THE USE OF DEDICATED PEPTIDE LIBRARIES PERMITS THE DISCOVERY OF HIGH-AFFINITY BINDING PEPTIDES

The motif for peptide binding to monoclonal antibody mAb A16, which is known to be directed against glycoprotein D of Herpes simplex virus t ype 1, was determined using two dedicated peptide libraries. As a star ting point for this study we used an A-16 binding lead sequence, which had previously been obtained from a phage display peptide library (Sc hellekens et al., 1994). Binding studies with different length variant s of this peptide identified a 12mer as a suitable lead compound for o ur library study. Two incomplete dedicated resin-bound synthetic pepti de libraries were generated. Both consisted of 2 X 10(6) 12mers, in wh ich positions were alternately fixed (amino acids identical to the lea d sequence) and random. The libraries were screened with mAb A16 and b eads with binding peptides were sequenced using Edman degradation. Thi s resulted in a unique peptide binding motif, essentially comprising a 7mer core sequence. Comparison of the sequence of the natural epitope with the binding motif revealed that its sequence was identical to th e motif except for one position. Substitution of a methionine in the n atural epitope by a tyrosine or a phenylalanine at that position, as d ictated by the motif, resulted in a peptide with an affinity for bindi ng to mAb A16 about 50 times higher than that of the natural epitope. Thus, if a lead sequence is available, the use of incomplete, dedicate d synthetic peptide libraries provides a fast and powerful tool for th e detection of high affinity peptides.