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Vaccine. 2012 Sep 7;30(41):5949-55. doi: 10.1016/j.vaccine.2012.07.037. Epub 2012 Jul 27.

Prevention and synergistic control of Ph(+) ALL by a DNA vaccine and 6-mercaptopurine.

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Department of Pediatrics, Universität zu Lübeck, UKSH, Campus Lübeck, Germany.


Although the outcome of patients with acute lymphoblastic leukemia (ALL) has been improved continuously by chemotherapy and tyrosine kinase inhibitors, prognosis of patients with Philadelphia chromosome positive (Ph(+)) ALL still remains poor. Since further intensification of chemotherapy is limited by toxic side effects and patients with high risk of transplant-related mortality are not eligible for allogeneic stem cell transplantation new treatment strategies are urgently needed for the prevention of Ph(+) ALL relapse. There is increasing evidence that the immune system plays an essential role for the eradication or immunologic control of remaining leukemia cells. We developed several DNA-based vaccines encoding a BCR-ABL(p185) specific peptide and GM-CSF, and CD40-L, IL-27 or IL-12 and evaluated the preventive and therapeutic efficacy against a lethal challenge of syngeneic Ph(+) ALL in Balb/c mice. In vivo cell depletion assays and cytokine expression studies were performed and the efficacy of the DNA vaccine was compared with 6-mercaptopurine (6-MP) alone and the combination of the DNA vaccine and 6-MP. Preventive immunization with the vaccine BCR-ABL/GM-CSF/IL-12 and the TLR-9 agonist dSLIM induced an innate and adaptive immune response mediated by NK-cells, CD4(+) T-cells and CD8(+) T-cells leading to a survival rate of 80%. Therapeutic vaccination resulted in a significantly longer leukemia-free survival (40.7 days vs. 20.4 days) and a higher survival rate (56% vs. 10%) compared to chemotherapy with 6-MP. Remarkably, in combination with the vaccine 6-MP acted synergistically and led to 100% survival. These results demonstrate that minimal residual disease of Ph(+) ALL can be significantly better controlled by a combined treatment approach of immunotherapy and chemotherapy. This provides a rationale for improving maintenance therapy in order to reduce the relapse rate in patients with Ph(+) ALL.

[Indexed for MEDLINE]

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