Neurosteroid-Mediated Regulation of Brain Innate Immunity in HIV/Aids: DHEA-S Suppresses Neurovirulence

Neurosteroids are cholesterol-derived molecules synthesized within the brain, which exert trophic and protective actions. Infection by human and feline immunodeficiency viruses (HIV and FIV, respectively) causes neuroinflammation and neurodegeneration, leading to neurological deficits. Secretion of neuroinflammatory host and viral factors by glia and infiltrating leukocytes mediates the principal neuropathogenic mechanisms during, although the effect of neurosteroids on these processes is unknown. We investigated the interactions between neurosteroid mediated effects and lentivirus infection outcomes. Analyses of HIV-infected uninfected human brains disclosed a reduction in neurosteroid synthesis enzyme expression. Human neurons exposed to supernatants from HIV macrophages exhibited suppressed enzyme expression without reduced cellular viability. HIV human macrophages treated with sulfated dehydroepiandrosterone (DHEA-S) showed suppression of inflammatory gene (IL-1, IL-6, TNF-) expression. IV-infected IV) animals treated daily with 15mg/kg body weight. DHEA-S treatment reduced inflammatory gene transcripts (IL-1, TNF-, CD3, GFAP) in brain compared to vehicle-(-cyclodextrin)-treated FIV animals similar to levels found in vehicle treated FIV animals. DHEA-S treatment also increased CD4T-cell levels and prevented neurobehavioral deficits and neuronal loss among FIV animals, compared to vehicle-treated FIV animals. Reduced neuronal neuro-steroid synthesis was evident in lentivirus infections, but treatment with DHEA-S limited neuroinflammation and prevented neurobehavioral deficits. Neurosteroid-derived therapies could be effective in the treatment of virus- or inflammation-mediated neurodegeneration

Hepatitis C Virus Core Protein Induces Neuroimmune Activation and Potentiates Human Immunodeficiency Virus-1 Neurotoxicity

BACKGROUND: Hepatitis C virus (HCV) genomes and proteins are present in human brain tissues although the impact of HIV/HCV co-infection on neuropathogenesis remains unclear. Herein, we investigate HCV infectivity and effects on neuronal survival and neuroinflammation in conjunction with HIV infection. METHODOLOGY: Human microglia, astrocyte and neuron cultures were infected with cell culture-derived HCV or exposed to HCV core protein with or without HIV-1 infection or HIV-1 Viral Protein R (Vpr) exposure. Host immune gene expression and cell viability were measured. Patch-clamp studies of human neurons were performed in the presence or absence of HCV core protein. Neurobehavioral performance and neuropathology were examined in HIV-1 Vpr-transgenic mice in which stereotaxic intrastriatal implants of HCV core protein were performed. PRINCIPAL FINDINGS: HCV-encoded RNA as well as HCV core and non-structural 3 (NS3) proteins were detectable in human microglia and astrocytes infected with HCV. HCV core protein exposure induced expression of pro-inflammatory cytokines including interleukin-1β, interleukin-6 and tumor necrosis factor-α in microglia (p<0.05) but not in astrocytes while increased chemokine (e.g. CXCL10 and interleukin-8) expression was observed in both microglia and astrocytes (p<0.05). HCV core protein modulated neuronal membrane currents and reduced both β-III-tubulin and lipidated LC3-II expression (p<0.05). Neurons exposed to supernatants from HCV core-activated microglia exhibited reduced β-III-tubulin expression (p<0.05). HCV core protein neurotoxicity and interleukin-6 induction were potentiated by HIV-1 Vpr protein (p<0.05). HIV-1 Vpr transgenic mice implanted with HCV core protein showed gliosis, reduced neuronal counts together with diminished LC3 immunoreactivity. HCV core-implanted animals displayed neurobehavioral deficits at days 7 and 14 post-implantation (p<0.05). CONCLUSIONS: HCV core protein exposure caused neuronal injury through suppression of neuronal autophagy in addition to neuroimmune activation. The additive neurotoxic effects of HCV- and HIV-encoded proteins highlight extrahepatic mechanisms by which HCV infection worsens the disease course of HIV infection

Impaired neurosteroid synthesis in multiple sclerosis

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Brain microbial populations in HIV/AIDS: α-proteobacteria predominate independent of host immune status.

The brain is assumed to be a sterile organ in the absence of disease although the impact of immune disruption is uncertain in terms of brain microbial diversity or quantity. To investigate microbial diversity and quantity in the brain, the profile of infectious agents was examined in pathologically normal and abnormal brains from persons with HIV/AIDS [HIV] (n = 12), other disease controls [ODC] (n = 14) and in cerebral surgical resections for epilepsy [SURG] (n = 6). Deep sequencing of cerebral white matter-derived RNA from the HIV (n = 4) and ODC (n = 4) patients and SURG (n = 2) groups revealed bacterially-encoded 16 s RNA sequences in all brain specimens with α-proteobacteria representing over 70% of bacterial sequences while the other 30% of bacterial classes varied widely. Bacterial rRNA was detected in white matter glial cells by in situ hybridization and peptidoglycan immunoreactivity was also localized principally in glia in human brains. Analyses of amplified bacterial 16 s rRNA sequences disclosed that Proteobacteria was the principal bacterial phylum in all human brain samples with similar bacterial rRNA quantities in HIV and ODC groups despite increased host neuroimmune responses in the HIV group. Exogenous viruses including bacteriophage and human herpes viruses-4, -5 and -6 were detected variably in autopsied brains from both clinical groups. Brains from SIV- and SHIV-infected macaques displayed a profile of bacterial phyla also dominated by Proteobacteria but bacterial sequences were not detected in experimentally FIV-infected cat or RAG1⁻/⁻ mouse brains. Intracerebral implantation of human brain homogenates into RAG1⁻/⁻ mice revealed a preponderance of α-proteobacteria 16 s RNA sequences in the brains of recipient mice at 7 weeks post-implantation, which was abrogated by prior heat-treatment of the brain homogenate. Thus, α-proteobacteria represented the major bacterial component of the primate brain's microbiome regardless of underlying immune status, which could be transferred into naïve hosts leading to microbial persistence in the brain

Transmission of bacteria from human brain to <i>RAG1^−/−</i> mice brains.

<p>(A) Comparison of the relative quantity of 16 s rRNA in human and matched recipient mouse brains showed that mean bacterial rRNA levels in recipient mice were present at ∼40% of the mean ODC14 brain homogenate rRNA levels but less than 1% for the heated-treated ODC13 brain homogenate (prior to heat-treatment), measured by real time RT-PCR. (B) Mouse host inflammatory gene transcripts (<i>ifn-α, il-1β</i> and <i>il-12</i>) in mouse brains were not induced by implantation of untreated compared to heat-treated human brain homogenates. (C) The bacterial 16 s rRNA sequences from the ODC14 brain homogenates and the recipient mouse ODC14 brains were similar with substantial phylogenetic overlap between the bacterial genera, as evidenced by the 97% similarity for <i>Delftia acidovorans</i> sequences.</p

Total sequence tag counts per patient for principal bacterial classes detected in brain¹.

1<p>All sequence tag counts were normalized across experiments.</p>2<p>Host gene.</p

16 s rRNA sequences from brain-derived cDNA of cynomolgus macaques.

<p> (A) Ethidium bromide-stained agarose gel showed the amplicon generated by primers 16 s514F and 16 s 806R from SIV-infected macaques 1–10, SHIV-infected macaques 1–3 and FIV-challenged macaque 1 and 2. cDNA synthesized with ultrapure water, water carried through both rounds of nested PCR and water used as template only in the final round of PCR were all included as negative controls. (B) Phylogenetic analysis of 16 s rRNA region sequences amplified by the primers 514F and 806R derived from macaque brain specimens. Clustal alignments were generated comparing amplicon sequences with the equivalent position of published 16 s rRNA sequences identified by BLAST analysis. The Neighbor joining tree was generated based on 10,000 bootstrap trials and rooted on the macaque mitochondrial 12 s rRNA sequence. Again, these data showed a predominance of Proteobacteria in brain-derived 16 s rRNA clones although other bacteria, e.g., Actinobacter and Bacilli, were detected.</p

Human brain host gene responses.

<p>Analysis of human transcript sequences implicated in (A) bacterial and (B) viral host responses identified by deep sequencing of brain-derived RNA showed variability within clinical groups with many genes showing a relative reduction or induction in expression in the HIV relative to ODC brain specimens. (C) Host neuroimmune responses were assessed as transcript abundance in terms of relative fold change (RFC) by real time RT-PCR, showing a general increase in pro-inflammatory gene expression among the HIV (n = 5) compared to ODC (n = 5) brain specimens with significant changes in <i>cd3ε, IL-12</i> and <i>egf</i> expression.</p