Construction and Expression of Chimeric Antibodies by a Simple Replacement of Heavy and Light Chain V Genes into a Single Cassette Vector

ABSTRACT

A novel vector pMH-gpt, which is proved useful for cloning mouse immunoglobulin heavy and light chain V genes and for expressing mouse-human chimeric antibody, was constructed. The vector contains human genomic C_γ 1 and C_κ genes, cloning sites for immunoglobulin V region genes, murine Ig promoters, a human Ig heavy chain enhancer, and the selection marker gene Eco-gpt. Because V_H and V_κ genes can be cloned into a single vector, a chimeric antibody gene is easily constructed by this simple insertion procedure.

The usefulness of the vector was confirmed by construction of two mouse–human chimeric antibodies. Mouse monoclonal antibody (MAb) 196-14 recognizes the ovarian cancer-associated antigen (CA125), and MoAb 2-18 reacts with carcinoembryonic antigen (CEA). Mouse–human chimeric 196-14 and 2-18 antibodies were readily constructed and efficiently produced in a mouse myeloma cell line by utilizing the vector. Both chimeric antibodies retained binding activity to their respective antigens. In biodistribution and immunoscintigraphy studies, specificity of radiolabeled chimeric 196-14 antibody was identical to that of its murine counterpart and significant accumulation at the tumor site was observed. The pMH-gpt vector is useful for constructing and producing mouse–human chimeric antibodies.