MIMICRY OF A CARCINOEMBRYONIC ANTIGEN EPITOPE BY A RAT MONOCLONAL ANTIIDIOTYPE ANTIBODY

Anti-idiotype antibodies (Ab2) that immunologically mimic tumor antige ns are auspicious agents for the active immunization of cancer patient s. We have developed W12, a rat monoclonal IgG(1) Ab2 to MN-14, a muri ne anti-carcinoembryonic antigen (CEA) monoclonal antibody. W12 is spe cific for MN-14 and does not react with other isotype-matched anti-CEA monoclonal antibodies. Moreover, W12 inhibits the binding between MN- 14 and CEA. Anti-CEA antibodies can be induced by immunization with W1 2 (but not with control rat IgG) in xenogenic animals (mice or rabbits ). Immunoblotting studies indicate that the internal image determinant borne by W12 is conformational and requires the association of the he avy and light chains of the Ab2 molecule. This study indicates that W1 2 is a potential idiotype vaccine in patients with CEA-producing cance rs. (C) 1994 Wiley-Liss, Inc.