Phage ESCape: an emulsion-based approach for the selection of recombinant phage display antibodies.

Antibody phage display technology is a well established method for selecting specific antibodies against desired targets. Although phage display is the most widely used method of generating synthetic antibodies, it is laborious to perform multiple selections with different antigens simultaneously using conventional manual methods. We have developed a novel approach to the identification and isolation of cells secreting phage encoding desirable antibodies that utilizes compartmentalization and Fluorescence Activated Cell Sorting (FACS). This method, termed Phage Emulsion, Secretion, and Capture (ESCape), allows us to individually query each phage against the antigen. Here, we demonstrate the ability of Phage ESCape to identify novel scFvs against a phosphopeptide epitope of the Her2 kinase from a phage display library containing approximately 10(8) synthetically diversified antibodies. Clones were analyzed by monoclonal phage ELISA against the Her2 phosphopeptide, and positive binders were identified as those showing a signal greater than 3-fold higher than the background signal against an irrelevant antigen. We isolated antibodies recognizing the phosphopeptide in a single round of selection by Phage ESCape, but the strength and specificity of the hits was substantially improved when the library was pre-enriched by a single round of biopanning. By minimizing the selection rounds required for phage display and using a FACS machine as a 'colony picker' equivalent, Phage ESCape has the potential to dramatically increase the throughput of in vitro screening methods.