Dendritic cell maturation with poly(I:C)-based versus PGE2-based cytokine combinations results in differential functional characteristics relevant to clinical application

The generation and application of antigen-specific T cell therapies for cancer and viral-associated disease

Immunotherapy with antigen-specific T cells is a promising, targeted therapeutic option for patients with cancer as well as for immunocompromised patients with virus infections. In this review, we characterize and compare current manufacturing protocols for the generation of T cells specific to viral and non-viral tumor-associated antigens. Specifically, we discuss: (1) the different methodologies to expand virus-specific T cell and non-viral tumor-associated antigen-specific T cell products, (2) an overview of the immunological principles involved when developing such manufacturing protocols, and (3) proposed standardized methodologies for the generation of polyclonal, polyfunctional antigen-specific T cells irrespective of donor source. Ex vivo expanded cells have been safely administered to treat numerous patients with virus-associated malignancies, hematologic malignancies, and solid tumors. Hence, we have performed a comprehensive review of the clinical trial results evaluating the safety, feasibility, and efficacy of these products in the clinic. In summary, this review seeks to provide new insights regarding antigen-specific T cell technology to benefit a rapidly expanding T cell therapy field.

A systematic review on poly(I:C) and poly-ICLC in glioblastoma: adjuvants coordinating the unlocking of immunotherapy

Immunotherapy is currently under intensive investigation as a potential breakthrough treatment option for glioblastoma. Given the anatomical and immunological complexities surrounding glioblastoma, lymphocytes that infiltrate the brain to develop durable immunity with memory will be key. Polyinosinic:polycytidylic acid, or poly(I:C), and its derivative poly-ICLC could serve as a priming or boosting therapy to unleash lymphocytes and other factors in the (immuno)therapeutic armory against glioblastoma. Here, we present a systematic review on the effects and efficacy of poly(I:C)/poly-ICLC for glioblastoma treatment, ranging from preclinical work on cellular and murine glioblastoma models to reported and ongoing clinical studies. MEDLINE was searched until 15 May 2021 to identify preclinical (glioblastoma cells, murine models) and clinical studies that investigated poly(I:C) or poly-ICLC in glioblastoma. A systematic review approach was conducted according to PRISMA guidelines. ClinicalTrials.gov was queried for ongoing clinical studies. Direct pro-tumorigenic effects of poly(I:C) on glioblastoma cells have not been described. On the contrary, poly(I:C) changes the immunological profile of glioblastoma cells and can also kill them directly. In murine glioblastoma models, poly(I:C) has shown therapeutic relevance as an adjuvant therapy to several treatment modalities, including vaccination and immune checkpoint blockade. Clinically, mostly as an adjuvant to dendritic cell or peptide vaccines, poly-ICLC has been demonstrated to be safe and capable of eliciting immunological activity to boost therapeutic responses. Poly-ICLC could be a valuable tool to enhance immunotherapeutic approaches for glioblastoma. We conclude by proposing several promising combination strategies that might advance glioblastoma immunotherapy and discuss key pre-clinical aspects to improve clinical translation.

Moving on From Sipuleucel-T: New Dendritic Cell Vaccine Strategies for Prostate Cancer

Tumors evade the immune system though a myriad of mechanisms. Using checkpoint inhibitors to help reprime T cells to recognize tumor has had great success in malignancies including melanoma, lung, and renal cell carcinoma. Many tumors including prostate cancer are resistant to such treatment. However, Sipuleucel-T, a dendritic cell (DC) based immunotherapy, improved overall survival (OS) in prostate cancer. Despite this initial success, further DC vaccines have failed to progress and there has been limited uptake of Sipuleucel-T in the clinic. We know in prostate cancer (PCa) that both the adaptive and the innate arms of the immune system contribute to the immunosuppressive environment. This is at least in part due to dysfunction of DC that play a crucial role in the initiation of an immune response. We also know that there is a paucity of DC in PCa, and that those there are immature, creating a tolerogenic environment. These attributes make PCa a good candidate for a DC based immunotherapy. Ultimately, the knowledge gained by much research into antigen processing and presentation needs to translate from bench to bedside. In this review we will analyze why newer vaccine strategies using monocyte derived DC (MoDC) have failed to deliver clinical benefit, particularly in PCa, and highlight the emerging antigen loading and presentation technologies such as nanoparticles, antibody-antigen conjugates and virus co-delivery systems that can be used to improve efficacy. Lastly, we will assess combination strategies that can help overcome the immunosuppressive microenvironment of PCa.

Usefulness of IL-21, IL-7, and IL-15 conditioned media for expansion of antigen-specific CD8+ T cells from healthy donor-PBMCs suitable for immunotherapy

Clonal anergy and depletion of antigen-specific CD8+ T cells are characteristics of immunosuppressed patients such as cancer and post-transplant patients. This has promoted translational research on the adoptive transfer of T cells to restore the antigen-specific cellular immunity in these patients. In the present work, we compared the capability of PBMCs and two types of mature monocyte-derived DCs (moDCs) to prime and to expand ex-vivo antigen-specific CD8+ T cells using culture conditioned media supplemented with IL-7, IL-15, and IL-21. The data obtained suggest that protocols involving moDCs are as efficient as PBMCs-based cultures in expanding antigen-specific CD8+ T cell to ELA and CMV model epitopes. These three gamma common chain cytokines promote the expansion of naïve-like and central memory CD8+ T cells in PBMCs-based cultures and the expansion of effector memory T cells when moDCs were used. Our results provide new insights into the use of media supplemented with IL-7, IL-15, and IL-21 for the in-vitro expansion of early-differentiated antigen-specific CD8+ T cells for immunotherapy purposes.

Recent Advances in Good Manufacturing Practice-Grade Generation of Dendritic Cells

Dendritic cells (DCs) are pivotal regulators of immune responses, specialized in antigen presentation and bridging the gap between the innate and adaptive immune system. Due to these key features, DCs have become a pillar of the continuously growing field of cellular therapies. Here we review recent advances in good manufacturing practice strategies and their individual specificities in relation to DC production for clinical applications. These take into account both small-scale experimental approaches as well as automated systems for patient care.

In situ Vaccination by Direct Dendritic Cell Inoculation: The Coming of Age of an Old Idea?

For more than 25 years, dendritic cell (DC) based vaccination has flashily held promises to represent a therapeutic approach for cancer treatment. While the vast majority of studies has focused on the use of antigen loaded DC, the intratumoral delivery of unloaded DC aiming at in situ vaccination has gained much less attention. Such approach grounds on the ability of inoculated DC to internalize and process antigens directly released by tumor (usually in combination with cell-death-inducing agents) to activate broad patient-specific antitumor T cell response. In this review, we highlight the recent studies in both solid and hematological tumors showing promising clinical results and discuss the main pitfalls and advantages of this approach for endogenous cancer vaccination. Lastly, we discuss how in situ vaccination by DC inoculation may fit with current immunotherapy approaches to expand and prolong patient response.

FICZ generates human tDCs that induce CD4+ CD25high Foxp3+ Treg-like cell differentiation

Dendritic cells (DCs) play a central role in the maintenance of immune homeostasis, their participation as professional antigen presenting cells is essential to the initiation of the adaptive immune response as well as to the induction of tolerance. The recently described role of the aryl hydrocarbon receptor (AhR) in the immune system, particularly in the modulation of the adaptive immune response has attracted the attention as a potential player in the induction of immune tolerance. However, the effects of AhR activation through endogenous ligands on human DCs have been poorly evaluated. In this study, we investigated the effect of FICZ, a natural AhR ligand, on monocyte-derived dendritic cells (Mo-DCs) from healthy subjects. We found that the activation of AhR through FICZ during DCs differentiation and maturation processes resulted in a decreased expression of CD83, an increased expression of the enzyme IDO and a reduced production of the pro-inflammatory cytokines IL-6 and TNF-α. More importantly, FICZ-treated DCs were able to induce the differentiation of naive T lymphocytes into CD4⁺ CD25^high Foxp3⁺ T reg-like cells. Our results show that the activation of the AhR on human DCs induces a tolerogenic phenotype with potential implications in immunotherapy.

Addition of CpG ODN and Poly (I:C) to a standard maturation cocktail generates monocyte-derived dendritic cells and induces a potent Th1 polarization with migratory capacity

Monocyte-derived dendritic cells (DCs) are used as immunoadjuvant cells in cancer vaccines and have made great progress. However, an optimal DCs subset is vital for this treatment effect, the current 'gold standard' cytokine cocktail DCs have a shortcoming in their cytokines secretion, especially IL-12p70, mainly because of the existence of PGE2. Therefore, it is necessary to find an appropriate DCs-based immunotherapeutic protocol. In this study, we compared a novel 'improved' maturation cytokine cocktail with the current 'gold standard' maturation cytokine cocktail used for generating standard DCs. The 'improved' maturation cytokine cocktail DCs showed a higher levels surface markers expression (CD80, CD83, CD86 and HLA-DR), the chemokine receptors CXCR4 and CCR7 and chemokine CCL19, CCL21 and CXCL21, whereas CCR5 expression was reduced. Most importantly, in contrast to 'gold standard' DCs, which secrete little IL-12p70 and as a result induce mainly Th2 immunity, 'improved' cytokine cocktail DCs secreted higher levels IL-12p70 and also secreted similar concentration IL-10. To removal of PGE2 from the 'improved' DCs did increase the IL-12p70 production. In conclusion, we here present the 'improved' DCs, as an optimal maturation cocktail protocol, can induce high migratory potential, generate immunostimulatory DCs, produce higher levels IL-12p70 with superior capacity to induce Th1 immunity, when compared with the 'gold standard' DCs.

Gene Expression Profiling of Human Monocyte-derived Dendritic Cells - Searching for Molecular Regulators of Tolerogenicity

The ability of dendritic cells (DCs) to initiate and modulate antigen-specific immune responses has made them attractive targets for immunotherapy. Since DC research in humans is limited by the scarcity of DC populations in the blood circulation, most of our knowledge about DC biology and function has been obtained in vitro from monocyte-derived DCs (moDCs), which can be readily generated in sufficient numbers and are able to differentiate into distinct functional subsets depending on the nature of stimulus. In particular, moDCs with tolerogenic properties (tolDCs) possess great therapeutic potential for the treatment of autoimmune diseases. Several protocols have been developed to generate tolDCs in vitro, able to reinstruct auto-reactive T cells and to promote regulatory cells. While ligands and soluble mediators, by which DCs shape immune responses, have been vastly studied, the intracellular pathways and transcriptional regulators that govern tolDC differentiation and function are poorly understood. Whole-genome microarrays and proteomics provide useful strategies to dissect the complex molecular processes that promote tolerogenicity. Only few attempts have been made to understand tolDC biology through a global view on "omics" profiles. So far, the identification of a common regulator of tolerogenicity has been hampered by the fact that each protocol, used for tolDC generation, targets distinct signaling pathways. Here, we review the progress in understanding the transcriptional regulation of moDC differentiation, with a special focus on tolDCs, and highlight candidate molecules that might be associated with DC tolerogenicity.

Poly (I: C) modulates the immunosuppressive activity of myeloid-derived suppressor cells in a murine model of breast cancer

Polyinosinic-polycytidylic acid [Poly (I: C)], a ligand for Toll-like receptor (TLR-3), is used as an adjuvant to enhance anti-tumor immunity because of its prominent effects on CD8 T cells and NK cells. Myeloid-derived suppressor cells (MDSCs) are one of the main immunosuppressive factors in cancer, and their abnormal accumulation is correlated with the clinical stage of breast cancer and is an important mechanism of tumor immune evasion. Although Poly (I: C) is thought to have direct anti-tumor activity in different cell lines, its effect on immunosuppressive MDSCs in tumor-bearing animals has not been studied. 4T1-Luc, a metastatic breast cancer mouse cell line, was injected into the left flank of female BALB/c mice. Tumor-bearing mice were treated with i.p. injection of Poly (I: C) or PBS beginning on day 7 after tumor inoculation. WBCs and MDSCs were counted using coulter counter and stained for flow cytometry, respectively. Bioluminescent imaging was used to monitor tumor burden at multiple time points during the course of tumor growth. Poly (I: C) treatment led to a decrease in MDSC frequencies in BM, blood, and tumor compared to saline-treated control mice. Poly (I: C) treatment also abrogated the immunosuppressive function of MDSCs, concomitant with an increase in local T cell response of the immune system in a murine model of breast cancer. Poly (I: C) treatment decreases MDSC frequency and immunosuppressive function in 4T1-tumor-bearing hosts and effectively augments the activity of breast cancer immunotherapy.

ELISpot and DC-ELISpot Assay to Measure Frequency of Antigen-Specific IFNγ-Secreting Cells

ELISpot is a highly sensitive method in immunology to enumerate cells producing a given cytokine. Cells are stimulated in a microtiter plate pre-coated with a specific anti-analyte antibody. In response to the stimulation, cells release cytokines that are bound to the anti-analyte antibody. After a washing step, which removes the cells from the wells, the location of the cytokine-releasing cell is visualized by an enzyme-labeled detection antibody and its corresponding chromogenic substrate. The end result is a set of colored spots, each of which represents an area where a cell secreting the cytokine had been located. Here we describe the standard ELISpot protocol and a variation denominated dendritic cell (DC)-ELISpot for the detection of IFNγ-secreting cells upon stimulation with oligopeptides and protein antigens, respectively.

Low molecular weight hyaluronan-pulsed human dendritic cells showed increased migration capacity and induced resistance to tumor chemoattraction

We have shown that ex vivo pre-conditioning of bone marrow-derived dendritic cells (DC) with low molecular weight hyaluronan (LMW HA) induces antitumor immunity against colorectal carcinoma (CRC) in mice. In the present study we investigated the effects of LMW HA priming on human-tumor-pulsed monocytes-derived dendritic cells (DC/TL) obtained from healthy donors and patients with CRC. LMW HA treatment resulted in an improved maturation state of DC/TL and an enhanced mixed leucocyte reaction activity in vivo. Importantly, pre-conditioning of DC/TL with LMW HA increased their ability to migrate and reduced their attraction to human tumor derived supernatants. These effects were associated with increased CCR7 expression levels in DC. Indeed, a significant increase in migratory response toward CCL21 was observed in LMW HA primed tumor-pulsed monocyte-derived dendritic cells (DC/TL/LMW HA) when compared to LWM HA untreated cells (DC/TL). Moreover, LMW HA priming modulated other mechanisms implicated in DC migration toward lymph nodes such as the metalloproteinase activity. Furthermore, it also resulted in a significant reduction in DC migratory capacity toward tumor supernatant and IL8 in vitro. Consistently, LMW HA dramatically enhanced in vivo DC recruitment to tumor-regional lymph nodes and reduced DC migration toward tumor tissue. This study shows that LMW HA--a poorly immunogenic molecule--represents a promising candidate to improve human DC maturation protocols in the context of DC-based vaccines development, due to its ability to enhance their immunogenic properties as well as their migratory capacity toward lymph nodes instead of tumors.

Type I interferons as regulators of human antigen presenting cell functions

Type I interferons (IFNs) are pleiotropic cytokines, initially described for their antiviral activity. These cytokines exhibit a long record of clinical use in patients with some types of cancer, viral infections and chronic inflammatory diseases. It is now well established that IFN action mostly relies on their ability to modulate host innate and adaptive immune responses. Work in recent years has begun to elucidate the mechanisms by which type I IFNs modify the immune response, and this is now recognized to be due to effects on multiple cell types, including monocytes, dendritic cells (DCs), NK cells, T and B lymphocytes. An ensemble of results from both animal models and in vitro studies emphasized the key role of type I IFNs in the development and function of DCs, suggesting the existence of a natural alliance between these cytokines and DCs in linking innate to adaptive immunity. The identification of IFN signatures in DCs and their dysregulation under pathological conditions will therefore be pivotal to decipher the complexity of this DC-IFN interaction and to better exploit the therapeutic potential of these cells.

Stimulating surface molecules, Th1-polarizing cytokines, proven trafficking--a new protocol for the generation of clinical-grade dendritic cells

BACKGROUND AIMS

Dendritic cells (DC) have been vigorously investigated as an immunological basis for therapeutic vaccination against cancer and infections, even among patients after allogeneic stem cell transplantation.

METHODS

Effective induction of cell-mediated immunity strongly depends on the ability of DC to (i) migrate to the draining lymphoid organs mediated by chemokine receptors, (ii) prime T cells through high expression of costimulatory molecules and major histocompatibility complexes and (iii) secret Th1-polarizing cytokines such as Interleukin-12 (IL-12). However, there is no protocol to generate fully matured and functional DC according to methodical requirements of current good manufacturing practice (CGMP) guidelines.

RESULTS

We established a protocol conforming to CGMP standards that permits the generation of fully matured and functional DC on the basis of cell culture in adherence bags with the use of serum-free media with a maturation cocktail, containing tumor necrosis factor-alpha/Interferon-alpha/polyinosinic:polycytidylic acid. Our DC superiorly display three critical features for an effective induction of cell-mediated immunity without evidence of exhaustion, along with its ability to prime infectious or tumor-specific T cells in a short-term cell culture.

CONCLUSIONS

Our newly developed protocol offers an attractive method to produce fully matured Th1-polarizing DC with proven migratory and stimulatory capacity for any clinical application according to CGMP standards.

Usage of standardized antigen-presenting cells improves ELISpot performance for complex protein antigens

The enzyme-linked immunospot (ELISpot) assay is a widely used method for immune monitoring in cancer immunotherapy trials. In the ELISpot assay, peripheral blood mononuclear cells (PBMC) are stimulated with specific antigens, and cytokines of interest produced by individual cells are detected. In the standard procedure, T cells rely for antigen presentation on other cells like the monocyte/macrophage population present among the PBMC. Whereas oligopeptides can be added directly to the ELISpot assay without the necessity of a pre-incubation step, protein antigens must be internalized and processed by antigen-presenting cells to accomplish efficient presentation via HLA class I or II. We have studied the impact of sources for different antigen-presenting cell (i.e. PBMC-resident monocytes and monocyte-derived dendritic cells maturated with Poly I:C and PGE-2 based cocktails) on ELISpot assay performance and defined an optimized dendritic cell-based ELISpot protocol. This protocol is suitable for monitoring immune responses directed to protein antigens with higher sensitivity than the standard procedure.

The ratio between dendritic cells and T cells determines whether prostaglandin E2 has a stimulatory or inhibitory effect

Prostaglandin E2 has been shown to enhance the maturation, migration, and antigen-presenting capacity of DCs. It is therefore included in many maturation cocktails for the generation of monocyte-derived DCs. Paradoxically, PGE2 is also an important tumor-derived immunosuppressive factor and has inhibitory effects on DC differentiation and function. To further investigate these seemingly contradictory results we studied whether the DC:T cell ratio has an impact on the outcome of the interaction between PGE2-treated DCs and T cells. Surprisingly, at high DC:T cell ratios T cell proliferation was inhibited while at low ratios PGE2-treated DCs displayed enhanced T cell-stimulatory properties. The inhibitory function of PGE2-treated DCs depended primarily on the PGE2-induced induction of indoleamine 2,3-dioxygenase competence. In summary, we show that PGE2-treated DCs can have either an immunogenic or tolerogenic function depending on the DC:T cell ratio. This finding could explain the conflicting results regarding the influence of PGE2 on DC function.

Maturation of human iDCs by IL-18 plus PGE2, but not by each stimulus alone, induced migration toward CCL21 and the secretion of IL-12 and IFN-γ

Dendritic cells (DCs) are potent antigen-presenting cells that initiate the primary immune response and whose functional properties in vivo depend on the maturation stimulus. We describe the functional properties of human monocyte-derived DCs after the maturation of immature DCs (iDCs) for 2 days with LPS (100 ng/ml), PGE2 (1 μg/ml), CD40L (1 μg/ml) or IL-18 (200 ng/ml) and with CD40L+PGE2 and IL-18+PGE2 mixtures at the same concentrations as above. Neither IL-18 nor PGE2 alone stimulated IL-12 or IFN-γ secretion. When administered simultaneously to 1×10(6)iDCs/ml, IL-18+PGE2 induced the secretion of 131.4±6.7 pg IL-12/ml and 355±87 pg IFN-γ/ml but there was no detectable IL-10 secretion. However, PGE2 alone stimulated the secretion of 208±89 pg IL-10/ml whereas IL-18 alone did not stimulate the secretion of IL-10, IL-12, TNF-α or INF-γ. When the mixture of CD40L+PGE2 was used, only migration toward CCL19 and CCL21 was induced. CD40L did not stimulate the secretion of IL-10, IL-12, TNF-α or IFN-γ and did not stimulate migration toward CCL19 or CCL21. The extent of stimulation of T cell proliferation was essentially the same for all stimuli at the concentrations given above. New properties such as IL-12 and INF-γ secretion and migration toward CCL21 emerged when a mixture of IL-18+PGE2 was employed. These data show that when the pairs of stimuli reported here were used simultaneously their effect was not additive. This system can be used to prepare mDCs with properties useful for cell therapy and also as a model to investigate the mechanisms of cytokine secretion and cell migration.

Ambivalent effects of dendritic cells displaying prostaglandin E2-induced indoleamine 2,3-dioxygenase

Prostaglandin E2 (PGE(2)), an abundantly produced lipid messenger in mammalian organisms, has been attributed to possess potent albeit ambivalent immunological functions. Recently, PGE(2) has been reported to stimulate the commonly believed immunosuppressive indoleamine 2,3-dioxygenase (IDO) pathway in human dendritic cells (DCs), but without promoting DC immunosuppressive activity. Here, we report that PGE(2) used as a DC maturation agent apparently has more diverse functions. PGE(2)-matured DCs acquired powerful IDO activity, which was sustained even after removing PGE(2). These IDO-competent DCs were able to stimulate allogeneic T-cell proliferation, but achieved inhibitory activity as their content in DC/T-cell co-cultures increased. The DC inhibitory activity was reversed upon blockade of IDO activity, confirming that the suppressive effect was in fact mediated by IDO and occurred in a dose-dependent fashion. IDO-mediated T-cell suppression was restored upon re-stimulation of T cells in the absence of IDO activity, confirming its reversibility. T cells stimulated by PGE(2)-matured IDO-competent DCs were sensitized to produce multiple cytokines, comprising Th1, Th2, and Th17 phenotypes. Collectively, these data suggest that T cells stimulated by PGE(2)-matured DCs are not terminally differentiated and their ultimate type of response may be formed by microenvironmental conditions.

Distinct modulation of chemokine expression patterns in human monocyte-derived dendritic cells by prostaglandin E(2)

Dendritic cells (DCs) are key in regulating immune responses. DCs reside in tissues facing the environment and sample their surrounding for pathogens. Upon pathogen encounter, DCs mature and migrate into secondary lymphoid organs. Distinct maturation signals dictate the ability of DCs to produce distinct patterns of chemokines that orchestrate immunity. Prostaglandin E(2) (PGE(2)) is produced during inflammation and modulates DC functions. We demonstrate that PGE(2) modulates distinct chemokine expression patterns of human monocyte-derived (Mo) DCs upon maturation with various stimuli. PGE(2) dampened early production of the inflammatory chemokines CCL2, CCL4, CCL5 and attenuated the expression of the T cell attractant CXCL10. In contrast, PGE(2) enhanced CXCL8 production early during maturation, whereas CXCL16 levels were continuously elevated, contributing to innate immune cell recruitment. Moreover, PGE(2) induces transcription of the homeostatic chemokines CCL17 and CCL22. Finally, mature MoDCs produced the homing chemokine CCL19 and its expression was down-regulated by PGE(2).

Poly(I:C)-induced tumour cell death leads to DC maturation and Th1 activation

Dendritic cells (DCs) have the ability to generate peptide epitopes for MHC class I molecules derived from apoptotic tumour cells for direct recognition by cytotoxic T cells. This function has lead to DCs being used in vaccine strategies. In this study, we investigate the effect of inducing apoptosis in tumour cell lines using IFN-γ and poly(I:C), the subsequent maturation of the endocytosing DC and its ability to direct the resulting T cell response. We show that uptake of poly(I:C)-induced apoptotic tumour cells leads to DC maturation and activation with a Th1 cell polarising capacity. In contrast, these effects are not seen by DCs loaded with γ-irradiated apoptotic tumour cells. We propose that the manner in which tumour cells are induced to die can have a profound effect on the endocytosing DC and the resulting T cell response.

Low molecular weight hyaluronan preconditioning of tumor-pulsed dendritic cells increases their migratory ability and induces immunity against murine colorectal carcinoma

We have recently shown that systemic administration of low molecular weight hyaluronan (LMW HA) significantly reduces colorectal carcinoma (CRC) growth in vivo. The elicited response is partially mediated by activated dendritic cells (DC). To potentiate the ability of DC loaded with whole tumor lysate (DC/TL) to induce immunity against CRC in mice, we aimed to study the effects of preconditioning DC with LMW HA for therapeutic vaccination. LMW HA improved maturation of ex vivo generated DC, increased IL-12, decreased IL-10 production, and enhanced a MLR activity in vitro. Although TNF-α showed a similar capacity to mature DC, preconditioning of DC/TL with LMW HA increased their ability to migrate in vitro toward CCL19 and CCL-21 in a CD44- and a TLR4-independent manner; this effect was superior to Poly(I:C), LPS, or TNF-α and partially associated with an increase in the expression of CCR7. Importantly, LMW HA dramatically enhanced the in vivo DC recruitment to tumor-regional lymph nodes. When these LMW HA-treated CRC tumor lysate-pulsed DC (DC/TL/LMW HA) were administered to tumor-bearing mice, a potent antitumor response was observed when compared to DC pulsed with tumor lysate alone and matured with TNF-α. Then, we showed that splenocytes isolated from animals treated with DC/TL/LMW HA presented a higher proliferative capacity, increased IFN-γ production, and secreted lower levels of the immunosuppressive IL-10. Besides, increased specific CTL response was observed in DC/TL/LMW HA-treated animals and induced long-term protection against tumor recurrence. Our data show that LMW HA is superior to other agents at inducing DC migration; therefore, LMW HA could be considered a new adjuvant candidate in the preparation of DC-based anticancer vaccines with potent immunostimulatory properties.

Bromelain treatment leads to maturation of monocyte-derived dendritic cells but cannot replace PGE2 in a cocktail of IL-1β, IL-6, TNF-α and PGE2

Immunotherapy using dendritic cells (DC) has shown promising results. However, the use of an appropriate DC population is critical for the outcome of this treatment, and the search for an optimal DC subset is still ongoing. The DC used in immunotherapy today are usually matured with a cytokine cocktail consisting of TNF-α, IL-1β, IL-6 and PGE(2). These cells have deficits in their cytokine production, particularly IL-12p70, mainly because of the presence of PGE(2). Bromelain is a pineapple stem extract containing a mixture of proteases that has been used clinically in adjuvant cancer treatment. In this study, we analysed the effect of bromelain on human monocyte-derived DC. We added bromelain to the cytokine cocktail and modified cytokine cocktails with either no PGE(2) or reduced amounts of PGE(2), respectively. Combining bromelain with the cytokine cocktails containing PGE(2) resulted in an increased surface expression of CD83, CD80 and CD86. The chemokine receptor CCR7 was also considerably upregulated in these DC populations compared with DC treated with the cytokine cocktail alone. Removal or reduction of PGE(2) from the cytokine cocktail did not increase the IL-12p70 secretion from stimulated DC, and addition of bromelain to the different cytokine cocktails resulted in only a minor increase in IL-12p70 production. Moreover, combining bromelain with the cytokine cocktails did not improve the T cell stimulatory capacity of the generated DC populations. In conclusion, bromelain treatment of monocyte-derived DC does not improve the functional quality compared with the standard cytokine cocktail.

Contact sensitizers modulate the arachidonic acid metabolism of PMA-differentiated U-937 monocytic cells activated by LPS

For the effective induction of a hapten-specific T cell immune response toward contact sensitizers, in addition to covalent-modification of skin proteins, the redox and inflammatory statuses of activated dendritic cells are crucial. The aim of this study was to better understand how sensitizers modulate an inflammatory response through cytokines production and COX metabolism cascade. To address this purpose, we used the human monocytic-like U-937 cell line differentiated by phorbol myristate acetate (PMA) and investigated the effect of 6 contact sensitizers (DNCB, PPD, hydroquinone, propyl gallate, cinnamaldehyde and eugenol) and 3 non sensitizers (lactic acid, glycerol and tween 20) on the production of pro-inflammatory cytokines (IL-1β and TNF-α) and on the arachidonic acid metabolic profile after bacterial lipopolysaccharide (LPS) stimulation. Our results showed that among the tested molecules, all sensitizers specifically prevent the production of PMA/LPS-induced COX-2 metabolites (PGE(2,) TxB(2) and PGD(2)), eugenol and cinnamaldehyde inhibiting also the production of IL-1β and TNF-α. We further demonstrated that there is no unique PGE(2) inhibition mechanism: while the release of arachidonic acid (AA) from membrane phospholipids does not appear do be a target of modulation, COX-2 expression and/or COX-2 enzymatic activity are the major steps of prostaglandin synthesis that are inhibited by sensitizers. Altogether these results add a new insight into the multiple biochemical effects described for sensitizers.

Monocyte-derived DC maturation strategies and related pathways: a transcriptional view

Ex vivo production of highly stimulator mature dendritic cells (DCs) for cellular therapy has been used to treat different pathological conditions with the aim of inducing a specific immune response. In the last decade, several protocols have been developed to mature monocyte-derived DCs: each one has led to the generation of DCs showing different phenotypes and stimulatory abilities, but it is not yet known which one is the best for inducing effective immune responses. We grouped several different maturation protocols according to the downstream pathways they activated and reviewed the shared features at a transcriptomic level to reveal the potential of DCs matured by each protocol to develop Th-polarized immune responses.

Two-step maturation of immature DCs with proinflammatory cytokine cocktail and poly(I:C) enhances migratory and T cell stimulatory capacity

Effective induction of cell-mediated immune responses strongly depends on the ability of dendritic cells (DCs) to produce Th1-polarizing cytokines, migrate to lymph nodes and stimulate T cells through antigen-presenting complex and costimulatory molecules. While various protocols for optimizing DC maturation with single or multiple stimuli mimicking infections or inflammatory milieu have been proposed for the generation of DCs with features desired for clinical application, stepwise maturation of DCs by these multiple stimuli has not been systemically assessed. Among the combinations of several immune-modulating factors with known effects on DC maturation, we found that stepwise DC maturation with cytokine cocktail (TNF-alpha+IL-6+IL-1 beta+PGE(2)) followed by poly(I:C) stimulation enhanced the production of IL-12 with strong allostimulatory capacity. While there were no significant differences between DC matured by simultaneous or sequential activation by cytokine cocktail and poly(I:C) in expression of markers and costimulatory molecules of mature DCs, the delivery of inflammatory signal prior to poly(I:C) results in sustained interleukin-12 expression with reduced IL-10 than DC matured by simultaneous stimulation. This sequential stimulation significantly increased migratory capacity in response to CCL21 and CXCL12 compared to DC matured with cytokine cocktail. Furthermore, these DCs retained their responsiveness to CD40L stimulation in secondary IL-12 production and efficiently generated autologous antigen-specific effector T cells as evidenced by ELISPOT assay. Thus, we propose a novel DC maturation protocol in which stimulation of DCs with cytokine cocktail and subsequently with poly(I:C) generates DCs with a high migratory capacity with a preferential Th1 inducing capacity.

Intracellular delivery of major histocompatibility complex class I-binding epitopes: dendritic cells loaded and matured with cationic peptide/poly(I:C) complexes efficiently activate T cells

Based on their role for the induction of T-cell responses, dendritic cells (DCs) are popular candidates in cancer vaccine development. We established a novel single-step intracellular delivery of peptide/poly(I:C) complexes for antigen loading and Toll-like receptor-3 (TLR3)-mediated maturation of human DCs using a cell-penetrating peptide (tat(49-57): RKKRRQRRR) as delivery vector. Towards this end, a cationic tat-sequence was fused with an antigenic, major histocompatibility complex (MHC) class I-binding melanoma epitope (Melan-A/Mart-1 sequence: ELAGIGILTV) and then mixed with negatively charged poly(I:C) dsRNA to form peptide/nucleic acid complexes. Flow cytometry and confocal laser scanning microscopy confirmed intracellular localization of TLR3 in monocyte-derived immature DCs (iDCs). Peptide/poly(I:C) complexes were readily internalized by iDCs without negatively affecting cell viability. They induced DC maturation and secretion of bioactive interleukin (IL)-12p70. When peptide/poly(I:C) complex-loaded DCs were used for autologous T cell stimulation, epitope-specific interferon-gamma secretion was quantitatively superior in comparison to peptide-loaded DCs matured by a cytokine cocktail, as detected by enzyme-linked immunospot assays. Thus, complexes of cationic antigenic peptides and poly(I:C) might be of great utility for a TLR3-mediated DC maturation and intracellular peptide targeting in a single step. Resulting DCs induce a strong expansion/activation of antigen-specific T cells in the context of an IL-12p70 secretion.

Dendritic-cell vaccination for prostate cancer

Vaccination with tumor antigen-loaded dendritic cells has been one of the most frequently applied immunotherapeutic strategies in prostate cancer. Immunological effects have been observed in a majority of patients, while clinical effects have been modest and transient. Advances in the understanding of the interplay between cancer and the immune system have generated new concepts in tumor immunology and immunotherapy that might aid in the improvement of vaccine effectiveness. The combination of immunotherapy with conventional treatment modalities and targeting of immunosuppressive mechanisms has demonstrated improved immunological and clinical results that warrant further investigation.