Pathogenicity of dentilisin from Treponema denticola

Objectives: Treponema denticola is frequently isolated from lesions occurring in chronic periodontitis, along with Porphyromonas gingivalis and Tannerella forsythia. These microorganisms have all been implicated in the progression of this disease, and are also potentially associated with systemic diseases such as atherosclerosis. T. denticola has a prolyl-phenylalanine-specific protease, dentilisin,on its surface and this protease is thought to be a major pathogen of this microorganism. Therefore, to evaluate the pathogenicity of this protease to periodontal tissue, we studied its role in the colonization of gingival crevices and invasion of host tissue, and examined its effect on the immune responses and formation of abscesses. Methods: A dentilisin-deficient mutant was constructed following electroporation with a prtP-inactivated DNA fragment. Coaggregation activity between T. denticola and T. forsythia was evaluated by the method of Nagata et al. (J. Dent. Res. 69, 1990). Ability of invasion was evaluated by the method of Dorn et al. (Infect. Immun. 67, 1999). Induction of cytokine production was evaluated by ELISA. To evaluate its abscess-forming activity, 3x10⁹ cells of T. denticola were subcutaneously injected into Balb/c mice. Results: Dentilisin-deficient mutant lost its prolyl-phenylaranine specific protease. Its coaggregation reaction with T. forsythia was attenuated compared with that of the wild type strain. The invasion assay indicated that T. denticola wild type was able to invade human umbilical endothelial cells, but that the dentilisin-deficient mutant was not. Invasion was inhibited by cytokaracin B. Similar to other periodontopathic bacteria, T. denticola induces proinflammatory cytokines, although here IL-2 and IL-6 were hydrolyzed by dentilisin. Abscess forming activity following subcutaneous injection of live T. denticola was attenuated in the dentilisin-deficient mutant compared with in the wild type strain. Conclusion: Its effects on coaggregation, downregulation of the immunoresponses, and formation of abscesses show that dentilisin plays a key role in the pathogenicity of T. denticola.