Unique immune cells in oral cavity are critical for enteric virus pathogenesis

Abstract

Abstract We recently discovered that salivary glands are a major site of norovirus replication and oral-oral transmission is facilitated by saliva1. However, the cell types infected and the role of saliva in virus dissemination remains to be elucidated. Mice inoculated with norovirus were sampled and cells sorted into immune and epithelial cells. Mice became positive for virus in salivary glands and intestine plus associated lymphatic tissues. The majority of virus was present and replicating in CD45+ immune cells and EpCAM+ epithelial cells. Spatio-temporal analysis of the infection revealed that the earliest and highest viral pools were associated with the mandibular lymph nodes. Furthermore, a unique population of immune cells contained the highest concentration of virus, suggesting that these cells potentially play a sentinel role in disseminating norovirus. Notably, enteric infection of the intestine resulted in high levels of inflammation and cell death, however this was absent in the salivary glands, suggesting a level of immune modulation. Our findings suggest that the immune response in the salivary glands is different from that seen in the intestinal tract, and there is a unique population of immune cells which potentially plays an important role during the infection. 1 Ghosh S, et al. Enteric viruses replicate in salivary glands and infect through saliva. Nature. 2022; 607:345–350. doi: 10.1038/s41586-022-04895-8.