Genetic Evolution Analysis and Clinical Antibody Tracking Analysis of Two PEDV Strains in China

To investigate the current epidemic status of dominant Porcine Epidemic Diarrhea Virus (PEDV) strains and the genetic evolution characteristics of their S proteins in China, as well as to explore strategies for enabling suckling piglets in PED-affected farms to acquire effective maternal antibody protection, this study conducted S gene sequencing on PEDV isolates collected from two epidemic cases, followed by phylogenetic analysis and homology-based three-dimensional modeling. Meanwhile, the titers of IgA and IgG in the PEDV-specific immune response were tracked and analyzed by employing different immunization regimens. The results showed that phylogenetic analysis allowed the identification of distinct variations in the major antigenic epitope CO-26K equivalent (COE) region and the predicted N-glycosylation sites of the S protein. Additionally, the differences in the spatial conformation of the COE region might also account for the inadequate protection of pig herds against G2c strain infection conferred by commercial vaccines that do not contain the G2c strain. Furthermore, feedback immunization combined with inactivated tissue vaccine-based sow booster immunization during gestation could induce high levels of PEDV-specific IgA antibodies, and continuous gestation-stage booster immunization with inactivated tissue vaccines was crucial for maintaining such high antibody titers. Collectively, the findings of this study provide a reference for the establishment of high-level PED maternal antibody protection in pig herds.