Rational Design of Engineered Cationic Antimicrobial Peptides Consisting Exclusively of Arginine and Tryptophan, and Their Activity against Multidrug-Resistant Pathogens

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 g/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.

Section: Figmentioning

confidence: 99%

Potential of Host Defense Peptide Prodrugs as Neutrophil Elastase-Dependent Anti-Infective Agents for Cystic Fibrosis

Forde

Humphreys

Greene

et al. 2014

“…Another AMP chosen for prodrug modification, WR12, comes from a series of salt-resistant peptides synthesized by Deslouches et al (27,28). Its activity and cytotoxicity characteristics are also promising in the CF context, as it was shown to have good activity against a panel of 100 Pseudomonas isolates from CF patients (27,28).…”

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confidence: 99%

Differential In Vitro and In Vivo Toxicities of Antimicrobial Peptide Prodrugs for Potential Use in Cystic Fibrosis

Forde

Schutte

Reeves

et al. 2016

There has been considerable interest in the use of antimicrobial peptides (AMPs) as antimicrobial agents for the treatment of many conditions, including cystic fibrosis (CF). The challenging conditions of the CF patient lung require robust AMPs that are active in an environment of high proteolytic activity but that also have low cytotoxicity and immunogenicity. Previously, we developed prodrugs of AMPs that limited the cytotoxic effects of AMP treatment by rendering the antimicrobial activity dependent on the host enzyme neutrophil elastase (NE). However, cytotoxicity remained an issue. Here, we describe the further optimization of the AMP prodrug (pro-AMP) model for CF to produce pro-WMR, a peptide with greatly reduced cytotoxicity (50% inhibitory concentration against CFBE41o-cells, >300 M) compared to that of the previous group of pro-AMPs. The bactericidal activity of pro-WMR was increased in NE-rich bronchoalveolar lavage (BAL) fluid from CF patients (range, 8.4% ؎ 6.9% alone to 91.5% ؎ 5.8% with BAL fluid; P ‫؍‬ 0.0004), an activity differential greater than that of previous pro-AMPs. In a murine model of lung delivery, the pro-AMP modification reduced host toxicity, with pro-WMR being less toxic than the active peptide. Previously, host toxicity issues have hampered the clinical application of AMPs. However, the development of application-specific AMPs with modifications that minimize toxicity similar to those described here can significantly advance their potential use in patients. The combination of this prodrug strategy with a highly active AMP has the potential to produce new therapeutics for the challenging conditions of the CF patient lung.

“…1), form amphipathic ␣-helices in a hydrophobic environment and display broad activities in vitro against diverse Gramnegative and Gram-positive bacteria, including several highly drug-resistant strains (20)(21)(22). Importantly, WLBU2 is the first synthetic AMP to demonstrate an ability to eradicate otherwise lethal P. aeruginosa septicemia in vivo in a systemic treatment model in mice (23,24).…”

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confidence: 99%

“…In addition, almost all eCAP-resistant strains also displayed resistance to colistin and LL37: 10 of the 11 WLBU2-and 14 of the 18 WR12-resistant isolates were also resistant to colistin and LL37 ( Table 2). As the 142 isolates were selected because of their MDR/XDR properties (see Table SA1 in the supplemental material), it is quite interesting that colistin and LL37 were active against 51% of these isolates, particularly considering that these isolates have probably been exposed to LL37 in the context of an infected patient with an underlying pathophysiological condition, which reflects environment-dependent efficacy (20,30). With regard to colistin, the data are consistent with its frequent use as a last-resort antibiotic against MDR bacterial pathogens, given the fact that the panel of clinical isolates used in this study is skewed toward MDR/XDR phenotypes (31,32).…”

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confidence: 99%

Engineered Cationic Antimicrobial Peptides To Overcome Multidrug Resistance by ESKAPE Pathogens

Deslouches

Steckbeck

Craigo

et al. 2015

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c Multidrug resistance constitutes a threat to the medical achievements of the last 50 years. In this study, we demonstrated the abilities of two de novo engineered cationic antibiotic peptides (eCAPs), WLBU2 and WR12, to overcome resistance from 142 clinical isolates representing the most common multidrug-resistant (MDR) pathogens and to display a lower propensity to select for resistant bacteria in vitro compared to that with colistin and LL37. The results warrant an exploration of eCAPs for use in clinical settings.