Characterization of the gene encoding 200-kDa Porphyromonas gingivalis protein that reacts to sera from periodontitis patients.

Porphyromonas gingivalis, a Gram-negative anaerobic bacterium, is considered to be one of the major etiologic agents of adult periodontitis. We previously succeeded in molecular cloning of a 200-kDa antigenic protein (200-k AP) from P. gingivalis 381 by immunoscreening using sera from severe periodontitis patients and designated it as pMD101. We also identified amino acid sequences of the short peptide from a lysyl endopeptidase digested recombinant (r), 200-k AP, and found that the short peptide had exactly the same amino acid sequence as the hemagglutinin A (hagA) of P. gingivalis, which is thought to have potential use in a vaccine against periodontitis. In this study, we attempted to confirm whether 200-k AP was a molecule identical to hagA. DNA sequences of pMD157, a subclone encoding the 25-kDa antigenic region of pMD101, were identical to the same part of the hagA gene. The r200-k AP was purified for homogeneity and rabbits were immunized with it. The antibody against r200-k AP previously showed a similar Western-blot pattern as P. gingivalis lysate by monoclonal antibodies against hagA by literature and reacted to r130-kDa hemagglutinin. These findings suggest that 200-k AP is identical to hagA and that r200-k AP may be useful as an immunotherapy agent against periodontitis caused by P. gingivalis infection.