A Monoclonal Antibody to HA2 Inhibits the Growth of P. gingivalis

Objectives: Porphyromonas gingivalis (P. gingivalis) is an important periodontal pathogen that require heme for growth. Gingipain plays a role in erythrocyte agglutinatation and lysis. The hemagglutinin-2 (HA2) is a part of the multi-protein gingipain complexes of K-gingipain (Kgp), R-gingipain A (RgpA), and the cell surface adhesion domains of hemagglutinin A (HagA). The HA2 can bind both heme and hemoglobin. Based on their adhesive properties, these proteins are considered potential candidates for cell-surface heme deposition. The objectives of this study were to prepare an anti-HA2 monoclonal antibody (MAb) and to investigate whether it inhibits the growth of P. gingivalis in vitro.
Methods: Anti-HA2 MAb was prepared using hybridoma technology. In vitro growth inhibition assays were performed in 96-well microtiter plates in the presence or absence of the MAb. Absorbance at 570-nm was used to determine the concentration of P. gingivalis, and viable cells were quantified using flow cytometry.
Results: The anti-HA2 MAb, termed 6G10, inhibited the growth of P. gingivalis compared with an irrelevant MAb or PBS. As little as 50-µg/ml of purified antibody inhibited bacterial growth in the synthetic medium containing hemin. After 18 h of incubation, 6G10 inhibited the growth of P. gingivalis by 10.55% compared with the irrelevant MAb as assessed using a microplate reader, while quantitation of live cells by flow cytometry showed a reductions of 47.05%.
Conclusions: These results showed that the anti-HA2 MAb 6G10 inhibits P. gingivalis growth and may be useful in the treatment of periodontal disease.