Identifying host and viral correlates for coronavirus pathogenesis

摘要 冠状病毒 (CoV) 刺突蛋白是负责受体结合和受体结合的关键病毒决定因素。 融合/进入。刺突蛋白也被预测为驱动跨物种的主要因素 传播，导致 SARS 和 MERS 冠状病毒等流行病毒株的出现。之后的第一个十年里 SARS-CoV 的出现，流行病峰值的变化允许与新的宿主受体结合 被认为是这种人畜共患病出现的基础。然而，我们的工作表明，蝙蝠物种已经拥有 类 SARS 冠状病毒具有能够感染人类细胞的刺突蛋白。这些结果表明，对于一个子集 蝙蝠冠状病毒、受体结合和人类细胞感染并不是出现的主要障碍。 我们发现，尽管在体外复制效果相当，但含有蝙蝠冠状病毒刺突的嵌合病毒却减少了 体内毒力。感染了表达蝙蝠来源的 SHC014-CoV 刺突的嵌合 SARS-CoV 的小鼠 与 SARS-CoV 对照相比，体重减轻和致死率降低。重要的是，尽管这种衰减发生 与 SARS-CoV 在肺部的复制效果相当。结果表明，毒力由以下因素决定： 只是体外感染宿主细胞的能力。值得注意的是，我们还发现 SHC014 刺突嵌合体减少了 肺部大气道感染。这些初步数据形成了我们的中心假设，即 SARS- 冠状病毒的毒力取决于宿主与冠状病毒刺突蛋白的相互作用以及病毒基序。 了解导致气道感染减少的宿主和病毒机制可以预测体内 发病机制并对人畜共患病的出现具有重要意义。 在本提案中，我们探讨了减弱人畜共患 SHC014 尖峰的宿主因素和 CoV 尖峰变化 体内。在第一部分中，我们检查了趋向性变化，发现人畜共患病 SHC014 尖峰损害了上部 气道感染。我们预测这种不相容性与宿主蛋白酶活性的差异有关。我们 随后使用体外和体内两种方法定义介导这种衰减的特定宿主蛋白酶 接近。在第二部分中，我们使用鼠标适应和结构分析来预测尖峰变化 负责 SHC014 尖峰的衰减。我们随后生成突变病毒并恢复 SHC014 在体内尖峰或减弱 SARS 尖峰。最后，我们评估衰减机制 重点关注与宿主蛋白酶的尖峰相互作用。该提案共同确定了宿主蛋白酶和刺突蛋白 改变呼吸道感染并决定冠状病毒感染后毒力的相互作用。这些发现 为理解毒力提供重要见解，并对出现和产生重要影响 冠状病毒的传播。

Abstract The coronavirus (CoV) spike protein is a key viral determinant responsible for receptor binding and fusion/entry. The spike protein has also been predicted to be the major factor driving cross-species transmission, allowing the emergence of epidemic strains like SARS- and MERS-CoV. In the first decade after SARS-CoV emergence, changes to the epidemic spike that allowed binding to a new host receptor were thought to underlie this zoonotic emergence. However, our work has shown that bat species already harbor SARS-like CoVs with spike proteins capable of infecting human cells. These results argue that for a subset of bat CoVs, receptor binding and infection of human cells is not the major barrier for emergence. We found that despite equivalent replication in vitro, chimeric viruses containing bat CoV spikes have reduced virulence in vivo. Mice infected with a chimeric SARS-CoV expressing the bat derived SHC014-CoV spike had reduced weight loss and lethality compared to SARS-CoV controls. Importantly, this attenuation occurs despite equivalent replication to SARS-CoV in the lung. The results indicate that virulence is dictated by more than just the ability to infect host cells in vitro. Notably, we also found that the SHC014 spike chimera has reduced infection of the large airways of the lung. These preliminary data shaped our central hypothesis that SARS- CoV virulence is predicated on both host interactions with and viral motifs in the CoV spike protein. Understanding the host and viral mechanisms that drive reduced airway infection may predict in vivo pathogenesis and have critical implications for zoonotic emergence. In this proposal, we explore the host factors and CoV spike changes that attenuate the zoonotic SHC014 spike in vivo. In part one, we examine tropism changes finding that the zoonotic SHC014 spike has impaired upper airway infection. We predict that this incompatibility relates to differences in host protease activity. We subsequently define the specific host proteases that mediate this attenuation using both in vitro and in vivo approaches. In part two, we use mouse-adaptation and structural analysis to predict spike changes responsible for attenuation of the SHC014 spike. We subsequently generate mutant viruses and restore the SHC014 spike or attenuate the SARS spike in vivo. Finally, we evaluate the mechanism of attenuation focusing on spike interactions with host proteases. Together, the proposal identifies host proteases and spike interactions that alter airway infection and dictate virulence following coronavirus infection. These findings provide critical insights for understanding virulence as well as have important implications for emergence and transmission of coronaviruses.