Molecular epidemiological analysis of ORF3 genes of PEDV endemic strains in Henan province / 中国兽医学报

ABSTRACT

To understand the genetic origin and variation of porcine epidemic diarrhea virus (PEDV) prevailing in Henan province,a total of 22 PEDV positive samples from suckling piglets with severe diarrhea were collected from 16 pig farms and amplified by RT-PCR.ORF3 genes were then cloned into pMD18-T vector and sequenced.The result of sequencing showed that the length of ORF3 genes all were 675 bp which encoded 224 amino acids.The strains in this study had eight amino acid substitutions when compared with CV777 strain.The nucleotide homologies of the 22 strains were 95.9％-100％ and amino acid homologies were 96.4％-100％.By comparing with those of European strain CV777 and vaccine strain truncated CV777,the nucleotide homologies were 97.1％-97.9％ and 94.8％-95.4％,respectively.Based on the phylogenetic relationship of ORF3 genes,the PEDV field strains and PEDV reference strains could be divided into two groups,and all the field strains identified in this study belong to group 2.It suggested that prevalent PEDV strains in this study seem to be closely related to Henan isolates in previous years,domestic strains,Janpanese strains,American strains as well as Korean strains but differ genetically from European strains or vaccine strains used in China.This experiment analyzed the ORF3 gene sequence features in prevailing of Henan region in recent years,which provides a new support of epidemiology study and protein function research of PEDV ORF3 gene.