Construction of a human antibody domain (VH) library

Highly diverse antibody (Fab or scFv) libraries have become vital sources to select antibodies with high affinity and novel properties. Combinatorial strategies provide efficient ways of creating antibody libraries containing a large number of individual clones. These strategies include the reassembly of naturally occurring genes encoding the heavy and light chains from either immune or nonimmune B-cell sources, or introduction of synthetic diversity to either the framework regions (FRs) or the complementarity-determining regions (CDRs) of the variable domains of antibodies. In the late 1980s, the smallest known antigen-binding fragment was identified when a murine VH repertoire was screened for binding to lysozyme. This fragment (approximately 15 kDa), called a "domain antibody", or "dAb", is approximately four times smaller than a Fab and half the size of a scFv. Here, we describe the construction of a phage-displayed VH library and an approach to introduce genetic diversity in this library, where both diverse human CDRs and synthetic CDRs are combined into a single-domain (VH) framework.