Isolation of Porcine Reproductive and Respiratory Syndrome Virus and Sequence Analysis of ORF5 and Nsp2 Genes

Two pairs of primers were designed and synthesized according to genome sequences of porcine reproductive and respiratory syndrome virus(PRRSV) available.The tissues of swine were detected by a RT-PCR method.Virus had been isolated and identified from the tissue whose detection turned to be positive.All the results indicated that the virus isolated was American PRRSV,which was designed GD08-2.ORF5 and Nsp2 genes of GD-XH,GD08-1 and the isolated strain GD08-2 were amplified,cloned and sequenced respectively.The results showed that ORF5 gene of GD08-2 had high similarity with PRRSV pMLV,PRRSV VR-2332 and GD-XH strain,but a little low with GD08-1.The discontinuous deletions of 12 amino acids were found at sites 66-74 and 192-194 in the peptide deduced from the Nsp2 gene,The results showed that the GD08-2 strain might be the deletion mutant isolate of PRRSV.The ORF5 gene of GD08-1 shared highly similarity with highly pathogenic PRRSV strains.The deletions of 30 amino acids in GD08-1 strain was consistent with the highly pathogenic PRRSV JXA1 strain.The results showed that the GD08-1 strain might be highly pathogenic PRRSV.The ORF5 gene of GD-XH strain shared highly similarity with PRRSV pMLV,and there were some deletions in the Nsp2 gene of GD-XH.Phylogenetic analysis showed that GD08-1 strain had the closest relationship with highly pathogenic PRRSV strains,and belonged to the same group,while GD08-2 strain and GD-XH strain were attributed to another group with PRRSV pMLV and VR-2332.