Design and Immunogenicity of SARS-CoV-2 DNA vaccine encoding RBD-PVXCP fusion protein

The potential of immune evasive mutations accumulation of the SARS-CoV-2 virus has led to its rapid spread causing over 600 million confirmed cases and more than 6.5 million confirmed deaths. Huge demand for the rapid development and deployment of low-cost and effective vaccines against emerging variants renews interest in DNA vaccine technology. Here we report a rapid generation and immunological evaluation of novel DNA vaccine candidates against Wuhan-Hu-1 and Omicron variants, based on the RBD protein fused with the Potato virus X coat protein (PVXCP). Delivery of DNA vaccines using electroporation in a two-doses regimen induced high antibody titers and profound cellular response in mice. Antibody titers induced against Omicron variant of the vaccine were sufficient for the effective protection against both the Omicron and Wuhan-Hu-1 virus infections. PVXCP protein in the vaccine construct shifted immune response to the favorable Th1-like type and provided oligomerization of RBD-PVXCP protein. A naked DNA delivery by the needle-free injection device allowed us to achieve antibody titers comparable with the mRNA-LNP delivery in rabbits. This data identifies the RBD-PVXCP DNA vaccine platform as a promising solution for robust and effective SARS-CoV-2 protection, supporting further translational study.