Dominant cross-reactive antibodies generated during the response to a variety of oral bacterial species detect phosphorylcholine

The intraperitoneal immunization of Balb/c mice with subgingival plaque fro m advanced periodontal pockets or with certain strains of Actinobacillus ac tinomycetemcomitans, Fusobacterium nucleatum, Actinomyces israelii, Strepto coccus mitis, or Streptococcus oralis yielded frequently indistinguishable IgM monoclonal antibodies which were reactive with antigens from a variety of oral bacteria. This study aimed to characterize the specificity of such monoclonal antibodies and the diversity of oral bacteria expressing this ta rget antigen or epitope. Using a competitive enzyme-linked immunosorbent as say to study a variety of competitor substances for their capacity to bind to the monoclonal antibodies, we identified phosphorylcholine as the recogn ized epitope. The concentration of positive bacteria with extraordinarily b right cell wall fluorescence in indirect immunofluorescence assays varied b etween 0.1% and 15% in subgingival and from 10 to 40% in supragingival plaq ue samples. Labeled bacteria belonged to different morphotypes, including c occi, rods, and filaments. Of 75 species tested in vitro, 14 Gram-positive and four Gramnegative species were found to harbor positive strains. Haemop hilus aphrophilus, Streptococcus mitis, Actinomyces georgiae, Actinomyces g erencseriae, Actinomyces israelii, and Actinomyces odontolyticus were human oral species of which all tested strains were capable of binding the cross -reactive monoclonal antibodies. In contrast, Actinomyces naeslundii was co nsistently negative. These data provide evidence for a much more common exp ression of phosphorylcholine by oral bacteria than hitherto believed but do not indicate an obvious association of phosphorylcholine expression with o ral health or inflammatory periodontal diseases.