Semisynthetic Phage Display Library Construction: Generation of Filtered Libraries

Display of antibody fragments on the surface of M13 filamentous bacteriophages is a well-established approach for the identification of antibodies binding to a target of interest. Here, we describe the second of a three-step method to construct Antibody Libraries for Therapeutic Antibody Discovery (ALTHEA) Gold Plus Libraries. The three-step method involves (1) primary library (PL) construction, (2) filtered library (FL) construction, and (3) secondary library construction. The second step, described here, involves display of the PLs as single-chain variable fragment (scFv) fusions to protein pIII of the M13 phage, as well as heat shock treatment and subsequent selection of well-folded and thermostable scFvs via protein L binding, whereas unstable and defective scFvs are removed by washing steps and centrifugation. The quality of the filtration process is assessed by sequencing clones chosen at random from the FLs. These libraries, enriched with thermostable antibodies, are then ready to be used for the third and final step of the process: generation of secondary libraries.