The long-term goal of this proposal is the development of immunotherapy strategies that are based on eliciting immune responsiveness to a self antigen, carcinoembryonic antigen (CEA), that is widely expressed on human colon, breast, and lung carcinomas. As a first step towards accomplishing this goal, mice transgenic for human CEA have been prepared as a model for investigating CEA tolerance and the effects that initiating or introducing immune responsiveness to CEA have on normal tissue function and tumor growth. Preliminary studies have shown that with respect to the tissue distribution pattern of CEA expression and their antigen tolerance these CEA transgenic mice closely resemble humans. In the first aim, T cell tolerance to CEA will be studied in both the T helper and cytotoxic cell compartment. Following immunization with soluble CEA or antigen-expressing cells, lymphocyte transformation, cytokine release, anti-hapten antibody formation, and delayed hypersensitivity tests will measure T cell responsiveness. For the second aim, B cell tolerance to CEA will be examined. Immunogens consisting of helper-independent CEA conjugates or cytokine fusion proteins will be used to stimulate antibody formation. The binding, potency, and class properties of elicited antibodies will be determined. In the third aim, the roles of humoral and cellular immune responses to CEA in mediating destruction of tumor cells in vivo will be analyzed using syngeneic murine tumors transfected with CEA. Protection against tumor growth will be studied following immunization with CEA- expressing fibroblasts along with bacterial adjuvant. Possible mechanisms of tumor eradication will be pursued using in vivo lymphocyte depletion and adoptive transfer, and in vitro assays of T cell effector activity, antibody specificity and nature, and antibody-dependent cellular cytotoxicity. Immunization with cell vaccine or soluble antigen will be used to bias either a cellular or humoral response to CEA to dissect further their roles in mediating tumor destruction. As part of the above aims, the specificity of anti-CEA responses that appear with respect to CEA cross-reactive antigens will be established. For the final aim, the therapeutic properties of anti-CEA cytotoxic T cells derived from nontransgenic mice will be studied in transgenic animals following adoptive transfer. This model for adoptive therapy is proposed as a means to circumvent requirement for breaking tolerance and to control possible autoimmune reactions. Studies under this aim will define the immunodominant CEA epitopes using peptides with predicted class I binding motifs or by isolation of naturally processed peptide. In all studies, the possible appearance of autoimmune reactions accompanying anti-CEA responsiveness will be characterized.
