Cell surface polysaccharide and protein antigens of an encapsulated Porphyromonas gingivalis 16-1 strain.

We have extracted the cell surface polysaccharide antigen (PS) and protein antigen from an encapsulated and virulent strain of Porphyromonas gingivalis 16-1. The PS was separated from lipopolysaccharide (LPS) by Sephacryl S-300 gel chromatography. It was distinguished from LPS by immunodiffusion with homologous rabbit antiserum. The PS reacted specifically with serogroup b antiserum against P. gingivalis 16-1 and Su63 strains, but not with antisera against serogroup a (ATCC 33277) or serogroup c (W83). The outer membrane protein was extracted with the Zwittergent 3-16 and sarcosyl detergents in a Tris-EDTA buffer. SDS-Page analysis revealed that the extracted protein antigen of P. gingivalis 16-1 contained 2 immunodominant proteins with molecular weights of 41 KDa and 27 KDa.