cDNA cloning and sequencing of a novel monoclonal antibody to carcinoembryonic antigen and construction of a mouse/human chimeric antibody

Background: Mouse monoclonal antibody F33-104 recognizes an epitope which is present on the carcinoembryonic antigen (CEA) molecule but not on the other CEA family member proteins, and which seems to be of potential value for immunotherapy of CEA-expressing cancers. However, an inherent problem in its in vivo application is the human anti-mouse antibody response. Materials and Methods: To reduce its immunogenicity in humans, we cloned and sequenced the V region genes of heavy and light chains of F33-104 using the reverse transcription-polymerase chain reaction method, and then constructed a mouse/human chimeric antibody, designated Ch F33-104, by fusing the F33-104 V-H and Vkappa genes to human Cgamma1 and Ckappa genes, respectively. The resulting Ch F33-104 was expressed in non-Ig-producing myeloma cells and characterized for its CEA binding specificity and the tumor cell killing activity. Results: Ch F33-104 specifically bound to CEA-expressing tumor cells and revealed a potent antibody-dependent cell-mediated cytotoxicity with human lymphokine-activated killer cells as effectors against the CEA-expressing tumor cells. Conclusion: This mouse/human chimeric antibody could therefore be a candidate for cancer immunotherapy of CEA-positive cancers.