Human immunodeficiency virus type 1 RNA Levels in different regions of human brain: Quantification using real-time reverse transcriptase–polymerase chain reaction

Abstract

Human immunodeficiency virus type 1 (HIV-1) enters the central nervous system shortly after the infection and becomes localized in different regions of the brain, leading to various neurological abnormalities including motor disorders and neurocognitive deficits. Although HIV-1-associated functional abnormalities of the central nervous system (CNS) can be evaluated during life by using various test batteries, HIV-1 virus concentration in different brain regions can be measured only after death. The tissues obtained at autopsy provide a valuable source for determining the role of various factors, including that of HIV-1 viral load in the CNS, that may contribute to the regional CNS neuropathogenesis. For this study, we obtained from the National Institutes of Health-sponsored National NeuroAIDS Tissue Consortium (NNTC) the tissues from different brain regions collected at autopsy of HIV-1-positive (N = 38) and HIV-negative (N = 11) individuals, with postmortem intervals of 2 to 29 h, and measured HIV-1 RNA concentration in the frontal cortex, frontal cortex area 4, frontal cortex area 6, basal ganglia, caudate nucleus, putamen, globus pallidus, substantia nigra, and cerebrospinal fluid. Because HIV-1+ individuals were infected with the virus for up to 21 years and the majority of them had used highly active antiretroviral therapy (HAART), we used highly sensitive real-time reverse transcriptase-polymerase chain reaction (RT-PCR) assay in order to detect a wide dynamic range of HIV-1 RNA with lower detection limit of a single copy. The primers and probes were from the long terminal repeat (LTR) region of HIV genome for achieving higher specificity and sensitivity of detection and amplification. Our results demonstrate a wide variation in the concentration of HIV-1 RNA in different brain regions (5.51 and 8,144,073; log(10) 0.74 and 6.91 copies/g tissue), and despite the high specificity and sensitivity of this method, viral RNA was not detected in 50% of all the samples, and in 30% to 64% of samples of each region of HIV-1+ individuals. However, the highest concentration of viral RNA was found in the caudate nucleus and the lowest concentration in the frontal cortex and cerebrospinal fluid. The viral RNA was undetectable in all samples of HIV-negative individuals.

Structural gray and white matter changes in patients with HIV

“…With regard to the caudate nucleus, neurocognitive impairment was correlated with volume reduction and reduced blood flow [35]. Furthermore, virus accumulation together with decreased dopamine levels is present within the caudate nucleus [36,37].…”

Human immunodeficiency virus infection in the CNS and decreased dopamine availability: relationship with neuropsychological performance

“…Findings from several studies suggest that in the absence of opportunistic infections, HIV-1-associated neuronal loss found in different brain regions is a consequence of neuronal damage caused by the virus-related neurotoxins (Nath 2002), as well as the neurotoxic products generated by the infected extra-neuronal cells, including microglia and macrophages, and to some extent by astrocytes (Heyes et al 1991;Brabers and Nottet 2006;Anderson et al 2002;Brack-Werner 1999;Kaul and Lipton 2006). Recent studies by our group reported varying levels of HIV-1 RNA in different regions of postmortem brains with high concentration found in different nuclei of the basal ganglia, including the caudate nucleus, putamen, globus pallidus, and substantia nigra as well as in the fronto-cortical areas (Kumar et al 2007). Since these subcortical regions are also rich in dopaminergic activity and neurotoxicity of the dopaminergic system has been associated with AIDS dementia (Nath et al 2000), we propose that high levels of HIV-1 RNA found in these brain regions may be responsible for inducing the higher production of neurotoxins that result in the loss of dopaminergic neurons and a decrease in the availability of dopamine, leading to impairment in neuromotor and neurocognitive functions in individuals with HIV-1 infection.…”

Drugs of Abuse, Dopamine, and HIV-Associated Neurocognitive Disorders/HIV-Associated Dementia

“…HIV-1 gp41-positive microglia were most numerous in globus pallidus obtained from the brain of AIDS encephalitis patients [27]. Relatively higher levels of HIV-1 RNA were found in dopamine-rich parts of human brain samples (substantia nigra, caudate nucleus, basal ganglia, and globus pallidus) obtained at autopsy [17,28]. Overall, these data suggest that while HIV infection can generally cause brain atrophy, "dopamine-rich" areas can show proportionally more atrophy, suggesting a propensity for HIV in targeting these brain areas.…”