PROJECT SUMMARY/ABSTRACT HIV is a chronic infection requiring long-term antiretroviral therapy (ART) to halt viral replication and prevent disease progression. Despite highly effective ART, issues remain with medication access, adherence, and tolerability. When ART is stopped, the virus rebounds from a reservoir of long-lived infected cells with resumption of disease progression. Exceptions to this natural disease course are “Elite Controllers” who spontaneously suppress viral replication by highly functional HIV-specific T-cells. To achieve the robust immune responses observed in Elite Controllers, we have generated HIV-targeting chimeric antigen receptor (CD4CAR) T cells that redirect the specificity of T cells to recognize highly conserved regions of HIV. Using our validated non-human primate (NHP) model of chronic HIV infection, we have shown that CD4CAR T cells induce long- term viral remission following ART interruption in a subset of NHPs. Our data suggest that long-term CD4CAR T-cell responses will be essential to advance this therapy broadly for people living with HIV (PLWH). We are currently investigating strategies to extend CD4CAR T-cell persistence in vivo. Unlike in cancer, CAR T cells for HIV must overcome abundant soluble antigen in the form of circulating virus. Our preliminary data highlight how soluble antigen can inhibit CD4CAR T-cell killing of target cells and promote a dysfunctional immunophenotype. We hypothesize that soluble antigen must be overcome to achieve comparable success as observed for cancer. In this proposal, we will thoroughly characterize and overcome the effect of soluble antigen on CD4CAR T-cell function using our new ex vivo models of viremia to validate next-generation CD4CAR constructs. We will also extend the persistence of CD4CAR T cells using the immunostimulatory IL15 cytokine, which can boost HIV-specific endogenous T-cell and cancer-specific CAR T-cell responses. Our preliminary data confirm the potential for IL15 to enhance the cytotoxicity and survival of CD4CAR T cells. In this proposal, we will compare a series of IL15-armored CD4CAR T-cell strategies to enhance long-term persistence and durable cytotoxicity. Finally, we will combine our strategies to generate potent armored CD4CAR T cells with improved function and persistence during viremia, which we will validate and test in our NHP model of chronic HIV infection. Through the mentored research experiences outlined in this K08 proposal, Dr. Bui will develop expertise in gene therapy and adoptive cellular therapies for the treatment of HIV, which is aligned with his future career goal to become an independent physician-scientist advancing immunotherapies for infectious diseases. The hosting institutions have vibrant scientific communities in adoptive cellular therapies and infectious diseases that Dr. Bui will engage in to foster learning and build collaborations. Dr. Bui will receive comprehensive training in technical skills, scientific i...