Strain-dependent activation of the mouse immune response is correlated with Porphyromonas gingivalis-induced experimental periodontitis

P>Aims To evaluate the effect of oral infection with three Porphyromonas gingivalis strains on alveolar bone loss (ABL) and its correlation with the mouse immune response. Materials and Methods Mice were orally infected with P. gingivalis strains 381, 33277 and 53977. After 42 days, maxillae were analysed for ABL using micro-computed tomography and the serum for anti-P.gingivalis IgG1 and IgG2a levels. The cytokine response to P. gingivalis was tested using the subcutaneous chamber model. Results The P. gingivalis 53977-infected group showed the highest ABL, which was significantly different from all other groups (p < 0.001). In addition, the humoral response to P. gingivalis 53977 was significantly lower than the response to P. gingivalis 381 and 33277 (p <= 0.01). The IgG2a/IgG1 ratio was higher in the P. gingivalis 33277-infected group (1.6) compared with the P. gingivalis 381-infected group (0.51). Four days post-infection, interleukin (IL)-1 beta levels remained significantly higher in the P. gingivalis 53977-infected group only (1198.2 +/- 260.0, p < 0.05), while IL-4 levels remained significantly higher in the P. gingivalis 381-infected group (265.8 +/- 131.6, p < 0.05). Conclusions The high levels of ABL induced by P. gingivalis 53977 were inversely correlated with the humoral response to this bacterium. In addition, ABL was correlated with an elevated pro-inflammatory response.