11. Phage Libraries

Summary

Phage display is a technology that has been applied to a wide array of scientific fields, such as therapeutics, diagnostics, imaging agents, affinity media, and vaccine development. In this latter field, this chapter describes how phage display libraries are used as tools to dissect the immune response against foreign pathogens and diseases. Using peptide phage display (PPD), many authors have discovered novel peptides that serve as surrogates for antigens. By selecting PPD libraries against antibodies directed to key epitopes on antigens, small peptides are discovered that bind the antigen-binding site on the selected antibody. When used to immunize animals, these peptides (mimotopes) can mimic the antigen and elicit an immune response against the parental antigen. Besides using synthetic peptides for immunization, many groups have immunized animals directly with the selected peptide(s) on phage and found these vaccines yield a more robust immune response than the peptide alone. In cases where the antigen is not known, many laboratories have discovered the targeted antigens in an immune response by selecting high titer polyclonal sera on phage display libraries (peptide and cDNA). Once the antigen is discovered, PPD is often used to further epitope map the antigen-antibody interaction and also to develop mimotopes to be used as vaccines. This chapter provides examples of each of these applications and highlights how PPD libraries are used for novel vaccine strategies.