Dermatan sulphate is released by proteinases of common pathogenic bacteriaand inactivates antibacterial alpha-defensin

Defensins represent an evolutionarily conserved group of small peptides wit h potent antibacterial activities. We report here that extracellular protei nases secreted by the human pathogens Pseudomonas aeruginosa, Enterococcus faecalis and Streptococcus pyogenes release dermatan sulphate by degrading dermatan sulphate-containing proteoglycans, such as decorin. Dermatan sulph ate was found to bind to neutrophil-derived alpha -defensin, and this bindi ng completely neutralized its bactericidal activity. During infection, prot eoglycan degradation and release of dermatan sulphate may therefore represe nt a previously unknown virulence mechanism, which could serve as a target for novel antibacterial strategies.