Infection of Glia by Human Pegivirus Suppresses Peroxisomal and Antiviral Signaling Pathways.

Human pegivirus (HPgV) infects peripheral leukocytes but was recently shown to be a neurotropic virus associated with leukoencephalitis in humans. In the present study, we investigated the neural cell tropism of HPgV as well as its effects on host immune responses. HPgV wild type (WT) and a mutant virus with a deletion in the HPgV NS2 gene (ΔNS2) were able to productively infect human astrocytes and microglia but not neurons or an oligodendrocyte-derived cell line. Of note, the ΔNS2 virus replicated better than WT pegivirus in astrocytes, with both viruses being able to subsequently infect and spread in fresh human astrocyte cultures. Infection of human glia by HPgV WT and ΔNS2 viruses resulted in suppression of peroxisome-associated genes, including PEX11B, ABCD1, PEX7, ABCD3, PEX3, and PEX5L, during peak viral production, which was accompanied by reduced expression of IFNB, IRF3, IRF1, and MAVS, particularly in ΔNS2-infected cells. These data were consistent with analyses of brain tissue from patients infected with HPgV in which we observed suppression of peroxisome and type I interferon gene transcripts, including PEX11B, ABCD3, IRF1, and IRF3, with concurrent loss of PMP70 immunoreactivity in glia. Our data indicate that human astrocytes and microglia are permissive to HPgV infection, resulting in peroxisome injury and suppressed antiviral signaling that is influenced by viral diversity. IMPORTANCE Human pegiviruses are detected in 1 to 5% of the general population, principally infecting leukocytes, although their effects on human health remain uncertain. Here, we show that human pegivirus infects specific neural cell types in culture and human brain and, like other neurotropic flaviviruses, causes suppression of peroxisome and antiviral signaling pathways, which could favor ongoing viral infection and perhaps confer susceptibility to the development of neurological disease.

Brain morphometric correlates of metabolic variables in HIV: the CHARTER study.

Obesity and other metabolic variables are associated with abnormal brain structural volumes and cognitive dysfunction in HIV-uninfected populations. Since individuals with HIV infection on combined antiretroviral therapy (CART) often have systemic metabolic abnormalities and changes in brain morphology and function, we examined associations among brain volumes and metabolic factors in the multisite CNS HIV AntiRetroviral Therapy Effects Research (CHARTER) cohort, cross-sectional study of 222 HIV-infected individuals. Metabolic variables included body mass index (BMI), total blood cholesterol (C), low- and high-density lipoprotein C (LDL-C and HDL-C), blood pressure, random blood glucose, and diabetes. MRI measured volumes of cerebral white matter, abnormal white matter, cortical and subcortical gray matter, and ventricular and sulcal CSF. Multiple linear regression models allowed us to examine metabolic variables separately and in combination to predict each regional volume. Greater BMI was associated with smaller cortical gray and larger white matter volumes. Higher total cholesterol (C) levels were associated with smaller cortex volumes; higher LDL-C was associated with larger cerebral white matter volumes, while higher HDL-C levels were associated with larger sulci. Higher blood glucose levels and diabetes were associated with more abnormal white matter. Multiple atherogenic metabolic factors contribute to regional brain volumes in HIV-infected, CART-treated patients, reflecting associations similar to those found in HIV-uninfected individuals. These risk factors may accelerate cerebral atherosclerosis and consequent brain alterations and cognitive dysfunction.

Characterizing HIV medication adherence for virologic success among individuals living with HIV/AIDS: Experience with the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) cohort.

Antiretroviral therapy (ART) has changed HIV related illness from terminal to chronic by suppressing viral load which results in immunologic and clinical improvement. Success with ART is dependent on optimal adherence, commonly categorized as >95%. As medication type, class and frequency of use continue to evolve, we assessed adherence levels related to viral suppression. Using a cross-sectional analysis with secondary data (n = 381) from an ongoing multi-site study on impact of ART on the Central Nervous System (CNS), we compared self-reported adherence rates with biological outcomes of HIV-RNA copies/ml, and CD4 cell/mm3. Adherence to ART measures included taking all prescribed medication as directed on schedule and following dietary restrictions. While depression was a barrier to adherence, undetectable viral suppression was achieved at pill adherence percentages lower than 95%. Practice, research and policy implications are discussed in the context of patient-, provider-, and system-level factors influencing adherence to ART.

Apolipoprotein E4 genotype does not increase risk of HIV-associated neurocognitive disorders.

This is a cross-sectional, observational study to evaluate the hypothesis that HIV-seropositive (HIV+) apolipoprotein E4 (APOE4) carriers are at increased risk for HIV-associated neurocognitive disorders (HAND) compared to APOE4 noncarriers with HIV in the CNS HIV Antiretroviral Therapy Effects Research (CHARTER) Group sample. APOE genotype was determined in 466 CHARTER participants with varying disease stages and histories of antiretroviral treatment who did not have severe psychiatric or medical comorbid conditions that preclude diagnosis of HAND. HAND diagnoses were based on results of comprehensive neurobehavioral evaluation and use of current neuroAIDS diagnostic criteria. HAND status consists of two levels: neuropsychologically normal status (i.e., no HAND) and any HAND diagnosis (i.e., asymptomatic neurocognitive impairment, minor neurocognitive disorder, HIV-associated dementia). Logistic regression analyses revealed no association between APOE4 carrier status and HAND, and there were no interactions between APOE4 carrier status and ethnicity, age, substance use disorders, duration of infection, or nadir CD4. Results did not differ when analysis was restricted to symptomatic HAND, and no APOE4 gene dose-dependent relationship to HAND emerged. APOE4 status was not associated with concurrent HAND in this large, well-characterized sample. This does not preclude emergence of an association between APOE4 status and HAND as this population ages. Prospective, longitudinal studies are needed to examine APOE4 as a risk factor for neurocognitive decline, incident HAND at older ages, and potential associations with cerebrospinal fluid amyloid.

Defining neurocognitive impairment in HIV: deficit scores versus clinical ratings.

Because HIV-related neurocognitive impairment is usually mild and variable, clinical ratings (CR) and global deficit scores (GDS) are recommended for detecting HIV-associated neurocognitive disorders (HAND). The CR approach requires impairment in at least two ability domains while the GDS considers number and severity of impairments across all measures. We examined classification agreement and clinical correlates of the two methods. Neurocognitive functioning of 1574 HIV-infected participants was assessed via a comprehensive, seven-domain neuropsychological battery. Global neurocognitive impairment was defined for each participant independently by CR and GDS. Participants were classified into four categories (Dually-normal, [impaired by] CR-only, [impaired by] GDS-only, or Dually-impaired). There was 83% concordance between CR and GDS classifications; in total, 56% of participants were deemed impaired by CR and 41% were classified as impaired by GDS. Impairment by GDS virtually guaranteed CR impairment, but 16% of participants were additionally classified as impaired only by CR. As compared to Dually-normal participants, those classified as Dually and CR-only impaired were more likely to have AIDS, have more severe co-occurring conditions, have more severe depressive symptoms, be unemployed, and have more everyday functioning complaints (ps < .05). Impairment classifications of the two methods were in high agreement; however, more people were classified as impaired using the CR approach compared to the GDS approach. Those impaired according to CR-only showed fewer neurocognitive and functional deficits than the Dually-impaired participants, but more of these deficits than Dually-normal participants. The CR approach may be most appropriate for detecting more subtle forms of neurocognitive impairment. Clinicians and researchers should recognize the strengths and weaknesses of each method when evaluating neurocognitive complications in HIV.

Diagnosing symptomatic HIV-associated neurocognitive disorders: self-report versus performance-based assessment of everyday functioning.

Three types of HIV-associated neurocognitive disorders (HAND) exist that are distinguished by presence and severity of impairment in cognitive and everyday functioning. Although well-validated neurocognitive measures exist, determining impairment in everyday functioning remains a challenge. We aim to determine whether Self-Report measures of everyday functioning are as effective in characterizing HAND as Performance-Based measures. We assessed 674 HIV-infected participants with a comprehensive neurocognitive battery; 233 met criteria for a HAND diagnosis by having at least mild neurocognitive impairment. Functional decline was measured via Self-Report and Performance-Based measures. HAND diagnoses were determined according to published criteria using three approaches to assess functional decline: (1) Self-Report measures only, (2) Performance-Based measures only, and (3) Dual-method combining Self-Report and Performance-Based measures. The Dual-method classified the most symptomatic HAND, compared to either singular method. Singular method classifications were 76% concordant with each other. Participants classified as Performance-Based functionally impaired were more likely to be unemployed and more immunosuppressed, whereas those classified as Self-Report functionally impaired had more depressive symptoms. Multimodal methods of assessing everyday functioning facilitate detection of symptomatic HAND. Singular Performance-Based classifications were associated with objective functional and disease-related factors; reliance on Self-Report classifications may be biased by depressive symptoms.

HIV-associated neurocognitive disorders persist in the era of potent antiretroviral therapy: CHARTER Study.

OBJECTIVES: This is a cross-sectional, observational study to determine the frequency and associated features of HIV-associated neurocognitive disorders (HAND) in a large, diverse sample of infected individuals in the era of combination antiretroviral therapy (CART). METHODS: A total of 1,555 HIV-infected adults were recruited from 6 university clinics across the United States, with minimal exclusions. We used standardized neuromedical, psychiatric, and neuropsychological (NP) examinations, and recently published criteria for diagnosing HAND and classifying 3 levels of comorbidity (minimal to severe non-HIV risks for NP impairment). RESULTS: Fifty-two percent of the total sample had NP impairment, with higher rates in groups with greater comorbidity burden (40%, 59%, and 83%). Prevalence estimates for specific HAND diagnoses (excluding severely confounded cases) were 33% for asymptomatic neurocognitive impairment, 12% for mild neurocognitive disorder, and only 2% for HIV-associated dementia (HAD). Among participants with minimal comorbidities (n = 843), history of low nadir CD4 was a strong predictor of impairment, and the lowest impairment rate on CART occurred in the subset with suppressed plasma viral loads and nadir CD4 ≥200 cells/mm(3) (30% vs 47% in remaining subgroups). CONCLUSIONS: The most severe HAND diagnosis (HAD) was rare, but milder forms of impairment remained common, even among those receiving CART who had minimal comorbidities. Future studies should clarify whether early disease events (e.g., profound CD4 decline) may trigger chronic CNS changes, and whether early CART prevents or reverses these changes.

Association of self-reported painful symptoms with clinical and neurophysiologic signs in HIV-associated sensory neuropathy.

Sensory neuropathy (HIV-SN) is a common cause of pain in HIV-infected people. Establishing a diagnosis of HIV-SN is important, especially when contemplating opioid use in high-risk populations. However physical findings of HIV-SN may be subtle, and sensitive diagnostic tools require specialized expertise. We investigated the association between self-report of distal neuropathic pain and/or paresthesias (DNPP) and objective signs of HIV-SN. Data were obtained from the Central Nervous System HIV Antiretroviral Therapy Effects Research (CHARTER) study. Out of 237 participants, 101 (43%) reported DNPP. Signs of HIV-SN were measured by a modified Total Neuropathy Score (TNS), composed of six objective sensory subscores (pin sensibility, vibration sensibility, deep tendon reflexes, quantitative sensory testing for cooling and vibration, and sural sensory amplitude). Self-report of DNPP was associated with all six TNS items in univariate analysis and with four TNS items in multivariate analysis. The sensitivity and specificity of self-report of DNPP in detecting the presence of a sensory abnormality were 52% and 92%, respectively with a PPV of 96% and a NPV of 34%. Increasing intensity of pain measured on a visual analog scale was associated with increasing severity of sensory abnormality. In summary, our results suggest that HIV-infected patients reporting symptoms consistent with HIV-SN, such as tingling, pins and needles, or aching or stabbing pain in the distal lower extremities, usually have objective evidence of HIV-SN on neurologic examination or with neurophysiologic testing. This finding holds true regardless of demographic factors, depression or substance use history.

Aquaporins in spinal cord injury: the janus face of aquaporin 4.

Although malfunction of spinal cord water channels (aquaporins, AQP) likely contributes to severe disturbances in ion/water homeostasis after spinal cord injury (SCI), their roles are still poorly understood. Here we report and discuss the potential significance of changes in the AQP4 expression in human SCI that generates glial fibrillary acidic protein (GFAP)-labeled astrocytes devoid of AQP4, and GFAP-labeled astroglia that overexpress AQP4. We used a rat model of contusion SCI to study observed changes in human SCI. AQP4-negative astrocytes are likely generated during the process of SCI-induced replacement of lost astrocytes, but their origin and role in SCI remains to be investigated. We found that AQP4-overexpression is likely triggered by hypoxia. Our transcriptional profiling of injured rat cords suggests that elevated AQP4-mediated water influx accompanies increased uptake of chloride and potassium ions which represents a protective astrocytic reaction to hypoxia. However, unbalanced water intake also results in astrocytic swelling that can contribute to motor impairment, but likely only in milder injuries. In severe rat SCI, a low abundance of AQP4-overexpressing astrocytes was found during the motor recovery phase. Our results suggest that severe rat contusion SCI is a better model to analyze AQP4 functions after SCI. We found that AQP4 increases in the chronic post-injury phase are associated with the development of pain-like behavior in SCI rats, while possible mechanisms underlying pain development may involve astrocytic swelling-induced glutamate release. In contrast, the formation and size of fluid-filled cavities occurring later after SCI does not appear to be affected by the extent of increased AQP4 levels. Therefore, the effect of therapeutic interventions targeting AQP4 will depend not only on the time interval after SCI or animal models, but also on the balance between protective role of increased AQP4 in hypoxia and deleterious effects of ongoing astrocytic swelling.

Interrater reliability of the Psychiatric Research Interview for Substance and Mental Disorders in an HIV-infected cohort: experience of the National NeuroAIDS Tissue Consortium.

The interrater reliability of the Psychiatric Research Interview for Substance and Mental Disorders (PRISM) was assessed in a multicentre study. Four sites of the National NeuroAIDS Tissue Consortium performed blinded reratings of audiotaped PRISM interviews of 63 HIV-infected patients. Diagnostic modules for substance-use disorders and major depression were evaluated. Seventy-six per cent of the patient sample displayed one or more substance-use disorder diagnoses and 54% had major depression. Kappa coefficients for lifetime histories of substance abuse or dependence (cocaine, opiates, alcohol, cannabis, sedative, stimulant, hallucinogen) and major depression ranged from 0.66 to 1.00. Overall the PRISM was reliable in assessing both past and current disorders except for current cannabis disorders when patients had concomitant cannabinoid prescriptions for medical therapy. The reliability of substance-induced depression was poor to fair although there was a low prevalence of this diagnosis in our group. We conclude that the PRISM yields reliable diagnoses in a multicentre study of substance-experienced, HIV-infected individuals.

p73 modulates HIV-1 Tat transcriptional and apoptotic activities in human astrocytes.

HIV-1 Tat is a potent transcriptional activator of the viral promoter with the ability to modulate a number of cellular regulatory circuits including apoptosis. Tat exerts its effects through interaction with viral as well as cellular proteins. Here, we studied the influence of p73, a protein that is implicated in apoptosis and cell cycle control, on Tat apoptotic function in the central nervous system. We recently demonstrated the ability of Tat to associate with p73, and that this association modulates Tat transcriptional activity (Amini et al., Mol Cell Biol 2005; 18: 8126-8138). We demonstrated that p73 interferes with Tat-mediated apoptosis by preventing the up-regulation of Bax and down-regulation of Bcl-2 proteins in astrocytes. Thus, the interplay between Tat and p73 may affect Tat contribution to apoptotic events in the brain, limiting its involvement in the neuropathology often observed in the brains of HIV-1 patients.

Evidence that infiltrating neutrophils do not release reactive oxygen species in the site of spinal cord injury.

The release of reactive oxygen species (ROS) by neutrophils, which infiltrate the region of damage following spinal cord injury (SCI), was investigated to determine if such release is significant following spinal cord injury. The relationship of extracellular levels of hydroxyl radicals and hydrogen peroxide obtained by microdialysis sampling and oxidized protein levels in tissue to neutrophil infiltration following spinal cord injury was examined. Neither of the reactive oxygen species were elevated in the site of spinal cord injury relative to their concentrations in normal tissue at a time (24 h) when the numbers of neutrophils were maximum in the site of injury. Surprisingly, ablation with a neutrophil antiserum actually increased the level of oxidized proteins in Western blots. Thus, our findings are (1) that neutrophils, which infiltrate the site of damage following a spinal cord injury, do not release detectable quantities of reactive oxygen species; and (2) that the presence of neutrophils reduces the concentrations of oxidized proteins in the site of spinal cord injury. Therefore, release of reactive oxygen species by neutrophils does not contribute significantly to secondary damage following spinal cord injury. Reduced levels of oxidized proteins in the presence of neutrophils may reflect removal of damaged tissue by neutrophils.

The National NeuroAIDS Tissue Consortium: a new paradigm in brain banking with an emphasis on infectious disease.

The National NeuroAIDS Tissue Consortium (NNTC) was founded in 1998, in response to the scientific need for well-characterized central nervous system (CNS) and peripheral nervous system (PNS) tissues and fluids from HIV-infected individuals. In addition to performing the routine functions of non-transplant anatomic tissue banks, the Consortium offers a unique model for the integration of independent research entities in order to provide well-characterized tissues and fluids for the international research community. Herein, we describe the structure of the Consortium, pointing out the inherent strengths of linking together multiple independent sites for the purpose of banking HIV-infected nervous system tissues. We describe the neuropathology protocol that was adopted and successfully implemented at the four participating banks of the Consortium.

Oncocytoma in melanocytoma of the spinal cord: case report.

OBJECTIVE AND IMPORTANCE: Oncocytoma in the central nervous system is extremely unusual. The first reported example of oncocytoma in a melanocytoma of the spinal cord was successfully excised, and its pathological appearance is described. CLINICAL PRESENTATION: A 71-year-old woman presented with a 25-year history of back pain and myelographic evidence of a lumbar spinal cord mass. After declining surgical treatment for two decades, she elected eventually to have the mass excised. Preoperative magnetic resonance imaging revealed a large intraspinal mass that spanned spinal levels L3 through S1. TECHNIQUE: The mass was excised en bloc through posterior laminectomies, and histopathological analysis revealed a benign neoplasm composed predominantly of monotonous sheets of plump oncocytes. Electron microscopy confirmed that the cytoplasm of the oncocytes was packed full of mitochondria. Focal areas of the tumor contained spindle cells, with abundant intracytoplasmic granular deposits of brown melanin pigment that contained melanosomes. Positive Fontana-Masson, HMB-45, and S-100 staining confirmed the final diagnosis of melanocytoma, oncocytic variant. CONCLUSION: The first reported case of oncocytoma arising in spinal melanocytoma is described. After surgical excision, the patient recovered completely and has remained free of symptoms for 4 years.

A novel mechanism of CD4 lymphocyte depletion involves effects of HIV on resting lymphocytes: induction of lymph node homing and apoptosis upon secondary signaling through homing receptors.

Recently, we reported that abortive HIV infection of resting human T lymphocytes up-regulated expression of CD62L, the receptor for homing to lymph nodes (LNs), and enhanced homing of these cells from the blood into the LNs (Wang et al., 1997, Virology 228:141). This suggested that HIV-induced homing of resting lymphocytes (which comprise >98% of all lymphocytes) may be a major mechanism for the reduction of CD4+ lymphocytes in the blood of infected individuals. This mechanism also could be partially responsible for the lymphadenopathy that often develops at the same time that CD4+ lymphocytes are disappearing from the blood. In this study, we show that secondary signaling through the homing receptors (CD62L, CD44, CD11a) of abortively infected resting CD4+ T lymphocytes induced apoptosis. These signals would occur as the cells home into the LNs. Apoptosis did not occur after secondary signaling through some other receptors (CD26, CD4, CD45, and HLA class I) or in HIV-exposed resting CD8+ lymphocytes signaled through the homing receptors. These findings indicate that HIV-induced homing of resting CD4+ lymphocytes to LNs results in death of many of these cells. This was confirmed in the LNs of SCID mice that were i.v. injected with HIV-exposed resting human lymphocytes. Thus, these effects of HIV upon binding to resting CD4+ T lymphocytes, which are not permissive for HIV replication, may significantly contribute to their depletion in vivo. These findings also offer an explanation for the bystander effect observed in the LNs of AIDS patients, whereby cells not making virus are dying.

A host defense role for a natural antiviral substance in the nervous system.

The pathogenesis of virus infections of the nervous system (NS) is regulated by host defenses. The defensive role of a major constitutive antiviral substance was studied by determining its distribution in the human nervous system, its concentration and the ability of this viral inhibitor to protect mice against viral infection. The 4000 kDa inhibitor complex in the human nervous system was detected in brain gray and white matter, spinal cord, and sciatic nerve but not in human cerebrospinal fluid. The inhibitor was found in the extracellular medium incubated with minced murine brain. The inhibitory titer ranged from approximately 50 to 200 antiviral units per gram against polio 1, Semliki Forest, Banzi, mengo, Newcastle disease and herpes simplex 1 viruses. The inhibitor is composed of lipid and essential protein and carbohydrate moieties as determined by enzymatic inactivation. Protection of inhibitor-treated mice was demonstrated against both an alphavirus and a picornavirus. Thus a natural defensive role for the broadly antiviral inhibitor is suggested by its constitutively high concentration, wide distribution in nervous system tissues, presence in extracellular fluid and its ability to provide protection in infected mice.

Pulmonary lymphomatoid granulomatosis in acquired immunodeficiency syndrome: lesions with Epstein-Barr virus infection.

We report the clinicopathologic characteristics of pulmonary lymphomatoid granulomatosis (LYG) in 11 patients (identified from a series of 330 consecutive patients who underwent autopsy between 1984 and 1995 at the University of Texas Medical Branch at Galveston, Texas) with a diagnosis of acquired immunodeficiency syndrome (AIDS). We used immunohistochemical stains, RNA in situ hybridization (ISH), and gene rearrangement studies to identify the immunophenotype and the presence or absence of Epstein-Barr virus (EBV) infection. All of the patients were men ranging in age from 27 to 65 years (mean age, 38.6 yr). Autopsy lungs of 21 age-matched controls were examined for EBV using ISH; these included 9 patients with AIDS who did not have pulmonary lesions and 12 HIV-negative individuals who died accidentally (mean age, 38.6 yr). All of the 11 pulmonary lesions showed the gross and microscopic characteristics of LYG, with zonal necrosis and prominent angioinvasion. The tumor nodules consisted of a mixture of atypical large lymphocytes, with vesicular nuclei and prominent nucleoli and with a background of small and intermediate-size lymphocytes, histiocytes, and plasma cells. The large lymphocytes were CD20 positive, consistent with a B-cell phenotype. Ten of the 11 cases demonstrated EBV1-encoded RNA and CD20 positivity in the large, atypical lymphocytes by double labeling. One patient showed EBV positivity in CD20-negative, CD45RO-positive large cells, but these cells were CD3 negative and showed a monoclonal heavy chain gene rearrangement by polymerase chain reaction, indicating that these were of B-cell origin. Aberrant CD43 coexpression was identified in four cases. EBV latent membrane protein was demonstrated in 9 of 11 cases by immunohistochemical stains. The lungs of all of the 21 control patients were negative for EBV by ISH. We conclude that, in our series, AIDS-associated LYG is a B-cell neoplasm and that it has a strong association with EBV infection.

Proteolysis in the myelopathy of acquired immunodeficiency syndrome: preferential loss of the C-8 component of myelin basic protein.

Many patients with AIDS have a myelopathy characterized by vacuolization of spinal cord white matter. The biochemical and molecular changes underlying this myelin disturbance have not yet been characterized. Myelin basic protein (MBP) is potentially important because it is a key structural protein of myelin with roles in compaction and stabilization. In the present study, we describe the steady-state protein concentration of MBP in 46 patients with AIDS and 12 control subjects at autopsy. Patients with myelopathy exhibited no change in the abundance of the predominant 18.5- and 17.2-kd isoforms, but a 14-kd MBP-immunoreactive degradation fragment was increased significantly. MBP degradation correlated significantly with the severity of histopathologic changes, including neutral lipid deposition, the density of vacuolated fibers, and the number of ferritin-stained activated microglia. Alkaline gel electrophoresis of isolated MBP showed preferential loss of the least cationic isomer (C-8). The concentration of MBP RNA in slot blots was normal in cords exhibiting myelopathy, and the ratio of mRNA corresponding to the 18.5- and 17.2-kd MBP isoforms, measured using reverse transcriptase-PCR, was not altered. This study suggests that mononuclear phagocyte-mediated degradation of MBP may play a role in AIDS myelopathy, and the preferential loss of the C-8 component of MBP may have mechanistic implications.

Mononuclear phagocyte hydrolytic enzyme activity associated with cerebral HIV-1 infection.

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.