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

Reconfiguring the immune system to target cancer: Therapies based on T cells, cytokines, and vaccines

Over the years, extensive research has been dedicated to performing in-depth analysis of cancer to uncover the intricate details of its nature - including the types of cancer, causative agents, stimulators of disease progression, factors contributing to poor prognosis, and efficient therapies to restrict the metastatic aggressiveness. This chapter highlights the mechanisms through which different arms of the host immune system - namely cytokines, lymphocytes, antigen-presenting cells (APCs) -can be mobilized to eradicate cancer. Most malignant tumors are either poorly immunogenic, or are harbored in a highly immuno-suppressive microenvironment. This is why reinforcing the host's anti-tumor defenses, through infusion of pro-inflammatory cytokines, tumor antigen-loaded APCs, and anti-tumor cytotoxic cells has emerged as a viable treatment option against cancer. The chapter also highlights the ongoing preclinical and clinical studies in different malignancies and the outcome of various therapies. Although these methods are not foolproof, and antigen escape variants can still evade or develop resistance to customized therapies, they achieve disease stabilization in several cases when conventional treatments fail. In many instances, combination therapies involving cytokines, T cells, and vaccinations prove more effective than monotherapies. The limitations of the current therapies are also discussed, along with ongoing modifications aimed at improving efficacy.

Establishment of a protocol for rapidly expanding Epstein-Barr-virus-specific cytotoxic T cells with enhanced cytotoxicity

BACKGROUND

Lytic Epstein-Barr virus (EBV) infection plays a major role in the pathogenesis of nasopharyngeal carcinoma (NPC). For patients with recurrent or metastatic NPC and resistant to conventional therapies, adoptive cell therapy using EBV-specific cytotoxic T cells (EBV-CTLs) is a promising option. However, the long production period (around 3 to 4 weeks) and low EBV-CTL purity (approximately 40% of total CD8 T cells) in the cell product limits the application of EBV-CTLs in clinics. Thus, this study aimed to establish a protocol for the rapid production of EBV-CTLs.

METHODS

By culturing peripheral blood mononuclear cells (PBMCs) from EBV-seropositive donors with EBV-specific peptides and interleukin (IL)-2, IL-15, and interferon α (IFN-α) for 9 days, we identified that IL-15 can enhance IL-2-mediated CTL activation and significantly increase the yield of CTLs.

RESULTS

When IFN-α was used in IL-2/IL-15-mediated CTL production from days 0 to 6, the productivity of EBV-CTLs and EBV-specific cytotoxicity significantly were reinforced relative to EBV-CTLs from IL-2/IL-15 treatment. Additionally, IFN-α-induced production improvement of virus-specific CTLs was not only the case for EBV-CTLs but also for cytomegalovirus-specific CTLs.

CONCLUSION

We established a novel protocol to rapidly expand highly pure EBV-CTLs from PBMCs, which can produce EBV-CTLs in 9 days and does not require feeder cells during cultivation.

Functional Heterogeneity of Umbilical Cord Blood Monocyte-Derived Dendritic Cells

Human umbilical cord blood (UCB) represents a unique resource for hematopoietic stem cell transplantation for children and patients lacking suitable donors. UCB harbors a diverse set of leukocytes such as professional APCs, including monocytes, that could act as a novel source for cellular therapies. However, the immunological properties of UCB monocytes and monocyte-derived dendritic cells (MoDCs) are not fully characterized. In this study, we characterized the phenotype and functions of UCB-MoDCs to gauge their potential for future applications. UCB exhibited higher frequencies of platelets and lymphocytes as well as lower frequencies of neutrophils in comparison with adult whole blood. Leukocyte subset evaluation revealed significantly lower frequencies of granulocytes, NK cells, and CD14+CD16- monocytes. Surface marker evaluation revealed significantly lower rates of costimulatory molecules CD80 and CD83 while chemokine receptors CCR7 and CXCR4, as well as markers for Ag presentation, were similarly expressed. UCB-MoDCs were sensitive to TLR1-9 stimulation and presented quantitative differences in the release of proinflammatory cytokines. UCB-MoDCs presented functional CCR7-, CXCR4-, and CCR5-associated migratory behavior as well as adequate receptor- and micropinocytosis-mediated Ag uptake. When cocultured with allogeneic T lymphocytes, UCB-MoDCs induced weak CD4+ T lymphocyte proliferation, CD71 expression, and release of IFN-γ and IL-2. Taken together, UCB-MoDCs present potentially advantageous properties for future medical applications.

Extracellular vesicles of Trypanosoma cruzi and immune complexes they form with sialylated and non-sialylated IgGs increase small peritoneal macrophage subpopulation and elicit different cytokines profiles

American trypanosomiasis, or Chagas disease, is caused by the protozoan parasite Trypanosoma cruzi and is characterized by the presence of cardiac or gastrointestinal symptoms in a large number of patients during the chronic phase of the disease. Although the origin of the symptoms is not clear, several mechanisms have been described involving factors related to T. cruzi and the host immune response. In this sense, the extracellular vesicles (EVs) secreted by the parasite and the immune complexes (ICs) formed after their recognition by host IgGs (EVs-IgGs) may play an important role in the immune response during infection. The aim of the present work is to elucidate the modulation of the immune response exerted by EVs and the ICs they form by analyzing the variation in the subpopulations of small and large peritoneal macrophages after intraperitoneal inoculation in mice and to evaluate the role of the sialylation of the host IgGs in this immunomodulation. Both macrophage subpopulations were purified and subjected to cytokine expression analysis by RT-qPCR. The results showed an increase in the small peritoneal macrophage subpopulation after intraperitoneal injection of parasite EVs, but a greater increase in this subpopulation was observed when sialylated and non-sialylated ICs were injected, which was similar to inoculation with the trypomastigote stage of the parasite. The cytokine expression results showed the ability of both subpopulations to express inflammatory and non-inflammatory cytokines. These results suggest the role of free EVs in the acute phase of the disease and the possible role of immune complexes in the immune response in the chronic phase of the disease, when the levels of antibodies against the parasite allow the formation of immune complexes. The differential expression of interleukins showed after the inoculation of immune complexes formed with sialylated and non-sialylated IgGs and the interleukins expression induced by EVs, demonstrates that the IgG glycosilation is involved in the type of immune response that dominates in each of the phases of the Chagas disease.

In vitro expansion of Wilms' tumor protein 1 epitope-specific primary T cells from healthy human peripheral blood mononuclear cells

Wilms' tumor protein 1 (WT1) is a tumor-associated antigen overexpressed in various cancers. As a self-antigen, negative selection reduces the number of WT1-specific T cell receptors (TCRs). Here, we provide a protocol to generate WT137-45-specific TCRs using healthy human peripheral blood mononuclear cells. We describe the expansion of WT1-specific T cell clones by two consecutive in vitro stimulations with autologous WT137-45-pulsed dendritic cells and peripheral blood lymphocytes. We then detail the detection with human leukocyte antigen/WT137-45 tetramers.

Interleukin 15 in Cell-Based Cancer Immunotherapy

Cell-based cancer immunotherapy, such as chimeric antigen receptor (CAR) engineered T and natural killer (NK) cell therapies, has become a revolutionary new pillar in cancer treatment. Interleukin 15 (IL-15), a potent immunostimulatory cytokine that potentiates T and NK cell immune responses, has demonstrated the reliability and potency to potentially improve the therapeutic efficacy of current cell therapy. Structurally similar to interleukin 2 (IL-2), IL-15 supports the persistence of CD8⁺ memory T cells while inhibiting IL-2-induced T cell death that better maintains long-term anti-tumor immunity. In this review, we describe the biology of IL-15, studies on administrating IL-15 and/or its derivatives as immunotherapeutic agents, and IL-15-armored immune cells in adoptive cell therapy. We also discuss the advantages and challenges of incorporating IL-15 in cell-based immunotherapy and provide directions for future investigation.

Novel IL-15 dendritic cells have a potent immunomodulatory effect in immunotherapy of multiple myeloma

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Culture DCs with GM-CSF + IL-4 + IL-15 (IL-15 DCs) can be shortened for 6 days.

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IL-15 DCs showed high expression levels of costimulatory receptors, IFN-γ and IL-12p70.

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IL-15 DCs showed strong stimulation toward T, CIK and NK cells.

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The activated lymphocytes showed high cytotoxicity against myeloma cells.

Dendritic cells (DCs) are the most potent antigen-presenting cells, and have thus been used in clinical cancer vaccines. However, the effects of DC vaccines are still limited, leading researchers to explore novel ways to make them effective. In this study, we investigated whether human monocyte-derived DCs generated via the addition of interleukin 15 (IL-15) had a higher capacity to induce antigen-specific T cells compared to conventional DCs. We isolated CD14⁺ monocytes from peripheral blood from multiple myeloma (MM) patients, and induced immature DCs with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 in the presence or absence of IL-15 for 4–6 days. Then we generated mature DCs (mDCs) with lipopolysaccharide for another 2 days [IL-15 mDCs (6 days), IL-15 mDCs (8 days), and conventional mDCs (8 days)]. IL-15 mDCs (6 days) showed higher expression of MHC I and II, CD40, CD86, and CCR7, and the secretion of IFN-γ was significantly higher compared to conventional mDCs. IL-15 mDCs (6 days) showed superior polarization of naïve T cells toward Th1 cells and a higher proportion of activated T cells, cytokine-induced killer (CIK) cells, and natural killer (NK) cells for inducing strong cytotoxicity against myeloma cells, and lower proportion of regulatory T cells compared to conventional mDCs. These data imply that novel multipotent mDCs generated by the addition of IL-15, which can be cultivated in 6 days, resulted in outstanding activation of T cells, CIK cells and NK cells, and may facilitate cellular immunotherapy for cancer patients.

Anti-Tumor Potency of Short-Term Interleukin-15 Dendritic Cells Is Potentiated by In Situ Silencing of Programmed-Death Ligands

Dendritic cell (DC) vaccines have proven to be a valuable tool in cancer immune therapy. With several DC vaccines being currently tested in clinical trials, knowledge about their therapeutic value has been significantly increased in the past decade. Despite their established safety, it has become clear that objective clinical responses are not yet robust enough, requiring further optimization. Improvements of this advanced therapy medicinal product encompass, among others, regulating their immune stimulating capacity by in situ gene engineering, in addition to their implementation in combination therapy regimens. Previously, we have reported on a superior monocyte-derived DC preparation, including interleukin-15, pro-inflammatory cytokines and immunological danger signals in the culture process. These so-called IL-15 DCs have already proven to exhibit several favorable properties as cancer vaccine. Evolving research into mechanisms that could further modulate the immune response towards cancer, points to programmed death-1 as an important player that dampens anti-tumor immunity. Aiming at leveraging the immunogenicity of DC vaccines, we hypothesized that additional implementation of the inhibitory immune checkpoint molecules programmed death-ligand (PD-L)1 and PD-L2 in IL-15 DC vaccines would exhibit superior stimulatory potential. In this paper, we successfully implemented PD-L silencing at the monocyte stage in the 3-day IL-15 DC culture protocol resulting in substantial downregulation of both PD-L1 and PD-L2 to levels below 30%. Additionally, we validated that these DCs retain their specific characteristics, both at the level of phenotype and interferon gamma secretion. Evaluating their functional characteristics, we demonstrate that PD-L silencing does not affect the capacity to induce allogeneic proliferation. Ultimately designed to induce a durable tumor antigen-specific immune response, PD-L silenced IL-15 DCs were capable of surpassing PD-1-mediated inhibition by antigen-specific T cells. Further corroborating the superior potency of short-term IL-15 DCs, the combination of immune stimulatory components during DC differentiation and maturation with in situ checkpoint inhibition supports further clinical translation.

Research progress on dendritic cell vaccines in cancer immunotherapy

Dendritic cell (DC) vaccines induce specific immune responses that can selectively eliminate target cells. In recent years, many studies have been conducted to explore DC vaccination in the treatment of hematological malignancies, including acute myeloid leukemia and myelodysplastic syndromes, as well as other nonleukemia malignancies. There are at least two different strategies that use DCs to promote antitumor immunity: in situ vaccination and canonical vaccination. Monocyte-derived DCs (mo-DCs) and leukemia-derived DCs (DCleu) are the main types of DCs used in vaccines for AML and MDS thus far. Different cancer-related molecules such as peptides, recombinant proteins, apoptotic leukemic cells, whole tumor cells or lysates and DCs/DCleu containing a vaster antigenic repertoire with RNA electroporation, have been used as antigen sources to load DCs. To enhance DC vaccine efficacy, new strategies, such as combination with conventional chemotherapy, monospecific/bispecific antibodies and immune checkpoint-targeting therapies, have been explored. After a decade of trials and tribulations, much progress has been made and much promise has emerged in the field. In this review we summarize the recent advances in DC vaccine immunotherapy for AML/MDS as well as other nonleukemia malignancies.

Generation of high cross-presentation ability human dendritic cells by combination of interleukin 4, interferon β and GM-CSF

Dendritic cell (DC)-based immunotherapies have been utilized for the treatment of numerous diseases. However, the conventional generation strategies of DCs in vitro require 7 days and these DCs showed an unsatisfactory function, which prompted us to explore new approaches. We found that in vitro culture of human CD14⁺ cells, in the medium containing granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin (IL)-4, as well as interferon β (IFN-β) for 48 h, followed by the maturation stimuli of IL-1β and poly I:C for another 24 h can be differentiated into high cross-presentation ability DCs (G4B-DCs). These DCs express high levels of CD11c, CD86, and HLA-DR, producing a high level of tumor necrosis factor α (TNF-α). Of note, compared with the conventional DCs, G4B-DCs showed a higher ability to promote allogeneic naïve CD4⁺ T cell and CD8⁺ T cell proliferation and interferon (IFN)-γ production. These DCs also have the remarkable ability to induce Flu-M1-specific CD8⁺ T cells. In addition, we found that these G4B-DCs express partially the cDC1 phenotype. These data indicate that G4B-DC is unique and may provide a relatively rapid alternative method for potential clinical use.

Constitutively Activated DAP12 Induces Functional Anti-Tumor Activation and Maturation of Human Monocyte-Derived DC

Dendritic cells (DCs) are professional antigen presenting cells with a great capacity for cross-presentation of exogenous antigens from which robust anti-tumor immune responses ensue. However, this function is not always available and requires DCs to first be primed to induce their maturation. In particular, in the field of DC vaccine design, currently available methodologies have been limited in eliciting a sustained anti-tumor immune response. Mechanistically, part of the maturation response is influenced by the presence of stimulatory receptors relying on ITAM-containing activating adaptor molecules like DAP12, that modulates their function. We hypothesize that activating DAP12 in DC could force their maturation and enhance their potential anti-tumor activity for therapeutic intervention. For this purpose, we developed constitutively active DAP12 mutants that can promote activation of monocyte-derived DC. Here we demonstrate its ability to induce the maturation and activation of monocyte-derived DCs which enhances migration, and T cell stimulation in vitro using primary human cells. Moreover, constitutively active DAP12 stimulates a strong immune response in a murine melanoma model leading to a reduction of tumor burden. This provides proof-of-concept for investigating the pre-activation of antigen presenting cells to enhance the effectiveness of anti-tumor immunotherapies.

IL-15 negatively regulates curdlan-induced IL-23 production by human monocyte-derived dendritic cells and subsequent Th17 response

OBJECTIVE:

In this study, we aimed to assess the effects of long- and short-term IL-15 cytokine exposure of human monocyte-derived curdlan-matured dendritic cells (DCs) on the production of Th17 cell-polarizing cytokine IL-23 and subsequent Th17 cell activation.

METHODS:

Peripheral blood mononuclear cells (PBMCs) were purified using Ficoll-Paque from healthy donors. Monocytes were magnetically selected using CD14 Miltenyi beads and differentiated into DCs with granulocyte-macrophage colony-stimulating factor (GM-CSF) and IL-4 for five days in the presence or absence of IL-15 (100ng/ml) for long-term exposure experiments. Then, DCs were matured with peptidoglycan (PGN), or curdlan for 24 hours. For short-term exposure experiments, IL-15 was added only during maturation of DCs. Then, DCs were characterized concerning the expression of MHC II and costimulatory molecules, production of cytokine subunits IL-23p19, IL-12p40, IL-12p35 and cytokine IL-23 via flow cytometry or real-time qPCR or ELISA. Finally, the phosphorylation of signaling molecules after curdlan stimulation was assessed using phospho-flow assays.

RESULTS:

IL-15 exposure suppressed IL-23 production by DCs. As a result, IL-15-exposed DCs suppressed IL-17 production by allogeneic T cells. Importantly, we observed a reduction in the surface Dectin-1 receptor levels by IL-15-exposed DCs. In line with these observations, curdlan stimulation resulted in reduced phosphorylation of ERK1/2, NF-kB p65 and AKT by human DCs exposed to IL-15 compared with controls. These results may explain why IL-15-exposed DCs produce less IL-23 after maturation with curdlan, which is a ligand of Dectin-1.

CONCLUSION:

Short- or long-term exposure to IL-15 of human DCs during their differentiation or maturation programs DCs against Th17 cell polarization, which suggests that IL-15 availability may affect CD4+ T cell-mediated protective immunity to fungal infections.

NF-κB activation triggers NK-cell stimulation by monocyte-derived dendritic cells

Background:

In therapeutic cancer vaccination, monocyte-derived dendritic cells (moDCs) efficiently activate specific T-cell responses; however, optimizing the activation of innate immune cells could support and improve the antitumor effects. A major disadvantage of moDCs matured with the standard cytokine cocktail (consisting of IL-1β, IL-6, TNFα, and PGE₂) is their inability to secrete IL-12p70. IL-12 prominently activates natural killer (NK) cells, which are crucial in innate antitumor immunity, as they act as helper cells for the induction of a cytotoxic T lymphocyte (CTL) response and are also able to directly kill the tumor.

Methods:

Previously we have shown that triggering the NF-κB pathway in moDCs by transfection of mRNA encoding constitutively active IKKβ (caIKKβ) led to IL-12p70 secretion and improved the dendritic cells’ capability to activate and expand CTLs with a memory-like phenotype. In this study, we examined whether such dendritic cells could activate autologous NK cells.

Results:

moDCs matured with the standard cytokine cocktail followed by transfection with the caIKKβ-RNA were able to activate autologous NK cells, detected by the upregulation of CD54, CD69, and CD25 on the NK cells, their ability to secrete IFNγ, and their high lytic activity. Moreover, the ability of NK-cell activation was not diminished by simultaneous T-cell activation.

Conclusion:

The capacity of caIKKβ-DCs to activate both the adaptive and innate immune response indicates an enhanced potential for clinical efficacy.

Ex vivo dendritic cell generation-A critical comparison of current approaches

Dendritic cells (DCs) are professional antigen-presenting cells, required for the initiation of naïve and memory T cell responses and regulation of adaptive immunity. The discovery of DCs in 1973, which culminated in the Nobel Prize in Physiology or Medicine in 2011 for Ralph Steinman and colleagues, initially focused on the identification of adherent mononuclear cell fractions with uniquely stellate dendritic morphology, followed by key discoveries of their critical immunologic role in initiating and maintaining antigen-specific immunity and tolerance. The medical promise of marshaling these key capabilities of DCs for therapeutic modulation of antigen-specific immune responses has guided decades of research in hopes to achieve genuine physiologic partnership with the immune system. The potential uses of DCs in immunotherapeutic applications include cancer, infectious diseases, and autoimmune disorders; thus, methods for rapid and reliable large-scale production of DCs have been of great academic and clinical interest. However, difficulties in obtaining DCs from lymphoid and peripheral tissues, low numbers and poor survival in culture, have led to advancements in ex vivo production of DCs, both for probing molecular details of DC function as well as for experimenting with their clinical utility. Here, we review the development of a diverse array of DC production methodologies, ranging from cytokine-based strategies to genetic engineering tools devised for enhancing DC-specific immunologic functions. Further, we explore the current state of DC therapies in clinic, as well as emerging insights into physiologic production of DCs inspired by existing therapies.

CD56 Homodimerization and Participation in Anti-Tumor Immune Effector Cell Functioning: A Role for Interleukin-15

A particularly interesting marker to identify anti-tumor immune cells is the neural cell adhesion molecule (NCAM), also known as cluster of differentiation (CD)56. Namely, hematopoietic expression of CD56 seems to be confined to powerful effector immune cells. Here, we sought to elucidate its role on various killer immune cells. First, we identified the high motility NCAM-120 molecule to be the main isoform expressed by immune cells. Next, through neutralization of surface CD56, we were able to (1) demonstrate the direct involvement of CD56 in tumor cell lysis exerted by CD56-expressing killer cells, such as natural killer cells, gamma delta (γδ) T cells, and interleukin (IL)-15-cultured dendritic cells (DCs), and (2) reveal a putative crosstalk mechanism between IL-15 DCs and CD8 T cells, suggesting CD56 as a co-stimulatory molecule in their cell-to-cell contact. Moreover, by means of a proximity ligation assay, we visualized the CD56 homophilic interaction among cancer cells and between immune cells and cancer cells. Finally, by blocking the mitogen-activated protein kinase (MAPK) pathway and the phosphoinositide 3-kinase (PI3K)-Akt pathway, we showed that IL-15 stimulation directly led to CD56 upregulation. In conclusion, these results underscore the previously neglected importance of CD56 expression on immune cells, benefiting current and future immune therapeutic options.

Dendritic Cell-Based Immunotherapy of Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a type of blood cancer characterized by the uncontrolled clonal proliferation of myeloid hematopoietic progenitor cells in the bone marrow. The outcome of AML is poor, with five-year overall survival rates of less than 10% for the predominant group of patients older than 65 years. One of the main reasons for this poor outcome is that the majority of AML patients will relapse, even after they have attained complete remission by chemotherapy. Chemotherapy, supplemented with allogeneic hematopoietic stem cell transplantation in patients at high risk of relapse, is still the cornerstone of current AML treatment. Both therapies are, however, associated with significant morbidity and mortality. These observations illustrate the need for more effective and less toxic treatment options, especially in elderly AML and have fostered the development of novel immune-based strategies to treat AML. One of these strategies involves the use of a special type of immune cells, the dendritic cells (DCs). As central orchestrators of the immune system, DCs are key to the induction of anti-leukemia immunity. In this review, we provide an update of the clinical experience that has been obtained so far with this form of immunotherapy in patients with AML.

Ascophyllan Induces Activation of Natural Killer Cells in Mice In Vivo and In Vitro

Natural marine polysaccharides have demonstrated immune stimulatory effects in both mice and humans. Our previous study compared the ability of ascophyllan and fucoidan to activate human and mouse dendritic cells (DCs). In this study, we further examined the effect of ascophyllan on the activation of mouse natural killer (NK) cells in vivo and in vitro and compared it to that of fucoidan, a well-studied natural marine polysaccharide. Specifically, administration of ascophyllan to C57BL/6 mice increased the number of NK cells in the spleen when compared to the number in PBS-treated mice. Moreover, the number of IFN-γ-producing NK cells and expression of CD69 were markedly upregulated by ascophyllan treatment. Ascophyllan treatment also induced IFN-γ production and CD69 upregulation in isolated NK cells, but did not promote cell proliferation. Finally, ascophyllan treatment increased the cytotoxicity of NK cells against Yac-1 cells. The effects of ascophyllan on NK cell activation were considerably stronger than those of fucoidan. These data demonstrated that ascophyllan promotes NK cell activation both in mice and in vitro, and its stimulatory effect on NK cells is stronger than that of fucoidan.

IL-15 and a Two-Step Maturation Process Improve Bone Marrow-Derived Dendritic Cell Cancer Vaccine

In the last 20 years, dendritic cells (DCs) have been largely used as a platform for therapeutic vaccination in cancer patients. However, despite its proven safety and ability to induce cancer specific immune responses, the clinical benefits of DC-based immunotherapy are currently very limited. Thus, novel approaches are still needed to boost its efficacy. Our group recently showed that squaric acid treatment of antigens is an important adjuvant that can increase vaccine-induced downstream immune responses and therapeutic outcomes. Here we further improved this dendritic cell vaccine formulation by developing a new method for differentiating and maturing DCs from their bone marrow precursors. Our data demonstrate that bone marrow-derived DCs differentiated with GM-CSF and IL-15 and matured with a maturation cocktail in two steps present a more mature and immunogenic phenotype, compared to standard DC preparations. Further suppression of the prostaglandin E₂ pathway achieved even more immunogenic DC phenotypes. This vaccine was more potent at delaying tumor growth, improved animal survival and induced a more immunogenic and Th1-skewed T cell response in an ovarian cancer mouse model. These promising results support future efforts for the clinical translation of this approach.

IL-15 Generates IFN-γ-producing Cells Reciprocally Expressing Lymphoid-Myeloid Markers during Dendritic Cell Differentiation

Recently, interest in IL-15-differentiated cells has increased; however, the phenotypic definition of IL-15-differentiated bone marrow-derived cells (IL-15-DBMCs) is still under debate, particularly the generation of IFN-γ-producing innate cells such as premature NK (pre-mNK) cells, natural killer dendritic cells (NKDCs), interferon-producing killer dendritic cells (IKDCs), and type 1 innate lymphoid cells (ILC1s), all of which are IL-15-dependent. Here, we revisited the immunophenotypic characteristics of IFN-γ-producing IL-15-DBMCs and their functional role in the control of intracellular Mycobacterium tuberculosis (Mtb) infection. When comparing the cytokine levels between bone marrow-derived dendritic cells (BMDCs) and IL-15-DBMCs upon stimulation with various TLR agonists, only the CD11c^int population of IL-15-DBMCs produced significant levels of IFN-γ, decreased levels of MHC-II, and increased levels of B220. Neither BMDCs nor IL-15-DBMCs were found to express DX5 or NK1.1, which are representative markers for the NK cell lineage and IKDCs. When the CD11c^intB220⁺ population of IL-15-DBMCs was enriched, the Thy1.2⁺Sca-1⁺ population showed a marked increase in IFN-γ production. In addition, while depletion of the B220⁺ and Thy1.2⁺ populations of IL-15-DBMCs, but not the CD19⁺ population, inhibited IFN-γ production, enrichment of these cell populations increased IFN-γ. Ultimately, co-culture of sorted IFN-γ-producing B220⁺Thy1.2⁺ IL-15-DBMCs with Mtb-infected macrophages resulted in control of the intracellular growth of Mtb via the IFN-γ-nitric oxide axis in a donor cell number-dependent manner. Taken together, the results indicate that IFN-γ-producing IL-15-DBMCs could be redefined as CD11c^intB220⁺Thy1.2⁺Sca-1⁺ cells, which phenotypically resemble both IKDCs and ILC1s, and may have therapeutic potential for controlling infectious intracellular bacteria such as Mtb.

A cancer vaccine with dendritic cells differentiated with GM-CSF and IFNα and pulsed with a squaric acid treated cell lysate improves T cell priming and tumor growth control in a mouse model

Introduction: Ovarian cancer is one of the most lethal gynecologic cancers. Relapses after remission are common, hence novel strategies are urgently needed. Our group has previously developed a vaccination approach based on dendritic cells pulsed with HOCl-oxidized tumor lysates. Here we investigate the improvement of this vaccine strategy using squaric acid treatment of cancer cells during tumor lysate preparation and by differentiating dendritic cells in the presence of GM-CSF and IFNα.

Methods: Induction of cell death by squaric acid treatment was assessed with propidium iodide (PI) and Annexin V in ID8 tumor cells. High mobility group box 1 (HMGB1) immunogenic status was analyzed using a western blot-based method, as previously described. For immunological tests, ID8 cells expressing ovalbumin (ova-ID8) were treated with squaric acid before cell lysis. DCs prepared with the canonical GM-CSF and IL-4 differentiation cocktail or IFNα and GM-CSF were pulsed with tumor cell lysates and further matured in the presence of IFNγ and LPS (4-DCs and α-DCs respectively). DCs were then used in co-culture assays with ova-specific T cells and IFNγ and IL-4 secretion measured by ELISA. DC phenotypes were characterized by FACS. Finally, DCs were tested in an ovarian cancer mouse model measuring body weight and animal survival.

Results: Squaric acid treatment of mouse ovarian cancer cells induced tumor cell death as well as preserve HMGB1, a crucial Damage-associated molecular pattern (DAMP) signal, in its active reduced form. Squaric acid treatment of ID8-ova cells increased IFNγ and decreased IL-4 production from ova-specific T cells in co-culture experiments, promoting a more immunogenic cytokine secretion pattern. DCs differentiated in the presence of IFNα induced a considerable decrease in IL-4 production compared to canonical 4-DCs, without affecting IFNγ release. DC phenotyping demonstrated a more mature and immunogenic phenotype for IFNα-differentiated DCs. Vaccination in tumor-bearing mice showed that IFNα-differentiated DCs pulsed with squaric acid-treated lysates were the most potent at delaying tumor growth, improving animal survival.

Conclusion: We identified squaric acid as a novel immunogenic treatment of tumor cells for cancer vaccines particularly efficient in prolonging animal survival when used in combination with IFNα-differentiated DCs. These promising results support future efforts for the clinical translation of this approach.

Interleukin-15-Cultured Dendritic Cells Enhance Anti-Tumor Gamma Delta T Cell Functions through IL-15 Secretion

Dendritic cell (DC) vaccination can be an effective post-remission therapy for acute myeloid leukemia (AML). Yet, current DC vaccines do not encompass the ideal stimulatory triggers for innate gamma delta (γδ) T cell anti-tumor activity. Promoting type 1 cytotoxic γδ T cells in patients with AML is, however, most interesting, considering these unconventional T cells are primed for rapid function and exert meaningful control over AML. In this work, we demonstrate that interleukin (IL)-15 DCs have the capacity to enhance the anti-tumoral functions of γδ T cells. IL-15 DCs of healthy donors and of AML patients in remission induce the upregulation of cytotoxicity-associated and co-stimulatory molecules on the γδ T cell surface, but not of co-inhibitory molecules, incite γδ T cell proliferation and stimulate their interferon-γ production in the presence of blood cancer cells and phosphoantigens. Moreover, the innate cytotoxic capacity of γδ T cells is significantly enhanced upon interaction with IL-15 DCs, both towards leukemic cell lines and allogeneic primary AML blasts. Finally, we address soluble IL-15 secreted by IL-15 DCs as the main mechanism behind the IL-15 DC-mediated γδ T cell activation. These results indicate that the application of IL-15-secreting DC subsets could render DC-based anti-cancer vaccines more effective through, among others, the involvement of γδ T cells in the anti-leukemic immune response.

Dendritic cells as cancer therapeutics

The ability of immune therapies to control cancer has recently generated intense interest. This therapeutic outcome is reliant on T cell recognition of tumour cells. The natural function of dendritic cells (DC) is to generate adaptive responses, by presenting antigen to T cells, hence they are a logical target to generate specific anti-tumour immunity. Our understanding of the biology of DC is expanding, and they are now known to be a family of related subsets with variable features and function. Most clinical experience to date with DC vaccination has been using monocyte-derived DC vaccines. There is now growing experience with alternative blood-derived DC derived vaccines, as well as with multiple forms of tumour antigen and its loading, a wide range of adjuvants and different modes of vaccine delivery. Key insights from pre-clinical studies, and lessons learned from early clinical testing drive progress towards improved vaccines. The potential to fortify responses with other modalities of immunotherapy makes clinically effective "second generation" DC vaccination strategies a priority for cancer immune therapists.

Desirable cytolytic immune effector cell recruitment by interleukin-15 dendritic cells

Success of dendritic cell (DC) therapy in treating malignancies is depending on the DC capacity to attract immune effector cells, considering their reciprocal crosstalk is partially regulated by cell-contact-dependent mechanisms. Although critical for therapeutic efficacy, immune cell recruitment is a largely overlooked aspect regarding optimization of DC vaccination. In this paper we have made a head-to-head comparison of interleukin (IL)-15-cultured DCs and conventional IL-4-cultured DCs with regard to their proficiency in the recruitment of (innate) immune effector cells. Here, we demonstrate that IL-4 DCs are suboptimal in attracting effector lymphocytes, while IL15 DCs provide a favorable chemokine milieu for recruiting CD8⁺ T cells, natural killer (NK) cells and gamma delta (γδ) T cells. Gene expression analysis revealed that IL-15 DCs exhibit a high expression of chemokines involved in antitumor immune effector cell attraction, while IL-4 DCs display a more immunoregulatory profile characterized by the expression of Th2 and regulatory T cell-attracting chemokines. This is confirmed by functional data indicating an enhanced recruitment of granzyme B⁺ effector lymphocytes by IL-15 DCs, as compared to IL-4 DCs, and subsequent superior killing of tumor cells by the migrated lymphocytes. Elevated CCL4 gene expression in IL-15 DCs and lowered CCR5 expression on both migrated γδ T cells and NK cells, led to validation of increased CCL4 secretion by IL15 DCs. Moreover, neutralization of CCR5 prior to migration resulted in an important inhibition of γδ T cell and NK cell recruitment by IL-15 DCs. These findings further underscore the strong immunotherapeutic potential of IL-15 DCs.

Comparative study of dendritic cells matured by using IL-1β, IL-6, TNF-α and prostaglandins E2 for different time span

Interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and prostaglandins E2 is considered as the standard cocktail for maturing dendritic cells (DCs). However, the appropriate time span for DC maturation with the standard cocktail remains unclear. The present study aimed to compare the differences between DCs matured with the standard cocktail for 24 and 48 h, respectively, and determine whether 24-h stimulation was sufficient for DC maturation. The findings demonstrated that, compared with DCs matured for 48 h, the levels of cluster of differentiation (CD)80, CD83, CD86 and programmed death-ligand 1 expression in DCs matured for 24 h were relatively lower. However, with the exception of CD80 whose mean fluorescence intensity (MFI) was higher in DCs matured for 48 h, the MFI values of other surface markers were comparable. Notably, the MFI of CD40 was higher in DCs matured for 24 h. In addition, the viability, T cell stimulatory capacity in allogeneic mixed lymphocyte reaction and cytokine production, including IL-12p40, IL-12p70 and IL-10, were all comparable between DCs matured for 24 and 48 h, respectively. These results indicated that 24-h stimulation may be sufficient for DC maturation when using the standard cocktail.

Enhanced stimulation of human tumor-specific T cells by dendritic cells matured in the presence of interferon-γ and multiple toll-like receptor agonists

Dendritic cell (DC) vaccines have been demonstrated to elicit immunological responses in numerous cancer immunotherapy trials. However, long-lasting clinical effects are infrequent. We therefore sought to establish a protocol to generate DC with greater immunostimulatory capacity. Immature DC were generated from healthy donor monocytes by culturing in the presence of IL-4 and GM-CSF and were further differentiated into mature DC by the addition of cocktails containing different cytokines and toll-like receptor (TLR) agonists. Overall, addition of IFNγ and the TLR7/8 agonist R848 during maturation was essential for the production of high levels of IL-12p70 which was further augmented by adding the TLR3 agonist poly I:C. In addition, the DC matured with IFNγ, R848, and poly I:C also induced upregulation of several other pro-inflammatory and Th1-skewing cytokines/chemokines, co-stimulatory receptors, and the chemokine receptor CCR7. For most cytokines and chemokines the production was even further potentiated by addition of the TLR4 agonist LPS. Concurrently, upregulation of the anti-inflammatory cytokine IL-10 was modest. Most importantly, DC matured with IFNγ, R848, and poly I:C had the ability to activate IFNγ production in allogeneic T cells and this was further enhanced by adding LPS to the cocktail. Furthermore, epitope-specific stimulation of TCR-transduced T cells by peptide- or whole tumor lysate-loaded DC was efficiently stimulated only by DC matured in the full maturation cocktail containing IFNγ and the three TLR ligands R848, poly I:C, and LPS. We suggest that this cocktail is used for future clinical trials of anti-cancer DC vaccines.

Immunotherapy: A promising approach to reverse sepsis-induced immunosuppression

Sepsis is defined as life-threatening organ dysfunction caused by dysregulated host responses to infection (Third International Consensus definition for Sepsis and septic shock). Despite decades of research, sepsis remains the leading cause of death in intensive care units. More than 40 clinical trials, most of which have targeted the sepsis-associated pro-inflammatory response, have failed. Thus, antibiotics and fluid resuscitation remain the mainstays of supportive care and there is intense need to discover and develop novel, targeted therapies to treat sepsis. Both pre-clinical and clinical studies over the past decade demonstrate unequivocally that sepsis not only causes hyper-inflammation, but also leads to simultaneous adaptive immune system dysfunction and impaired antimicrobial immunity. Evidences for immunosuppression include immune cell depletion (T cells most affected), compromised T cell effector functions, T cell exhaustion, impaired antigen presentation, increased susceptibility to opportunistic nosocomial infections, dysregulated cytokine secretion, and reactivation of latent viruses. Therefore, targeting immunosuppression provides a logical approach to treat protracted sepsis. Numerous pre-clinical studies using immunomodulatory agents such as interleukin-7, anti-programmed cell death 1 antibody (anti-PD-1), anti-programmed cell death 1 ligand antibody (anti-PD-L1), and others have demonstrated reversal of T cell dysfunction and improved survival. Therefore, identifying immunosuppressed patients with the help of specific biomarkers and administering specific immunomodulators holds significant potential for sepsis therapy in the future. This review focusses on T cell dysfunction during sepsis and discusses the potential immunotherapeutic agents to boost T cell function during sepsis and improve host resistance to infection.

Immune Cells in Cancer Therapy and Drug Delivery

Recent studies indicate the critical role of tumour associated macrophages, tumour associated neutrophils, dendritic cells, T lymphocytes, and natural killer cells in tumourigenesis. These cells can have a significant impact on the tumour microenvironment via their production of cytokines and chemokines. Additionally, products secreted from all these cells have defined specific roles in regulating tumour cell proliferation, angiogenesis, and metastasis. They act in a protumour capacity in vivo as evidenced by the recent studies indicating that macrophages, T cells, and neutrophils may be manipulated to exhibit cytotoxic activity against tumours. Therefore therapy targeting these cells may be promising, or they may constitute drug or anticancer particles delivery systems to the tumours. Herein, we discussed all these possibilities that may be used in cancer treatment.

Pathogen-Associated Molecular Patterns Induced Crosstalk between Dendritic Cells, T Helper Cells, and Natural Killer Helper Cells Can Improve Dendritic Cell Vaccination

A coordinated cellular interplay is of crucial importance in both host defense against pathogens and malignantly transformed cells. The various interactions of Dendritic Cells (DC), Natural Killer (NK) cells, and T helper (Th) cells can be influenced by a variety of pathogen-associated molecular patterns (PAMPs) and will lead to enhanced CD8⁺ effector T cell responses. Specific Pattern Recognition Receptor (PRR) triggering during maturation enables DC to enhance Th1 as well as NK helper cell responses. This effect is correlated with the amount of IL-12p70 released by DC. Activated NK cells are able to amplify the proinflammatory cytokine profile of DC via the release of IFN-γ. The knowledge on how PAMP recognition can modulate the DC is of importance for the design and definition of appropriate therapeutic cancer vaccines. In this review we will discuss the potential role of specific PAMP-matured DC in optimizing therapeutic DC-based vaccines, as some of these DC are efficiently activating Th1, NK cells, and cytotoxic T cells. Moreover, to optimize these vaccines, also the inhibitory effects of tumor-derived suppressive factors, for example, on the NK-DC crosstalk, should be taken into account. Finally, the suppressive role of the tumor microenvironment in vaccination efficacy and some proposals to overcome this by using combination therapies will be described.

IL-15 Superagonist Expands mCD8+ T, NK and NKT Cells after Burn Injury but Fails to Improve Outcome during Burn Wound Infection

Background

Severely burned patients are highly susceptible to opportunistic infections and sepsis, owing to the loss of the protective skin barrier and immunological dysfunction. Interleukin-15 (IL-15) belongs to the IL-2 family of common gamma chain cytokines and stimulates the proliferation and activation of T (specifically memory CD8), NK and NKT cells. It has been shown to preserve T cell function and improve survival during cecal ligation and puncture (CLP)-induced sepsis in mice. However, the therapeutic efficacy of IL-15 or IL-15 superagonist (SA) during infection after burn injury has not been evaluated. Moreover, very few, if any, studies have examined, in detail, the effect of burn injury and infection on the adaptive immune system. Thus, we examined the effect of burn and sepsis on adaptive immune cell populations and the effect of IL-15 SA treatment on the host response to infection.

Methods

Mice were subjected to a 35% total body surface area burn, followed by wound infection with Pseudomonas aeruginosa. In some experiments, IL-15 SA was administered after burn injury, but before infection. Leukocytes in spleen, liver and peritoneal cavity were characterized using flow cytometry. Bacterial clearance, organ injury and survival were also assessed.

Results

Burn wound infection led to a significant decline in total white blood cell and lymphocyte counts and induced organ injury and sepsis. Burn injury caused decline in CD4⁺ and CD8⁺ T cells in the spleen, which was worsened by infection. IL-15 treatment inhibited this decline and significantly increased cell numbers and activation, as determined by CD69 expression, of CD4⁺, CD8⁺, B, NK and NKT cells in the spleen and liver after burn injury. However, IL-15 SA treatment failed to prevent burn wound sepsis-induced loss of CD4⁺, CD8⁺, B, NK and NKT cells and failed to improve bacterial clearance and survival.

Conclusion

Cutaneous burn injury and infection cause significant adaptive immune dysfunction. IL-15 SA does not augment host resistance to burn wound sepsis in mice despite inducing proliferation and activation of lymphocyte subsets.

Generation and Cryopreservation of Clinical Grade Wilms' Tumor 1 mRNA-Loaded Dendritic Cell Vaccines for Cancer Immunotherapy

First described in the 1970s, dendritic cells (DC) are currently subjects of intense investigation to exploit their unique antigen-presenting and immunoregulatory capacities. In cancer, DC show promise to elicit or amplify immune responses directed against cancer cells by activating natural killer (NK) cells and tumor antigen-specific T cells. Wilms' tumor 1 (WT1) protein is a tumor-associated antigen that is expressed in a majority of cancer types and has been designated as an antigen of major interest to be targeted in clinical cancer immunotherapy trials. In this chapter, we describe the generation, cryopreservation, and thawing of clinical grade autologous monocyte-derived DC vaccines that are loaded with WT1 by messenger RNA (mRNA) electroporation. This in-house-developed transfection method gives rise to presentation of multiple antigen epitopes and can be used for all patients without restriction of human leukocyte antigen (HLA) type.

Dendritic Cells as Pharmacological Tools for Cancer Immunotherapy

Although the earliest—rudimentary—attempts at exploiting the immune system for cancer therapy can be traced back to the late 18th Century, it was not until the past decade that cancer immunotherapeutics have truly entered mainstream clinical practice. Given their potential to stimulate both adaptive and innate antitumor immune responses, dendritic cells (DCs) have come under intense scrutiny in recent years as pharmacological tools for cancer immunotherapy. Conceptually, the clinical effectiveness of this form of active immunotherapy relies on the completion of three critical steps: 1) the DCs used as immunotherapeutic vehicles must properly activate the antitumor immune effector cells of the host, 2) these immune effector cells must be receptive to stimulation by the DCs and be competent to mediate their antitumor effects, which 3) requires overcoming the various immune-inhibitory mechanisms used by the tumor cells. In this review, following a brief overview of the pivotal milestones in the history of cancer immunotherapy, we will introduce the reader to the basic immunobiological and pharmacological principles of active cancer immunotherapy using DCs. We will then discuss how current research is trying to define the optimal parameters for each of the above steps to realize the full clinical potential of DC therapeutics. Given its high suitability for immune interventions, acute myeloid leukemia was chosen here to showcase the latest research trends driving the field of DC-based cancer immunotherapy.

Interleukin-15 Dendritic Cells Harness NK Cell Cytotoxic Effector Function in a Contact- and IL-15-Dependent Manner

The contribution of natural killer (NK) cells to the treatment efficacy of dendritic cell (DC)-based cancer vaccines is being increasingly recognized. Much current efforts to optimize this form of immunotherapy are therefore geared towards harnessing the NK cell-stimulatory ability of DCs. In this study, we investigated whether generation of human monocyte-derived DCs with interleukin (IL)-15 followed by activation with a Toll-like receptor stimulus endows these DCs, commonly referred to as "IL-15 DCs", with the capacity to stimulate NK cells. In a head-to-head comparison with "IL-4 DCs" used routinely for clinical studies, IL-15 DCs were found to induce a more activated, cytotoxic effector phenotype in NK cells, in particular in the CD56bright NK cell subset. With the exception of GM-CSF, no significant enhancement of cytokine/chemokine secretion was observed following co-culture of NK cells with IL-15 DCs. IL-15 DCs, but not IL-4 DCs, promoted NK cell tumoricidal activity towards both NK-sensitive and NK-resistant targets. This effect was found to require cell-to-cell contact and to be mediated by DC surface-bound IL-15. This study shows that DCs can express a membrane-bound form of IL-15 through which they enhance NK cell cytotoxic function. The observed lack of membrane-bound IL-15 on "gold-standard" IL-4 DCs and their consequent inability to effectively promote NK cell cytotoxicity may have important implications for the future design of DC-based cancer vaccine studies.

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

Gamma delta (γδ) T cells are the all-rounders of our immune-system with their major histocompatibility complex-unrestricted cytotoxicity, capacity to secrete immunosti-mulatory cytokines and ability to promote the generation of tumor antigen-specific CD8⁺ and CD4⁺ T cell responses. Dendritic cell (DC)-based vaccine therapy has the prospective to harness these unique features of the γδ T cells in the fight against cancer. In this review, we will discuss our current knowledge on DC-mediated γδ T cell activation and related opportunities for tumor immunologists.

Extending the lifespan and efficacies of immune cells used in adoptive transfer for cancer immunotherapies-A review

Cells used in adoptive cell-transfer immunotherapies against cancer include dendritic cells (DCs), natural-killer cells, and CD8⁺ T-cells. These cells may have limited efficacy due to their lifespan, activity, and immunosuppressive effects of tumor cells. Therefore, increasing longevity and activity of these cells may boost their efficacy. Four cytokines that can extend immune effector-cell longevity are IL-2, IL-7, IL-21, and IL-15. This review will discuss current knowledge on effector-cell lifespans and the mechanisms by which IL-2, IL-7, IL-15, and IL-21 can extend effector-cell longevity. We will also discuss how lifespan and efficacy of these cells can be regulated to allow optimal clinical benefits.

STAT3 signaling contributes to the high effector activities of interleukin-15-derived dendritic cells

Dendritic cells (DCs) are important innate and adaptive immune effectors, and have a key role in antigen presentation and T-cell activation. Different lineages of DCs can be developed from hematopoietic progenitors following cytokine signaling, and the various lineages of DCs display distinct morphology, phenotype and functions. There has been limited information on differential cytokine-mediated molecular signaling in DCs. Analyses of surface molecules by flow cytometry and quantitative RNA profiling revealed differences between DCs derived from interleukin-4 (IL-4) versus IL-15 signaling, yet both lineages of DCs exhibited similar levels of surface molecules key to immune activation. Functional assays confirmed that IL-15-derived DCs elicited greater antigen-specific, primary and secondary CD8 and CD4 T-cell responses than did IL-4-derived DCs. Importantly, IL-15 DCs secreted substantial amounts of proinflammatory cytokines, including IL-6, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNFα), which helped polarize a strong T-cell response. Assessment of signaling pathways revealed that IL-15 DCs exhibited a lower levels of activated signal transducer and activator of transcription 5 (STAT5), STAT6 and extracellular signal-regulated kinase 1/2 than IL-4 DCs, but after lipopolysaccharide (LPS)/TNFα treatment, the STAT3 and p38 mitogen-activated protein kinase (MAPK) activities were significantly enhanced in the IL-15 DCs. Surprisingly, contrary to the canonical IL-15-mediated STAT5 signaling pathway in lymphoid cells, IL-15 did not mediate a strong STAT5 or STAT3 activation in DCs. Further analysis using specific inhibitors to STAT3 and p38 MAPK pathways revealed that the STAT3 signaling, but not p38 MAPK signaling, contributed to IFN-γ production in DCs. Therefore, while IL-15 does not promote the STAT signaling in DCs, the increased STAT3 activity after LPS/TNFα treatment of the IL-15 DCs has a key role in their high IFN-γ effector activities.

Preparation of dendritic cells for cancer immunotherapy

Development of new effective method for cancer therapy is one of the most important trends in the modern medicine. Along with surgery, chemotherapy and radiotherapy, induction of an immune response against the tumor cells is a promising approach for therapy of cancer, particularly metastatic, slowly dividing tumors and cancer stem cells. Induction of the antitumor T-cell immune response involves activation of antigen-presenting cells, which can efficiently present the cancer antigens and activate T-lymphocytes. The immune response may be activated by dendritic cells (DC) loaded with tumor antigens, such as tumor-specific proteins, tumor cell lysates, apoptotic or necrotic tumor cells, as well as nucleic acids encoding tumor antigens. Regardless of the selected source of the tumor antigen, preparation of mature DC is a principal step in the development of anticancer vaccines aimed at the induction of the cytotoxic T-cell immune response. Recently, various research groups have proposed several strategies for producing mature DC, differed by the set of agents used. It has been shown that the maturation strategy influences both their phenotype and the ability to induce the immune response. In this review we have analyzed the results of studies on the various strategies of preparation of mature DCs.

Dendritic cells primed with HPV positive cervical tumor lysate are superior to unprimed DCs in migratory capacity and induce a potent Th1 response

In this study, we assessed the efficacy of tumor lysate primed and unprimed monocyte derived mature dendritic cells (DCs) to trigger an effective anti-tumor immune response in cervical cancer patients who tested positive for human papilloma virus (HPV) DNA. Lysate primed and unprimed DCs were assessed for the expression of CD80, CD86, CD40, HLADR and CD83. The ability of DCs to migrate in response to the chemokines CCL19 and 21 as well as their ability to secrete IL12p40 was investigated. Mixed lymphocyte proliferation assays were used to assess DC stimulatory capacity and their ability to generate a Th1 response. Our results showed no difference in phenotypic expression between primed and unprimed DCs but both had significantly increased expression of the activation marker CD83 when compared to immature DCs. Importantly, the primed DCs showed significant (P value=0.03) IL-12p40 secretion and a superior migratory capacity towards CC19 and CCL21 (P value=0.04) compared to unprimed DCs even after cytokine withdrawal. Primed DCs showed superior stimulation of T cell proliferation (allogeneic and autologous) and secretion of IFN gamma (IFN-γ) than the unprimed DCs. Hence whole tumor lysate primed mature DCs could be potent immunotherapeutic adjuvants to standard treatment for cervical cancer.

HPV vaccine stimulates cytotoxic activity of killer dendritic cells and natural killer cells against HPV-positive tumour cells

Cervarix™ is approved as a preventive vaccine against infection with the human papillomavirus (HPV) strains 16 and 18, which are causally related to the development of cervical cancer. We are the first to investigate in vitro the effects of this HPV vaccine on interleukin (IL)-15 dendritic cells (DC) as proxy of a naturally occurring subset of blood DC, and natural killer (NK) cells, two innate immune cell types that play an important role in antitumour immunity. Our results show that exposure of IL-15 DC to the HPV vaccine results in increased expression of phenotypic maturation markers, pro-inflammatory cytokine production and cytotoxic activity against HPV-positive tumour cells. These effects are mediated by the vaccine adjuvant, partly through Toll-like receptor 4 activation. Next, we demonstrate that vaccine-exposed IL-15 DC in turn induce phenotypic activation of NK cells, resulting in a synergistic cytotoxic action against HPV-infected tumour cells. Our study thus identifies a novel mode of action of the HPV vaccine in boosting innate immunity, including killing of HPV-infected cells by DC and NK cells.

Wilms' tumor gene 1 immunotherapy in pelvic gynecological malignancies

Pelvic gynecological malignancies account for 6% of all cancers. In the relapsed state, classical treatments are limited. There is an urgent need for new and personalized treatment. Wilms' tumor gene 1 (WT1) is the most important tumor-associated antigen. Although highly present in gynecological tumors, active immunotherapy against it is still underexplored. This review gives an insight into the importance of WT1 in pelvic gynecological malignancies and the first taken steps into the world of WT1 immunotherapy.

Loading of acute myeloid leukemia cells with poly(I:C) by electroporation

In this chapter, we describe the technique of electroporation as an efficient method to load primary leukemic cells with the double-stranded RNA (dsRNA) analogue, polyriboinosinic polyribocytidylic acid (poly(I:C)), and detail on the delicate freezing and thawing procedure of primary leukemic cells.Electroporation is a non-viral gene transfer method by which short-term pores in the membrane of cells are generated by an electrical pulse, allowing molecules to enter the cell. RNA electroporation, a technique developed in our laboratory, is a widely used and versatile transfection method for efficient introduction of both coding RNA (messenger RNA) and non-coding RNA, e.g., dsRNA and small interfering (siRNA), into mammalian cells. Accurate cell processing and storage of patient material is essential for optimal recovery and quality of the cell product for downstream applications.

Dendritic cell-based immunotherapy for myeloid leukemias

Acute and chronic myeloid leukemia (AML, CML) are hematologic malignancies arising from oncogene-transformed hematopoietic stem/progenitor cells known as leukemia stem cells (LSCs). LSCs are selectively resistant to various forms of therapy including irradiation or cytotoxic drugs. The introduction of tyrosine kinase inhibitors has dramatically improved disease outcome in patients with CML. For AML, however, prognosis is still quite dismal. Standard treatments have been established more than 20 years ago with only limited advances ever since. Durable remission is achieved in less than 30% of patients. Minimal residual disease (MRD), reflected by the persistence of LSCs below the detection limit by conventional methods, causes a high rate of disease relapses. Therefore, the ultimate goal in the treatment of myeloid leukemia must be the eradication of LSCs. Active immunotherapy, aiming at the generation of leukemia-specific cytotoxic T cells (CTLs), may represent a powerful approach to target LSCs in the MRD situation. To fully activate CTLs, leukemia antigens have to be successfully captured, processed, and presented by mature dendritic cells (DCs). Myeloid progenitors are a prominent source of DCs under homeostatic conditions, and it is now well established that LSCs and leukemic blasts can give rise to "malignant" DCs. These leukemia-derived DCs can express leukemia antigens and may either induce anti-leukemic T cell responses or favor tolerance to the leukemia, depending on co-stimulatory or -inhibitory molecules and cytokines. This review will concentrate on the role of DCs in myeloid leukemia immunotherapy with a special focus on their generation, application, and function and how they could be improved in order to generate highly effective and specific anti-leukemic CTL responses. In addition, we discuss how DC-based immunotherapy may be successfully integrated into current treatment strategies to promote remission and potentially cure myeloid leukemias.

The role of IL-15 in gastrointestinal diseases: a bridge between innate and adaptive immune response

IL-15 is a member of the IL-2 family of cytokines whose signaling pathways are a bridge between innate and adaptive immune response. IL-15 is part of the intestinal mucosal barrier, and functions to modulate gut homeostasis. IL-15 has pivotal roles in the control of development, proliferation and survival of both innate and adaptive immune cells. IL-15 becomes up-regulated in the inflamed tissue of intestinal inflammatory disease, such as IBD, Celiac Disease and related complications. Indeed, several studies have reported that IL-15 may participate to the pathogenesis of these diseases. Furthermore, although IL-15 seems to be responsible for inflammation and autoimmunity, it also may increase the immune response against cancer. For these reasons, we decided to study the intestinal mucosa as an 'immunological niche', in which immune response, inflammation and local homeostasis are modulated. Understanding the role of the IL-15/IL-15R system will provide a scientific basis for the development of new approaches that use IL-15 for immunotherapy of autoimmune diseases and malignancies. Indeed, a better understanding of the complexity of the mucosal immune system will contribute to the general understanding of immuno-pathology, which could lead to new therapeutical tools for widespread immuno-mediated diseases.

Interleukin-15 dendritic cells as vaccine candidates for cancer immunotherapy

Owing to their professional antigen-presenting capacity and unique potential to induce tumor antigen-specific T cell immunity, dendritic cells (DCs) have attracted much interest over the past decades for therapeutic vaccination against cancer. Clinical trials have shown that the use of tumor antigen-loaded DCs in cancer patients is safe and that it has the potential to induce anti-tumor immunity which, in some cases, culminates in striking clinical responses. Unfortunately, in a considerable number of patients, DC vaccination is unable to mount effective anti-tumor immune responses and, if it does so, the resultant immunity is often insufficient to translate into tangible clinical benefit. This underscores the necessity to re-design and optimize the current procedures for DC vaccine manufacturing. A new generation of DC vaccines with improved potency has now become available for clinical use as a result of extensive pre-clinical research. One of the promising next-generation DC vaccine candidates are interleukin (IL)-15-differentiated DCs. In this commentary, we will compile the research data that have been obtained by our group and other groups with these so-called IL-15 DCs and summarize the evidence supporting the implementation of IL-15 DCs in DC-based cancer vaccination regimens.

Costimulatory molecules on immunogenic versus tolerogenic human dendritic cells

Dendritic cells (DC) are sentinels of immunity, essential for homeostasis of T cell-dependent immune responses. Both functions of DC, initiation of antigen-specific T cell immunity and maintenance of tissue-specific tolerance originate from distinct stages of differentiation, immunogenic versus tolerogenic. Dependent on local micro milieu and inflammatory stimuli, tissue resident immature DC with functional plasticity differentiate into tolerogenic or immunogenic DC with stable phenotypes. They efficiently link innate and adaptive immunity and are ideally positioned to modify T cell-mediated immune responses. Since the T cell stimulatory properties of DC are significantly influenced by their expression of signal II ligands, it is critical to understand the impact of distinct costimulatory pathways on DC function. This review gives an overview of functional different human DC subsets with unique profiles of costimulatory molecules and outlines how different costimulatory pathways together with the immunosuppressive cytokine IL-10 bias immunogenic versus tolerogenic DC functions. Furthermore, we exemplarily describe protocols for the generation of two well-defined monocyte-derived DC subsets for their clinical use, immunogenic versus tolerogenic.

Fast dendritic cells stimulated with alternative maturation mixtures induce polyfunctional and long-lasting activation of innate and adaptive effector cells with tumor-killing capabilities

The clinical usage of dendritic cells (DC) for tumor immunotherapy still requires improvements. In this study, three alternative maturation mixtures were compared with the cytokine-based gold standard, and the overall interaction of the resulting DC with effector cells from the innate as well as the adaptive immunity was evaluated in healthy donors. Stimulation with the TLR-4 ligand monophosphoryl lipid A together with IFN-γ (alt-2 DC) resulted in DC with the highest levels of costimulatory molecule expression and IL-12p70/IL-10 ratio. Whereas all alternative DC were able to induce NK and γδ T cells to acquire cytotoxic properties and secrete type 1 and proinflammatory cytokines, after both short (20-h)- and long (5-8 d)-time coculture, secretion of IFN-γ by the innate populations was induced in response to alt-2 and alt-1 DC (TNF-α, IFN-α, IFN-γ, IL-1β, poly IC), but not to alt-3 DC (TNF-α, IFN-γ, IL-1β, CL097). Regarding CD8(+) T cell-mediated Ag-specific immune responses, a heterogeneous pattern of responses was obtained among the healthy donors, suggesting rather a competition than a synergy among the different effector cells. Our data promote further evaluation of alt-2 fast DC for translatability into clinical immunotherapy trials, while also fostering the need to identify biomarkers for immune cell responsiveness and tumor susceptibility to be able to select for each patient the best possible DC-based therapy.

Interleukin-15-induced CD56(+) myeloid dendritic cells combine potent tumor antigen presentation with direct tumoricidal potential

Dendritic cells (DCs) are the quintessential antigen-presenting cells of the human immune system and play a prime role in coordinating innate and adaptive immune responses, explaining the strong and still growing interest in their application for cancer immunotherapy. Much current research in the field of DC-based immunotherapy focuses on optimizing the culture conditions for in vitro DC generation in order to assure that DCs with the best possible immunogenic qualities are being used for immunotherapy. In this context, monocyte-derived DCs that are alternatively induced by interleukin-15 (IL-15 DCs) have attracted recent attention due to their superior immunostimulatory characteristics. In this study, we show that IL-15 DCs, in addition to potent tumor antigen-presenting function, possess tumoricidal potential and thus qualify for the designation of killer DCs. Notwithstanding marked expression of the natural killer (NK) cell marker CD56 on a subset of IL-15 DCs, we found no evidence of a further phenotypic overlap between IL-15 DCs and NK cells. Allostimulation and antigen presentation assays confirmed that IL-15 DCs should be regarded as bona fide myeloid DCs not only from the phenotypic but also from the functional point of view. Concerning their cytotoxic activity, we demonstrate that IL-15 DCs are able to induce apoptotic cell death of the human K562 tumor cell line, while sparing tumor antigen-specific T cells. The cytotoxicity of IL-15 DCs is predominantly mediated by granzyme B and, to a small extent, by tumor necrosis factor-α (TNF-α)-related apoptosis-inducing ligand (TRAIL) but is independent of perforin, Fas ligand and TNF-α. In conclusion, our data provide evidence of a previously unappreciated role for IL-15 in the differentiation of human monocytes towards killer DCs. The observation that IL-15 DCs have killer DC capacity lends further support to their implementation in DC-based immunotherapy protocols.

Dendritic cell engineering for tumor immunotherapy: from biology to clinical translation

Dendritic cells (DCs) are the most potent APCs, with the ability to orchestrate a repertoire of immune responses. DCs play a pivotal role in the initiation, programming and regulation of tumor-specific immune responses, as they are poised to take up, process and present tumor antigens to naive or effector T lymphocytes. Although, to an extent, DC-based immunotherapeutic strategies have successfully induced specific anti-tumor responses in animal models, their clinical efficacy has rarely been translated into the clinic. This article attempts to present a complete picture of recent developments of DC-based therapeutic strategies addressing multiple components of tumor immunoenvironment. It also showcases certain practical intricacies in order to explore novel strategies for providing new impetus to DC-based cancer vaccination.

Quality controls in cellular immunotherapies: rapid assessment of clinical grade dendritic cells by gene expression profiling

Cell-based immunotherapies are among the most promising approaches for developing effective and targeted immune response. However, their clinical usefulness and the evaluation of their efficacy rely heavily on complex quality control assessment. Therefore, rapid systematic methods are urgently needed for the in-depth characterization of relevant factors affecting newly developed cell product consistency and the identification of reliable markers for quality control. Using dendritic cells (DCs) as a model, we present a strategy to comprehensively characterize manufactured cellular products in order to define factors affecting their variability, quality and function. After generating clinical grade human monocyte-derived mature DCs (mDCs), we tested by gene expression profiling the degrees of product consistency related to the manufacturing process and variability due to intra- and interdonor factors, and how each factor affects single gene variation. Then, by calculating for each gene an index of variation we selected candidate markers for identity testing, and defined a set of genes that may be useful comparability and potency markers. Subsequently, we confirmed the observed gene index of variation in a larger clinical data set. In conclusion, using high-throughput technology we developed a method for the characterization of cellular therapies and the discovery of novel candidate quality assurance markers.

Complex evaluation of human monocyte-derived dendritic cells for cancer immunotherapy

Dendritic cell (DC) immunotherapy is capable of generating tumour-specific immune responses. Different maturation strategies were previously tested to obtain DC capable of anti-cancer responses in vitro, usually with limited clinical benefit. Mutual comparison of currently used maturation strategies and subsequent complex evaluation of DC functions and their stimulatory capacity on T cells was performed in this study to optimize the DC vaccination strategy for further clinical application. DC were generated from monocytes using granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4, pulsed with whole tumour cell lysate and then matured with one of five selected maturation strategies or cultured without additional maturation stimulus. DC were characterized with regard to their surface marker expression, cytokine profiles, migratory capacity, allogeneic and autologous T cell stimulatory capacity as well as their specific cytotoxicity against tumour antigens. We were able to demonstrate extensive variability among different maturation strategies currently used in DC immunotherapeutic protocols that may at least partially explain limited clinical benefit of some clinical trials with such DC. We identified DC matured with interferon-γ and lipopolysaccharide as the most attractive candidate for future clinical trials in cancer immunotherapy.