Abstract.
Diabodies are recombinant, dimeric, antibody-based molecules composed of two non-covalently associated single-chain antibody fragments that bind to an antigen in a divalent manner. In an attempt to develop more effective therapeutic molecules against scorpion venoms, we designed a diabody derived from monoclonal antibody 9C2, which neutralizes the toxicity of scorpion neurotoxin AahI in mammals. The recombinant diabody produced in the periplasm of Escherichia coli was purified to homogeneity in a single step by protein L-agarose affinity chromatography. It was functional, and possessed a high binding affinity to AahI (8 × 10–11M). The bivalence of the diabody was confirmed by size-exclusion chromatography, isoelectrofocussing and electron microscopic observations. Finally, the diabody showed high thermal stability in serum and demonstrated protective activity when injected intraperitonally in mice experimentally envenomed with toxin AahI. In conclusion, the diabody format gives the 9C2molecule advantageous properties that are particularly important for potential clinical applications in the treatment of envenomations.
Keywords: Key words. Diabody; scFv; immunotherapy; scorpion; toxin; antibody engineering.
Footnotes
Received 23 December 2002; received after revision 28 January 2003; accepted 4 February 2003
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