A two-culture method for exposure of human brain organotypic slice cultures to replicating human immunodeficiency virus type 1

To evaluate the effect of HIV-1 virus on neural cells, we have developed a method to culture human fetal organotypic brain slices in the presence of live virus. Brain slices were placed on semipermeable hydrophilic membrane inserts, resting on top of wells that contain cultured H9 T-cells chronically producing HIV-1. This system allows free exposure of the brain slices to HIV-1, HIV-1 proteins, and other molecules released by the infected T-cells. After specific lengths of time in culture, slices were stained for viability with Calcein-AM and propidium iodide, for neural cell markers such as GFAP, nestin and β-III-tubulin, tested for cell proliferation, and analyzed by fluorescent and confocal microscopy. When cultured in the presence of neural progenitor medium lacking serum, slices were viable and maintained active cell replication for at least 3 weeks in culture, without significant cell death. By comparison with slices co-cultured with uninfected T-cells or with medium alone, slices cultured in the presence of HIV-1 showed increased nestin and GFAP. Moreover, in slices exposed to HIV-1-producing H9 cells, regions of nestin stain were, over time in culture, replaced with GFAP stain. This suggested the process of gliosis often found in brains of HIV-1 infected individuals. This co-culture method can be used to model the dynamics and the microenvironment of brain tissue exposed to HIV-1 and can potentially be used to test therapies directed at preventing HIV-1-induced neural damage.     

Effects of extracellular human immunodeficiency virus type 1 vpr protein in primary rat cortical cell cultures

Recent evidence suggests that HIV-1 Vpr exists in soluble form in the serum and cerebrospinal fluid (CSF). Further, its abundance in the bloodstream, and the CSF, and its activity on other cell types suggest that it could have an effect on brain activity. Using mixed embryonic rat brain cultures as a model to examine the effects of physiological concentrations of extracellular Vpr protein, Vpr-induced cell death was observed. We also observed similar Vpr-induced effects in enriched primary cortical rat astrocytes, as well as in the C6 glioma cell line. Vpr-induced cell death observed in the astrocytic cells appeared to be caused primarily by a necrotic mechanism, although a few apoptotic nuclei were also present. We did not observe Vpr-induced effects on any primary cortical neurons, although we did observe Vpr-induced cell death in hippocampal neurons and astrocytes. Finally, we observed no cell cycle effects due to extracellular Vpr protein. This data points out that different cell types are affected by the toxic effects of extracellular Vpr protein, and that differential toxic effects of extracellular Vpr protein are observed in similar cell types.     

The gp 120 glycoprotein of human immunodeficiency virus type 1 binds to sensory ganglion neurons

Using immunofluorescence microscopy we found that gp 120 binds to the surface of rat dorsal root ganglia neurons and human neuroblastoma cells but not to rat fibroblasts or glial cells. The binding of gp 120 to neurons was eliminated by pretreatment with trypsin, which removes cell-surface proteins, but not with chloroform: methanol, which removes glycolipids. As control, neuronal staining by antisulfatide antibodies was eliminated by pretreatment with chloroform: methanol but not with trypsin. The gp 120 binding to neurons was also inhibited by the mouse monoclonal antibody 01, which binds to galactocerebroside and cross-reactive glycoproteins. These studies suggest that the receptor for gp 120 on the surface of the dorsal root ganglia neurons is a glycoprotein. This interaction may mediate the effects of human immunodeficiency virus type 1 in sensory neuropathy.     

Human immunodeficiency virus type 1 alters brain-derived neurotrophic factor processing in neurons

The molecular mechanisms leading to synaptic simplification and neuronal apoptosis in human immunodeficiency virus type 1 (HIV-1)-positive subjects are unknown. The HIV protein gp120 reduced the length of neuronal processes similarly to the proneurotrophin pro-brain-derived neurotrophic factor (proBDNF). Intriguingly, the effects of both proBDNF and gp120 were blocked by inhibitors of the p75 neurotrophin receptor, suggesting that proBDNF and gp120 share a similar mechanism of neurotoxicity. Therefore, we tested the hypothesis that gp120 affects the release of proBDNF. Using rat primary neurons, we observed that gp120 promotes a time-dependent intracellular and extracellular accumulation of proBDNF concomitantly with a decrease in mature BDNF. A similar imbalance in the ratio proBDNF/mature BDNF was confirmed in postmortem brains of HIV-positive subjects cognitively impaired and motor impaired. Therefore, it is conceivable to formulate the hypothesis that HIV neurotoxicity includes a gp120-mediated alteration of BDNF processing. To determine the cellular mechanism whereby gp120 produces an accumulation of proBDNF, we examined the levels of intracellular and extracellular enzymes that proteolytically cleave proBDNF furin and tissue plasminogen, respectively. In rat neurons exposed to gp120, intracellular furin levels decreased before cell death, whereas tissue plasminogen changed only during apoptosis. Our data suggest that HIV, through gp120, reduces proBDNF processing by affecting furin levels, and therefore causes an altered balance between antiapoptotic and proapoptotic neurotrophins. Our studies identify a new mechanism that may explain how HIV promotes neuronal injury.     

Cerebrospinal fluid neopterin in human immunodeficiency virus type 1 infection

We evaluated cerebrospinal fluid (CSF) concentrations of neopterin, a putative marker of activated macrophages, in 97 subjects infected with human immunodeficiency virus type 1 who had a spectrum of neurological complications. The highest CSF neopterin concentrations occurred in those with neurological opportunistic infections, primary central nervous systems lymphoma, and acquired immunodeficiency syndrome (AIDS) dementia complex. In general, the CSF concentration of neopterin was independent of CSF cell count and blood-brain barrier disruption to albumin. In the patients with AIDS dementia complex, CSF neopterin concentrations correlated with severity of disease and decreased in conjunction with clinical improvement following treatment with zidovudine. These results suggest that CSF neopterin, although not disease-specific, may be useful as a surrogate marker for the presence of AIDS dementia complex and its response to antiviral therapy.     

Astroglial reaction pattern in human immunodeficiency virus type 1 infected brains

The reaction pattern of astrocytes was investigated by means of immunohistochemistry and morphometry in 36 brain regions of human immunodeficiency virus type 1 infected patients and of normal controls. The numerical density of astrocytes immunoreactive for glial fibrillary acidic protein (GFAP) was determined. In HIV1 infected brains, the number of GFAP-positive astrocytes was significantly increased in all investigated brain regions as compared with normal controls. The increase in number of GFAP-positive, reactive astrocytes might play a crucial role in triggering pathogenetic mechanisms leading to cell damage and death in HIV1 infected brains.     

Long-latency event-related potentials in asymptomatic human immunodeficiency virus type 1 infection

As part of the Medical Research Council prospective study of the neurological and neuropsychological complications of human immunodeficiency virus (HIV) infection, long-latency event-related potentials were recorded in a cohort of homosexual and bisexual men. The latencies and amplitudes of the potentials, recorded from three scalp sites, were compared with the scores from neuropsychological tests of memory, attention, and concentration and with markers of immune function. The findings from 94 men were analyzed in the cross-sectional study of whom 47 were HIV seropositive without symptoms or signs of HIV type 1 (HIV-1) infection, 24 had progressed to the symptomatic stages of the disease, and 23 were persistently HIV seronegative. There were no consistently significant differences between the three subject groups in mean latencies and amplitudes of the P300 and N200 or in the numbers of abnormal P300 latencies. There were no significant correlations between either the neuropsychological tests scores or the immune measures (CD4 lymphocyte count and β₂ microglobulin level) and the neurophysiological parameters. On repeated testing an average of 2 years later, there was no evidence of a significant trend towards deterioration in 30 HIV-seropositive subjects who remained asymptomatic compared with 22 HIV seronegatives. These findings indicate that there is no neurophysiological evidence of cognitive dysfunction in the asymptomatic stages of HIV-1 infection.     

Neuromuscular complications of the human immunodeficiency virus type 1 infection

Neuromuscular disorders are the most frequent neurologic complications associated with human immunodeficiency virus (HIV) infection and AIDS. Although neurologic disorders are frequently overlooked, they add considerable morbidity and mortality to patients with HIV infection. It is critically important to properly diagnose and treat these neuromuscular complications, which leads to substantial improvement in patients' quality of life. Distal symmetric polyneuropathy is the most common form of peripheral neuropathy in HIV infection. It occurs mainly in patients with advanced immunosuppression and may also result from the neurotoxicity of several antiretroviral agents. Myopathy may occur at any stage of HIV disease and has also been described as a toxic side effect of zidovudine. Here we review the clinical features, diagnostic approach, and pathogenetic mechanisms of the neuromuscular complications of HIV infection. We also discuss management strategies and the results of clinical trials for the treatment of these disorders.     

Lithium therapy for human immunodeficiency virus type 1-associated neurocognitive impairment

The objective of this study was to assess lithium safety and tolerability and to explore its impact on cognition, function, and neuroimaging biomarkers in human immunodeficiency virus (HIV)-infected subjects with cognitive impairment. Fifteen cognitively impaired HIV-infected subjects were enrolled in this 10-week open-label study of lithium 300 mg twice daily. Neuroimaging was performed at baseline and following 10 weeks of treatment and included magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), and functional MRI (fMRI). Thirteen of the 14 subjects (93%) that complied with the study visits were able to complete the study on lithium and 11 out of 13 (79%) completed the study at the originally assigned dose of 300 mg twice daily. There were no significant changes in CD4⁺ lymphocyte cell count and plasma HIV RNA. Cognitive performance and depressive mood did not improve significantly after the 10-week lithium treatment; however, neuroimaging revealed a decrease in the glutamate+glutamine (Glx) peak in the frontal gray matter, increased fractional anisotropy, and decreased mean diffusivity in several brain areas, and changes in brain activation patterns, suggestive of improvement. These results suggest that lithium can be used safely in HIV-infected individuals with cognitive impairment. Furthermore, the neuroimaging results suggest that lithium may improve HIV-associated central nervous system (CNS) injury; thus, further investigations of lithium as an adjunctive treatment for HIV-associated cognitive impairment are warranted.     

A patient with progressive myelopathy and antibodies to human T-cell leukemia virus type I and human immunodeficiency virus type 1 in serum and cerebrospinal fluid

A 52-year-old human immunodeficiency virus type 1-seropositive bisexual black man was evaluated at UCLA because of the recent onset of progressive lower-extremity weakness. Initial neurologic examination showed that the patient's distal weakness was greater than his proximal weakness, with bilateral foot drop and electrophysiologic evidence of denervation in the distal lower extremities. Magnetic resonance imaging of the brain and spinal cord disclosed no abnormalities. Subsequent neurologic evaluation 8 months later showed a myelopathy, with progression of lower-extremity weakness, spasticity, and flexor spasms, and urinary incontinence, as well as the peripheral neuropathy noted previously. A second magnetic resonance imaging scan of the brain showed patchy foci of increased signal intensity in white matter and cortex, with mild generalized cerebral and cerebellar atrophy and no lesions in the spinal cord. Specimens of the patient's serum and cerebrospinal fluid contained antibodies to human immunodeficiency virus type 1. Additionally, specimens of his serum and cerebrospinal fluid were tested for antibody to human T-cell leukemia virus type I by Western blotting and radioimmunoprecipitation, and found to be positive for human T-cell leukemia virus type I gag, env, and tax antibodies. The primary cause of severe myelopathy in this patient may be infection with human T-cell leukemia virus type I rather than with human immunodeficiency virus type 1. Treatment with prednisolone resulted in improvement of the lower-extremity weakness, reduction in flexor spasms, and slower but significant improvement in urinary symptoms. Patients who are infected with human immunodeficiency virus type 1 and have unusual motor findings should be tested for concomitant human T-cell leukemia virus type I infection.     

Neurosyphilis in human immunodeficiency virus type 1-seropositive individuals. A prospective study.

The prevalence of neurosyphilis in human immunodeficiency virus type 1 (HIV-1)-seropositive (HIV+) persons was assessed during the course of a study of the neurological complications of HIV-1 infection. One hundred sixty-six asymptomatic HIV+ subjects, 63 neurologically symptomatic HIV+ subjects, and six at-risk HIV-1-seronegative (HIV-) control subjects underwent cerebrospinal fluid (CSF) analysis on entry into this longitudinal study. Three (1.8%) of the asymptomatic HIV+ subjects had both a reactive CSF VDRL test and a reactive CSF fluorescent treponemal antibody-absorption (FTA-ABS) test. Two of these three subjects had a history of appropriately treated early syphilis, and all had a reactive serum rapid plasma reagin test. Of the 63 neurologically symptomatic HIV+ subjects, one patient with dementia had both a reactive CSF VDRL test and a fluorescent treponemal antibody-absorption test. Subjective improvement in cognitive skills followed high-dose, intravenous penicillin therapy. Another subject had a penicillin-responsive myelopathy accompanied by a reactive CSF fluorescent treponemal antibody-absorption test result, but a nonreactive CSF VDRL. Unsuspected neurosyphilis is relatively common in our population of asymptomatic HIV+ subjects and may be responsible for neurological disease in a significant minority of neurologically symptomatic HIV+ persons. Cerebrospinal fluid examination should be performed in all HIV+ persons with a history of syphilis or serological evidence of syphilis, regardless of prior treatment. Additionally, neurosyphilis should be considered in the differential diagnosis of neurological disease in any HIV+ person.     

Neuropsychological deficits in human immunodeficiency virus type 1 clade C-seropositive adults from South India

Most studies of cognitive functioning in human immunodeficiency virus type 1 (HIV-1)-seropositive (HIV-1+) subjects have been done in the United States and Europe, where clade B infections predominate. However, in other parts of the world such as South India, where clade C HIV is most common, the prevalence of HIV-1 is increasing. Standardized neuropsychological tests were used to assess cognitive functioning in a sample of 119 adults infected with clade C HIV-1 who were not on antiretroviral medications. The subjects did not have neurological or psychiatric illness and were functioning adequately. Neuropsychological test performance was compared with gender-, age-, and education-matched normative data derived from a sample of 540 healthy volunteers and a matched cohort of 126 healthy, HIV-1-seronegative individuals. Among the seropositive subjects, 60.5% had mild to moderate cognitive deficits characterized by deficits in the domains of fluency, working memory, and learning and memory. None of the subjects had severe cognitive deficits. The HIV-1+ sample was classified into groups according to the level of immune suppression as defined by CD4 count (<200, 201–499, and >500 cells/mm³) and viral load (<5000, 5001–30,000, 30,001–99,999, 100,000–1,000,000, and >1,000,001 copies). Although the most immunosuppressed group (CD4 count <200 cells/mm³ or viral load >1,000,001 copies) was small, their rate of impairment in visual working memory was greater when compared to groups with better immune functioning. Mild to moderate cognitive deficits can be identified on standardized neuropsychological tests in clade C-infected HIV-1+ adults who do not have any clinically identifiable functional impairment. The prevalence of cognitive deficits is similar to that reported in antiretroviral treatment-naïve individuals infected with clade B virus in the western world.     

Cerebrospinal fluid anti-cerebellar soluble lectin antibodies in human immunodeficiency virus type 1 infection.

Cerebrospinal fluid samples from 14 human immunodeficiency type 1 (HIV-1) seropositive patients in various stages of HIV infection were tested for the presence of autoantibodies to an endogenous manose-binding protein, the cerebellar soluble lectin (CSL), which has recently been found to be detected in a high proportion of patients with multiple sclerosis. An immunoblotting test was used with rat CSL as antigen. Seven patients were positive for anti-CSL and seven were negative. The seven anti-CSL-positive patients had signs of intrathecal immunoglobulin G production measured as an elevated IgG index, while the seven anti-CSL-negative patients had a normal IgG index. There was no apparent relation between infectious stage and the presence of anti-CSL. Immunological reactions such as anti-CSL autoantibodies may be a similar pathogenic mechanism in HIV and multiple sclerosis brain disease.     

Specific neurologic complications of human immunodeficiency virus type 1 (HIV-1) infection in children

Pediatric human immunodeficiency virus type 1 (HIV-1) infection is endemic throughout southern Africa. Neurologic complications are described in 20% to 60% of published series, mostly related to HIV-1 encephalopathy. With increasing HIV prevalence, more atypical cases are presenting. We present, as illustrative cases, seven children (three girls) with unusual neurologic sequelae as a consequence of HIV-1 infection. The median age at presentation was 33 months (range 7 months-6 years). Five of the seven children were developmentally normal before presentation. They presented with progressive multifocal leukoencephalopathy, myelopathy, intractable seizures, acute vasculitis and blindness, hemiplegia, peripheral neuropathy, and paraspinal lymphoma. Neuroimaging of the brain was performed in five patients, of whom one had basal ganglia calcification. All children had poor outcome with incomplete recovery or continued deterioration. In conclusion, children with HIV-1 infection who survive beyond the first year of life can present with a wide variety of neurologic complications. A similar spectrum of neurologic manifestations is likely to occur in other sub-Saharan African countries, characterized by high HIV prevalence. The case histories demonstrate that the neurologic features of pediatric HIV infection do not easily fit into a simplified classification system.     

Human immunodeficiency virus type 1 Tat-mediated cytotoxicity of human brain microvascular endothelial cells

Human immunodeficiency virus (HIV)-1 infection is often complicated with neurologic disorders, but the pathogenesis of HIV-1 encephalopathy is incompletely understood. Tat (HIV-1 transactivator protein) is released from HIV-1-infected cells and has been detected in the sera and cerebrospinal fluid of HIV-1-infected patients. Tat, along with increased inflammatory cytokines such as interferon-gamma (IFN-gamma), have been implicated in the pathogenesis of HIV-1-associated blood-brain barrier dysfunction. The present study examined the effects of Tat and IFN-gamma on human brain microvascular endothelial cells (HBMECs), which constitute the blood-brain barrier. Tat produced cytotoxicity of HBMECs, but required IFN-gamma. IFN-gamma treatment of HBMECs up-regulates vascular endothelial growth factor receptor-2 (VEGFR2/KDR), which is known to be the receptor for Tat. Tat activated KDR in the presence of IFN-gamma, and Tat-mediated cytopathic changes involve its interaction with KDR and phosphatidylinositol 3-kinase (PI3K). Further understanding and characterization of Tat-HBMEC interactions should help us understand HIV-1 neuropathogenesis and develop strategies to prevent HIV-1 encephalopathy.