antimicrobial-peptide-ib-367 and Disease-Models--Animal

Innate host defence, involving both cellular and humoral mediators, is a prominent function of the human airways. Cellular mediators of innate immunity include dendritic cells, natural killer cells, cytotoxic T cells, macrophages and neutrophils, while humoral mediators of innate immunity consist of components of the epithelial lining fluid (ELF) covering the airways. Microbicidal substances in the ELF can selectively disrupt bacterial cell walls and membranes, sequester microbial nutrients or act as decoys for microbial attachment. Antimicrobial components of airway secretions include lysozymes, lactoferrin, secretory leukoprotease inhibitor, defensins and cathelicidins. Defensins are the most widely studied family of antimicrobial peptides present in airway fluid. Humans produce at least 10 different defensin molecules, six alpha-defensins and four beta-defensins similar in structure and function. Direct evidence that defensins have central roles in host defense has only recently become available. Some defensins and defensin-like molecules could serve as templates for the development of pulmonary pharmaceuticals. As potential therapeutics, they possess several desirable properties, including the ability to kill a broad spectrum of micro-organisms while permitting little development of microbial resistance. Many peptides can also neutralize effects of lipopolysaccharide on macrophages and other host defense cells and decrease the release of proinflammatory cytokines thereby giving protection against septic shock. Protegrin-1 is a minidefensin isolated from pig leukocytes and has proved to be an attractive template for large-scale development of antibacterials. One such protegrin analog, iseganan is in phase III clinical trials for the treatment of oral mucositis secondary to systemic chemotherapy. Other prospective uses of iseganan include control of respiratory pathogens in patients with cystic fibrosis and reduction of oral bacteria to prevent ventilator-associated pneumonia. However, in order to advance the production and clinical testing of peptide-based therapeutics, technical hurdles of synthesizing large quantities of complexly folded peptides must be first overcome. Strategies to develop potent peptide-based microbicides are promising in the struggle against increasingly resistant pathogens.

Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Clinical Trials as Topic; Defensins; Disease Models, Animal; Drugs, Investigational; Humans; Lung; Lung Diseases; Molecular Sequence Data; Peptides; Proteins

The aim of our study was to evaluate the in vitro activity of IB-367 and its bactericidal effect for Pseudomonas aeruginosa and Escherichia coli, associated to a synergic study to test the antibiotic combinations between the peptide and colistin or imipenem. Minimum inhibitory concentrations (MICs), the minimum bactericidal concentrations (MBCs), the synergy test and killing study were carried out to evaluate the IB-367 activity. In the in vivo model, a wound was incised through the panniculus carnosus of BALB/c mice, and then inoculated with 5 × 107 colony-forming units of P. aeruginosa and E. coli. For each strain, the study included an infected or not infected group that did not receive any treatment, and five contaminated groups treated with local IB- 367, intraperitoneal imipenem, intraperitoneal colistin, topical IB-367 local plus intraperitoneal imipenem or intraperitoneal colistin. All isolates were inhibited by IB-367 at concentrations of 4-64 mg/l. Killing by IB-367 was shown to be very rapid: its activity on all Gram-negative bacteria was completed within a 40 min exposure period at a concentration of 2 × MIC/l. Synergy was demonstrated when IB-367 was combined with colistin or imipenem. In in vivo studies, the groups treated with topical IB-367 and intraperitoneal colistin showed the best results in terms of bacterial load inhibition either for Pseudomonas or for E. coli. The good in vitro activity and in vivo efficacy, as well as, the synergic interactions with antibiotics suggest that IB-367 is a promising candidate for potential application in the treatment of wound Gram-negative infections.

Topics: Acinetobacter baumannii; Administration, Topical; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Colistin; Disease Models, Animal; Drug Therapy, Combination; Escherichia coli; Gram-Negative Bacterial Infections; Humans; Imipenem; Injections, Intraperitoneal; Klebsiella pneumoniae; Mice, Inbred BALB C; Microbial Sensitivity Tests; Pseudomonas aeruginosa

Antimicrobial peptides are known as immunomodulators and antibiotic enhancers. We report that administration of an antimicrobial peptide, IB-367, was efficacious in increasing the antimicrobial activity of daptomycin and teicoplanin in a mouse model of wound infection caused by meticillin-resistant Staphylococcus aureus (MRSA). Mice were assigned to seven groups: an IB-367 pre-treated group with no antibiotics given after challenge, two IB-367 pre-treated groups plus daptomycin or teicoplanin given after challenge, two groups treated with daptomycin or teicoplanin only after challenge, and two control groups without infection or that did not receive any treatment. The main outcome measures were quantitative bacterial culture and analysis of natural killer (NK) cytotoxicity and leukocyte phenotype. The wound, established through the panniculus carnosus muscle of mice, was infected by MRSA. Bacterial cultures of mice receiving antibiotics alone showed a -2 log decrease, whilst those for IB-367 plus daptomycin or teicoplanin showed a -4 log decrease. IB-367 plus daptomycin showed the highest efficacy. The higher antimicrobial effect exerted by IB-367 was associated with increased levels of NK cytotoxicity but not of NK cell number. IB-367 increased the number of both CD11b and Gr-1 cells 3 days after MRSA challenge, whereas both of these leukocyte populations were reduced at 10 days after challenge. Our data suggest that a combination of IB-367 with antibiotic exerts a therapeutic effect and may be useful for the management of staphylococcal wounds.

Topics: Animals; Antimicrobial Cationic Peptides; Bacterial Load; Daptomycin; Disease Models, Animal; Drug Therapy, Combination; Male; Methicillin-Resistant Staphylococcus aureus; Mice; Mice, Inbred BALB C; Staphylococcal Infections; Teicoplanin; Treatment Outcome; Wound Infection

Postoperative morbidity in patients with obstructive jaundice remains high because of increased susceptibility to endotoxin and the inflammatory cascade.. An experimental study was designed to investigate the efficacy of protegrin peptide IB-367, an antimicrobial positively charged peptide, in neutralising Escherichia coli 0111:B4 lipopolysaccharide (LPS) in bile duct ligated rats.. Adult male Wistar rats were injected intraperitoneally with 2 mg/kg E coli 0111:B4 LPS one week after sham operation or bile duct ligation (BDL). Six groups were studied: sham with placebo, sham with 120 mg/kg tazobactam-piperacillin (TZP), sham with 1 mg/kg IB-367, BDL with placebo, BDL with 120 mg/kg TZP, and BDL with 1 mg/kg IB-367.. Main outcome measures were: endotoxin and tumour necrosis factor alpha (TNF-alpha) concentrations in plasma, evidence of bacterial translocation in blood and peritoneum, and lethality. After LPS, TNF-alpha plasma levels were significantly higher in BDL rats compared with sham operated animals. IB-367 caused a significant reduction in plasma endotoxin and TNF-alpha concentrations compared with placebo and TZP treated groups. In contrast, both TZP and IB-367 significantly reduced bacterial growth compared with saline treatment. Finally, LPS induced 60% and 55% lethality in BDL placebo and TZP treated rats and no lethality in sham operated rats, while only IB-367 significantly reduced lethality to 10%.. By virtue of its dual antimicrobial and antiendotoxin properties, IB-367 could be an interesting compound to inhibit bacterial translocation and endotoxin release in obstructive jaundice.

Topics: Animals; Anti-Infective Agents; Antimicrobial Cationic Peptides; Bacterial Translocation; Bile Ducts; Cholestasis; Disease Models, Animal; Endotoxemia; Escherichia coli Infections; Ligation; Lipopolysaccharides; Male; Peptides; Postoperative Complications; Proteins; Rats; Rats, Wistar; Tumor Necrosis Factor-alpha

The therapeutic efficacy of protegrin peptide IB-367 was investigated in three rat models of septic shock: (i) rats injected intraperitoneally with 1mg Escherichia coli 0111:B4 lipopolysaccharide, (ii) rats given an intraperitoneal injection of 2 X 10(10) CFU of E. coli ATCC 25922, and (iii) rats in which intra-abdominal sepsis was induced via cecal ligation and puncture. All animals were randomized to receive parenterally isotonic sodium chloride solution, 1mg/kg of IB-367, 60mg/kg piperacillin and 1mg/kg of IB-367 plus 60mg/kg piperacillin. The peptide demonstrated lower level of antimicrobial activity than piperacillin, nevertheless it exhibited the dual properties of antimicrobial and antiendotoxin agent. Finally IB-367 and piperacillin association showed to be the most effective therapeutic approach.

Topics: Animals; Antimicrobial Cationic Peptides; Cecum; Disease Models, Animal; Drug Therapy, Combination; Escherichia coli Infections; Ligation; Lipopolysaccharides; Male; Microbial Sensitivity Tests; Peptides; Peritonitis; Piperacillin; Proteins; Punctures; Rats; Rats, Wistar; Shock, Septic

Protegrin antimicrobial peptides possess activity against gram-positive and gram-negative bacteria and yeasts. An extensive structure-activity relationship (SAR) study was conducted on several hundred protegrin analogues to gain understanding of the relationship between the primary and secondary structure of the protegrins and their antimicrobial activities, and to identify a protegrin analogue for clinical development. Native sequence protegrins are cationic, amphiphilic peptides that are characterized by the presence of a beta-sheet structure that is maintained by two disulfide bridges. The presence of the beta-sheet is key to the stability of the protegrin structure; linearized analogues or analogues that have amino acid substitutions that eliminate hydrogen bonding across the beta-sheet have reduced activity, especially in the presence of physiological concentrations of NaCl. Also, maintaining amphiphilicity of the beta-sheet is key; analogues with substitutions of polar amino acids in the hydrophobic face have reduced activity. Analogues with reduced positive charge tend to be less active, an observation that is more marked for gram-negative than gram-positive bacteria, and may implicate binding to lipopolysaccharide as a key mechanistic step in the killing of gram-negative bacteria. A very large number of amino acid substitutions are tolerated by the protegrin structure, implying that overall structural features such as amphiphilicity, charge, and shape are more important to activity than the presence of specific amino acids. This lack of importance of specific stereochemistry is supported by the fact that completely D-amino acid substituted protegrins are fully potent. Based on the SAR studies, and on the microbiological data from an animal model, one protegrin analogue, IB-367, was selected for clinical development as a topical agent to prevent the oral mucositis associated with cancer therapy.

Topics: Amino Acid Sequence; Animals; Anti-Bacterial Agents; Antimicrobial Cationic Peptides; Cathelicidins; Cricetinae; Disease Models, Animal; Microbial Sensitivity Tests; Molecular Sequence Data; Mouth Mucosa; Peptides; Peptides, Cyclic; Proteins; Stomatitis; Structure-Activity Relationship