Identification of dominant immunogenic bacteria and bacterial proteins in periodontitis

Marginal periodontitis is considered an infectious disease that triggers host inflammatory responses resulting in destruction of the periodontium. A complex biofilm of bacteria is associated with periodontitis. Some species have been identified as putative pathogens such as Porphyromonas gingivalis (P.g) and Actinobacillus actinomycetemcomitans (A.a), but the identity of dominate immunogens of these bacteria is poorly elucidated. The aim of the study was to identify dominant immunogenic proteins of P.g and A.a in patients suffering from chronic and aggressive periodontitis by proteomic analysis. 2-dimensional gel electroforesis of outer membrane and secreted proteins from P.g strain W83, A.a strain HK1651, and Streptococcus gordonii strain SK7 was performed. The gels were blotted onto membranes and immunogens were detected by incubation with sera collected from patients, healthy controls, and immunized rabbits followed by development with fluorescently labeled anti-IgG. The detected immunogens were extracted from gels run in parallel and subjected to mass spectrometric analysis and identified (ongoing) with reference to genome sequences from the target strains. It is expected that we will be able to identify immunodominant proteins and potentially important virulence factors of putative periodontal pathogens.