B/PI-derived synthetic peptides: synergistic effects in tethered bactericidal and endotoxin neutralizing peptides

Abstract

Human neutrophil bactericidal protein (B/PI) is known for its ability to kill bacteria and to neutralize the action of endotoxin. Short lininear peptides derived from residues 80–109 have been synthesized and their bactericidal and endotoxin neutralizing activities have been assayed. A series of ‘walk-through’ decapeptides, overlapping 3 to 4 residues, indicates that endotoxin neutralizing and partial bactericidal activities can be localized within the N- and C-terminal portions, respectively, of the 80–109 sequence. Bactericidal activity toward Pseudomonas aeruginosa was localized in central peptides of the walk-through series and greatest in peptide 90–99. By using longer peptides, residues 86–104 and 82–108, both bactericidal and endotoxin neutralizing activities are significantly enhanced. Bactericidal activity of peptide 82–108 is now only 6-fold less than that of parent B/Pl and 9-fold more potent than peptide 86–104. The 82–108 peptide was 7-fold more active at endotoxin neutralization than 86–104 but showed less enhanced activity, being approx. 470-times less active than B/PI. Cyclized 82–108 peptide retained bactericidal activity but did not improve in capacity to neutralize endotoxin.