Selection and expression of recombinant single domain antibodies from a hyper-immunized library against the hapten azoxystrobin

► A llama was immunized with a model hapten molecule azoxystrobin (MW 403). ► The apparent affinity of the convIgG to azoxystrobin was greater than to the HcIgG. ► A VHH hyper-immunized phage-displayed library was constructed and panned. ► Two VHHs (A27 and A85) were isolated with the IC50 values of 7.2 and 2.0 µM, respectively. ► A85 is one of the highest affinity VHHs that has yet been isolated against a hapten.