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

Combined Osteopontin Blockade and Type 2 Classical Dendritic Cell Vaccination as Effective Synergetic Therapy for Conjunctival Melanoma

Angiogenesis and immune protection are essential at the onset of tumorigenesis. Angiogenesis serves to nourish the tumor, and prevention of immune defenses, for example, by dendritic cells (DCs), allows tumor growth. In this study, we investigated whether there are factors with dual functions that are both angiogenic and immunomodulatory and represent a therapeutic target. We analyzed 1) innate immune responses intratumorally and in draining lymph nodes and 2) angiogenic factors in conjunctival melanoma (CM), a potentially lethal malignant tumor at the ocular surface whose immune and vascular responses are largely unknown. For this purpose, an HGF-Cdk4R24C model in immunocompetent C57BL/6 mice was used and revealed that CD103- type 2 classical DC (cDC2s) were the most abundant DC subtype in healthy conjunctiva, whereas in CM, CD103- cDC2s, CD103+ type 1 cDCs, monocyte-derived DCs, and plasmacytoid DCs were significantly increased. In our analysis of angiogenic factors in CM, the examination of 53 angiogenesis-related factors that might interact with DCs identified osteopontin (OPN) as a major tumor-derived protein that interacts with DCs. Consistent with these findings, 3) a dual therapeutic strategy that inhibited tumor cell function by an OPN blocking Ab while enhancing the immune response by cDC2 vaccination resulted in 35% failure of tumor development. Moreover, tumor progression, monocyte-derived DC infiltration, and intratumoral angiogenesis were significantly reduced, whereas survival and CD8+ T cell infiltration were increased in treated mice compared with the control group. Therefore, we identified OPN blockade in combination with cDC2 vaccination as a potential future therapeutic intervention for early stages of CM by combining antiangiogenic and host immune stimulating effects.

Lactobacilli Probiotics Modulate Antibacterial Response Gene Transcription of Dendritic Cells Challenged with LPS

Probiotics are beneficial bacteria that may modulate the immune response by altering the maturation and function of antigen-presenting cells, such as dendritic cells. This study aimed to evaluate the antibacterial gene expression of dendritic cells challenged with LPS and probiotics. Immature dendritic cells were obtained from human CD14+ monocytes and challenged with E. coli LPS and probiotics Lacticaseibacillus rhamnosus (LR-32) and Lactobacillus acidophilus (LA-5) at a ratio DC:bacteria of 1:10. The analysis of gene expression was performed by RT-qPCR using the Kit RT2 human antibacterial response. In the supernatant, the cytokines secretion was determined by ELISA. Tukey post-ANOVA with p at 5% was used for statistical analysis. LPS showed the higher upregulation of 29 genes compared with the groups where probiotics were added to LPS, including genes related to an inflammatory response like BIRC3, CASP1, CCL5, CXCL1, IL12B, IL18, MYD88, NLRP3, RIPK1, and TIRAP. Similarly, LPS increased the transcription of genes enrolled with apoptosis such as CARD6, CASP1, IRF5, MAP2K1, MAP2K4, MAPK1, MYD88, NLRP3, RIPK2, TNF, TNFRSF1A, and XIAP when compared to probiotics groups (p < 0.05). Although probiotics decrease several genes upregulated by LPS, the transcription of encoded cytokines IL12A, IL12B, IL1B, IL6, CXCL8, and TNF genes was maintained upregulated by probiotics, except for IL18, which was downregulated by LA-5. LA-5 led to a higher transcription of IL1B, IL6, and CXCL-8 which was followed by the secretion of these proteins by ELISA. The results suggest that probiotics attenuate the transcription of inflammatory and immune response genes caused by LPS.

Modeling human immune responses to vaccination in vitro

The human immune system is a complex network of coordinated components that are crucial for health and disease. Animal models, commonly used to study immunomodulatory agents, are limited by species-specific differences, low throughput, and ethical concerns. In contrast, in vitro modeling of human immune responses can enable species- and population-specific mechanistic studies and translational development within the same study participant. Translational accuracy of in vitro models is enhanced by accounting for genetic, epigenetic, and demographic features such as age, sex, and comorbidity. This review explores various human in vitro immune models, considers evidence that they may resemble human in vivo responses, and assesses their potential to accelerate and de-risk vaccine discovery and development.

Immuno-metabolic dendritic cell vaccine signatures associate with overall survival in vaccinated melanoma patients

Efficacy of cancer vaccines remains low and mechanistic understanding of antigen presenting cell function in cancer may improve vaccine design and outcomes. Here, we analyze the transcriptomic and immune-metabolic profiles of Dendritic Cells (DCs) from 35 subjects enrolled in a trial of DC vaccines in late-stage melanoma (NCT01622933). Multiple platforms identify metabolism as an important biomarker of DC function and patient overall survival (OS). We demonstrate multiple immune and metabolic gene expression pathway alterations, a functional decrease in OCR/OXPHOS and increase in ECAR/glycolysis in patient vaccines. To dissect molecular mechanisms, we utilize single cell SCENITH functional profiling and show patient clinical outcomes (OS) correlate with DC metabolic profile, and that metabolism is linked to immune phenotype. With single cell metabolic regulome profiling, we show that MCT1 (monocarboxylate transporter-1), a lactate transporter, is increased in patient DCs, as is glucose uptake and lactate secretion. Importantly, pre-vaccination circulating myeloid cells in patients used as precursors for DC vaccine generation are significantly skewed metabolically as are several DC subsets. Together, we demonstrate that the metabolic profile of DC is tightly associated with the immunostimulatory potential of DC vaccines from cancer patients. We link phenotypic and functional metabolic changes to immune signatures that correspond to suppressed DC differentiation.

Human dendritic cell subsets in the glioblastoma-associated microenvironment

Glioblastoma (GBM) is the most aggressive type of glioma (Grade IV). The presence of cytotoxic T lymphocyte (CTLs) has been associated with improved outcomes in patients with GBM, and it is believed that the activation of CTLs by dendritic cells may play a critical role in controlling the growth of GBM. DCs are professional antigen-presenting cells (APC) that orchestrate innate and adaptive anti-GBM immunity. DCs can subsequently differentiate into plasmacytoid DCs (pDC), conventional DC1 (cDC1), conventional (cDC2), and monocyte-derived DCs (moDC) depending on environmental exposure. The different subsets of DCs exhibit varying functional capabilities in antigen presentation and T cell activation in producing an antitumor response. In this review, we focus on recent studies describing the phenotypic and functional characteristics of DC subsets in humans and their respective antitumor immunity and immunotolerance roles in the GBM-associated microenvironment. The critical components of crosstalk between DC subsets that contribute significantly to GBM-specific immune responses are also highlighted in this review with reference to the latest literature. Since DCs could be prime targets for therapeutic intervention, it is worth summarizing the relevance of DC subsets with respect to GBM-associated immunologic tolerance and their therapeutic potential.

Tumor vaccine based on extracellular vesicles derived from γδ-T cells exerts dual antitumor activities

γδ-T cells are innate-like T cells with dual antitumor activities. They can directly eradicate tumor cells and function as immunostimulatory cells to promote antitumor immunity. Previous studies have demonstrated that small extracellular vesicles (EVs) derived from γδ-T cells (γδ-T-EVs) inherited the dual antitumor activities from their parental cells. However, it remains unknown whether γδ-T-EVs can be designed as tumors vaccine to improve therapeutic efficacy. Here, we found that γδ-T-EVs had immune adjuvant effects on antigen-presenting cells, as revealed by enhanced expression of antigen-presenting and co-stimulatory molecules, secretion of pro-inflammatory cytokines and antigen-presenting ability of DCs after γδ-T-EVs treatment. The γδ-T-EVs-based vaccine was designed by loading tumor-associated antigens (TAAs) into γδ-T-EVs. Compared with γδ-T-EVs, the γδ-T-EVs-based vaccine effectively promoted more tumor-specific T-cell responses. In addition, the vaccine regimen preserved direct antitumor effects and induced tumor cell apoptosis. Interestingly, the allogeneic γδ-T-EVs-based vaccine showed comparable preventive and therapeutic antitumor effects to their autologous counterparts, indicating a better way of centralization and standardization in clinical practice. Furthermore, the allogeneic γδ-T-EVs-based vaccine displayed advantages over the DC-EVs-based vaccine through their dual antitumor activities. This study provides a proof-of-concept for using the allogeneic γδ-T-EVs-based vaccine in cancer control.

CaCO3 powder-mediated biomineralization of antigen nanosponges synergize with PD-1 blockade to potentiate anti-tumor immunity

Antigen self-assembly nanovaccines advance the minimalist design of therapeutic cancer vaccines, but the issue of inefficient cross-presentation has not yet been fully addressed. Herein, we report a unique approach by combining the concepts of "antigen multi-copy display" and "calcium carbonate (CaCO₃) biomineralization" to increase cross-presentation. Based on this strategy, we successfully construct sub-100 nm biomineralized antigen nanosponges (BANSs) with high CaCO₃ loading (38.13 wt%) and antigen density (61.87%). BANSs can be effectively uptaken by immature antigen-presenting cells (APCs) in the lymph node upon subcutaneous injection. Achieving efficient spatiotemporal coordination of antigen cross-presentation and immune effects, BANSs induce the production of CD4⁺ T helper cells and cytotoxic T lymphocytes, resulting in effective tumor growth inhibition. BANSs combined with anti-PD-1 antibodies synergistically enhance anti-tumor immunity and reverse the tumor immunosuppressive microenvironment. Overall, this CaCO₃ powder-mediated biomineralization of antigen nanosponges offer a robust and safe strategy for cancer immunotherapy.

The synergistic and enhancive effects of IL-6 and M-CSF to expand and differentiate functional dendritic cells from human monocytes under serum-free condition

BACKGROUND

Dendritic cells (DCs) are differentiated from monocytes, and have a strong ability to perform phagocytosis, present antigens and activate T cell immune response. Therefore, DCs are one of the key factors in fighting cancer in immunotherapy, and it is an important issue to develop a serum-free system for DC differentiation and expansion in vitro for clinical application.

RESULTS

In this study, IL-6 and M-CSF were determined and a concentration combination of cytokines was optimized to develop an optimal DC serum-free differentiation medium (SF-DC Optimal) that can effectively differentiate CD14⁺ monocytes into CD40⁺CD209⁺ DCs. After differentiation, the morphology, growth kinetics, surface antigen expression, phagocytosis ability, cytokine secretion, mixed lymphocyte reaction and stimulation for maturation of the differentiated DCs were checked and confirmed. Importantly, this research is the first report finding that the addition an extra low concentration of IL-6 and M-CSF exhibited a synergistic effect with GM-CSF and IL-4 to generate higher numbers and more fully functional DCs than the addition of GM-CSF and IL-4 only under serum-free condition.

CONCLUSION

A large number of functional DCs can be generated by using SF-DC Optimal medium and provide an alternative source of DCs for related basic research and clinical applications.

The role of interferons in ovarian cancer progression: Hinderer or promoter?

Ovarian cancer (OC) is a common gynecologic malignancy with poor prognosis and high mortality. Changes in the OC microenvironment are closely related to the genesis, invasion, metastasis, recurrence, and drug-resistance. The OC microenvironment is regulated by Interferons (IFNs) known as a type of important cytokines. IFNs have a bidirectional regulation for OC cells growth and survival. Meanwhile, IFNs positively regulate the recruitment, differentiation and activation of immune cells. This review summarizes the secretion and the role of IFNs. In particular, we mainly elucidate the actions played by IFNs in various types of therapy. IFNs assist radiotherapy, targeted therapy, immunotherapy and biotherapy for OC, except for some IFN pathways that may cause chemo-resistance. In addition, we present some advances in OC treatment with the help of IFN pathways. IFNs have the ability to powerfully modulate the tumor microenvironment and can potentially provide new combination strategies for OC treatment.

LL-37 as a Powerful Molecular Tool for Boosting the Performance of Ex Vivo-Produced Human Dendritic Cells for Cancer Immunotherapy

Ex vivo-produced dendritic cells (DCs) constitute the core of active cellular immunotherapy (ACI) for cancer treatment. After many disappointments in clinical trials, the current protocols for their preparation are attempting to boost their therapeutic efficacy by enhancing their functionality towards Th1 response and capability to induce the expansion of cytotoxic tumor-specific CD8⁺ T cells. LL-37 is an antimicrobial peptide with strong immunomodulatory potential. This potential was previously found to either enhance or suppress the desired anti-tumor DC functionality when used at different phases of their ex vivo production. In this work, we show that LL-37 can be implemented during the whole process of DC production in a way that allows LL-37 to enhance the anti-tumor functionality of produced DCs. We found that the supplementation of LL-37 during the differentiation of monocyte-derived DCs showed only a tendency to enhance their in vitro-induced lymphocyte enrichment with CD8⁺ T cells. The supplementation of LL-37 also during the process of DC antigen loading (pulsation) and maturation significantly enhanced the cell culture enrichment with CD8⁺ T cells. Moreover, this enrichment was also associated with the downregulated expression of PD-1 in CD8⁺ T cells, significantly higher frequency of tumor cell-reactive CD8⁺ T cells, and superior in vitro cytotoxicity against tumor cells. These data showed that LL-37 implementation into the whole process of the ex vivo production of DCs could significantly boost their anti-tumor performance in ACI.

Positively charged nanocomplex modulates dendritic cell differentiation to enhance Th1 immune response

Most existing vaccines use activators that polarize the immune response to T-helper (Th) 2 response for antibody production. Our positively charged chitosan (Cs)-based nanocomplex (CNC) drives the Th1 response through unknown mechanisms. As receptors for the positively charged CNC are not determined, the physico-chemical properties are hypothesized to correlate with its immunomodulatory effects. To clarify the effects of surface charge and size on the immune response, smaller CNC and negatively charged CNC encapsulating ovalbumin are tested on dendritic cell (DC) 2.4 ​cells. The negatively charged CNC loses activity, but the smaller CNC does not. To further evaluate the material effects, we replace Cs by poly-amino acids. Compared with the negatively charged nanocomplex, the positively charged one preserves its activity. Using immature bone marrow-derived DCs (BMDC) enriched from BALB/c mice as a model to analyze DC differentiation, treatments with positively charged nanocomplexes evidently increase the proportions of Langerin⁺ dermal DC, CD11b^lo interstitial DC, and CD8a⁺ conventional DC. Additionally, vaccination with two doses containing positively charged nanocomplexes are safe and increase ovalbumin-specific IgG and recall T-cell responses in mice. Overall, a positive charge seems to contribute to the immunological effect of nanocomplexes on elevating the Th1 response by modulating DC differentiation.

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.

Small Extracellular Vesicles Loaded with Immunosuppressive miRNAs Leads to an Inhibition of Dendritic Cell Maturation

In particular conditions, inhibition of an immune response is required to prevent tissue damage. Among these conditions are diseases caused by an over-reactive immune response, such as autoimmune or allergic disorders, or imminent organ rejection after transplantation. To avoid tissue damage, drug-mediated systemic immune suppression is an option, but it comes with high costs in the form of susceptibility to viral and bacterial infections. Thus, the induction of antigen-specific tolerance is preferable. Extracellular vesicles (EVs) are capable of delivering antigen together with immunosuppressive signals and may be used to specifically induce antigen-specific tolerance. However, naturally occurring EVs are heterogeneous and not all of them show immunosuppressive character. In our trials to engineer cell culture derived EVs to increase their tolerogenic potential, we equipped them with immunosuppressive miRNA mimics. Small EVs (sEVs) were isolated and purified from the human monocytic THP-1 cell line or from healthy donor peripheral blood mononuclear cells, and electroporated with miR-494 and miR-146a mimics. The acquired immunosuppressive potential of the modified sEVs was demonstrated by their ability to alter the major histocompatibility complex molecules and co-stimulatory receptors present on dendritic cells (DCs). To avoid allogeneic responses, the same cells that produced the sEVs served also as recipient cells. In contrast to the treatment with unmodified sEVs, the tolerogenic sEVs impeded lipopolysaccharide-induced maturation and kept DCs in a more immature developmental stage. Our experiments show that simple manipulations of sEVs using immunosuppressive cargo can lead to the inhibition of DC maturation.

Engineered Cell Membrane-Derived Nanoparticles in Immune Modulation

Immune modulation is one of the most effective approaches in the therapy of complex diseases, including public health emergency. However, most immune therapeutics such as drugs, vaccines, and cellular therapy suffer from the limitations of poor efficacy and adverse side effects. Fortunately, cell membrane-derived nanoparticles (CMDNs) have superior compatibility with other therapeutics and offer new opportunities to push the limits of current treatments in immune modulation. As the interface between cells and outer surroundings, cell membrane contains components which instruct intercellular communication and the plasticity of cytomembrane has significantly potentiated CMDNs to leverage our immune system. Therefore, cell membranes employed in immunomodulatory CMDNs have gradually shifted from natural to engineered. In this review, unique properties of immunomodulatory CMDNs and engineering strategies of emerging CMDNs for immune modulation, with an emphasis on the design logic are summarized. Further, this review points out some pressing problems to be solved during clinical translation and put forward some suggestions on the prospect of immunoregulatory CMDNs. It is anticipated that this review can provide new insights on the design of immunoregulatory CMDNs and expand their potentiation in the precise control of the dysregulated immune system.

Nanovaccine biomineralization for cancer immunotherapy: a NADPH oxidase-inspired strategy for improving antigen cross-presentation via lipid peroxidation

Current efforts to develop novel vaccine nanotechnologies to increase cytotoxic T lymphocytes have met the challenges of the limited efficacy of antigen cross-presentation. Recent studies have uncovered a unique biological mechanism by which activation of the NADPH oxidase 2 (NOX2) complex, a major source of reactive oxygen species (ROS), enhances the cross-presentation by antigen-presenting cells (APCs). Inspired by the NOX2 mechanism, we devise biomineralized nanovaccines named NVs^cp, which are developed by in situ growth of calcium peroxide on nanovaccines self-assembled with the model antigen ovalbumin. The ~80 nm NVs^cp efficiently flow to the draining lymph nodes, where they accumulate within APC endo-/lysosomes, and generate a rapid burst of ROS in response to the acidic endo-/lysosomal environment with the subsequent endo-/lysosomal lipid peroxidation. Accompanied by the process, NVs^cp stimulate distinct APCs maturation and antigen presentation to T lymphocytes. Notably, high levels of antigen-specific CD8⁺ T cell responses, accompanied by the induction of CD4⁺ T helper cells, are achieved. More importantly, NVs^cp significantly increase the ratios of intratumoral CD8⁺ T/regulatory T cells and achieve prominent tumor therapy effects. The NOX2-inspired biomineralized NVs^cp represent an effective and easily applicable strategy that enables the strong cross-presentation of exogenous vaccine antigens.

Immunogenic tumor cell death promotes dendritic cell migration and inhibits tumor growth via enhanced T cell immunity

Immunogenic tumor cell death enhances anti-tumor immunity. However, the mechanisms underlying this effect are incompletely understood. We established a system to induce tumor cell death in situ and investigated its effect on dendritic cell (DC) migration and T cell responses using intravital photolabeling in mice expressing KikGR photoconvertible protein. We demonstrate that tumor cell death induces phagocytosis of tumor cells by tumor-infiltrating (Ti)-DCs, and HMGB1-TLR4 and ATP-P2X7 receptor signaling-dependent Ti-DC emigration to draining lymph nodes (dLNs). This led to an increase in anti-tumor CD8⁺ T cells of memory precursor effector phenotype and secondary tumor growth inhibition in a CD103⁺ DC-dependent manner. However, combining tumor cell death induction with lipopolysaccharide treatment stimulated Ti-DC maturation and emigration to dLNs but did not improve tumor immunity. Thus, immunogenic tumor cell death enhances tumor immunity by increasing Ti-DC migration to dLNs where they promote anti-tumor T cell responses and tumor growth inhibition.

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Immunogenic cell death (ICD) promotes egress of tumor-infiltrating (Ti)-DCs to dLNs

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ICD induced Ti-DC migration to dLNs utilizes P2X7R and HMGB1 signaling pathways

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LPS treatment attenuates the anti-tumor effects of ICD

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CD103⁺ DCs are required at the time of ICD for suppression of secondary tumor growth

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.

Interleukin-1 as Innate Mediator of T Cell Immunity

The three-signal paradigm tries to capture how the innate immune system instructs adaptive immune responses in three well-defined actions: (1) presentation of antigenic peptides in the context of MHC molecules, which allows for a specific T cell response; (2) T cell co-stimulation, which breaks T cell tolerance; and (3) secretion of polarizing cytokines in the priming environment, thereby specializing T cell immunity. The three-signal model provides an empirical framework for innate instruction of adaptive immunity, but mainly discusses STAT-dependent cytokines in T cell activation and differentiation, while the multi-faceted roles of type I IFNs and IL-1 cytokine superfamily members are often neglected. IL-1α and IL-1β are pro-inflammatory cytokines, produced following damage to the host (release of DAMPs) or upon innate recognition of PAMPs. IL-1 activity on both DCs and T cells can further shape the adaptive immune response with variable outcomes. IL-1 signaling in DCs promotes their ability to induce T cell activation, but also direct action of IL-1 on both CD4⁺ and CD8⁺ T cells, either alone or in synergy with prototypical polarizing cytokines, influences T cell differentiation under different conditions. The activities of IL-1 form a direct bridge between innate and adaptive immunity and could therefore be clinically translatable in the context of prophylactic and therapeutic strategies to empower the formation of T cell immunity. Understanding the modalities of IL-1 activity during T cell activation thus could hold major implications for rational development of the next generation of vaccine adjuvants.

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.

Physical transfection technologies for macrophages and dendritic cells in immunotherapy

INTRODUCTION

Dendritic cells (DCs) and macrophages, two important antigen presenting cells (APCs) of the innate immune system, are being explored for the use in cell-based cancer immunotherapy. For this application, the therapeutic potential of patient-derived APCs is increased by delivering different types of functional macromolecules, such as mRNA and pDNA, into their cytosol. Compared to the use of viral and non-viral delivery vectors, physical intracellular delivery techniques are known to be more straightforward, more controllable, faster and generate high delivery efficiencies.

AREAS COVERED

This review starts with electroporation as the most traditional physical transfection method, before continuing with the more recent technologies such as sonoporation, nanowires and microfluidic cell squeezing. A description is provided of each of those intracellular delivery technologies with their strengths and weaknesses, especially paying attention to delivery efficiency and safety profile.

EXPERT OPINION

Given the common use of electroporation for the production of therapeutic APCs, it is recommended that more detailed studies are performed on the effect of electroporation on APC fitness, even down to the genetic level. Newer intracellular delivery technologies seem to have less impact on APC functionality but further work is needed to fully uncover their suitability to transfect APCs with different types of macromolecules.

Alarmin-painted exosomes elicit persistent antitumor immunity in large established tumors in mice

Treating large established tumors is challenging for dendritic cell (DC)-based immunotherapy. DC activation with tumor cell-derived exosomes (TEXs) carrying multiple tumor-associated antigen can enhance tumor recognition. Adding a potent adjuvant, high mobility group nucleosome-binding protein 1 (HMGN1), boosts DCs’ ability to activate T cells and improves vaccine efficiency. Here, we demonstrate that TEXs painted with the functional domain of HMGN1 (TEX-N1ND) via an exosomal anchor peptide potentiates DC immunogenicity. TEX-N1ND pulsed DCs (DC_TEX-N1ND) elicit long-lasting antitumor immunity and tumor suppression in different syngeneic mouse models with large tumor burdens, most notably large, poorly immunogenic orthotopic hepatocellular carcinoma (HCC). DC_TEX-N1ND show increased homing to lymphoid tissues and contribute to augmented memory T cells. Importantly, N1ND-painted serum exosomes from cancer patients also promote DC activation. Our study demonstrates the potency of TEX-N1ND to strengthen DC immunogenicity and to suppress large established tumors, and thus provides an avenue to improve DC-based immunotherapy.

The use of tumour exosome-activated dendritic cell (DC) immunotherapy shows promise for the treatment of large established tumours. Here, the authors generate alarmin HMGN1-attached tumour exosomes which significantly improve therapy efficacy by boosting DC activation in several preclinical mouse models.

Human Innate Immune Cells Respond Differentially to Poly-γ-Glutamic Acid Polymers from Bacillus anthracis and Nonpathogenic Bacillus Species

The poly-γ-glutamic acid (PGA) capsule produced by Bacillus anthracis is composed entirely of d-isomer glutamic acid, whereas nonpathogenic Bacillus species produce mixed d-, l-isomer PGAs. To determine if B. anthracis PGA confers a pathogenic advantage over other PGAs, we compared the responses of human innate immune cells to B. anthracis PGA and PGAs from nonpathogenic B. subtilis subsp. chungkookjang and B. licheniformis Monocytes and immature dendritic cells (iDCs) responded differentially to the PGAs, with B. anthracis PGA being least stimulatory and B. licheniformis PGA most stimulatory. All three elicited IL-8 and IL-6 from monocytes, but B. subtilis PGA also elicited IL-10 and TNF-α, whereas B. licheniformis PGA elicited all those plus IL-1β. Similarly, all three PGAs elicited IL-8 from iDCs, but B. subtilis PGA also elicited IL-6, and B. licheniformis PGA elicited those plus IL-12p70, IL-10, IL-1β, and TNF-α. Only B. licheniformis PGA induced dendritic cell maturation. TLR assays also yielded differential results. B. subtilis PGA and B. licheniformis PGA both elicited more TLR2 signal than B. anthracis PGA, but only responses to B. subtilis PGA were affected by a TLR6 neutralizing Ab. B. licheniformis PGA elicited more TLR4 signal than B. anthracis PGA, whereas B. subtilis PGA elicited none. B. anthracis PGA persisted longer in high m.w. form in monocyte and iDC cultures than the other PGAs. Reducing the m.w. of B. anthracis PGA reduced monocytes' cytokine responses. We conclude that B. anthracis PGA is recognized less effectively by innate immune cells than PGAs from nonpathogenic Bacillus species, resulting in failure to induce a robust host response, which may contribute to anthrax pathogenesis.

Cannabinoid Receptor 2 Modulates Maturation of Dendritic Cells and Their Capacity to Induce Hapten-Induced Contact Hypersensitivity

Contact hypersensitivity (CHS) is an established animal model for allergic contact dermatitis. Dendritic cells (DCs) play an important role in the sensitization phase of CHS by initiating T cell responses to topically applied haptens. The cannabinoid receptors 1 (CB1) and 2 (CB2) modulate DC functions and inflammatory skin responses, but their influence on the capacity of haptenized DCs to induce CHS is still unknown. We found lower CHS responses to 2,4-dinitro-1-fluorobenzene (DNFB) in wild type (WT) mice after adoptive transfer of haptenized Cnr2^-/- and Cnr1^-/-/Cnr2^-/- bone marrow (BM) DCs as compared to transfer of WT DCs. In contrast, induction of CHS was not affected in WT recipients after transfer of Cnr1^-/- DCs. In vitro stimulated Cnr2^-/- DCs showed lower CCR7 and CXCR4 expression when compared to WT cells, while in vitro migration towards the chemokine ligands was not affected by CB2. Upregulation of MHC class II and co-stimulatory molecules was also reduced in Cnr2^-/- DCs. This study demonstrates that CB2 modulates the maturation phenotype of DCs but not their chemotactic capacities in vitro. These findings and the fact that CHS responses mediated by Cnr2^-/- DCs are reduced suggest that CB2 is a promising target for the treatment of inflammatory skin conditions.

A simulation of the random and directed motion of dendritic cells in chemokine fields

Dendritic cells (DCs) are the most effective professional antigen-presenting cell. They ferry antigen from the extremities to T cells and are essential for the initiation of an adaptive immune response. Despite interest in how DCs respond to chemical stimuli, there have been few attempts to model DC migration. In this paper, we simulate the motility of DCs by modeling the generation of forces by filopodia and a force balance on the cell. The direction of fliopodial extension is coupled to differential occupancy of cognate chemokine receptors across the cell. Our model simulates chemokinesis and chemotaxis in a variety of chemical and mechanical environments. Simulated DCs undergoing chemokinesis were measured to have a speed of 5.1 ± 0.07 μm·min-1 and a persistence time of 3.2 ± 0.46 min, consistent with experiment. Cells undergoing chemotaxis exhibited a stronger chemotactic response when exposed to lower average chemokine concentrations, also consistent with experiment. We predicted that when placed in two opposing gradients, cells will cluster in a line, which we call the "line of equistimulation;" this clustering has also been observed. We calculated the effect of varying gradient steepness on the line of equistimulation, with steeper gradients resulting in tighter clustering. Moreover, gradients are found to be most potent when cells are in a gradient of chemokine whose mean concentration is close to the binding of the Kd to the receptor, and least potent when the mean concentration is 0.1Kd. Comparing our simulations to experiment, we can give a quantitative measure of the strength of certain chemokines relative to others. Assigning the signal of CCL19 binding CCR7 a baseline strength of 1, we found CCL21 binding CCR7 had a strength of 0.28, and CXCL12 binding CXCR4 had a strength of 0.30. These differences emerge despite both chemokines having virtually the same Kd, suggesting a mechanism of signal amplification in DCs requiring further study.

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.

A Single-Stranded Oligonucleotide Inhibits Toll-Like Receptor 3 Activation and Reduces Influenza A (H1N1) Infection

The initiation of an immune response is dependent on the activation and maturation of dendritic cells after sensing pathogen associated molecular patterns by pattern recognition receptors. However, the response needs to be balanced as excessive pro-inflammatory cytokine production in response to viral or stress-induced pattern recognition receptor signaling has been associated with severe influenza A virus (IAV) infection. Here, we use an inhibitor of Toll-like receptor (TLR)3, a single-stranded oligonucleotide (ssON) with the capacity to inhibit certain endocytic routes, or a TLR3 agonist (synthetic double-stranded RNA PolyI:C), to evaluate modulation of innate responses during H1N1 IAV infection. Since IAV utilizes cellular endocytic machinery for viral entry, we also assessed ssON's capacity to affect IAV infection. We first show that IAV infected human monocyte-derived dendritic cells (MoDC) were unable to up-regulate the co-stimulatory molecules CD80 and CD86 required for T cell activation. Exogenous TLR3 stimulation did not overcome the IAV-mediated inhibition of co-stimulatory molecule expression in MoDC. However, TLR3 stimulation using PolyI:C led to an augmented pro-inflammatory cytokine response. We reveal that ssON effectively inhibited PolyI:C-mediated pro-inflammatory cytokine production in MoDC, notably, ssON treatment maintained an interferon response induced by IAV infection. Accordingly, RNAseq analyses revealed robust up-regulation of interferon-stimulated genes in IAV cultures treated with ssON. We next measured reduced IAV production in MoDC treated with ssON and found a length requirement for its anti-viral activity, which overlapped with its capacity to inhibit uptake of PolyI:C. Hence, in cases wherein an overreacting TLR3 activation contributes to IAV pathogenesis, ssON can reduce this signaling pathway. Furthermore, concomitant treatment with ssON and IAV infection in mice resulted in maintained weight and reduced viral load in the lungs. Therefore, extracellular ssON provides a mechanism for immune regulation of TLR3-mediated responses and suppression of IAV infection in vitro and in vivo in mice.

Inhibition of CD83 Alleviates Systemic Inflammation in Herpes Simplex Virus Type 1-Induced Behçet's Disease Model Mouse

Behçet's disease (BD) is an autoinflammatory disease that can lead to life- and sight-threating complications. Dendritic cells (DCs) are the most potent antigen-presenting cells that can regulate multiple inflammatory pathways. The objective of this study was to investigate the association of the DC stimulatory molecule CD83 with BD. Frequencies of costimulatory molecules expressing DCs in peripheral blood leukocytes (PBL) were measured by flow cytometry (FACS). The severity of symptoms in HSV-1-induced BD symptomatic mice was also assessed. Frequencies of CD83-positive cells were significantly increased in mice exhibiting BD symptoms, compared to those in asymptomatic mice. Abatacept, a CD80/86 blocker, significantly decreased the frequencies of CD83-positive cells in a time- and dose-dependent manner. BD symptomatic mice treated with Abatacept showed gradual reduction in the severity score of symptoms. Intraperitoneal injection of CD83 siRNA significantly reduced the frequencies of CD83-positive cells in PBL and peritoneal macrophages. After CD83 siRNA injection, BD symptoms of mice were improved and disease severity was decreased. Discontinuation of CD83 siRNA deteriorated symptoms while readministration of CD83 siRNA again improved BD symptoms of mice. These results clearly indicate the involvement of CD83-expressing cells in the inflammatory symptoms of BD. Therefore, CD83 might be useful as a therapeutic target for BD.

The Janus Face of Tumor Microenvironment Targeted by Immunotherapy

The tumor microenvironment (TME) is a complex entity where host immune and non-immune cells establish a dynamic crosstalk with cancer cells. Through cell-cell interactions, which are mediated by key signals, such as the PD-1/PD-L1 axis, as well as the release of soluble mediators, this articulated process defines the nature of TME determining tumor development, prognosis, and response to therapy. Specifically, tumors are characterized by cellular plasticity that allows for the microenvironment to polarize towards inflammation or immunosuppression. Thus, the dynamic crosstalk among cancer, stromal, and immune components crucially favors the dominance of one of the Janus-faced contexture of TME crucial to the outcome of tumor development and therapeutic response. However, mostly, TME is dominated by an immunosuppressive landscape that blocks antitumor immunity and sustain tumor progression. Hence, in most cases, the immunosuppressive components of TME are highly competent in suppressing tumor-specific CD8⁺ T lymphocytes, the effectors of cancer destruction. In this complex context, immunotherapy aims to arm the hidden Janus face of TME disclosing and potentiating antitumor immune signals. Herein, we discuss recent knowledge on the immunosuppressive crosstalk within TME, and share perspectives on how immunotherapeutic approaches may exploit tumor immune signals to generate antitumor immunity.

An Anticancer Drug Cocktail of Three Kinase Inhibitors Improved Response to a Dendritic Cell-Based Cancer Vaccine

Monocyte-derived dendritic cell (moDC)-based cancer therapies intended to elicit antitumor T-cell responses have limited efficacy in most clinical trials. However, potent and sustained antitumor activity in a limited number of patients highlights the therapeutic potential of moDCs. In vitro culture conditions used to generate moDCs can be inconsistent, and moDCs generated in vitro are less effective than natural DCs. On the basis of our study highlighting the ability for certain kinase inhibitors to enhance tumor antigenicity, we therefore screened kinase inhibitors for their ability to improve DC immunogenicity. We identified AKT inhibitor MK2206, DNA-PK inhibitor NU7441, and MEK inhibitor trametinib as the compounds most effective at modulating moDC immunogenicity. The combination of these drugs, referred to as MKNUTRA, enhanced moDC activity over treatment with individual drugs while exhibiting minimal toxicity. An evaluation of 335 activation and T-cell-suppressive surface proteins on moDCs revealed that MKNUTRA treatment more effectively matured cells and reduced the expression of tolerogenic proteins as compared with control moDCs. MKNUTRA treatment imparted to ICT107, a glioblastoma (GBM) DC-based vaccine that has completed phase II trials, an increased ability to stimulate patient-derived autologous CD8+ T cells against the brain tumor antigens IL13Rα2(345-354) and TRP2(180-188) In vivo, treating ICT107 with MKNUTRA, prior to injection into mice with an established GBM tumor, reduced tumor growth kinetics. This response was associated with an increased frequency of tumor-reactive lymphocytes within tumors and in peripheral tissues. These studies broaden the application of targeted anticancer drugs and highlight their ability to increase moDC immunogenicity.

H7N9 influenza A virus activation of necroptosis in human monocytes links innate and adaptive immune responses

We previously demonstrated that avian influenza A H7N9 virus preferentially infected CD14⁺ monocyte in human peripheral blood mononuclear cells (PBMCs), which led to apoptosis. To better understand H7N9 pathogenesis in relation to monocyte cell death, we showed here that extensive phosphorylation of mixed lineage kinase domain-like (MLKL) protein occurred concurrently with the activation of caspases-8, -9 and -3 in H7N9-infected monocytes at 6 h post infection (hpi), indicating that apoptosis and necroptosis pathways were simultaneously activated. The apoptotic morphology was readily observed in H7N9-infected monocytes with transmission electron microscopy (TEM), while the pan-caspase inhibitor, IDN6556 (IDN), accelerated cell death through necroptosis as evidenced by the increased level of pMLKL accompanied with cell swelling and plasma membrane rupture. Most importantly, H7N9-induced cell death could only be stopped by the combined treatment of IDN and necrosulfonamide (NSA), a pMLKL membrane translocation inhibitor, but not by individual inhibition of caspase or RIPK3. Our data further showed that activation of apoptosis and necroptosis pathways in monocytes differentially contributed to the immune response of monocytes upon H7N9 infection. Specifically, caspase inhibition significantly enhanced, while RIPK3 inhibition reduced the early expression of type I interferons and cytokine/chemokines in H7N9-infected monocytes. Moreover, culture supernatants from IDN-treated H7N9-infected monocyte promoted the expression of co-stimulatory molecule CD80, CD83 and CD86 on freshly isolated monocytes and monocyte-derived dendritic cells (MDCs) and enhanced the capacity of MDCs to induce CD3⁺ T-cell proliferation in vitro. In contrast, these immune stimulatory effects were abrogated by using culture supernatants from H7N9-infected monocyte with RIPK3 inhibition. In conclusion, our findings indicated that H7N9 infection activated both apoptosis and necroptosis in monocytes. An intact RIPK3 activity is required for upregulation of innate immune responses, while caspase activation suppresses the immune response.

NKT Cell-Driven Enhancement of Antitumor Immunity Induced by Clec9a-Targeted Tailorable Nanoemulsion

Invariant natural killer T (iNKT) cells are a subset of lymphocytes with immune regulatory activity. Their ability to bridge the innate and adaptive immune systems has been studied using the glycolipid ligand α-galactosylceramide (αGC). To better harness the immune adjuvant properties of iNKT cells to enhance priming of antigen-specific CD8⁺ T cells, we encapsulated both αGC and antigen in a Clec9a-targeted nanoemulsion (TNE) to deliver these molecules to cross-presenting CD8⁺ dendritic cells (DC). We demonstrate that, even in the absence of exogenous glycolipid, iNKT cells supported the maturation of CD8α⁺ DCs to drive efficient cross-priming of antigen-specific CD8⁺ T cells upon delivery of Clec9a/OVA-TNE. The addition of αGC to the TNE (Clec9a/OVA/αGC) further enhanced activation of iNKT cells, NK cells, CD8α⁺ DCs, and polyfunctional CD8⁺ T cells. When tested therapeutically against HPVE7-expressing TC-1 tumors, long-term tumor suppression was achieved with a single administration of Clec9a/E7 peptide/αGC TNE. Antitumor activity was correlated with the recruitment of mature DCs, NK cells, and tumor-specific effector CD8⁺ T cells to the tumor-draining lymph node and tumor tissue. Thus, Clec9a-TNE codelivery of CD8⁺ T-cell epitopes with αGC induces alternative helper signals from activated iNKT cells, elicits innate (iNKT, NK) immunity, and enhances antitumor CD8⁺ T-cell responses for control of solid tumors.

Enhancing Antigen Cross-Presentation in Human Monocyte-Derived Dendritic Cells by Recruiting the Intracellular Fc Receptor TRIM21

Suboptimal immune responses to pathogens contribute to chronic infections. One way to improve immune responses is to boost Ag presentation. In this study, we investigate the potential of the tripartite motif-containing 21 (TRIM21) pathway. TRIM21 is a ubiquitously expressed cytosolic protein that recognizes the Fc region of Abs. When Abs that are bound to pathogens enter the cell as immune complexes, binding of TRIM21 to Fc initiates downstream inflammatory signaling and targets the immune complexes for proteasomal degradation. In APCs, peptides generated by proteasomes are loaded onto MHC class I molecules to stimulate CD8 T cell responses, which are crucial for effective immunity to pathogens. We hypothesized that increasing the affinity between immune complexes and TRIM21 might markedly improve CD8 T cell responses to Ags processed by the TRIM21 pathway. Using phage display technology, we engineered the human IgG1 Fc to increase its affinity for TRIM21 by 100-fold. Adenovirus immune complexes with the engineered Fc induced greater maturation of human dendritic cells (DC) than immune complexes with unmodified Fc and stimulated increased Ag-specific CD8 T cell proliferation and IFN-γ release in cocultures of DC-PBMC. Thus, by increasing the affinity between Fc and TRIM21, Ags from immune complexes undergo enhanced cross-presentation on DC, leading to greater CD8 T cell responses. Our study reveals an approach that could potentially be used in vaccines to increase cytotoxic T cell responses against Ags that are targeted or delivered by Fc-modified Abs.

Human Dendritic Cells: Their Heterogeneity and Clinical Application Potential in Cancer Immunotherapy

Dendritic cells (DC) are professional antigen presenting cells, uniquely able to induce naïve T cell activation and effector differentiation. They are, likewise, involved in the induction and maintenance of immune tolerance in homeostatic conditions. Their phenotypic and functional heterogeneity points to their great plasticity and ability to modulate, according to their microenvironment, the acquired immune response and, at the same time, makes their precise classification complex and frequently subject to reviews and improvement. This review will present general aspects of the DC physiology and classification and will address their potential and actual uses in the management of human disease, more specifically cancer, as therapeutic and monitoring tools. New combination treatments with the participation of DC will be also discussed.

IL-6 Signaling Blockade during CD40-Mediated Immune Activation Favors Antitumor Factors by Reducing TGF-β, Collagen Type I, and PD-L1/PD-1

IL-6 plays a role in cancer pathogenesis via its connection to proteins involved in the formation of desmoplastic stroma and to immunosuppression by driving differentiation of myeloid suppressor cells together with TGF-β. Inhibition of IL-6 signaling in the tumor microenvironment may, thus, limit desmoplasia and myeloid suppressor cell differentiation. CD40 signaling can further revert myeloid cell differentiation toward antitumor active phenotypes. Hence, the simultaneous use of IL-6 blockade with CD40 stimuli may tilt the tumor microenvironment to promote antitumor immune responses. In this paper, we evaluated the mechanisms of LOAd713, an oncolytic adenovirus designed to block IL-6R signaling and to provide myeloid cell activation via a trimerized membrane-bound isoleucine zipper (TMZ) CD40L. LOAd713-infected pancreatic cancer cells were killed by oncolysis, whereas infection of stellate cells reduced factors involved in stroma formation, including TGF-β-1 and collagen type I. Virus infection prevented IL-6/GM-CSF-mediated differentiation of myeloid suppressors, but not CD163 macrophages, whereas infection of dendritic cells led to upregulation of maturation markers, including CD83, CD86, IL-12p70, and IFN-γ. Further, IL-6R blockade prevented upregulation of programed death ligand 1 (PD-L1) and PD-1 on the stimulated dendritic cells. These results suggest that LOAd713 can kill infected tumor cells and has the capacity to affect the tumor microenvironment by stimulating stellate cells and myeloid suppressors with TMZ-CD40L and IL-6R blockade. Gene transfer of murine TMZ-CD40L prolonged survival in an animal model. LOAd713 may be an interesting therapeutic option for cancers connected to IL-6 signaling, such as pancreatic cancer.

Age-Associated Changes in the Respiratory Epithelial Response to Influenza Infection

Older adults suffer a disproportionate burden of influenza-related morbidity and mortality typically attributed to defects in the aging immune system collectively known as immunosenescence. While the age-related decline in the adaptive immune system has been well characterized, little is known about how aging affects the principal site of influenza infection-the nasal epithelium. In human nasal epithelial cell cultures (hNECs) from older adults, we found similar or increased levels of cytokines during influenza infection compared with hNECs from younger individuals. However, hNECs from older individuals demonstrated decreased mRNA expression for several key proteins that affect clearance of infected cells, including MHC-I and transporter associated with antigen presentation (TAP). These findings were confirmed at the level of protein expression. In vivo studies corroborated the in vitro differences in MHC-I and TAP gene expression and also revealed important decreases in the expression of key influenza-specific antiviral mediators MX1 and IFITM1. Furthermore, epithelial cell-cytotoxic T lymphocyte co-cultures demonstrate that CTL cytotoxic activity is dose-dependent on MHC-I antigen presentation. Taken together, these results indicate that aging is associated with important changes in the nasal epithelium, including antigen presentation and antiviral pathways, which may contribute to increased severity of disease in older adults through impaired clearance of infected cells.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Attenuate Dendritic Cell Maturation and Function

Mesenchymal stromal cells (MSCs) are potent regulators of immune responses largely through paracrine signaling. MSC secreted extracellular vesicles (MSC-EVs) are increasingly recognized as the key paracrine factors responsible for the biological and therapeutic function of MSCs. We report the first comprehensive study demonstrating the immunomodulatory effect of MSC-EVs on dendritic cell (DC) maturation and function. MSC-EVs were isolated from MSC conditioned media using differential ultracentrifugation. Human monocyte-derived DCs were generated in the absence or presence of MSC-EVs (20 ug/ml) then subjected to phenotypic and functional analysis in vitro. MSC-EV treatment impaired antigen uptake by immature DCs and halted DC maturation resulting in reduced expression of the maturation and activation markers CD83, CD38, and CD80, decreased secretion of pro-inflammatory cytokines IL-6 and IL-12p70 and increased production of anti-inflammatory cytokine TGF-β. MSC-EV treated DCs also demonstrated a diminished CCR 7 expression after LPS stimulation, coupled with a significantly reduced ability to migrate toward the CCR7-ligand CCL21, although they were still able to stimulate allogeneic T cell proliferation in vitro. Through microRNA profiling we have identified 49 microRNAs, which were significantly enriched in MSC-EVs compared to their parent MSCs. MicroRNAs with known effect on DC maturation and functions, including miR-21-5p, miR-142-3p, miR-223-3p, and miR-126-3p, were detected within the top 10 most enriched miRNAs in MSC-EVs, with MiR-21-5p as the third highest expressed miRNA in MSC-EVs. In silico analysis revealed that miR-21-5p targets the CCR7 gene for degradation. To verify these observations, DCs were transfected with miR-21-5p mimics and analyzed for their ability to migrate toward the CCR7-ligand CCL21 in vitro. MiR-21-5p mimic transfected DCs showed a clear trend of reduced CCR7 expression and a significantly decreased migratory ability toward the CCL21. Our findings suggest that MSC-EVs are able to recapitulate MSC mediated DC modulation and MSC-EV enclosed microRNAs may represent a novel mechanism through which MSCs modulate DC functions. As MSCs are currently used in clinical trials to treat numerous diseases associated with immune dysregulation, such as graft-versus-host disease and inflammatory bowel disease, our data provide novel evidence to inform potential future application of MSC-EVs as a cell-free therapeutic agent.

Miniaturized High-Throughput Multiparameter Flow Cytometry Assays Measuring In Vitro Human Dendritic Cell Maturation and T-Cell Activation in Mixed Lymphocyte Reactions

Enhancing antitumor activities of the human immune system is a clinically proven approach with the advent of monoclonal antibodies recognizing programmed cell death protein-1 (PD1) receptors on immune cell surfaces. Historically, using flow cytometry as a means to assess next-generation agent activities was underused, largely due to limits on cell number and assay sensitivity. Here, we leveraged an IntelliCyt high-throughput flow cytometry platform to monitor human dendritic cell maturation and lymphocyte proliferation in mixed lymphocyte reactions. Specifically, we established flow cytometry-based immunophenotyping and screening methodologies capable of measuring T-cell activation as a result of cell-associated antigens presented on dendritic cell surfaces, as indicated by cell proliferation, cytokine secretion, and surface marker expression. Together, the overall novelty of this 384-well platform is its capability to measure multiple functional readouts in one well and consistently evaluate large numbers of compounds in a single study, as well as its ability to show increased assay sensitivity requiring considerably fewer primary cells and less reagents compared to more traditional 96-well flow cytometry methods.

Development and Functional Characterization of Murine Tolerogenic Dendritic Cells

The immune system operates by maintaining a tight balance between coordinating responses against foreign antigens and maintaining an unresponsive state against self-antigens as well as antigens derived from commensal organisms. The disruption of this immune homeostasis can lead to chronic inflammation and to the development of autoimmunity. Dendritic cells (DCs) are the professional antigen-presenting cells of the innate immune system involved in activating naïve T cells to initiate immune responses against foreign antigens. However, DCs can also be differentiated into TolDCs that act to maintain and promote T cell tolerance and to suppress effector cells contributing to the development of either autoimmune or chronic inflammation conditions. The recent advancement in our understanding of TolDCs suggests that DC tolerance can be achieved by modulating their differentiation conditions. This phenomenon has led to tremendous growth in developing TolDC therapies for numerous immune disorders caused due to break in immune tolerance. Successful studies in preclinical autoimmunity murine models have further validated the immunotherapeutic utility of TolDCs in the treatment of autoimmune disorders. Today, TolDCs have become a promising immunotherapeutic tool in the clinic for reinstating immune tolerance in various immune disorders by targeting pathogenic autoimmune responses while leaving protective immunity intact. Although an array of strategies has been proposed by multiple labs to induce TolDCs, there is no consistency in characterizing the cellular and functional phenotype of these cells. This protocol provides a step-by-step guide for the development of bone marrow-derived DCs in large numbers, a unique method used to differentiate them into TolDCs with a synthetic triterpenoid 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid-difluoro-propyl-amide (CDDO-DFPA), and the techniques used to confirm their phenotype, including analyses of essential molecular signatures of TolDCs. Finally, we show a method to assess TolDC function by testing their immunosuppressive response in vitro and in vivo in a preclinical model of multiple sclerosis.

Bags versus flasks: a comparison of cell culture systems for the production of dendritic cell-based immunotherapies

In recent years, cell-based therapies targeting the immune system have emerged as promising strategies for cancer treatment. This review summarizes manufacturing challenges related to production of antigen presenting cells as a patient-tailored cancer therapy. Understanding cell-material interactions is essential because in vitro cell culture manipulations to obtain mature antigen-producing cells can significantly alter their in vivo performance. Traditional antigen-producing cell culture protocols often rely on cell adhesion to surface-treated hydrophilic polystyrene flasks. More recent commercial and investigational cancer immunotherapy products were manufactured using suspension cell culture in closed hydrophobic fluoropolymer bags. The shift to closed cell culture systems can decrease risks of contamination by individual operators, as well as facilitate scale-up and automation. Selecting closed cell culture bags over traditional open culture systems entails different handling procedures and processing controls, which can affect product quality. Changes in culture vessels also entail changes in vessel materials and geometry, which may alter the cell microenvironment and resulting cell fate decisions. Strategically designed culture systems will pave the way for the generation of more sophisticated and highly potent cell-based cancer vaccines. As an increasing number of cell-based therapies enter the clinic, the selection of appropriate cell culture vessels and materials becomes a critical consideration that can impact the therapeutic efficacy of the product, and hence clinical outcomes and patient quality of life.

Dendritic Cell-Based Immunotherapy for Solid Tumors

As a treatment for solid tumors, dendritic cell (DC)-based immunotherapy has not been as effective as expected. Here, we review the reasons underlying the limitations of DC-based immunotherapy for solid tumors and ask what can be done to improve immune cell-based cancer therapies. Several reports show that, rather than a lack of immune induction, the limited efficacy of DC-based immunotherapy in cases of renal cell carcinoma (RCC) likely results from inhibition of immune responses by tumor-secreted TGF-β and an increase in the number of regulatory T (Treg) cells in and around the solid tumor. Indeed, unlike DC therapy for solid tumors, cytotoxic T lymphocyte (CTL) responses induced by DC therapy inhibit tumor recurrence after surgery; CTL responses also limit tumor metastasis induced by additional tumor-challenge in RCC tumor-bearing mice. Here, we discuss the mechanisms underlying the poor efficacy of DC-based therapy for solid tumors and stress the need for new and improved DC immunotherapies and/or combination therapies with killer cells to treat resistant solid tumors.

Atypical activation of dendritic cells by Plasmodium falciparum

Dendritic cells (DCs) are activated by pathogens to initiate and shape immune responses. We found that the activation of DCs by Plasmodium falciparum, the main causative agent of human malaria, induces a highly unusual phenotype by which DCs up-regulate costimulatory molecules and secretion of chemokines, but not of cytokines typical of inflammatory responses (IL-1β, IL-6, IL-10, TNF). Similar results were obtained with DCs obtained from malaria-naïve US donors and malaria-experienced donors from Mali. Contact-dependent cross-talk between the main DC subsets, plasmacytoid and myeloid DCs (mDCs) was necessary for increased chemokine and IFN-α secretion in response to the parasite. Despite the absence of inflammatory cytokine secretion, mDCs incubated with P. falciparum-infected erythrocytes activated antigen-specific naïve CD4⁺ T cells to proliferate and secrete Th1-like cytokines. This unexpected response of human mDCs to P. falciparum exhibited a transcriptional program distinct from a classical LPS response, pointing to unique P. falciparum-induced activation pathways that may explain the uncharacteristic immune response to malaria.

p21 Restricts HIV-1 in Monocyte-Derived Dendritic Cells through the Reduction of Deoxynucleoside Triphosphate Biosynthesis and Regulation of SAMHD1 Antiviral Activity

HIV-1 infection of noncycling cells, such as dendritic cells (DCs), is impaired due to limited availability of deoxynucleoside triphosphates (dNTPs), which are needed for HIV-1 reverse transcription. The levels of dNTPs are tightly regulated during the cell cycle and depend on the balance between dNTP biosynthesis and degradation. SAMHD1 potently blocks HIV-1 replication in DCs, although the underlying mechanism is still unclear. SAMHD1 has been reported to be able to degrade dNTPs and viral nucleic acids, which may both hamper HIV-1 reverse transcription. The relative contribution of these activities may differ in cycling and noncycling cells. Here, we show that inhibition of HIV-1 replication in monocyte-derived DCs (MDDCs) is associated with an increased expression of p21cip1/waf, a cell cycle regulator that is involved in the differentiation and maturation of DCs. Induction of p21 in MDDCs decreases the pool of dNTPs and increases the antiviral active isoform of SAMHD1. Although both processes are complementary in inhibiting HIV-1 replication, the antiviral activity of SAMHD1 in our primary cell model appears to be, at least partially, independent of its dNTPase activity. The reduction in the pool of dNTPs in MDDCs appears rather mostly due to a p21-mediated suppression of several enzymes involved in dNTP synthesis (i.e., RNR2, TYMS, and TK-1). These results are important to better understand the interplay between HIV-1 and DCs and may inform the design of new therapeutic approaches to decrease viral dissemination and improve immune responses against HIV-1.IMPORTANCE DCs play a key role in the induction of immune responses against HIV. However, HIV has evolved ways to exploit these cells, facilitating immune evasion and virus dissemination. We have found that the expression of p21, a cyclin-dependent kinase inhibitor involved in cell cycle regulation and monocyte differentiation and maturation, potentially can contribute to the inhibition of HIV-1 replication in monocyte-derived DCs through multiple mechanisms. p21 decreased the size of the intracellular dNTP pool. In parallel, p21 prevented SAMHD1 phosphorylation and promoted SAMHD1 dNTPase-independent antiviral activity. Thus, induction of p21 resulted in conditions that allowed the effective inhibition of HIV-1 replication through complementary mechanisms. Overall, p21 appears to be a key regulator of HIV infection in myeloid cells.

miR-181d regulates human dendritic cell maturation through NF-κB pathway

OBJECTIVES

MicroRNAs (miRNAs) are considered as the cellular regulators which post-transcriptionally modulate gene expression in diverse biological processes including cell development and immunity. In this study, we investigated functions of miR-181d in dendritic cells (DCs) maturation, and the underlying mechanisms were also explored.

MATERIALS AND METHODS

Here we did the miRNA screening in human DCs in response to lipopolysaccharides (LPS) by quantitative real-time PCR (qRT-PCR). The expressions of DCs maturation markers were measured after miRNA mimics transfections. The pharmacological inhibitors of signalling pathways were applied to examine miR-181d effect on DCs maturation by Western blot. Luciferase assay and mixed lymphocyte reaction (MLR) were also performed to reveal the target gene of miR-181d and test the viability of T cells treated with miR-181d transfected DCs.

RESULTS

Overexpression of miR-181d per se is sufficient to promote DCs maturation, and up-regulate CD80 and CD83 expressions without LPS. Besides, we showed that miR-181d activated NF-κB pathway and also promoted the expression of pro-inflammatory cytokine IL12 and TNF-α. Inhibition of NF-κB pathway suppressed DCs maturation. Luciferase reporter assay and target gene knockdown assay indicated that miR-181d targets regulator cylindromatosis (CYLD), a primary negative regulator of NF-κB pathway. MLR assay showed that miR-181d-transfected DCs could promote T-cell proliferation than iDCs in vitro.

CONCLUSION

Our study demonstrates that miR-181d is required for DCs maturation through the activation of NF-κB pathway by targeting CYLD.

Immunomonitoring reveals interruption of anergy after vaccination in a case of type-2-papillary renal cell carcinoma

With the enormous and growing interest in the clinical application of immunotherapy, we are currently facing the need to accurately monitor the immune function of cancer patients. Here, we describe changes in the immune status of a patient with metastatic type-2-papillary renal cell carcinoma, before and after surgery and subsequent immunotherapy with a dendritic cell-tumor cell hybrid vaccine. Through the accurate assessment of monocyte-derived dendritic cells (Mo-DCs) function, we show that Mo-DCs were freed from tumor-induced maturation blockage by tumor resection surgery, while Mo-DCs-tumor induced suppression and anergy were only interrupted by the vaccination treatment. Our data suggest that the evaluation of Mo-DCs' function may provide a powerful and precise tool to monitor immune restoration in cancer patients.

Thymoquinone as a Potential Adjuvant Therapy for Cancer Treatment: Evidence from Preclinical Studies

Thymoquinone (TQ), the main bioactive component of Nigella sativa, has been found to exhibit anticancer effects in numerous preclinical studies. Due to its multitargeting nature, TQ interferes in a wide range of tumorigenic processes and counteracts carcinogenesis, malignant growth, invasion, migration, and angiogenesis. Moreover, TQ can specifically sensitize tumor cells toward conventional cancer treatments (e.g., radiotherapy, chemotherapy, and immunotherapy) and simultaneously minimize therapy-associated toxic effects in normal cells. In this review, we summarized the adjuvant potential of TQ as observed in various in vitro and in vivo animal models and discussed the pharmacological properties of TQ to rationalize its supplementary role in potentiating the efficacy of standard therapeutic modalities namely surgery, radiotherapy, chemotherapy, and immunotherapy. Altogether, we suggest further comprehensive evaluation of TQ in preclinical and clinical levels to delineate its implied utility as a novel complementary adjuvant therapy for cancer treatment.

Human monocyte-derived dendritic cells exposed to hyperthermia show a distinct gene expression profile and selective upregulation of IGFBP6

Fever plays a role in activating innate immunity while its relevance in activating adaptive immunity is less clear. Even brief exposure to elevated temperatures significantly impacts on the immunostimulatory capacity of dendritic cells (DCs), but the consequences on immune response remain unclear. To address this issue, we analyzed the gene expression profiles of normal human monocyte-derived DCs from nine healthy adults subjected either to fever-like thermal conditions (39°C) or to normal temperature (37°C) for 180 minutes. Exposure of DCs to 39°C caused upregulation of 43 genes and downregulation of 24 genes. Functionally, the up/downregulated genes are involved in post-translational modification, protein folding, cell death and survival, and cellular movement. Notably, when compared to monocytes, DCs differentially upregulated transcription of the secreted protein IGFBP-6, not previously known to be specifically linked to hyperthermia. Exposure of DCs to 39°C induced apoptosis/necrosis and resulted in accumulation of IGFBP-6 in the conditioned medium at 48 h. IGFBP-6 may have a functional role in the hyperthermic response as it induced chemotaxis of monocytes and T lymphocytes, but not of B lymphocytes. Thus, temperature regulates complex biological DC functions that most likely contribute to their ability to induce an efficient adaptive immune response.