SARS-CoV-2 is the causative agent of the COVID-19 pandemic, with 10 million infections and more than 500,000 fatalities by June 2020. To initiate infection, the SARS-CoV-2 spike (S) glycoprotein promotes attachment to the host cell surface and fusion of the viral and host membranes. Prefusion SARS-CoV-2 S is the main target of neutralizing antibodies and the focus of vaccine design. However, its limited stability and conformational dynamics are limiting factors for developing countermeasures against this virus. We report here the design of a construct corresponding to the prefusion SARS-CoV-2 S ectodomain trimer, covalently stabilized by a disulfide bond in the closed conformation. Structural and antigenicity analyses show we successfully shut S in the closed state without otherwise altering its architecture. We demonstrate that this strategy is applicable to other β-coronaviruses, such as SARS-CoV and MERS-CoV, and might become an important tool for structural biology, serology, vaccine design and immunology studies.

SARS-CoV-2 是 COVID-19 大流行的病原体，到 2020 年 6 月将有 1000 万人感染，超过 500,000 人死亡。为了引发感染，SARS-CoV-2 刺突 (S) 糖蛋白促进与宿主细胞的结合病毒和宿主膜的表面和融合。Prefusion SARS-CoV-2 S是中和抗体的主要靶标，也是疫苗设计的重点。然而，其有限的稳定性和构象动力学是制定针对该病毒的对策的限制因素。我们在此报告了一种与预融合 SARS-CoV-2 S 胞外域三聚体相对应的结构设计，该结构通过闭合构象中的二硫键共价稳定。结构和抗原性分析表明我们成功地将 S 关闭在关闭状态，而没有改变其结构。