Optimization of Host Cell-Compatible, Antimicrobial Peptides Effective against Biofilms and Clinical Isolates of Drug-Resistant Bacteria

Abstract

High Resolution Image Download MS PowerPoint Slide Here, we describe the continued synthetic molecular evolution of a lineage of host-compatible antimicrobial peptides (AMP) intended for the treatment of wounds infected with drug-resistant, biofilm-forming bacteria. The peptides tested are variants of an evolved AMP called d -amino acid CONsensus with Glycine Absent ( d -CONGA), which has excellent antimicrobial activities in vitro and in vivo . In this newest generation of rational d -CONGA variants, we tested multiple sequence–structure–function hypotheses that had not been tested in previous generations. Many of the peptide variants have lower antibacterial activity against Gram-positive or Gram-negative pathogens, especially variants that have altered hydrophobicity, secondary structure potential, or spatial distribution of charged and hydrophobic residues. Thus, d -CONGA is generally well tuned for antimicrobial activity. However, we identified a variant, d -CONGA-Q7, with a polar glutamine inserted into the middle of the sequence, that has higher activity against both planktonic and biofilm-forming bacteria as well as lower cytotoxicity against human fibroblasts. Against clinical isolates of Klebsiella pneumoniae, innate resistance to d -CONGA was surprisingly common despite a lack of inducible resistance in Pseudomonas aeruginosa reported previously. Yet, these same isolates were susceptible to d -CONGA-Q7. d -CONGA-Q7 is much less vulnerable to AMP resistance in Gram-negative bacteria than its predecessor. Consistent with the spirit of synthetic molecular evolution, d -CONGA-Q7 achieved a critical gain-of-function and has a significantly better activity profile.

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