Reprogramming Of Dendritic Cells Research Articles

Restoring tumor immunogenicity with dendritic cell reprogramming.

Decreased antigen presentation contributes to the ability of cancer cells to evade the immune system. We used the minimal gene regulatory network of type 1 conventional dendritic cells (cDC1) to reprogram cancer cells into professional antigen-presenting cells (tumor-APCs). Enforced expression of the transcription factors PU.1, IRF8, and BATF3 (PIB) was sufficient to induce the cDC1 phenotype in 36 cell lines derived from human and mouse hematological and solid tumors. Within 9 days of reprogramming, tumor-APCs acquired transcriptional and epigenetic programs associated with cDC1 cells. Reprogramming restored the expression of antigen presentation complexes and costimulatory molecules on the surfaces of tumor cells, allowing the presentation of endogenous tumor antigens on MHC-I and facilitating targeted killing by CD8+ T cells. Functionally, tumor-APCs engulfed and processed proteins and dead cells, secreted inflammatory cytokines, and cross-presented antigens to naïve CD8+ T cells. Human primary tumor cells could also be reprogrammed to increase their capability to present antigen and to activate patient-specific tumor-infiltrating lymphocytes. In addition to acquiring improved antigen presentation, tumor-APCs had impaired tumorigenicity in vitro and in vivo. Injection of in vitro generated melanoma-derived tumor-APCs into subcutaneous melanoma tumors delayed tumor growth and increased survival in mice. Antitumor immunity elicited by tumor-APCs was synergistic with immune checkpoint inhibitors. Our approach serves as a platform for the development of immunotherapies that endow cancer cells with the capability to process and present endogenous tumor antigens.

Abstract 6384: ATG-034, an LILRB4 antagonist antibody, reinvigorates dendritic cells and prevents tumor progression

Abstract Background: Dendritic cells (DCs) are vital for initiating antigen-specific T cell-dependent antitumor immune responses. However, emerging evidence reveals that local DCs within the tumor microenvironment (TME) are tolerized to facilitate immune evasion. Reprogramming of DCs is recognized as a promising strategy for tumor immunotherapy. Leukocyte immunoglobulin-like receptor B4 (LILRB4) is an inhibitory receptor belonging to the LILR family which is mainly expressed on normal myeloid cells and myeloid-derived malignant cells. It is upregulated on tolerogenic DCs (tolDCs), which exhibit low expression levels of costimulatory molecules and resistance to DC maturation. Targeting LILRB4 to reprogram tolDCs has been reported to be a promising strategy for cancer treatment. Here we report the preclinical development of an LILRB4 antagonist antibody, ATG-034. Method: The protein-based and cell-based binding affinity of ATG-034 were measured using SPR, ELISA and FACS analysis. Fc receptor (FcR) stimulation assay was used to evaluate the ability of ATG-034 to block the interaction of LILRB4 with its ligand fibronectin. ATG-034-mediated enhancement of antigen presentation and co-stimulation ability of DCs was determined by FACS analysis for the change of surface expression of HLA-DR, HLA-ABC, CD86, and CD206. The mixed lymphocyte reaction (MLR) assay was used to assess the immunomodulatory potential of ATG-034. The in vivo antitumor efficacy of ATG-034 was evaluated in a radiation therapy-resistant murine Lewis lung carcinoma (LLC) syngeneic model. Results: ATG-034 binds to LILRB4 protein with a single-digit nM affinity. It potently reversed the fibronectin-mediated inhibition of FcR-driven TNF-α cytokine production. TolDCs were reprogrammed by ATG-034 to immunogenic DCs with significant upregulation of the expression of HLA-DR, HLA-ABC, CD86 and downregulation of the expression of CD206. Furthermore, ATG-034 remarkably reinvigorated tolDCs for priming T cell activation with noticeable upregulation of the expression of CD25 and the secretion of IFN-γ, enhancing antitumor immunity. In addition, 10 mg/kg ATG-034 significantly inhibited the LLC tumor growth in vivo with a TGI of 40.28%, while a benchmark antibody only demonstrated a 24.43% TGI. Conclusion: Our data show that ATG-034 reprograms tolDC, enhancing anti-tumor immunity, and demonstrates potent in vivo anti-tumor efficacy. Therefore, ATG-034 may be a promising strategy for the treatment of cancer. Citation Format: Ao Sun, Enlin Zheng, Huili Cao, Mengshi Cao, Suya Bai, Peng Chen, Linjie Tian, Jay Mei, Bo Shan, Bing Hou. ATG-034, an LILRB4 antagonist antibody, reinvigorates dendritic cells and prevents tumor progression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 6384.

Dual RNA sequencing reveals dendritic cell reprogramming in response to typhoidal Salmonella invasion

Salmonella enterica represent a major disease burden worldwide. S. enterica serovar Typhi (S. Typhi) is responsible for potentially life-threatening Typhoid fever affecting 10.9 million people annually. While non-typhoidal Salmonella (NTS) serovars usually trigger self-limiting diarrhoea, invasive NTS bacteraemia is a growing public health challenge. Dendritic cells (DCs) are key professional antigen presenting cells of the human immune system. The ability of pathogenic bacteria to subvert DC functions and prevent T cell recognition contributes to their survival and dissemination within the host. Here, we adapted dual RNA-sequencing to define how different Salmonella pathovariants remodel their gene expression in tandem with that of infected DCs. We find DCs harness iron handling pathways to defend against invading Salmonellas, which S. Typhi is able to circumvent by mounting a robust response to nitrosative stress. In parallel, we uncover the alternative strategies invasive NTS employ to impair DC functions.

Immune synapse instructs epigenomic and transcriptomic functional reprogramming in dendritic cells.

Immune synapse instructs epigenomic and transcriptomic functional reprogramming in dendritic cells.

Genetic regulation of nitric oxide-mediated metabolic reprogramming in dendritic cells

Abstract Dendritic cell (DC) activation is characterized by a rapid “metabolic switch” towards increased glycolysis that supports maturation. Sustained glycolysis post-activation is a requirement for survival in DC subsets that express inducible nitric oxide synthase (Nos2, iNOS), due to the production of nitric oxide (NO) which acts as an inhibitor of mitochondrial respiration. Long-term metabolic reprogramming in activated DCs has almost exclusively been studied in the strain C57BL/6J (B6), which experience loss of mitochondrial function due to NO accumulation. To assess the conservation of NO-driven metabolic regulation in DCs, we generated and compared DCs from B6 mice to the wild-derived genetically diverse PWD/PhJ (PWD) strain. We show attenuated iNOS induction, lowered NO production, and intact mitochondrial respiration in activated PWD DCs. To reduce genetic variability in our model, we generated DCs from a congenic mouse strain containing a genetic interval from PWD—including Nos2—on a B6 background. Activated DCs from the congenic strain produce NO at lower levels than B6, but NO production is not completely ablated as it is for pharmacologic or genetic interventions, thus this model allows for the subtle interrogation of NO-mediated metabolic reprogramming. We show that glucose-dependent carbon flux through the TCA cycle is altered in DCs with restrained NO production compared to B6 DCs, and we demonstrate that these differences are driven by NO. These studies provide a more comprehensive understanding of NO-mediated metabolic reprogramming in the murine myeloid lineage and establish a natural genetic model for investigating the contribution of NO in regulating the interplay between DC metabolism and immune function.

Immune synapse instructs epigenomic and transcriptomic functional reprogramming in dendritic cells.

Understanding the fate of dendritic cells (DCs) after productive immune synapses (postsynaptic DCs) with T cells during antigen presentation has been largely neglected in favor of deciphering the nuances of T cell activation and memory generation. Here, we describe that postsynaptic DCs switch their transcriptomic signature, correlating with epigenomic changes including DNA accessibility and histone methylation. We focus on the chemokine receptor Ccr7 as a proof-of-concept gene that is increased in postsynaptic DCs. Consistent with our epigenomic observations, postsynaptic DCs migrate more efficiently toward CCL19 in vitro and display enhanced homing to draining lymph nodes in vivo. This work describes a previously unknown DC population whose transcriptomics, epigenomics, and migratory capacity change in response to their cognate contact with T cells.

Dynamic metabolic reprogramming in dendritic cells: An early response to influenza infection that is essential for effector function.

Infection with the influenza virus triggers an innate immune response that initiates the adaptive response to halt viral replication and spread. However, the metabolic response fueling the molecular mechanisms underlying changes in innate immune cell homeostasis remain undefined. Although influenza increases parasitized cell metabolism, it does not productively replicate in dendritic cells. To dissect these mechanisms, we compared the metabolism of dendritic cells to that of those infected with active and inactive influenza A virus and those treated with toll-like receptor agonists. Using quantitative mass spectrometry, pulse chase substrate utilization assays and metabolic flux measurements, we found global metabolic changes in dendritic cells 17 hours post infection, including significant changes in carbon commitment via glycolysis and glutaminolysis, as well as mitochondrial respiration. Influenza infection of dendritic cells led to a metabolic phenotype distinct from that induced by TLR agonists, with significant resilience in terms of metabolic plasticity. We identified c-Myc as one transcription factor modulating this response. Restriction of c-Myc activity or mitochondrial substrates significantly changed the immune functions of dendritic cells, such as reducing motility and T cell activation. Transcriptome analysis of inflammatory dendritic cells isolated following influenza infection showed similar metabolic reprogramming occurs in vivo. Thus, early in the infection process, dendritic cells respond with global metabolic restructuring, that is present in inflammatory lung dendritic cells after infection, and this is important for effector function. These findings suggest metabolic switching in dendritic cells plays a vital role in initiating the immune response to influenza infection.

Direct Reprogramming of Mouse Embryonic Fibroblasts to Conventional Type 1 Dendritic Cells by Enforced Expression of Transcription Factors.

Ectopic expression of transcription factor combinations has been recently demonstrated to reprogram differentiated somatic cells towards the dendritic cell (DC) lineage without reversion to a multipotent state. DCs have the ability to induce potent and long-lasting adaptive immune responses. In particular, conventional type 1 DCs (cDC1s) excel on antigen cross-presentation, a critical step for inducing CD8+ T cell cytotoxic responses. The rarity of naturally occurring cDC1s and lack of in vitro methodologies for the generation of pure cDC1 populations strongly hinders the study of cDC1 lineage specification and function. Here, we describe a protocol for the generation of induced DCs (iDCs) by lentiviral-mediated expression of the transcription factors PU.1, IRF8 and BATF3 in mouse embryonic fibroblasts. iDCs acquire DC morphology, cDC1 phenotype and transcriptional signatures within 9 days. iDCs generated with this protocol acquire functional ability to respond to inflammatory stimuli, engulf dead cells, process and cross-present antigens to CD8+ T cells. DC reprogramming provides a simple and tractable system to generate high numbers of cDC1-like cells for high content screening, opening new avenues to better understand cDC1 specification and function. In the future, faithful induction of cDC1 fate in fibroblasts may lead to the generation of patient-specific DCs for vaccination.

Syk-dependent glycolytic reprogramming in dendritic cells regulates IL-1β production to β-glucan ligands in a TLR-independent manner.

Dendritic cells (DCs) activated via TLR ligation experience metabolic reprogramming, in which the cells are heavily dependent on glucose and glycolysis for the synthesis of molecular building blocks essential for maturation, cytokine production, and the ability to stimulate T cells. Although the TLR‐driven metabolic reprogramming events are well documented, fungal‐mediated metabolic regulation via C‐type lectin receptors such as Dectin‐1 and Dectin‐2 is not clearly understood. Here, we show that activation of DCs with fungal‐associated β‐glucan ligands induces acute glycolytic reprogramming that supports the production of IL‐1β and its secretion subsequent to NOD‐, LRR‐ and pyrin domain‐containing protein 3 (NLRP3) inflammasome activation. This acute glycolytic induction in response to β‐glucan ligands requires spleen tyrosine kinase signaling in a TLR‐independent manner, suggesting now that different classes of innate immune receptors functionally induce conserved metabolic responses to support immune cell activation. These studies provide new insight into the complexities of metabolic regulation of DCs immune effector function regarding cellular activation associated with protection against fungal microbes.

Syk-dependent Glycolytic Reprogramming in Dendritic Cells Regulates IL-1-beta Production to Fungal-assoicated Ligands in a TLR-independent Manner

Abstract Dendritic cells (DCs) activated via TLR ligation experience metabolic reprogramming, in which the cells are heavily dependent on glucose and glycolysis for the synthesis of molecular building blocks essential for maturation, cytokine production, and the ability to stimulate T cells. Although the TLR-driven metabolic reprogramming events are well documented, fungal-mediated metabolic regulation via C-type Lectin Receptors such as Dectin-1 is not clearly understood. Here, we show that activation of DCs with fungal-associated ligands induces acute glycolytic reprogramming that supports the production of IL-1b via inflammasome activation. This acute glycolytic induction to fungal-associated ligands is depending on Syk signaling in a TLR-independent manner, suggesting now that different classes of innate immune receptors functionally induce conserved metabolic responses to support immune cell activation. These studies provide new insight into the complexities of metabolic regulation of DCs immune effector function regarding cellular activation associated with protection against fungal microbes.

TLR4 antagonist FP7 inhibits LPS-induced cytokine production and glycolytic reprogramming in dendritic cells, and protects mice from lethal influenza infection

Dysregulated Toll-like receptor (TLR)-4 activation is involved in acute systemic sepsis, chronic inflammatory diseases, such as atherosclerosis and diabetes, and in viral infections, such as influenza infection. Thus, therapeutic control of the TLR4 signalling pathway is of major interest. Here we tested the activity of the small-molecule synthetic TLR4 antagonist, FP7, in vitro on human monocytes and monocyte-derived dendritic cells (DCs) and in vivo during influenza virus infection of mice. Our results indicate that FP7 antagonized the secretion of proinflammatory cytokines (IL-6, IL-8, and MIP-1β) by monocytes and DCs (IC50 < 1 μM) and prevented DC maturation upon TLR4 activation by ultrapure lipopolysaccharide (LPS). FP7 selectively blocked TLR4 stimulation, but not TLR1/2, TLR2/6, or TLR3 activation. TLR4 stimulation of human DCs resulted in increased glycolytic activity that was also antagonized by FP7. FP7 protected mice from influenza virus-induced lethality and reduced both proinflammatory cytokine gene expression in the lungs and acute lung injury (ALI). Therefore, FP7 can antagonize TLR4 activation in vitro and protect mice from severe influenza infection, most likely by reducing TLR4-dependent cytokine storm mediated by damage-associated molecular patterns (DAMPs) like HMGB1.

Human Regulatory T Cells Mediate Transcriptional Modulation of Dendritic Cell Function

Regulatory T cells (Treg) attenuate dendritic cell (DC) maturation and stimulatory function. Current knowledge on the functional impact of semimature DC is limited to CD4+ T cell proliferation and cytokine production. Little is known about the molecular basis underpinning the functional effects of Treg-treated DC (Treg-DC). We present novel evidence that Treg-DC skewed CD4+ naive T cell polarization toward a regulatory phenotype and impaired CD8+ T cell allo-reactive responses, including their ability to induce target tissue damage in a unique in vitro human graft-versus-host disease skin explant model. Microarray analysis clustered Treg-DC as a discrete population from mature-DC and immature-DC, with 51 and 93 genes that were significantly over- or underexpressed, respectively, compared with mature-DC. Quantitative real-time PCR analysis revealed an intermediate expression level of CD38, CD83, CD80 and CD86 mRNA in Treg-DC, lower than mature-DC, higher than immature-DC. We also observed an attenuation of NF-κB pathway, an upstream regulator of the aforementioned genes, concomitant with reduced expression of two NF-κB-signaling related genes RELB and NFκBIZ, in the Treg-DC, together with an increased expression of Wnt5a, a negative regulator of DC differentiation. We further confirmed that the Treg-DC-mediated skewed CD4+ naive T cell polarization resulted from decreased IL-12 secretion by Treg-DC, which may be post-transcriptionally modulated by decreased expression of microRNA-155 in Treg-DC. To our knowledge, this is the first study demonstrating a transcriptional modulation of DC function by human Treg, partially via attenuation of the NF-κB signaling pathway and upregulation of Wnt5a, suggesting Treg may interfere with DC reprogramming during maturation, thereby modulating DC function.

Dendritic Cell Reprogramming by Endogenously Produced Lactic Acid

The demand for controlling T cell responses via dendritic cell (DC) vaccines initiated a quest for reliable and feasible DC modulatory strategies that would facilitate cytotoxicity against tumors or tolerance in autoimmunity. We studied endogenous mechanisms in developing monocyte-derived DCs (MoDCs) that can induce inflammatory or suppressor programs during differentiation, and we identified a powerful autocrine pathway that, in a cell concentration-dependent manner, strongly interferes with inflammatory DC differentiation. MoDCs developing at low cell culture density have superior ability to produce inflammatory cytokines, to induce Th1 polarization, and to migrate toward the lymphoid tissue chemokine CCL19. On the contrary, MoDCs originated from dense cultures produce IL-10 but no inflammatory cytokines upon activation. DCs from high-density cultures maintained more differentiation plasticity and can develop to osteoclasts. The cell concentration-dependent pathway was independent of peroxisome proliferator-activated receptor γ (PPARγ), a known endogenous regulator of MoDC differentiation. Instead, it acted through lactic acid, which accumulated in dense cultures and induced an early and long-lasting reprogramming of MoDC differentiation. Our results suggest that the lactic acid-mediated inhibitory pathway could be efficiently manipulated in developing MoDCs to influence the immunogenicity of DC vaccines.

IRAK-M Expression Limits Dendritic Cell Activation and Proinflammatory Cytokine Production in Response to Helicobacter pylori

Helicobacter pylori (H. pylori) infects the gastric mucosa and persists for the life of the host. Bacterial persistence may be due to the induction of regulatory T cells (Tregs) whichmay have protective effects against other diseases such as asthma. It has been shown that H. pylori modulates the T cell response through dendritic cell reprogramming but the molecular pathways involved are relatively unknown. The goal of this study was to identify critical elements of dendritic cell (DC) activation and evaluate potential influence on immune activation. Microarray analysis was used to demonstrate limited gene expression changes in H. pylori stimulated bone marrow derived DCs (BMDCs) compared to the BMDCs stimulated with E. coli. IRAK-M, a negative regulator of TLR signaling, was upregulated and we selectedit for investigation of its role in modulating the DC and T cell responses. IRAK-M−/− and wild type BMDC were compared for their response to H. pylori. Cells lacking IRAK-M produced significantly greater amounts of proinflammatory MIP-2 and reduced amounts of immunomodulatory IL-10 than wild type BMDC. IRAK-M−/− cells also demonstrated increased MHC II expression upon activation. However, IRAK-M−/− BMDCs were comparable to wild type BMDCs in inducing T-helper 17 (TH17) and Treg responses as demonstrated in vitro using BMDC CD4+ T cells co-culture assays,and in vivo though the adoptive transfer of CD4+ FoxP3-GFP T cells into H. pylori infected IRAK-M−/− mice. These results suggest that H. pylori infection leads to the upregulation of anti-inflammatory molecules like IRAK-M and that IRAK-M has a direct impact on innate functions in DCs such as cytokine and costimulation molecule upregulation but may not affect T cell skewing.

Dendritic cell reprogramming by the hypoxic environment

Myeloid dendritic cells (DCs) are professional antigen-presenting cells central to the orchestration of innate and acquired immunity and the maintenance of self-tolerance. The local microenvironment contributes to the regulation of DC development and functions, and deregulated DC responses may result in amplification of inflammation, loss of tolerance, or establishment of immune escape mechanisms. DC generation from monocytic precursors recruited at sites of inflammation, tissue damage, or neoplasia occurs under condition of low partial oxygen pressure (pO2, hypoxia). We reviewed the literature addressing the phenotypic and functional changes triggered by hypoxia in monocyte-derived immature (i) and mature (m) DCs. The discussion will revolve around in vitro studies of gene expression profile, which give a comprehensive representation of the complexity of response of these cells to low pO2. The gene expression pattern of hypoxic DC will be discussed to address the question of the relationship with a specific maturation stage. We will summarize data relative to the regulation of the chemotactic network, which points to a role for hypoxia in promoting a migratory phenotype in iDCs and a highly proinflammatory state in mDCs. Current knowledge of the strict regulatory control exerted by hypoxia on the expression of immune-related cell surface receptors will also be addressed, with a particular focus on a newly identified marker of hypoxic DCs endowed with proinflammatory properties. Furthermore, we discuss the literature on the transcription mechanisms underlying hypoxia-regulated gene expression in DCs, which support a major role for the HIF/HRE pathway. Finally, recent advances shedding light on the in vivo influence of the local hypoxic microenvironment on DCs infiltrating the inflamed joints of juvenile idiopathic arthritis patients are outlined.

Lentiviral vectors for immunization: an inflammatory field

Lentiviruses are retroviruses that are able to transduce both dividing and nondividing cells. Dendritic cells are key players in the innate and adaptive immune responses, and are natural targets for lentiviruses. Lentiviral vectors (LVs) have recently reached the clinical gene therapy arena, prompting their use as clinical vaccines. In recent years, LVs have emerged as a robust and practical experimental platform for gene delivery and rational genetic reprogramming of dendritic cells. Here, we present the status quo of the LV system for protective or therapeutic vaccine development. This vector system has been extensively evaluated for ex vivo and in vivo (immuno)gene delivery. Improvements of the LV design in order to further grant a higher biosafety profile for vaccine development are presented.

CD4+ T Cells Have a Key Instructive Role in Educating Dendritic Cells in Allergy

Background: Dendritic cells (DCs) are central in allergy as regulators of the Th1/Th2 balance. We have recently demonstrated a unique transcriptional profile of DCs in patients with ongoing allergy compared with healthy subjects and shown that crosstalk between DCs and memory T cells affects the transcriptional profile of T cells. However, the transcriptional profile of DCs educated by T cells in allergy is unknown. Methods: In the present study, we have examined the transcriptional profiles of DCs after stimulation with grass pollen allergens, Phleum pratense and coculture with autologous CD4+ memory T cells using high-density microarray. Protein analysis was performed using flow cytometry and recombinant antibody protein microarrays. Patients with allergic rhinitis and healthy subjects were compared. Results: The results reveal a distinct T-cell-induced DC profile in atopic individuals. Accordingly, about 170 genes were upregulated and 40 genes downregulated. For example, the chemokine receptor CXCR4 and the tumor necrosis factor receptor CD30 were upregulated in DCs derived from atopic donors, and this could also be verified at the protein level. Conclusion: We conclude that crosstalk between CD4+ memory T cells and autologous DCs induces transcriptional reprogramming in DCs. This finding suggests that T cells have a key instructive role in educating DCs in Th2-type responses.