Molecular epidemiological investigation of prevalent porcine reproductive and respiratory syndrome virus strains in Anhui Province from 2006 to 2008.

ORF5 gene of seven PRRSV strains was amplified by RT-PCR from tissue samples in Anhui Province from 2006 to 2008 year.The sequence of PRRSV ORF5 gene was analyzed and the antigen sites were predicted.The results showed that the amino acids homology shared from 85.1% to 86.1%,from 90.5% to 92.5%,and from 96.5% to 98.5% among Anhui prevalent strains and VR-2332,CH-1a,JXA1 strains.Compared with the acquired strain before 2006,Anhui strains had the same amino acids mutational sites(G9→C9,S16→F16,S35→N35,V94→A94 and V185→A185).The virulence of PRRSV could be strengthened because key amino acids sites mutation.The six major antigen sites of Anhui strains and JXA1 strain GP5 protein was predicted.Owing to amino acids mutation of the GP5 epitope(A27→V27,L39→I39,V185→A185 and I189→L189),antigenicity of Anhui strains and JXA1 strain had changed compared with VR-2332 and CH-1a strains.The phylogenetic tree revealed that Anhui strains had closer relationship with JXA1 and TZ strains.It was concluded that Anhui strains which were prevalent in Anhui from 2006 to 2008 year were the same strain.