CoVac501, a self-adjuvanting peptide vaccine conjugated with TLR7 agonists, against SARS-CoV-2 induces protective immunity

Long, Yiru; Sun, Jianhua; Liu, Tingting; Tang, Feng; Zhang, Xinxin; Qin, Qiuping; Miao, Yunqiu; Zhu, Weiliang; Pan, Xiaoyan; An, Qi; Qin, Mian; Tong, Xiankun; Peng, Xionghua; Yu, Pan; Zhu, Peng; Zhang, Yachun; Zhang, Leike; Xiao, Gengfu; Zuo, Jianping; Tang, Wei; Zhou, Ji; Xu, Zhijian; Gan, Yong; Ren, Jin; Huang, Wei; Jin, Guangyi; Gong, Likun

Safe, economical and effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) are needed to achieve adequate herd immunity and halt the pandemic. We have constructed a novel SARS-CoV-2 vaccine, CoVac501, which is a self-adjuvanting peptide vaccine conjugated with Toll-like receptor 7 (TLR7) agonists. The vaccine contains two immunodominant peptides screened from receptor-binding domain (RBD) and is fully chemically synthesized. And the vaccine has optimized nanoemulsion formulation, outstanding stability and safety. In non-human primates (NHPs), CoVac501 elicited high and persistent titers of RBD-specific and protective neutralizing antibodies (NAbs), which were also effective to RBD mutations. CoVac501 was found to elicit the increase of memory T cells, antigen-specific CD8+ T cell responses and Th1-biased CD4+ T cell immune responses in NHPs. More importantly, the sera from the immunized NHPs can prevent infection of live SARS-CoV-2 in vitro. One-Sentence Summary A novel SARS-CoV-2 vaccine we developed, CoVac501, which is a fully chemically synthesized and self-adjuvanting peptides conjugated with TLR7 agonists, can induce high-efficient humoral and cellular immune responses against SARS-CoV-2.