Heterogeneity of Porphyromonas gingivalis strains in the induction of alveolar bone loss in mice

These experiments examine alveolar bone loss in a model in which specific p athogen-free mice are exposed orally with Porphyromonas gingivalis. Alveola r bone loss was induced as a result of a specific infection with P. gingiva lis, rather than other environmental antigens. Infection with live P. gingi valis was required, as significant bone loss did not follow gavage with for malin-killed P. gingivalis. The virulence of different strains of P. gingiv alis was compared. Two laboratory strains of the bacteria (ATCC 53977 and W 50) and a mutant strain lacking the 43-kDa fimbrillin (strain DPG3) induced bone loss. P. gingivalis 381, however, did not induce bone loss. There was a strong immunoglobulin G (IgG) antibody response to infection with each s train but a significant serum IgA response only to strain 381. These studie s show that in mice with a background oral microflora bone loss is induced by a specific infection with P. gingivalis and that bacterial strain variat ion is important in determining whether alveolar bone loss will ensue.