Tuft cell tropism enables norovirus evasion of CD8+ T cells and viral persistence

Abstract Human norovirus (HNV) is a leading cause of viral gastroenteritis. Infection fails to elicit durable immunity and can cause chronic asymptomatic shedding. It is not known how norovirus escapes the adaptive immune response, and rigorous studies of the host and viral determinants underlying immune evasion are impeded by the lack of scalable cell culture systems and reverse genetic tools. Murine norovirus (MNV) recapitulates many aspects of HNV and enables studying norovirus biology in vitro and in vivo. MNV CW3causes non-persistent infection with long-lasting immune memory, whereas MNV CR6causes persistent infection despite inducing functional MNV-specific CD8+ T cells. We recently identified that MNV CR6and other persistent MNV strains require tuft cells for chronic enteric infection. Tuft cells are rare, chemosensory epithelial cells with roles in pathogen surveillance, epithelial repair, and tumorigenesis. To interrogate tuft cell interactions with CD8+ T cells, we adoptively transferred JEDI (Just EGFP Death Inducing) CD8+ T cells that detect EGFP 200–208presented on H2-K dinto tuft cell reporter mice (Gfi1b-GFP). Surprisingly, tuft cells at steady state can resist JEDI CD8+ T cell-mediated killing despite normal levels of surface MHC-I. In contrast, Lgr5+ intestinal stem cells and extraintestinal tuft cells are highly susceptible to clearance by JEDI CD8+ T cells. We further find that JEDI CD8+ T cells cannot clear nor prevent MNV CR6infection of tuft cells, suggesting that tuft cells offer a replicative niche for immune escape and viral persistence. Whether HNV infects tuft cells during chronic asymptomatic infection and whether tuft cell-derived cancers can evade CD8+ T cells will warrant further exploration in the future. Supported by grants from the NIH (K08 A1128043, R01 AI148467) and the NSF (DGE1752134)