Major role of S-glycoprotein in providing immunogenicity and protective immunity in mRNA lipid nanoparticle vaccines based on SARS-CoV-2 structural proteins
Recently we have developed an mRNA lipid nanoparticle (mRNA-LNP) platform providing efficient long-term expression of an encoded gene in vivo after both intramuscular and intravenous application. Based on this platform, we have generated mRNA-LNP coding SARS-CoV-2 structural proteins M, N, S from different virus variants and studied their immunogenicity separately or in combinations in vivo. As a result, all candidate vaccine compositions coding S and N proteins induced excellent anti-RBD and N titers of binding antibodies. T cell responses mainly represented specific CD4+ T cell lymphocyte producing IL-2 and TNF-. mRNA-LNP coding M protein did not show high immunogenicity. High neutralizing activity was detected in sera of mice vaccinated with mRNA-LNP coding S protein (alone or in combinations) against closely related strains but was not detectable or significantly lower against an evolutionarily distant variant. Our data showed that the addition of mRNAs encoding S and M antigens to the mRNA-N in the vaccine composition enhanced immunogenicity of mRNA-N inducing more robust immune response to the N protein. Based on our results, we suggested that the S protein plays a key role in enhancement of immune response to the N protein in the mRNA-LNP vaccine.