Oral Immunization against PEDV with Recombinant Lactobacillus casei Expressing Dendritic Cell-Targeting Peptide Fusing COE Protein of PEDV in Piglets

Abstract

Porcine epidemic diarrhea (PED) is a highly contagious disease in newborn piglets. In our previous study, a genetically engineered <i>Lactobacillus casei</i> oral vaccine (<i>pPG-COE-DCpep/L393</i>) expressing a dendritic cell (DC)-targeting peptide fused with porcine epidemic diarrhea virus (PEDV) COE antigen was developed. This vaccine induced significant levels of anti-PEDV specific IgG and IgA antibody responses in mice, indicating a potential strategy against PEDV infection. In this study, <i>pPG-COE-DCpep/L393</i> was used for oral vaccination of newborn piglets against PEDV. We then assessed the immune responses and protection efficacy of <i>pPG-COE-DCpep/L393</i>. An indirect enzyme-linked immunosorbent assay (ELISA) showed that the recombinant <i>Lactobacillus</i> vaccine elicits a specific systemic and mucosal immune response. The T-helper cells mediated by <i>pPG-COE-DCpep/L393</i> and PEDV infection display a Th1 phenotype. The histopathological results showed that <i>pPG-COE-DCpep/L393</i> promotes lymphocyte proliferation and effectively protects piglets against PEDV infection. The transforming growth factor-β level indicated that the recombinant <i>Lactobacillus</i> vaccine plays a role in anti-inflammatory responses in mesenteric lymph nodes during PEDV infection. These results show that <i>pPG-COE-DCpep/L393</i> is a potential vaccine against PEDV infection.