IADR Abstract Archives
Antibacterial Activity of Peptides Derived from the Beta-Defensin hBD-3 C-Terminus
Objectives: Defensins are cationic peptides with broad-spectrum antibiotic activity. Human neutrophils contain four alpha-defensins known as Human Neutrophil Peptide (HNP) 1-4. Epithelial cells produce four beta-defensins known as human Beta Defensin (hBD) 1-4. Gram-negative anaerobic bacteria associated with periodontal disease are resistant to human neutrophil alpha-defensins, but are killed by beta-defensins. Compared with alpha-defensins, the beta-defensin hBD-3 has additional hydrophobic and cationic amino acid residues near the N-terminus and additional cationic residues at the C-terminus. The aim was to compare activity of cationic peptides from the C-terminus against control, non-pathogenic Escherichia coli (ML-35; ATCC43827) and the periodontal pathogen A.a. (Aggregatibacter actinomycetemcomitans; Y4; ATCC43718).
Methods: Bacteria were incubated 4 h at 37°C under aerobic (E. coli) or anaerobic (A.a.) conditions with recombinant hBD-3, the synthetic peptide CHRG01, which has a sequence derived from the C-terminus of hBD-3 (Hoover et al. Antimicrob Agents Chemother 47:2804, 2003), and with peptides based on the CHRG01 sequence. Viability was determined by diluting, plating, and counting colonies.
Results: hBD-3 at 5 to 10 µM killed >90% of the bacteria. The cationic CHRG01 peptide was less active than hBD-3. CHRG01 killed 90% of E. coli at 10 µM and 90% of A.a. at 30 µM. Peptide MJ04 with two hydrophobic leucine residues substituted for serine residues in CHRG01 was more active than CHRG01 against both E. coli and A.a., and MJ05 with four leucine residues substituted for serines was more active than hBD-3 against both E. coli and A.a.
Conclusions: a) A.a. is more resistant than E. coli to cationic peptides; b) Both hydrophobic and cationic residues are needed for activity against A.a.; c) Short peptides with a mixture of hydrophobic and cationic residues can be more effective than hBD-3 and would be easier to synthesize and easier to use in clinical applications.
Methods: Bacteria were incubated 4 h at 37°C under aerobic (E. coli) or anaerobic (A.a.) conditions with recombinant hBD-3, the synthetic peptide CHRG01, which has a sequence derived from the C-terminus of hBD-3 (Hoover et al. Antimicrob Agents Chemother 47:2804, 2003), and with peptides based on the CHRG01 sequence. Viability was determined by diluting, plating, and counting colonies.
Results: hBD-3 at 5 to 10 µM killed >90% of the bacteria. The cationic CHRG01 peptide was less active than hBD-3. CHRG01 killed 90% of E. coli at 10 µM and 90% of A.a. at 30 µM. Peptide MJ04 with two hydrophobic leucine residues substituted for serine residues in CHRG01 was more active than CHRG01 against both E. coli and A.a., and MJ05 with four leucine residues substituted for serines was more active than hBD-3 against both E. coli and A.a.
Conclusions: a) A.a. is more resistant than E. coli to cationic peptides; b) Both hydrophobic and cationic residues are needed for activity against A.a.; c) Short peptides with a mixture of hydrophobic and cationic residues can be more effective than hBD-3 and would be easier to synthesize and easier to use in clinical applications.
