The overall objective of these studies is to develop an effective immunotherapeutic regimen to control neoplastic growth in situations which mimic clinical presentation in human cancer. To date, extracted tumor-specific transplatation antigens (TSTA) from methylcholanthrene (MCA)-induced murine sarcomas of moderate antigenicity used in various combinations with cyclophosphamide and intrasplenically delivered interleukin-2 (IL-2) have reduced neoplastic progression in models of local subcutaneous disease, including retardation of primary outgrowth, augmentation of sinecomitant immunity, eradication of residual disease and amelioration of established disease, and in models of pulmonary metastasis due to artificial or spontaneous, hematogenous dissemination. The proposed studies will test the efficacy of more purified antigens, as well as the benefits of maneuvers to augment immunogenicity, including coupling to monocytes/macrophages or to liposomal carries, as well as cross-linking of TSTA by aggregation, glutaraldehyde, or immobilization on beads. Purification of TSTA epitopes has been achieved by the use of preparative isoelectric focusing, high performance gel permeation chromatography, preparative isotachophoresis and affinity chromatography with monoclonal anti-murine mammary tumor virus antibody. The effects of immunostimulation with muramyl tripeptide in native or liposomal form with treatment in vivo and/or in vitro will be compared and combined with the documented effects of IL-2. The nature of host resistance and effects of TSTA immunotherapy will be dissected by measuring circulating antigen levels, using a monoclonal anit-MCA TSTA antibody, and by expanding sensitized T-cell populations from virgin, immunized or tumor-bearer, syngeneic murine hosts. Expanded T-cell populations, already generated in preliminary studies, will be used for systemic immunotherapy combined with the other agents. In addition, the proposed studies will extend the immunotherapy experiments to a non-immunogenic MCA sarcoma and to epithelial murine colon adenocarcinomas, based on the hypothesis that failure to achieve host resistance during natural in vivo progression is due to insufficient immunogenic antigen presentation, to release of suppressogenic determinants, and/or to a requirement for concomitant immunostimulation. In sum, these experiments will extend the horizons of immunotherapeutic intervention with extracted and purified tumor antigens from models of moderate antigenicity and modest tumor burden, to models of poorly- or non-immunogenic neoplasms present in large body tumor burdens.
