Cell-based tumor vaccines targeting CD4+ T lymphocytes

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Our long-term goal is to develop therapeutic and prophylactic vaccines that induce regression and prevent progression of metastatic ocular melanoma, a disease for which there is no current treatment. To achieve this goal we have designed cell-based vaccines that activate tumor-specific CD4+ T cells, a key cell population that facilities CD8+ T cell-mediated cytotoxicity and memory. The ocular melanoma "MHC II vaccines" consist of tumor cells that are genetically modified to express the costimulatory molecule CD80 and MHC class II alleles that are syngeneic to the tumor-bearing host. If the vaccine cells and the host share MHC I alleles, the vaccines also activate CD8+ T cells. Previous studies in mice demonstrated significant therapeutic efficacy against established primary and spontaneously metastatic cancers. Because the vaccines lack the MHC ll-accessory molecule, Invariant chain (li), which is expressed in all professional antigen presenting cells (ARC), we have hypothesized that the vaccines present novel MHC ll-restricted peptides which are not produced by professional ARC. We have spent years 1-4 of this grant translating the vaccines for human use and have made a series of ocular melanoma vaccines that express C080 plus a variety of HLA-DR alleles in the absence of li. These vaccines activate human PBMC to endogenously synthesized tumor antigens in vitro. During the next grant period we will determine if the basic concept of MHC II vaccines has therapeutic efficacy in human systems and will exploit the mechanistic insight we have gained during the previous grant period to improve vaccine design. We propose four Specific Aims. Aim 1: Determine if MHC II "cocktail" vaccines activate patients' T cells to autologous tumor and if patients are responsive to the vaccines throughout the course of their disease. Aim 2. Determine if ocular melanoma MHC II vaccines prepared from primary tumors, which reside in the immune privileged site of the eye, are more efficacious than vaccines prepared from metastatic tumor cells that reside in the liver, a non-privileged site. Aim 3: Determine if ocular melanoma cells transduced with CD80, the MHC class II transactivator (CIITA), and down-regulated for li activate tumor-specific T cells. Aim 4: Determine if the MHC ll+livaccines produce a novel repertoire of peptides and if ocular melanoma patients' responses are skewed towards the novel peptides.