Gao Jiming, Ji Pengchao, Zhang Maodong, Wang Xiangpeng, Li Na, Wang Chengbao, Xiao Shuqi, Mu Yang, Zhao Qin, Du Taofeng, Sun Yani, Hiscox Julian A, Zhang Gaiping, Zhou En-Min
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling 712100, China; Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, Ministry of Agriculture of the People's Republic of China, No. 22 Xinong Road, Yangling, Shaanxi 712100, China.
Department of Preventive Veterinary Medicine, College of Veterinary Medicine, Northwest A&F University, Yangling 712100, China; Experimental Station of Veterinary Pharmacology and Veterinary Biotechnology, Ministry of Agriculture of the People's Republic of China, No. 22 Xinong Road, Yangling, Shaanxi 712100, China.
Vet Microbiol. 2014 Dec 5;174(3-4):409-418. doi: 10.1016/j.vetmic.2014.09.030. Epub 2014 Oct 14.
The major neutralizing epitope of porcine reproductive and respiratory syndrome virus (PRRSV) is mainly located on virus glycoprotein 5 (GP5). Immunization with exogenous GP5 or exposure to native GP5 by means of DNA immunization can provide some degree of immune protection to PRRSV infection in pigs. However, during PRRSV infection in pigs, the production of neutralization antibodies induced by GP5 is delayed or suppressed. This suggests that the synthesis of GP5 is late than some PRRSV proteins or other PRRSV proteins interfering with the function of GP5 in inducing host responses during virus infection. Here, to exclude the impacts of the other PRRSV proteins and determine the role of GP5 in the replication of PRRSV in vitro, a Marc-145 cell line stably expressing GP5 (Marc-145-GP5(Flag)) was constructed. Cell proliferation and cell apoptosis measurements indicated that the expression of GP5 in Marc-145 cells did not disturb the cells' viability. Following infection with different PRRSV strains PRRSV replication in Marc-145-GP5(Flag) cells was inhibited significantly. Type I interferon assay results showed that beta interferon (IFN-β) in the Marc-145-GP5(Flag) cells were increased at mRNA and protein levels. When siRNA was introduced into the cells to knock down IFN-β mRNA, PRRSV infectivity of these cells was recovered. These data suggest that early GP5 expression is not favorable for further infection by PRRSV, because it not only stimulates production of neutralization antibodies in pigs, but also induces IFN-β production in host cells. Therefore, GP5 is an important protein in the induction of self-protection responses from the host.
猪繁殖与呼吸综合征病毒（PRRSV）的主要中和表位主要位于病毒糖蛋白5（GP5）上。用外源性GP5免疫或通过DNA免疫接触天然GP5可在一定程度上为猪抵抗PRRSV感染提供免疫保护。然而，在猪感染PRRSV期间，由GP5诱导产生的中和抗体的产生会延迟或受到抑制。这表明GP5的合成比一些PRRSV蛋白晚，或者其他PRRSV蛋白在病毒感染期间干扰了GP5诱导宿主反应的功能。在此，为排除其他PRRSV蛋白的影响并确定GP5在PRRSV体外复制中的作用，构建了稳定表达GP5的Marc-145细胞系（Marc-145-GP5(Flag)）。细胞增殖和细胞凋亡检测表明，Marc-145细胞中GP5的表达并未干扰细胞活力。用不同PRRSV毒株感染后，Marc-145-GP5(Flag)细胞中的PRRSV复制受到显著抑制。I型干扰素检测结果显示，Marc-145-GP5(Flag)细胞中的β干扰素（IFN-β）在mRNA和蛋白水平均升高。当将siRNA导入细胞以敲低IFN-β mRNA时，这些细胞的PRRSV感染性得以恢复。这些数据表明，早期GP5表达不利于PRRSV的进一步感染，因为它不仅刺激猪体内中和抗体的产生，还诱导宿主细胞产生IFN-β。因此，GP5是诱导宿主自我保护反应的重要蛋白。
