The recent focus for improving immunotherapy has been to develop potent vaccination strategies to elicit tumor-specific T cells that could recognize and eliminate cancer cells. The challenge of this approach is to generate an immune response against self-antigens on the tumor cell consisting of sufficient numbers of tumor-specific T cells with adequate activation so they will be tumoricidal. Experiments in Dr. Hong-Ming Hu's laboratory in a mouse model of melanoma clearly demonstrated that the inability of the immune system to recognize weak self-tumor antigens can be overcome with a novel vaccination strategy that involves depletion of lymphocytes and vaccination during reconstitution when homeostatic mechanisms are coordinating an expansion of T cells. These naive T cells are more sensitive to the self-antigens on the mouse tumor resulting in a skewing of the T-cell repertoire. This experimental model requires the induction of lymphopenia, a tumor vaccine and reconstitution with naive T cells. Using this vaccination strategy, established metastases were rejected and mice were cured of their cancer. Similar results were achieved whether lymphocyte depletion was accomplished with radiation or chemotherapy. For this reason, we have chosen to use fludarabine, a drug that is used to treat lymphoid malignancies but has profound effects on lymphocytes, to render patients lymphopenic at the time of vaccination. The vaccine that will be used in this study is the modified gp100 peptide, g209-2M, plus Montanide ISA 51 and KLH. Our Institute has extensive prior experience with the g209-2M peptide vaccine and we have clearly defined the immune responses to it.
The specific aims of this project are to assess the toxicity and immune effects of this vaccine with reconstitution after the induction of lymphopenia by fludarabine in patients with metastatic melanoma. The induction of a peptide-specific T cell response will be measured by HLA-A2/gp100 tetramers and by cytokine flow cytometry of pre- and post-vaccine peripheral blood cells stimulated with gp100 peptides and KLH. Two different dosing schedules of fludarabine will be tested to determine if the lower dose achieves similar effects and could be safely used in the adjuvant setting in future trials. PBMC will be assayed monthly for induction of immune responses.
| Meijer, Sybren L; Dols, Annemieke; Jensen, Shawn M et al. (2007) Induction of circulating tumor-reactive CD8+ T cells after vaccination of melanoma patients with the gp100 209-2M peptide. J Immunother 30:533-43 |
