Figure 2.
Immunization with mRNA vaccines elicited neutralizing antibodies in mice. (A) Mice immunization schedule. Groups of BALB/c mice were injected i.m. with 10 μg of RBD-WT mRNA (n = 8), RBD-O mRNA (n = 8), or luciferase-mRNA (Ctrl; n = 5) vaccines at weeks 0 and 2. Serum samples were collected from individual mice at weeks 2 and 4. (B) The week-2 and week-4 antisera were diluted 1:100 and analyzed for RBD-WT-binding activity by ELISA. (C) Neutralizing titers of the week-4 antisera samples from each group against WT-, Delta-, and Omicron-PV (pseudovirus). Serum samples that exhibited less than 50% neutralization at the lowest serum dilution (1:200) were assigned a NT50 value of 100 for statistical analysis. Each symbol represents one mouse. (D) Neutralizing titers of the week-4 antisera from RBD-WT mRNA group (left panel) and RBD-O mRNA group (right panel) against SARS-CoV-2 PV. The geometric mean of NT50 values was shown. For panels (B, C), data are presented as mean ± SEM. p values were analyzed with unpaired t-test and indicated as follows: ns, not significant; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.