Investigating antigen-driven clonal proliferation to target HIV-1 persistence

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PROJECT SUMMARY Antiretroviral therapy (ART) greatly reduces HIV morbidity and mortality. However, it has no effect on the HIV reservoir, a small pool of latently infected cells that rekindles infection upon treatment interruption. Due to the persistence of this reservoir, ART must be continued indefinitely, requiring public health systems to deliver medications to all 38 million people living with HIV for life. This research program has the long-term goal of helping develop new therapeutic approaches to eliminate or control the HIV reservoir, leading to a drug-free remission. The proliferation of infected cells is a major mechanism of HIV persistence, as it results in expanded CD4+ T cell clones that carry proviral DNA. Recent studies suggest that antigen-specific immune responses contribute largely to this phenomenon. The overall objective of this application is to understand the role of chronic antigens in determining the structure and dynamics of the clones that constitute the HIV reservoir. The underlying central hypothesis is that adaptive immune responses impose selective pressure on HIV-infected cells. The rationale for the project is that, if clonal expansion is one of the major mechanisms of HIV persistence, targeting this process will reduce the reservoir size and accelerate its decay. The central hypothesis will be tested by pursuing three specific aims: 1) Determine the effect of antigens on HIV latency reversal; 2) Identify the factors responsible for the expansion and maintenance of HIV-infected, antigen-specific clones; and 3) Determine the role of chronic antigens from commensal pathogens in driving reservoir persistence. Under the first aim, CD4+ T cells reactive to Cytomegalovirus (CMV, the virus responsible for a common chronic infection) will be isolated from individuals with HIV and expanded ex vivo. Upon stimulation of T cells with cognate CMV antigens, HIV latency will be studied at the single-cell level and compared to non-specific maximal T cell stimulation, commonly used to reverse latency in vitro. For the second aim, CMV-responsive clones harboring HIV will be tracked longitudinally in individuals with CMV replication around the time of ART introduction, in the effort to understand the events underlying their expansion. For the third aim, Candida albicans, a pathogenic commensal yeast that plays a major role in driving antifungal immune responses, will be used to demonstrate whether chronic exposure to commensal microbes shapes the repertoire of CD4+ T cells, including those part of the HIV reservoir. The research proposed in this application is innovative because, compared to the status quo, it focuses on physiological T cell stimulation and ubiquitous immune responses to study latency reversal and HIV dynamics. The proposed research is significant because it is expected to result in a better understanding of the interaction between adaptive immunity and HIV persistence, and will provide new insight on how to target a major mechanism of HIV reservoir maintenance. Ultimately, such knowledge has the potential of offering new opportunities for the development of innovative strategies to induce HIV remission.