Immunization With Porphyromonas gingivalis Cysteine Protease: Effects on Experimental Gingivitis and Ligature‐Induced Periodontitis in Macaca fascicularis

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Abstract
Targeting bacterial virulence factors such as proteases for immunization may hold the key to hmiting or preventing loss of attachment and alveolar bone in periodontal disease. This study examined the chnical, microbiological, and immunological responses following active immunization with a purified Porphyromonas gingivalis cysteine protease (porphypain‐2) in the nonhuman primate (Nhp) Macaca fascicularis. One group of Nhp was immunized with porphypain‐2 antigen while control Nhp received placebo injections. AU Nhp were subjected to experimental gingivitis followed by hgature‐induced periodontitis in a split‐mouth design. An enzyme‐hnked immunosorbent assay demonstrated that immunization elicited a significantly elevated and specific IgG antibody response to both whole cell P. gingivalis (36‐fold) and to porphypain‐2 (194‐fold). Checkerboard hybridization DNA analysis of subgingival plaque from ligated sextants demonstrated that 25% more Gram‐negative anaerobic species became significantly elevated from basehne and at earlier timepoints in the control group than in the immunized group. Immunization with this protease did not suppress the emergence of P. gingivalis. Chnical indices showed few changes related to immunization. Alveolar bone density changes demonstrated a highly significant loss in ligated sextants compared to non‐ligated sextants within the control group (P < 0.001), and a smaller but significant difference within the immunized group (P = 0.043). Comparison of ligated sextants only demonstrated more bone loss in the control group versus the immunized group (−13.07±9.51 versus −9.41±6.18; computerassisted densitometric image analysis units ± SD); the difference approached, but did not reach, significance. The results suggest that porphypain‐2 may contribute to the pathogenic potential of the subgingival plaque microbiota in the Nhp model of hgature‐induced periodontitis, and that active immunization with porphypain‐2 appeared capable of altering this pathogenic response. J Periodontol 1998;69:686–697.