Plasma CXCL10 correlates with HAND in HIV-infected women.

HIV-associated neurocognitive disorder (HAND) is characterized by chronic immune activation. We aimed to identify biomarkers associated with HAND and to investigate their association with cognitive function and sex, in a homogenous cohort of HIV-infected (HIV+) young adults, parenterally infected during early childhood. One hundred forty-four HIV+ Romanian participants (51% women) without major confounders underwent standardized neurocognitive and medical evaluation in a cross-sectional study. IFN-γ, IL-1ß, IL-6, CCL2, CXCL8, CXCL10, and TNF-α were measured in plasma in all participants and in cerebrospinal fluid (CSF) in a subgroup of 56 study participants. Biomarkers were compared with neurocognitive outcomes, and the influence of sex and HIV disease biomarkers was assessed. In this cohort of young adults (median age of 24 years), the rate of neurocognitive impairment (NCI) was 36.1%. Median current CD4+ count was 479 cells/mm3 and 36.8% had detectable plasma viral load. Women had better HIV-associated overall status. In plasma, controlling for sex, higher levels of IL-6 and TNF-α were associated with NCI (p < 0.05). Plasma CXCL10 showed a significant interaction with sex (p = 0.02); higher values were associated with NCI in women only (p = 0.02). Individuals with undetectable viral load had significantly lower plasma CXCL10 (p < 0.001) and CCL2 (p = 0.02) levels, and CSF CXCL10 (p = 0.01), IL-6 (p = 0.04), and TNF-α (p = 0.04) levels. NCI in young men and women living with HIV was associated with higher IL-6 and TNF-α in plasma, but not in the CSF. CXCL10 was identified as a biomarker of NCI specifically in women with chronic HIV infection.

Latent toxoplasmosis is associated with neurocognitive impairment in young adults with and without chronic HIV infection.

We evaluated the impact of latent toxoplasmosis (LT) on neurocognitive (NC) and neurobehavioural functioning in young adults with and without chronic HIV infection, using a standardised NC test battery, self-reported Beck Depression Inventory, Frontal System Behavior Scale, MINI-International Neuropsychiatric Interview and risk-assessment battery. 194 young adults (median age 24years, 48.2% males) with chronic HIV infection (HIV+) since childhood and 51 HIV seronegative (HIV-) participants were included. HIV+ individuals had good current immunological status (median CD4: 479 cells/µl) despite a low CD4 nadir (median: 93 cells/µl). LT (positive anti-Toxoplasma IgG antibodies) was present in one third of participants. The impairment rates in the HIV- with and without Toxo were not significantly different (p=0.17). However, we observed an increasing trend (p<0.001) in impairment rates with HIV and LT status: HIV-/LT- (6.1%); HIV-/LT+ (22%), HIV+/LT- (31%), HIV+/LT+ (49%). In a multivariable analysis using the entire study group there were main effects on cognition for HIV and also for LT. Within the HIV+ group LT was associated with worse performance globally (p=0.006), in memory (p=0.009), speed of information processing (p=0.01), verbal (p=0.02) and learning (p=0.02) domains. LT was not associated with depressive symptoms, frontal systems dysfunction or risk behaviors in any of the groups. HIV participants with lower Toxoplasma antibody concentration had worse NC performance, with higher GDS values (p=0.03) and worse learning (p=0.002), memory (p=0.006), speed of information processing (p=0.01) T scores. Latent Toxoplasmosis may contribute to NC impairment in young adults, including those with and without chronic HIV infection.

Hepatitis B virus compartmentalization in the cerebrospinal fluid of HIV-infected patients.

We detected hepatitis B virus (HBV) DNA in the cerebrospinal fluid (CSF) of 26 adolescents co-infected with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) with neurological disease and studied compartmentalization of HBV in the CSF. More than half of the subjects with positive HBV DNA plasma also had CSF positive for HBV. CSF HBV DNA was found in subjects with preserved blood-brain barrier integrity. In a subgroup of these subjects, compartmentalized evolution of HBV was demonstrated by distinct profiles of resistance mutations. Future studies are warranted to determine the clinical significance of HBV presence in the CSF and its contribution to HIV-associated neurological disease.

Intracellular mannose binding lectin mediates subcellular trafficking of HIV-1 gp120 in neurons.

Human immunodeficiency virus-1 (HIV-1) enters the brain early during infection and leads to severe neuronal damage and central nervous system impairment. HIV-1 envelope glycoprotein 120 (gp120), a neurotoxin, undergoes intracellular trafficking and transport across neurons; however mechanisms of gp120 trafficking in neurons are unclear. Our results show that mannose binding lectin (MBL) that binds to the N-linked mannose residues on gp120, participates in intravesicular packaging of gp120 in neuronal subcellular organelles and also in subcellular trafficking of these vesicles in neuronal cells. Perinuclear MBL:gp120 vesicular complexes were observed and MBL facilitated the subcellular trafficking of gp120 via the endoplasmic reticulum (ER) and Golgi vesicles. The functional carbohydrate recognition domain of MBL was required for perinuclear organization, distribution and subcellular trafficking of MBL:gp120 vesicular complexes. Nocodazole, an agent that depolymerizes the microtubule network, abolished the trafficking of MBL:gp120 vesicles, suggesting that these vesicular complexes were transported along the microtubule network. Live cell imaging confirmed the association of the MBL:gp120 complexes with dynamic subcellular vesicles that underwent trafficking in neuronal soma and along the neurites. Thus, our findings suggest that intracellular MBL mediates subcellular trafficking and transport of viral glycoproteins in a microtubule-dependent mechanism in the neurons.

Immunophilin expression in the HIV-infected brain.

Immunophilins (IP) are receptors for immunosuppressive drugs and also aid protein folding, assembly, and trafficking. This autopsy study analyses the levels of FKBP12 in the brain of patients with HIV encephalitis. We show that the expression of FKBP12 is increased in the deep gray matter and frontal cortex where it colocalizes with markers of pathology. Changes in FKBP12 levels may be linked to the abnormal protein folding and axonal transport that characterize the neurodegenerative process and could also explain the selective vulnerability of the basal ganglia to HIV infection.

Immunophilins in nervous system degeneration and regeneration.

Immunophilins are receptors for immunosuppressive drugs like cyclosporin A, FK506, rapamycin and their non- immunosuppressive analogs, which are collectively referred to as "immunophilin ligands" (IPL). Cyclosporin A binds to a class of IP called cyclophilins, whereas the receptors for FK506 and rapamycin belong to the family of FK506- binding proteins (FKBP). The latter are designated according to their molecular weight: FKBP12, 25, 52 etc. FKBP levels in the rat brain are up to 50 times higher than in the immune system. FKBP12 is associated with IP3 and ryanodine receptors present on the endoplasmic reticulum and plays a role in stabilizing calcium release. It has also been proposed to be a modulator of the TGFbeta receptor activity. Crush injury of facial or sciatic nerves in rat leads to markedly increased FKBP12 levels in the respective nerve nuclei and this increase is related to nerve regeneration. Cyclophilin A protects cells from death following expression of mutant Cu/ Zn superoxide dismutase, which is associated with familial amyotrophic lateral sclerosis. Our recent studies show that FKBP12 and FKBP52 are expressed in the human nervous system, especially in the substantia nigra- deep gray matter axis. In neurodegenerative diseases, FKBP12 levels increase in neurons situated in areas of pathology. This IP colocalizes with synaptophysin and alpha- synuclein, suggesting that it may become a novel marker of pathology. Immunophilins participate in axonal transport, synaptic vesicle assembly and may play a role in neuroprotection against abnormal protein aggregation, suggesting a potential avenue of therapeutic interventions.

Immunophilins and their ligands: insights into survival and growth of human neurons.

The immunophilin receptors implicated in generating the neurotrophic effects of FK506 and rapamycin (RM) are unknown. Our studies are directed at (1) characterizing the effects of FK506 and RM on human fetal neurons and glia (2) revealing the role played by the immunophilin FKBP receptors and downstream effectors in mediating the effects of FK506 and RM on human brain cells and (3) clarifying the role of immunophilins (IP) in the normal and degenerating human brain. These studies provide the basis for the implementation of the FDA-approved immunophilin ligands (IPL) in the pharmacologic treatment of Parkinson's disease (PD). Additionally, they establish a potential link to pathogenetic and repair mechanisms associated with neurodegeneration and propose FKBP12 and FKBP52 as substrates that can be targeted by future drug design endeavors. Our studies also show for the first time that the immunophilin FKBP is present in the human brain and that its levels are altered in the brain of patients with neurodegenerative diseases. The increased levels of FKBP12 in neurons situated in areas of degeneration suggest that it may become a novel marker of pathology. Although the precise role of this immunophilin in the normal and degenerating brain awaits further clarification, this study suggests that FKBP might play a role in neuroprotection against abnormal protein aggregation, as well as participate in axonal transport and synaptic vesicle assembly. The rotamase activity of FKBP is likely to underlie these functions. If this hypothesis is confirmed, therapeutic attempts using rotamase activity-inhibiting immunophilin ligand administration in neurodegenerative disease patients need to be carefully designed.

The immunosuppressant drug FK506 is a potent trophic agent for human fetal neurons.

FK506 is a potent immunosuppressive drug used to prevent rejection post-organ transplantation. It is activated upon binding to members of the immunophilin chaperone proteins (e.g. FK506-binding protein, FKBP 12). Studies of the distribution of FKBP12 reveal that it is enriched in neurons throughout the central and peripheral nervous system. In vitro, FK506 augments neurite outgrowth; in animal models, it enhances axonal re-growth and functional recovery following lesioning. The effects on human neurons and glial cells have not yet been studied. Using immunofluorescent laser scanning confocal microscopy we demonstrate that in human fetal brain cultures FK506 significantly increases cell numbers, including neurons, and the expression of the neuronal marker MAP-2. This suggests that the drug has a potent effect in stimulating neuronal survival, proliferation and dendrite extension. Interestingly, in combination with brain-derived neurotrophic factor, FK506 induces a prominent decrease in glial fibrillary acidic protein expression, which indicates an inhibitory effect on astrogliosis in vitro. Our data support a potential role for FK506 and its analogues in the treatment of neurodegenerative disorders.

Response of cell cycle proteins to neurotrophic factor and chemokine stimulation in human neuroglia.

Increased expression of neurotrophins (e.g., NGF, BDNF) and chemokines (e.g., RANTES) has been observed in neurodegenerative diseases. We examined the effect of these factors on intracellular signaling cascades inducing cell cycle proteins p53, pRb, and E2F1 in human fetal mixed neuronal and glial cells. Comparing neurotrophin- and chemokine-treated cultures with untreated controls showed altered subcellular localization and expression of hyperphosphorylated retinoblastoma protein (ppRb), E2F1, and p53. Using immunofluorescent laser confocal microscopy, E2F1 and ppRb were detected exclusively in neuronal nuclei in control cultures while p53 was cytoplasmic in astrocytes and nuclear in neurons. Following treatment with neurotrophins, E2F1 and ppRb were observed in the cytoplasm of neurons, while p53 was observed in both neuronal and astrocytic nuclei. Similar findings were observed following treatment with RANTES. Semiquantitative analysis using immunoblots showed an increase in the amount of phosphorylated pRb in treated cultures. Induction of cell cycle proteins may play a role in neurodegeneration associated with neurotrophin and chemokine stimulation.

Damage and repair of DNA in HIV encephalitis.

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.

Blood-brain barrier disruption in simian immunodeficiency virus encephalitis.

Infected monocyte-derived macrophages (MDM) are thought by some investigators to play a central role in the neuropathogenesis of human immunodeficiency virus encephalitis (HIVE). It was recently proposed that these cells gain access to the central nervous system (CNS) through disruptions in blood-brain barrier (BBB) tight junctions, which occur in HIVE in association with accumulation of activated, HIV-1-infected, perivascular macrophages and serum protein extravasation (Am J Pathol 1999, 155: 1915-27). The present study tested this hypothesis in basal ganglia tissue from simian immunodeficiency virus (SIV)-infected macaques with encephalitis by examining vessels for immunohistochemical alterations in the tight junction-associated proteins, occludin and zonula occludens-1 (ZO-1). Compared to non-infected macaques and SIV-infected macaques without encephalitis, cerebral vessels from macaques with SIVE showed fragmentation and decreased immunoreactivity for both tight junction proteins. These alterations were associated with accumulation of perivascular macrophages and aberrant occludin and ZO-1 immunoreactivity within these cells. In addition, perivascular extravasation of fibrinogen, a plasma protein, and a change from a strong linear staining pattern to a more irregular pattern of glucose transporter isoform-1 (GLUT-1), a metabolic BBB marker, were observed in regions with vascular tight junction protein alterations. These findings demonstrate that tight junction disruption occurs in SIVE in association with perivascular macrophage accumulation. While it cannot be ascertained from these studies whether such changes precede macrophage infiltration, or are secondary to the chronic presence of macrophages around cerebral vessels, disruptions in BBB integrity could serve as portals for additional accumulation of perivascular macrophages in SIVE.

Differential expression of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in chronic murine retroviral encephalitis.

The cell adhesion molecules, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1, are important mediators of immune interactions within the central nervous system (CNS). A wide variety of pro-inflammatory insults to the brain, including viral infection, result in upregulation of these molecules on brain endothelial cells, astrocytes, and microglia. This study investigated the expression of ICAM-1 and VCAM-1 in chronic encephalitis induced by infection with a temperature sensitive (ts-1) strain of Moloney murine leukaemia virus (MoMuLV), an ecotropic murine retrovirus. During the late stages of disease, viral antigen was present in both endothelial cells and microglia, but not astrocytes, in regions of spongiform change and gliosis. In these areas, ICAM-1 staining was detected on activated microglia, but not on endothelial cells or astrocytes. In contrast, no cells showed increased VCAM-1 expression in the CNS. These findings demonstrate that there is cell-specific, differential expression of these adhesion molecules in ts-1 retroviral encephalitis. The lack of endothelial cell expression correlates with the characteristic lack of lymphocytic infiltrate in this chronic retroviral encephalitis and suggests that increased microglial ICAM-1 expression may play a role in the pathogenesis of MoMuLV (ts-1)-mediated neurodegeneration.

Blood-brain barrier tight junction disruption in human immunodeficiency virus-1 encephalitis.

The blood-brain barrier (BBB) plays a critical role in regulating cell trafficking through the central nervous system (CNS) due to several unique anatomical features, including the presence of interendothelial tight junctions that form impermeable seals between the cells. Previous studies have demonstrated BBB perturbations during human immunodeficiency virus encephalitis (HIVE); however, the basis of these permeability changes and its relationship to infiltration of human immunodeficiency virus type 1 (HIV-1)-infected monocytes, a critical event in the pathogenesis of the disease, remains unclear. In this study, we examined CNS tissue from HIV-1-seronegative patients and HIV-1-infected patients, both with and without encephalitis, for alterations in BBB integrity via immunohistochemical analysis of the tight junction membrane proteins, occludin and zonula occludens-1 (ZO-1). Significant tight junction disruption (P < 0.001), as demonstrated by fragmentation or absence of immunoreactivity for occludin and ZO-1, was observed within vessels from subcortical white matter, basal ganglia, and, to a lesser extent, cortical gray matter in patients who died with HIVE. These alterations were also associated with accumulation of activated, HIV-1-infected brain macrophages, fibrinogen leakage, and marked astrocytosis. In contrast, no significant changes (P > 0.05) were observed in cerebellar tissue from patients with HIVE compared to HIV-seronegative patients or HIV-1-infected patients without encephalitis. Our findings demonstrate that tight junction disruption is a key feature of HIVE that occurs in regions of histopathological alterations in association with perivascular accumulation of activated HIV-1-infected macrophages, serum protein extravasation, and marked astrocytosis. We propose that disruption of this key BBB structure serves as the main route of HIV-1-infected monocyte entry into the CNS.

HIV mediates a productive infection of the brain.

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.

Tyramide signal amplification method in multiple-label immunofluorescence confocal microscopy.

The tyramide signal amplification (TSA) method has recently been introduced to improve the detection sensitivity of immunohistochemistry. We present three examples of applying this method to immunofluorescence confocal laser microscopy: (1) single labeling for CD54 in frozen mouse brain tissue; (2) double labeling with two unconjugated primary antibodies raised in the same host species (human immunodeficiency virus type 1 p24 and CD68) in paraffin-biopsied human lymphoid tissue; and (3) triple labeling for brain-derived neurotrophic factor, glial fibrillary acidic protein, and HLA-DR in paraffin-autopsied human brain tissue. The TSA method, when properly optimized to individual tissues and primary antibodies, is an important tool for immunofluorescence microscopy. Furthermore, the TSA method and enzyme pretreatment can be complementary to achieve a high detection sensitivity, particularly in formalin-fixed paraffin-embedded archival tissues. Using multiple-label immunofluorescence confocal microscopy to characterize the cellular localization of antigens, the TSA method can be critical for double labeling with unconjugated primary antibodies raised in the same host species.

Absence of brain-derived neurotrophic factor and trkB receptor immunoreactivity in glia of Alzheimer's disease.

Alterations in the neuronal expression of some neurotrophins have been shown in various neurodegenerative processes, particularly Alzheimer's disease (AD). Glia may up-regulate neurotrophins and their high-affinity tyrosine kinase (trk) receptors in response to neural injury. In human immunodeficiency virus type 1 (HIV-1) encephalitis, activated microglia were shown to express brain-derived neurotrophic factor (BDNF), while reactive astrocytes expressed trkB receptor. This observation has suggested the existence of local neurotrophic regulation between different glial populations. To characterize the glial cellular distribution of BDNF and trkB receptor proteins in AD, we studied selected regions of postmortem brains from four AD and three age-matched control patients by double-immunofluorescence confocal microscopy. In both groups, BDNF immunoreactivity was distributed in neuronal perikarya and neuritic processes in the neocortex and hippocampus. No BDNF immunoreactivity was observed in microglia or astrocytes within and between senile plaques of AD. Catalytic trkB receptor immunoreactivity was present in neuronal perikarya in the neocortex and hippocampus. Reactive astrocytes and microglia were not immunoreactive for catalytic trkB. The absence of BDNF and trkB proteins in glia in AD patients is in contrast to the finding in patients with HIV-1 encephalitis. This difference suggests that glial expression of BDNF and trkB proteins may be characteristic of particular disease processes, rather than merely representing a stereotyped response to any type of neural injury.

Neuron-enriched second trimester human cultures: growth factor response and in vivo graft survival.

Grafts of first trimester fetal tissue show limited survival and integration in the adult CNS. Alternative grafting strategies have been sought for treatment of neurodegenerative disease. We have developed cultures of human second trimester fetal tissues to study neuronal differentiation. Grafted into the SCID mouse striatum, aggregates of these cultures formed neuron-rich xenografts for at least 8 months. We examined the influence of various neurotrophic factors, including basic fibroblast growth factor (bFGF), brain-derived neurotrophic factor (BDNF), transforming growth factor-beta 1 (TGF-beta1), and hepatocyte growth factor (HGF), on the growth and differentiation of neuronal and glial cell populations. BDNF promoted the survival and differentiation of second trimester neurons whereas bFGF exhibited a strong proliferative effect on precursors and the astroglial population. Our data suggest that second trimester human fetal cultures contain neuroprogenitor cells that can be directed to the neuronal lineage. This process may be amplified by treatment with BDNF, which we hypothesize could improve the long-term in vivo survival of neuron-enriched grafts.

Sources of the neurotoxin quinolinic acid in the brain of HIV-1-infected patients and retrovirus-infected macaques.

This study investigated the sources of quinolinic acid, a neurotoxic tryptophan-kynurenine pathway metabolite, in the brain and blood of HIV-infected patients and retrovirus-infected macaques. In brain, quinolinic acid concentrations in HIV-infected patients were elevated by > 300-fold to concentrations that exceeded cerebrospinal fluid (CSF) by 8.9-fold. There were no significant correlations between elevated serum quinolinic acid levels with those in CSF and brain parenchyma. Because nonretrovirus-induced encephalitis confounds the interpretation of human postmortem data, rhesus macaques infected with retrovirus were used to examine the mechanisms of increased quinolinic acid accumulations and determine the relationships of quinolinic acid to encephalitits and systemic responses. The largest kynurenine pathway responses in brain were associated with encephalitis and were independent of systemic responses. CSF quinolinic acid levels were also elevated in all infected macaques, but particularly those with retrovirus-induced encephalitis. In contrast to the brain changes, there was no difference in any systemic measure between macaques with encephalitis vs. those without. Direct measures of the amount of quinolinic acid in brain derived from blood in a macaque with encephalitis showed that almost all quinolinic acid (>98%) was synthesized locally within the brain. These results demonstrate a role for induction of indoleamine-2,3dioxygenase in accelerating the local formation of quinolinic acid within the brain tissue, particularly in areas of encephalitis, rather than entry of quinolinic acid into the brain from the meninges or blood. Strategies to reduce QUIN production, targeted at intracerebral sites, are potential approaches to therapy.

Chemokines and receptors in HIV encephalitis.

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.