Key Laboratory of Animal Epidemiology of the Ministry of Agriculture, College of Veterinary Medicine and State Key Laboratory of Agrobiotechnology, China Agricultural University, Beijing, 100193, China.
Virol Sin. 2019 Dec;34(6):631-640. doi: 10.1007/s12250-019-00149-6. Epub 2019 Jul 25.
Porcine reproductive and respiratory syndrome virus (PRRSV) is characterized by its genetic variation and limited cross protection among heterologous strains. Even though several viral structural proteins have been regarded as inducers of neutralizing antibodies (NAs) against PRRSV, the mechanism underlying limited cross-neutralization among heterologous strains is still controversial. In the present study, examinations of NA cross reaction between a highly pathogenic PRRSV (HP-PRRSV) strain, JXwn06, and a low pathogenic PRRSV (LP-PRRSV) strain, HB-1/3.9, were conducted with viral neutralization assays in MARC-145 cells. None of the JXwn06-hyperimmuned pigs' sera could neutralize HB-1/3.9 in vitro and vice versa. To address the genetic variation between these two viruses that are associated with limited cross-neutralization, chimeric viruses with coding regions swapped between these two strains were constructed. Viral neutralization assays indicated that variations in nonstructural protein 2 (nsp2) and structural proteins together contribute to weak cross-neutralization activity between JXwn06 and HB-1/3.9. Furthermore, we substituted the nsp2-, glycoprotein2 (GP2)-, GP3-, and GP4-coding regions together, or nsp2-, GP5-, and membrane (M) protein-coding regions simultaneously between these two viruses to construct chimeric viruses to test cross-neutralization reactivity with hyperimmunized sera induced by their parental viruses. The results indicated that the swapped nsp2 and GP5-M viruses increased the neutralization reactivity with the donor strain antisera in MARC-145 cells. Taken together, these results show that variations in nsp2 and GP5-M correlate with the limited neutralization reactivity between the heterologous strains HP-PRRSV JXwn06 and LP-PRRSV HB-1/3.9.
猪繁殖与呼吸综合征病毒（PRRSV）的遗传变异和不同毒株之间交叉保护作用有限是其主要特征。尽管已有几种病毒结构蛋白被认为是诱导针对 PRRSV 的中和抗体（NA）的诱导物，但不同毒株之间交叉中和作用有限的机制仍存在争议。在本研究中，通过 MARC-145 细胞中的病毒中和试验，对高致病性 PRRSV（HP-PRRSV）JXwn06 株和低致病性 PRRSV（LP-PRRSV）HB-1/3.9 株之间的 NA 交叉反应进行了检测。JXwn06 高免猪血清均不能中和 HB-1/3.9，反之亦然。为了解决与交叉中和作用有限相关的这两种病毒之间的遗传变异，构建了这两种毒株之间编码区交换的嵌合病毒。病毒中和试验表明，非结构蛋白 2（nsp2）和结构蛋白的变异共同导致了 JXwn06 和 HB-1/3.9 之间弱的交叉中和活性。此外，我们同时在这两种病毒之间替换 nsp2、糖蛋白 2（GP2）、GP3 和 GP4 编码区，或 nsp2、GP5 和膜（M）蛋白编码区，构建嵌合病毒，以测试其母本病毒诱导的高免血清的交叉中和反应性。结果表明，交换 nsp2 和 GP5-M 的嵌合病毒增加了与供体株抗血清在 MARC-145 细胞中的中和反应性。综上所述，这些结果表明，nsp2 和 GP5-M 的变异与异源株 HP-PRRSV JXwn06 和 LP-PRRSV HB-1/3.9 之间有限的中和反应性相关。
