SURFACE DISPLAY OF ANTIBODIES

To screen antibody libraries that contain many millions of different c lones, a selection system is required with an efficiency comparable to that of the immune system. This can be achieved by displaying antibod ies on the surface of microorganisms containing the antibody's gene, a nalogous to the expression of the IgM antigen receptor on the surface of unactivated B-lymphocytes. Specific clones can then be selected usi ng immobilized antigens. The minor coat protein of filamentous phages, pIII, which initiates the infection of E. coli by binding to their F- pili, and the major coat protein, pVIII, have been used as carriers fo r displaying antibodies on the phage surface. Recombinant antibodies h ave also been targeted to the cell surface of bacteria by fusing them with outer membrane components derived from lipoproteins, OmpA and an IgA protease. However, only the pIII system has been routinely used fo r screening antibody libraries. Here we describe the various antibody surface display systems and the screening of antibody libraries genera ted from the gene repertoire of lymphocytes and by gene synthesis. Fin ally, we have made a short comparison of the bacterial production of F abs versus single chain antibodies (scFv).