结构域B在鼠冠状病毒S蛋白的抗原性及膜融合中的作用

Domain B of murine coronavirus spike protein is necessary for the membrane fusion and antigenicity

棘突(spike,S)蛋白是冠状病毒表面必不可少的跨膜糖蛋白,在病毒进入宿主细胞时具有结合受体和诱导膜融合的双重作用。大部分冠状病毒S蛋白的受体结合域位于S1-CTD(即相对应的结构域B),而经典的乙型冠状病毒模型鼠肝炎病毒(mouse hepatitis virus,MHV)的受体mCEACAM1a与S1-NTD(即相对应的结构域A)结合,其结构域B的作用仍未完全清楚。本研究通过构建结构域B和S2膜融合元件的缺失突变体,并使其在鼠神经母细胞瘤细胞系Neuro-2a内成功表达,证实了结构域B对病毒S蛋白导致的细胞-细胞间膜融合是必需的。用不同方法处理的病毒颗粒作为抗原免疫小鼠,所获得的多克隆抗体进一步显示,结构域B不但是S蛋白的主要抗原决定簇,而且能诱导中和抗体明显抑制病毒感染和S蛋白介导的膜融合作用。此结果为阐述不同冠状病毒的致病性与感染性差异提供了新思路。

Spike(S)protein is an essential transmembrane glycoprotein on the surface of coronaviruses.It has dual functions of receptor binding and membrane fusion for infection.Although most of the receptor binding domains(RBD)of S proteins are located in S1-CTD,or domain B,the receptor for beta-coronavirus mouse hepatitis virus(MHV)binds to S1-NTD,or domain A,and the role of domain B remains unclear.By constructing and expression of domain B deletion mutants of S protein with S2 membrane fusion in neuroblastoma cell line Neuro-2a,we proved that the domain B is essential for cell-cell membrane fusion mediated by the S protein.Further analysis of polyclonal antibodies generated in mice revealed that domain B is not only the major antigenic determinant of S protein,but also a domain for significant neutralizing antibodies to inhibit viral infection.These results provided insights into the role of S protein in pathogenicity and infection of coronaviruses.