[Recombinant design and expression of human three-domain antibody against BoNTa].

VH and Vkappa genes were amplified from human ScFv B17 specific against botulinum neurotoxin serotype A (BoNTa). Gene sequence encoding 5'-terminal 12 amino acid of heavy chain constant region CH1, as a linker, linked VH and Vkappa to construct a new three-domain antibody molecule VH/Vkappa. VH/Vkappa was expressed at high level over 34% of total host cell proteins in E. coli. Recombinant protein were purified up to 95% by affinity column. As a result, recombinant VH/Vkappa could recognize and bind specific to BoNTa in ELISA. However, comparing with its parent ScFv, VH/Vkappa has higher relative affinity and stability.