Isolation, identification and genomic analysis of HP-PRRSV obtained from one province in east China.

【Objective】PRRSV strains from pig IFArms suspected to have broken out PRRS in 3 different regions of one province in middle east China were isolated.The genome of the obtained PRRSV isolates was determined and then molecular characteristics of dominant strains was analyzed,the evolutionary law of PRRSVs isolated in China recent years according detaild sequences analysis was observed.【Method】 Samples of lymph nodes and lungs from dead or sick pigs were collected,treated samples by PRRSV RTPCR were determined,then the strains from positive samples were isolated.IFA was conducted after the i-solation and TCID50 of IFA-positive isolates was measured.6 pairs of primers were designed based on PRRSV VR-2332,CH-1a,HB2 and JXA1 and other PRRSV strains available on NCBI Genebank.The genome of obtained PRRSV isolates were amplified and determined by these primers.Detailed sequences anal-ysis and evolutionary relationship research among 3 obtained isolates and LV,VR-2332,JXA1 and other 13 domestic and foreign representative strains or isolates were carried out.【Result】3PRRSVstrains were obtained and were named as SDCXA/2008,SDWF and SDLY respectively.The Blast result of complete genome indicated that all 3 isolates were Amercian-type strains.According to the sequences analysis,the genome sequences of 3 isolates showed a very low identity of 61.6%-61.8% with Europe-type PRRSV,a relatively low identity of 86.6%-97.1% with American-type strains isolated before 2006,a high identity of 98.3%-99.7% with American-type strains isolated after 2006.Nsp2gene was the most variable labile gene compared with ORF5 and ORF3 gene.ORF5 gene was more mutable than ORF3 gene.The deduced aa of Nsp2 gene was most variable too.The sequences analysis showed that all 3 isolates were high pathogenic PRRSV like representative HP-PRRSV strains of JXA1and HUN4 having 30 discontinuous aa deletions at the position of 481and 532-560aa site in Nsp2 deduced aa sequence.The sequences analysis with and phylogenetic tree was combined and 3obtained HP-PRRSV strains were clossified into JXA1-like HPPRRSV group.【Conclusion】3HP-PRRSV strains were obtained,the genetic characteristics of 3 strains showed to be comparatively stable,but some mutations appeared in the genomes suggested that the PRRSVs would continually evolve with variation in future.The result also showed that there were no apparent relations between the distribution features of PRRSVs and the places.