title: Complement-mediated killing of porphyromonas gingivalis 381 by the immunoglobulin G induced by recombinant 40-kDa outer membrane protein.
abstract: Porphyromonas gingivalis has been implicated as an important pathogen in severe adult periodontitis. We have previously cloned a 40-kDa outer membrane protein from P. gingivalis 381 and succeeded in producing sufficient quantities of the recombinant protein (r40-kDa OMP). r40-kDa OMP has been the subject of considerable interest to us as a possible vaccine candidate. To understand the role of anti-r40-kDa OMP antibody in the host defense mechanisms against P. gingivalis, we examined the involvement of a rabbit antibody against r40-kDa OMP (r40-kDa OMP Ab) to an in vitro complement-mediated bactericidal assay for P. gingivalis 381. By measuring the absorbance values in order to assay the surviving bacteria, we found significant anti-P. gingivalis activity of r40-kDa OMP Ab when guinea pig complement was present. Using affinity-purified immunoglobulin G of r40-kDa OMP Ab (IgG-r40-kDa OMP), we demonstrated that the IgG contributed to anti-P. gingivalis activity in the antibody-complement system. This was effected by measuring the incorporation of tritiated thymidine into newly synthesized nucleic acids. Finally, we confirmed the cell lysis of P. gingivalis 381 exposed to IgG-r40-kDa OMP in the presence of complement sources in a radioactive bactericidal assay using bacteria labeled with [14C]sodium acetate. Assembling the data from experiments using component-deficient complements, we concluded that IgG-r40-kDa OMP was related to the killing of P. gingivalis 381 by mediation in the complement activated through both the classical and the alternative pathways.
authors.affiliation: Department of Biochemistry, Nihon University School of Dentistry at Matsudo, Matsudo, Chiba, 271, Japan.
authors.forename: S
authors.initials: S
authors.lastname: Saito
authors.forename: M
authors.initials: M
authors.lastname: Hayakawa
authors.forename: K
authors.initials: K
authors.lastname: Hiratsuka
authors.forename: H
authors.initials: H
authors.lastname: Takiguchi
authors.forename: Y
authors.initials: Y
authors.lastname: Abiko
mesh_terms: D000818:Animals; D001425:Bacterial Outer Membrane Proteins / Q000276:immunology*; D002250:Carbon Radioisotopes; D002846:Chromatography, Affinity; D003167:Complement Activation; D006168:Guinea Pigs; D007106:Immune Sera; D007074:Immunoglobulin G / Q000302:isolation & purification / Q000494:pharmacology*; D009696:Nucleic Acids / Q000096:biosynthesis; D016966:Porphyromonas gingivalis / Q000276:immunology* / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000276:immunology; D019346:Sodium Acetate / Q000378:metabolism; D013936:Thymidine / Q000378:metabolism; D014316:Tritium
chemical_list: D001425:Bacterial Outer Membrane Proteins; D002250:Carbon Radioisotopes; D007106:Immune Sera; D007074:Immunoglobulin G; D009696:Nucleic Acids; D011994:Recombinant Proteins; D014316:Tritium; D019346:Sodium Acetate; D013936:Thymidine