Fig. 2: Humoral immune responses after the first and second vaccinations.

NP- and GP38-specific IgM (A, F) and IgG (B, G) responses after the first and second vaccinations were determined as endpoint titers in plasma samples. Anti-NP C and anti-GP38 H IgG1 and IgG2c titers were determined as endpoint titers in plasma samples. The IgG1 to IgG2c ratios were determined by dividing the endpoint titers of IgG1 to IgG2 of individual animals and presented in D for anti-NP antibodies and in I for anti-GP38 antibodies. The dotted horizontal line represents IgG1 to IgG2c ratio = 1. The avidity indices of anti-NP E and anti-GP38 J antibodies from vaccinated animals after the first and second vaccinations were determined. For the avidity of IgG antibodies, areas under the curves (AUC) of 7-point dilutions of urea-treated and untreated samples were determined and the avidity index calculated as follows: (AUC of the urea-treated sample/AUC of untreated sample) × 100. Each dot represents the mean value of the replicates from each animal and the horizontal line represents the median value for the group. All samples were tested in duplicate. Two-tailed nonparametric t tests and ordinary one-way ANOVA (*p < 0.05; **p < 0.001; ***p < 0.0003) were used for statistical analyses when applicable. Statistical analyses compared IgM and IgG titers from each vaccine group with those of the mock-vaccinated animals at corresponding timepoints. For IgG subclasses, statistical analyses compared IgG1 and IgG2 titers of individual vaccine groups after the first and second vaccination. For IgG avidity determination, statistical analyses were performed with IgG titers after first and second vaccinations.