Phase I study of tumor Ag-loaded IL-12 secreting semi-mature DC for the treatment of pediatric cancer

Depletion of endogenous tumor-associated regulatory T cells improves the efficacy of adoptive cytotoxic T-cell immunotherapy in murine acute myeloid leukemia

Tumor-induced immune suppression can permit tumor cells to escape host immune resistance. To elucidate host factors contributing to the poor response of adoptively transferred tumor-reactive cytotoxic T lymphocytes (CTLs), we used a systemic model of murine acute myeloid leukemia (AML). AML progression resulted in a progressive regulatory T-cell (Treg) accumulation in disease sites. The adoptive transfer of in vitro-generated, potently lytic anti-AML-reactive CTLs failed to reduce disease burden or extend survival. Compared with non-AML-bearing hosts, transferred CTLs had reduced proliferation in AML sites of metastases. Treg depletion by a brief course of interleukin-2 diphtheria toxin (IL-2DT) transiently reduced AML disease burden but did not permit long-term survival. In contrast, IL-2DT prevented anti-AML CTL hypoproliferation, increased the number of transferred CTLs at AML disease sites, reduced AML tumor burden, and resulted in long-term survivors that sustained an anti-AML memory response. These data demonstrated that Tregs present at AML disease sites suppress adoptively transferred CTL proliferation, limiting their in vivo expansion, and Treg depletion before CTL transfer can result in therapeutic efficacy in settings of substantial pre-existing tumor burden in which antitumor reactive CTL infusion alone has proven ineffective.

Evaluation of 3 clinical dendritic cell maturation protocols containing lipopolysaccharide and interferon-gamma

Dendritic cells (DCs) are important adjuvants for cancer vaccines. Immature dendritic cells (iDCs) are often produced by the stimulation of peripheral blood monocytes with interleukin (IL)-4 and granulocyte macrophage-colony stimulating factor. For many applications iDCs are treated with cytokines or inflammatory signals to produce mature DCs (mDCs). iDCs are often treated ex vivo with lipopolysaccharide (LPS) and interferon (IFN)-gamma to produce mDCs for clinical therapy. The purpose of this study was to determine if the DC maturation cocktail LPS plus IFN-gamma could be improved by the addition of 2 other DC maturation agents IL-1beta and tumor necrosis factor (TNF)-alpha. Peripheral blood mononuclear cells were collected from 6 healthy subjects. Monocytes were isolated from the peripheral blood mononuclear cell concentrates by elutriation and were incubated for 3 days with granulocyte macrophage-colony stimulating factor and IL-4 to produce iDCs. iDCs from each subject were divided into 3 and were incubated for 24 hours with LPS plus IFN-gamma; LPS, IFN-gamma, plus IL-1beta; or LPS, IFN-gamma, IL-1beta, plus TNF-alpha to produce mDCs. The DCs were compared by measuring the expression of costimulator and antigen presenting molecules (CD80, CD83, CD86, and human leukocyte antigen-DR) by flow cytometry, cytokine production (IL-12p70 and IL-10) by enzyme-linked immunosorbent assay and global gene expression using an oligonucleotide microarray. There were no differences in the expression of costimulatory molecules, human leukocyte antigen-DR and CCR7 and production of IL-12p70 among the mDCs produced with the 3 cocktails. Global gene expression analysis found that the expression of 9576 genes differed between the iDCs and mDCs, but the expression of only 13 differed among the 3 different groups of mDCs. There was no benefit of adding IL-1beta and TNF-alpha to LPS and IFN-gamma to produce mDCs.

Intramembranous fragment of amyloid-beta: A potential immunogen for Alzheimer's disease immunotherapy

Immunotherapy holds great promise for Alzheimer's disease (AD), but meningoencephalitis observed in the first AD vaccination trial, which accompanied T-lymphocytic infiltration, needs to be overcome. This study was aimed to investigate alternative approaches for a safer vaccine to treat AD. We used intramembranous fragment of amyloid-beta (IF-Abeta) to immunize Kunming mice for up to 2.5 months and then evaluated the immunization efficacy and potential adverse effects. Immunization of mice with IF-Abeta plus Freund's adjuvant resulted in moderate levels of Abeta antibodies (IgG), and the anti-sera were able to neutralize Abeta1-42-neurotoxicity in cultured primary cortical neurons. IF-Abeta itself did not show neurotoxicity, and immunization with IF-Abeta did not cause behavioral deficits in Morris water maze or any abnormalities by histological examinations of major organs including the brain. We conclude that vaccination with IF-Abeta may be a potentially safe and effective treatment for AD.

Comparative evaluation of techniques for the manufacturing of dendritic cell-based cancer vaccines

Manufacturing procedures for cellular therapies are continuously improved with particular emphasis on product safety. We previously developed a dendritic cell (DC) cancer vaccine technology platform that uses clinical grade lipopolysaccharide (LPS) and interferon (IFN)-y for the maturation of monocyte derived DCs. DCs are frozen after 6 hrs exposure at a semi-mature stage (smDCs) retaining the capacity to secret interleukin (IL)-12 and thus support cytolytic T-cell responses, which is lost at full maturation. We compared closed systems for monocyte enrichment from leucocyte apheresis products from healthy individuals using plastic adherence, CD14 selection, or CD2/19 depletion with magnetic beads, or counter flow centrifugation (elutriation) using a clinical grade in comparison to a research grade culture medium for the following DC generation. We found that elutriation was superior compared to the other methods showing 36 ± 4% recovery, which was approximately 5-fold higher as the most frequently used adherence protocol (8 ± 1%), and a very good purity (92 ± 5%) of smDCs. Immune phenotype and IL-12 secretion (adherence: 1.4 ± 0.4; selection: 20 ± 0.6; depletion: 1 ±0.5; elutriation: 3.6 ± 1.5 ng/ml) as well as the potency of all DCs to stimulate T cells in an allogeneic mixed leucocyte reaction did not show statistically significant differences. Research grade and clinical grade DC culture media were equally potent and freezing did not impair the functions of smDCs. Finally, we assessed the functional capacity of DC cancer vaccines manufactured for three patients using this optimized procedure thereby demonstrating the feasibility of manufacturing DC cancer vaccines that secret IL-12 (9.4 ± 6.4 ng/ml). We conclude that significant steps were taken here towards clinical grade DC cancer vaccine manufacturing.