Noroviruses are the leading cause of food-borne gastroenteritis outbreaks and childhood diarrhoea globally, estimated to be responsible for 200,000 deaths in children each year1,2,3,4. Thus, reducing norovirus-associated disease is a critical priority. Development of vaccines and therapeutics has been hindered by the limited understanding of basic norovirus pathogenesis and cell tropism. While macrophages, dendritic cells, B cells and stem-cell-derived enteroids can all support infection of certain noroviruses in vitro5,6,7, efforts to define in vivo norovirus cell tropism have generated conflicting results. Some studies detected infected intestinal immune cells8,9,10,11,12, other studies detected epithelial cells13, and still others detected immune and epithelial cells14,15,16. Major limitations of these studies are that they were performed on tissue sections from immunocompromised or germ-free hosts, chronically infected hosts where the timing of infection was unknown, or following non-biologically relevant inoculation routes. Here, we report that the dominant cellular targets of a murine norovirus inoculated orally into immunocompetent mice are macrophages, dendritic cells, B cells and T cells in the gut-associated lymphoid tissue. Importantly, we also demonstrate that a norovirus can infect T cells, a previously unrecognized target, in vitro. These findings represent the most extensive analyses to date of in vivo norovirus cell tropism in orally inoculated, immunocompetent hosts at the peak of acute infection and thus they significantly advance our basic understanding of norovirus pathogenesis.
The authors thank C. Jobin and X. Sun (University of Florida) for technical guidance in swiss rolling, H. Lelouard (Centre d’Immunologie de Marseille-Luminy) for discussions on Peyer’s patch cell types, J. Shirley (University of Florida) for technical guidance on multicolour flow cytometric analysis, and D.C. Machart and L. Schneider (University of Florida Molecular Pathology Core) for their assistance in processing histology samples. The authors also thank C. Fisher and T. Edwards (University of Florida) for their assistance with microscopic analyses, and D. Avram, D. Bloom, S. Tibbetts and F. Zhu for providing cell lines. This work was also supported by the technical guidance provided by ACDBio in terms of optimizing RNAscope assays. This work was funded by NIH R01AI116892 and NIH R01AI081921.