Sequence analysis of the NSP2, ORF5, and ORF7 genes of 11 PRRS virus isolates from China.

During a tracing investigation of blue ear disease in China conducted from January to November 2008, 11 porcine reproductive and respiratory syndrome virus (PRRSV) isolates were collected from eight provinces including Liaoning, Jilin, Hebei, Shandong, Henan, Shanghai, Zhejiang, and Guangxi. The complete gene sequences of the NSP2, ORF5, and ORF7 genes from these 11 PRRSV isolates were amplified, cloned and detected by RT-PCR and then compared with the published sequences of other strains. The results showed that all of the isolates genotypically belonged to an American strain, but shared high homology with JXA1, the highly pathogenic strain endemic to China. All of the 11 PRRSV isolates demonstrated a 90-nucleotide deletion in the NSP2 gene, suggesting that the main epidemic of PRRSV in 2008 was due to this gene deletion isolate. More consistent mutations were found in specific regions of the ORF5 and ORF7 genes of the 11 PRRSV isolates, such as the signal peptide and transmembrane regions of GP5 and the Pat 7 motif of the N protein. Whether these mutations influence nuclear localization of PRRSV requires confirmation by future studies.