Antimicrobial activity of cathelicidin peptides and defensin against oral yeast and bacteria
JH Wong1, TB Ng1, RCF Cheung1, X Dan1, YS Chan1, M Hui2
1 School of Biomedical Sciences, The Chinese University of Hong Kong
2 Department of Microbiology, The Chinese University of Hong Kong
1. Human cathelicidin LL37 and its fragments LL13-37 and LL17-32 were equipotent in inhibiting growth of Candida albicans.
2. LL13-37 permeabilised the membrane of yeast and hyphal forms of C albicans and adversely affected mitochondria.
3. Reactive oxygen species was detectable in the yeast form after LL13-37 treatment but not in untreated cells suggesting that the increased membrane permeability caused by LL13-37 might also lead to uptake of the peptide, which might have some intracellular targets.
4. LL37 and its fragments also showed antifungal activity against C krusei, and C tropicalis.
5. A 5447-Da antifungal peptide with sequence homology to plant defensins was purified from king pole beans by chromatography on Q-Sepharose and FPLC-gel filtration on Superdex 75. It inhibited growth of fungi, including Mycosphaerella arachidicola, Saccharomyces cerevisiae and C albicans with an IC50 value of 3.9, 4.0, and 8.4 µM, respectively. The peptide increased fungal membrane permeability.
6. LL37 did not show obvious antibacterial activity below a concentration of 64 µM and its fragments did not show antibacterial activity below a concentration of 128 µM. Pole bean defensin exerted antibacterial activity on some bacterial species.