Molecular evolution comparison analysis between the field and vaccine strains of porcine reproductive and respiratory syndrome virus in China

In order to understand the characteristics of the molecular evolution of porcine reproductive and respiratory syndrome virus(PRRSV) in China and provide a reference for PRRS prevention and control,this study analyzed the ORF5 gene and NSP2 gene sequence of 60 PRRSV strains from GenBank.The phylogenetic tree,based on the the ORF5 genes and NSP2 gene,showed that: the PRRSV strains could be divided into four subgroups,subgroup 1 was a main branch,JXA1 strain isolated in 2006 was a representative strain of HP-PRRSV in the subgroup 1,HP-PRRSV might have originated in the CH1-a and HB-1(sh)/2002 strain,which variation was gradually evolving process.HP-PRRSV was dominant in pandemic strains at present,and the high homology with the highly pathogenic vaccine strains(JAX1 and HUN4 of strains).