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HIV-associated neurocognitive disorders (HANDs) persist even with virologic suppression on combination antiretroviral therapy (cART), and the underlying pathophysiological mechanisms are not well understood. We performed structural magnetic resonance imaging and MR spectroscopy (MRS) in HIV+ individuals without major neurocognitive comorbidities. Study participants were classified as neurocognitively unimpaired (NU), asymptomatic (ANI), mild neurocognitive disorder (MND), or HIV-associated dementia (HAD). Using structural MRI, we measured volumes of cortical and subcortical gray matter and total and abnormal white matter (aWM). Using single-voxel MRS, we estimated metabolites in frontal gray matter (FGM) and frontal white matter (FWM) and basal ganglia (BG) regions. Adjusted odds ratios were used to compare HAND to NU. Among 253 participants, 40% met HAND criteria (21% ANI, 15% MND, and 4% HAD). Higher risk of HAND was associated with more aWM. Both HAD and MND also had smaller gray and white matter volumes than NU. Among individuals with undetectable plasma HIV RNA, structural volumetric findings were similar to the overall sample. MND had lower FWM creatine and higher FGM choline relative to NU, whereas HAD and ANI had lower BG N-acetyl aspartate relative to NU. In the virologically suppressed subgroup, however, ANI and MND had higher FGM choline compared to NU. Overall, HAND showed specific alterations (more aWM and inflammation; less gray matter volume and lower NAA). Some MR measures differentiated less severe subtypes of HAND from HAD. These MR alterations may represent legacy effects or accumulating changes, possibly related to medical comorbidities, antiretroviral therapy, or chronic effects of HIV brain infection.

HIV-associated neurocognitive disorders (HAND) remain prevalent in the combined antiretroviral therapy (CART) era, especially the milder forms. Despite these milder phenotypes, we have shown that motor abnormalities persist and have quantified them with the HIV Dementia Motor Scale (HDMS). Our objectives were to replicate, in an independent sample, our prior findings that the HDMS is associated with cognitive impairment in HIV, while adding consideration of age-associated comorbidities such as cerebrovascular disease, and to examine the longitudinal trajectories of cognitive and motor dysfunction. We included all participants enrolled in the Manhattan HIV Brain Bank (MHBB) from January 2007 to May 2017 who had complete baseline data (N = 164). MHBB participants undergo standardized longitudinal assessments including documentation of comorbidities and medications, blood work, the HDMS, and neurocognitive testing. We found that motor dysfunction, cognitive impairment, and cerebrovascular disease were significantly associated with each other at baseline. Cerebrovascular disease independently predicted cognitive impairment in a multivariable model. Longitudinal analysis in a subset of 78 participants with ≥ 4 years of follow-up showed a stable cognition but declining motor function. We conclude that the HDMS is a valid measurement of motor dysfunction in HIV-infected patients and is associated with cognitive impairment and the presence of cerebrovascular disease. Cognitive impairment is mild and stable in CART-treated HIV; however, motor function declines over time, which may be related to the accrual of comorbidities such as cerebrovascular disease. Further research should examine the mechanisms underlying motor dysfunction in HIV and its clinical impact.

We aimed to test the hypothesis that brain large artery diameters relate to distal downstream arteriolar diameters. In a sample of 110 autopsied individuals (69% men, 76% HIV+, mean age 51), we used multilevel models to relate large artery lumen and lumen-to-wall ratio to left frontal lobe arteriolar lumen and lumen-to-wall ratio adjusting for demographics and vascular risk factors. Comparing the large artery characteristics of the whole brain did not disclose significant associations with frontal lobe arteriolar characteristics. However, restricting the comparison to large arteries upstream of the studied arterioles demonstrated an independent association between left-sided frontal lobe arteriolar luminal diameter with large artery luminal diameters (B = 1.82 ± 0.77, P = 0.01) and with large artery lumen-to-wall ratio (B = 0.58 ± 0.29, P = 0.05). In stratified models, the point estimates in the HIV+ subsample were larger than in the HIV- subsample. These finding suggest coupling between higher proximal blood flow represented by large artery diameter and lower distal resistance represented by arteriolar dilatation. The relationship between arteriolar dilatation and brain parenchyma homeostasis should be further studied.

BACKGROUND. Small intestinal bacterial overgrowth (SIBO) is common among patients with HIV-associated autonomic neuropathies (HIV-AN), and may be associated with increased bacterial translocation and elevated plasma inflammatory biomarkers. Pyridostigmine is an acetylcholinesterase inhibitor which has been used to augment autonomic signaling. We sought preliminary evidence as to whether pyridostigmine could improve proximal gastrointestinal motility, reduce SIBO, reduce plasma sCD14 (a marker of macrophage activation and indirect measure of translocation), and reduce the inflammatory cytokines IL-6 and TNFα in patients with HIV-AN. METHODS. Fifteen participants with well-controlled HIV, HIV-AN, and SIBO, were treated with 8 weeks of pyridostigmine (30mg PO TID). Glucose breath testing for SIBO, gastric emptying studies (GES) to assess motility, plasma sCD14, IL-6 and TNFα, and gastrointestinal autonomic symptoms were compared before and after treatment. RESULTS. Thirteen participants (87%) experienced an improvement in SIBO following pyridostigmine treatment; with an average improvement of 50% (p=0.016). There was no change in gastrointestinal motility, however only two participants met GES criteria for gastroparesis at baseline. TNFα and sCD14 levels declined by 12% (p=0.004) and 19% (p=0.015) respectively; there was no significant change in IL-6 or gastrointestinal symptoms. CONCLUSION. Pyridostigmine may ameliorate SIBO and reduce levels of sCD14 and TNFα in patients with HIV-AN. Larger placebo-controlled studies are needed to definitively delineate how HIV-AN affects gastrointestinal motility, SIBO, and systemic inflammation in HIV, and whether treatment improves clinical outcomes.

The criteria for differentiating symptomatic from asymptomatic HIV-associated neurocognitive disorder require evaluation of (1) cognitive impairment, (2) daily functioning declines, and (3) whether the functional declines are attributable to cognitive versus physical problems. Many providers rely only on self-report to evaluate these latter criteria. However, the accuracy of patient-provided information may be limited. This study evaluated the validity of self-assessment for HIV-associated neurocognitive disorder (HAND) diagnoses by comparing objective findings with self-report of criteria 2 and 3 above. Self-reports were used to stratify 277 cognitively impaired HIV+ individuals into functionally dependent (n = 159) and independent (n = 118) groups, followed by group comparisons of objective functional problems. The dependent group was then divided into those who self-attributed their functional dependence to only cognitive (n = 80) versus only physical (n = 79) causes, for further comparisons on objective findings. The functionally dependent group was significantly worse than the independent group on all objective disability characteristics except severity of cognitive impairment, while those who attributed their dependence to physical (versus cognitive) factors were similar on all objective physical, cognitive, and functioning variables. Of note, 28% of physical attributors showed no physical abnormalities on neuromedical examinations. Results suggest that patient report is consistently associated with objective measures of functional loss; in contrast, patient identification of physical versus cognitive causes is poorly associated with objective criteria. These findings caution against relying solely on patient self-report to determine whether functional disability in cognitively impaired HIV+ individuals can be attributed to strictly physical causes.

Despite modern antiretroviral therapy, HIVassociated sensory neuropathy affects over 50% of HIV patients. The clinical expression of HIV neuropathy is highly variable: many individuals report few symptoms, but about half report distal neuropathic pain (DNP), making it one of the most prevalent, disabling, and treatment-resistant complications of HIV disease. The presence and intensity of pain is not fully explained by the degree of peripheral nerve damage, making it unclear why some patients do, and others do not, report pain. To better understand central nervous system contributions to HIV DNP, we performed a cross-sectional analysis of structural magnetic resonance imaging volumes in 241 HIV-infected participants from an observational multi-site cohort study at five US sites (CNS HIV Anti-Retroviral Treatment Effects Research Study, CHAR TER). The association between DNP and the structural imaging outcomes was investigated using both linear and nonlinear (Gaussian Kernel support vector) multivariable regression, controlling for key demographic and clinical variables. Severity of DNP symptoms was correlated with smaller total cerebral cortical gray matter volume (r = -0.24; p =0.004). Understanding the mechanisms for this association between smaller total cortical volumes and DNP may provide insight into HIV DNP chronicity and treatment-resistance. © Journal of NeuroVirology, Inc. 2014.

HIV-associated sensory neuropathy remains an important complication of combination antiretroviral therapy and HIV infection. Mitochondrial DNA haplogroups and single nucleotide polymorphisms (SNPs) have previously been associated with symptomatic neuropathy in clinical trial participants. We examined associations between mitochondrial DNA variation and HIV-associated sensory neuropathy in CNS HIV Antiretroviral Therapy Effects Research (CHARTER). CHARTER is a USA-based longitudinal observational study of HIV-infected adults who underwent a structured interview and standardized examination. HIV-associated sensory neuropathy was determined by trained examiners as ≥1 sign (diminished vibratory and sharp-dull discrimination or ankle reflexes) bilaterally. Mitochondrial DNA sequencing was performed and haplogroups were assigned by published algorithms. Multivariable logistic regression of associations between mitochondrial DNA SNPs, haplogroups, and HIV-associated sensory neuropathy were performed. In analyses of associations of each mitochondrial DNA SNP with HIV-associated sensory neuropathy, the two most significant SNPs were at positions A12810G [odds ratio (95 % confidence interval) = 0.27 (0.11-0.65); p = 0.004] and T489C [odds ratio (95 % confidence interval) = 0.41 (0.21-0.80); p = 0.009]. These synonymous changes are known to define African haplogroup L1c and European haplogroup J, respectively. Both haplogroups were associated with decreased prevalence of HIV-associated sensory neuropathy compared with all other haplogroups [odds ratio (95 % confidence interval) = 0.29 (0.12-0.71); p = 0.007 and odds ratio (95 % confidence interval) = 0.42 (0.18-1.0); p = 0.05, respectively]. In conclusion, in this cohort of mostly combination antiretroviral therapy-treated subjects, two common mitochondrial DNA SNPs and their corresponding haplogroups were associated with a markedly decreased prevalence of HIV-associated sensory neuropathy.

Since HIV-1 Tat has been associated with neurocognitive dysfunction, we investigated 60 HIV-1 subtype B-infected individuals who were characterized for neurocognitive functioning and had paired CSF and blood plasma samples available. To avoid issues with repeated sampling, we generated population-based HIV-1 tat sequences from each compartment and evaluated these data using a battery of phylogenetic, statistical, and machine learning tools. These analyses identified position HXB2 5905 within the cysteine-rich domain of tat as a signature of CSF-derived HIV-1, and a higher number of mixed bases in CSF, as measure of diversity, was associated with HIV-associated neurocognitive disorder. Since identified mutations were synonymous, we evaluated the predicted secondary RNA structures, which showed that this mutation altered secondary structure. As a measure of divergence, the genetic distance between the blood and CSF-derived tat was inversely correlated with current and nadir CD4+ T cell counts. These data suggest that specific HIV-1 features of tat influence neurotropism and neurocognitive impairment.

It is well known that infection by the human immunodeficiency virus (HIV) dysregulates cell physiology, but little information is available on the consequences of HIV infection in primary macrophages and microglia. The authors examined the relationship between cell proliferation and HIV infection in primary cultures of microglia and in human central nervous system (CNS). In cultures infected with HIV (ADA and BaL), granulocyte-macrophage colony-stimulating factor (GM-CSF)-mediated cell proliferation was reduced in productively infected (p24+) cells as compared to p24- cells. The reduction was observed with both Ki67 and BrdU labeling, suggesting a G1/S block. The reduction was insignificant when microglia were infected with a Vpr- mutant virus. In human CNS, proliferating (Ki67+) cells were rare but were increased in the HIV+ and HIV encephalitis (HIVE) groups compared to the HIV- group. A positive correlation between GM-CSF immunoreactivity and Ki67 counts, implicating GM-CSF as a growth factor in human CNS was found. The relationship between total macrophage (CD68+) proliferation and infected macrophage (p24+) proliferation was assessed in HIVE by double labeling. Whereas 1.2% of total CD68+ cells were Ki67+, only 0.5% of HIV p24+ cells were Ki67+ (P.05). Furthermore, staining for CD45RB (as opposed to CD68) facilitated the identification of Ki67+ microglia, indicating that CD68 could underestimate proliferating microglia. The authors conclude that although there is increased expression of GM-CSF and increased cell proliferation in the CNS of HIV-seropositive individuals, cell proliferation in the productively infected population is actually suppressed. These data suggest that there might be a viral gain in the suppressed host cell proliferation.

Previous neuroimaging studies suggest a negative relationship between the apolipoprotein (ApoE) e4 allele and brain integrity in human immunodeficiency virus (HIV)-infected (HIV+) individuals, although the presence of this relationship across adulthood remains unclear. The purpose of this study is to clarify the discrepancies using a large, diverse group of HIV+ individuals and multiple imaging modalities sensitive to HIV. The association of ApoE e4 with structural neuroimaging and magnetic resonance spectroscopy (MRS) was examined in 237 HIV+ individuals in the CNS HIV Anti-Retroviral Therapy Effects Research (CHARTER) study. Cortical and subcortical gray matter, abnormal and total white matter, ventricles, sulcal cerebrospinal fluid (CSF), and cerebellar gray matter, white matter, and CSF volumes, and MRS concentrations of myo-inositol, creatine, N-acetyl-aspartate, and choline in the frontal white matter (FWM), frontal gray matter (FGM), and basal ganglia were examined. Secondary analyses explored this relationship separately in individuals ≥50 years old (n = 173) and

Human immunodeficiency virus (HIV)-associated neurocognitive disorders (HAND) persist despite combination antiretroviral therapy (cART), supporting the need to better understand HIV neuropathogenesis. Magnetic resonance spectroscopy (MRS) of the brain has demonstrated abnormalities in HIV-infected individuals despite cART. We examined the associations between MRS metabolites and selected cerebrospinal fluid (CSF) biomarkers reflecting monocyte/macrophage activation and chemotaxis. A multicenter cross-sectional study involving five sites in the USA was conducted. The following CSF biomarkers were measured: soluble CD14 (sCD14), monocyte chemotactic protein-1 (MCP-1), interferon inducible protein 10 (IP-10), and stromal cell-derived growth factor 1 alpha (SDF-1α). The following MRS metabolites were measured from basal ganglia (BG), frontal white matter (FWM), and frontal gray matter (FGM): N-acetylaspartate (NAA), myo-inositol (MI), choline (Cho), and creatine (Cr). CSF biomarkers were compared to absolute MRS metabolites as well as metabolite/Cr ratios using linear regression. Eighty-three HIV-infected individuals were included, 78 % on cART and 37 % with HAND. The most robust positive correlations were between MCP-1 and Cho in BG (R 2 0.179, p

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.

Neurologic complications of HIV are well characterized in the central and peripheral nervous systems but not in the autonomic nervous system, perhaps due to the complexities of measuring autonomic function in medically ill populations. We hypothesized that autonomic dysfunction is common in HIV, can be meaningfully measured with an autonomic reflex screen, and is associated with distal symmetric polyneuropathy (DSP) but not with signs of CNS disease. We also sought to characterize immunovirologic and medical factors associated with autonomic dysfunction. We assessed 102 HIV-infected adults for autonomic dysfunction with a laboratory-based autonomic reflex screen summarized as the composite autonomic severity score (CASS). The total neuropathy score (TNS) was used to quantify DSP based on neurologic interview/examination, quantitative sensory testing, and nerve conduction studies. Autonomic dysfunction was common, with a CASS ≥ 3 in 61 % of participants, of whom 86 % were symptomatic. Greater CASS abnormalities demonstrated univariate association with increasing TNS, age, viral load, hypertension, and use of medications (particularly anticholinergics), but not with antiretrovirals, current/nadir CD(4+) count, HIV duration, metabolic factors, or signs of CNS disease. The TNS was the only significant predictor of the CASS in multivariate analysis; anticholinergic medications were marginally significant. This study demonstrates that autonomic dysfunction is common and frequently symptomatic in HIV and that an autonomic reflex screen, adjusted for anticholinergic medication, is useful in its assessment. Association of autonomic dysfunction with DSP suggests common factors in their pathogenesis, and autonomic neuropathy may be part of the spectrum of HIV-associated peripheral nerve pathologies.

The objective of this study was to examine the spectrum of human immunodeficiency virus (HIV) brain pathology and its clinical correlates in the antiretroviral era. We carried out a cross-sectional survey, analyzing prospective clinical and neuropathological data collected by the National NeuroAIDS Tissue Consortium (NNTC), comprising 589 brain samples from individuals with advanced HIV disease collected from 1999 onwards. We assessed gender, ethnicity/race, mode of transmission, age, year of death, nadir CD4, plasma viral load, last antiretroviral regimen, presence of parenchymal HIV brain pathology, HIV-associated neurocognitive disorder, and major depressive disorder. We compared cohort demographic variables with Centers for Disease Control and Prevention US HIV/AIDS statistics and examined associations of parenchymal HIV brain pathology with demographic, clinical, and HIV disease factors. With regard to Centers for Disease Control and Prevention US data, the NNTC was similar in age distribution, but had fewer females and African Americans and more Hispanics and men who have sex with men. Only 22% of the brains examined were neuropathologically normal. Opportunistic infections occurred in 1% to 5% of the cohort. Parenchymal HIV brain pathology was observed in 17.5% of the cohort and was associated with nadir CD4 and plasma viral load. Brains without parenchymal HIV brain pathology often had other noninfectious findings or minimal nondiagnostic abnormalities that were associated with HIV-associated neurocognitive disorder. Clinically, 60% of the cohort reported a lifetime episode of major depressive disorder and 88% had a HIV-associated neurocognitive disorder. No pathological finding correlated with major depressive disorder. Both antiretroviral treatment regimen and elevated plasma HIV viral load were associated with presence of parenchymal HIV brain pathology; however, multivariate analyses suggest a stronger association with plasma viral load. The frequency of HIV brain pathology was lower than previous pre-antiretroviral reports, and was predicted by lower nadir CD4 and higher plasma viral load. Noninfectious pathologies and minimal changes correlated with HIV-associated neurocognitive disorder, suggesting a shift in pathogenesis from florid HIV replication to other, diverse mechanisms.

Neurodegeneration and dementia caused by human immunodeficiency virus type 1 (HIV-1) infection of the brain are common complications of acquired immunodeficiency syndrome (AIDS). Introduction of highly active antiretroviral therapy (HAART) reduced the incidence of HIV-1-associated dementia, but so far had no effect on the high frequency of milder neurological disorders caused by HIV-1. This indicates that some neuropathogenic processes persist during limited HIV-1 replication in the central nervous system (CNS). The authors are evaluating the hypothesis that interaction of HIV-1 with astrocytes, which bind HIV-1 but support limited productive HIV-1 infection, may contribute to these processes by disrupting astrocyte functions that are important for neuronal activity or survival. Using laser-capture microdissection on brain tissue samples from HIV-1-infected individuals, we found that HIV-1 DNA can be detected in up to 1% of cortical and basal ganglia astrocytes, thus confirming HIV-1 infection in astrocytes from symptomatic patients. Using rapid subtraction hybridization, the authors cloned and identified 25 messenger RNAs in primary human fetal astrocytes either up-regulated or down-regulated by native HIV-1 infection or exposure to gp120 in vitro. Extending this approach to gene microarray analysis using Affymetrix U133A/B gene chips, the authors determined that HIV-1 alters globally and significantly the overall program of gene expression in astrocytes, including changes in transcripts coding for cytokines, G-coupled protein receptors, transcription factors, and others. Focusing on a specific astrocyte function relevant to neuropathogenesis, the authors showed that exposure of astrocytes to HIV-1 or gp120 in vitro impairs the ability of the cells to transport l-glutamate and the authors related this defect to transcriptional inhibition of the EAAT2 glutamate transporter gene. These findings define new pathways through which HIV-1 may contribute to neuropathogenesis under conditions of limited virus replication in the brain.

HIV-1 infection can lead to severe central nervous system (CNS) clinical syndromes in more than 50% of HIV-1 positive individuals. Progressive multifocal leukoencephalopathy (PML) is the frequent opportunistic infection of the CNS which is seen in as high as 5% of AIDS patients. Results from previous cell culture studies showed that the HIV-1 regulatory protein, Tat can potentiate transcription of the human neurotropic virus, JCV, the causative agent for PML in cells derived from the human CNS. In this communication we examine the presence of the HIV-1 regulatory protein, Tat, as well as the HIV-1 and JCV structural proteins, p24 and VP1, respectively in AIDS/PML clinical samples. We demonstrate high level expression of the JCV capsid protein, VP1, in oligodendrocytes and to some degree in astrocytes of AIDS with PML. In HIV-1+ samples expression of HIV-1 core protein, p24 was detected in perivascular monocytic cells and to a lesser extent in astrocytes and endothelial cells. A lack of p24 expression in oligodendrocytes suggested no infection of these cells with HIV-1. Interestingly, HIV-1 Tat was detected in various infected cells as well as in uninfected oligodendrocytes from HIV-1+ tissue, supporting the earlier in vitro findings that secreted Tat from the infected cells can be localized in the neighboring uninfected cells. The presence of Tat in oligodendrocytes was particularly interesting as this protein can up-modulate JCV gene transcription and several key cell cycle regulatory proteins including cyclin E, Cdk2, and pRb. The data presented here provide in vivo evidence for a role of HIV-1 Tat in the pathogenesis of AIDS/PML by acting as a positive regulatory protein that affects the expression of JCV and other cell regulatory proteins in the CNS.

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.

HIV associated neurological diseases include HIV dementia, peripheral neuropathies and progressive multifocal leukoencephalopathy (PML). In the studies presented here, we examined the abnormal accumulation of monocytes/macrophages in the CNS in patients with HIV dementia complex (HIVD), AIDS without dementia, and seronegative controls. Our results demonstrate substantial increases in both perivascular macrophages and ramified parenchymal microglia in HIVD. Although these mononuclear phagocytes were positive for proliferating cell nuclear antigen (PCNA), they do not appear to be proliferating as determined by the paucity of Ki-67 staining. Using antibody to HIV-P24 antigen, PCNA expression co-localized in cells productively infected with HIV-1. Additional cells were negative for HIV-1 P24, but positive for PCNA expression, possibly suggesting the role of secreted factors. These results suggest dysregulation of DNA repair pathways in HIVD, with potential relevance to the JCV activation and the development of PML in the setting of AIDS.