Investigation and characterization for the periodontopathic bacterial genes specifically expressing in vivo

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Pathogenic bacteria could express specific genes and its proteins under the specific growth condition or especially in vivo, which might be related to bacterial growth and pathogenicity. In this study, we aimed to investigate and characterize such specific genes and proteins of periodontopathic bacteria, Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans expressing in vivo.The major results of this study are as follows:1)P. gingivalis expresses specific 53-kDa outer membrane protein(Ag53) which evokes strong humoral immune responses in evokes strong humoral immune responses in many patients with periodontal disease. Three sequences, RAAIRAS, YYLQ and MSPARR, were identified as major B-cell epitopes in Ag53, which might influence individual differences in antibody titer against Ag53.2)A. actinomycetemcomitans express fimbriae in vivo that plays an important role in the ability of this bacterium to colonize teeth and other surfaces. The flp-1 gene encodes the major fimbriae protein component of A. actinomycetemcomitans. We compared flp-1 DNA sequences from 43 A. actinomycetemcomitans clinical isolates. DNA and predicted protein sequences were highly divergent in the C-terminus of the flp-1 protein that has been shown to be important for the bundling and adhesive properties of the fimbriae, suggesting that these diverse strains carry pathogenic potential.3) Two genes encoding ferritin-like protein were identified in the upstream region of actX from A. actinomycetemcomitans which controls its growth and virulence. Two ferritin genes constituted a bicistronic operon and the accumulation of its mRNA was upregulated under aerobic conditions, suggested that the operon may have important roles in the adaptation of the bacteria to oxidative environmental changes.