2024-2025年天津市GⅡc亚型猪流行性腹泻病毒S基因遗传变异分析OA

In order to investigate the genetic variation characteristics of porcine epidemic diarrhea virus(PEDV)in Tianjin City since 2024,127 clinical samples collected from 27 small-to-medium swine farms across 5 districts/counties of Tianjin City were tested using RT-qPCR,from which representative positive samples were selected for S gene amplification,sequencing and phylogenetic analysis.The results showed 46/127 positive samples were detected.18 full-length S gene sequences were successfully obtained from 18 representative positive samples.Phylogenetic analysis indicated that all the 18 sequences belonged to GⅡc subtype,92.2％-93.5％identical to CV777,the classical vaccine strain.Amino acid sequence analysis revealed that typical molecular features of GⅡ-type variants appeared at positions 55-56 aa(IGEN insertion),135-136 aa(D/N insertion)and 155-156 aa(DI deletion)in all the sequences.Compared to AJ1102,the GⅡb vaccine strain,the mutation rate of amino acid in the S1 region was up to 50.0％-73.5％,with key mutation sites located in critical antigenic domains such as N-terminal domain(NTD)and coronavirus epitope(COE).N-glycosylation analysis revealed that the glycosylation patterns of positive sequences were highly consistent with those of highly pathogenic GⅡ strains,particularly in the 57ENQGVNST64 and 722NSTF725 regions.In conclusion,GⅡc subtype PEDV had been dominant in Tianjin City,and changes of virus antigenicity and enhanced capabilities of immune escape could be caused by the continuous mutations of its S gene.Key evidences were provided by the study for development of PED vaccines and formulation of control strategies.