Genetic Variation and Pathogenic Distinctions of Porcine Epidemic Diarrhea Virus GII a and GII c subtype

Porcine epidemic diarrhea virus (PEDV) is responsible for causing severe watery diarrhea, vomiting, and elevated mortality rates in neonatal piglets, resulting in substantial economic losses within the global swine industry. In recent years, PEDV has experienced continuous genetic variation, leading to the emergence of multiple subtypes with ambiguous pathogenic distinctions, thereby complicating clinical prevention and control efforts. To elucidate the molecular characteristics and pathogenicity of circulating PEDV strains, our study collected intestinal and fecal samples from diarrheic piglets on pig farms in China. Viruses were isolated using Vero-E6 cells and identified through transmission electron microscopy (TEM) and immunofluorescence assay (IFA). Whole-genome sequencing and evolutionary analysis revealed that the two isolated strains belonged to the GII a and GII c subtypes, designated as CH/GZ/2024 and CH/SX/2025, respectively. Pathogenicity assays in suckling piglets demonstrated that both strains induced typical PED symptoms; however, the CH/GZ/2024 strain exhibited enhanced pathogenicity, characterized by an earlier onset of diarrhea, higher mortality rates, and more severe intestinal lesions compared to the CH/SX/2025 strain. Conversely, the CH/SX/2025 strain displayed increased tissue tropismand induced a robust interferon immune response, which we speculated may be associated with the glycosylation site mutation in the S1 protein of the CH/SX/2025 strain. In conclusion, two different PEDV subtypes were successfully isolated from diseased newborn piglets, and their pathogenic differences were clarified. This study provides experimental basis for molecular epidemiological monitoring of PEDV and the optimization of prevention and control strategies.