山东PRRSV流行株ORF5、ORF6、ORF7基因序列的分子特征

采用RT-PCR技术对2001～2007年分离自山东地区10株(ShanDong-3、SD-JN、SD-ZQ、SD1、SD2、SD3、SD4、SD5、SD6和SD7)猪繁殖与呼吸综合征病毒(PRRSV)进行ORF5、ORF6和ORF7基因的扩增、克隆和测序,与已知序列的毒株的相应片段进行同源性分析比较,并对其分子特征进行分析.结果表明:该10株病毒仍属北美洲型,其中2001～2002年分离的SD1株、SD2株和2006年分离的SD6株核苷酸序列之间的ORF5、ORF6、ORF7同源性分别为99.2%,99.8%,100%,均与北美洲原型代表株(VR-2332株)和疫苗毒MLVRespPRRS Repro USA遗传距离较近,同属一大分支;2006～2007年分离的PRRSV ShanDong-3、SD-JN、SD-ZQ 、SD3,SD4,SD5, SD7分离株ORF5、ORF6、ORF7同源性分别为97.8%～100%,99.4%～99.8%,99.2%～99.7%,均与国内96年Ch-1a和2002年HB-1株及2006年分离鉴定的国内高致病性分离株(JXA1、Shanghai、HEB1)同属一个大的分支.首次证实目前山东省同时存在高致病性PRRSV和传统PRRSV,并且有由传统PRRSV向高致病性PRRSV演化的趋势.

Cloning and Genetic Analysis of ORF5,ORF6,ORF7 of PRRSV Isolated in Shandong Province

The ORF5,ORF6 and ORF7 genes of PRRSV isolates from Shandong in 2001～2007 were amplified by RT-PCR.The products were sequenced after cloning into pMD18-T vectors respectively.The sequences were analysed and compared with other PRRSV isolates in GenBank.The results indicated that the homology of ORF5,ORF6 and ORF7 of SD1 and SD2 which isolated in 2001～2002 and SD6 which isolated in 2006 were 99.2%,99.8% and 100% respectively ,with two isolates-North American(VR-2332) and vaccinal strain (MLVRespPRRS Repro USA) belonged to the same subgroup; the ORF5,ORF6 and ORF7 of Shandong-3,SD-JN,SD-ZQ,SD3,SD4,SD5,SD7 which isolated in 2006～2007 shared 97.8%～100%,99.4%～99.8%,99.2%～99.7% respectively.The seven strains together with Ch-la(1996),HB-1(2002)and the highly pathogenic PRRSV(JXA1,Shanghai,HEB1)were in the same subgroup.It was first found that conventional PRRSV and highly pathogenic PRRSV were both in Shandong Province simultaneously and tended to change from conventional PRRSV to highly pathogenic PRRSV.