ANTIGENIC DIVERSITY IN THE PERIODONTOPATHOGEN, ACTINOBACILLUS-ACTINOMYCETEMCOMITANS

We have identified a significant level of variation in antibody respon ses to Actinobacillus actinomycetemcomitans outer membrane antigens (O MA). This study was designed to verify A. actinomycetemcomitans antige nic diversity that could contribute to maintaining this chronic infect ion despite the host immune response. A. actinomycetemcomitans strains (5 from different patients and 3 the same patient) were cultured and OMA prepared for Western immunoblotting studies. Antigen bands in the OMA were identified using 7 sera obtained from 3 adult periodontitis ( AP) and 4 localized juvenile periodontitis (WP) patients that were doc umented with elevated A. actinomycetemcomitans antibody and infection. Differences/similarities in the antigen patterns among the A. actinom ycetemcomitans strains were assessed using a kappa similarity coeffici ent. Antigen bands in the A. actinomycetemcomitans strains ranged from 11-150 kDa; however, variation in antigen patterns were noted among t he strains. Utilizing the human sera as probes for antigenic diversity , the 5 heterologous strains showed average K=0.23 (p<0.05), while hom ologous A. actinomycetemcomitans strains had a K=0.48 (p<0.02). The A. actinomycetemcomitans OMA were used as probes to describe variability in host antibody and as such presumptive evidence of antigenic divers ity in A. actinomycetemcomitans that is colonizing each of the patient s. The results showed average K=0.26 (p<0.05) for the patients when te sted against each of the heterologous strains, and K=0.14 when tested against the homologous strains (p > 0.1). Finally, antigen bands of M( r) 80, 65, 58, 31 and 20 kDa were demonstrated as antigens contributin g to the antigenic diversity in A. actinomycetemcomitans.