Peptides related to the carboxyl terminus of human platelet factor IV with antibacterial activity.

Abstract

A peptide (C13) corresponding to the last 13 amino acids of the carboxyl terminus of human platelet factor IV was found to be antibacterial. Amino acid substitutions predicted to disrupt either the amphipathic or a-helical nature of C13 rendered the peptide inactive. Antibacterial activity was demonstrated in normal human serum on bacteria which had been previously exposed to low levels of cefepime, a f-lactam antibiotic. Peptide analogues were examined for more potent antibacterial activity in an antibacterial assay that employed normal human serum and low levels of cefepime. A peptide analogue (C18G) with 80-fold more antibacterial activity than C13 was identified. Studies in C8-deficient sera confirmed an essential role of human serum complement for optimal antibacterial activity. Additional studies showed low levels of cefepime, although not essential, enhanced the antibacterial activity of C18G. Animal protection experiments demonstrated that either peptide C18G or an analogue with all D amino acids (C18X) significantly increased the survival of neutropenic mice when coadministered with a low level of cefepime. This work has resulted in the identification of a new group of antibacterial peptides. (J. Clin. Invest. 1992. 90:447455.)

Enterohemorrhagic and enteropathogenic Escherichia coli evolved different strategies to resist antimicrobial peptides

“…Thus, EHEC and EPEC appear to the presence or absence of the synthetic α-helical AMP C18G, which was previously shown to be readily degraded by EHEC OmpT. 14,21 In the absence of AMP, both the wild-type and ΔompT EHEC cells exhibited intense fluorescence outlines with uniform staining of the OM, indicating that ChFP localizes to the cell envelope ( Fig. 2A and B).…”

Identification of Legionella pneumophila rcp , a pagP -Like Gene That Confers Resistance to Cationic Antimicrobial Peptides and Promotes Intracellular Infection

“…were used to check the resistance of 130b and its mutants to CAMPs. To assess this resistance, a standard microdilution susceptibility assay, which uses minimal amounts of each CAMP, was performed (21,36,53,73,81). Bacteria grown in BYE, CDM, or CDM containing various amounts of Mg 2ϩ were diluted to 5 ϫ 10 4 CFU/ml in 2ϫ BYE.…”

“…supplemented with 10% heat-inactivated fetal calf serum (HyClone, Logan, Utah) and 2.5 ml of amphotericin B (Fungizone; Gibco Life Technologies) in a 5% CO 2 incubator at 37°C. Using a multiplicity of infection (MOI) of 1, 10 6 adherent U937 macrophages were infected with bacteria grown for 3 days on BCYE agar, as standardly performed (1,3,21,56). After a 2-h incubation period to allow bacterial internalization, extracellular bacteria were removed by repeated washing, and then infected monolayers were incubated at 37°C in a 5% CO 2 incubator.…”

PmrAB, a Two-Component Regulatory System of Pseudomonas aeruginosa That Modulates Resistance to Cationic Antimicrobial Peptides and Addition of Aminoarabinose to Lipid A

“…Quantitative bactericidal assays (39) were performed with the following modifications: cells were diluted to 2 ϫ 10 4 CFU per ml prior to assay, and assays of human ␤-defensin activity were performed in 1.4% tryptic soy broth with 10 mM Na phosphate (pH 7.4) rather than Mueller-Hinton broth. The PAKpmrB6 and PAKpmrB12 strains displayed cross-resistance to defensins, protegrin, and ␣-helical peptides, as reflected by relative LD 50 s (compared to those of the PAK parental strain) for human ␤-defensin-2 (4), protegrin-1 (39), and C18G, an ␣-helical peptide derived from the carboxy terminus of platelet factor IV (11), that ranged from 3 to Ͼ200 (Table 1). In addition, these strains were also resistant to human ␤-defensin-1, rabbit ␣-defensin NP1, and the ␣-helical cathelicidins CAP18, SMAP29, and LL37 (data not shown).…”