DECREASED INTERFERON- GAMMA PRODUCTION IN THE CD4+ T-CELLS FROM AIDS PATIENTS PERSISTS DURING HAART THERAPY: ROLE OF ABERRANT METHYLATION

Abstract

Individuals infected with HIV progress to overt AIDS at markedly different rates. HIV infects primarily the CD4+ T-cell, which orchestrates the immune response mainly through the expression of cytokines. Our laboratory has been investigating the hypothesis that HIV infection disrupts the delicate balance of cytokines resulting in immune dysfunction. Previously, we have shown that in vitro infection of CD4+ T-cells with HIV results in aberrant methylation of the IFN- y gene promoter leading to a reduced expression of this cytokine in infected cells. In this study, we examined the potential of CD4+ T-cells isolated from HIV-infected individuals to express cytokines, including IFN-y. By combining intracellular staining techniques and flow cytometry with a two-step priming and activation of CD4+ T-cells, we determined the potential of a specific cell population to produce cytokines. Here, we show that CD4+ T-cells isolated from HIV-infected individuals showed a marked decrease in the potential to produce IFN-y. The decreased expression was not due to delayed kinetics of expression, differential activation, differential apoptosis or differences in memory vs. naive populations. The reduced ability to produce IFN-y persisted in individuals whose viral load had been reduced to undetectable levels through treatment with highly active anti-retroviral therapy (HAART). IFN-y production in these individuals can be partially restored with the addition of 5-Aza-2-deoxycytidine. Investigation of the molecular mechanisms by which IFN-y production is deregulated showed hypermethylation in the promoter of the gene. These data suggest aberrant methylation can play a role in cytokine dysregulation seen in AIDS.