Cao Xiaoyu, Ge Xinna, Zhang Yongning, Guo Xin, Han Jun, Zhou Lei, Yang Hanchun
National Key Laboratory of Veterinary Public Health and Safety, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Key Laboratory of Animal Epidemiology of Ministry of Agriculture and Rural Affairs, College of Veterinary Medicine, China Agricultural University, Beijing, China.
Transbound Emerg Dis. 2023 Jul 22;2023:8871321. doi: 10.1155/2023/8871321. eCollection 2023.
Porcine reproductive and respiratory syndrome virus (PRRSV) is an economically devastating pathogenic microorganism that greatly affects the pork industry in the world. The genetic variation and frequent emergence of novel strains greatly hinder the control efforts of PRRSV. Therefore, monitoring the evolutionary dynamics is long and rewarding work for PRRSV researchers and practitioners to make the control strategy. Here, three novel PRRSV strains named CHbj2101, CHbj2102, and CHbj2103 were isolated from different nursery barns with various mortality rates from 6% to 17%, belonging to the same farm, but at different periods of the outbreak. The genomic sequencing and phylogenetic analyses indicated that these three isolates were all clustered with NADC30-like virus CHsx1401, sharing higher genomic similarity from 87.3% to 89.8%, and having the same molecular marker of 131 amino acid residues deletion at their nsp2 coding region, but varied mutagenesis among the antigenic sites in the region of GP2 to GP5. Among the available PRRSV sequences in the GenBank, the isolates CHbj2101 and CHbj2102 display the highest genomic identity (90.1% and 89.8%) with NADC30-like recombinant strain 15LN3, and the rest CHbj2103 shows the highest genomic identity (90.8%) with NADC30-like virus strain 15SC3. The recombination analysis indicated that all three isolates are generated by multiple recombination events among the NADC30-like virus (major parent, Lineage 1), HP-PRRSV vaccine-like virus (minor parent, Lineage 8), and QYYZ-like virus (minor parent, Lineage 3). The isolates CHbj2101 and CHbj2102 shared a similar recombination pattern, but CHbj2103 has a different pattern in nonstructural protein coding regions. To further investigate the recombination characteristics of QYYZ-like strains, we analyzed all available whole genomic sequences of QYYZ-like PRRSV, submitted during the year 1991 and 2021 ( = 83) in China. The result shows that almost all QYYZ-like strains were products of recombination and their immunogenicity or protective protein fragments (nsp2-nsp7 and GP2-GP4) were mainly from QYYZ. These results provide us with some better insight into the evolution process of PRRSV strains in the field and warn us to pay more attention to monitoring and reducing the PRRSV variant on farms to reduce the risk of novel emergence and outbreak.
猪繁殖与呼吸综合征病毒（PRRSV）是一种对经济具有毁灭性影响的致病微生物，极大地影响着全球猪肉产业。该病毒的基因变异以及新毒株的频繁出现，极大地阻碍了PRRSV的防控工作。因此，监测其进化动态对于PRRSV研究人员和从业者制定防控策略而言，是一项长期且有意义的工作。在此，从同一养殖场不同保育舍中分离出三株新型PRRSV毒株，分别命名为CHbj2101、CHbj2102和CHbj2103，这些保育舍的死亡率在6%至17%之间，且处于疫情爆发的不同阶段。基因组测序和系统发育分析表明，这三株分离株均与NADC30样病毒CHsx1401聚类，基因组相似性较高，在87.3%至89.8%之间，并且在其nsp2编码区具有相同的131个氨基酸残基缺失的分子标记，但在GP2至GP5区域的抗原位点存在不同的诱变情况。在GenBank中现有的PRRSV序列中，分离株CHbj2101和CHbj2102与NADC30样重组毒株15LN3显示出最高的基因组同一性（分别为90.1%和 89.8%）；其余的CHbj2103与NADC30样病毒株15SC3显示出最高的基因组同一性（90.8%）。重组分析表明，所有三株分离株均由NADC30样病毒（主要亲本，谱系1）、高致病性PRRSV疫苗样病毒（次要亲本，谱系8）和QYYZ样病毒（次要亲本，谱系3）之间的多次重组事件产生。分离株CHbj2101和CHbj2102具有相似的重组模式，但CHbj2103在非结构蛋白编码区具有不同的模式。为了进一步研究QYYZ样毒株的重组特征，我们分析了1991年至2021年期间在中国提交的所有可用的QYYZ样PRRSV全基因组序列（n = 83）。结果表明，几乎所有QYYZ样毒株都是重组产物，其免疫原性或保护性蛋白片段（nsp2 - nsp7和GP2 - GP4）主要来自QYYZ。这些结果为我们更好地洞察田间PRRSV毒株的进化过程提供了一些依据，并警示我们要更加重视养殖场中PRRSV变异株的监测和减少，以降低新毒株出现和爆发的风险。
