Monitoring the Antileukemic Immune Response with an Active Specific Immunization Strategy

Abstract

AbstractAbstract 4354 Background:Donor lymphocyte transfusion (DLT) may induce the graft-versus-leukemia (GVL) effect for patients with AML relapsed after transplant. However, the limited overall efficacy of DLT in clinical practice emphasizes the importance of identifying a specific subgroup of patients who might benefit from this treatment approach. Objective:To monitor the cellular immune response after DLT, we developed an active specific immunization strategy using in vitro generated AML-trained T cells to induce a highly specific antileukemic T-cell response and thus established a novel nonradioactive assay system. Methods:The myeloid blasts derived from five patients with AML relapsed post allogeneic hematopoietic stem cell transplantation (allo-HSCT) were first labeled with CFDA (5,6-carboxyfluorescein diacetate succinimidyl ester). To analyze the growth inhibitory potential of the donor T cells trained by AML cells, the myeloid blasts were induced to proliferate by means of a cytokine cocktail. The T cell mediated growth inhibitory potential was detected after 5 days by flow cytometry and correlated with [3H]-thymidine uptake. Results:Here, we applied a CFDA dye to track the proliferation and expansion of AML blasts in response to the cytokine cocktail in vitro. AML-trained T cells, expressed high levels of the activation markers CD25 and CD69, and were generated to recognize the leukemic progenitor cells and inhibit cytokine-induced leukemic cell proliferation, which is an active specific immunization strategy circumventing the identification of leukemia-associated antigens. The capability of proliferation inhibition of AML-trained T cells evaluated with the nonradioactive, CFDA-based assay provided comparable results with the classic [3H]-thymidine assay. Conclusion:The active specific immunization strategy was realized to monitor the antileukemic immune response measured with radioactive and nonradioactive assay system. Disclosures:No relevant conflicts of interest to declare.