A recombinant spike protein subunit vaccine confers protective immunity against SARS-CoV-2 infection and transmission in hamsters

Wu, Yangtao; Huang, Xiaofen; Yuan, Lunzhi; Wang, Shaojuan; Zhang, Yali; Xiong, Hualong; Chen, Rirong; Ma, Jian; Qi, Ruoyao; Nie, Meifeng; Xu, Jingjing; Zhang, Zhigang; Chen, Liqiang; Wei, Min; Zhou, Ming; Cai, Minping; Shi, Yang; Zhang, Liang; Yu, Huan; Hong, Junping; Wang, Zikang; Hong, Yunda; Yue, Mingxi; Li, Zonglin; Chen, Dabing; Zheng, Qingbing; Li, Shaowei; Chen, Yixin; Cheng, Tong; Zhang, Jun; Zhang, Tianying; Zhu, Huachen; Zhao, Qinjian; Yuan, Quan; Guan, Yi; Xia, Ningshao

Multiple safe and effective vaccines that elicit immune responses against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are necessary to respond to the ongoing coronavirus disease 2019 (COVID-19) pandemic. Here, we developed a protein subunit vaccine composed of spike ectodomain protein (StriFK) plus a nitrogen bisphosphonate-modified zinc-aluminum hybrid adjuvant (FH002C). StriFK-FH002C generated substantially higher neutralizing antibody titers in mice, hamsters, and cynomolgus monkeys than those observed in plasma isolated from COVID-19 convalescent individuals. StriFK-FH002C also induced both TH1- and TH2-polarized helper T cell responses in mice. In hamsters, StriFK-FH002C immunization protected animals against SARS-CoV-2 challenge, as shown by the absence of virus-induced weight loss, fewer symptoms of disease, and reduced lung pathology. Vaccination of hamsters with StriFK-FH002C also reduced within-cage virus transmission to unvaccinated, cohoused hamsters. In summary, StriFK-FH002C represents an effective, protein subunit-based SARS-CoV-2 vaccine candidate.