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Pharmaceuticals 2014, 7(4), 366-391; doi:10.3390/ph7040366

“Specificity Determinants” Improve Therapeutic Indices of Two Antimicrobial Peptides Piscidin 1 and Dermaseptin S4 Against the Gram-negative Pathogens Acinetobacter baumannii and Pseudomonas aeruginosa

1
Department of Biochemistry & Molecular Genetics, University of Colorado, School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
2
Department of Microbiology, University of Colorado, School of Medicine, Anschutz Medical Campus, Aurora, CO 80045, USA
*
Author to whom correspondence should be addressed.
Received: 22 January 2014 / Revised: 12 March 2014 / Accepted: 13 March 2014 / Published: 25 March 2014
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Abstract

A new class of antimicrobial agents with lower rates of resistance and different targets is urgently needed because of the rapidly increasing resistance to classical antibiotics. Amphipathic cationic α-helical antimicrobial peptides (AMPs) represent such a class of compounds. In our previous studies, using a 26-residue de novo designed antimicrobial peptide, we proposed the concept of “specificity determinant(s)”: positively charged residue(s) in the center of the non-polar face of AMPs that could decrease hemolytic activity/toxicity but increase or maintain the same level of antimicrobial activity to increase dramatically the therapeutic index. In the current study, we used d-enantiomers of two AMPs, Piscidin 1 isolated from fish and dermaseptin S4 isolated from frog. We substituted different positions in the center of the hydrophobic face with one or two lysine residue(s) (one or two “specificity determinant(s)”). This simple modification not only maintained or improved antimicrobial activity against Gram-negative pathogens Acinetobacter baumannii (11 strains) and Pseudomonas aeruginosa (6 strains), but also dramatically decreased hemolytic activity of human red blood cells, as predicted. Therapeutic indices improved by 55-fold and 730-fold for piscidin 1 (I9K) and dermaseptin S4 (L7K, A14K), respectively, against A. baumannii. Similarly, the therapeutic indices improved 32-fold and 980-fold for piscidin 1 (I9K) and dermaseptin S4 (L7K, A14K), respectively, against P. aeruginosa.
Keywords: Acinetobacter baumannii; antimicrobial peptides; Gram-negative pathogens; Pseudomonas aeruginosa; specificity determinant(s); temperature-profiling by RP-HPLC Acinetobacter baumannii; antimicrobial peptides; Gram-negative pathogens; Pseudomonas aeruginosa; specificity determinant(s); temperature-profiling by RP-HPLC
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This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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MDPI and ACS Style

Jiang, Z.; Vasil, A.I.; Vasil, M.L.; Hodges, R.S. “Specificity Determinants” Improve Therapeutic Indices of Two Antimicrobial Peptides Piscidin 1 and Dermaseptin S4 Against the Gram-negative Pathogens Acinetobacter baumannii and Pseudomonas aeruginosa. Pharmaceuticals 2014, 7, 366-391.

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