Cell-specific peptide binding by human neutrophils

Analysis of peptide binding to human neutrophils (PMN) using phage display techniques has revealed cell-specific motifs reactive with the PMN surface. Phage libraries displaying either linear 9-mer or cyclic 10-mer and 6-mer peptides were incubated with normal human neutrophils followed by elution o f bound phage with low pH (pH 2.2) and non-ionic detergent. Three rounds of selection generated several related peptide sequences that bound with high avidity to PMN. Using the linear 9-mer library, PMN-binding phage expresse d peptides with the motif (G/A)PNLTGRW. The binding of phage hearing this m otif was highly specific since no binding was observed on lymphocytes, fibr oblasts, epithelial, or endothelial cells. Functional assays revealed that phage bearing the sequence FGPNLTGRW induced a pertussis toxin-sensitive in crease in PMN cytosolic calcium analogous to that observed with G(alpha I) coupled receptors. Other prominent motifs identified included phage bearing the consensus DLXTSK(M/L)X(V/I/L), where X represents a nonconserved posit ion. Phage with this motif bound exclusively to a sub population of human P MN that comprised approximately 50% of the total and did not elicit a calci um response. The binding of such phage to PMN was prevented by co-incubatio n with competing peptides displaying identical or similar sequences (IC50 r ange from 0.6 mu mol/L to 50 mu mol/L for DLXTSK and GPNLTG, respectively). We speculate that these techniques will be useful in identifying functiona l cell-specific binding motifs and contribute to the development of new the rapeutic and diagnostic strategies in human disease. (C) 1999 by The Americ an Society of Hematology.