Evaluation of protease resistant synthetic antimicrobial peptides as a new approach methodology to mitigate bacterial growth in ex vivo human platelet concentrates

Abstract

Background - Maintaining the safety of platelet concentrates (PCs) is a significant challenge in transfusion medicine, as room-temperature storage (22°C) increases the risk of transfusion-transmitted bacterial infections (TTBIs). This study evaluates a New Approach Methodology (NAM) for pathogen reduction using two protease-resistant antimicrobial peptides (AMPs), D-CONGA and D-CONGA-Q7.

Materials and methods - PCs were experimentally contaminated with Escherichia coli and Staphylococcus epidermidis. The bactericidal efficacy of the AMPs was assessed at a concentration of 8 µM, which is the minimum inhibitory concentration (MIC) that we established in our previous report for the two bacteria used in this study. To determine the biocompatibility and safety margins, the effects of these peptides (at 8 µM and a 2.5× higher concentration of 20 µM) on in vitro platelet activation, aggregation, and plasma coagulation functions (aPTT) were evaluated.

Results - At 8 µM, both AMPs achieved a 5-log₁₀ reduction in bacterial load within 2-3 hours of treatment. Biocompatibility testing revealed that concentrations up to 20 µM did not negatively impact platelet activation or aggregation potential. While 8 µM and 4 µM concentrations remained compatible with normal clotting activity, the 20 µM dose significantly elevated clotting times; however, this effect was partially reversed through peptide absorption using a cation exchange resin.

Discussion - D-CONGA and D-CONGA-Q7 at a concentration of 8 µM serve as effective bactericidal agents in PCs without compromising essential functional attributes. These findings support the potential of these AMPs as a viable strategy to enhance the safety and quality of stored platelets for transfusion.