K-antigens in Porphyromonas gingivalis are associated with virulence.
We investigated antigens in spreading and non-spreading Porphyromonas gingivalis strains. On the basis of differences in virulence in the mouse model, 8 strains were selected for antiserum production in rabbits. Hyperimmune sera were tested by double immunoprecipitation and immunoelectrophoresis. Besides a common antigen, differences in antigenic composition were observed in the thermolabile antigens between all strains tested. Two different heat-stable antigens were found after heating at 120 degrees C. One such antigen was detected after sonication of the pellet fraction of autoclaved P. gingivalis cells. This antigen cross-reacted with 6 of the 8 immune sera. This somatic antigen was almost neutrally charged and sensitive to sodium periodate treatment, suggestive of lipopolysaccharide. A second heat-stable antigen was detected in the supernatant of autoclaved strains of W83, W50, HG184 and A7A1-28. These non-somatic antigens were strain-specific, i.e., no cross-reactivity was found with heterologous hyperimmune sera. An exception was strain W50, which had a non-somatic heat-stable antigen which was recognized by W83 antiserum. These antigens were resistant to DNAse, RNAse and proteinase-K treatment but were degraded by sodium periodate. In immunoelectrophoresis, these antigens appeared to be negatively charged. These properties are characteristics of a K-antigen, which likely represent a thermostable carbohydrate capsule. The presence of K-antigen correlates very well with the serum resistance, the low chemiluminescence, the resistance to phagocytosis and the need for opsonization with specific antibodies for complement-mediated killing of virulent P. gingivalis strains.(ABSTRACT TRUNCATED AT 250 WORDS)
van Winkelhoff
A J
AJ
Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam (ACTA), The Netherlands.
Appelmelk
B J
BJ
Kippuw
N
N
de Graaff
J
J
D000818:Animals; D000942:Antigens, Bacterial / Q000276:immunology*; D000954:Antigens, Surface / Q000276:immunology*; D006801:Humans; D005779:Immunodiffusion; D007122:Immunoelectrophoresis; D010518:Periodontitis / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000145:classification / Q000276:immunology* / Q000472:pathogenicity*; D011817:Rabbits; D012703:Serotyping / Q000379:methods; D014774:Virulence
D000942:Antigens, Bacterial; D000954:Antigens, Surface; C030659:K antigens