Betacoronaviruses: activation and antagonism of host innate immune responses

人类贝塔冠状病毒可引起多种呼吸道疾病。MERS冠状病毒(MERS)和SARS冠状病毒- 2(SARS-2)会导致严重的致命性肺炎，而SARS-2也会在 有些人。相比之下，感染“普通”呼吸道人类β-冠状病毒OC43的几率很小。 传到上呼吸道。由于只有几种药物显示出对抗人类Cov的前景，它仍然存在 迫切需要开发针对当前和未来新出现的人类冠状病毒的疗法。为此，我们需要确定 并了解所有这些病毒共有或不同的宿主与病毒的相互作用。我们的一个主要焦点是 实验室已经研究了双链(DS)RNA诱导的宿主对β-CoV的反应：干扰素的产生和 信号转导；寡核苷酸合成酶-核糖核酸酶L和蛋白激酶R，两者都是抗病毒和亲病毒的。 煽动性的。我们已经证明了保守的冠状病毒复制酶编码的nsp15内切核酸酶(Endo)U 减少所有三条途径的dsRNA积累和激活，而亚属特有的辅助蛋白 增加了对抗性。Merbeco(MERS-CoV)和Embeco(OC43)病毒关闭了这些途径 有效；相比之下，肉瘤病毒SARS-2在呼吸道来源的细胞中复制，尽管ALL被激活 三。初步数据提示，核糖核酸酶L下游对炎症和细胞死亡的影响可能更大 在SARS-2感染期间的影响比温和的抗病毒效果要好。PKR和PKR样ERK(PERK)，均为 整合应激反应的激酶，当被激活时，磷酸化蛋白质合成起始因子eIF2a， 导致蛋白质合成减弱，在感染中提供重要的控制点。PERK的激活也 启动对内质网应激的未折叠蛋白反应(UPR)的途径，产生抗病毒作用和 发炎。我们发现MERS和OC43感染通过阻止PKR抑制eIF2a的磷酸化 激活并通过PERK通路反馈环，使eIF2a去磷酸化。相比之下，SARS-2促进了 P-eIF2a通过PKR和PERK，但维持病毒蛋白合成。这可能部分通过冠状病毒发生 复制酶nsp1蛋白，促进宿主而不是病毒蛋白质合成的选择性衰减。我们的整体 假设每个亚属的贝塔冠状病毒都进化出了与宿主相互作用的独特方式。 这些差异会影响致病结果。 我们建议确定：保守的冠状病毒Endou和亚属特异性辅助蛋白在 拮抗宿主先天应答途径；L激活对病毒复制的影响， 炎症和细胞死亡；宿主PKR/PERK和病毒NSP1在蛋白质合成控制中的作用 和病毒复制。我们的总体目标是了解以下主机交互的异同 三个亚属的贝塔冠状病毒。我们的发现可能确定针对宿主或病毒的新的治疗干预措施 并表明它们是否可以作为泛冠状病毒的治疗方法，或者是每个贝塔冠状病毒亚属所特有的， 从而帮助为未来的冠状病毒爆发做好准备。

Human betacoronaviruses induce a wide spectrum of respiratory disease. MERS-CoV (MERS) and SARS-CoV- 2 (SARS-2), cause severe lethal pneumonia, while SARS-2 can also cause mild to asymptomatic disease in some individuals. In contrast, infections with the “common” respiratory human beta-CoV OC43 are largely limited to the upper respiratory tract. With only a few drugs that show promise against human CoVs, it remains imperative to develop therapeutics for current and future emergent human CoVs. For this, we need to identify and understand the host-virus interactions common to all or different among these viruses. A major focus of our lab has been on the double-stranded (ds)RNA induced host responses to beta-CoVs: interferon production and signaling; oligoadenylate synthetase-ribonuclease L and protein kinase R (PKR), that are both antiviral and pro- inflammatory. We have shown that the conserved CoV replicase encoded nsp15 endoribonuclease (Endo)U reduces dsRNA accumulation and activation of all three pathways while subgenera specific accessory proteins add to the antagonism. Merbeco (MERS-CoV) and embeco (OC43) viruses shut down these pathways effectively; in contrast, the sarbecovirus, SARS-2, replicates in respiratory derived cells despite activation of all three. Preliminary data suggest that downstream effects of RNase L on inflammation and cell death may be more impactful during SARS-2 infection than the modest antiviral effects. PKR and PKR-like ER kinase (PERK), both kinases of the integrated stress response, when activated, phosphorylate protein synthesis initiation factor eIF2a, leading to protein synthesis attenuation, providing an important control point in infection. Activation of PERK also initiates a pathways of the unfolded protein response (UPR) to ER stress, which produces antiviral effects and inflammation. We found that MERS and OC43 infection suppress phosphorylation of eIF2a by preventing PKR activation and through a PERK pathway feedback loop, dephosphorylating eIF2a. In contrast SARS-2 promotes p-eIF2a through both PKR and PERK, but maintains viral protein synthesis. This may occur in part via the CoV replicase nsp1 protein, which promotes selective attenuation of host, but not viral, protein synthesis. Our overall hypothesis is that betacoronaviruses of each subgenus have evolved unique ways to interact with host responses to optimize replication and spread and that these differences influence pathogenic outcomes. We propose to determine: the role of the conserved CoV EndoU and subgenera specific accessory proteins in antagonizing host innate response pathways; the impact of OAS-RNase L activation on viral replication, inflammation and cell death; and the effects of host PKR/PERK and viral nsp1 on control of protein synthesis and virus replication. Our overall goal is to understand the similarities and differences in host interactions among beta-CoVs of three subgenera. Our findings may identify novel therapeutic interventions targeting host or viral proteins and indicate whether they may work as pan-CoV therapies or be unique to each beta-CoV subgenus, and thus help prepare for future CoV outbreaks.