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Deslouches, Berthony (2006) DE NOVO CATIONIC ANTIMICROBIAL PEPTIDES AS THERAPEUTICS AGAINST PSEUDOMONAS AERUGINOSA. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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Cationic antimicrobial peptides (CAPs) are a very diverse group of amphipathic agents that demonstrate broad activity against Gram-positive and -negative bacteria. To overcome the obstacle of drug resistance among bacterial pathogens, CAPs have been extensively investigated as a potential source of new antimicrobials with novel mechanisms of action that may complement current antibiotic regimens. However, the suppression of antimicrobial activity in biological conditions (e.g., physiological salt concentrations, serum) constitutes a major challenge to the successful development of CAPs for clinical applications. We hypothesized that CAPs with optimized amphipathic structures can be designed de novo to enhance antibacterial activity and selective toxicity in environments that are generally challenging to host-derived peptides. Furthermore, the antibacterial efficacy will positively correlate with length, charge, Trp content, and helicity. Three specific aims were developed to address this hypothesis. The first aim addressed the design of amphipathic peptides to evaluate the influence of helicity, length, and Trp content on activity. Using a base unit peptide approach, we synthesized a multimeric series of 12-residue lytic base unit (LBU) composed of Arg and Val residues, positioned to form idealized amphipathic ƒÑ-helices. Another series of LBU derivatives (WLBU) was engineered by substituting Trp residues on the hydrophobic face. The correlation between length and helicity was established by circular dichroism analysis. Bacterial killing assays revealed no appreciable increase in activity for peptides longer than 24 residues. In addition, the inclusion of Trp residues in the hydrophobic face increased potency and selectivity in a novel co-culture system utilizing bacteria and primary cell lines, which led to the selection of WLBU2 as the shortest peptide (24 residues in length) with the highest potency. The second objective was to examine the selective toxicity of WLBU2 in biological or biologically-derived media. In contrast to the human CAP LL37, the peptide WLBU2 displayed potent activity against Pseudomonas aeruginosa in the presence of human serum and human blood ex-vivo, with no detectable red blood cell lysis or toxicity to human monocytes at all test concentrations. Finally, we demonstrated potent activity of WLBU2 in intraperitoneal and intravenous mouse models of Pseudomonas aeruginosa infection. WLBU2 not only protected mice prophylactically but also eradicated P. aeruginosa from the blood and other tissues at 3 to 4mg/kg. Furthermore, WLBU2 displayed only a minor stimulatory effect on inflammatory cytokines, notably IL1-£] and TNF-ƒÑ. Consistent with our in vitro studies, the in vivo data provide strong evidence for the potential application of WLBU2 in the treatment of systemic infection due to P. aeruginosa.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Deslouches, Berthonybedst12@pitt.eduBEDST12
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairMontelaro, Ronald Crmont@pitt.eduRMONT
Committee CoChairMietzner, Timothy Amietzner@pitt.eduMIETZNER
Committee MemberMcClane, Bruce Abamcc@pitt.eduBAMCC
Committee MemberParniak, Michael
Committee MemberCascio, Michaelcascio@pitt.eduCASCIO
Committee Member Hillier, Sharon Lslh6@pitt.eduSLH6
Date: 11 January 2006
Date Type: Completion
Defense Date: 29 June 2005
Approval Date: 11 January 2006
Submission Date: 30 August 2005
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Institution: University of Pittsburgh
Schools and Programs: School of Medicine > Molecular Virology and Microbiology
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: antibiotics; Antimicrobial peptides; antimicrobial therapy; cationic amphipathic peptides; Pseudomonas aeruginosa; staphylococcus aureus
Other ID:, etd-08302005-113738
Date Deposited: 10 Nov 2011 20:01
Last Modified: 15 Nov 2016 13:49


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