Identification of model peptides as affinity ligands for the purification of humanized monoclonal antibodies by means of phage display

A proof-of-principle study was initiated to determine whether phage-display technology could be used to identify peptides as leads in the customizatio n of ligands for affinity chromatography and to identify a peptide or pepti domimetic for use as a Protein A alternative in the affinity purification o f monoclonal antibodies. The constant region of humanized anti-Tac (HAT), p repared by pepsin digestion and receptor-affinity chromatography, was used as the target for phage display in this study. As such, 20 phage-derived pe ptide sequences were identified from four rounds of biopanning with two lin ear phage-display libraries (7-mer, containing 100 copies of 2 x 10(9) sequ ences and 12-mer, containing 70 copies of 1.4 x 109 sequences). Five peptid es were synthesized for use as affinity ligands, based on sequence homology to Protein A, sequence redundancy, and amino acid motifs. The best HAT bin ding immobilized peptide was EPIHRSTL-TALL. The best-fit analysis of this p eptide sequence with Protein A yielded an alignment well within the Fc bind ing domain of Protein A. These results suggest that phage display can sme a s a tool in the identification of peptides as model ligands for affinity ch romatography. (C) 2001 Published by Elsevier Science B.V.