Leukemia Relapse remains a significant obstacle to the success of allogeneic HSCT, particularly for patients with acute leukemias and MDS transplanted in advanced stages of disease. Adoptive transfer of donor-derived antigen-specific T cells has emerged as a promising approach for the tretment and prevention of life-threatening viral infections post transplant, and may also be used to provide expandable populations of tumoricidal effector T cells to tumor-beariing hosts. In this project, we propose to explore and develop practicable broadly applicable strategies for generating donor-derived T cells that selectively react againstdeterminants differentially expressed on leukemia cells for adoptive immunotherapy to treat or, ultimately, prevent leukemia relapse in the post transplant peeriod. In Aim 1, we propose to develop and evaluate new strategies for rapid generation of WT1 peptide specific T cells from normal transplant donors expressing at least one of a series of common HLA class I or II alleles by in vitro sensitization with a selectable panel of immediately accessible and replenishable artificial antigen presented cells engineered to express critical costimulatory molecules and single class I or class II alleles shared by the donor which have been either loaded with specific WT1 epitopes or a pool of synthetic overlapping pentadecapeptides spanning the WT1 sequence or transduced to express the WT1 protein. These T cells will then be compared with T cells sensitized with autologous, WT1 peptide loaded dendritic cells as to yield, phenotype, peptide-speciflc reactivity and leukemocidal activity. In Aim 2, we will develop and evaluate in vitro generated and selected EBV or CMV virus-specific T cells transduced to also express either a T cell receptor specific for an immunogenic WT1 peptide presented by a prevalent class I HLA allele, or CD19-specific ScFvbased chimeric antigen receptor and evaluate them for their activity against WT1+ and/or CD19+ leukemias and lymphomas and their viral antigen targets. We hypothesize that introduction of a leukemia reactive WT1-specific TCR or CE19-specific CAR will abrogate the risk of transducing alloreactive T cells and may also enhance persistence of dual receptor T cells through ongoing stimulation in vivo by cells expressing latent viral antigens. In Aim 3, we propose to comparatively evaluate WT1 specific and CD19 specific T vcells generated in aims 1 and 2 for their capacity to migrate to, accumulate and persist in and induce regressions of leukemia xenografts in NOD/SCID mice, and to also assess the effects of the WT1 peptide sensitized T cells and T cells expressing transduced receptors on the engraftment and in vivo expansion of normal hematopoietic cells and leukemia blasts in the permissive NOD/SCIDyc