Porphyromonas gingivalis-induced Platelet Aggregation in Human Plasma

The periodontal pathogen Porphyromonas gingivalis has the ability to aggregate human platelets. In this study, the mechanism of P. gingivalis-induced platelet aggregation in platelet-rich plasma (PRP) was investigated. Proteinase inhibitors toward Arg- and Lys-specific gingipain (Rgp and Kgp) did not suppress P. gingivalis-induced platelet aggregation in PRP and it was found that proteolytic activity of gingipains did not contribute to P. gingivalis-induced platelet aggregation in plasma. The study using mutant strains revealed that P. gingivalis-induced platelet aggregation in PRP depended on Rgp-, Kgp- and hemagglutinin A (HagA) -encoding genes that intragenically coded for adhesin Hgp44. Hgp44 adhesin on the bacterial cell surface, which was processed by Rgp and Kgp proteinases, was essential for P. gingivalis-induced platelet aggregation in PRP P. gingivalis cell-reactive IgG in plasma, and FcyRIIa receptor and to a lesser extent GP Ibα receptor on platelets were found to be essential for P. gingivalis-induced platelet aggregation in PRP These results reveal a novel mechanism of platelet aggregation by P. gingivalis and contribute to elucidation of the common nature of the interaction between platelets and pathogenic bacteria.