Potent In Vitro and In Vivo Activity of Plantibody Specific for Porphyromonas gingivalis FimA

Fimbrial protein fimbrillin (FimA), a major structural subunit ofPorphyromonas gingivalis , has been suggested as a vaccine candidate to controlP. gingivalis -induced periodontal disease. Previously, cDNAs encoding IgG monoclonal antibodies (MAbs) against purified FimA fromP. gingivalis 2561 have been cloned, and the MAbs have been produced in rice cell suspension. Here we examined the biological activities of the plant-produced MAb specific for FimA (anti-FimA plantibody) ofP. gingivalis in vitro andin vivo . The anti-FimA plantibody recognized oligomeric/polymeric forms of native FimA in immunoblot analysis and showed high affinity for native FimA (KD = 0.11 nM). Binding ofP. gingivalis (108 cells) to 2 mg of saliva-coated hydroxyapatite beads was reduced by 53.8% in the presence of 1 μg/ml plantibody. Anti-FimA plantibody (10 μg/ml) reduced invasion of periodontal ligament cells byP. gingivalis (multiplicity of infection, 100) by 68.3%. Intracellular killing ofP. gingivalis opsonized with the anti-FimA plantibody by mouse macrophages was significantly increased (77.1%) compared to killing of bacterial cells with irrelevant IgG (36.7%). In a mouse subcutaneous chamber model, the number of recoverableP. gingivalis cells from the chamber fluid was significantly reduced when the numbers of bacterial cells opsonized with anti-FimA plantibody were compared with the numbers of bacterial cells with irrelevant IgG, 66.7% and 37.1%, respectively. Thesein vitro andin vivo effects of anti-FimA plantibody were comparable to those of the parental MAb. Further studies withP. gingivalis strains with different types of fimbriae are needed to investigate the usefulness of anti-FimA plantibody for passive immunization to controlP. gingivalis -induced periodontal disease.