Mapping Epitopes by Phage Display

Monoclonal antibodies (mAbs) are valuable biological molecules, serving for many applications. Therefore, it is advantageous to know the interaction pattern between antibodies and their antigens. Regions on the antigen which are recognized by the antibodies are called epitopes, and the respective molecular counterpart of the epitope on the mAbs is called paratope. These epitopes can have many different compositions and/or structures. Knowing the epitope is a valuable information for the development or improvement of biological products, e.g., diagnostic assays, therapeutic mAbs, and vaccines, as well as for the elucidation of immune responses. Most of the techniques for epitope mapping rely on the presentation of the target, or parts of it, in a way that it can interact with a certain mAb. Among the techniques used for epitope mapping, phage display is a versatile technology that allows the display of a library of oligopeptides or fragments from a single gene product on the phage surface, which then can interact with several antibodies to define epitopes. In this chapter, a protocol for the construction of a single-target oligopeptide phage library, as well as for the panning procedure for epitope mapping using phage display is given.