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T-cell tolerance to tumor associated antigens is commonly found in cancer patients. Dendritic cells are required to induce tumor-specific immunity because dendritic cells (DCs) can efficiently capture and present tumor antigens to result in the expansion and activation of tumor-specific cytotoxic T cells. We have studied ways of using adenoviral vectors for the simultaneous in vivo activation and loading of dendritic cells (DCs) with tumor associated antigens (TAA) continuously over a 10 day period. We found that the subcutaneous injection of an adenoviral vector (Ad-sig-TAA/ecdCD40L) which can secrete a fusion protein composed of a tumor associated antigen (TAA) and the extracellular domain (ecd) of the CD40 ligand (CD40L) could induce an antigen specific immune response against cancer cells brearing the TAA for up to one year. By using LDH release cytotoxicity assays, ELISOPT assays, and tetramer staining, we showed that subcutaneous injections of the Ad-sig-TAA/ecdCD40L vector increased the levels of TAA specific splenic T cells up to 250 fold, using the E7 foreign viral HPV antigen and the self MUC-1 TAA which is overexpressed on neoplastic epithelial cells. These injections induced a T cell dependent immune response for over a year which could prevent the growth of at least 5 X 105 TAA bearing cancer cells in 100% of the injected mice. These studies indicated that the Ad-sig-TAA/ecdCD40L vector injections were inducing antigen specific memory cells. In human MUC-1 transgenic mice which were transgenic for the human MUC-1 (hMUC-1) gene, and therefore anergic to the hMUC-1 antigen, vaccination with the Ad-sig-hMUC-1/ecdCD40L vector resulted in induction of an immune response to the hMUC-1 antigen positive tumor cells which overcame the anergy to the hMUC-1 antigen which exists in hMUC-1.Tg transgenic mice. The induction of the immune response was HLA restricted, was mediated by CD 8+ T cells, and involved activation of proliferation signal transduction pathways in the antigen specific T cells. No cytokine boosts were required to break tolerance to the TAA in 100% of the treated animals. These findings suggest that the Ad-sig-TAA/ecdCD40L vector injections may be of value in the treatment of the many epithelial malignancies in which the human MUC-1 gene is overexpressed.

[Proc Amer Assoc Cancer Res, Volume 45, 2004]