Ribosome display and affinity maturation: from antibodies to single V-domains and steps towards cancer therapeutics

Protein affinity maturation using molecular evolution techniques to produce high-affinity binding proteins is an important step in the generation of r eagents for cancer diagnosis and treatment. Currently, the most commonly us ed molecular evolution processes involve mutation of a single gene into com plex gene repertoires followed by selection from a display library. Fd-bact eriophage are the most popular display vectors, but are Limited in their ca pacity for library presentation, speed of processing and mutation frequency . Recently, the potential of ribosome display for directed molecular evolut ion was recognised and developed into a rapid and simple affinity selection strategy using ribosome complexes to display antibody fragments (scFv). Ri bosome display and selection has the potential to generate and display larg e Libraries more representative of the theoretical optima for naive reperto ires (10(14)). Even more important is the application of ribosome display f or the affinity maturation of individual proteins by rapid mutation and sel ection cycles. These display strategies can apply to other members of the i mmunoglobulin superfamily; for example single V-domains which have an impor tant application in providing specific targeting to either novel or refract ory cancer markers. We discuss the application of ribosome display and sele ction in conjunction with variable domain (CTLA-4) libraries as the first s tep towards this objective and review affinity maturation strategies for in vitro ribosome display systems. (C) 2001 Elsevier Science BN: All rights r eserved.