Selection of Non-aggregating VH Binders from Synthetic VH Phage-Display Libraries

The particular interest in V_H antibody fragments stems from the fact that they can rival their “naturally occurring” single-domain antibody (sdAb) counterparts (camelid V_H Hs and shark V_NAR s) with regard to such desirable characteristics as stability, solubility, expression, and ability to penetrate cryptic epitopes and outperform them in terms of less immunogenicity, a much valued property in human immunotherapy applications. However, human V_H s are typically prone to aggregation. Various approaches for developing non-aggregating human V_H s with binding specificities have relied on a combination of recombinant DNA technology and phage-display technology. V_H gene libraries are constructed synthetically by randomizing the CDRs of a single V_H scaffold fused to a gene encoding a phage coat protein. Recombinant phage expressing the resulting V_H libraries in fusion with the pIII protein is propagated in Escherichia coli. Monoclonal phage displaying V_H s with specificities for target antigens are isolated from the libraries by a process called panning. The exertion of stability pressure in addition to binding pressure during panning ensures that the isolated V_H binders are also non-aggregating. The genes encoding the desired V_H s selected from the libraries are packaged within the phage particles, linking genotype and phenotype, hence making possible the identification of the selected V_H s through identifying its physically linked genotype. Here, we describe the application of recombinant DNA and phage-display technologies for the construction of a phage-displayed human V_H library, the panning of the library against a protein, and the expression, purification, and characterization of non-aggregating V_H s isolated by panning.