Contending With Target Unrelated Peptides from Phage Display

Abstract

Copyright: © 2012 Zheng D, et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Bacteriophage (phage) display is a popular technique employed to generate peptides, antibody fragments, or proteins with specificity for any number of desired targets. In phage display, foreign polypeptides are genetically fused to a phage coat protein so that the random polypeptide sequence is exposed on the surface of the virion. Surface exposure of the polypeptide allows for affinity selection in a highthroughput manner to isolate clones that bind the target. The target may be a purified protein, receptor, nucleic acid, carbohydrate, cell, organ, tumor, etc [1-10]. The genotype-phenotype link in phage display technology generates an easy and efficient means of ligand identification. Phage display technology is a deceptively complex procedure, however, with numerous variables that, if not taken into consideration, can lead to the selection of targeting sequences with unintended and/or undesired properties. While it is important to design a rigorous selection protocol aimed at experimental success, it is equally important to share both positive and negative selection results with the scientific community. If results are not shared, each investigator utilizing phage display technology runs the risk of reselecting amino acid sequences selected by others and/or wasting time characterizing unwanted amino acid sequence. Phage display can be described as “ignorance based discovery” or a “blind” process due to the selection method relying upon the affinity of phage possessing the necessary characteristics to bind to the presented target in order to purify/select individual phage clones from a vast library of unknown phage. As a result, when utilizing phage display it is imperative to recognize the intrinsic bias contained in the libraries and inherent in the selection protocol. For example it is known that phage displaying peptides composed of amino acid residues that are incompatible with virion assembly, secretion and/or infection processes are censored [11]. A short list of these biases is presented in (Table1) with corresponding references which describe each issue.