Common antigens of Treponema denticola: chemical, physical, and serological characterization.

A sodium deoxycholate-ethanol extractable antigen (DES-Ag) was obtained from four serotypes of Treponema denticola and characterized by chemical, physical, and serological procedures. The cross-reactivity of these antigens was demonstrated by indirect microhemagglutination, immunodiffusion, and immunoelectrophoresis with hyperimmune rabbit antiserum against each of the T. denticola serotypes. Antiserum against two nonoral treponemes, T. phagedenis biotype Reieter and T. pallidum Nichols strain, did not cross-react with the DES-Ag of T. denticola. Chemical analysis of the DES-Ag indicated that proteins (84%) and hexoses (12%) accounted for 96% of the total dry weight of the antigen. Trace amounts of N-acetylglucosamine (0.6%) were also detected. Fatty acids, including palmitic, oleic, and stearic, were identified by gas-liquid chromatography. Polyacrylamide gel electrophoresis of the DES-Ag of each serotype revealed the presence of two bands. The molecular weights of the bands were estimated to be 58,000 and 31,000 by comparing the electrophoretic mobility of the DES-Ag to that of five protein standards of known molecular weights. Although only a single precipitin line was observed by immunodiffusion when each antigen was reacted against its homologous antiserum, two precipitin lines were evident by immunoelectrophoresis. Antiserum against the DES-Ag of T. denticola was shown to agglutinate whole cells of the homologous serotype. Adsorption of this anti-DES-Ag serum with whole cells of T. denticola resulted in the elimination of precipitating antibodies to the DES-Ag by immunodiffusion. It is concluded that the DES-Ag is a component of the outer sheath of T. denticola.