HGP44 induces protection against Porphyromonas gingivalis-Induced alveolar bone loss in mice

Abstract

The protective effect of DNA vaccines expressing the Arg-gingipain A domain against bone loss induced by Porphyromonas gingivalis infection was investigated in a murine model. phgp44, which expresses the 44-kDa adhesion/hemagglutinin domain of Arg-gingipain A, prevented P. gingivalis-induced alveolar bone loss. The results indicate that phgp44 could be a candidate antigen for a vaccine against P. gingivalis infection.

Fig. 1.

Map of cloned rgpA in the rgpA DNA vaccine and primers used to construct the rgpA domain DNA vaccines. Small arrows below the map indicate the locations of primers used in this study. Large arrows indicate fragments expressed by the DNA vaccines.

Fig. 2.

(A) Induction of P. gingivalis-specific IgGs in mice immunized with rgpA domain DNA vaccines. Titers of IgG against sonicates of P. gingivalis in sera from mice were determined on day 42 after primary immunization, and endpoint titers were evaluated by measuring serially diluted sera. Results represent means ± standard deviations for log₂ ELISA antibody titers. *, P < 0.05 by one-way ANOVA for comparison with mice immunized with pVAX1. (B) Immunoblot analysis with sera from mice immunized with the rgpA DNA vaccine or phgp44. Sonicates of P. gingivalis were separated by SDS-PAGE and transferred to polyvinylidene difluoride (PVDF) membranes. Blotted membranes were immunostained using sera from mice immunized with the rgpA DNA vaccine or phgp44. Lanes 1 and 3, molecular size markers; lane 2, sera from mice immunized with the rgpA DNA vaccine; and lane 4, sera from mice immunized with phgp44. Molecular mass markers are shown in kilodaltons.

Fig. 3.

Levels of alveolar bone loss elicited following P. gingivalis oral challenge after immunization with the rgpA domain DNA vaccine. BALB/c mice were immunized with rgpA DNA or rgpA domain DNA vaccines. The control groups consisted of age-matched, nonvaccinated mice and pVAX1-immunized mice. After immunization, mice were orally challenged with P. gingivalis ATCC 33277. At 42 days after oral challenge, all mice were sacrificed. *, P < 0.05 by one-way ANOVA for comparison with mice infected by P. gingivalis without immunization. §, P < 0.05 by one-way ANOVA for comparison with mice infected by P. gingivalis and immunized with pVAX1.

Fig. 4.

(A) Induction of P. gingivalis-specific IgGs in mice immunized with rgpA domain DNA vaccines. Titers of IgG against sonicates of P. gingivalis in sera from mice were determined on day 43 after primary immunization, and endpoint titers were evaluated by measuring serially diluted sera. Results represent means ± standard deviations for log₂ ELISA antibody titers. *, P < 0.05 by one-way ANOVA for comparison with mice immunized with pVAX1. (B) Levels of alveolar bone loss elicited following P. gingivalis oral challenge after immunization with the phgp44 derivative. BALB/c mice were immunized with rgpA DNA or rgpA domain DNA vaccines. The control groups consisted of age-matched, nonvaccinated mice and pVAX1-immunized mice. After immunization, mice were orally challenged with P. gingivalis ATCC 33277. At 42 days after oral challenge, all mice were sacrificed. *, P < 0.05 by one-way ANOVA for comparison with mice infected by P. gingivalis without immunization. §, P < 0.05 by one-way ANOVA for comparison with mice infected by P. gingivalis and immunized with pVAX1.