Figure 1. Induction of P. gingivalis-specific serum IgG and salivary sIgA antibodies in mice immunized with rgpA DNA vaccine via abdominal skin by Gene Gun (2.5 µg/mouse) and mice immunized nasally with the rgpA-HVJ envelope vector (20 µg/mouse). rgpA DNA vaccine was injected a total of 7 times as indicated by arrows. (A) Serum IgG titers of mice against sonicates of P. gingivalis were determined on days 0, 7, 14, 28, 35, 42, and 49 after primary immunization (N = 15). Serial dilutions were used to measure endpoint titers (> 0.15). Results are means ± standard deviations of log₂ ELISA antibody titers. Variation in endpoint titers was within a two-fold serial dilution. *p < 0.01, against naïve mice; **p < 0.01 against Gene Gun-immunized mice by one-way ANOVA, followed by the Student-Newman-Keuls test. (B) Salivary sIgA titers against sonicates of P. gingivalis were determined on days 0, 7, 14, 28, 35, 42, and 49 after primary immunization. Serial dilutions were used to measure endpoint titers (> 0.15). Results are means ± standard deviations of log₂ ELISA antibody titers (N = 15). Variation in endpoint titer was within a two-fold serial dilution. *p < 0.01 against naïve mice and Gene Gun-immunized mice by one-way ANOVA, followed by the Student-Newman-Keuls test.