Surface displayed porcine epidemic diarrhea virus membrane epitopes on Lactiplantibacillus plantarum stimulates antibody production in mice

Porcine epidemic diarrhea virus (PEDV) causes enteric disease in pigs, characterized by vomiting and watery diarrhea, and has a major economic burden on the global pork industry. The objective of this study was to develop a new surface display system for PEDV antigens fused with a cell wall-anchoring domain, using <i>Lactiplantibacillus plantarum</i> as a host. The B-cell epitopes of the PEDV membrane (M) protein epitopes, designated as M1, M2, and M3, generated by online prediction tools, were stably expressed and displayed in <i>Lp. plantarum</i> SK156 and verified by immunofluorescence microscopy. Stimulation of porcine intestinal epithelial cells (IPEC-J2) with the surface displayed M epitopes resulted in elevated production of interferon (IFN)-γ and interleukin (IL)-10. To investigate the immunogenicity of the M epitopes, 30 female BALB/c mice (n = 6 per group) were orally administered <i>Lp. plantarum</i> displaying M1, M2, or M3 epitopes and wild-type <i>Lp. plantarum</i>, or phosphate buffered saline (PBS). On days 21 and 35, mice immunized with the M1 epitope showed consistently high levels of antigen-specific secretory immunoglobulin (Ig)-A and serum IgG, demonstrating the induction of both mucosal and humoral immune responses. However, no changes were observed in the cytokine profiles of the immunized mice. To the best of our knowledge, this is the first report of PEDV M epitopes on the surface of lactic acid bacteria (LAB). Our findings highlight the immunogenic potential of the PEDV M protein and the possibility of further research on the development of a <i>Lactobacillus</i>-based oral vaccine against PEDV infection.