Abstract: Background: Microbe-binding peptides (MBPs) are currently being investigated to address the problem of antimicrobial resistance. Strategies enhancing their antimicrobial activity have
been developed, including peptide dimerization. Here, we present an alternative approach based on
peptide polymerization, yielding hapten-labelled polymeric MBPs that mediate tagging of bacteria
with anti-hapten antibodies, for enhanced immune recognition by host phagocytes.
Methods: C-terminally amidated analogs of the bacterial-binding peptide IIGGR were synthesized,
with or without addition of cysteine residues at both N- and C-termini. Peptides were subjected to
oxidizing conditions in a dimethyl-sulfoxide/wate... More
Abstract: Background: Microbe-binding peptides (MBPs) are currently being investigated to address the problem of antimicrobial resistance. Strategies enhancing their antimicrobial activity have
been developed, including peptide dimerization. Here, we present an alternative approach based on
peptide polymerization, yielding hapten-labelled polymeric MBPs that mediate tagging of bacteria
with anti-hapten antibodies, for enhanced immune recognition by host phagocytes.
Methods: C-terminally amidated analogs of the bacterial-binding peptide IIGGR were synthesized,
with or without addition of cysteine residues at both N- and C-termini. Peptides were subjected to
oxidizing conditions in a dimethyl-sulfoxide/water solvent system, and polymerization was demonstrated using SDS-PAGE. Peptides were then N-terminally labelled with a trinitrophenyl (TNP)
group using trinitrobenzene sulfonate (TNBS). Binding to representative bacteria was demonstrated by ELISA using anti-TNP antibodies and was quantified as half-maximal effective concentration (EC50). Minimum inhibitory concentration (MIC) and concentration yielding 50% hemolysis
(H50) were estimated. Neutrophil phagocytic index was determined for TNP-labelled polymeric bacterial-binding peptide (Pbac) with anti-TNP antibodies and/or serum complement.
Results: Polydisperse Pbac was synthesized. EC50 was lower for Pbac than for the corresponding
monomeric form (Mbac), for both Staphylococcus aureus ATCC 29213 and Escherichia coli
ATCC 25922. MIC and H50 were >250µg/mL for both Pbac and Mbac. A complement-independent
increase in neutrophil phagocytic index was observed for E. coli treated with TNP-labelled Pbac in
conjunction with anti-TNP antibodies.
Conclusion: Our data suggest that hapten-labelled polymeric bacterial-binding peptides may easily
be produced from even crude synthetic oligopeptide precursors, and that such bacterial-binding peptides in conjunction with cognate anti-hapten antibodies can enhance immune recognition of bacteria by host phagocytes.
