拉沙病毒(LASV)是一种哺乳动物病毒,可导致致命的拉沙热疾病,没有FDA批准的疫苗和有限的治疗选择。致命的LASV感染与先天免疫抑制有关。我们以前已经证明LASV的小基质Z蛋白,但不是一种非致病性沙粒病毒匹金德病毒(PICV),可以抑制细胞RIG-I样受体(RLRs),但是由于病毒生命周期所需的Z蛋白的多种基本功能,因此尚未在感染性病毒中评估其生物学意义。在这项研究中,我们开发了一种稳定的HeLa细胞系(HeLa-iRIGN),该细胞系可以通过多西环素(Dox)处理快速而稳健地诱导表达RIG-IN末端效应子,同时产生I型干扰素(IFN-Is)。我们还产生了重组三段PICV,rP18tri-LZ,和rP18tri-PZ,编码LASVZ和PICVZ,分别,作为一种额外的mScarlet融合蛋白,对病毒生命周期是非必需的。一旦感染,rP18tri-LZ始终以高于rP18tri-PZ的水平表达病毒基因。rP18tri-LZ在HeLa-iRIGN细胞中也显示出比rP18tri-PZ更高的病毒感染水平,尤其是在Dox诱导时。通过生长曲线分析,异源Z基因没有改变Vero和A549细胞中的病毒生长,而LASVZ强烈增加和延长病毒基因表达,特别是在有IFN能力的A549细胞中。我们的研究为LASVZ介导的RIG-I抑制的生物学作用提供了重要见解,并暗示LASVZ是潜在的毒力因子。重要性拉沙病毒(LASV)可引起人类致命的出血热疾病,但其他沙粒病毒,如皮钦德病毒(PICV),不要引起明显的疾病。我们以前已经证明LASV的Z蛋白而不是PICV的Z蛋白可以抑制RIG-I,一种胞浆先天免疫受体。在这项研究中,我们开发了一个稳定的HeLa细胞系,可以被诱导表达RIG-IN末端效应子结构域,这允许RIG-I激活的及时控制。我们还产生了编码LASVZ或PICVZ的重组PICV,作为病毒生命周期非必需的额外基因。与PICVZ相比,LASVZ可以增加传染性沙粒病毒系统中的病毒基因表达和病毒感染,特别是当RIG-I信号被激活时。我们的研究提出了一种方便的细胞系统来表征RIG-I信号及其拮抗剂,并揭示了LASVZ作为可能的毒力因子和潜在的抗病毒靶标。
Lassa virus (LASV) is a mammarenavirus that can cause lethal Lassa fever disease with no FDA-approved vaccine and limited treatment options. Fatal LASV infections are associated with innate immune suppression. We have previously shown that the small matrix Z protein of LASV, but not of a nonpathogenic arenavirus Pichinde virus (PICV), can inhibit the cellular RIG-I-like receptors (RLRs), but its biological significance has not been evaluated in an infectious virus due to the multiple essential functions of the Z protein required for the viral life cycle. In this study, we developed a stable HeLa cell line (HeLa-iRIGN) that could be rapidly and robustly induced by doxycycline (Dox) treatment to express RIG-I N-terminal effector, with concomitant production of type I interferons (IFN-Is). We also generated recombinant tri-segmented PICVs, rP18tri-LZ, and rP18tri-PZ, which encode LASV Z and PICV Z, respectively, as an extra mScarlet fusion protein that is nonessential for the viral life cycle. Upon infection, rP18tri-LZ consistently expressed viral genes at a higher level than rP18tri-PZ. rP18tri-LZ also showed a higher level of a viral infection than rP18tri-PZ did in HeLa-iRIGN cells, especially upon Dox induction. The heterologous Z gene did not alter viral growth in Vero and A549 cells by growth curve analysis, while LASV Z strongly increased and prolonged viral gene expression, especially in IFN-competent A549 cells. Our study provides important insights into the biological role of LASV Z-mediated RIG-I inhibition and implicates LASV Z as a potential virulence factor. IMPORTANCE Lassa virus (LASV) can cause lethal hemorrhagic fever disease in humans but other arenaviruses, such as Pichinde virus (PICV), do not cause obvious disease. We have previously shown that the Z protein of LASV but not of PICV can inhibit RIG-I, a cytosolic innate immune receptor. In this study, we developed a stable HeLa cell line that can be induced to express the RIG-I N-terminal effector domain, which allows for timely control of RIG-I activation. We also generated recombinant PICVs encoding LASV Z or PICV Z as an extra gene that is nonessential for the viral life cycle. Compared to PICV Z, LASV Z could increase viral gene expression and viral infection in an infectious arenavirus system, especially when RIG-I signaling is activated. Our study presented a convenient cell system to characterize RIG-I signaling and its antagonists and revealed LASV Z as a possible virulence factor and a potential antiviral target.