Department of Infectious Disease and Veterinary Public Health, Faculty of Animal Husbandry and Veterinary Medicine, Nong Lam University, Linh Trung Ward, Thu Duc City, Quarter 6, Ho Chi Minh City, Vietnam.
P&Y Livestock Service Company Limited, Ho Chi Minh City, Vietnam.
Virus Genes. 2022 Aug;58(4):361-366. doi: 10.1007/s11262-022-01912-w. Epub 2022 May 19.
The porcine reproductive and respiratory syndrome virus (PRRSV) causes more economic losses in the swine industry than any other virus. This study aimed to investigate the genetic diversity of PRRSV to assist in evaluating the effectiveness of PRRS vaccines. Twenty-eight samples from clinical cases were collected from 19 farms in seven provinces of Vietnam in 2021. Full-length PRRSV ORF5 genes from the 19 samples were amplified, sequenced, and compared to the corresponding sequences of referenced PRRSV strains from Genbank. The genetic analysis showed that 12 isolates were the highly pathogenic PRRSV subtype (HP-PRRSV) lineage 8, sublineage 8.7; six isolates were the classical North American PRRSV subtype (US-PRRSV), NADC-like group, lineage 1, sublineage 1.4, which were reported in Vietnam for the first time; and the final isolate was a vaccine-like strain. The field isolates of HP-PRRSV had relatively higher genetic diversity with US-PRRSV vaccine strains (84.0-94.5%) than HP-PRRSV vaccine strains (95.3-98.6%). Meanwhile, the six NADC-like isolates had low nucleotide similarity with US-PRRSV and HP-PRRSV vaccine strains (83.4-85.4% and 83.2-84.0%, respectively). Many amino acid substitutions were found in antigenic regions of GP5 involved in response to early antibody production, neutralizing antibodies, and viral immune evasion between these field strains and PRRSV vaccine strains. These findings provide insights into the molecular characteristics, genetic diversity, antigenicity, and evolution of PRRSV strains in Vietnam and postulate a compelling explanation for the limitations of current vaccination efforts.
猪繁殖与呼吸综合征病毒（PRRSV）是造成养猪业经济损失最大的病毒。本研究旨在调查 PRRSV 的遗传多样性，以帮助评估 PRRS 疫苗的效果。2021 年，从越南七个省的 19 个农场的临床病例中采集了 28 个样本。从这 19 个样本中扩增、测序并比较了全长 PRRSV ORF5 基因与 Genbank 中相应参考 PRRSV 株的序列。遗传分析显示，12 个分离株为高致病性 PRRSV 亚型（HP-PRRSV）谱系 8、亚谱系 8.7；6 个分离株为经典北美 PRRSV 亚型（US-PRRSV）、NADC 样群、谱系 1、亚谱系 1.4，这是越南首次报道；最后一个分离株为疫苗样株。与 US-PRRSV 疫苗株（84.0-94.5%）相比，HP-PRRSV 田间分离株具有相对较高的遗传多样性（95.3-98.6%）。同时，这 6 个 NADC 样分离株与 US-PRRSV 和 HP-PRRSV 疫苗株的核苷酸相似性较低（分别为 83.4-85.4%和 83.2-84.0%）。在 GP5 涉及早期抗体产生、中和抗体和病毒免疫逃避的抗原区域发现了许多氨基酸取代，这些田间株与 PRRSV 疫苗株之间存在。这些发现深入了解了越南 PRRSV 株的分子特征、遗传多样性、抗原性和进化，并对当前疫苗接种效果的局限性提出了有力的解释。
