Vigor F.I. Van Tendeloo

Short-term cultured, interleukin-15 differentiated dendritic cells have potent immunostimulatory properties

BackgroundOptimization of the current dendritic cell (DC) culture protocol in order to promote the therapeutic efficacy of DC-based immunotherapy is warranted. Alternative differentiation of monocyte-derived DCs using granulocyte macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-15 has been propagated as an attractive strategy in that regard. The applicability of these so-called IL-15 DCs has not yet been firmly established. We therefore developed a novel pre-clinical approach for the generation of IL-15 DCs with potent immunostimulatory properties.MethodsHuman CD14+ monocytes were differentiated with GM-CSF and IL-15 into immature DCs. Monocyte-derived DCs, conventionally differentiated in the presence of GM-CSF and IL-4, served as control. Subsequent maturation of IL-15 DCs was induced using two clinical grade maturation protocols: (i) a classic combination of pro-inflammatory cytokines (tumor necrosis factor-α, IL-1β, IL-6, prostaglandin E2) and (ii) a Toll-like receptor (TLR)7/8 agonist-based cocktail (R-848, interferon-γ, TNF-α and prostaglandin E2). In addition, both short-term (2-3 days) and long-term (6-7 days) DC culture protocols were compared. The different DC populations were characterized with respect to their phenotypic profile, migratory properties, cytokine production and T cell stimulation capacity.ResultsThe use of a TLR7/8 agonist-based cocktail resulted in a more optimal maturation of IL-15 DCs, as reflected by the higher phenotypic expression of CD83 and costimulatory molecules (CD70, CD80, CD86). The functional superiority of TLR7/8-activated IL-15 DCs over conventionally matured IL-15 DCs was evidenced by their (i) higher migratory potential, (ii) advantageous cytokine secretion profile (interferon-γ, IL-12p70) and (iii) superior capacity to stimulate autologous, antigen-specific T cell responses after passive peptide pulsing. Aside from a less pronounced production of bioactive IL-12p70, short-term versus long-term culture of TLR7/8-activated IL-15 DCs resulted in a migratory profile and T cell stimulation capacity that was in favour of short-term DC culture. In addition, we demonstrate that mRNA electroporation serves as an efficient antigen loading strategy of IL-15 DCs.ConclusionsHere we show that short-term cultured and TLR7/8-activated IL-15 DCs fulfill all pre-clinical prerequisites of immunostimulatory DCs. The results of the present study might pave the way for the implementation of IL-15 DCs in immunotherapy protocols.

Phenotypic alterations and IL-1β production in CD34+ progenitor- and monocyte-derived dendritic cells after exposure to allergens: a comparative analysis

Abstract. Dendritic cells (DC) have been shown to capture and process antigens and play an initiating role in contact sensitization. Cells with dendritic morphology can be generated in vitro either from CD34+ cord blood cells or from CD14+ peripheral monocytes. The aim of this study was to determine the state of maturation/activation of both populations after exposure to several concentrations of four well-established model allergens (nickel sulfate, eugenol, α-hexylcinnamaldehyde and 2,4,6-trinitrobenzene sulfonic acid) or the irritant sodium dodecyl sulfate. We analyzed the surface expression of CD86, CD83 and HLA-DR and the production of IL-1β. DC from the two sources were generated separately in two laboratories, but challenged using identical test protocols. Using both DC populations it was possible to detect the allergens under investigation, though minor differences regarding effective concentrations were noted. The non-responsiveness of CD34-DC to CIN was probably due to non-optimal concentrations. Ni2+, known as a moderate allergen in vivo, showed the most prominent effect in both cell systems. CD86 expression was the most reliable phenotypic marker for the in vitro identification of allergens. Due to substantial individual variations it was difficult to draw any definite conclusions as to the relevance of IL-1β production as an activation endpoint. We conclude that both test systems are able to respond to allergens, but CD34-DC must be exposed to higher concentrations to demonstrate significant phenotypic changes. On the other hand, Mo-DC from only some of the donors reacted to allergens, in contrast to CD34-DC, which responded to allergens irrespective of the donor, thus necessitating the use of Mo-DC cultures from several blood donors.

Vaccination thérapeutique à base de cellules dendritiques contre la leucémie aiguë myéloïde

The long-term outlook for adult patients with acute myeloid leukemia (AML) remains dismal. The main reason for this state of affairs lies in the fact that the majority of AML patients will eventually relapse, even after obtaining complete remission following front-line chemotherapy. Relapses are generally attributed to the persistence of a small number of chemotherapy-resistant leukemic (stem) cells, a condition known as minimal residual disease (MRD). The eradication of MRD, with the eventual aim of reducing the risk of relapse, therefore represents a high-priority goal of modern AML therapy. It is now well established that the immune system plays a crucial role in the defense against AML. This knowledge has fuelled the development of immune-based approaches to control MRD and, ultimately, to prevent relapse. One of the promising strategies that have emerged in this regard involves the use of dendritic cells for therapeutic vaccination. This review article aims to introduce the reader into the conceptual and practical aspects of DC-based vaccination for AML. Next, we will review the first clinical results obtained with this immunotherapeutic approach in AML patients. Finally, we will briefly reflect on the potential place of DC vaccination in the future therapy of AML.

Vaccination thérapeutique à base de cellules dendritiques contre la leucémie aiguë myéloïdeDendritic cell-based therapeutic vaccination for acute myeloid leukemia

The long-term outlook for adult patients with acute myeloid leukemia (AML) remains dismal. The main reason for this state of affairs lies in the fact that the majority of AML patients will eventually relapse, even after obtaining complete remission following front-line chemotherapy. Relapses are generally attributed to the persistence of a small number of chemotherapy-resistant leukemic (stem) cells, a condition known as minimal residual disease (MRD). The eradication of MRD, with the eventual aim of reducing the risk of relapse, therefore represents a high-priority goal of modern AML therapy. It is now well established that the immune system plays a crucial role in the defense against AML. This knowledge has fuelled the development of immune-based approaches to control MRD and, ultimately, to prevent relapse. One of the promising strategies that have emerged in this regard involves the use of dendritic cells for therapeutic vaccination. This review article aims to introduce the reader into the conceptual and practical aspects of DC-based vaccination for AML. Next, we will review the first clinical results obtained with this immunotherapeutic approach in AML patients. Finally, we will briefly reflect on the potential place of DC vaccination in the future therapy of AML.