Biopanning of endotoxin-specific phage displayed peptides

Systemic bacterial infections frequently lead to a plethora of symptoms termed “endotoxic shock” or “sepsis.” Characterized by hypotension, coagulation abnormalities, and multiple organ failure, treatment of sepsis still remains mostly supportive. Of the various experimental therapeuticinterventional strategies, neutralization of endotoxin by peptides or proteins is becoming popular recently. Hence, design of endotoxin binding peptides is gaining currency as their structural complexity and mode of recognition of endotoxin precludes mounting of resistance against them by the susceptible bacteria by genetic recombination, mutation, etc. Earlier work from our laboratory had shown that the amphiphilicc ationic peptides are good ligands for endotoxin binding. In this study, we report the results of studies with the 12 selected lipid A binding phage displayed peptides by biopanning of a repertoire of a random pentadecapeptide library displayed on the .lamentous M-13 phage. A comparison of the sequences revealed no consensus sequence between the 12 selected peptides suggesting that the lipid A binding motif is not sequence speci.c which is in accord with the sequence variation seen with the naturally occurring anti-microbial and/or endotoxin binding peptides. Thus, the .exibility of\ud the peptides coupled with their plasticity in recognizing the lipid A moiety, explains their tight binding to ndotoxin. At a structural level, asymmetric distribution of the charged polar residues on one face of the helix and non-polar residues on the opposite face appears to correlate with their activity.\u