Evaluating humoral immunogenicity induced by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) DNA vaccine candidates.

(A) The blood samples of vaccinated mice were collected one week after the final vaccination. Sera of vaccinated mice were analyzed for SARS-CoV-2 specific total IgG using ELISA. Each sample was tested in duplicate. (B) The total IgG titers were calculated as EC50 (half maximal effective concentration). P-values were determined using one-way ANOVA with uncorrected Fisher’s LSD test. (C) The IgG subtypes in the sera of vaccinated mice were also analyzed using ELISA. P-values were determined using two-way ANOVA with Tukey’s test. (D) The ratios of IgG2b to IgG1 and IgG2c to IgG1 were calculated. P-values were determined using two-way ANOVA with Tukey’s test. (E) The neutralizing antibody titers in the sera of the vaccinated mice were analyzed via a plaque reduction neutralization test (PRNT) using the SARS-CoV-2 virus. P-values were determined using two-way ANOVA with Tukey’s test. (F) The sera of mice were tested for their neutralization rate using a SARS-CoV-2 surrogate virus neutralization test (sVNT). P-values were determined using one-way ANOVA with Dunnett’s test. * P P P P < 0.0001.