PRRSV上海浦东南汇分离株Nsp2与ORF5基因遗传演化分析

Geneticevolution analysis of NSP2 and ORF5 genes of porcine reproductive and respiratory syndrome virus from Nanhui in Pudong District of Shanghai

对上海浦东南汇地区某规模猪场猪繁殖与呼吸综合征病毒(PRRSV)疑似病料进行处理,提取病毒总RNA,采用RT-PCR方法扩增Nsp2/ORF5基因,并进行基因测序。序列分析结果表明,浦东南汇分离株Nsp2蛋白均缺失481位和第533~561位30个不连续的氨基酸,同时在Nsp2编码区出现与高致病性PRRSV(HP-PRRSV)代表株JXA1相同的遗传变异现象。同源性分析表明,6株Nsp2、ORF5氨基酸序列与VR-2332、CH-1a、HB-2以及JXA1株的同源性分别为:40.3%~55.3%,73.5%~89.5%;54.7%~75.1%,75.5%~92.5%;50.9%~67.3%,73.5%~90.5%;72.8%~91.5%,81.5%~98.5%;而与欧洲型代表株LV株的同源性分别仅为26.2%~35.9%和44.8%~56.4%。遗传演化分析表明,浦东南汇分离株与国内株(CH-1a、HB-2)和VR-2332美洲代表株各自处于相对独立的分支,遗传关系较远且不存在交叉现象,而与JXA1变异株处于同一进化分支。研究表明,浦东南汇分离株为美洲型HP-PRRSV毒株,具有一定的地理衍变特性,已从PRRSV遗传进化树中分离,出现一个新的遗传独立群体。

Genetic evolution of porcine reproductive and respiratory syndrome virus（ PRRSV） in Nanhui of Shanghai was investigated in order to provide the theoretical basis for prevention and control of PRRS. Clinical samples from some scale farms suspicious of PRRSV infection were collected. RNA was extracted and Nsp2 and ORF5 genes were amplified by PCR and sequenced. Sequence analysis revealed that all isolated strains of Nanhui had discontinuous 30 amino acid deletion in 481 aa and 533 to 561 aa in Nsp2 protein,and had the same multiple genomic variations in different regions with that of the highly pathogenicity PRRSV（ HP-PRRSV） JXA1. Amino acid sequence comparison of Nsp2 and ORF5 demonstrated that the six strains shared 40. 3%-55. 3%,73. 5% ~ 89. 5%; 54. 7% ~ 75. 1%,75. 5% ~ 92. 5%; 50. 9% ~67. 3%,73. 5% ~ 90. 5%; 72. 8% ~ 91. 5%,81. 5% ~ 98. 5% identities with VR-2332,CH-1a,HB-2 and JXA1,respectively. But there were 26. 2% ~ 35. 9% and 44. 8% ~ 56. 4% amino acid sequence identities in Nsp2 and ORF5,respectively,with European prototype Lelystad virus strain. Phylogenetic analysis showed that Nanhui strains located a relatively independent branch from domestic strains（ CH-1a,HB-2） and North American genotype VR-2332,but in the same evolutionary branch with JXA1 strains. The results indicated that the six PRRSV strains from Nanhui belong to North America HP-type and have certain geographical development feature. And these strains have been independent from the tree of PRRSV genetic evolution and form a new genetic group.