DESIGN OF A POTENT NOVEL ENDOTOXIN ANTAGONIST

Background. Bactericidal permeability increasing protein (BPI) binds t o and neutralizes lipopolysac-charide (LPS, endotoxin). Small syntheti c peptides based on the amino acid sequence of the LPS binding domain of BPI neutralize LPS, albeit inefficiently. Although the LPS binding domain of native BPI possesses a beta-turn secondary structure, this s tructure is not present in small derivative peptides. The purpose of t his study was to determine whether the addition of a p-tnm to a BPI-de rived peptide is associated with more potent endotoxin antagonism. Met hods. We generated a hybrid peptide (BU3) on the basis of (1) a portio n of the LPS binding domain from BPI and (2) amino acids known to init iate a beta-turn. BU3 folds with a beta-turn, and we tested its effect s on LPS neutralisation and LPS-induced tumor necrosis factor-alpha se cretion, comparing it with BPI-derived peptide BG22 that lacks a beta- turn and to an irrelevant peptide (BG16). Results. Compared with BG22, BU3 demonstrated enhanced LPS neutralization and inhibition of LPS-in duced tumor necrosis factor-alpha secretion in vitro and a similar dim inution of endotoxemia and tumor necrosis factor-alpha secretion in a murine model of endotoxemia. Conclusions. These data demonstrate the p otential for enhancing the biologic activity of a BPI-derived peptide endotoxin antagonist via manipulation of its conformational structure.