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Amino Acid Sequence, Bronchoalveolar Lavage Fluid, Coculture Techniques, Cystic Fibrosis, Humans, Leukocyte Elastase, Lung, Microbial Sensitivity Tests, Molecular Sequence Data, Neutrophils, Primary Cell Culture, Prodrugs, Pseudomonas aeruginosa, Sodium Chloride, alpha-Defensins


This work was funded by the Higher Education Authority, Ireland, under the BioAT program in Cycle 5 of the Programme for Research in Third- Level Institutions and by the Science Foundation Ireland under Equipment Grant no. 06/RFP/CHO024/602 EC07 for the peptide synthesizer.


Copyright © American Society for Microbiology, Antimicrobial Agents and Chemotherapy. 2014;58(2):978-85. doi: 10.1128/AAC.01167-13


Host defense peptides (HDPs) are short antimicrobial peptides of the innate immune system. Deficiencies in HDPs contribute to enhanced susceptibility to infections, e.g., in cystic fibrosis (CF). Exogenous HDPs can compensate for these deficiencies, but their development as antimicrobials is limited by cytotoxicity. Three HDP prodrugs were designed so their net positive charge is masked by a promoiety containing a substrate for the enzyme neutrophil elastase (NE). This approach can confine activation to sites with high NE levels. Enzyme-labile peptides were synthesized, and their activation was investigated using purified NE. Susceptibilities of Pseudomonas aeruginosa to parent and prodrug peptides in the presence and absence of NE-rich CF human bronchoalveolar lavage (BAL) fluid and different NaCl concentrations were compared. The effect of the HDP promoiety on cytotoxicity was determined with cystic fibrosis bronchial epithelial (CFBE41o-) cells. NE in CF BAL fluids activated the HDP prodrugs, restoring bactericidal activity against reference and clinical isolates of P. aeruginosa. However, activation also required the addition of 300 mM NaCl. Under these conditions, the bactericidal activity levels of the HDP prodrugs differed, with pro-P18 demonstrating the greatest activity (90% to 100% of that of the parent, P18, at 6.25 μg/ml). Cytotoxic effects on CFBE41o- cells were reduced by the addition of the promoiety to HDPs. We demonstrate here for the first time the selective activation of novel HDP prodrugs by a host disease-associated enzyme at in vivo concentrations of the CF lung. This approach may lead to the development of novel therapeutic agents with low toxicity that are active under the challenging conditions of the CF lung.


Medicine and Health Sciences


Forde E, Humphreys H, Greene CM, Fitzgerald-Hughes D, Devocelle M. Potential of host defense peptide prodrugs as neutrophil elastase-dependent anti-infective agents for cystic fibrosis. 2014;58(2):978-85.

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