Targeting mechanisms of T cell homeostasis to purge the HIV reservoir

University Of California, San Francisco, San Francisco CA

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Abstract

A major barrier to HIV eradication is the existence of a small pool of long-lived latently-infected, resting memory CD4[+] T cells carrying an integrated form of the viral genome. Memory T cells encompass a variety of cell subsets all endowed with specific survival and differentiation properties. We have recently demonstrated that the privileged cell type where HIV establishes its resen/oir is the central memory T cell (T{CM}) and its immediate progeny, the transitional memory T cell (T{TM})- IL-7 is one of the cytokines that is responsible for sustaining low levels of proliferation in T{CM} and T{TM}. Harnessing IL-7 interactions with its receptor on TCM could provide a strategy to prevent the survival and proliferation of these cells, and to prevent the persistence of the HIV reservoir. Another cytokine known to play a major role in memory T cell survival is IL-15. We have recently demonstrated that IL-15 engagement with its receptor on resting CD4[+] T{CM} that harbor latent virus will induce their differentiation into short-lived effector memory T cells (T{EM}) that can proliferate and produce virus. We propose to exploit this capacity of IL-15 so that the pool of resting, infected T{CM} cells can be depleted in vitro and in vivo. We will first determine the relative impact of IL-7 and IL-15 on HIV persistence in vivo and in vitro by measuring the contribution of these cytokines to the maintenance of the pool of latently infected cells in blood and tissues obtained from subjects receiving suppressive ART and by evaluating their capacity to induce viral reactivation (Specific Aim 1). We will then test the hypothesis that blocking the IL-7 pathway or, conversely, administrating IL-15 to optimally-treated macaquess could be used as strategies to deplete the latent viral reservoir (Specific Aim 2). Our proposed interventions target the major cellular source of persistent virus during treatment, and although they may not work alone in eradicating HIV, they could complement other interventions by transiently reversing the host factors that are critical in maintaining latently infected cells.