乳猪“高热症”猪繁殖与呼吸综合征病毒的分离与致病性分析

Isolation and pathogenicity analysis of porcine reproductive and respiratory syndrome virus

本研究针对疑似高热症疫情的猪场,从分离病原的致病特性及基因特征,对高热症的病因进行了探索。以RT-PCR/PCR从临床病料中检测出猪繁殖与呼吸综合征病毒(PRRSV)、猪圆环病毒2型(PCV2)、猪瘟病毒(CSFV)核酸,利用Marc-145细胞从病料中分离到PRRSV(XS070425毒株)。测序结果显示,XS070425毒株Nsp2基因无高致病性PRRSV Nsp2基因533～561位连续29个氨基酸"RPVTPLSEPIPVPAPRRKFQQVKRLSSAA"的缺失;但遗传进化分析显示,XS070425毒株Nsp2、ORF5基因与近期我国报道的高致病性PRRSV-HuN4和JXA1有较高的同源性,达95%～96%。致病性试验显示,PRRSV-XS070425原始病料悬液和Marc-145细胞分离物接种健康猪后,病毒血症可持续26d,并出现典型的PRRS临床症状和体温升高,但不致死感染猪。这些结果说明,无NSP2蛋白29个氨基酸残基缺失的PRRSV也是猪高热症的重要病原。

To investigate the causative agent of swine ＂high fever syndrome＂, clinical samples were tested by RT-PCR/PCR for porcine reproductive and respiratory syndrome virus （PRRSV）, classic swine fever virus and porcine circovirus. An isolate of PRRSV strain, designated XS070425, was isolated fxom the sample using Marc-145 cell line. Sequence analysis indicated that the isolate had no deletion of 29 amino acids residues RPVTPLSEPIPVPAPRRKFQQVKRLSSAA within the nonstructural protein 2 （Nsp2） compared to high pathogenic PRRSV HuN4 and JXA1 isolates, but Nsp2 and ORF5 sequences of XS070425 shared 95 % -96 % homology to the high pathogenic PRRSV HuN4 and JXA1 isolates. To evaluate the pathogenicity of the XS070425, PRRSV-free pigs were inoculated intranasally with the homogenized tissue sample and the cell culture of XS070425, respectively. The infected pigs exhibited typical clinical symptoms of PRRSV and high fever, but all survived. These results indicated that PRRSV without a deletion of 29 residues within NSP2 protein was an important causative agent of swine ＂high fever syndrome＂ .