Abstract Vaccination is our most important preventative therapy against infectious disease. Protective immunity at mucosal sites has the potential to prevent re-infection by stopping invasion of the host. The small intestinal mucosa is amongst the most common sites of infection, but the mechanisms of vaccine-induced immune- mediated protection at this site remain relatively unknown. The primary target of an effective vaccine is the creation of long-lived B cells and T cells that provide durable protection. How CD4+ T cells might contribute to vaccine-mediated protection is unclear. We have developed a model of oral vaccination with an attenuated version of the E. coli heat labile toxin (LT) that induces large populations of vaccine-specific CD4+ T cells that are necessary for protection against re-infection. Using MHC class II tetramers we demonstrated that oral vaccination induces a long-lived population of LT-specific intestinal memory CD4+ T cells share a transcriptomic signature with Tissue-resident memory T cells (Trms). LT-specific T cells also expressed genes associated with enteric nerve function and after vaccination CD4+ T cells were observed adjacent to enteric nerves. Our hypothesis is that oral vaccine-specific CD4+ Trms protect the intestine by interacting with nerves to activate motility and physically expel enteric pathogens upon re-encountering their antigen. To test this question we need to develop a novel T cell receptor (TCR) transgenic mouse, specific to a dominant MHC class II-restricted antigen from LT. Via adoptive transfer of LT-specific TCR transgenic memory T cells we can test the hypothesis that these cells are sufficient to mediate protection against enteric infection. Further, LT- specific TCR transgenic T cells can be easily identified in tissues using congenic markers and we propose to use them to identify which nerves oral vaccine-activated CD4+ T cells interact with in the small intestine. At the conclusion of this grant we will have developed a first in its kind TCR transgenic mouse that will drastically increase our ability to make important discoveries about the biology and protective effects of CD4+ Trms in the small intestine, but also will undoubtedly be of use to the scientific community interested in oral vaccines.

Project Narrative Oral vaccines are potentially valuable tools to prevent infections. Here we propose to build a novel transgenic mouse model that will help us understand how T cells populate the intestine after vaccination to protect against infection.