Genetic Variation of Porcine Epidemic Diarrhea Virus under Antibody Selective Pressure

Purpose To study the molecular variation of porcine epidemic diarrhea virus (PEDV) under antibody selective pressure.

Methods PEDV Sinder02 strain was continuously passaged for 40 generations on Vero E6 cells with and without the addition of appropriate antibodies, and the whole genome sequences of the virulent strains before and after passaging were amplified, sequenced, spliced, and analyzed.

Results In the 40th generation, the cumulative number of genome nucleotide mutation sites respectively was 71 and 50 for the group with antibody (group A) and the group without antibody (group NA), and the cumulative number of amino acid mutation sites respectively was 50 and 26 for the group A and the group NA. The ratio of nonsynonymous (NS) to synonymous (S) in S gene of the group A was 4.25, and the NS/S value in ORF3 gene was 3.67. In the group A, there were six stable mutation sites in S gene, four of which were associated with known epitopes; and there were five stable mutation sites in ORF3 gene, three of which were associated with known epitopes. The sequence homology between the original virus and both the group A and the group NA were decreased from generation to generation, and the differences between the group A and the original virus was greater, with a greater genetic distance.

Conclusion The first proof that antibody selective pressure plays a role in promoting variation of the S gene and ORF3 gene of PEDV Sinder02 strain. The results of the study provide a theoretical basis for exploring the variation of PEDV and also provide a scientific reference for the development of new PEDV vaccines.