Prevention and synergistic control of Ph(+) ALL by a DNA vaccine and 6-mercaptopurine.
ABSTRACT 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.
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ABSTRACT: We sought to amplify the immune response to polynucleotide immunization through co-delivery of complementary DNA (cDNA) encoding a cytokine or co-stimulatory molecule to enhance antigen presentation. In the context of intramuscular immunization, we examined co-delivery of cDNAs for B7-1 and human carcinoembryonic antigen (CEA) within separate plasmids or a dual plasmid with two independent expression cassettes. Intramuscular delivery of the dual expression plasmid produced anti-CEA antibody responses and antitumor effects superior to those generated by plasmid DNA encoding CEA alone. However, co-delivery of cDNAs encoding B7-1 and CEA in the form of two separate plasmids produced no augmentation. The importance of single plasmid delivery suggests the effectiveness of this strategy is contingent upon co-expression of B7-1 and CEA within the same cell. The success of cutaneous polynucleotide immunization by particle bombardment is thought to derive largely from the presence of Langerhans cells within the skin. We hypothesized that co-delivery of plasmid DNA encoding granulocyte-macrophage colony stimulating factor (GM-CSF) by particle bombardment would enhance the antigen presenting capacity of Langerhans cells at the inoculation site similar to its effects in vitro. Augmentation of CEA-specific lymphoblastic transformation and antibody response was observed when plasmid GM-CSF (pGM-CSF) was administered 3 days prior to each dose of plasmid DNA encoding CEA. These strategies for augmentation of immune response to polynucleotide immunization should be applicable to a wide variety of antigenic targets including infectious agents and other tumor-associated antigens.Gene Therapy 02/1996; 3(1):67-74. · 4.32 Impact Factor
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ABSTRACT: Philadelphia chromosome-positive acute lymphoblastic leukemia (Ph+ ALL) is a highly aggressive malignancy caused by the bcr-abl translocation oncogene. To explore alternative treatments for Ph+ ALL we tested gene-modified cell vaccines in the BALB/c-derived BM185 leukemia model. We compared the efficacy of BM185 cell vaccine expressing CD80 alone or in combination with IL-2 or GM-CSF. Mice injected with viable BM185 leukemia cells modified to express CD80 and GM-CSF (BM185/CD80+GM-CSF) showed the highest leukemia rejection rates. Cell vaccines consisting of irradiated BM185/CD80+GM-CSF cells administered subcutaneously stimulated a potent cytotoxic T lymphocyte (CTL) response against parental BM185. Histological examination of the vaccination site showed a large concentration of immune cells. Administration of the BM185/CD80+GM-CSF cell vaccine before intravenous challenge with parental cells caused strong inhibition of leukemia development. Vaccination after subcutaneous challenge with BM185 cells caused efficient elimination of leukemia promoting 40-60% long-term survival rates. The immunization efficacy of the BM185/CD80+ GM-CSF cell vaccine was directly correlated with the percentage of cells expressing the transgenes. In all, this preclinical study shows that leukemia cell vaccines coexpressing CD80 and GM-CSF can potentially be explored for immunotherapy in Ph+ ALL patients.Human Gene Therapy 10/1999; 10(13):2109-22. · 4.02 Impact Factor
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ABSTRACT: Childhood Philadelphia chromosome positive (Ph(+)) acute lymphoblastic leukemia (ALL) has a poor prognosis. Because leukemia cell burden is reduced but not eradicated by polychemotherapy, improved treatment strategies should enhance those immune mechanisms responsible for the maintenance of complete remission. The aim of this study was to evaluate the protection of mice challenged with the syngeneic Ph(+) ALL cell line BM185 using genetically modified leukemia cell vaccines and immunomodulating oligonucleotides. Experimental Design: Because retroviral vectors are ineffective at transducing nondividing primary cells from human hematopoietic malignancies, we first evaluated nonviral techniques (electroporation and ballistic transfer) using minimalistic immunogenically defined gene expression vectors to generate B7.1 or granulocyte macrophage colony-stimulating factor (GM-CSF)-expressing BM185 cells. Subsequently, protective vaccination experiments with these cells were performed in a leukemia challenge mouse model. Electroporation yielded a high transfection rate (82.6% for B7.1) with moderate GM-CSF secretion/1 x 10(6) cells (228 pg), whereas ballistic transfer led to a lower transfection rate (30.9%) with high GM-CSF secretion (614 pg). Secondly, we immunized mice with B7.1/interleukin 2- or B7.1/GM-CSF-expressing BM185 cell vaccines. We observed a better protection of mice that received the B7.1/GM-CSF vaccine compared with these receiving the B7.1/interleukin 2 vaccine. Protection was additionally enhanced by application of a double stem-loop immunomodulating oligonucleotide containing CpG motifs. Our data indicate that immunization with B7.1/GM-CSF-expressing cell vaccines generated by electroporation and application of double stem-loop immunomodulating oligonucleotide protected mice against a murine Ph(+) ALL challenge. Ultimately, this approach may also lead to clinical benefit in patients with Ph(+) ALL.Clinical Cancer Research 09/2003; 9(8):3142-9. · 7.84 Impact Factor