[Replacement of the constant region gene of a novel anti-CEA antibody and characterization of its biological activity].

AIM: To convert the subclass of a novel anti-CEA antibody, C2-45, from IgG4 to IgG1, and to increase its biological activity. METHODS: V(H) and V(kappa); genes were cloned from C2-45(IgG4), then inserted to pAc-kappa-CH3 expression vector which contained the constant region gene of human IgG1. The recombinant gene was transfected to Sf9 insect cells to produce recombinant virus with high titer and obtain recombinant protein. The recombinant protein, in the culture supernatant, designated C2-45 (IgG1), was purified by affinity chromatography, and characterized for the CEA binding specificity and the biological activity of CDC and ADCC. RESULTS: The C2-45 (IgG1), retained the original antigen-binding activity and effectively introduced a specific cytotoxicity of complement and lymphokine-activated killer cells to the CEA-expressing tumor cells. CONCLUSION: The constant region of anti-CEA antibody C2-45 was successfully converted from IgG4 to IgG1, which may be useful for immunotherapy of human CEA-expressing tumors.