Cerebrospinal fluid HIV-1 p24 antigen and culture: sensitivity and specificity for AIDS-dementia complex

Measurement of Human Immunodeficiency Virus p24 Antigen in Human Cerebrospinal Fluid With Digital Enzyme-Linked Immunosorbent Assay and Association With Decreased Neuropsychological Performance

New tools are needed to understand human immunodeficiency virus central nervous system involvement. Testing 15 cerebrospinal fluid (CSF) samples for p24 antigen, using a high-sensitivity assay, we found a strong correlation trend between CSF p24 concentration and worse neuropsychological performance.

Productive infection of human neural progenitor cells by R5 tropic HIV-1: opiate co-exposure heightens infectivity and functional vulnerability

OBJECTIVE

HIV type-1 (HIV-1) causes a spectrum of central nervous system (CNS) complications; many are worsened by opiate co-exposure. Human neural progenitor cells (hNPCs) give rise to all CNS neurons and macroglia. We tested the hypothesis that hNPC maturation and fate are altered by HIV and opiates, contributing to HIV-1-related neuropathology. Reports of hNPC infection remain controversial. We rigorously examined this question, testing whether hNPCs propogated infection, and whether HIV affected hNPCs absent their infection.

DESIGN AND METHODS

Primary hNPCs were characterized over multiple passages. Following R5 HIV-1BaL exposure, p24, Nef, and tat assays monitored infection; a serial dilution approach tested infection transfer to naive hNPCs. Bromodeoxyuridine uptake, population doubling time, and immunostaining assessed proliferation and differentiation. Morphine co-exposure assessed opiate interactions. Supernatant from HIV-1BaL-infected PBMCs (HIVsup), HIV-1BaL, and ultraviolet light-inactivated HIVsup were compared to test effects of inflammatory milieu versus virus or infection per se.

RESULTS

The hNPCs (CD4/CD8/Iba/CXC3CL1/CD11b) were infectable and could transfer infection to naive hNPCs. Infection was partly blocked by maraviroc, implicating CCR5. HIVsup reduced hNPC proliferation and caused premature differentiation into neurons/astroglia. Effects on proliferation were due to soluble factors/viral proteins, not infection per se. Morphine co-exposure exacerbated certain functional consequences of HIVsup, and sustained the infection of hNPCs.

CONCLUSION

hNPCs can be infected and propagate virus in vitro. hNPCs or their progeny may represent an underappreciated viral reservoir. Factors from infected cells alter hNPC proliferation and neural cell maturation, which likely compromises CNS structure and function. Morphine-HIV interactions may worsen dysfunction and sustain infection.

Regulation of neural cell survival by HIV-1 infection

Infection by the lentivirus, human immunodeficiency virus type 1 (HIV-1), results in a variety of syndromes involving both the central (CNS) and the peripheral (PNS) nervous systems. Productive HIV-1 infection of the CNS is chiefly detectable in perivascular macrophages and microglia. HIV-1 encoded transcripts and proteins have also been detected in the PNS; however, productive viral replication appears to be sparse and restricted to the macrophage cell population. Despite the absence of productive infection of neurons, HIV-1 infection has been associated with neuronal loss in distinct regions of the brain. Neuronal cell loss may occur through both necrosis and apoptosis, although neuronal apoptosis appears to be a feature of AIDS, as only rare apoptotic neurons have been demonstrated in a few pre-AIDS cases. Although there is no clear consensus as to the underlying mechanism of HIV-induced neuropathogenesis, two complementary concepts predominate. Firstly, HIV-1 encoded proteins injure neurons directly without requiring the intermediary functions of nonneuronal cells. Alternatively, neuronal apoptosis may result indirectly from the secretion of neurotoxic host molecules by resident brain macrophages or microglia in response to HIV-1 infection, stimulation by viral proteins or immune activation. Herein, we review the neurological disorders and their underlying mechanisms associated with HIV infection, focusing on HIV-associated dementia (HAD) and HIV sensory neuropathy (HIV-SN). The evidence that neuronal loss in HIV-1-infected individuals may be due to neuronal apoptosis is then discussed. This review also summarizes the current data supporting both the direct and indirect mechanisms by which neuronal death may occur during infection with HIV-1 or the closely related lentiviruses SIV and FIV. Lastly, strategies are examined for treating or preventing HAD by targeting specific neurotoxic mechanisms.

AIDS dementia complex

Human immunodeficiency virus (HIV) infection is often complicated by the development of AIDS dementia complex (ADC). This article examines the typical and atypical presentations of ADC, along with aspects of the prevalence and natural history of the disorder. Salient aspects of the neuropathology, neurovirology, neuroimmunology, and pathogenesis are also considered. The intricacies of management of ADC, especially in the era of highly active antiretroviral therapy, are fully evaluated. Finally, this information is synthesized into an approach to the diagnosis of ADC in a particular patient.

Progressive dendritic pathology in cynomolgus macaques infected with simian immunodeficiency virus

Neuronal pathology in acquired immunodeficiency syndrome (AIDS) is of interest in relation to cognitive impairment in AIDS patients and from the broader perspective of the pathogenesis of neurodegeneration. Cortical dendritic spine loss has been described in patients with AIDS and the aim of this study was to test the hypothesis that similar pathology is present in cynomolgus macaques infected with simian immunodeficiency virus (SIV). These animals develop an AIDS-like illness, but multinucleated giant cell encephalitis is not a feature and CNS virus load is found to be very low. Four animals infected for 2.5-3 months and four infected for 2-3 years were compared with four controls. The Golgi-Cox technique was employed to demonstrate dendritic morphology in the frontal cortex and the diameter of apical dendrites, dendritic spine density and dendritic spine lengths were measured in layer V pyramidal cells. Immunohistochemistry for microtubule-associated protein-2 (MAP-2), MHC class II and glial fibrillary acidic protein (GFAP) was also performed. In infected animals there was progressive spine loss and atrophy of remaining spines with loss of MAP-2 immunoreactivity at late time points. No parallel increase in GFAP immunostaining or MHC-class II expression in microglial cells was seen. We conclude that progressive neuronal dendritic pathology is a feature of SIVmac251 infection of cynomolgus macaques and is apparent relatively early in disease. Furthermore, dendritic abnormalities occur in the absence of either multinucleated giant cell pathology or substantial CNS virus load.

An immunovirological study of central nervous system involvement during HIV-1 infection of chimpanzees

Chimpanzees infected with human immunodeficiency virus type 1 (HIV-1) are used to model acquired immunodeficiency syndrome (AIDS). Since the central nervous system (CNS) is involved in AIDS, we performed an immunovirological study in 18 chimpanzees inoculated up to 87 months prior to the study (mean, 45 months) with HIV-1 and 8 uninfected controls. Serum and cerebrospinal fluid (CSF) IgG and albumin levels of infected chimpanzees never exceeded those of controls. The CSF/serum albumin ratio was elevated in 1 of 18 infected chimpanzees compared to controls; however, all animals had an elevated ratio indicating a more open blood-brain barrier relative to humans. The intrathecal IgG production index was elevated in only 1 of 18 infected chimpanzees compared to controls. Identical serum and CSF IgG bands were found by isoelectric focusing in 2 of 8 controls and in 1 of 18 infected chimpanzees. None of these bands reacted with recombinant HIV-1 p24gag or gp 120env. HIV-1 was isolated from the peripheral blood of 4 of 18 infected chimpanzees but never from the paired CSF samples. Anti-HIV-1 antibody was detected by a enzyme-linked immunosorbent assay in 18 of 18 paired serum and CSF samples and by Western blot in 18 of 18 serum and 13 of 18 CSF samples from infected chimpanzees without a difference in pattern. Polymerase chain reaction analysis on brain tissue of one animal was negative for HIV-1 sequences. Our results demonstrate that, unlike human infection, chimpanzees inoculated with HIV-1 show no evidence of isolatable virus in the CSF and no evidence of intrathecal anti-HIV-1 antibody synthesis up to several years after experimental infection. The lack of CNS involvement may contribute to the delay or suppression of clinical disease in infected chimpanzees.

AIDS dementia complex and HIV-1 brain infection: clinical-virological correlations

To evaluate the presence and distribution of central nervous system infection by human immunodeficiency virus type 1 (HIV-1), we used immunohistochemical methods to map the HIV-1 p24 core protein in the brains of 55 autopsied patients with acquired immunodeficiency syndrome (AIDS). In a subset of 40 of these patients who had undergone antemortem neurological evaluation of the AIDS dementia complex (ADC), we analyzed the relation between the severities of the viral infection and clinical dysfunction. Viral antigen was detected in macrophages and cells with morphological and immunohistochemical characteristics of microglia as well as multinucleated cells. The distribution of antigen-positive cells preferentially involved certain deep brain structures, especially the globus pallidus, other basal ganglia nuclei, and the central white matter. Overall, the presence and frequency of infected cells were highly correlated with the histological findings of multinucleated-cell encephalitis and in general with the clinical ADC stage. However, infection was often more limited than might be "anticipated" from the severity of patients' clinical dysfunction: Only 61% of patients with at least ADC stage 1 had detectable antigen and of these only approximately 30% of the brain sections were antigen positive. These results suggest a pathogenetic model of ADC where virus- or cell-coded toxins amplify the effect of limited brain infection.

Review of antiretroviral therapy in the prevention of HIV-related AIDS dementia complex (ADC)

Following the introduction of zidovudine, a major decline was noted in the incidence of AIDS dementia complex (ADC). Several factors point to a causal relationship. It is important now to review the evidence derived from clinical, cerebrospinal fluid (CSF) and neuropathological studies to determine whether the protective effect of zidovudine on the brain of patients with HIV infection has implications for clinical practice. It has been demonstrated in clinical studies that patients with ADC may improve with zidovudine treatment and that the development of ADC is rare in patients receiving the nucleoside analogue long term. In support of these clinical findings, CSF studies have revealed that the presence of HIV-1 p24 antigen has diagnostic value in patients with suspected ADC and that p24 antigen levels decline with zidovudine treatment. Supporting evidence has also come from neuropathological studies, which have demonstrated that zidovudine decreases HIV-specific neuropathological abnormalities. Recently, the Multicenter AIDS Cohort Study reported conflicting data which suggested that antiretroviral therapy is not protective against ADC; however, several methodological weaknesses of this study limit the general applicability of the findings and the conclusions. In view of the increasing body of evidence in support of the efficacy of zidovudine in the prevention and management of ADC in patients with HIV-1 infection, it seems reasonable to include this antiretroviral agent in any combination treatment regimen. Many questions remain to be answered, however, before management of such patients is optimised. Meanwhile, in order to increase both insight and evidence, it is imperative that ongoing and future clinical trials with antiretroviral drugs closely monitor all cases of progression to ADC.(ABSTRACT TRUNCATED AT 250 WORDS)