Project 2 will determine the extent to which metabolic conditions and immunometabolic programming impact the ability to recruit new T-cell clonotypes with memory-like features. HIV-infected individuals harbor pre-existing HIV-specific T cells that were insufficiently potent to control initial infection and that will likely remain ineffective even after expansion in number following therapeutic vaccination. We propose that metabolic control over the response to vaccination can positively bias the response by limiting expansion of exhausted T cells and allowing expansion of long-lived memory cells that can control viral replication after treatment interruption. If so, then control over host and specifically T-cell metabolism may be required to design impactful therapeutic T-cell vaccines that transform the host immune response to HIV. We believe that fully understanding T-cell responses in human populations will require better understanding of how host metabolism controls T-cell differentiation. Furthermore, manipulation of metabolic pathways, especially amino-acid sensing pathways, may offer a mechanism for greater control over the quality of the T- cell response elicited by therapeutic vaccination. This project will use metabolic profiling via plasma metabolomics, RNAseq, and SCENITH to (i) understand the extent to which metabolic profiles are associated with success in completed therapeutic-vaccine trials, and (ii) test if metabolic regulation can alter the trajectory of T-cell development in response to therapeutic vaccines. We hypothesize that successful vaccines leverage immunometabolic programming to restrain pre-existing memory CD8+ T cells from expanding and promote outgrowth of broadly reactive new CD4+ and CD8+ clonotypes with stem-like qualities. Aim 1: Using samples from therapeutically vaccinated humans and non-human primates, identify metabolomic features that predict T-cell differentiation patterns, breadth, and/or control over viremia in ATI. In this aim, we test if rich metabolomic data (plasma analytes, bulk RNAseq, and SCENITH) from macaques and humans can predict both the quality of T-cell responses generated by therapeutic vaccination and the virus control achieved after ATI. Aim 2: Examine the systemic and T cell-specific metabolomic impact of SIV vaccines co-delivered with either supplemental arginine or the arginine-catabolizing enzyme, arginase 1, and the effect on viremia after ART cessation. mTOR regulates cellular metabolism based on integration of nutrient-sensing systems, including those that measure availability of amino acids. Vaccine-mediated modulation of amino-acid catabolism could therefore provide a route to local and limited metabolic regulation that encourages a transformative and effective T-cell response.