Microarray analysis of cytokine and chemokine genes in the brains of macaques with SHIV‐encephalitis

Abstract

Human immunodeficiency virus (HIV)-encephalitis results from a cascade of viral-host interactions that lead to cytokine and chemokine imbalance, which then leads to neuropathologic manifestations of the disease. These include macrophage/microglia activation, astrocytosis and neuronal dysfunction or death. As the molecular mechanisms of this process are poorly understood, we used Atlas human cytokine or cytokine receptor microarray analysis to highlight gene expression profiles that accompanied encephalitis in Simian human immunodeficiency virus (SHIV) 89.6P-infected macaques. Of the 277 genes screened, marked upregulation of monocyte chemoattractant protein-1, interferon-inducible peptide IP-10 and interleukin-4 were observed specifically in the encephalitic brains. These genes are collectively known to promote macrophage infiltration and activation and virus replication. In contrast, genes regulating neurotrophic functions, such as brain-derived neurotrophic factor were downregulated. We also found that some of the apoptosis genes were up- or down-regulated. These data provide a comprehensive spectrum of gene expression that underscores the two major clinical manifestations of this unique syndrome: enhanced virus replication in brain macrophages and dystrophic changes in neurons.

Neuronal Apoptosis Is Mediated by CXCL10 Overexpression in Simian Human Immunodeficiency Virus Encephalitis

“…21,33 Microarray analysis for cytokine and chemokine genes in the brains from the two groups of macaques demonstrated a marked up-regulation of CXCL10 RNA (almost a 20-fold increase) in the brains of macaques with SHIV-E compared to brains of infected macaques without encephalitis. 21 In assays described here, we used sections of encephalitic brain for immunohistochemical analyses to determine the expression pattern of CXCL10. As shown in Figure 1A, CXCL10 antigen was observed in large cells outside of and in close proximity to microglial nodules, but not in the macrophages populating the nodules.…”

“…All five had also developed virus infection in the brain but only three of these animals developed SHIV-E as demonstrated by histopathology of nine different regions of the brain. 21 Details of viral inoculation, disease course, processing of tissue samples, and histological analysis of the tissues have been described earlier. 21 Prominent neuropathological changes were present in basal ganglia, motor cortex, and brain stem regions in the encephalitic animals.…”

“…21 Briefly, paraffin sections of brain tissue were dewaxed, rehydrated in graded ethanol solutions, and then irradiated at 750 W in a microwave oven in 0.01 mol/L sodium citrate buffer, pH 6.0, for 1.5 minutes. After blockage with 1% of milk in phosphate-buffered saline, the sections were stained with primary/secondary antibodies.…”

“…20 In earlier studies aimed at exploring factors contributing to encephalitis caused by simian human immunodeficiency virus (SHIV) in the rhesus macaque model of HIV encephalopathy, we performed chemokine microarray analysis on the brains of infected macaques with and without SHIV-E. Among the various dysregulated genes identified on the array, a dramatic up-regulation (ϳ20-fold) of CXCL10 (formerly known as IP-10, interferon-␥-inducible protein) was observed in the brains of macaques with SHIV-E. 21 CXCL10 is a secreted polypeptide of 10 kd that was first identified as an early response gene induced after interferon-␥ treatment in a variety of cells, and was thus named interferon-inducible peptide, IP-10. 22,23 In addition to interferon-␥, HIV envelope glycoprotein gp120 has also been shown to induce expression of CXCL10 in brains of mice.…”

“…21,28,29 In the present study, we used the SHIV/rhesus macaque model of HIV-E to investigate whether there was a link between CXCL10 overexpression and neuronal degeneration. Using confocal microscopy on immunohistochemically stained sections of macaque brains with SHIV-E, we report localization of CXCL10 in neurons.…”