Objectives: Influenza in humans is often accompanied by gastroenteritis-like symptoms such as diarrhea and abdominal pain nausea, but the underlying mechanism remains unclear.
Results: Mice infected with three subtypes of respiratory influenza A virus (IAV), particularly H5N1 and H7N2, developed intestinal injury. The avian H5N1 and H7N2 IAV were detected in the small intestine, whereas the human H1N1 was not detected. Section staining with the sialic acid (SA) receptor demonstrated that the small intestine mainly expressed SA α2, 3 Gal instead of SA α2, 6 Gal which preferentially binds to avian IAV. The number of goblet and sIgA cells in the small intestine increased, whereas CD4(+) and CD8(+) T cells decreased in all infected mice except for CD8(+) T cells increased in H7N2 infected mice.
Conclusions: Respiratory IAV infection, particularly infected by avian IAV, can cause small intestine structural damage and modify the local immune response, thereby resulting in gastroenteritis-like symptoms.