The Role of the Immune Response in Controlling the Size of the HIV Reservoir.

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DESCRIPTION (provided by applicant): HIV-infected individuals accumulate a reservoir of treatment-resistant, latently infected resting CD4+ T cells. A special category of HIV infected individuals called elite suppressors have undetectable viral loads in the absence of highly active antiretroviral therapy (HAART) and have a smaller HIV reservoir. There is compelling evidence that elite suppressors (ES) have higher functioning CTL activity against HIV than treated and untreated chronic progressors. Our recent data provide evidence that CTL in ES have activity against latently infected resting CD4+ T cells in vivo. Specifically, we demonstrate for the first time that ES patients have dramatically lower levels of integrated HIV DNA and a relatively large excess of unintegrated HIV DNA compared to HAART patients. This is consistent with CTL pressure since HIV proteins are expressed more efficiently from integrated compared to unintegrated HIV DNA. In addition, we have preliminary data that latently infected resting CD4+ T cells express HIV proteins but do not permit spreading infection and thus should be susceptible to CTL pressure. At the same time, we show with our in vitro model of latency that CTL have activity against latently infected resting CD4+ T cells. Thus, the range of CTL targets is greater than previously thought since it appears that latently infected cells can be targets of CTL. In this application, we plan to test for further evidence of CTL pressure by assessing the frequency of HIV RNA+ cells among resting CD4+ T cells in ES vs HAART patients. We expect the frequency of HIV RNA+ cells normalized to integration to be lower in ES because we expect the majority of HIV RNA+ cells will express protein and be subjected to CTL lysis. Finally, we will determine if integration levels increase over time (as suggested by our preliminary data) in all or a subset of ES and if an increase in integration levels correlates with a loss of CTL function in ES. We also consider the alternate hypothesis that integration levels may increase over time in ES because defective proviruses accumulate. PUBLIC HEALTH RELEVANCE: A special category of HIV infected individuals, called elite suppressors, control HIV viral load to undetectable levels in the absence of antiviral therapy. The proposed experiments investigate the mechanism behind the ability of elite suppressors to maintain a smaller reservoir. Our studies suggest that elite suppressors have immune activity against treatment resistant reservoir cells and may lead to future therapies that harness the immune response to reduce reservoir size in patients receiving antiviral therapy.