Screening of Phage-Expressed Antibody Libraries by Capture Lift

Cloning and expression of functional antibody fragments (Fabs) in bacteria and on the surface of filamentous phage has revolutionized the processes by which antibodies (Abs) are discovered and engineered. Cloning, expression, and screening efficiencies of phage systems permit the characterization of large numbers of Abs (>10⁶ ). For example, using immobilized antigen (Ag), specific Abs can be rapidly enriched from large populations of Fabs displayed on the surface of filamentous phage (1 ). However, the selection methods are typically biased toward the enrichment of the highest affinity Fabs displaying the slowest dissociation rates because of prolonged incubation times and multiple washing steps. Thus, a significant number of unique clones displaying low or intermediate affinities to diverse epitopes may be lost while enriching higheraffinity clones to potentially less interesting dominant epitopes. An optimal screening system would permit the rapid characterization of all clones present in the library.