猪繁殖与呼吸综合征病毒非结构蛋白1α(nsp1α)的N端锌指结构是其抑制NLRP3炎症小体活性所必需

The Zinc-Finger Domain is Essential for Porcine Reproductive and Respiratory Syndrome Virus Nonstructural Protein 1α(nsp1α)to Inhibit the NLRP3Inflammasome

猪繁殖与呼吸综合征(PRRS)是严重危害养猪业的病毒性传染病之一,其致病原猪繁殖与呼吸综合征病毒(PRRSV)抑制宿主的天然免疫和特异性免疫反应,引起机体免疫抑制,造成持续性感染,从而给该病的防控带来困难。NLRP3炎症小体作为先天性免疫的重要组分在机体抗病毒中发挥重要作用。前期研究发现PRRSV能够激活NLRP3炎症小体,但PRRSV是否存在拮抗NLRP3炎症小体的组分还未见报道。本研究首先在缺失内源性炎症小体的HEK293T细胞中,共转染NLRP3、ASC、procaspase-1和pro-IL-1β四个真核表达质粒,建立NLRP3炎症小体的体外研究模型。然后,在该炎症小体模型细胞和猪肺泡巨噬细胞中,转染PRRSV nsp1α的真核表达质粒,结果表明nsp1α能够明显拮抗炎症小体的活化,而进一步的突变试验表明缺失N端锌指(ZF)结构或者突变ZF结构的nsp1α均不能抑制NLRP3炎症小体活化。本研究不仅首次发现了拮抗NLRP3炎症小体活化的PRRSV蛋白——nsp1α,而且发现nsp1α的N端锌指结构是其抑制NLRP3炎症小体活性所必需。本研究进一步发现了PRRSV拮抗天然免疫的新机制,并为PRRSV的防控提供了潜在的分子靶点和理论指导。

Porcine reproductive and respiratory syndrome(PRRS)is an important viral infectiousdisease in swine industry worldwide.The causative agent is porcine reproductive and respiratory syndrome virus(PRRSV),which can inhibit host innate and adaptive immune response,cause immunosuppression,and lead to persistent infection.So it is difficult to control and eradicate PRRS.As a critical part of innate immune,NLRP3 inflammasome plays an extremely important role in host anti-viral immunity.Previous studies have shown that PRRSV activated the NLRP3 inflammasome.However,whether there are components of PRRSV which suppress NLRP3 inflammasome remains unknown.Therefore,in the present study,we first reconstructed NLRP3 inflammasome through co-transfecting expression plasmids encoding NLRP3,ASC,procaspase-1,and pro-IL-1βin HEK293 T cells which are deficient in endogenous inflammasomes.Then,HEK293 Tcells and porcine alveolar macrophages(PAMs)were transfected with expression plasmid encoding nsp1αof PRRSV.The results indicated that nsp1αcan apparently block NLRP3 inflammasome activation.The further mutation experiments demonstrated that deletion or mutation of Zinc-Finger(ZF)domain in N-terminal of nsp1αfails to activate the NLRP3 inflammasome.Our study first demonstrated that nsp1αhad the ability to suppress the NLRP3inflammasome-mediated IL-1βsecretion and ZF domain was essential for nsp1αto inhibit the IL-1βinduction.Our study reveals a new mechanism that PRRSV antagonize host innate immune responses and may provide some insights into the research on molecular targets of anti-PRRSV drugs and prevention of PRRS.