Isolation of monoclonal antibody fragments from phage display libraries

Techniques developed over the past 20 years for the display of foreign peptides and proteins on the surfaces of filamentous bacteriophages have been a major driving force in the rapid development of recombinant antibody technology in recent years. With phage display of antibodies as one of its key components, recombinant antibody technology has led to the development of an increasing number of therapeutic monoclonal antibodies. Antibody gene libraries are fused to a gene encoding a phage coat protein. Recombinant phage expressing the resulting antibody libraries in fusion with the coat protein are propagated in Escherichia coli. Phage displaying monoclonal antibodies with specificities for target antigens are isolated from the libraries by a process called panning. The genes encoding the desired antibodies selected from the libraries are packaged within the phage particles, linking genotype and phenotype. Here, we describe the application of this technology to the construction of a phage-displayed single-domain antibody (sdAb) library based on the heavy chain antibody repertoire of a llama, the panning of the library against a peptide antigen and the expression, purification, and characterization of sdAbs isolated by panning.