Preclinical Study of DNA Vaccines Targeting SARS-CoV-2 (preprint)

ABSTRACT

As potential pandemic vaccines, DNA/RNA vaccines, viral vector vaccines and protein-based vaccines have been rapidly developed to prevent pandemic spread worldwide. In this study, we designed plasmid DNA vaccine targeting the SARS-CoV-2 Spike glycoprotein (S protein) as pandemic vaccine, and the humoral, cellular, and functional immune responses were characterized to support proceeding to initial human clinical trials. After intramuscular injection of DNA vaccine encoding S protein with alum adjuvant (three times at 2-week intervals), the humoral immunoreaction, as assessed by anti-S protein or anti-receptor-binding domain (RBD) antibody titers, and the cellular immunoreaction, as assessed by antigen-induced IFNγ expression, were up-regulated. In IgG subclass analysis, IgG2b was induced as the main subclass. Based on these analyses, DNA vaccine with alum adjuvant preferentially induced Th1-type T cell polarization. We confirmed the neutralizing action of DNA vaccine-induced antibodies by a binding assay of RBD recombinant protein with angiotensin-converting enzyme 2 (ACE2), a receptor of SARSCoV-2, and pseudo-virus assay, TCID assay with live SARS-CoV-2. Further B cell epitope mapping analysis using a peptide array showed that most vaccine-induced antibodies recognized the S2 and RBD subunits. Finally, DNA vaccine protected hamsters form SARSCoV-2 infection. In conclusion, DNA vaccine targeting the spike glycoprotein of SARS-CoV-2 might be an effective and safe approach to combat the COVID-19 pandemic.Funding: This study was supported by Project Promoting Support for Drug Discovery grants(JP20nk0101602 and JP21nf0101623h102) from the Japan Agency for Medical Research andDevelopment and Panasonic Co. (Japan). To fight against the worldwide COVID-19 pandemic, the development of an effective and safe The Department of Health Development and Medicine is an endowed department supported by Anges, Daicel, and FunPep. The Department of Clinical Gene Therapy is financially supported by Novartis, AnGes, Shionogi, Boeringher, Fancl, Saisei Mirai Clinics, Rohto and Funpep. Declaration of Interest R.M. is a stockholder of FunPep and Anges. T.O. T.K. and Y.S. are employees of Anges. R.I, A.T, H.K, S.K, E.T, S.M, and H.T are employees of FunPep. R.M, H.T, and A.T. are FunPep stockholders. All other authors declare no competing interests.Ethical Approval All experiments were approved by the Ethical Committee for Animal Experiments of the Osaka University Graduate School of Medicine.