Single-domain antibodies (variable domain of the heavy chain of a heavy chain antibody; VHH) are promising reagents for therapeutics and diagnostics because of their stability, cost-effective production and material workability as a small antibody. Currently, general acquisition of a VHH using immunization of camelids is inconvenient from the standpoint of animal protection, cost and the process is time-consuming. Thus, a straightforward and efficient method for screening VHHs against a target molecule is required. In this study, we examined whether in vitro selection of a VHH against a target protein could be performed by a cDNA display method with an artificial VHH library that had the three complementarity-determining regions (CDRs) randomized by chemical synthesis. The results revealed that a particular VHH against survivin, which is a member of the inhibitor of apoptosis family, was selected with affinity in the range of 10-7 to 10-8 M. The in vitro selection of a VHH using cDNA display with an artificial synthesized library without animal immunization was shown to be effective for rapid and inexpensive screening of VHHs against a target protein.
Keywords: In vitro selection; Nanobody; Single-domain antibody; Survivin; VHH; cDNA display.
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