Fig. 3

RBD-specific IgG binding and neutralizing antibodies in sera of naïve mice immunized by WT and variant RBD mRNA vaccines. A Immunization and blood draw schedule. B Serum IgG binding to recombinant SARS-CoV-2 RBD of WT, Beta, Delta, and Omicron strain measured by ELISA. Plotted values represent mean endpoint titers. Fold change between groups with statistically significance were shown after asterisks. C Serum neutralizing activity against SARS-CoV-2 D614G, Beta, Delta, and Omicron pseudovirus measured by pseudovirus neutralization assay. Plotted values represent geometric mean of 50% neutralizing titers (NT₅₀). Fold change between groups with statistically significance were shown after asterisks. Statistical comparisons across groups were determined by one-way ANOVA with Tukey’s multiple comparisons test. *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001. Dotted line indicates the limit of detection. See also Additional file 1: Fig. S3