Isolation and assessment of characterization of porcine epidemic diarrhea virus GD1 strain from China

Porcine epidemic diarrhea virus (PEDV) is an important pathogen in swine, causing severe economic losses to the global swine industry. As a coronavirus, PEDV is prone to mutations and recombination. Therefore, characterizing circulating strains is essential for disease control. In this study, a PEDV strain (GD1) was isolated from diarrheic piglets in Guangdong Province, China, and identified by RT-PCR and immunofluorescence. Pathogenicity was evaluated in piglet challenge experiment. The results showed that GD1 strain could be stably passaged in Vero cells, forming syncytia. Phylogenetic analysis based on the complete genome and spike (S) gene both placed GD1 strain within the GIIc genotype. Amino acid sequence alignment of the S protein revealed multiple amino acid mutations in the neutralizing epitopes COE, SE16, and SS6 of GD1 strain compared with the classical vaccine strain CV777. Recombination analysis suggested that GD1 may be a novel recombination strain originating from strains SD2021 and GDS28, with the recombination breakpoint located in the ORF1a region. Pathogenicity assessment demonstrated that GD1 is highly virulent, inducing severe watery diarrhea and vomiting in newborn piglets within 24 h post-inoculation, and causing histopathological lesions characterized by intestinal villous atrophy and shedding. Immunohistochemistry confirmed that PEDV antigen was predominantly distributed in the villous epithelial cells of the small intestine. The successful isolation and characterization of the GD1 strain provide important viral resources for further research on the genetic evolution of PEDV and the development of matched vaccines.