Inability of intact cells of Treponema denticola to degrade human serum proteins IgA, IgG and albumin.

Treponema denticola has been shown to be associated with periodontitis in man and animals. The organism ferments amino acids and thrives on the proteins in the periodontal pocket. Accordingly, T. denticola possesses various proteolytic enzymes, including a chymotrypsin-like protease, capable of hydrolyzing a whole range of proteins, including immunoglobulins. Yet, it is not clear whether the intact cells of T. denticola can degrade immunoglobulins and albumin. The purpose of this study was to clarify this point. Three strains of T. denticola were cultured in liquid medium, and cells were harvested by centrifugation. Protein degradation in cell suspensions was assayed by capillary electrophoresis and immunonephelometry. None of the T. denticola strains appeared to be able to degrade IgA, IgG, or albumin, while a strain of P. gingivalis completely hydrolyzed these proteins. The findings suggest that, in the periodontal pocket, T. denticola depends on proteinases from other bacteria for utilization of the available serum proteins. This is in accordance with clinical data showing a close relationship between T. denticola and strongly proteolytic bacteria, such as Porphyromonas gingivalis and Bacteroides forsythus.