Enhancing the virulence of G2a subtype PEDV by chimeric expression of G2c subtype S gene

Among the various causes of pig diarrhea, porcine epidemic diarrhea (PED) remains a severe disease causing significant economic losses to the global swine industry. Given the rapid variation of the PEDV spike (S) protein, it is crucial to investigate how S protein of different genotypes influence the pathogenicity and immunogenicity of PEDV. Herein, chimeric PEDV strains were constructed by inserting the S gene of subtype G1b, G2b, or G2c into the corresponding position of the G2a subtype strain GX4/2021 using Red recombination. In evaluating the growth characteristics of these chimeric viruses, the G1b subtype S protein was identified as a determinant of trypsin independence in the chimeric PEDV strains, while the S proteins of G2 genotype facilitated the formation of larger syncytia in recombinant PEDV-infected cells in the presence of trypsin. Furthermore, the effects of S proteins from different subtypes on the pathogenicity and immunogenicity of the recombinant viruses were examined using piglet challenge experiments. These findings indicate that the G2c subtype S protein induced the most severe diarrhea symptoms and a strong T cell response in piglets, highlighting the central significance of the G2c subtype S protein in PEDV virulence and immunogenicity. Overall, our findings reveal the role of different genotypes S proteins in the pathogenic mechanisms and immunogenicity of the emerging PEDV variants and provide a foundation for future vaccine design strategies.