Chicken cathelicidin-2-derived peptides with enhanced immunomodulatory and antibacterial activities against biological warfare agents.

Host defence peptides (HDPs) are considered to be excellent candidates for the development of novel therapeutic agents. Recently, it was demonstrated that the peptide C1-15, an N-terminal segment of chicken HDP cathelicidin-2, exhibits potent antibacterial activity while lacking cytotoxicity towards eukaryotic cells. In the present study, we report that C1-15 is active against bacteria such as Bacillus anthracis and Yersinia pestis that may potentially be used by bioterrorists. Substitution of single and multiple phenylalanine (Phe) residues to tryptophan (Trp) in C1-15 resulted in variants with improved antibacterial activity against B. anthracis and Y. pestis as well as decreased salt sensitivity. In addition, these peptides exhibited enhanced neutralisation of lipopolysaccharide (LPS)-induced release of pro-inflammatory cytokines in human peripheral blood mononuclear cells (PBMCs). The antibacterial and LPS-neutralising activities of these C1-15-derived peptides are exerted at concentrations far below the concentrations that are toxic to human PBMCs. Taken together, we show that Phe-->Trp substitutions in C1-15 variants enhances the antibacterial and LPS-neutralising activities against pathogenic bacteria, including those that may potentially be used as biological warfare agents.

Evaluation of the antibacterial spectrum of drosocin analogues.

Drosocin is a 19-mer, cationic antimicrobial peptide from Drosophila melanogaster. The aim of the study was to examine the antibacterial spectrum of unglycosylated drosocin analogues. Furthermore, the amino acid sequence of DnaK, drosocin's intracellular target, from susceptible species was aligned and studied for sequence homology. From this a panel of 31 bacterial strains, including Salmonella strains with truncated lipopolysaccharide structures, was tested for susceptibility towards three drosocin analogues. Available bacterial DnaK amino acid sequences were retrieved from the ExPASy proteomics server of the Swiss Institute of Bioinformatics studied for sequence homology. Seventeen of the 31 strains tested were susceptible for the drosocin analogues. Minimal inhibitory concentration values against mainly Gram-negative bacteria ranged from 3.1 to 100 microm. With the exception of Micrococcus luteus and Xanthomonas campestris all drosocin analogue-susceptible strains were Enterobacteriaceae showing a high DnaK amino acid sequence homology.