Epitope mapping of monoclonal antibodies against N-domain of carcinoembryonic antigen

Abstract

Monoclonal antibodies (MoAbs) against N-domain of carcinoembryonic antigen (CEA), C249, K348, K1338, and K1444, that inhibit CEA-mediated cell adhesion, did not crossreact with nonspecific cross-reacting antigen (NCA). To determine amino acid sequences involved in the adhesion, epitopes of the MoAbs were mapped with recombinant NCAs carrying CEA-NCA chimeric N-domain. The data showed that the epitopes of C249, K1338, K1444 are located within the regions 1–32, 1–32, and 33–59 of CEA, respectively, and that two discrete regions 1–32 and 60–93 may be related to the epitope of K348. Comparison of amino acid sequences between CEA and NCA suggested that four residues (21, 27–29), eight residues (21, 27–29, 66, 78, 79, 89), and three residues (43, 44, 46) are important for recognition by C249 (or K1338), K348, and K1444, respectively. These residues seem to participate in the cell adhesion mediated by CEA.