Purging the latent HIV reservoir at ART inititation: A new eradication strategy

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 DESCRIPTION: It is now clear that antiretroviral therapy (ART) alone does not eradicate HIV: Even after more than 15 years of intensive and continuous therapy, the spread of the virus resumes within a few weeks upon cessation of ART in all but exceptional cases. A small pool of latently infected cells, usually referred as the "reservoir" of HIV infection, provides a long-live source of rebound viremia. Inducing HIV expression combined with ART has been proposed as a strategy to eliminate persistently infected cells that could ultimately lead to viral eradication However, none of the current approaches has led to a significant decrease in the size of the latent reservoir. A likely explanation for these disappointing results is given by the lack of potet HIV specific CD8 T cells to eliminate the recently reactivated latently infected CD4 T cells in virally suppressed subjects. Indeed, concomitant to the decrease in viral antigen load, HIV-specific CD8 T cells rapidly vanish after ART initiation and remain barely detectable during suppressive therapy. Therefore, shock and kill strategies implemented in individuals on long-term ART are likely to fail. A fundamentally different approach is to reactivate the pre-existing latent reservoir when ART is started while HIV-specific CD8 T cells are still at high frequencies. We hypothesize that there is a window of opportunity during ART initiation where the use of a reactivating agent would reactivate latently-infected CD4 T cells (shock) and lead to an enhanced killing of the HIV reservoir by HIV-specific CD8 T cells (kill), as these cells are still present at high frequency at this stage. The major objective of this proposal is to provide a proof of concept in the SIV model that the addition of a reactivating agent administered at ART initiation will lead to a significant decrease in the size of the latent viral reservoir due to potnt killing by CD8 T cells. To achieve this objective, we will use bryostatin-1 (BRYO-1) as a benchmark reactivating agent since we have observed that this PKC agonist is the most potent molecule to reactivate latent HIV in human CD4 T cells from virally suppressed individuals. In the R21 phase, we will validate that BRYO-1 can be used as benchmark reactivating agent in the SIV model and determine the optimal dose to be used in vivo. During the R33 phase, we will test this new concept in the non-human primate (NHP) model of HIV, SIV infection of Indian origin rhesus macaques specifically selected for expressing the MHC class 1 allele Mamu-A*01, that has been associated with potent SIV-specific CD8 T cell responses. We will compare the size of the latent reservoir in animals that will receive ART alone, ART + delayed BRYO-1 and ART + immediate BRYO-1 and demonstrate that the elimination of latent reservoir in animals receiving BRYO- 1 at ART initiation is mediated by CD8 T cell killing. In addition, we will interrupt ART in these animals to determine the potential clinical benefit of this novel strategy aimed at achieving a functional cure. This study will pave the way to the rapid development of clinical trials in which an eradication agent will be administered together with ART.