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

Abstract

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.

Leukemia-associated antigens and their relevance to the immunotherapy of acute myeloid leukemia

“…68 Hence, the presence of CD4 þ T-cell 'helper' epitopes within the larger structure of the antigen is a highly desirable immunogenic property. 69 Antigenic peptides presented by MHC class II molecules are usually longer than peptide fragments bound to MHC class I molecules, the latter typically being nine amino acids in length (nonapeptides).…”

“…25 CD8 þ T cells specific for G250/CAIX [24][25][26][27][28][29][30][31][32] , G250/CAIX 254-262 and RHAMM [165][166][167][168][169][170][171][172][173] are also regularly detected in the peripheral blood of AML patients, with frequencies of 60%, 13% and 47%, respectively. 25 In a series of 15 AML patients, Siegel et al 22 observed spontaneous T-cell immune responses to different HLA-A*0201-restricted T-cell epitopes derived from OFA-iLRP, including iLR1 [59][60][61][62][63][64][65][66][67][68] (6/15) …”

Empowering gamma delta T cells with antitumor immunity by dendritic cell-based immunotherapy

“…49 These data could support the implementation of IL-15 expressing DCs into clinical trials. [54][55][56][57] Impact of DCs on effector functions of gd T cells The two main effector functions of gd T cells which would be desirable in the context of cancer immunotherapy are a direct cytotoxicity toward tumor cells and an immunomodulatory function through the secretion of pro-inflammatory cytokines including IFN-g and TNF-a.…”

Dendritic cells in cancer immunotherapy

“…These are also high on the list of priorities, as MoDC cultured in GM-CSF 1IL-15 are superior in vitro in inducing high-affinity CTL [79,80]. It remains difficult for us to generate a sufficient number of highly standardized DC under these conditions, which is a prerequisite for true GMP production.…”