Construction, Expression, and Characterization of a Novel Human-Mouse Chimeric Antibody, Hm3A4: A Potential Therapeutic Agent for B and Myeloid Lineage Leukemias.

Antibody-targeting therapy has drawn great interests to the hematologists and oncologists. 3A4, a novel antibody recognizing human CD45RA antigen, is a new target molecule for leukemias and holds a therapeutic potential for myeloid lineage leukemias. However, murine antibodies cannot be safely used in patients because of their strong immune reaction, humanization of the antibodies interested will be an important development step for therapeutic purpose. The aim of this study was to engineer the mouse 3A4 and to investigate the biological activity of its chimeric form. The humanized antibody composed of the 3A4 single-chain fragment of variable region and the human IgG1 Fc region, which was named human-mouse chimeric antibody 3A4 (Hm3A4). The function and biological activities of Hm3A4 were characterized using a variety of biological approaches. The results showed that Hm3A4 retained a strong binding activity to its antigen and could significantly block the binding of parental 3A4 to the antigen. In vitro experiments revealed that Hm3A4 could kill the target cells through complement-dependent cytotoxicity and antibody-dependent cell-mediated cytotoxicity function. In vivo, Hm3A4 showed efficient antileukemia activity outperforming the nontreated mice. In conclusion, the chimeric antibody has an excellent biological activity after humanization and holds targeting therapeutic potential for myeloid leukemia, which warrants further development of this agent.