Gene-Modified Tumor Vaccine with Therapeutic Potential Shifts Tumor-Specific T Cell Response from a Type 2 to a Type 1 Cytokine Profile

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Abstract
Vaccination with a poorly immunogenic/nonimmunogenic tumor fails to protect the host from a subsequent challenge with the same tumor. The mechanisms underlying the failure of these tumors to sensitize therapeutic T cells are not clearly understood, but the inability of host T cells to recognize tumor has been implicated. In this study, vaccination with the poorly immunogenic B16BL6-D5 (D5 H-2b) tumor fails to generate therapeutic T cells from the tumor vaccine-draining lymph nodes (TVDLN) in our adoptive immunotherapy model. However, if vaccination is performed with an allogeneic MHC class I gene (H-2 Kd)-modified tumor, the T cells obtained from the TVDLN are therapeutic after activation with anti-CD3 and IL-2. Lymph nodes (LN) draining both D5 and D5-Kd tumor vaccines contained increased numbers of cells with reduced expression of L-selectin (L-selectinlow/−) compared with naive LN. This implies that vaccination led to sensitization of T cells even in LN draining the unmodified D5 tumor. L-selectinlow/− cells from D5-Kd, but not D5, TVDLN were therapeutic in our animal model. No antitumor activity was seen in the high level L-selectin T cells. L-selectinlow/− T cells exhibited tumor-specific cytokine release that was type 2 (IL-4, IL-10) following vaccination with native D5 and type 1 (IFN-γ) following vaccination with gene-modified D5-Kd. Our data suggest that the failure of unmodified D5 to generate therapeutic T cells is not due to an inability to recognize tumor Ags, but, rather, to the induction of an immune response that is ineffective in mediating tumor regression, i.e., immune deviation.