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Involvement of dopamine in the progression of AIDS Dementia Complex.

HIV compromises immunological functions. Immune responses are regulated to a great extent by several molecules such as cytokines, neurotransmitters and hormones which interact with different immune effector cells and ultimately mediate the homeostatic responses to disease. Among these mediators, dopamine plays an important role. In this article we review AIDS Dementia Complex (ADC) and describe lines of evidence implying increased dopamine availability as a potent mediator of neurologic deficits in HIV infection and a factor exhibiting adverse effects on the progression of ADC.

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HIV-1 reverse transcriptase sequence in plasma and cerebrospinal fluid of patients with AIDS dementia complex treated with Abacavir.

OBJECTIVE: To assess HIV-1 RNA levels and the relationship between HIV-1 reverse transcriptase (RT) genotype from plasma and cerebrospinal fluid (CSF) during treatment with abacavir (Ziagen, ABC) or placebo in combination with stable background therapy (SBG) in subjects with AIDS dementia complex (ADC) (study CNA3001). DESIGN: One-hundred and five HIV-1 infected adults with ADC were randomized to receive either ABC (600 mg twice daily) or ABC-matched placebo (twice daily) in addition to SBG for 12 weeks. METHODS: Plasma and CSF were collected for population sequencing at baseline and week 12 (CSF optional). Sequences were analyzed for mutations associated with resistance to nucleoside reverse transcriptase inhibitors (NRTI). RESULTS: Sixty out of sixty-seven subjects with baseline plasma HIV-RT sequence data harbored virus with > or = 1 NRTI-associated mutations; 50 out of 67 had the M184V mutation. At week 12, more subjects in the ABC group had plasma HIV-1 RNA < or = 400 copies/ml than the SBG group (46% versus 13%, P = 0.002). Non-response to ABC was associated with multiple baseline zidovudine (ZDV)/stavudine (d4T)-associated mutations. Baseline RT mutation patterns differed in 14 out of 21 (67%) paired samples from plasma and CSF. Four subjects experienced > 1 log10 copies/ml reductions in CSF HIV-1 RNA, two in the absence of reductions in plasma HIV-1 RNA and two with undetectable plasma HIV-1 RNA at baseline. CONCLUSIONS: Substantial decreases in plasma and CSF HIV-1 RNA following addition of ABC were not precluded by baseline HIV-1 NRTI-associated mutations, including the M184V mutation, but non-responders commonly harbored multiple ZDV/d4T-associated mutations. HIV-1 RNA responses and RT genotype appear to be discordant between CSF and plasma in some subjects.

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Overexpression of nerve growth factor and basic fibroblast growth factor in AIDS dementia complex.

Although neurotrophic factors are currently considered as treatment for neurodegenerative diseases, little is still known about their presence in the central nervous system under pathological conditions. We investigated the expression of the neurotrophic molecules NGF, bFGF, BDNF and IGF-1 in brain tissue of patients suffering from AIDS dementia complex. In contrast to IGF-1 and BDNF, NGF and bFGF mRNA levels were significantly elevated. Strong NGF immunoreactivity was found in perivascular areas and was colocalized with infiltrating macrophages, whereas intense bFGF staining was found in cells with characteristic astrocytic morphology. These data suggest that the induction of NGF and bFGF alone appears to be insufficient as a compensatory mechanism to prevent ADC.

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Olfactory deficits in HIV-infected patients with and without AIDS dementia complex.

The aim of the present study was to examine the effect of HIV infection on odour memory. Recognition and identification olfactory tests were administered to six groups of patients defined according to a decrease in cellular immunity: asymptomatic HIV seropositive (HIV+), symptomatic HIV+, HIV+ AIDS, and three groups with a mild, moderate, and severe degree of dementia (AIDS dementia complex [ADC]). Consistent with the literature, the general results show that HIV infection is associated with a decrease in olfactory ability. In addition, a polynomial linear trend analysis indicates a constant decrease in performance from the first to the sixth group of patients, related to the number of CD4 T lymphocytes circulating and to the severity of the pathology. An interesting result regards the drop in performance exhibited by ADC patients on the identification task. Reasonably, such an effect is not attributable to a decline in olfactory ability only, bit rather to a severe semantic memory deficit. It follows that the two tasks used here can be useful clinical supports to discriminate between the mental operations involved in a low cognitive demand task (recognition) and in a high cognitive demand task (identification).

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Evaluation of autoantibodies to brain proteins in patients with AIDS dementia complex.

A high frequency of autoantibodies to brain proteins has been reported in HIV-1-positive patients. However, the specificity of this response has not been characterized. Using homogenized tissue from three normal brains, the presence of autoantibodies to human brain proteins was analyzed in 16 HIV-1-positive patients with AIDS dementia complex (ADC), 10 HIV-1-positive patients without ADC, 10 patients with multiple sclerosis, 10 patients with juvenile rheumatoid arthritis, and 10 normal controls. Although antibodies to various brain proteins were detected in sera from one-third HIV-1-infected individuals with or without ADC, the proteins recognized were different among different brains. Only one ADC patient had consistent seroreactivity to a 50-kDa brain-specific protein. Our results indicate that autoantibodies to brain proteins are infrequently present in patients with ADC.

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Reduced prevalence of the CCR5 delta32 heterozygous genotype in human immunodeficiency virus-infected individuals with AIDS dementia complex.

Heterozygosity for a 32-bp deletion in the CCR5 gene (CCR5 Delta32), which encodes the coreceptor for macrophage-tropic non-syncytium-inducing (NSI) human immunodeficiency virus type 1 (HIV-1) variants, results in a lower CCR5 expression and reduced NSI HIV-1 replication. Because infection of macrophages and microglial cells by NSI HIV-1 is considered to be instrumental for the development of AIDS dementia complex (ADC), we studied whether the CCR5 Delta32 heterozygous genotype correlated with a reduced frequency of ADC. Two (4.1%) of 49 patients with ADC versus 27 (14. 5%) of 186 AIDS patients without ADC were heterozygous for CCR5 Delta32 (P=.05). In contrast, a point mutation in the first transmembrane domain of CCR2 (CCR2 64I) did not show this protective effect (P=.57). The reduced prevalence of the CCR5 Delta32 allele among patients with ADC may indicate a reduced or absent reservoir of macrophage-tropic NSI HIV-1 in the brain of CCR5 Delta32 heterozygotes.

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Cerebrospinal fluid T cell receptor gamma/delta+ lymphocyte subsets in patient with AIDS-dementia complex.

A subset of peripheral T cells, whose physiological function is little known, expresses a distinct CD3-associated receptor composed of gamma and delta chains. We used two monoclonal antibodies to characterize the TcR gamma/delta lymphocytes (TcR delta 1+) and their fraction (TcS delta 1+) in peripheral blood and cerebrospinal fluid of patients affected by AIDS dementia complex (ADC). Thirty patients with ADC and a control group of twenty individuals with other non-inflammatory neurological diseases (OND) were recruited. Our results demonstrate that the TcR gamma/delta cells were also present in cerebrospinal fluid of ADC patients, but we did not find any statistical difference between the two groups.

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SDF-1alpha is expressed in astrocytes and neurons in the AIDS dementia complex: an in vivo and in vitro study.

Recent in vitro studies suggest that the alpha chemokine stromal-derived factor-1alpha (SDF-1alpha) and its receptor CXCR-4 may contribute to neuronal apoptosis in HIV infection of the brain. The cellular and regional expression of this chemokine and its relationship to the AIDS dementia complex (ADC), however, have remained undetermined. Using immunohistochemistry and semiquantitative RT-PCR, we examined the expression of SDF-1alpha in the frontal cortex (FC), the adjacent deep white matter (DWM). and the basal ganglia (BG) of 17 patients with ADC and 5 normal controls, and the FC and temporal cortex of 6 patients with Alzheimer disease (AD). Additionally, SDF-1alpha expression was studied in 3 different neuronal cultures: differentiated SK-N-MC cells, primary human fetal neuronal, and mouse hippocampal cultures. SDF-1alpha staining was predominantly localized to astrocytes in all 3 groups in the gray matter of the FC and the BG, often in the vicinity of cortical and basal ganglia neurons, but was generally absent in the DWM. Further, the number of positive neurons was significantly greater in the BG of AIDS subjects with advanced brain disease compared to subjects with lesser disease (p = 0.029). All cultures showed prominent SDF-1alpha staining of neurons within the cytoplasm and in neurites, whereas preferential expression in GABA-ergic neurons was found in hippocampal cultures. This is the first study to show that SDF-1alpha is constitutively expressed in astrocytes of the deep and cortical gray matter as well as in neurons of the human brain. Its increased expression in basal ganglia neurons of patients with advanced HIV CNS disease suggests it may also contribute to pathogenesis.

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A multi-center 1H MRS study of the AIDS dementia complex: validation and preliminary analysis.

PURPOSE: To demonstrate the technical feasibility and reliability of a multi-center study characterizing regional levels of the brain metabolite ratios choline (Cho)/creatine (Cr) and myoinositol (MI)/Cr, markers of glial cell activity, and N-acetyl aspartate (NAA)/Cr, a marker of mature neurons, in subjects with AIDS dementia complex (ADC). MATERIALS AND METHODS: Using an automated protocol (GE PROBE-P), short echo time spectra (TE = 35 msec) were obtained at eight sites from uniformly prepared phantoms and from three brain regions (frontal white matter, basal ganglia, and parietal cortex) of normal volunteers and ADC and HIV-negative subjects. RESULTS: A random-effects model of the phantom and volunteer data showed no significant inter-site differences. Feasibility of a multi-center study was further validated by detection of significant differences between the metabolite ratios of ADC subjects and HIV-negative controls. ADC subjects exhibited significantly higher Cho/Cr and MI/Cr in the basal ganglia and significantly reduced NAA/Cr and significantly higher MI/Cr in the frontal white matter. These results are consistent with the predominantly subcortical distribution of the pathologic abnormalities associated with ADC. CONCLUSION: This is the first study to ascertain and validate the reliability and reproducibility of a short echo time (1)H-MRS acquisition sequence from multiple brain regions in a multi-center setting. It should now be possible to examine the regional effects of HIV infection in the brain in a large number of subjects and to study the metabolic effects of new therapies for the treatment of ADC in a clinical trial setting.

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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.

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The relationship between AIDS dementia complex and the presence of macrophage tropic and non-syncytium inducing isolates of human immunodeficiency virus type 1 in the cerebrospinal fluid.

We sought to determine the clinical significance of macrophage tropic and non-syncytium inducing isolates of human immunodeficiency virus type 1 (HIV-1) in the cerebrospinal fluid (CSF) of patients with and without AIDS dementia complex (ADC). HIV-1 was isolated from the CSF of 31 patients with and without ADC. The isolates were then characterised as to the degree of macrophage tropism by quantitation of p24 production and the presence of syncytium inducing (SI) or non-syncytium inducing (NSI) isolates by MT2 assay and SupT1 coculture. The degree of macrophage tropism varied according to the donor macrophage that was used except in strongly macrophage tropic isolates. Moderate and severe ADC (stage > or = 2) was associated with the presence of highly macrophage tropic isolates in the CSF (P = 0.01). The sensitivity and specificity values of a highly macrophage tropic isolate in the CSF for ADC stage > or = 2 were 82% and 66% respectively while the predictive value was 64%. Three of four asymptomatic patients with such highly macrophage tropic isolates in the CSF subsequently developed ADC after an average of 4 months. Twenty-eight isolates from the CSF and 23 from the blood were NSI regardless of the presence or absence of ADC. The predictive value of an SI isolate in the blood reflecting an SI isolate in the CSF was 37.5% while the predictive value of an NSI isolate in the blood reflecting an NSI in the CSF was 100%. These data suggest that host factors are essential in determining the degree of macrophage tropism in HIV-1 and that such tropism is important for the presence and possibly subsequent development of ADC. The CSF usually has NSI isolates regardless of the presence of ADC and irrespective of the presence of such isolates in the blood thereby suggesting that the CSF is behaving virologically as a separate compartment to the blood.

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Metabolic characterization of AIDS dementia complex by spectroscopic imaging.

Prospective proton chemical shift imaging (CSI) of the brain was performed in 30 HIV- 1-seropositive patients and 11 healthy controls. Significant (P < 0.05) reductions in the N-acetyl-L-aspartate (NAA)/total creatine (Cr), and NAA/total choline (Cho) ratios and significant increases in Cho/Cr occurred in patients with 1) AIDS-defining diagnoses; 2) <200 CD4 lymphocyte counts/microl; 3) neurological evidence for an AIDS dementia complex (ADC); 4) magnetic resonance imaging (MRI) signs of cerebral atrophy. The basal ganglia and the insula were affected to approximately the same extent and without indications of spatial variations within these areas. Reduced NAA seems to indicate progressive neuronal injury or loss due to productive HIV infection in the brain and its clinical picture ADC. Spectroscopic abnormalities were, however, also observed in neurologically normal HIV patients or those with normal MRI results. Proton CSI may therefore serve as an early quantitative marker of central nervous system involvement in AIDS.

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Trypsin inhibition: a potential cause of cobalamin deficiency common to the pathogenesis of Alzheimer-type dementia and AIDS dementia complex?

There is increasing evidence for an association between Alzheimer-type dementia (AD) and nutritionally independent cobalamin deficiency. Furthermore, low serum cobalamin values occur in a kindred with familial Alzheimer's disease (FAD) and histopathological confirmation of AD neuropathology. The Cobalamin deficiency could be either a consequence or cause of amyloidogenesis. Cobalamin deficiency is also associated with the acquired immunodeficiency syndrome (AIDS). A common pathogenic mechanism may exist for AIDS dementia complex (ADC) and AD, but there is no explanation at present for these associations. This paper presents the hypothesis that protease inhibition is a common factor in AD and ADC resulting in protein-bound cobalamin malabsorption and disrupted cobalamin metabolism.

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Increased peroxynitrite activity in AIDS dementia complex: implications for the neuropathogenesis of HIV-1 infection.

Oxidative stress is suggested to be involved in several neurodegenerative diseases. One mechanism of oxidative damage is mediated by peroxynitrite, a neurotoxic reaction product of superoxide anion and nitric oxide. Expression of two cytokines and two key enzymes that are indicative of the presence of reactive oxygen intermediates and peroxynitrite was investigated in brain tissue of AIDS patients with and without AIDS dementia complex and HIV-seronegative controls. RNA expression of IL-1beta, IL-10, inducible nitric oxide synthase, and superoxide dismutase (SOD) was found to be significantly higher in demented compared with nondemented patients. Immunohistochemical analysis showed that SOD was expressed in CD68-positive microglial cells while inducible nitric oxide synthase was detected in glial fibrillary acidic protein (GFAP)-positive astrocytes and in equal amounts in microglial cells. Approximately 70% of the HIV p24-Ag-positive macrophages did express SOD, suggesting a direct HIV-induced intracellular event. HIV-1 infection of macrophages resulted in both increased superoxide anion production and elevated SOD mRNA levels, compared with uninfected macrophages. Finally, we show that nitrotyrosine, the footprint of peroxynitrite, was found more intense and frequent in brain sections of demented patients compared with nondemented patients. These results indicate that, as a result of simultaneous production of superoxide anion and nitric oxide, peroxynitrite may contribute to the neuropathogenesis of HIV-1 infection.

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An overview of AIDS dementia complex.

The major neurological complications associated with HIV infection include cognitive, behavioral, and motor disturbances, which may range in severity from subtle, mild cognitive deficits to the clinical syndrome referred to as HIV-associated dementia or AIDS dementia complex (ADC). As with Alzheimer's type dementia, caregivers for people with HIV/AIDS have the overwhelming and burdensome task of caring for someone with deteriorating cognitive abilities, increasing physical debilitation, and changes in personality. This article describes ADC as well as some of the similarities and differences from Alzheimer's type dementia, and offers some special considerations for older adults and HIV.

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Reversible myoclonic encephalopathy revealing the AIDS-dementia complex.

A 40-year-old HIV-positive right handed homosexual man was admitted for progressive mental deterioration coexisting with permanent segmental middle-amplitude arrhythmic, asynchronous and asymmetrical myoclonic jerks. EEG showed fronto-central bursts of rhythmic triphasic 1.5-2 Hz sharp waves similar to the characteristic periodic pattern of Jakob-Creutzfeldt disease. Biological procedures were negative, thus eliminating a metabolic encephalopathy. Dramatic neurological improvement occurred shortly after initiation of i.v. and then oral zidovudine which produced perfect EEG normalisation. This unusual electroclinical presentation of the AIDS-dementia complex underlines the fact that this affection may present a diagnostic challenge, particularly in individuals in whom HIV infection is unknown.

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Potential role of CCR5 polymorphism in the development of AIDS dementia complex.

The chemokine receptor CCR5 and to a lesser extent CCR2b and CCR3 have been shown to serve as coreceptors for HIV-1 entry into macrophages. Individuals that are homozygous for a defective CCR5 allele (DeltaCCR5) are highly, but not fully, resistant to infection with HIV-1. Here, we want to emphasize the importance of DeltaCCR5 in in vitro as well as in vivo studies. We provide data that suggest that CCR5 polymorphism may affect the onset of AIDS dementia complex in vivo and data that show that HIV-1 replication is influenced by the DeltaCCR5 allele in vitro. Knowing the CCR5 genotype of an individual will help to better interpret research results and may even provide new information about mechanisms of disease.

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The Edinburgh cohort of HIV-positive drug users: current intellectual function is impaired, but not due to early AIDS dementia complex.

Eighty people, all infected by HIV-contaminated drug injection equipment between 1983 and 1984, completed the National Adult Reading Test (NART) and selected revised Wechsler Adult Intelligence Scale (WAIS-R) subtests. Demographic variables (age, sex, years of education, and social class) were recorded as additional indices of premorbid functioning. Cross-sectional comparison of NART and WAIS-R scores showed that cognitive function was not more impaired with increasing severity of HIV illness, as defined by clinical staging. Nor were HIV-positive patients more impaired than a control group of seronegative drug users. Mean NART scores did not differ significantly from that predicted by a regression model, indicating that the NART can be reliably used to estimate premorbid intelligence for this population. However, current performance on WAIS-R subtests was below that expected from population models of cognitive function that combine measures of premorbid IQ and demographic factors, providing evidence of impaired intellectual function. Currently observed cognitive deficits are probably more due to drug use than to the insidious onset of AIDS dementia complex.

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