Induction of immune responses and prevention of alveolar bone loss by intranasal administration S of mice with Porphyromona gingivanlis fimbriae and recombinant cholera toxin B subunit

Introduction: Adult periodontitis is initiated by specific periodontal pathogens represented by Porphyromonas gingivalis; however, an effective measure for preventing the disease has not yet been established. In this study, the effectiveness of a vaccine composed of fimbriae of P. gingivalis and recombinant cholera toxin B subunit (rCTB) was evaluated using BALB/c mice. Methods: Fimbriae and rCTB were co-administered intranasally to BALB/c mice on days 0, 143 21, and 28. On day 35, mice were sacrificed to determine immunoglobulin levels in serum, saliva, and nasal and lung extracts by enzyme-linked immunosorbent assay. The prevention effect of the vaccine on P. gingivalis-induced periodontitis in mice was evaluated by measuring alveolar bone loss. Results: The rCTB significantly increased serum immunoglobulin (Ig)A levels when mice were administered with a minimal amount (0.5 mu g) of the fimbrial antigen. The adjuvant effect on serum IgG production was indistinct because the minimal amount of the antigen still induced a large amount of IgG. In contrast to systemic responses, a fimbria-specific secretory IgA response was strongly induced by co-administration of rCTB and 0.5 mu g fimbriae, the same amount of the antigen alone scarcely induced a response. Histopathological examination revealed IgA-positive plasma cells in the nasal mucosal tissue but no observable mast cells in the area. In addition, nasal administration of the fimbrial vaccine significantly protected the mice from R gingivalis-mediated alveolar bone loss. Conclusion: Nasal vaccination with a combination of fimbriae and rCTB can be an effective means of preventing P gingivalis-mediated periodontitis.