SHARED ANTIGENS OF PORPHYROMONAS-GINGIVALIS AND BACTEROIDES-FORSYTHUS

Periodontitis in humans is caused by a group of predominantly gram-neg ative, anaerobic bacteria among which Porphyromonas gingivalis and Bac teroides for sythus are prominent. A similar group is present and pres umably plays a similar role in experimental periodontitis in the prima te Macaca fascicular is. Nevertheless, immunization using a vaccine co ntaining only killed P, gingivalis suppresses the progress of experime ntal periodontitis in M. fascicular is. We investigated the hypothesis that gram-negative periodontopathic bacteria may share antigens, and immunization with one species may induce antibodies reactive with othe r gram-negative species. Using enzyme-linked immunosorbent assay (ELIS A), Western and dot immunoblots with nonabsorbed and absorbed and immu ne and preimmune sera we show that monkeys immunized with P. gingivali s produce antibodies reactive not only with antigens of P. gingivalis but also with those of B. forsythus. Similarly, rabbits immunized with P. gingivalis or with B. forsythus produce antibodies that react with antigens of both bacteria. Cross-reactive antibodies bind to epitopes in lipid A and possibly in core carbohydrate of lipopolysaccharide. U sing complexes of lipopolysaccharide with polymyxin B, bovine serum al bumin and apolipoprotein A1 specificity of binding was documented. Usi ng sera from monkeys immunized with P. gingivalis, cross-reactivity wi th Actinobacillus actinomycetemcomitans could not be demonstrated by E LISA, although binding to lipopolysaccharide but not to lipid A was de monstrated by Western and dot immunoblots. Antibodies to shared lipopo lysaccharide epitopes of periodontopathic bacteria may account, at lea st in part, for the immune protection observed in immunized monkeys, a nd shared epitopes may have potential as a vaccine for periodontitis i n humans.