Immunogenicity of a multivalent protein subunit vaccine based on non-glycosylated RBD antigens of SARS-cov-2 and its variants.

COVID-19 infections continue due to accessibility barriers to vaccines and the emergence of SARS-CoV-2 variants. An effective, safe, accessible, and broad-spectrum vaccine is still needed to control the disease. We developed a multivalent protein subunit vaccine comprising antigens designed from a non-N-glycosylated region of the receptor-binding domain of the spike protein of SARS-CoV-2. We combined a previously developed antigen based on the Wuhan original viral strain, and a site-mutated antigen based on several variants including Alpha, Beta, Gamma, Eta, Iota, Theta, Zeta, Mu and Omicron. The recombinant antigens were expressed in a prokaryotic system and the immunogenicity of the multivalent vaccine was tested in a mouse model. The evaluation of the subunit vaccine candidate, incorporating different variant-based multivalent recombinant antigens from non-glycosylated regions of the RBD, demonstrated a favorable safety profile, significant immunogenicity, and potent neutralizing activity, collectively supporting its potential efficacy and safety for further development.