RBD-homodimer, a COVID-19 subunit vaccine candidate, elicits immunogenicity and protection in rodents and nonhuman primates

Pan, Xiaoyan; Shi, Jian; Hu, Xue; Wu, Yan; Zeng, Liang; Yao, Yanfeng; Shang, Weijuan; Liu, Kunpeng; Gao, Ge; Guo, Weiwei; Peng, Yun; Chen, Shaohong; Gao, Xiaoxiao; Peng, Cheng; Rao, Juhong; Zhao, Jiaxuan; Gong, Cheng; Zhou, Hui; Lu, Yudong; Wang, Zili; Hu, Xiliang; Cong, WenJuan; Fang, Lijuan; Yan, Yongxiang; Zhang, Jing; Xiong, Hui; Yi, Jizu; Yuan, Zhiming; Zhou, Pengfei; Shan, Chao; Xiao, Gengfu

The pandemic of COVID-19 caused by SARS-CoV-2 has raised a new challenges to the scientific and industrious fields after over 1-year spread across different countries. The ultimate approach to end the pandemic is the timely application of vaccines to achieve herd immunity. Here, a novel SARS-CoV-2 receptor-binding domain (RBD) homodimer was developed as a SARS-CoV-2 vaccine candidate. Formulated with aluminum adjuvant, RBD dimer elicited strong immune response in both rodents and non-human primates, and protected mice from SARS-CoV-2 challenge with significantly reducing viral load and alleviating pathological injury in the lung. In the non-human primates, the vaccine could prevent majority of the animals from SARS-CoV-2 infection in the respiratory tract and reduce lung damage. In addition, antibodies elicited by this vaccine candidate showed cross-neutralization activities to SARS-CoV-2 variants. Furthermore, with our expression system, we provided a high-yield RBD homodimer vaccine without additional biosafety or special transport device supports. Thus, it may serve as a safe, effective, and low-cost SARS-CoV-2 vaccine candidate.