Abstract
BackgroundAntibiotic resistant S. aureus infection is a global threat. Newer approaches are required to control this organism in the current scenario. Cell wall degrading enzymes have been proposed as antibacterial agents for human therapy. P128 is a novel antistaphylococcal chimeric protein under development against S. aureus for human use which derives its bacterial cell wall degrading catalytic endopeptidase domain from ORF56, the Phage K tail-structure associated enzyme. Lead therapeutic entities have to be extensively characterized before they are assessed in animals for preclinical safety and toxicity. P128 is effective against antibiotic resistant strains as well as against a panel of isolates of global significance. Its efficacy against S. aureus in vivo has been established in our lab. Against this background, this study describes the characterization of this protein for its biochemical properties and other attributes.ResultsWe evaluated the requirement or effect of divalent cations and the metal ion chelator, EDTA upon biological activity of P128. As the protein is intended for therapeutic use, we tested its activity in presence of body fluids and antibodies specific to P128. For the same reason, we used standard human cell lines to evaluate cytotoxic effects, if any.The divalent cations, calcium and magnesium at upto 25 mM and Zinc upto 2.5 mM neither inhibited nor enhanced P128 activity. Incubation of this protein with EDTA, human serum, plasma and blood also did not alter the antibacterial properties of the molecule. No inhibitory effect was observed in presence of hyper-immune sera raised against the protein. Finally, P128 did not show any cytotoxic effect on HEp2 and Vero cells at the highest concentration (5 mg/mL) tested.ConclusionsThe results presented here throw light on several properties of protein P128. Taken together, these substantiate the potential of P128 for therapeutic use against S. aureus. Further development of the protein and conduct of preclinical safety studies in animals is warranted.
Highlights
Antibiotic resistant S. aureus infection is a global threat
P128 has shown potent in vitro bactericidal activity against many staphylococci, including methicillin-resistant S. aureus (MRSA) and has been efficacious as a topical gel in reducing MRSA nasal carriage in an animal model [7]
Cytotoxicity of antimicrobial peptides is one of the main reasons that prevent the use of this class of molecules as antibacterial drugs
Summary
Antibiotic resistant S. aureus infection is a global threat. Newer approaches are required to control this organism in the current scenario. P128 is a novel antistaphylococcal chimeric protein under development against S. aureus for human use which derives its bacterial cell wall degrading catalytic endopeptidase domain from ORF56, the Phage K tail-structure associated enzyme. Murein degrading enzymes that are capable of hydrolyzing the various carbohydrate or protein linkages of the peptidoglycan layer bring about cell death. Such enzymes are produced in eukaryotic and prokaryotic organisms [4,5,6]. P128 is a novel chimeric bacteriophage derived protein that is under development in our laboratory for human therapy against antibiotic resistant staphylococci. Efficacy of P128 when administered parenterally, is a key aspect that is currently under investigation
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