Cleavage of human immunoglobulin G by Treponema denticola

Mechanisms by which microbial proteases may counteract the local host immun e system include the degradation of immunoglobulins. In this study, we repo rt the capacity of the periodontopathogen Treponema denticola to degrade im munoglobulin G (IgG). Intact IgG was not hydrolysed by whole cells, as reve aled by SDS-PAGE analysis. When IgG molecules were treated with endoglycosi dase F to remove the carbohydrate moiety, significant degradation was obser ved. However, pre-treatment with glycosidases possessing specificities diff erent from endoglycosidase F (lysozyme or neuraminidase) did not render the molecule susceptible to cleavage by T. denticola. SDS-PAGE analysis of the IgG degradation products suggests that T. denticola cleaves inside the hea vy chain polypeptide. Serine-specific protease inhibitors were highly effec tive in inhibiting the degradation of glycosidase-treated IgG molecules by T. denticola. The synergistic effect of glycolytic enzymes and T. denticola proteases on IgG may occur during periodontitis since both glycolytic acti vities and spirochete numbers significantly increase in diseased periodonta l sites. (C) 2001 Academic Press.