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

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。

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

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.