Project description:The persistent murine norovirus strain MNVCR6 is a model for human norovirus and enteric viral persistence. MNVCR6 causes chronic infection by directly infecting tuft cells, rare chemosensory epithelial cells. Although MNVCR6 induces functional MNV-specific CD8+ T cells, these lymphocytes fail to clear infection. To clarify how tuft cells promote immune escape, we interrogated tuft cell interactions with CD8+ T cells by adoptively transferring JEDI (Just EGFP Death Inducing) CD8+ T cells into tuft cell reporter mice (Gfi1b-GFP). Surprisingly, some tuft cells partially resist JEDI CD8+ T cell-mediated killing – unlike Lgr5+ intestinal stem cells and extraintestinal tuft cells – despite seemingly normal antigen presentation. When targeting tuft cells, JEDI CD8+ T cells predominantly adopt a T resident memory phenotype with decreased effector and cytotoxic capacity, enabling tuft cell survival. Importantly, JEDI CD8+ T cells neither clear nor prevent MNVCR6 infection in the colon, the site of viral persistence, despite targeting a virus-independent antigen (e.g., GFP).
Project description:The persistent murine norovirus strain MNVCR6 is a model for human norovirus and enteric viral persistence. MNVCR6 causes chronic infection by directly infecting tuft cells, rare chemosensory epithelial cells. Although MNVCR6 induces functional MNV-specific CD8+ T cells, these lymphocytes fail to clear infection. To clarify how tuft cells promote immune escape, we interrogated tuft cell interactions with CD8+ T cells by adoptively transferring JEDI (Just EGFP Death Inducing) CD8+ T cells into tuft cell reporter mice (Gfi1b-GFP). Surprisingly, some tuft cells partially resist JEDI CD8+ T cell-mediated killing – unlike Lgr5+ intestinal stem cells and extraintestinal tuft cells – despite seemingly normal antigen presentation. When targeting tuft cells, JEDI CD8+ T cells predominantly adopt a T resident memory phenotype with decreased effector and cytotoxic capacity, enabling tuft cell survival. Importantly, JEDI CD8+ T cells neither clear nor prevent MNVCR6 infection in the colon, the site of viral persistence, despite targeting a virus-independent antigen (e.g., GFP).
Project description:Chemosensory epithelial tuft cells contribute to innate immunity at barrier surfaces, but their differentiation from epithelial progenitors is not well understood. Here we exploited differences between inbred mouse strains to identify an epithelium-intrinsic mechanism that regulates tuft cell differentiation and tunes innate type 2 immunity in the small intestine. Balb/cJ (Balb) mice had fewer intestinal tuft cells than C57BL/6J (B6) mice and failed to respond to the tuft cell ligand succinate. A majority of this differential succinate response was determined by a single genetic locus from 50-67Mb on chromosome 9 (Chr9). Congenic Balb mice carrying the B6 Chr9 locus had elevated baseline numbers of tuft cells and responded to succinate. The Chr9 locus includes Pou2af2, a transcriptional cofactor essential for tuft cell development. Epithelial crypts expressed a previously unannotated short isoform of Pou2af2 that uses a novel transcriptional start site and encodes a non-functional protein. Low tuft cell numbers and the resulting lack of succinate response in Balb mice was explained by a preferential expression of the short isoform. Physiologically, differential Pou2af2 isoform usage tuned innate type 2 immunity in the small intestine. Balb mice maintained responsiveness to helminth pathogens while ignoring commensal Tritrichomonas protists and reducing norovirus burdens.