Antimicrobial activity of truncated α-defensin (human neutrophil peptide (HNP)-1) analogues without disulphide bridges

Antimicrobial peptides play an important role in host defence, particularly in the oral cavity where there is constant challenge by microorganisms. The α-defensin antimicrobial peptides comprise 30-50% of the total protein in the azurophilic granules of human neutrophils, the most abundant of which is human neutrophil peptide 1 (HNP-1). Despite its antimicrobial activity, a limiting factor in the potential therapeutic use of HNP-1 is its chemical synthesis with the correct disulphide topology. In the present study, we synthesised a range of truncated defensin analogues lacking disulphide bridges. All the analogues were modelled on the C-terminal region of HNP-1 and their antimicrobial activity was tested against a range of microorganisms, including oral pathogens. Although there was variability in the antimicrobial activity of the truncated analogues synthesised, a truncated peptide named 2Abz23S29 displayed a broad spectrum of antibacterial activity, effectively killing all the bacterial strains tested. The finding that truncated peptides, modelled on the C-terminal β-hairpin region of HNP-1 but lacking disulphide bridges, display antimicrobial activity could aid their potential use in therapeutic interventions.