S-Trimer, a COVID-19 subunit vaccine candidate, induces protective immunity in nonhuman primates

Liang, Joshua G.; Su, Danmei; Song, Tian-Zhang; Zeng, Yilan; Huang, Weijin; Wu, Jinhua; Xu, Rong; Luo, Peiwen; Yang, Xiaofang; Zhang, Xiaodong; Luo, Shuangru; Liang, Ying; Li, Xinglin; Huang, Jiaju; Wang, Qiang; Huang, Xueqin; Xu, Qingsong; Luo, Mei; Huang, Anliang; Luo, Dongxia; Zhao, Chenyan; Yang, Fan; Han, Jian-Bao; Zheng, Yong-Tang; Liang, Peng

SARS-CoV-2 is the underlying cause for the COVID-19 pandemic. Like most enveloped RNA viruses, SARS-CoV-2 uses a homotrimeric surface antigen to gain entry into host cells. Here we describe S-Trimer, a native-like trimeric subunit vaccine candidate for COVID-19 based on Trimer-Tag technology. Immunization of S-Trimer with either AS03 (oil-in-water emulsion) or CpG 1018 (TLR9 agonist) plus alum adjuvants induced high-levels of neutralizing antibodies and Th1-biased cellular immune responses in animal models. Moreover, rhesus macaques immunized with adjuvanted S-Trimer were protected from SARS-CoV-2 challenge compared to vehicle controls, based on clinical observations and reduction of viral loads in lungs. Trimer-Tag may be an important new platform technology for scalable production and rapid development of safe and effective subunit vaccines against current and future emerging RNA viruses.