Generation of Powerful Human Tolerogenic Dendritic Cells by Lentiviral-Mediated IL-10 Gene Transfer

GENERATION OF TOLEROGENIC DENDRITIC CELLS UNDER THE PERSISTENT INFLAMMATION STIMULATION

ABSTRACT

Immunosuppression, commonly accompanied by persistent inflammation, is a key feature in the later phase of sepsis. However, the pathophysiological mechanisms underlying this phenomenon remain unclear. Dendritic cells (DCs), specifically tolerogenic DCs (tolDCs), play a crucial role in this process by regulating immune responses through inducing T cell anergy and releasing anti-inflammatory cytokines. Nevertheless, the existing cell models are inadequate for investigating tolDCs during the immunosuppressive phase of sepsis. Therefore, this study aimed to develop a novel in vitro model to generate tolDCs under chronic inflammatory conditions. We have successfully generated tolDCs by exposing them to sublethal lipopolysaccharide (LPS) for 72 h while preserving cell viability. Considering that IL-10-induced tolDCs (IL-10-tolDCs) are well-established models, we compared the immunological tolerance between LPS-tolDCs and IL-10-tolDCs. Our findings indicated that both LPS-tolDCs and IL-10-tolDCs exhibited reduced expression of maturation markers, whereas their levels of inhibitory markers were elevated. Furthermore, the immunoregulatory activities of LPS-tolDCs and IL-10-tolDCs were found to be comparable. These dysfunctions include impaired antigen presenting capacity and suppression of T cell activation, proliferation, and differentiation. Notably, compared with IL-10-tolDCs, LPS-tolDCs showed a reduced response in maturation and cytokine production upon stimulation, indicating their potential as a better model for research. Overall, in comparison with IL-10-tolDCs, our data suggest that the immunological dysfunctions shown in LPS-tolDCs could more effectively elucidate the increased susceptibility to secondary infections during sepsis. Consequently, LPS-tolDCs have emerged as promising therapeutic targets for ameliorating the immunosuppressed state in septic patients.

5-HT modulates the properties of dendritic cells to interfere with the development of type 1 regulating T cells

BACKGROUND

5-hydroxytryptamine (5-HT, serotonin) is a major mediator in allergic reactions. The number of tolerogenic dendritic cell (tolDC) and regulatory T cell is reduced in allergic disorders. The mechanism is unclear. The objective of this study is to elucidate the role of 5-HT in interfering with tolDC generation and regulatory Type 1 T cell (Tr1 cell).

METHODS

BALB/c mice were treated with 5-HT-containing nasal instillations. The frequency of tolDC and Tr1 cell was evaluated by flow cytometry.

RESULTS

Following treatment with 5-HT nasal instillations for one week, the frequency of tolDC and Tr1 cell was significantly reduced in the respiratory tissues. Higher levels of SOS1 were detected in DCs isolated from the airway tissues of mice treated with 5-HT. A complex of SOS1 and c-Maf was detected in DCs in response to 5-HT stimulation. The expression of IL-10 was suppressed by the presence of 5-HT. The induction of Tr1 cell by DC was substantially compromised by 5-HT.

CONCLUSIONS

5-HT inhibits the expression of IL-10 in DCs. DCs primed with 5-HT lose the ability to induce Tr1 cells.

Constitutive IL-1RA production by modified immune cells protects against IL-1-mediated inflammatory disorders

Dysregulation of the interleukin-1 (IL-1) pathway leads to immune diseases that can result in chronic tissue and organ inflammation. Although IL-1 blockade has shown promise in ameliorating these symptoms and improving patients' quality of life, there is an urgent need for more effective, long-lasting treatments. We developed a lentivirus (LV)-mediated gene transfer strategy using transplanted autologous hematopoietic stem/progenitor cells (HSPCs) as a source of IL-1 receptor antagonist (IL-1RA) for systemic delivery to tissues and organs. Transplantation of mouse and human HSPCs transduced with an IL-1RA-encoding LV ensured stable IL-1RA production while maintaining the clonogenic and differentiation capacities of HSPCs in vivo. We examined the efficacy of cell-mediated IL-1RA delivery in three models of IL-1-dependent inflammation, for which treatment hindered neutrophil recruitment in an inducible model of gout, prevented systemic and multi-tissue inflammation in a genetic model of cryopyrin-associated periodic syndromes, and reduced disease severity in an experimental autoimmune encephalomyelitis model of multiple sclerosis. Our findings demonstrate HSPC-mediated IL-1RA delivery as a potential therapeutic modality that can be exploited to suppress tissue and organ inflammation in diverse immune-related diseases involving IL-1-driven inflammation.

IL-10-Engineered Dendritic Cells Modulate Allogeneic CD8+ T Cell Responses

Tolerogenic dendritic cells (tolDC) play a central role in regulating immune homeostasis and in promoting peripheral tolerance. These features render tolDC a promising tool for cell-based approaches aimed at inducing tolerance in T-cell mediated diseases and in allogeneic transplantation. We developed a protocol to generate genetically engineered human tolDC overexpressing IL-10 (DC^IL-10) by means of a bidirectional lentiviral vector (LV) encoding for IL-10. DC^IL-10 promote allo-specific T regulatory type 1 (Tr1) cells, modulate allogeneic CD4⁺ T cell responses in vitro and in vivo, and are stable in a pro-inflammatory milieu. In the present study, we investigated the ability of DC^IL-10 to modulate cytotoxic CD8⁺ T cell responses. We demonstrate that DC^IL-10 reduces allogeneic CD8⁺ T cell proliferation and activation in primary mixed lymphocyte reactions (MLR). Moreover, long-term stimulation with DC^IL-10 induces allo-specific anergic CD8⁺ T cells without signs of exhaustion. DC^IL-10-primed CD8⁺ T cells display limited cytotoxic activity. These findings indicate that stable over-expression of IL-10 in human DC leads to a population of cells able to modulate cytotoxic allogeneic CD8⁺ T cell responses, overall indicating that DC^IL-10 represent a promising cellular product for clinical applications aimed at inducing tolerance after transplantation.

Tolerogenic IL-10-engineered dendritic cell-based therapy to restore antigen-specific tolerance in T cell mediated diseases

Tolerogenic dendritic cells play a critical role in promoting antigen-specific tolerance via dampening of T cell responses, induction of pathogenic T cell exhaustion and antigen-specific regulatory T cells. Here we efficiently generate tolerogenic dendritic cells by genetic engineering of monocytes with lentiviral vectors co-encoding for immunodominant antigen-derived peptides and IL-10. These transduced dendritic cells (designated DC^IL-10/Ag) secrete IL-10 and efficiently downregulate antigen-specific CD4⁺ and CD8⁺ T cell responses from healthy subjects and celiac disease patients in vitro. In addition, DC^IL-10/Ag induce antigen-specific CD49b⁺LAG-3⁺ T cells, which display the T regulatory type 1 (Tr1) cell gene signature. Administration of DC^IL-10/Ag resulted in the induction of antigen-specific Tr1 cells in chimeric transplanted mice and the prevention of type 1 diabetes in pre-clinical disease models. Subsequent transfer of these antigen-specific T cells completely prevented type 1 diabetes development. Collectively these data indicate that DC^IL-10/Ag represent a platform to induce stable antigen-specific tolerance to control T-cell mediated diseases.

24th "Nantes Actualités en Transplantation" and 4th "LabEx Immunotherapy-Graft-Oncology" NAT and IGO Joint Meeting "New Horizons in Immunotherapy"

The 24th edition of the annual NAT conference (Nantes Actualités Transplantation) and the 4th edition of the biennial LabEx IGO meeting (Immunotherapy Graft Oncology) were held jointly around a common theme: "New horizons in immunotherapy", on May 31st and June 1st 2021 to highlight new findings in the fields of transplantation, autoimmunity and cancer.

Tolerogenic Dendritic Cell-Based Approaches in Autoimmunity

Dendritic cells (DCs) dictate the outcomes of tissue-specific immune responses. In the context of autoimmune diseases, DCs instruct T cells to respond to antigens (Ags), including self-Ags, leading to organ damage, or to becoming regulatory T cells (Tregs) promoting and perpetuating immune tolerance. DCs can acquire tolerogenic properties in vitro and in vivo in response to several stimuli, a feature that opens the possibility to generate or to target DCs to restore tolerance in autoimmune settings. We present an overview of the different subsets of human DCs and of the regulatory mechanisms associated with tolerogenic (tol)DC functions. We review the role of DCs in the induction of tissue-specific autoimmunity and the current approaches exploiting tolDC-based therapies or targeting DCs in vivo for the treatment of autoimmune diseases. Finally, we discuss limitations and propose future investigations for improving the knowledge on tolDCs for future clinical assessment to revert and prevent autoimmunity. The continuous expansion of tolDC research areas will lead to improving the understanding of the role that DCs play in the development and treatment of autoimmunity.

Regulatory Macrophages and Tolerogenic Dendritic Cells in Myeloid Regulatory Cell-Based Therapies

Myeloid regulatory cell-based therapy has been shown to be a promising cell-based medicinal approach in organ transplantation and for the treatment of autoimmune diseases, such as type 1 diabetes, rheumatoid arthritis, Crohn’s disease and multiple sclerosis. Dendritic cells (DCs) are the most efficient antigen-presenting cells and can naturally acquire tolerogenic properties through a variety of differentiation signals and stimuli. Several subtypes of DCs have been generated using additional agents, including vitamin D3, rapamycin and dexamethasone, or immunosuppressive cytokines, such as interleukin-10 (IL-10) and transforming growth factor-beta (TGF-β). These cells have been extensively studied in animals and humans to develop clinical-grade tolerogenic (tol)DCs. Regulatory macrophages (Mregs) are another type of protective myeloid cell that provide a tolerogenic environment, and have mainly been studied within the context of research on organ transplantation. This review aims to thoroughly describe the ex vivo generation of tolDCs and Mregs, their mechanism of action, as well as their therapeutic application and assessment in human clinical trials.

Rapamycin Alternatively Modifies Mitochondrial Dynamics in Dendritic Cells to Reduce Kidney Ischemic Reperfusion Injury

Dendritic cells (DCs) are unique immune cells that can link innate and adaptive immune responses and Immunometabolism greatly impacts their phenotype. Rapamycin is a macrolide compound that has immunosuppressant functions and is used to prevent graft loss in kidney transplantation. The current study evaluated the therapeutic potential of ex-vivo rapamycin treated DCs to protect kidneys in a mouse model of acute kidney injury (AKI). For the rapamycin single (S) treatment (Rapa-S-DC), Veh-DCs were treated with rapamycin (10 ng/mL) for 1 h before LPS. In contrast, rapamycin multiple (M) treatment (Rapa-M-DC) were exposed to 3 treatments over 7 days. Only multiple ex-vivo rapamycin treatments of DCs induced a persistent reprogramming of mitochondrial metabolism. These DCs had 18-fold more mitochondria, had almost 4-fold higher oxygen consumption rates, and produced more ATP compared to Veh-DCs (Veh treated control DCs). Pathway analysis showed IL10 signaling as a major contributing pathway to the altered immunophenotype after Rapamycin treatment compared to vehicle with significantly lower cytokines Tnfa, Il1b, and Il6, while regulators of mitochondrial content Pgc1a, Tfam, and Ho1 remained elevated. Critically, adoptive transfer of rapamycin-treated DCs to WT recipients 24 h before bilateral kidney ischemia significantly protected the kidneys from injury with a significant 3-fold improvement in kidney function. Last, the infusion of DCs containing higher mitochondria numbers (treated ex-vivo with healthy isolated mitochondria (10 µg/mL) one day before) also partially protected the kidneys from IRI. These studies demonstrate that pre-emptive infusion of ex-vivo reprogrammed DCs that have higher mitochondria content has therapeutic capacity to induce an anti-inflammatory regulatory phenotype to protect kidneys from injury.

Regulatory Dendritic Cells, T Cell Tolerance, and Dendritic Cell Therapy for Immunologic Disease

Dendritic cells (DC) are antigen-presenting cells that can communicate with T cells both directly and indirectly, regulating our adaptive immune responses against environmental and self-antigens. Under some microenvironmental conditions DC develop into anti-inflammatory cells which can induce immunologic tolerance. A substantial body of literature has confirmed that in such settings regulatory DC (DCreg) induce T cell tolerance by suppression of effector T cells as well as by induction of regulatory T cells (Treg). Many in vitro studies have been undertaken with human DCreg which, as a surrogate marker of antigen-specific tolerogenic potential, only poorly activate allogeneic T cell responses. Fewer studies have addressed the abilities of, or mechanisms by which these human DCreg suppress autologous effector T cell responses and induce infectious tolerance-promoting Treg responses. Moreover, the agents and properties that render DC as tolerogenic are many and varied, as are the cells’ relative regulatory activities and mechanisms of action. Herein we review the most current human and, where gaps exist, murine DCreg literature that addresses the cellular and molecular biology of these cells. We also address the clinical relevance of human DCreg, highlighting the outcomes of pre-clinical mouse and non-human primate studies and early phase clinical trials that have been undertaken, as well as the impact of innate immune receptors and symbiotic microbial signaling on the immunobiology of DCreg.

Regulatory Cell Therapy in Organ Transplantation: Achievements and Open Questions

The effective development of innovative surgical applications and immunosuppressive agents have improved remarkable advancements in solid organ transplantation. Despite these improvements led to prevent acute rejection and to promote short-term graft survival, the toxicity of long-term immunosuppression regiments has been associated to organ failure or chronic graft rejection. The graft acceptance is determined by the balance between the regulatory and the alloreactive arm of the immune system. Hence, enhance regulatory cells leading to immune tolerance would be the solution to improve long-term allograft survival which, by reducing the overall immunosuppression, will provide transplanted patients with a better quality of life. Regulatory T cells (Tregs), and regulatory myeloid cells (MRCs), including regulatory macrophages and tolerogenic dendritic cells, are promising cell populations for restoring tolerance. Thus, in the last decade efforts have been dedicated to apply regulatory cell-based therapy to improve the successful rate of organ transplantation and to promote allogeneic tolerance. More recently, this approach has been translated into clinical application. The aim of this review is to summarize and discuss results on regulatory cell-based strategies, focusing on Tregs and MRCs, in terms of safety, feasibility, and efficacy in clinical studies of organ transplantation.