Our long-term goal is to develop new vaccination strategies in humans with an emphasis on anti-tumor immunity. The unique ability of dendritic cells (DC) to induce and sustain immune responses makes them optimal candidates for vaccination protocols. Yet, optimal strategies for the delivery of antigen(s) to human DCs still need to be identified. Recent studies demonstrate that DCs efficiently capture apoptotic cells and present MHC class I and class II-restricted epitopes. Thus, the use of tumor cell bodies as source of antigens in DC-based vaccination offers a novel strategy that allows presentation of both CTL and T helper epitopes. Our own studies show that naive CD8+ T cells can be induced to differentiate into melanoma-specific CTL when primed by DCs loaded with killed allogeneic melanoma cells. Yet, T cells require several rounds of stimulation for the tumor specific responses to be established. Therefore, it is of great importance to identify the means of increasing tumor cell immunogenicity. Because the purified heat shock proteins, gp96 and hsp7O, have been shown to play a critical role in tumor rejection in mice, it is likely that the expression level as well as the type of hsps expressed in tumor cell bodies will determine their immunogenicity. We propose that: Immunogenicity of tumor cell bodies is determined by their expression of heat shock proteins and we propose to analyze the immunogenicity of cell bodies from lines induced to overexpress hsp70 or gp96. Using human malignant melanoma as a model we will: (1) Determine whether loading DCs with tumor bodies overexpressing hsp70 or gp96 enhances TAA presentation to melanoma specific T cell lines/clones. (2) Determine whether loading DCs with tumor bodies overexpressing hsp 70 or gp96 enhances their capacity to prime naive T cells. (3) Determine whether loading DCs with tumor bodies overexpressing hsp70 or gp96 skews their capacity to prime CD4 T cells. (4) Determine whether hsp70 and gp96 account for the differential priming activity of cell bodies. These studies will permit us to produce an altered melanoma cell line, with enhanced immunogenicity, that will be used to generate tumor cell bodies to load onto DCs for vaccination protocols.
Showing the most recent 10 out of 21 publications
