N-terminal Domain of the Spike Protein of Porcine Epidemic Diarrhea Virus as a New Candidate Molecule for a Mucosal Vaccine

Kim, Sae-Hae; Cho, Byeol-Hee; Lee, Kyung-Yeol; Jang, Yong-Suk

The gut mucosal immune system consists of immune-inductive site, such as Peyer's patches (PPs), where Ag-specific immune induction occurs, and immune-effector site, such as the lamina propria (LP), where Ag-specific IgA is produced (9) . PPs do not have afferent lymphatic vessels; therefore, the main gateway of Ags into PPs is via microfold (M) cells, specialized epithelial cells mainly found in the follicle-associated epithelium of PPs in the gut (10) . M cells are distinguished from enterocytes by their unique morphological features, such as a thin glycocalyx, short and irregular microvilli, and an internal pocket containing Ag-presenting cells (APCs) (11) . Luminal Ags transported across the interior of M cells interact with APCs, resulting in induction of Ag-specific IgA + B cells. Dimeric IgA secreted from plasma B cells of the LP plays a major role as a mucosal defender through immune exclusion, intracellular neutralization, and Ag excretion (12) . Consequently, it is required to induce pathogen-specific mucosal immunity to protect the host against pathogen infection in the mucosa.