Methods: Strains of P. gingivalis were subjected to GL13K and D-GL13K (100 µg/ml) for 2 hours in 10 mM Sodium-Phosphate buffer and plated on blood agar plates. Colonies were counted to assess the effect of the peptides. To test in vivo effectiveness of D-GL13K, 4∙109 P. gingivalis W50 cells were delivered into the cheeks of both sham and treatment group mice (12 each). Immediately after injection, D-GL13K (100 µg/ml) was provided to the treatment group mice in drinking water for 24 h. The amount of alveolar bone loss was determined between the sham and D-GL13K treated mice 48 days after the first bacterial challenge.
Results: D-GL13K, but not GL13K, effectively killed P. gingivalis. Protease-deficient mutants of P. gingivalis were similarly killed by D-GL13K but not GL13K. P. gingivalis infected mice given D-GL13K peptide in their drinking water showed no significant different alveolar bone loss compared to the control group.
Conclusions: D-GL13K showed bactericidal activity against P. gingivalis. Surprisingly, gingipain mutants were not susceptible to GL13K, indicating that gingipains were not the cause of resistance against GL13K. Providing D-GL13K in the drinking water did not affect the amount of bone loss in P. gingivalis infected mice. It is likely that different peptide delivery methods must be explored.
Supported by PHS grant R01DE017989 and UMN-SOD Summer Fellowship Program