Cross talk between human regulatory T cells and antigen-presenting cells: Lessons for clinical applications

Short Report: CAR Tregs mediate linked suppression and infectious tolerance in islet transplantation

Regulatory T cells (Tregs) have potential as a cell-based therapy to prevent or treat transplant rejection and autoimmunity. Using an HLA-A2-specific chimeric antigen receptor (A2-CAR), we previously showed that adoptive transfer of A2-CAR Tregs limited anti-HLA-A2 alloimmunity. However, it was unknown if A2-CAR Tregs could also limit immunity to autoantigens. Using a model of HLA-A2+ islet transplantation into immunodeficient non-obese diabetic mice, we investigated if A2-CAR Tregs could control diabetes induced by islet-autoreactive (BDC2.5) T cells. In mice transplanted with HLA-A2+ islets, A2-CAR Tregs reduced BDC2.5 T cell engraftment, proliferation and cytokine production, and protected mice from diabetes. Tolerance to islets was systemic, including protection of the HLA-A2negative endogenous pancreas. In tolerant mice, a significant proportion of BDC2.5 T cells gained FOXP3 expression suggesting that long-term tolerance is maintained by de novo Treg generation. Thus, A2-CAR Tregs mediate linked suppression and infectious tolerance and have potential therapeutic use to simultaneously control both allo- and autoimmunity in islet transplantation.

Regulatory dendritic cell therapy in organ transplantation

PURPOSE OF REVIEW

Regulatory dendritic cells (DCregs; also 'tolerogenic DCs'), innate immune cells that regulate the alloimmune response, are a novel cellular therapy for organ transplantation. Preliminary results from early-phase clinical trials in live donor kidney and liver transplantation are promising. This follows many years of research elucidating mechanisms of action and utility of DCregs. Herein, we review early-phase clinical trial observations and recent advances in the production, modification, and future-trajectory of DCreg in organ transplantation.

RECENT FINDINGS

Preclinical work has demonstrated the ability of adoptively transferred DCreg to abrogate ischemia-reperfusion injury and promote long-term allograft survival. Good Manufacturing Practice-grade DCregs have been generated in adequate numbers for early-phase trials of autologous DCregs in kidney transplantation and donor-derived DCreg in liver transplantation. These trials have demonstrated feasibility and safety, with preliminary evidence of an influence on host immune reactivity. In both kidney and liver transplantation, reduced effector CD8 + T-cells have been noted, together with other changes that may be conducive to reduced dependence on immunosuppressive therapy.

SUMMARY

Substantial progress has been made in bringing DCreg to clinical testing in organ transplantation. Additional clinical and mechanistic studies are now needed to further explore and garner the full potential of DCreg in organ transplantation.

Obese visceral adipose dendritic cells downregulate regulatory T cell development through IL-33

Regulatory T cells (Tregs) residing in visceral adipose tissue (VAT) play a pivotal role in regulating tissue inflammation and metabolic dysfunction associated with obesity. However, the specific phenotypic and functional characteristics of Tregs in obese VAT, as well as the regulatory mechanisms shaping them, remain elusive. This study demonstrates that obesity selectively reduces Tregs in VAT, characterized by restrained proliferation, heightened PD-1 expression, and diminished ST2 expression. Additionally, obese VAT displays distinctive maturation of dendritic cells (DCs), marked by elevated expressions of MHC-II, CD86, and PD-L1, which are inversely correlated with VAT Tregs. In an in vitro co-culture experiment, only obese VAT DCs, not macrophages or DCs from subcutaneous adipose tissue (SAT) and spleen, result in decreased Treg differentiation and proliferation. Furthermore, Tregs differentiated by obese VAT DCs exhibit distinct characteristics resembling those of Tregs in obese VAT, such as reduced ST2 and IL-10 expression. Mechanistically, obesity lowers IL-33 production in VAT DCs, contributing to the diminished Treg differentiation. These findings collectively underscore the critical role of VAT DCs in modulating Treg generation and shaping Treg phenotype and function during obesity, potentially contributing to the regulation of VAT Treg populations.

Immune microenvironment heterogeneity reveals distinct subtypes in neuroblastoma: insights into prognosis and therapeutic targets

BACKGROUND

Neuroblastoma (NB) is a childhood cancer originating from immature nerve cells in the sympathetic nervous system. Current clinical and molecular subtyping methods for NB have limitations in providing accurate prognostic information and guiding treatment decisions.

RESULTS

To overcome these challenges, we explored the microenvironment of NB based on the knowledge-based functional gene expression signatures (Fges), which revealed heterogeneous subtypes. Consensus clustering of Fges activity scores identified three subtypes (Cluster 1, Cluster 2, and Cluster 3) that demonstrated significant differences in prognosis compared to mainstream subtypes. We assessed the immune infiltration, immunogenicity, CD8T cytotoxicity, and tumor purity of these subtypes, uncovering their distinct biological functions. Cluster 1 and Cluster 2 exhibited higher immunoreactivity, while Cluster 3 displayed higher tumor purity and poor prognosis. Gene ontology annotation and pathway analysis identified immune activation in Cluster 1, epithelial-mesenchymal transition (EMT) in Cluster 2, and cell cycle processes in Cluster 3. Notably, the impact of EMT activity on prognosis may vary across NB subtypes. A classification model using XGBoost accurately predicted subtypes in independent NB cohorts, with significant prognostic differences. GPR125, CDK4, and GREB1 emerged as potential therapeutic targets in Cluster 3. CD4K inhibitors showed subtype-specific responses, suggesting tailored treatment strategies. Single-cell analysis highlighted unfavorable clinical features in Cluster 3, including high-risk classification and reduced cytotoxicity. Suppressed interactions between monocytes, macrophages, and regulatory T cells were observed, affecting immune regulation and patient prognosis.

CONCLUSION

To summarize, we have identified a new independent prognostic factor in NB that underscores the significant correlation between tumor phenotype and immune contexture. These findings deepen our understanding of NB subtypes and immune cell interactions, paving the way for more effective treatment approaches.

Recombinant antigen 5 from Polybia paulista wasp venom (Hymenoptera, Vespidae): Antigen-specific antibody production and functional profile of CD4+ T cells in the immune response

Polybia paulista is a neotropical social wasp related to severe accidents and allergic reactions cases, including anaphylaxis, in southeastern Brazil. Antigen 5 (Poly p 5) is a major allergenic protein from its venom with potential use for component-resolved diagnostic. Therefore, the previous characterization of the immune response profile triggered by Poly p 5 should be evaluated. Recombinant Poly p 5 (rPoly p 5) was used to sensitize BALB/c mice with six weekly intradermal doses, and the specific antibody production and the functional profile of CD4+ T cells were assessed. rPoly p 5 induced the production of specific immunoglobulins (sIg) sIgE, sIgG1 and sIgG2a, which could recognize natural Poly p 5 presented in the venom of four different wasp species. rPoly p 5 stimulated in vitro the CD4+ T cells from immunized mice, which showed a significant proliferative response. These antigen-specific CD4+T cells produced IFN-γ and IL-17A cytokines and increased ROR-γT transcription factor expression. No differences between the control group and sensitized mice were found in IL-4 production and GATA-3 and T-bet expression. Interestingly, increased CD25+FoxP3+ regulatory T cells (Tregs) frequency was observed in the splenocyte cell cultures from rPoly p 5 immunized mice after the in vitro stimulation with both P. paulista venom extract and rPoly p 5. Here we showed that rPoly p 5 induces antigen-specific antibodies capable of recognizing Antigen 5 in the venom of four wasp species and modulates antigen-specific CD4+ T cells to IFN-γ production response associated with a Th17 profile in sensitized mice. These findings emphasize the potential use of rPoly p 5 as an essential source of a major wasp allergen with significant immunological properties.

CAR-T cells and CAR-Tregs targeting conventional type-1 dendritic cell suppress experimental autoimmune encephalomyelitis

Conventional type 1 dendritic cells (DC1) contribute to the development of pathogenic T helper type 1 (Th1) cells in part via the production of the proinflammatory cytokine interleukin-12. Thus, depletion of DC1 has the potential to dampen autoimmune responses. Here, we developed X-C motif chemokine receptor 1 (XCR1)-specific chimeric antigen receptor (CAR)-T cells and CAR-Tregs that specifically targeted DC1. XCR1 CAR-T cells were successfully generated as CD4+ and CD8+ T cells, expressed XCR1 CAR efficiently, and induced XCR1-dependent activation, cytokine production and proliferation. XCR1 CAR-T cells selectively depleted DC1 when transferred into RAG2-/- mice with a compensatory increase in conventional type 2 DC (DC2) and plasmacytoid DC (pDC). XCR1 CAR-T cell-mediated depletion of DC1 modestly suppressed the onset of Th1-driven experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Diphtheria toxin-mediated DC1 depletion in XCR1-diphtheria toxin receptor mice also suppressed EAE, suggesting that DC1 depletion was responsible for EAE suppression. XCR1 CAR-Tregs were successfully generated and suppressed effector T cells in the presence of XCR1+ cells. Therapeutic treatment with XCR1 CAR-Tregs suppressed Th1-driven EAE. Therefore, we conclude that depletion of DC1 with XCR1 CAR-T cells or immune suppression with XCR1 CAR-Tregs can modestly suppress Th1-driven EAE.

Lymphatic endothelial transcription factor Tbx1 promotes an immunosuppressive microenvironment to facilitate post-myocardial infarction repair

The heart is an autoimmune-prone organ. It is crucial for the heart to keep injury-induced autoimmunity in check to avoid autoimmune-mediated inflammatory disease. However, little is known about how injury-induced autoimmunity is constrained in hearts. Here, we reveal an unknown intramyocardial immunosuppressive program driven by Tbx1, a DiGeorge syndrome disease gene that encodes a T-box transcription factor (TF). We found induced profound lymphangiogenic and immunomodulatory gene expression changes in lymphatic endothelial cells (LECs) after myocardial infarction (MI). The activated LECs penetrated the infarcted area and functioned as intramyocardial immune hubs to increase the numbers of tolerogenic dendritic cells (tDCs) and regulatory T (Treg) cells through the chemokine Ccl21 and integrin Icam1, thereby inhibiting the expansion of autoreactive CD8+ T cells and promoting reparative macrophage expansion to facilitate post-MI repair. Mimicking its timing and implementation may be an additional approach to treating autoimmunity-mediated cardiac diseases.

Tregs integrate native and CAR-mediated costimulatory signals for control of allograft rejection

Tregs expressing chimeric antigen receptors (CAR-Tregs) are a promising tool to promote transplant tolerance. The relationship between CAR structure and Treg function was studied in xenogeneic, immunodeficient mice, revealing advantages of CD28-encoding CARs. However, these models could underrepresent interactions between CAR-Tregs, antigen-presenting cells (APCs), and donor-specific Abs. We generated Tregs expressing HLA-A2-specific CARs with different costimulatory domains and compared their function in vitro and in vivo using an immunocompetent model of transplantation. In vitro, the CD28-encoding CAR had superior antigen-specific suppression, proliferation, and cytokine production. In contrast, in vivo, Tregs expressing CARs encoding CD28, ICOS, programmed cell death 1, and GITR, but not 4-1BB or OX40, all extended skin allograft survival. To reconcile in vitro and in vivo data, we analyzed effects of a CAR encoding CD3ζ but no costimulatory domain. These data revealed that exogenous costimulation from APCs can compensate for the lack of a CAR-encoded CD28 domain. Thus, Tregs expressing a CAR with or without CD28 are functionally equivalent in vivo, mediating similar extension of skin allograft survival and controlling the generation of anti-HLA-A2 alloantibodies. This study reveals a dimension of CAR-Treg biology and has important implications for the design of CARs for clinical use in Tregs.

The Role of Regulatory T Cells in Cancer Treatment Resistance

Despite tremendous progress in cancer treatment in recent years, treatment resistance is still a major challenge for a great number of patients. One of the main causes is regulatory T lymphocytes (Tregs), which suppress excessive inflammatory responses via the secretion of immunosuppressive cytokines and upregulate the immune checkpoints. Their abundance causes an immunosuppressive reprogramming of the tumor environment, which is ideal for tumor growth and drug inefficiency. Hence, regiments that can regain tumor immunogenicity are a promising strategy to overcome Tregs-mediated drug resistance. However, to develop effective therapeutic regimens, it is essential to understand the molecular mechanisms of Treg-mediated resistance. In this article, we gathered a comprehensive summary of the current knowledge on molecular mechanisms and the role of Tregs in cancer treatment resistance, including cancer immunotherapy, targeted therapy, chemotherapy, and radiotherapy.

Biomarkers for Immune Checkpoint Inhibitors in Renal Cell Carcinoma

Immune checkpoint inhibitor (ICI) therapy has revolutionized renal cell carcinoma treatment. Patients previously thought to be palliative now occasionally achieve complete cures from ICI. However, since immunotherapies stimulate the immune system to induce anti-tumor immunity, they often lead to adverse autoimmunity. Furthermore, some patients receive no benefit from ICI, thereby unnecessarily risking adverse events. In many tumor types, PD-L1 expression levels, immune infiltration, and tumor mutation burden predict the response to ICI and help inform clinical decision making to better target ICI to patients most likely to experience benefits. Unfortunately, renal cell carcinoma is an outlier, as these biomarkers fail to discriminate between positive and negative responses to ICI therapy. Emerging biomarkers such as gene expression profiles and the loss of pro-angiogenic proteins VHL and PBRM-1 show promise for identifying renal cell carcinoma cases likely to respond to ICI. This review provides an overview of the mechanistic underpinnings of different biomarkers and describes the theoretical rationale for their use. We discuss the effectiveness of each biomarker in renal cell carcinoma and other cancer types, and we introduce novel biomarkers that have demonstrated some promise in clinical trials.

CD4 T-Cell Subsets and the Pathophysiology of Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is an umbrella term for the chronic immune-mediated idiopathic inflammation of the gastrointestinal tract, manifesting as Crohn's disease (CD) or ulcerative colitis (UC). IBD is characterized by exacerbated innate and adaptive immunity in the gut in association with microbiota dysbiosis and the disruption of the intestinal barrier, resulting in increased bacterial exposure. In response to signals from microorganisms and damaged tissue, innate immune cells produce inflammatory cytokines and factors that stimulate T and B cells of the adaptive immune system, and a prominent characteristic of IBD patients is the accumulation of inflammatory T-cells and their proinflammatory-associated cytokines in intestinal tissue. Upon antigen recognition and activation, CD4 T-cells differentiate towards a range of distinct phenotypes: T helper(h)1, Th2, Th9, Th17, Th22, T follicular helper (Tfh), and several types of T-regulatory cells (Treg). T-cells are generated according to and adapt to microenvironmental conditions and participate in a complex network of interactions among other immune cells that modulate the further progression of IBD. This review examines the role of the CD4 T-cells most relevant to IBD, highlighting how these cells adapt to the environment and interact with other cell populations to promote or inhibit the development of IBD.

The oxygen sensor Prolyl hydroxylase domain 2 regulates the in vivo suppressive capacity of regulatory T cells

The oxygen sensor prolyl hydroxylase domain 2 (PHD2) plays an important role in cell hypoxia adaptation by regulating the stability of HIF proteins (HIF1α and HIF2α) in numerous cell types, including T lymphocytes. The role of oxygen sensor on immune cells, particularly on regulatory T cell (Treg) function, has not been fully elucidated. The purpose of our study was to evaluate the role of PHD2 in the regulation of Treg phenotype and function. We demonstrate herein that selective ablation of PHD2 expression in Treg (PHD2^ΔTreg mice) leads to a spontaneous systemic inflammatory syndrome, as evidenced by weight loss, development of a rectal prolapse, splenomegaly, shortening of the colon, and elevated expression of IFN-γ in the mesenteric lymph nodes, intestine, and spleen. PHD2 deficiency in Tregs led to an increased number of activated CD4 conventional T cells expressing a Th1-like effector phenotype. Concomitantly, the expression of innate-type cytokines such as Il1b, Il12a, Il12b, and Tnfa was found to be elevated in peripheral (gut) tissues and spleen. PHD2^ΔTreg mice also displayed an enhanced sensitivity to dextran sodium sulfate-induced colitis and toxoplasmosis, suggesting that PHD2-deficient Tregs did not efficiently control inflammatory response in vivo, particularly those characterized by IFN-γ production. Further analysis revealed that Treg dysregulation was largely prevented in PHD2-HIF2α (PHD2-HIF2α^ΔTreg mice), but not in PHD2-HIF1α (PHD2-HIF1α^ΔTreg mice) double KOs, suggesting an important and possibly selective role of the PHD2-HIF2α axis in the control of Treg function. Finally, the transcriptomic analysis of PHD2-deficient Tregs identified the STAT1 pathway as a target of the PHD2-HIF2α axis in regulatory T cell phenotype and in vivo function.

Optimized CRISPR-mediated gene knockin reveals FOXP3-independent maintenance of human Treg identity

Regulatory T cell (Treg) therapy is a promising curative approach for a variety of immune-mediated conditions. CRISPR-based genome editing allows precise insertion of transgenes through homology-directed repair, but its use in human Tregs has been limited. We report an optimized protocol for CRISPR-mediated gene knockin in human Tregs with high-yield expansion. To establish a benchmark of human Treg dysfunction, we target the master transcription factor FOXP3 in naive and memory Tregs. Although FOXP3-ablated Tregs upregulate cytokine expression, effects on suppressive capacity in vitro manifest slowly and primarily in memory Tregs. Moreover, FOXP3-ablated Tregs retain their characteristic protein, transcriptional, and DNA methylation profile. Instead, FOXP3 maintains DNA methylation at regions enriched for AP-1 binding sites. Thus, although FOXP3 is important for human Treg development, it has a limited role in maintaining mature Treg identity. Optimized gene knockin with human Tregs will enable mechanistic studies and the development of tailored, next-generation Treg cell therapies.

Treg cell therapy: How cell heterogeneity can make the difference

CD4⁺ CD25^high CD127^low/- FOXP3⁺ T regulatory cells are responsible for maintaining immune tolerance and controlling excessive immune responses. Treg cell use in pre-clinical animal models showed the huge therapeutic potential of these cells in immune-mediated diseases and laid the foundations for their applications in therapy in humans. Currently, there are several clinical trials utilizing the adoptive transfer of Treg cells to reduce the morbidity in autoimmune disorders, allogeneic HSC transplantation, and solid organ transplantation. However, a large part of them utilizes total Treg cells without distinction of their biological variability. Many studies on the heterogeneity of Treg cell population revealed distinct subsets with different functions in the control of the immune response and induction of peripheral tolerance. Some of these subsets also showed a role in controlling the general homeostasis of non-lymphoid tissues. All these Treg cell subsets and their peculiar properties can be therefore exploited to develop novel therapeutic approaches. This review describes these functionally distinct subsets, their phenotype, homing properties and functions in lymphoid and non-lymphoid tissues. In addition, we also discuss the limitations in using Treg cells as a cellular therapy and the strategies to enhance their efficacy.