P.gingivalis-Induced Bone Loss in Mice Inversely-Correlates with Serum Antibody Levels

Background: The periopathogen Porphyromonas gingivalis was found to induce experimental alveolar bone loss in mice. However, heterogeneity between P. gingivalis strains may influence its virulence and ability to induce alveolar bone loss. Objectives: The present study was designed to test the ability of different strains of P. gingivalis to induce alveolar bone loss in mice and to correlate it with levels of specific serum antibodies. Methods: BALB/c mice were orally infected with three different strains of P. gingivalis (33277, 381, 53977). 42 days after oral infection, mice were sacrificed, the maxilla of each animal was harvested and blood was collected. Volumetric alveolar bone levels were measured using a novel micro-computed tomography (micro-CT) technique and specific serum antibody titers to P. gingivalis were determined by ELISA. Data was analyzed using one-way ANOVA. Results: The 3 strains of P. gingivalis induced significant alveolar bone loss compared to control non-infected group. Strain 53977 showed the highest levels of bone loss, 33277 moderate levels, and 381 showed the lowest levels. P. gingivalis-specific serum IgG titers were found in all infected group. The specific antibody levels were followed an inverted pattern of the bone loss levels: the highest levels were found in 381-infected mice, while the lowest levels were found in the 53977-infected group. Conclusions: The present study demonstrated the high value of the novel micro-CT technique for assessment of alveolar bone loss in mice. The data demonstrated that different strains of P. gingivalis varied in their ability to induce alveolar bone loss. The inverted correlation may explain the difference in virulence between the different strains, and may be due to the ability of specific strain to evade the immune system.