PROJECT SUMMARY Group 1 CD1-restricted T cells are members of the unconventional T cell family that recognize self- and microbial lipid antigens presented by CD1a, CD1b, and CD1c molecules. Group 1 CD1-restricted T cells have been implicated to play critical roles in various autoimmune and infectious diseases, in particular Mycobacterium tuberculosis (Mtb) infection. While group 1 CD1-restricted T cells represent a substantial part of the T cell repertoire in humans, further understanding of their in vivo function and regulation in immune response has been stymied by the lack of group 1 CD1 expression in mice. We have previously generated a transgenic mouse model possessing the entire human group 1 CD1 locus (hCD1Tg) and TCR transgenic mouse models with Mtb lipid and self-lipid specificity. We demonstrated that both mycolic acid (MA)-specific and self-lipid-specific CD1b-restricted T cells confers protection against Mtb infection. In addition, chronic activation of CD1b autoreactive T cells can lead to the development of psoriasis-like skin inflammation in an ApoE-deficient mouse model of hyperlipidemia. As hyperlipidemia is a common condition in HIV-infected individuals and the general population, we aim to further understand how it may affect the function of group 1 CD1-restricted T cells during infection using Mtb infection as a model. In Aim 1, TCR transgenic mouse models in hCD1Tg/LDLR-/- background will be used to determine the impact of diet- induced hyperlipidemia on self- and microbial lipid-specific T cells and elucidate the molecular and cellular mechanisms mediate such effect. The impact of hyperlipidemia on the polyclonal group 1 CD1-restricted T cell responses to Mtb infection will also be determined by comparing bacterial burden, lung inflammation, and magnitude of autoreactive and Mtb lipid-specific T cell responses in Mtb-infected hCD1Tg/LDLR-/- mice with or without hyperlipidemia. While peptide-specific T cells are known to have distinct effector and memory phenotypes, the properties of memory group 1 CD1-restricted T cells remain elusive. In Aim 2, we will determine functional properties and protective mechanism of memory MA/CD1b-specific T cells generated in mice vaccinated with MA containing nanoparticle (MA-NP). To identify common features associated with Mtb-lipid specific memory T cells, we will compare memory MA/CD1b-specific T cells to glucose monomycolate/CD1b-specific T cells, isolated from a novel TCR transgenic mouse model expressing a conserved germline-encoded mycolyl lipid-reactive (GEM) TCR. Lasty, the transcriptional and functional properties of memory MA/CD1b-specific T cells elicited by two vaccination approaches, MA-NP and an attenuated Mtb strain, will be compared and their response to subsequent challenge with Mtb will be evaluated. Collectively, these studies will pave way to better understanding of the role of lipid-specific T cells in various infectious disease in a relevant comorbidity condition.