A practical kinetic model for efficient isolation of useful antibodies from phage display libraries

To isolate phages displaying a practical and useful antibody with a high kon value and/or a low koff value from phage display antibody libraries, we developed a rational strategy based on a kinetic model. In the model, the recovery of a phage displaying an antibody after a round of biopanning is expressed as a function of five parameters, the apparent association rate constant of the phage antibody to the immobilized antigen (kon′), the apparent dissociation rate constant of the phage antibody from the immobilized antigen (koff′), the effective antigen concentration (C), the time for the binding process (tb) and the time for the washing process (tw). An optimum set of operating parameters (C, tb and tw) for isolating phages displaying an antibody with a high kon value was designed based on the model. Three rounds of biopanning were carried out under the designed conditions, against a phage library in which the hypervariable regions of an original antibody were randomized. All isolated phages displayed an antibody with a higher kon value and one displayed an antibody with a 30-fold greater kon value than that of the original antibody. Experimental conditions which improve the efficiency of conventional off-rate selections are also described.