Wei Chunhua, Liu Chen, Chen Guangsong, Yang Yuan, Li Jiarui, Dan Huijuan, Dai Ailing, Huang Cuiqin, Luo Manlin, Liu Jiankui
College of Life Sciences, Longyan University, Longyan, Fujian, 364012, China.
Fujian Provincial Key Laboratory for the Prevention and Control of Animal Infectious Diseases and Biotechnology, Longyan University, Longyan, Fujian, 364012, China.
BMC Vet Res. 2025 May 15;21(1):341. doi: 10.1186/s12917-025-04779-9.
Porcine reproductive and respiratory syndrome virus (PRRSV) is a major economic threat to the global swine industry. Currently, NADC30-like PRRSV has undergone complex recombination with local Chinese strains, which has exacerbated the evolution of PRRSV. Recently, new recombinant PRRSV-2 strains from four lineages (lineages 1, 3, 5, and 8) have emerged in China. However, information on the pathogenicity of the novel isolate in China remains limited. To further our knowledge about the isolate, FJLIUY2017 and PRRSV2/CN/G8/2018 were selected to analyze their pathogenicity for piglets.
The PRRSV FJLIUY2017 and PRRSV2/CN/G8/2018 strains were isolated by porcine alveolar macrophages (PAMs) and MARC-145CD. Complete genomic sequence analyses were conducted using the DNASTAR 7.0 software and the phylogenetic tree was constructed with MEGA 7.0. Recombination events were detected using RDP V4.10 and SIMPLOT software 3.5.1. Five PRRSV-free per group were inoculated with 2 mL (2 × 10 TCID50) of the FJLIUY-2017 and PRRSV2/CN/G8/2018. Clinical signs of disease were recorded daily after challenge. Blood samples were collected from all piglets on days 0, 4, 7, 11, and 14 dpi for analysis of viral load by IFA and PRRSV-specific antibody levels by ELISA kit. Lung gross and microscopic lesions of the inoculated piglets were examined by scoring system for lung lesion.
Full-length genome analysis revealed that FJLIUY2017 and PRRSV2/CN/G8/2018 share 89.2% identity with each other, and in particular, they had a low degree of homology (< 92%) with PRRSV sequences available in GenBank. Phylogenetic and recombination analyses revealed that the two strains were recombinant viruses from lineages 1, 3, 5.1, and 8.7 strains. Animal studies indicated that FJLIUY-2017 resulted in the typical clinical signs of PRRSV, including persistent fever, higher viremia, severe lung lesions, and 20% mortality, whereas PRRSV2/CN/G8/2018 caused moderate clinical symptoms and no mortality during the challenge period. Hyper-immune sera against the major vaccine strains JXA1-R (lineage 8) and Ingelvac PRRS MLV (Lineage 5) failed to neutralize two strains.
FJLIUY-2017 caused persistent fever, higher viremia, 20% mortality and exhibited higher pathogenicity in piglets compared to PRRSV2/CN/G8/2018. Our results suggest that recombination between different PRRSV-2 lineages can result in the development of PRRSV variants with increased pathogenicity.
猪繁殖与呼吸综合征病毒（PRRSV）是全球养猪业面临的重大经济威胁。目前，类NADC30 PRRSV已与中国本土毒株发生复杂重组，加剧了PRRSV的进化。最近，中国出现了来自四个谱系（谱系1、3、5和8）的新型重组PRRSV - 2毒株。然而，关于中国新型分离株致病性的信息仍然有限。为进一步了解该分离株，我们选择了FJLIUY2017和PRRSV2/CN/G8/2018来分析它们对仔猪的致病性。
通过猪肺泡巨噬细胞（PAMs）和MARC - 145CD分离PRRSV FJLIUY2017和PRRSV2/CN/G8/2018毒株。使用DNASTAR 7.0软件进行全基因组序列分析，并使用MEGA 7.0构建系统发育树。使用RDP V4.10和SIMPLOT软件3.5.1检测重组事件。每组五只无PRRSV的仔猪接种2 mL（2×10 TCID50）的FJLIUY - 2017和PRRSV2/CN/G8/2018。攻毒后每天记录疾病的临床症状。在攻毒后第0、4、7、11和14天从所有仔猪采集血液样本，通过间接荧光抗体试验（IFA）分析病毒载量，并通过ELISA试剂盒分析PRRSV特异性抗体水平。对接种仔猪的肺脏大体和微观病变通过肺脏病变评分系统进行检查。
全长基因组分析表明，FJLIUY2017和PRRSV2/CN/G8/2018彼此之间具有89.2%的同源性，特别是它们与GenBank中可用的PRRSV序列具有较低的同源性（<92%）。系统发育和重组分析表明，这两个毒株是来自谱系1、3、5.1和8.7毒株的重组病毒。动物研究表明，FJLIUY - 2017导致了PRRSV的典型临床症状，包括持续发热、更高的病毒血症、严重的肺部病变和20%的死亡率，而PRRSV2/CN/G8/2018在攻毒期间引起中度临床症状且无死亡。针对主要疫苗株JXA1 - R（谱系8）和英特威PRRS MLV（谱系5）的高免血清未能中和这两个毒株。
与PRRSV2/CN/G8/2018相比，FJLIUY - 2017导致持续发热、更高的病毒血症、20%的死亡率，并且在仔猪中表现出更高的致病性。我们的结果表明，不同PRRSV - 2谱系之间的重组可导致致病性增加的PRRSV变体的出现。
