Fig. 5.

Potential sites for induction of immune response induced by oral-delivered viral vector vaccine. In the oral cavity, viral vector vaccines enter through oral lymphoid tissue, including adenoid, tubal tonsil, palatine tonsil, and lingual tonsil, etc. In the small intestine, Peyer’s patch is the core site for immune response (1) T cells enter Peyer’s patch from blood vessels. (2) M cells take up antigens by endocytosis and phagocytosis. (3) Antigens are transported across the M cell in vessels and released at the basal surface. (4) T cells in the Peyer’s patch encounter antigens and are activated by dendritic cells. (Created in BioRender)