Institute of Applied Animal Technology, Mianyang Normal University, Mianyang, Sichuan, 621000, China; Research Center of Ecological Agriculture and Animal Husbandry in Northwest Sichuan, Mianyang, Sichuan, 621000, China.
Institute of Applied Animal Technology, Mianyang Normal University, Mianyang, Sichuan, 621000, China; College of Life Science, Southwest Forestry University, Kunming, Yunnan, 650224, China.
Microb Pathog. 2017 Nov;112:295-302. doi: 10.1016/j.micpath.2017.09.011. Epub 2017 Sep 29.
To monitor the genetic variation of PRRSV, the ORF5 gene of the PRRSV-SN strain found in Suining City, Sichuan Province, was cloned and sequenced. The results showed that the PRRSV-SN strain was a highly pathogenic PRRSV (HP-PRRSV) variant strain with the North American (NA) genotype. Homology analysis showed that the ORF5 gene of the PRRSV-SN isolate shared 89.4% (86.5%) nucleotide (amino acid) sequence similarity with the North American strain VR-2332, 98.8% (96%) similarity with JXA1, and 63.8% (57.7%) similarity with the European type representative strain Lelystad virus. Phylogenetic analysis showed that PRRSV-SN belongs to the NA genotype and has the same subtype as other highly pathogenic PRRSV strains. Amino acid sequence analysis showed that compared with the VR2332 strain, PRRSV-SN has different degrees of variation in the signal peptide, transmembrane region (TM), primary neutralizing epitope (PNE), non-neutral epitopes and N-glycosylation sites. Antigenicity analysis showed that the PRRSV-SN ORF5 gene products and JXA1 have similar antigenic characteristics, and the antigenic epitopes are mainly located in aa30-39, aa50-60, aa128-141, aa146-155 and aa161-183 regions. In contrast, the antigenic characteristics of PRRSV-SN are quite different from those of the VR2332 strain. The main differences were that the PRRSV-SN strain was significantly narrower than the VR2332 strain in the aa30-39 and the aa50-60 regions but was significantly wider in the aa136-141 region. The results of this study showed that the epidemic strains that cause PRRSV outbreaks in the farm are still mainly JXA1 variants, but due to the more frequent use of live vaccine immunizations, the genes of the PRRSV epidemic strain still show constant variation. Vaccination with live PRRSV should be reduced, and surveillance of PRRSV strains should be enhanced.
为监测 PRRSV 的遗传变异，对四川省遂宁市分离的 PRRSV-SN 株的 ORF5 基因进行了克隆和序列测定。结果表明，PRRSV-SN 株为高致病性 PRRSV（HP-PRRSV）变异株，具有北美（NA）基因型。同源性分析显示，PRRSV-SN 分离株的 ORF5 基因与北美 VR-2332 株核苷酸（氨基酸）序列相似性为 89.4%（86.5%），与 JXA1 株相似性为 98.8%（96%），与欧洲型代表株 Lelystad 病毒相似性为 63.8%（57.7%）。系统进化分析表明，PRRSV-SN 属于 NA 基因型，与其他高致病性 PRRSV 株具有相同的亚型。氨基酸序列分析表明，与 VR2332 株相比，PRRSV-SN 在信号肽、跨膜区（TM）、主要中和表位（PNE）、非中和表位和 N-糖基化位点有不同程度的变异。抗原性分析表明，PRRSV-SN 的 ORF5 基因产物与 JXA1 具有相似的抗原特征，抗原表位主要位于 aa30-39、aa50-60、aa128-141、aa146-155 和 aa161-183 区域。相比之下，PRRSV-SN 的抗原特征与 VR2332 株有很大的不同。主要差异在于 PRRSV-SN 株在 aa30-39 和 aa50-60 区域比 VR2332 株明显变窄，但在 aa136-141 区域明显变宽。本研究结果表明，引起猪场 PRRSV 暴发的流行株仍以 JXA1 变异株为主，但由于活疫苗免疫的应用更为频繁，PRRSV 流行株的基因仍存在持续变异。应减少活 PRRSV 疫苗的接种，并加强 PRRSV 株的监测。
