Variation Of Nsp2 Gene And ORF5 Gene Of Porcine Reproductive And Respiratory Syndrome Virus

Porcine reproductive and respiratory syndrome virus (PRRSV) is causative agent of porcine reproductive and respiratory syndrome (PRRS) which characterized by reproductive failure in sows and gilts, and severe pneumonia in neonatal piglets, resulting in great economic losses to the swine industry. The control and eradication of PRRS needs to better understand the variation and epidemioiogical status of PRRS.The Nsp2 gene and ORF5 gene variated mostly in the genome of PRRSV, thus focusing on analysis of Nsp2 gene and ORF5 gene could reflect variation of the genome at certain extent. In this study, the variation of the prevalent strains of PRRSV in China was analyzed based on sequencing and comparison of Nsp2 genes and ORF5 genes of different strains and constructing phylogenetic trees of Nsp2 gene and ORF5 gene.The partial Nsp2 genes and ORF5 genes were amplified from the tissue samples containing PRRSV by RT-PCR and cloned into pGEM-Teasy vector, and followed by sequencing. Ten sequences of the Nsp2 gene and 26 sequences of the ORF5 gene were obtained. Sequencing and comparative analysis showed that two sequences exhibited deletion in the Nsp2 gene, one was BJ-13 with a deletion of 3 nucleotides, the other (HB-4) with a deletion of 111 nucleotides.The obtained sequences were analyzed and compared with the published sequences of other strains by the molecular softwares. There was 76.1%~97.4% identity between those sequences of Nsp2 gene,, sharing 76.4%~99.6% and 38%~38.5% identity with VR2332 and LV respectively. There was 84.1%~99.8% identity among those sequences of ORF5 gene, sharing 86.4%~99.5% and 62.3 %~ 64.8% identity with VR2332 and LV respectively. The results showed that the prevalent PRRSV strains in China belonged to North American in genotype.The phylogenetic trees were generated while alignment of the sequences of the obtained Nsp2 gene and ORF5 gene with those published sequences of other strains. The phylogenetic tree based on the sequences of ORF5 gene indicated the PRRSV strains belonging to North American genotype could be divided into four subgroups. The prevalent strains in China presented three subgroups: BJ-4 and some strains fall into subgroup 1; CH-1a, HB-1, HB-2 belonged to subgroup 2; One strain (BJ-13) located in subgroup 4 was firstly recognized. The sequnences of different subgroups from different area showed diversity on potential glycosylation sites, antigenic epitope regions and the amino acids associated with virulence of PRRSV by comparison of the deduced amino acids of ORF5 gene.