Impact of Priming on the Generation of Intestinal Tissue-Resident Memory T Cells

PROJECT SUMMARY/ABSTRACT There is a critical gap in our knowledge of the mechanisms during CD8 T cell priming that promote tissue-resident memory CD8 T (TRM) cell development. In the absence of such knowledge, the realization of developing vaccination strategies that elicit robust memory T cells at sites of pathogen invasion or tumor development remain unlikely. The long-term goal is to determine the mechanisms that regulate the induction and maintenance of TRM cells to improve vaccine efficacy. The overall objective in this application is to define how priming influences the in situ development of intestinal CD8 TRM cells. The central hypothesis is that direct retinoic acid signals during T cell priming in the gut draining lymph nodes license CD8 TRM cell development in the intestine. This hypothesis is based on rigorous preliminary data that suggests that retinoic acid licenses CD8 TRM precursor cell development independent of the well known CCR9-mediated gut migration pathway. The rationale that underlies the proposed research is that knowledge of the factors that promote CD8 TRM cell development will provide a strong scientific framework to develop more effective and targeted vaccination strategies. The central hypothesis will be tested by pursuing three specific aims: 1) To test the hypothesis that priming in mesenteric lymph nodes promotes intestinal CD103+ CD8 TRM cell differentiation; 2) To test the hypothesis that retinoic acid licenses intestinal CD103+ CD8 TRM cell development; and 3) To test the hypothesis that dietary vitamin A enhances CD103+ CD8 TRM cell development to improve vaccine efficacy. MLN or spleen derived cells will be used to assess CD103+ CD8 TRM cell development in the gut and in distal tissues after foodborne infection. Agonists and antagonists of retinoic acid receptors (RAR) in combination with RAR and CCR9 knockout mouse models will be used to determine how retinoic acid licenses intestinal CD8 TRM cell development. Finally, vitamin A deficient or supplemented diets will be used to modulate retinoic acid and assess vaccine immunogenicity and efficacy. The proposed research is innovative because it utilizes foodborne infection with a mouse adapted human pathogen, Listeria monocytogenes, to interrogate intestinal T cell responses. The proposed research is significant because it is expected to define novel pathways through which retinoic acid impacts intestinal CD8 TRM cell development independent of CCR9 and gut migration. Ultimately, such knowledge can be applied to improve rationale vaccine design targeting gastrointestinal pathogens or immunization in malnourished individuals with vitamin A deficiency.