Isolation of Anti-Hapten Antibodies by Fluorescence-Activated Cell Sorting of Yeast-Displayed B-Cell Receptor Gene Repertoires

Anti-hapten antibodies are widely used as specific immunochemical detection tools in a variety of clinical and environmental analyses. The sensitivity, however, is limited due to the resulting antibody affinities to the haptens which, in turn, leads to a high demand for specific affinity reagents. A well-established path for the generation of high-affinity antibodies is the immunization of animals with the target antigen. However, the generation of anti-hapten antibodies via immunization remains challenging as small molecule haptens usually possess low immunogenicity and, therefore, must be coupled to an immunogenic and high molecular weight carrier to provoke an immune response.Consequently, antibodies are primarily raised against the carrier molecule or structural features of the hapten-linker fused to the carrier protein. This turns the generation of antibodies which bind exclusively to the hapten structure into a search for the needle in a haystack. In the following chapter, we describe how yeast surface display and high-throughput fluorescence-activated cell sorting can be used to isolate anti-hapten antibodies from a large, yeast-displayed B-cell receptor gene library derived from immunized animals. For this, we describe in detail the preparation of protein-hapten conjugates, the immunization procedure, and the subsequent screening process. Moreover, we provide a simple flow cytometry protocol that allows for a rapid analysis of the enriched clones toward free hapten binding.