Enhancing mucosal immunity by transient microbiota depletion

Tissue resident memory CD8 + T cells (Trm) are poised for immediate reactivation at sites of pathogen entry and provide optimal protection of mucosal surfaces. The intestinal tract represents a portal of entry for many infectious agents; however, to date specific strategies to enhance Trm responses at this site are lacking. Here, we present TMDI (Transient Microbiota Depletion-boosted Immunization), an approach that leverages antibiotic treatment to temporarily restrain microbiota-mediated colonization resistance, and favor intestinal expansion to high densities of an orally-delivered Listeria monocytogenes strain carrying an antigen of choice. By augmenting the local chemotactic gradient as well as the antigenic load, this procedure generates a highly expanded pool of functional, antigen-specific intestinal Trm, ultimately enhancing protection against infectious re-challenge in mice. We propose that TMDI is a useful model to dissect the requirements for optimal Trm responses in the intestine, and also a potential platform to devise novel mucosal vaccination approaches. Tissue resident CD8 + T cells present at mucosal surfaces are poised to elicit function in situ, however approaches to boost their number in the gastrointestinal mucosa has been limited. Here the authors combine the use of Listeria monocytogenese and transient depletion of the intestinal microbiome to boost the resident CD8 + T cell response.