously inhibits viral replication at that stage

195. Hao HN, Chiu FC, Losev L, Weidenheim KM, Rashbaum WK, Lyman WD (1997) HIV infection of human fetal neural cells is mediated by gp120 binding to a cell membrane-associated molecule that is not CD4 nor galactocerebroside. Brain Res. 764:149-157
     Abstract: HIV infection of central nervous system (CNS) tissue is a common finding in both adult and pediatric AIDS. Because most children are believed to be infected perinatally, we have developed a model of HIV CNS infection that utilizes explant organotypic cultures of human fetal CNS tissue. Using this model we previously reported that both lymphocytotropic and monocytotropic HIV isolates infect Microglia and astrocytes. However, the mechanism by which HIV infects these cells remains to be elucidated. We have observed that neural cell infection in these cultures may be the result of receptor-mediated endocytosis. In order to confirm this observation and to determine the ligand responsible for this process, organotypic cultures were exposed to untreated HIV, HIV pretreated with soluble CD4 (sCD4) or, as a control, heat-inactivated HIV. To address the question of a putative receptor for HIV infection, CNS cultures were either untreated or pretreated with gp120 or with the deglycosylated form of this protein. Other cultures were treated with antibodies to CD4 (anti-T4A) or to galactocerebroside (GC). Results demonstrate that pretreatment of either HIV with sCD4 or CNS cultures with gp120 significantly inhibits HIV infection. The inhibition of infection was demonstrated by a reduction in the number of cells positive for HIV proteins and by decreases in HIV proviral DNA and p24 production. Pretreatment of CNS cultures with deglycosylated gp120, anti-T4A or anti-GC antibodies did not inhibit HIV infection. These data suggest that HIV gp120 is needed for binding to a surface molecule on CNS cells that is not CD4 nor GC and that this molecule may function as a receptor and lead to infection of neural cells

196. He J, Chen Y, Farzan M, Choe H, Ohagen A, Gartner S, Busciglio J, Yang X, Hofmann W, Newman W, Mackay CR, Sodroski J, Gabuzda D (1997) CCR3 and CCR5 are co-receptors for HIV-1 infection of Microglia. Nature 385:645-649
     Abstract: Several members of the chemokine receptor family are used together with CD4 for HIV-1 entry into target cells. T cell line-tropic (T-tropic) HIV-1 viruses use the chemokine receptor CXCR4 as a co-receptor, whereas macrophage-tropic (M-tropic) primary viruses use CCR5 (refs 2-6). Individuals with defective CCR5 alleles exhibit resistance to HIV-1 infection, suggesting that CCR5 has an important role in vivo in HIV-1 replication. A subset of primary viruses can use CCR3 as well as CCR5 as a co-receptor, but the in vivo contribution of CCR3 to HIV-1 infection and pathogenesis is unknown. HIV-1 infects the central nervous system (CNS) and causes the dementia associated with AIDS. Here we report that the major target cells for HIV-1 infection in the CNS, the Microglia, express both CCR3 and CCR5. The CCR3 ligand, eotaxin, and an anti-CCR3 antibody inhibited HIV-1 infection of Microglia, as did MIP-1beta, which is a CCR5 ligand. Our results suggest that both CCR3 and CCR5 promote efficient infection of the CNS by HIV-1

197. Lannuzel A, Barnier JV, Hery C, Huynh VT, Guibert B, Gray F, Vincent JD, Tardieu M (1997) Human immunodeficiency virus type 1 and its coat protein gp120 induce apoptosis and activate JNK and ERK mitogen-activated protein kinases in human neurons. Ann.Neurol. 42:847-856
     Abstract: Detection of apoptotic neurons and Microglial cells in the brains of human immunodeficiency virus type 1 (HIV-1)-infected patients has suggested that programmed cell death may be implicated in the physiopathology of HIV-1 encephalopathy. To analyze in vitro the intracellular signals induced by HIV-1 in human neurons and the associated neuronal death, we tested cultured human central nervous system (CNS) cells for apoptosis induced by HIV-1 and gp120 and for signaling pathways activated by gp120. HIV-1 and gp120 induced apoptosis of neurons and Microglial cells but not of astrocytes or transformed Microglial cells. Gp120 activated c-Jun N-terminal kinase (JNK) and p42 extracellular-regulated kinase (ERK) in primary CNS cells, with an early peak of activation at 2 to 5 minutes that was not present when pure Microglial or astrocyte cultures were tested, followed by a late and sustained activation (10 and 60 minutes) in primary and enriched glial cell cultures as well as in transformed Microglial cells. This demonstrates that gp120 could be an effector of HIV-1-induced apoptosis in the CNS and act directly on neuronal and glial cells

198. Lavi E, Strizki JM, Ulrich AM, Zhang W, Fu L, Wang Q, O'Connor M, Hoxie JA, Gonzalez-Scarano F (1997) CXCR-4 (Fusin), a co-receptor for the type 1 human immunodeficiency virus (HIV-1), is expressed in the human brain in a variety of cell types, including Microglia and neurons. Am.J.Pathol. 151:1035-1042
     Abstract: Entry of the type 1 human immunodeficiency virus into most cells requires the presence of the CD4 protein in combination with one of several recently described co-receptors. CXCR-4 (fusin) was the first identified, and it serves as co-receptor for T-cell-line tropic (T-tropic) HIV-1 isolates. To determine the expression of CXCR-4 in the brain, a major target of HIV pathology, we used immunohistochemistry and reverse transcriptase polymerase chain reaction with CXCR-4-specific antibodies and probes. We found that CXCR-4 was expressed in several cell types in brain, but notably in neurons and Microglia, a finding that was replicated in tissue culture. The study of the expression of CXCR-4 in the brain, which may be one of many chemokine receptors in the central nervous system, may provide further insight into the interactions between brain cells, pathogens, and the immune system, and help understand the pathogenesis of HIV dementia

199. Limoges J, Persidsky Y, Bock P, Gendelman HE (1997) Dexamethasone therapy worsens the neuropathology of human immunodeficiency virus type 1 encephalitis in SCID mice. J.Infect.Dis. 175:1368-1381
     Abstract: Human immunodeficiency virus (HIV) dementia is a late complication of viral infection. Cognitive dysfunction revolves around the secretion of neurotoxins from immunologically competent virus-infected brain macrophages and Microglia. Such macrophage neurotoxins are inflammatory factors that produce selective neuronal dysfunction and ultimately cell death. To evaluate the potential efficacy of antiinflammatory therapy for HIV dementia, dexamethasone was administered to severe combined immunodeficient mice with HIV-1 encephalitis. Mice were given therapeutic doses of dexamethasone before intracerebral inoculation with HIV-1-infected human monocytes. Histochemical evaluation showed a worsening of neuropathology after treatment, with astrogliosis and increased apoptosis of neurons. Laboratory investigation of the mechanisms for the dexamethasone effects revealed increased viability of HIV-infected macrophages and incomplete suppression of neurotoxic inflammatory secretions. The results suggest the need for caution in administering glucocorticoids for treatment of HIV encephalitis in humans

200. Lin XH, Kashima Y, Khan M, Heller KB, Gu XZ, Sadun AA (1997) An immunohistochemical study of TNF-alpha in optic nerves from AIDS patients. Curr.Eye Res. 16:1064-1068
     Abstract: PURPOSE: Both in vitro and in vivo studies have implicated a role for tumor necrosis factor (TNF-alpha) in the pathology of demyelinating diseases. The purpose of this study was to address the hypothesis that TNF-alpha is a mediator of AIDS-related optic nerve injury and to determine the cell types involved in the proliferation of TNF-alpha in the AIDS optic nerve. METHODS: Ten optic nerves from seven patients with AIDS, and three from persons who were HIV negative were stained, using the indirect immunoperoxidase method. Six of the ten AIDS optic nerves were positive for cytomegalovirus (CMV), but the remainder did not have abnormal fundus findings. RESULTS: In all the optic nerves from AIDS patients with or without CMV retinitis, the vast majority of astrocytes stained strongly for TNF-alpha. Microglial cells (MPS-derived macrophages) varied from not staining to staining strongly positive for TNF-alpha. However, oligodendrocytes were not labeled positively for TNF-alpha. Some endothelial cells also stained for TNF-alpha. Examination of normal optic nerves and controls did not reveal any cell type that stained positively for TNF-alpha. CONCLUSIONS: The present study supports the contention that TNF-alpha is a major mediator of AIDS-associated optic neuropathy. HIV infection induces the production of TNF-alpha in macrophages and astrocytes, which probably causes demyelination and other neuronal damage

201. Lokensgard JR, Gekker G, Ehrlich LC, Hu S, Chao CC, Peterson PK (1997) Proinflammatory cytokines inhibit HIV-1(SF162) expression in acutely infected human brain cell cultures. J.Immunol. 158:2449-2455
     Abstract: An understanding of how viral replication in glial cells responds to proinflammatory cytokines is important in delineating HIV-1 neuropathogenesis. Because no information is available in the literature regarding the regulatory effects of exogenous cytokines on acute HIV-1 replication in human brain cells, we studied the impact of cytokine treatment on viral p24 Ag expression. Based upon reports using mononuclear phagocytes derived from somatic sources, we hypothesized that TNF-alpha, IL-1 beta, and IL-6 would up-regulate the expression of HIV-1(SF162) (a monocytotropic strain) in purified Microglial cells and in mixed brain cell cultures. This hypothesis was not supported. In fact, a contrary, unexpected result was obtained; whereas in purified Microglial cultures TNF-alpha displayed a mild stimulatory effect on HIV-1 expression (15% increase in p24 Ag production compared with control cultures), surprisingly, IL-1 beta and IL-6 were highly suppressive (91 and 83% inhibition of HIV expression, respectively). In contrast to the findings in Microglial cell cultures, TNF-alpha profoundly suppressed (84%) HIV-1 expression in mixed brain cell cultures, as did IL-1 beta (82%), and IL-6 was moderately suppressive (55% inhibition). In an attempt to identify factors responsible for the differential effects of TNF-alpha in the two brain cell infection models, it was found that compared with Microglial cell cultures, TNF-alpha treatment of mixed brain cell cultures released significantly greater amounts of RANTES (regulated upon activation, normal T cell expressed and secreted) and macrophage inflammatory protein-1 alpha, beta-chemokines that have been suggested to have anti-HIV-1 effects. Thus, these data suggest that proinflammatory cytokines possess anti-HIV-1 activity in the central nervous system

202. Masliah E, Heaton RK, Marcotte TD, Ellis RJ, Wiley CA, Mallory M, Achim CL, McCutchan JA, Nelson JA, Atkinson JH, Grant I (1997) Dendritic injury is a pathological substrate for human immunodeficiency virus-related cognitive disorders. HNRC Group. The HIV Neurobehavioral Research Center. Ann.Neurol. 42:963-972
     Abstract: To determine the neuropathological substrate of human immunodeficiency virus (HIV)-associated neurocognitive disorders, we examined persons with acquired immunodeficiency syndrome before their death and related their antemortem neuropsychological performance to postmortem indicators of HIV encephalitis, viral burden, and presynaptic and postsynaptic neuronal injury. Of 20 prospectively examined cases, 9 were neurocognitively normal, 5 showed neuropsychological impairment, 5 had minor cognitive/motor disorder, and 1 was demented. Degree of neurocognitive impairment was strongly related to the amount of dendritic simplification based on microtubule-associated protein 2 immunohistochemical staining, somewhat less so to a semiquantitative viral burden score based on numbers of HIV gp41-immunoreactive cells, and much less so to the presence of multinucleated giant cells or Microglial nodules. It appears that even milder neurocognitive impairment reflects microneuroanatomical injury to synaptic structures

203. Mayer V, Schmidtmayerova H (1997) [Encephalopathy in AIDS--increased formation of beta-chemokines in monocytes after HIV-1 virus infection: mechanisms of CNS involvement]. Bratisl.Lek.Listy 98:330-334
     Abstract: The characteristic trait of the family of lentiviruses (Retroviridae) which includes the human immune deficiency virus (HIV), is the tendency to cause a subacute neurologic disease in their animal host. The neuraxis can be inflicted at all its levels. In the advanced stage of HIV disease, more than 60 percent of patients suffer from a clinically evident neurological dysfunction. Neuropathologic changes are demonstrated in 75 - 90 percent of them at autopsy. HIV enters the CNS during the early phase of infection. HIV replicates predominantly in the nervous tissue macrophages which serve also as intrathecal reservoirs of infection. HIV isolated from the CNS is usually macrophagotropic. Neural cells are not susceptible to a productive HIV infection, contrasting with the permissivity of activated astroglial cells. The neuropathological picture of the brain involvement is typical by the giant multinuclear cells, i.e. fused monocytes/macrophages, then neuronal loss and changes in the white matter. The clinical manifestations of CNS involvement (AIDS encephalopathy) in HIV disease are variable protean, frequently associated with dementia. The pathogenesis of the neurological disease remains elusive. The cells supporting the HIV replication in the CNS (Microglia, monocytes, astroglia) do not play a major role in dementia development. The neurotoxicity of viral glycoproteins, virus-induced cytokines and neurotoxin produced by CNS macrophages infected with particularly efficiently replicating HIV strains are being intensively studied. Dementia is associated with an increased virus load in the brain in the advanced stage of HIV disease. Neurotoxicity associated with HIV-infected Microglial cells and macrophages activity remain to be considered, for the time being, as the most likely pathogenetic mechanism of neural dysfunction and injury. Our investigations have demonstrated that HIV infection of macrophages stimulate considerably the synthesis of MIP-1-alpha, MIP-1-beta RANTES chemokines (subgroup CC). These substances by their chemoattractant and activating properties may participate in the pathogenesis of HIV/AIDS encephalopathy, contributing to leukocytosis and inflammation, increasing thus the population of HIV-susceptible cells, facilitating their infection and enhancing finally the intrathecal spread of virus. (Tab. 2, Ref. 22.)

204. Meeker RB, Thiede BA, Hall C, English R, Tompkins M (1997) Cortical cell loss in asymptomatic cats experimentally infected with feline immunodeficiency virus. AIDS Res.Hum.Retroviruses 13:1131-1140
     Abstract: Specific pathogen-free cats experimentally infected with feline immunodeficiency virus (FIV) were used to evaluate the development of central nervous system changes during the asymptomatic stages of viral infection. The brains of asyptomatic cats were examined at postinoculation times ranging from 8 weeks to 3 years for changes in neuron density, glutamate receptor density, and synaptophysin immunoreactivity. At 2-3 years postinoculation a small decrease in neuronal density was found in layers 2-3 and layer 5 of the frontal cortex (-14.4%), parietal cortex (-18.1%), and striatum (-29.5%). The only other indications of pathology within these regions were a mild diffuse astrogliosis, occasional Microglial nodules, and the accumulation of satellite cells around selected neurons. An average loss of large neurons of 56-68% was seen in the cortex of four random source cats euthanized with AIDS. These values contrasted with the absence of any significant cell loss in FIV-infected cats 18 weeks after inoculation or FIV-negative controls. The loss of neurons in the asymptomatic cats showed a significant positive correlation with a decrease in the blood CD4:CD8 ratios. Morphometric evaluation of synaptic terminal densities immunocytochemically stained with synaptophysin revealed a significant increase in the asymptomatic cats at 2-3 years postinoculation that correlated negatively with the CD4:CD8 ratios. Random source AIDS cats showed a 34% decrease in synaptophysin-immunoreactive profiles. Glutamate binding in the cortex did not change significantly in the asymptomatic cats (4-7% decline). Thus, experimentally infected specific pathogen-free cats show a loss of cortical neurons similar to what has been observed in postmortem studies of humans infected with HIV. The detection of neuronal loss during the asymptomatic stage of disease and the correlation with the peripheral CD4:CD8 cell ratios indicate that neurodegeneration may progress in parallel with peripheral disease

205. Mrak RE, Griffin WS (1997) The role of chronic self-propagating glial responses in neurodegeneration: implications for long-lived survivors of human immunodeficiency virus. J.Neurovirol. 3:241-246
     Abstract: Within the last decade there has arisen increasing appreciation of the role of glia-derived immune and neurotrophic cytokines, especially Microglia-derived interleukin-1 and astrocyte-derived S100beta, in the pathophysiology of Alzheimer's disease and of neurodegeneration in general. Available evidence now suggests that these neurotrophic and immune cytokines, produced in response to neuronal cell dysfunction or death, may elicit cellular and molecular responses resulting in further activation of glia and glial cytokine secretion, producing a cytokine cycle. In conditions characterized by chronic glial activation this cycle becomes self propagating, promoting further neurodegeneration and subsequent further induction of glial cell activation with production of cytokines. In Alzheimer's disease, for instance, such self-propagation is essential to the progressive accumulation of neuropathological changes that underlie progressive dementia. Conditions that predispose one to Alzheimer-type 'senile' neuropathological changes, and to later development of Alzheimer's disease, also exhibit glial activation and overexpression of glial cytokines, providing further evidence of a pathogenic role for glial activation and cytokine cycle elements in the initiation and propagation of Alzheimer lesions. HIV produces a chronic viral infection of the central nervous system that has been associated with chronic glial activation and overexpression of some of the same cytokines that have been implicated in Alzheimer pathogenesis. These observations, together with established functions of cytokine cycle elements, suggest that chronic HIV infection in sufficiently long-lived HIV-infected individuals might confer additional risk for later development of Alzheimer's disease

206. Mussa M, Preux PM, Debrock C, Chazot-Balcon M, Melaku Z, Druet-Cabanac M, Kayembe K, Dumas M (1997) [HIV-1 cognitive and motor syndrome]. Sante 7:187-193
     Abstract: The central nervous system (CNS) is often affected by HIV-1 infection. Over 40% of AIDS cases present with neurological symptoms and CNS lesion are detected by anatomical and pathological studies in 80 to 90% of AIDS cases. There may be infections and tumors secondary to the immunodeficiency and pathologies may occur directly due to the neurotropism of the virus. Neurological problems associated with HIV-infection include encephalopathies, myelopathies, neuropathies and myopathies. HIV-1-induced encephalopathy may develop at any stages of HIV-1 infection and affects all risk groups equally. Its frequency worldwide is between 4 and 65% among individuals seropositive for HIV-1. The frequencies reported differ between studies due to differences in sampling methods, geographical factors, diagnostic criteria and investigative methods used. The pathogenesis of HIV-1-associated encephalopathy is not understood, but there are several hypotheses. The involvement of HIV-1 infected macrophages and Microglial cells has been demonstrated. Indirect mechanisms such as release of lymphokines (tumor necrosis factor-TNF alpha- and interleukin-1) and neurotoxicity of the HIV envelope protein, gp 120, have also been suggested. This disorder is known as HIV-1-associated cognitive and motor syndrome. It presents clinically as a form of sub-cortical dementia with cognitive problems, motor deficits and behavioral disorders depending on the type and stage of HIV infection. The diagnosis can only be made after all other infections and tumors common in HIV-1 patients have been ruled out by appropriate investigations such as cerebrospinal fluid analysis, cerebral scan and magnetic resonance imaging. Electrophysiological studies, such as evoked responses and electroencephalograms, are particularly useful in its diagnosis. Anatomical examination shows diffuse paleness of the white matter, multi-nucleated giant cells and Microglial nodes. Neuropsychological studies could be of value in diagnosis and in assessing the response to anti-retroviral treatment. There is currently no specific therapy for HIV-1-associated cognitive and motor syndrome. The use of new nucleoside analogue drugs in combination with existing drugs may provide new approaches to managing these patients

207. New DR, Ma M, Epstein LG, Nath A, Gelbard HA (1997) Human immunodeficiency virus type 1 Tat protein induces death by apoptosis in primary human neuron cultures. J.Neurovirol. 3:168-173
     Abstract: Neuronal loss in HIV encephalopathy remains a mystery since HIV-1 productively infects macrophage and Microglia and only rarely infects neurons in the central nervous system. Apoptosis is a mechanism which may account for the loss of neurons in HIV-1 infected brain. Putative toxic factors that result in neuronal cell death in HIV-1 infection include the regulatory protein Tat, since this protein is known to be released from HIV-1 infected cells. Here we show that Tat induces cell death by apoptosis in cultured human fetal neurons producing characteristic morphological and biochemical features associated with apoptosis. These findings suggest that Tat may play an important role as a secreted, soluble neurotoxin in HIV-1 associated dementia

208. Persidsky Y, Buttini M, Limoges J, Bock P, Gendelman HE (1997) An analysis of HIV-1-associated inflammatory products in brain tissue of humans and SCID mice with HIV-1 encephalitis. J.Neurovirol. 3:401-416
     Abstract: The human immunodeficiency virus type 1 (HIV)-associated dementia complex (ADC) is a neuroimmunological disorder fueled by viral replication in mononuclear phagocytes (MP) (brain macrophages and Microglia). The elucidation of MP inflammatory factors involved in neurological dysfunction is pivotal for unraveling pathogenic mechanisms and in developing new therapies for this disease. Recent advances in animal model systems for ADC and its associated encephalitis have provided important insights into how virus-infected macrophages cause brain injury. Indeed, the stereotactic inoculation of HIV infected monocytes into the basal ganglia/cortex of mice with severe combined immunodeficiency disease (SCID) results in pathological features similar to those of human HIV-1 encephalitis (HIVE). We used this SCID model to study the roles of macrophage secretory factors in HIVE. The expression of interleukin-1 (IL-1 beta, IL-6, IL-10), tumor necrosis factors-alpha (TNF alpha), vascular endothelial growth factor (VEGF), and adhesion molecules (E-selectin, intracellular cell adhesion molecule (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1)) in encephalitic brains of mice and humans was evaluated by semi-quantitative polymerase chain reaction (PCR). In SCID mice with HIVE, human and mouse TNF alpha, and mouse IL-6, VEGF, VCAM-1 and E-selectin were expressed at high levels. These results paralleled, to a great extent, those in HIVE brain tissues. Laser scanning confocal microscopy performed to assess the associated neuronal damage showed that microtubule associated protein-2 (MAP-2) immunoreactive dendrites were significantly reduced in both the ipsilateral and contralateral hemispheres of encephalitic mice. These results demonstrate the importance of macrophage inflammatory products in the pathogenesis of HIVE and further validates this model of viral encephalitis in SCID mice

209. Samson M, LaRosa G, Libert F, Paindavoine P, Detheux M, Vassart G, Parmentier M (1997) The second extracellular loop of CCR5 is the major determinant of ligand specificity. J.Biol.Chem. 272:24934-24941
     Abstract: The chemokine receptor CCR5 binds macrophage inflammatory protein (MIP)-1alpha, MIP-1beta, and regulated on activation, normal T-cell expressed and secreted (RANTES), and constitutes the major co-receptor allowing infection of CD4(+) T lymphocytes, macrophages, and Microglial cells by macrophage-tropic strains of human and simian immunodeficiency virus. CCR5 is most closely related to CCR2b, another chemokine receptor that responds to monocyte chemoattractant protein (MCP)-1, MCP-2, MCP-3, and MCP-4. We have investigated by mutagenesis the regions of CCR5 and CCR2b involved in the specificity of binding and functional response to their respective ligands. We demonstrate that the key region of CCR5 involved in its specific interaction with MIP-1alpha, MIP-1beta, and RANTES, and its subsequent activation, lies within the second extracellular loop (and possibly the adjacent transmembrane segments). Conversely, the NH2-terminal domain of CCR2b is responsible for the high affinity binding of MCP-1, but is not sufficient to confer activation of the intracellular cascades. Extracellular loops of the receptor, among which the second loop plays a prominent role, are necessary to achieve efficient signaling of the receptor. These data complement our previous mapping of CCR5 domains functionally involved in the fusion process with the human immunodeficiency virus envelope, and will help in the development of agents able to interfere with the early steps of viral infection

210. Seilhean D, Kobayashi K, He Y, Uchihara T, Rosenblum O, Katlama C, Bricaire F, Duyckaerts C, Hauw JJ (1997) Tumor necrosis factor-alpha, Microglia and astrocytes in AIDS dementia complex. Acta Neuropathol.(Berl) 93:508-517
     Abstract: The pathogenesis of HIV-associated cognitive changes is poorly understood. Cytokines such as tumor necrosis factor-alpha (TNF-alpha) have been postulated to contribute to the mechanism of the neurological complications of HIV infection. One of the effects of TNF-alpha is to induce astrocyte proliferation in vitro. The purpose of this study was to look for a correlation between the expression of TNF-alpha, astrogliosis and the degree of cognitive impairment in 12 prospectively assessed AIDS cases without focal brain lesion, 8 of whom were demented. They were compared with 6 control patients without neurological disease. Neuropathological examination showed myelin pallor in 5 of the 8 demented patients. TNF-alpha expression was detected by immunohistochemistry in the midfrontal cortex, subcortical and deep white matter, and basal ganglia. Not only perivascular macrophages but also some Microglial and endothelial cells were labeled. Most TNF-alpha-positive cells were in close contact with glial fibrillary acidic protein-positive astrocytes. They were more numerous than gp41-positive cells. Their density increased with increasing cognitive impairment and in parallel to the astrogliosis in the frontal cortex, basal ganglia and deep white matter. These findings further support the hypotheses that lesions of the deep white matter, driven by TNF-alpha, are associated with cognitive alteration, and that indirect effects of HIV infection in the brain participate in the development of HIV-associated dementia through a diffuse immune activation, mediated by cytokines

211. Silver B, McAvoy K, Mikesell S, Smith TW (1997) Fulminating encephalopathy with perivenular demyelination and vacuolar myelopathy as the initial presentation of human immunodeficiency virus infection. Arch.Neurol. 54:647-650
     Abstract: OBJECTIVE: To study the neuropathologic features in a case involving a 22-year-old woman in whom a fulminating encephalopathy developed as the initial manifestation of human immunodeficiency virus (HIV) infection. DESIGN: Case report. SETTING: Tertiary care hospital. PATIENT: The patient presented with rapidly progressive mental status, changes, cranial nerve abnormalities, and quadriplegia, which led to her death 5 months later. Serologic tests for HIV were initially indeterminate on Western blot analysis but were positive 1 week later. METHODS: A complete autopsy, including examination of the brain and spinal cord, was performed. Paraffin-embedded sections of the brain and spinal cord were examined using standard histologic staining procedures and immunohistochemical techniques. RESULTS: Neuropathologic examination revealed discrete foci of perivenular demyelination disseminated throughout the brain and spinal cord, as well as severe vacuolar myelopathy. Lesions typical of HIV encephalitis were not present. Human immunodeficiency virus-infected monocytes and Microglia were observed in the vicinity of, but not restricted to, the perivenular demyelinating lesions. No other infectious agents were identified. CONCLUSIONS: The patient's acute encephalopathy was most likely the direct result of a widespread demyelinating process resembling acute disseminated encephalomyelitis. We suggest that the perivenular demyelination may represent an autoimmune reaction, possibly due to a nonspecific viral infection, occurring in the setting of chronic immunosuppression secondary to HIV. Although less likely, we cannot exclude the possibility that HIV could have directly triggered an autoimmune response that caused the acute disseminated encephalomyelitis-like lesions

212. Stephens EB, Galbreath D, Liu ZQ, Sahni M, Li Z, Lamb-Wharton R, Foresman L, Joag SV, Narayan O (1997) Significance of macrophage tropism of SIV in the macaque model of HIV disease. J.Leukoc.Biol. 62:12-19
     Abstract: Microglia, alveolar macrophages, and Langerhans cells are representatives of cells of macrophage lineage that are susceptible to infection with HIV-1 and they play important roles in the pathogenesis of AIDS dementia, lymphoid interstitial pneumonia, and systemic viral invasion from mucosal surfaces, respectively. In contrast, elimination of CD4+ T cells with resultant development of immunosuppression and AIDS is thought to be reflective of the exclusive tropism of the virus for CD4+ T cells. Examination of these concepts in macaques infected with molecularly cloned strains of SIVmac suggested that all strains of the virus are both macrophage- and lymphocyte-tropic and that all aspects of pathogenesis including loss of CD4+ T cells are dependent on infection in both cell types. However, viral clones that caused productive lytic infection in macrophages were less virulent than those which caused persistent nonproductive infection. The former caused subclinical and even immunizing infections, whereas the latter caused activation and productive infection in CD4+ T cells, AIDS, and systemic infection, even after inoculation of the virus on mucosal surfaces. If these findings on SIVmac are relevant to HIV-1 disease, then demonstration that HIV-1 isolates are macrophage-tropic probably does not necessarily correlate with their pathogenic potential

213. Strizki JM, Turner JD, Collman RG, Hoxie J, Gonzalez-Scarano F (1997) A monoclonal antibody (12G5) directed against CXCR-4 inhibits infection with the dual-tropic human immunodeficiency virus type 1 isolate HIV-1(89.6) but not the T-tropic isolate HIV-1(HxB). J.Virol. 71:5678-5683
     Abstract: We used a monoclonal antibody (12G5) directed against an extracellular domain of CXCR-4 to investigate the role of this receptor in infection of immortalized lymphoid cell lines, peripheral blood mononuclear cells (PBMCs), and primary brain Microglia with a dual-tropic strain of human immunodeficiency virus (HIV-1(89.6)) and a T-tropic strain (HIV-1(IIIB)). Addition of antibody 12G5 to cells prior to and during infection with HIV-1(89.6) inhibited p24 production 100- to 10,000-fold in CEMx174 and 174-CD4 cells and about 10-fold in PBMC cultures but had no activity against infection of either monocyte-derived macrophages or brain Microglia. In contrast, 12G5 had little or no effect on infection of CEMx174 cells with HIV-1(IIIB) or HIV-1(HxB). To identify the region of the HIV-1(89.6) envelope that confers sensitivity to 12G5, we used chimeric molecular clones. Chimeras containing the V3 loop region of HIV-1(89.6) were inhibited by 12G5 to the same degree as wild-type HIV-1(89.6) whereas replication of those viruses containing the V3 loop of HIV-1(HxB) was not inhibited by the antibody. A similar pattern was seen in infections of a U87 glioblastoma line that coexpresses CD4 and CXCR-4. Antibody 12G5 was also able to block fusion between HeLa-CD4 cells and CEMx174 cells chronically infected with HIV-1(89.6) but had no effect on fusion mediated by cells chronically infected with HIV-1(IIIB). Taken together, these results suggest that different strains of HIV-1 may interact with different sites on CXCR-4 or may have different binding affinities for the coreceptor

214. Tanabe S, Heesen M, Yoshizawa I, Berman MA, Luo Y, Bleul CC, Springer TA, Okuda K, Gerard N, Dorf ME (1997) Functional expression of the CXC-chemokine receptor-4/fusin on mouse Microglial cells and astrocytes. J.Immunol. 159:905-911
     Abstract: The mRNA for the seven-transmembrane-spanning G protein-coupled receptor fusin/CXCR-4 is expressed in primary mouse astrocyte cultures and the transformed mouse Microglial cell line, N9. Cell surface expression of fusin in these cells was confirmed by staining with a polyclonal anti-fusin Ab. The functional capacity of this chemokine receptor was examined by evaluating the calcium responses following stimulation of glial cells with the CXC-chemokine, stromal-derived cell factor-1alpha (SDF-1alpha). Both astrocytes and Microglial cells mobilized calcium following stimulation with chemically synthesized SDF-1alpha. SDF-1alpha- and carbachol-mediated calcium responses of astrocytes were partially inhibited by treatment with pertussis toxin (PTx), suggesting receptor coupling to a combination of G alpha(i) and other G proteins. In contrast, the calcium responses of Microglial cells to SDF-1alpha were completely PTx sensitive, while responses to carbachol stimulation were PTx resistant. The ability of SDF-1alpha to induce glial cell migration was also examined. Synthetic SDF-1alpha was a potent chemoattractant for mouse Microglial cells at ligand concentrations of 10 to 500 ng/ml; peak responses were noted at 100 ng/ml. In contrast, astrocytes did not migrate toward a gradient of SDF-1alpha. The failure of SDF-1alpha to induce astrocyte migration was specific, as another chemokine, macrophage inflammatory protein-1alpha, triggered astrocyte chemotaxis

215. Wingertsmann L, Chretien F, Authier FJ, Paraire F, Durigon M, Gray F (1997) [Central nervous system lesions in the early stages of HIV infection]. Arch.Anat.Cytol.Pathol. 45:106-117
     Abstract: Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remain neurologically unimpaired during the so-called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, very few neuropathological studies have been conducted in the early pre-AIDS stages, and the natural history of central nervous system changes in HIV-1 infection remains poorly understood. Examination of brains of asymptomatic HIV-1 positive individuals who died accidentally and of rare cases with acute fatal encephalopathy revealing HIV infection, and comparison with experimental simian immunodeficiency virus and feline immunodeficiency virus infections suggest that, invasion of the CNS by HIV-1 occurs at the time of primary infection and induces an immunological process in the central nervous system. This includes an inflammatory T-cell reaction with vasculitis and leptomeningitis, and immune activation of brain parenchyma with increased number of Microglial cells, upregulation of major histocompatibility complex class II antigens and local production of cytokines. Myelin pallor and gliosis of the white matter are usually found and are likely to be the consequence of opening of the blood-brain barrier due to vasculitis; direct damage to oligodendrocytes by cytokines may also be involved. These white matter changes may explain, at least partly, the early cerebral atrophy observed, by magnetic resonance imaging, in asymptomatic HIV-1 carriers. In contrast, cortical damage seems to be a late event in the course of HIV-1 infection. There is no significant neuronal loss at the early stages of the disease, no accompanying increase in glial fibrillary acid protein staining in the cortex, and only exceptional neuronal apoptosis. Although HIV-1 proviral DNA may be demonstrated in a number of brains, viral replication remains very low during the asymptomatic stage of HIV-1 infection. This makes it likely that, although opening of the blood brain barrier may facilitate viral entry into the brain, specific immune responses including both neutralising antibodies and cytotoxic T-lymphocytes, continuously inhibit viral replication at this stage

216. Zenger E, Tiffany-Castiglioni E, Collisson EW (1997) Cellular mechanisms of feline immunodeficiency virus (FIV)-induced neuropathogenesis. Front Biosci. 2:d527-d537
     Abstract: The high incidence of neurologic dysfunction from human immunodeficiency virus (HIV) infection has heightened interest in neuropathogenesis of other lentiviruses, including that associated with feline immunodeficiency virus (FIV). Both HIV and FIV efficiently enter the central nervous system and cause primary neurological disease that is not attributable to opportunistic infections or systemic disease. Cells in the brain infected by FIV are similar to those observed in HIV infection, both viruses infect macrophages, Microglia, and astrocytes. Although substantial neuronal loss can occur in the cortex of HIV- or FIV-infected patients, most studies agree that neurons are not infected and indirect mechanisms of neurotoxicity are postulated. This review describes recent information on the neuropathogenesis of FIV and how this information correlates with what is known about the neuropathogenesis of HIV. Although the pathogenesis of neurological dysfunction in HIV- and FIV-infected patients is far from clear, it is becoming increasingly evident that the relationship between lentivirus presence in the brain and neurological signs is not straightforward and cannot be explained by simple cytolytic infection. The observed neurologic dysfunction is likely multifactorial and complex involving an intricate web of subcellular pathways and neurotoxic factors interacting with multiple cell types

217. Zheng J, Gendelman HE (1997) The HIV-1 associated dementia complex: a metabolic encephalopathy fueled by viral replication in mononuclear phagocytes. Curr.Opin.Neurol. 10:319-325
     Abstract: HIV enters the brain soon after virus exposure but elicits profound neurological deficits in infected humans years later usually during progressive immunosuppression and the development of the acquired immune deficiency syndrome. The neurological disease complex associated with virus infection occurs in a large proportion of infected patients and is commonly referred to as HIV-1 associated dementia complex. The neuropathogenesis of central nervous system/viral infection revolves around mononuclear phagocytes (brain macrophage/Microglial) infection and immune activation in brain. Macrophages secrete neurotoxic factors that elicit neuronal injury and inevitably death leading to the constellation of cognitive and motor impairments common during progressive disease. Neurotoxic factor production requires virus entry and replication, the evolution/selection of neurovirulent HIV-1 strains and the production of viral and cellular immune factors injurious to human neurons. Interestingly, neurological deficits, the HIV-1 associated neuropathology and viral replication disease are not always associated. This has led to the notion that viral replication induces the autocrine/paracrine production of cellular/viral factors leading to a metabolic encephalopathy. Anti-retroviral and anti-inflammatory therapies should prove increasingly beneficial for treatment and, ultimately, reversal of HIV-1 associated dementia complex in the affected human host

218. Albright AV, Strizki J, Harouse JM, Lavi E, O'Connor M, Gonzalez-Scarano F (1996) HIV-1 infection of cultured human adult oligodendrocytes. Virology 217:211-219
     Abstract: The mechanism through which HIV-1 causes HIV dementia (HIVD) is not well understood. Myelin pallor is a common pathological finding in HIVD and could be explained by a direct infection of oligodendrocytes or interaction with HIV-1 gp 120. To determine if oligodendrocytes could be infected by HIV-1, we purified oligodendrocytes from adult human brain tissues obtained from temporal lobe resections. These cells were exposed to HIV-1 and infectivity was assayed by detection of p24gag antigen, PCR amplification, and cocultivation with CD4+ cells. These results indicate that HIV-1(IIIB and BaL) and one of four primary isolates tested can infect oligodendrocytes, resulting in the production of infectious virus. Furthermore, in an experiment that mimics a potential in vivo scenario, infected Microglia were able to transmit virus to oligodendrocytes in a trans-well culture system. These experiments indicate that oligodendrocyte infection should be considered in studying the pathophysiology of HIVD

219. Arribas JR, Storch GA, Clifford DB, Tselis AC (1996) Cytomegalovirus encephalitis. Ann.Intern.Med. 125:577-587
     Abstract: PURPOSE: To review the pathologic and clinical features of and establish the frequency of cytomegalovirus encephalitis in adults and to review the methods available for diagnosis and treatment. DATA SOURCE: MEDLINE search of all English-language articles from January 1965 to August 1995. STUDY SELECTION: Articles dealing with cytomegalovirus infection of the brain in adults. We also reviewed all unselected autopsies of these populations to establish the frequency of cytomegalovirus encephalitis in recipients of organ transplants and in patients infected with the human immunodeficiency virus (HIV). DATA EXTRACTION: Epidemiologic and pathologic characteristics, clinical manifestations, diagnostic methods, pathogenetic mechanisms, and use of anticytomegalovirus treatments. DATA SYNTHESIS: Of 676 patients receiving a diagnosis of cytomegalovirus encephalitis, 574 (85%) were infected with HIV, 81 (12%) had other causes of immunosuppression, and 21 (3%) were otherwise healthy. Cytomegalovirus encephalitis was confirmed during autopsy in 12% of HIV-infected patients and 2% of transplant recipients. The most common lesion was Microglial nodule encephalitis, but the clinical findings corresponding to this pathologic entity are not well defined. In contrast, the pathologic entity of cytomegalovirus ventriculoencephalitis, found almost exclusively in patients with advanced HIV infection, has distinct clinical features that allow recognition even in patients with HIV encephalopathy. Polymerase chain reaction has been shown to be useful for diagnosis of cytomegalovirus encephalitis. CONCLUSIONS: Cytomegalovirus encephalitis is an important opportunistic infection in HIV-infected patients but is rarely recognized in other groups. Cytomegalovirus ventriculoencephalitis has emerged as a unique entity in patients with advanced HIV infection. Recent developments in diagnostic techniques allow early recognition and may make more aggressive approaches to therapy possible

220. Bagasra O, Lavi E, Bobroski L, Khalili K, Pestaner JP, Tawadros R, Pomerantz RJ (1996) Cellular reservoirs of HIV-1 in the central nervous system of infected individuals: identification by the combination of in situ polymerase chain reaction and immunohistochemistry. AIDS 10:573-585
     Abstract: OBJECTIVES: The majority of HIV-1-infected individuals manifest a plethora of central nervous system (CNS) diseases unrelated to opportunistic infections, including AIDS dementia complex, encephalitis, and various other disorders of the CNS. The present study sought to evaluate the cellular reservoirs and expression patterns of HIV-1 in brain tissue to gain further understanding of HIV-1 neuropathogenesis. DESIGN: CNS tissue, obtained post-mortem from 22 patients with AIDS and four HIV-1-seronegative controls, was analyzed. METHODS: CNS samples were evaluated using a combination of in situ DNA polymerase chain reaction (PCR), reverse transcriptase (RT)-initiated in situ PCR, and immunohistochemistry. By utilizing this triple-staining methodology, HIV-1 proviral DNA and HIV-1-specific mRNA can be identified at the single cell level. RESULTS: HIV-1 was detected in all 22 AIDS brain specimens and in none of the four brains from HIV-1-seronegative individuals. The most commonly infected cells in AIDS brains were Microglia cells and macrophages, but variable levels of HIV-1 infections were demonstrated in many of the major histological cell types within the CNS, including neurons, microvascular endothelial cells (MVEC) and astrocytes. The presence of HIV-1-infected cells was not uniform with infected cells unevenly distributed throughout the brain parenchyma. The degree of HIV-1 mRNA expression varied from 39-65% of the cells in the CNS harboring HIV-1 provirus. Choroid plexus and MVEC exhibited relatively high levels of productive infection. CONCLUSION: These findings demonstrate that several cell types in the CNS, in addition to Microglia or macrophages, may become infected with HIV-1 in vivo with variable levels of HIV-1 mRNA expression. The diverse cellular reservoirs for HIV-1 in the CNS may be critically linked to the molecular mechanisms involved in HIV-1 neuropathogenesis. In addition, in vivo infection of MVEC, and possibly cells in the choroid plexus, may directly contribute to penetration of the blood-brain barrier by HIV-1

221. Boelaert JR, Weinberg GA, Weinberg ED (1996) Altered iron metabolism in HIV infection: mechanisms, possible consequences, and proposals for management. Infect.Agents Dis. 5:36-46
     Abstract: The progression of human immunodeficiency virus (HIV) infection toward its more advanced stages is accompanied by increasing body iron stores. Iron accumulates in macrophages, Microglia, endothelial cells, and myocytes. The iron burden is especially heavy in bone marrow, brain white matter, muscle, and liver. Excess iron potentially enhances oxidative stress, impairs several already compromised immune defense mechanisms, and directly promotes the growth of microbial cells. Thus, we hypothesize that the prevention (or at least, reduction) of iron loading might slow the progression of the infectious complications of HIV infection, and perhaps indirectly, the HIV infection itself. A twofold strategy is proposed, consisting of (a) limitation of iron intake through the alimentary, parenteral, and respiratory routes, and (b) possibly the use of iron chelator drugs that could decrease the iron burden, redistribute the metal to the erythroblasts, and suppress the growth of microorganisms. This approach is still to be considered as hypothetical. However, the available data suggest that there is an urgent need for careful clinical studies to clarify the role of iron status on the course of HIV infection

222. Bradl M, Linington C (1996) Animal models of demyelination. Brain Pathol. 6:303-311
     Abstract: Demyelination is a pathological feature that is characteristic of many diseases of the central nervous system (CNS) including multiple sclerosis (MS), sub-acute sclerosing panencephalomyelitis (SSPE), metachromatic leukodystrophy and Pelizaeus-Merzbacher disease. While demyelination is a pathological end-point that is common to all of these diseases, the cellular and molecular mechanisms responsible for this pathology are very different . These range from genetic defects that affect lipid metabolism in the leukodystrophies, cytopathic effects of viral infection in SSPE to the action of immunological effector mechanisms in MS and the viral encephalopathies. Irrespective of the initial cause of myelin degradation, many of these disorders are associated with some degree of CNS inflammation, as indicated by the local activation of Microglia, recruitment of macrophages or the intrathecal synthesis of immunoglobulin. Many of these phenomena are now being duplicated in animal models, providing not only new insights into the pathogenesis of human demyelinating diseases , but also unexpected interrelationships between the immune response in the CNS and the pathogenesis of diseases such as Alzheimers disease and HIV encephalopathy. Autoimmune mediated models of inflammatory demyelinating CNS disease have proved particularly valuable in this respect as they allow the effects of defined immune effector mechanisms to be studied in the absence of CNS infection

223. Chiang CS, Powell HC, Gold LH, Samimi A, Campbell IL (1996) Macrophage/Microglial-mediated primary demyelination and motor disease induced by the central nervous system production of interleukin-3 in transgenic mice. J.Clin.Invest 97:1512-1524
     Abstract: Activated macrophage/Microglia may mediate tissue injury in a variety of CNS disorders. To examine this, transgenic mice were developed in which the expression of a macrophage/Microglia activation cytokine, interleukin-3 (IL-3), was targeted to astrocytes using a murine glial fibrillary acidic protein fusion gene. Transgenic mice with low levels of IL-3 expression developed from 5 mo of age, a progressive motor disorder characterized at onset by impaired rota-rod performance. In symptomatic transgenic mice, multi-focal, plaque-like white matter lesions were present in cerebellum and brain stem. Lesions showed extensive primary demyelination and remyelination in association with the accumulation of large numbers of proliferating and activated foamy macrophage/Microglial cells. Many of these cells also contained intracisternal crystalline pole-like inclusions similar to those seen in human patients with multiple sclerosis. Mast cells were also identified while lymphocytes were rarely, if at all present. Thus, chronic CNS production of low levels of IL-3 promotes the recruitment, proliferation and activation of macrophage/Microglial cells in white matter regions with consequent primary demyelination and motor disease. This transgenic model exhibits many of the features of human inflammatory demyelinating diseases including multiple sclerosis and HIV leukoencephalopathy

224. Di Stefano M, Wilt S, Gray F, Dubois-Dalcq M, Chiodi F (1996) HIV type 1 V3 sequences and the development of dementia during AIDS. AIDS Res.Hum.Retroviruses 12:471-476
     Abstract: The most frequent neurological complication of AIDS is a dementia-like syndrome. Power and collaborators (J Virol 1994; 68:4643-4649) have reported an association between the clinical signs of AIDS dementia and the amino acid composition of two positions (305 and 329) within the V3 region of HIV-1 strains amplified from brain tissue. Similarly, we analyzed position 305 in the V3 region of HIV-1 present in the brain or cerebrospinal fluid of 25 nondemented subjects at different clinical stages of HIV-1 infection. Our results are, however, at variance with the findings presented by Power and colleagues. Histidine, found to be common among sequences derived from demented patients, was also present in the majority (16 of 25) of nondemented patients analyzed by us. In the hands of Power and colleagues, sequences derived from nondemented patients contained proline at position 305. None of our patients had proline in this position. We also asked the question whether the presence of a specific amino acid at position 305 of the V3 loop is linked to an increased capacity of HIV-1 isolates to infect primary Microglial cells, the major target cell for HIV-1 infection in the brain. Primary HIV-1 isolates derived from blood and cerebrospinal fluid of five patients, two asymptomatic and three AIDS patients, were used to infect Microglia cell cultures. Infection was monitored by syncytium formation and by p24 antigen release in the culture supernatant. All but one of the paired blood/CSF isolates replicated in human brain cultures. Replication occurred independently from the amino acid present at position 305 of the V3 region of the viral envelope. Our results indicate that the majority of HIV-1 isolates, even derived during the asymptomatic stage, have the capacity to infect Microglial cells. The relevance of viral envelope sequences in determining tropism for Microglial cells and development of neurological symptoms remains an open question

225. Fine SM, Angel RA, Perry SW, Epstein LG, Rothstein JD, Dewhurst S, Gelbard HA (1996) Tumor necrosis factor alpha inhibits glutamate uptake by primary human astrocytes. Implications for pathogenesis of HIV-1 dementia. J.Biol.Chem. 271:15303-15306
     Abstract: Human immunodeficiency virus (HIV) infection is commonly associated with neurological disease that occurs in the apparent absence of extensive infection of brain cells by HIV, suggesting that indirect mechanisms account for neuropathogenesis in the CNS, perhaps including changes in the normal neuroprotective functions of astrocytes. To test this hypothesis, we examined the effect of the pro-inflammatory cytokine, tumor necrosis factor alpha (TNFalpha), produced by HIV-1-infected macrophages and Microglia, on glutamate transport by primary human fetal astrocytes (PHFAs). A dose-dependent inhibition of high affinity glutamate uptake sites was observed 12-24 h after addition of exogenous recombinant human TNFalpha to PHFAs. This effect was specific since it was blocked by a neutralizing monoclonal antibody directed against TNFalpha. Furthermore, the inhibitory effect was reproduced by a monoclonal antibody that is an agonist at the 55-kDa TNF receptor. These results suggest that the neurotoxic effects of TNFalpha may be due in part to its ability to inhibit glutamate uptake by astrocytes, which in turn may result in excitotoxic concentrations of glutamate in synapses

226. Gehrmann J (1996) Microglia: a sensor to threats in the nervous system? Res.Virol. 147:79-88
     Abstract: The parenchymal Microglia are now believed to settle the CNS antenatally, being derived from a bone marrow precursor cell. Based on developmental and pathophysiological studies, at least four different types of parenchymal Microglia can be distinguished: (i) the amoeboid Microglia which are mainly found perinatally in white matter areas, such as the corpus callosum, i.e. the so-called "fountains of Microglia", (ii) the ramified, resting Microglia in the adult CNS, (iii) the activated, non-phagocytic Microglia found in areas of secondary reaction due to nerve transection and (iv) the phagocytic Microglia, found in areas of trauma, infection or neuronal necrosis. In addition, there are perivascular cells enclosed in the basal lamina which have a high turnover with a bone marrow precursor pool. While the function of resting Microglia is still largely unknown, it is clear from observations in neuropathology that Microglia are among the first cell types in the brain to respond to injuries. Their reaction pattern to injury has been termed a graded response, since the transformation of resting cells into phagocytes is under strict control in vivo. Microglial activation is a key cellular response in many infectious, inflammatory, traumatic, neoplastic, ischaemic and degenerative conditions in the CNS. In HIV encephalitis, the Microglial involvement is striking, and approximately 25% of Microglia contain viral DNA or RNA. Based on natural homing mechanisms with bone marrow precursor cells, HIV-infected monocytes/macrophages may home at an early stage to the CNS perivascular space and eventually spread the infection to resident Microglia in the CNS which may be difficult to reach by pharmacological intervention. Further understanding of the mechanisms regulating Microglial proliferation and activation in vivo may help to develop therapies targeting the potentially harmful Microglial response in the injured CNS

227. Glass JD, Johnson RT (1996) Human immunodeficiency virus and the brain. Annu.Rev.Neurosci. 19:1-26
     Abstract: Human immunodeficiency virus (HIV) infects the nervous system in the majority of patients, causing a variety of neurological syndromes throughout the course of the disease. This review focuses on the effects of HIV in the central nervous system, with an emphasis on HIV-associated dementia. HIV-associated dementia occurs in a subset of patients with AIDS; it is unclear why these patients and not all patients develop the disease. Several factors are likely to be involved in the pathogenesis of HIV-associated dementia, including neurotoxins released from the virus and/or infected macrophages and Microglia, immunologic dysregulation of macrophage function, and specific genetic strains of HIV. These factors, and their possible interactions, are discussed

228. Gray F, Scaravilli F, Everall I, Chretien F, An S, Boche D, Adle-Biassette H, Wingertsmann L, Durigon M, Hurtrel B, Chiodi F, Bell J, Lantos P (1996) Neuropathology of early HIV-1 infection. Brain Pathol. 6:1-15
     Abstract: Early HIV-1 invasion of the central nervous system has been demonstrated by many cerebrospinal fluid studies; however, most HIV-1 carriers remain neurologically unimpaired during the so called "asymptomatic" period lasting from seroconversion to symptomatic AIDS. Therefore, neuropathological studies in the early pre-AIDS stages are very few, and the natural history of central nervous system changes in HIV-1 infection remains poorly understood. Examination of brains of asymptomatic HIV-1 positive individuals who died accidentally and of rare cases with acute fatal encephalopathy revealing HIV infection, and comparison with experimental simian immunodeficiency virus and feline immunodeficiency virus infections suggest that, invasion of the CNS by HIV-1 occurs at the time of primary infection and induces an immunological process in the central nervous system. This includes an inflammatory T-cell reaction with vasculitis and leptomeningitis, and immune activation of brain parenchyma with increased number of Microglial cells, upregulation of major histocompatibility complex class II antigens and local production of cytokines. Myelin pallor and gliosis of the white matter are usually found and are likely to be the consequence of opening of the blood brain barrier due to vasculitis; direct damage to oligodendrocytes by cytokines may also interfere. These white matter changes may explain, at least partly, the early cerebral atrophy observed, by magnetic resonance imaging, in asymptomatic HIV-1 carriers. In contrast, cortical damage seems to be a late event in the course of HIV-1 infection. There is no significant neuronal loss at the early stages of the disease, no accompanying increase in glial fibrillary acid protein staining in the cortex, and only exceptional neuronal apoptosis. Although HIV-1 proviral DNA may be demonstrated in a number of brains, viral replication remains very low during the asymptomatic stage of HIV-1 infection. This makes it likely that, although opening of the blood brain barrier may facilitate viral entry into the brain, specific immune responses including both neutralising antibodies and cytotoxic T-lymphocytes, continuously inhibits viral replication at that stage

229. Kibayashi K, Mastri AR, Hirsch CS (1996) Neuropathology of human immunodeficiency virus infection at different disease stages. Hum.Pathol. 27:637-642
     Abstract: The authors studied the brains of 471 adults infected with human immunodeficiency virus type 1 (HIV-1): 123 asymptomatic carriers, 127 in an early stage of acquired immunodeficiency syndrome (AIDS) with pulmonary tuberculosis or bacterial infections, and 221 in fully developed AIDS with opportunistic infections or neoplasms. Lymphocyte infiltration of the leptomeninges and of perivascular spaces occurred at all stages, but the frequency was significantly higher in asymptomatic carriers. Microglial nodules appeared at all stages of disease; they were not an early indicator of HIV encephalitis (HIVE). The incidence of HIVE was unrelated to the stage of AIDS, suggesting that HIVE occurs before opportunistic infections and neoplasms. Drug abuse, such as cocaine and opiates, may enhance HIV replication and increase the incidence of HIVE in the early stage of AIDS. Opportunistic infections or lymphoma involved only the brain in 31.2% of persons with fully developed AIDS. Conversely, opportunistic infections or neoplasms involved only organs other than the brain in 55.7% of persons with fully developed AIDS. In 13.1% of persons with fully developed AIDS, opportunistic infections or neoplasms involved the brain and other organs. Multiple intracranial opportunistic infections and lymphoma coexisted in 4.1% of persons with fully developed AIDS. The authors identified cerebrovascular disease in 10.6% of asymptomatic carriers, 7.1% of early AIDS, and 5.0% of fully developed AIDS. The observed sequence of abnormalities may be useful in understanding the progression of HIV disease in the brain

230. Kong LY, Wilson BC, McMillian MK, Bing G, Hudson PM, Hong JS (1996) The effects of the HIV-1 envelope protein gp120 on the production of nitric oxide and proinflammatory cytokines in mixed glial cell cultures. Cell Immunol. 172:77-83
     Abstract: Although the neurotoxicity induced by the HIV envelope protein, gp120, has been demonstrated to require the presence of glial cells (Microglia/astrocytes), the mechanisms for the gp120-induced neurotoxicity are not well understood. Moreover, the neurotoxic potencies of gp120s obtained from various HIV isolates are different. Since nitric oxide (NO) and proinflammatory cytokines (TNF-alpha, IL-1, IL-6) produced by glial cells have been involved in the neuropathogenesis of various diseases, this study examined the effects of gp120 obtained from two strains, HIV-1IIIB and HIV-1SF2, of the HIV-1 virus on the production of NO, TNF-alpha, IL-1 alpha, IL-1 beta, and IL-6 in murine primary mixed glial cell cultures. The glial cells exposed to HIV-1IIIB gp120 released NO, TNF-alpha, and IL-6 in a dose-dependent manner, whereas IL-1 alpha and IL-1 beta were undetectable. The cells exposed to HIV-1SF2 gp120 increased the release of IL-6 only. The gp120-induced effects were significantly enhanced by priming glial cells with IFN-gamma. To investigate the cellular sources and mechanisms of the gp120-induced IL-6 production, in situ hybridization with mRNA for IL-6 was performed in HIV-1IIIB gp120- or HIV-1SF2 gp120-stimulated Microgliaenriched or astrocyte-enriched cultures. HIV-1IIIB gp120 or HIV-1SF2 gp120 induced the expression of IL-6 mRNA in both Microglia-enriched and astrocyte-enriched cultures, indicating that both Microglia and astrocytes produce IL-6, and that the transcriptional regulation is involved in the gp120-induced IL-6 production. Taken together, these results demonstrate that the production of NO, TNF-alpha, IL-1, or IL-6 from glial cells is differentially regulated by HIV-1IIIB gp120 and HIV-1SF2 gp120. These results may provide insights into the roles of NO and proinflammatory cytokines in the neurotoxicity of gp120s and the neuropathology of different strains of HIV-1 viruses

231. Lane JH, Sasseville VG, Smith MO, Vogel P, Pauley DR, Heyes MP, Lackner AA (1996) Neuroinvasion by simian immunodeficiency virus coincides with increased numbers of perivascular macrophages/Microglia and intrathecal immune activation. J.Neurovirol. 2:423-432
     Abstract: During peak viremia and initial antibody response, rhesus macaques infected with pathogenic and nonpathogenic isolates of SIV show distinct differences in viral load and tissue distribution. Animals infected with pathogenic isolates of SIV invariably have virus in the CSF and brain parenchyma by two weeks postinoculation, whereas animals infected with nonpathogenic isolates do not. Mechanisms underlying neuroinvasion by SIV and HIV are unknown, but recruitment of latently infected mononuclear cells from the peripheral circulation (Trojan horse theory) is frequently proposed. Circulating monocytes, from which perivascular macrophage/Microglia are derived, are a likely vehicle for cell-associated transport of virus across the blood-brain barrier. This transport and the kinetics of perivascular macrophage/Microglial turnover in the CNS likely depend on endothelial and leukocyte adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1), which has previously been shown to be upregulated on cerebrovascular endothelium in SIV encephalitis. To investigate the role of peripheral monocyte recruitment into the perivascular macrophage/Microglial cell pool at the time of initial viral neuroinvasion, we examined the temporal relationships among perivascular macrophage/Microglia density, endothelial VCAM-1 expression and localization of viral nucleic acid in the CNS of macaques acutely infected with pathogenic and nonpathogenic molecular clones of SIV. The concentration of CSF quinolinic acid, a marker of intrathecal immune and macrophage activation, was examined concurrently. We found that significant increases in the density of perivascular macrophages/Microglia coincided with viral neuroinvasion and marked elevations in CSF quinolinic acid. Furthermore, combined in situ hybridization and immunohistochemistry demonstrated that infected perivascular cells were macrophages/Microglia. These findings provide evidence suggesting that neuroinvasion occurs through an influx of infected monocytes which take up residence in the CNS as perivascular macrophages/Microglia. VCAM-1 expression, however, was not clearly correlated with these events, thus its contribution to initial viral neuroinvasion is unclear

232. Lane TE, Buchmeier MJ, Watry DD, Fox HS (1996) Expression of inflammatory cytokines and inducible nitric oxide synthase in brains of SIV-infected rhesus monkeys: applications to HIV-induced central nervous system disease. Mol.Med. 2:27-37
     Abstract: BACKGROUND: Human immunodeficiency virus type 1 (HIV-1) infection of the central nervous system (CNS) can lead to severe impairments in cognition, behavior, and motor skills. The mechanism(s) by which HIV-1 induces CNS disease are not well understood. Recent evidence suggests that expression of inducible nitric oxide synthase (iNOS) and nitric oxide (NO) may contribute to HIV-1-induced neurologic disease. We sought to determine if these factors were present in the CNS of rhesus monkeys with simian immunodeficiency virus (SIV)-induced CNS disease. MATERIALS AND METHODS: Total NO production in cerebral spinal fluid (CSF) from infected monkeys was determined by measuring nitrite (NO2-) and nitrate (NO3-) (stable NO degradation products) utilizing Greiss reagents. In situ hybridization revealed iNOS, interferon-gamma (IFNgamma), and interleukin 1 beta (IL-1 beta) mRNA in the brains of SIV-infected monkeys. Microglia were isolated from animals infected with SIV. Following stimulation with LPS, induction of iNOS mRNA in isolated Microglia was analyzed by reverse transcriptase-polymerase chain reaction. RESULTS: Serial CSF samples from an SIV-infected monkey reveal increased levels of NO2-/NO3-. In situ hybridization demonstrated iNOS, IFN gamma, and IL-1 beta mRNAs in post-mortem brain tissue of SIV-infected monkeys. Furthermore, stimulated Microglia from an SIV-infected monkey could produce iNOS mRNA. CONCLUSIONS: The presence of iNOS in the brain and NO2-/NO3- in the CSF indicates that NO is produced in the CNS of SIV-infected monkeys. The data suggest that iNOS and NO may be contributing to SIV-induced CNS disease

233. Lee SC, Dickson DW, Casadevall A (1996) Pathology of cryptococcal meningoencephalitis: analysis of 27 patients with pathogenetic implications. Hum.Pathol. 27:839-847
     Abstract: In this autopsy series of cryptococcal meningoencephalitis (CME), the authors analyzed neuropathologic lesions in 13 human immunodeficiency virus (HIV) and 14 non-HIV-related cases. Most non-HIV patients did not have immunosuppressive predisposing illness. Analysis of pathological findings revealed significant differences in the inflammatory response to CME in patients with and without HIV infection. None of the acquired immunodeficiency syndrome (AIDS) patients had granulomatous inflammation, whereas most non-HIV-associated cases had granulomas, supporting a role for cell-mediated immunity in CME. Lymphocytic infiltrate in both groups consisted of T cells (CD45RO+). In some non-HIV-associated cases, CME was undiagnosed and untreated. In most HIV-associated cases, CME had an encephalitic component, resulting in grossly or microscopically visible accumulations of fungi within the brain parenchyma, whereas in non-HIV-associated cases, CME was often confined to the subarachnoid space and large perivascular spaces (Virchow-Robin spaces). In non-HIV-associated cases, yeast forms were fewer and showed a more limited distribution. In contrast, many extracellular fungi were present in many cases of HIV-associated CME. The principal reactive cell in CME in AIDS was brain macrophages and Microglia, especially those in the perivascular and juxtavascular locations. Reactive astrocytes were limited to large destructive lesions and subpial regions. In several patients with HIV-associated CME, large parenchymal cryptococcomas contained Crytococcus neoformans (CN) with cell wall pigmentation, suggestive of melanin. The authors suggest that in AIDS patients altered immune functions allow CN to accumulate within the brain, predominantly extracellularly, and that deficient macrophage/Microglial effector function may be responsible for the altered pathology. In addition, coexisting CNS processes in HIV-associated CME may contribute to the altered pathology. The authors conclude that cryptococcal meningitis is not a disease limited to the cerebrospinal fluid (CSF) space but affects the brain more significantly than suspected. Therapeutic strategies that enhance the effector function of glial cells at the CNS-CSF barrier may be useful for improving the response to therapy

234. Lipton SA (1996) Similarity of neuronal cell injury and death in AIDS dementia and focal cerebral ischemia: potential treatment with NMDA open-channel blockers and nitric oxide-related species. Brain Pathol. 6:507-517
     Abstract: Using in vitro models, our laboratory in collaboration with those of Pierluigi Nicotera (University of Konstanz, Germany) and Stan Orrenius (Karolinska Institute) has recently shown that fulminant insults to the nervous system from excitotoxins or free radicals result in neuronal cell death from necrosis, while more subtle insults result in delayed apoptosis. Over the past dozen or so years, mounting evidence has suggested that excitotoxins, such as glutamate, result in neuronal cell death after stroke. More recent evidence has suggested that in addition to necrotic cell death in the ischemic core, a number of neurons may also undergo apoptosis. Thus, the hypothesis that intense injury leads to necrosis while mild insult (perhaps in the penumbra) leads to apoptosis may hold in focal cerebral ischemia. Another neurological malady with mounting evidence for a pathogenesis that is mediated at least in part by excitotoxins is HIV-1-associated cognitive/motor complex (originally termed the AIDS Dementia Complex and, for convenience, designated here AIDS dementia). AIDS dementia appears to be associated with several neuropathological abnormalities, including giant cell formation by Microglia, astrogliosis, and neuronal injury or loss. Recently, neuronal and other cell injury in AIDS brains has been shown to result in apoptotic-like cell death. How can HIV-1 result in neuronal damage if neurons themselves are only rarely, if ever, infected by the virus? Experiments from several different laboratories, including our group in collaboration with that of Howard Gendelman (University of Nebraska Medical Center), have lent support to the existence of HIV- and immune-related toxins in a variety of in vitro and in vivo paradigms. In one recently defined pathway to neuronal injury, HIV-infected macrophages/ Microglia as well as macrophages activated by HIV-1 envelope protein gp120 appear to secrete excitants/ neurotoxins. These substances may include arachidonic acid, platelet-activating factor, free radicals (NO. and O2.-), glutamate, quinolinate, cysteine, cytokines (TNF-alpha, IL1-beta, IL-6), amines, and as yet unidentified factors emanating from stimulated macrophages and possibly reactive astrocytes. A final common pathway for neuronal susceptibility appears to be operative, similar to that observed in stroke and several neurodegenerative diseases. This mechanism involves excessive activation of N-methyl-D-aspartate (NMDA) receptor-operated channels, with resultant excessive influx of Ca2+ and the generation of free radicals, leading to neuronal damage. With the very recent development of clinically-tolerated NMDA antagonists, as discussed here, there is hope for future pharmacological intervention

235. Makrigeorgi-Butera M, Hagel C, Laas R, Puschel K, Stavrou D (1996) Comparative brain pathology of HIV-seronegative and HIV-infected drug addicts. Clin.Neuropathol. 15:324-329
     Abstract: Early stages of infection with human immunodeficiency virus (HIV) were studied in HIV-seropositive drug addicts. Since heroin users are immunocompromized even in the absence of HIV infection, the aim of the present study was to compare the morphological al