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; rRgpAcat, rRgpAA1, rRgpAA2, rRgpAA4, rRgpAA1(784–1009), rRgpAA1(911–1009), rKgpA1 and rKgpA1(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 rKgpA1 and rKgpA1(759–989) followed by rRgpAA1, rRgpAA1(784–1009) and rRgpAA1(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 rRgpAcat had no effect on P. gingivalis infection. As well as detecting the KgpA1 adhesin in a Western blot, the rKgpA1 and rKgpA1(759–989) antisera were also immunoreactive with the A1 and A3 adhesins of RgpA and HagA. Flow cytometric analysis indicated that rKgpA1 and rRgpAA1 antisera recognised native antigen on P. gingivalis whole cells. Furthermore, the rKgpA1 and rKgpA1(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.