Vaccination with recombinant adhesins from the RgpA-Kgp proteinase-adhesin complex protects against Porphyromonas gingivalis infection.

Porphyromonas gingivalis is a pathogen associated with chronic periodontitis, an inflammatory disease of the supporting tissues of the teeth. A major virulence factor for P. gingivalis is the RgpA-Kgp proteinase-adhesin complex. We have prepared the following recombinant proteins corresponding to domains/regions of the RgpA-Kgp complex; rRgpA(cat), rRgpA(A1), rRgpA(A2), rRgpA(A4), rRgpA(A1)(784-1009), rRgpA(A1)(911-1009), rKgp(A1) and rKgp(A1)(759-989). The ability of each recombinant protein to attenuate P. gingivalis infection, when used as a vaccine, in the murine lesion model was determined. All of the recombinant adhesin domains were found to significantly attenuate P. gingivalis infection with the most effective being rKgp(A1) and rKgp(A1)(759-989) followed by rRgpA(A1), rRgpA(A1)(784-1009) and rRgpA(A1)(911-1009). The predominant antibody isotype was IgG1. The A1 adhesins, which gave the best protection, contain specific motifs implicated in binding to host tissue. Immunisation with rRgpA(cat) had no effect on P. gingivalis infection. As well as detecting the Kgp(A1) adhesin in a Western blot, the rKgp(A1) and rKgp(A1)(759-989) antisera were also immunoreactive with the A1 and A3 adhesins of RgpA and HagA. Flow cytometric analysis indicated that rKgp(A1) and rRgpA(A1) antisera recognised native antigen on P. gingivalis whole cells. Furthermore, the rKgp(A1) and rKgp(A1)(759-989) antisera exhibited a similar immunoreactive profile with outer membrane preparations of all P. gingivalis serotypes and clinical isolates tested. The recombinant A1 adhesin therefore has potential in the development of a P. gingivalis vaccine.