The major goal of this research effort is to design, construct and generate novel recombinant immunological reagents for the diagnosis and therapy of human cancers. Several hybridoma cell lines have been developed in this laboratory that produce monoclonal antibodies (MAbs) selectively reactive with carcinoma associated antigens. These include MAbs against carcinoembryonic antigen (CEA), tumor associated glycoprotein (TAG)-72, a high-molecular weight mucin present on a variety of carcinomas, and MAb D612, which is reactive with a 48 kD antigen expressed on the surface of normal and malignant gastrointestinal epithelium. In ongoing clinical trials, the anti-TAG-72 MAbs, B72.3 and CC49, D612 and an anti-CEA MAb, COL-1, have shown various degrees of potential for being developed into diagnostic and therapeutic reagents. However, the usefulness of murine MAbs for in vivo diagnosis and therapy is limited because of their immunogenicity. To reduce this potential problem we have developed mouse- human chimeric (c) MAbs, including cB72.3 (gamma1), using recombinant DNA techniques. In an effort to optimize the pharmacokinetics of plasma clearance and to maximize the efficiency of localization of, and penetration into, tumors we have developed novel chimeric immunoglobulin variants; these include aglycosylated cB72.3 (gamma1) MAb and constant region domain-deleted variants of cB72.3 (gamma1). In comparison with the cB72.3 MAb, the CH2 domain-deleted cMAb demonstrated a faster clearance rate and a more rapid tumor targeting. For second generation anti-TAG-72 MAbs, the heavy and light chain genes of MAb CC49 and CC83 have been cloned, sequenced and inserted into retroviral vectors. Recently, the cCC49 (gamma1) has been expressed and purified. We have also developed a single gene enoded Ig molecule which has retained effector functions. We have also developed a cD612 MAb which has been expressed and secreted by a human T cell line. The secreted immunoglobulin retained its antigen- binding properties and its ability to mediate ADCC against human tumor cells. To our knowledge, this is the first demonstration of the production of an IgG by human T cells and opens the possibility of a therapeutic approach in which T-cells secrete humanized anti-tumor MAb capable of mediating ADCC at the tumor site.
