A PEPTIDE DOMAIN ON GINGIPAIN-R WHICH CONFERS IMMUNITY AGAINST PORPHYROMONAS-GINGIVALIS INFECTION IN MICE

The cysteine proteinases referred to as gingipains R (gingipain R1 and gingipain R2) and gingipain K produced by Porphyromonas gingivalis ar e virulence factors of this periodontal pathogen which likely act by i nterrupting host defense mechanisms and by participating in the penetr ation and destruction of host connective tissue. To examine the effect of immunization with gingipains R on the ability of P, gingivalis to colonize and invade in the mouse chamber model, BALB/c mice were immun ized intraperitoneally with the 95-kDa gingipain Ri, the 50-kDa gingip ain R2, or multiple antigenic peptide (MAP)-conjugated gingipain R-der ived peptides and then challenged with P. gingivalis. Immunization of mice with the 95-kDa gingipain R1, the 50-kDa gingipain R2, or a pepti de derived from the N-terminal sequence of the catalytic domain of gin gipains R (peptide A) followed by challenge with P. gingivalis A7436 r esulted in protection from P. gingivalis; invasion. In contrast, immun ization with peptides corresponding to either a sequence encompassing the catalytic cysteine residue of gingipains R (peptide B) or an ident ical sequence within the catalytic domains of gingipain R1 and gingipa in K (peptide C), followed by challenge with P. gingivalis, did not pr otect animals, nor did immunization with a peptide corresponding to se quences within the adhesion/hemagglutinin domain of gingipain R1 (pept ide D) which have been shown to be directly involved in the hemaggluti nin activity of gingipain R1, However, the immunoglobulin G (IgG) tite r obtained following immunization with peptide D nas comparable to tha t obtained following immunization with the N-terminal peptide (peptide A). Competitive enzyme-linked immunosorbent assays, using either the 95-kDa gingipain R1 or gingipain K as the competing soluble antigen, i ndicated that 42 and 53% of the antibodies induced by immunization wit h heat-killed bacteria recognize gingipain RI and gingipain R, respect ively; however, even at very high concentrations, the 50-kDa gingipain R2 did not hinder IgG binding to P, gingivalis. These results indicat e that antibodies directed to the amino-terminal region of the catalyt ic domain of gingipains R are capable of inducing a protective immune response against P. gingivalis infection in the mouse chamber model.