Using Phage Display to Create Recombinant Antibodies

A variety of phage display technologies have been developed since the approach was first described for antibodies. The most widely used approaches incorporate antibody sequences into the minor coat protein pIII of the nonlytic filamentous phage fd or M13. Libraries of variable gene sequences, encoding either scFv or Fab fragments, are made by incorporating sequences into phagemid vectors. The phagemid is packaged into phage particles with the assistance of a helper phage to produce the antibody display phage. This protocol describes a method for creating a phagemid library. The multiple cloning site (MCS) of the pBluescript KS(–) phagemid vector is replaced by digestion with the restriction enzyme BssHII, followed by the insertion of four overlapping oligonucleotides to create a new MCS within the vector. Next, the 3′ portion of gene III (from M13mp18) is amplified and combined with an antibody sequence using overlap extension PCR. This product is inserted into the phagemid vector to create pPDS. Two helper plasmids are also created from the modified pBluescript vector: pLINK provides the linker between the heavy and light chains, and pFABC provides the CH1 domain of the heavy chain. An antibody cDNA library is constructed from the RNA of interest and ligated into pPDS. The phagemid library is electroporated into Escherichia coli cells along with the VCS-M13 helper phage.