CONSTRUCTION AND PURIFICATION OF DOMAIN-DELETED IMMUNOGLOBULIN VARIANTS OF THE RECOMBINANT CHIMERIC B72.3 (Y1) MONOCLONAL-ANTIBODY

Chimeric antibodies have been produced against a pancarcinomic tumor a ssociated antigen, TAG-72, by fusing the genes for the variable region of mouse MAb B72.3 to the genes for the constant region of human IgG. In our efforts to optimize the pharmacokinetics of plasma clearance a nd the efficiency of tumor localization and penetrance of cB72.3, we h ave now developed truncated versions of immunoglobulin heavy chains. T he domain-deleted antibodies are produced by transfecting cells that p roduce chimeric kappa chains with expression vectors that encode chime ric heavy chains lacking the sequences that encode the C(H)2 domain, C (H)3 domain, or both. Despite the absence of these domains, the transf ectomas secrete H2L2 tetramers with appropriate antigenic specificity. All the domain-deleted immunoglobulins can be purified by chromatogra phy on Protein G Sepharose which binds to a site on the Fab region tha t is retained in the domain-deleted antibodies. The C(H)2C(H)3 domain- deleted immunoglobulin produced in cell culture is analogous in size t o enzymatically produced F(ab')2.