Coexpression of FOXP3 and a Helios isoform enhances the effectiveness of human engineered regulatory T cells

Regulatory T-cell dysfunctions are associated with increase in tumor necrosis factor α in autoimmune hemolytic anemia and participate in Th17 polarization

Warm autoimmune hemolytic anemia (wAIHA) is a rare acquired autoimmune disease mediated by antibodies targeting red blood cells. The involvement of CD4 T-helper cells has been scarcely explored, with most findings extrapolated from animal models. Here, we performed quantification of both effector T lymphocytes (Teff) and regulatory T cells (Treg), associated with functional and transcriptomic analyses of Treg in human wAIHA. We observed a shift of Teff toward a Th17 polarization concordant with an increase in serum interleukin-17 concentration that correlates with red blood cell destruction parameters, namely lactate dehydrogenase and bilirubin levels. A decrease in circulating Treg, notably effector Treg, associated with a functional deficiency, as represented by their decrease capability to inhibit Teff proliferation, were also observed. Treg deficiency was associated with a reduced expression of Foxp3, the master transcription factor known to maintain the Treg phenotype stability and suppressive functions. Transcriptomic profiling of Treg revealed activation of the tumor necrosis facto (TNF)-α pathway, which was linked to increased serum TNF-α concentrations that were twice as high as in controls. Treg transcriptomic profiling also suggested that post-translational mechanisms possibly accounted for Foxp3 downregulation and Treg dysfunctions. Since TNF-α participates in the rupture of immune tolerance during wAIHA, its inhibition could be of interest. To this end, the effects of fostamatinib, a SYK inhibitor, were investigated in vitro, and we showed that besides the inhibition of erythrocyte phagocytosis by monocytes, fostamatinib is also able to dampen TNF-α production, thus appearing as a promising multitargeting therapy in wAIHA (clinicaltrials gov. Identifier: NCT02158195).

HELIOS-expressing human CD8 T cells exhibit limited effector functions

Introduction

The transcription factor HELIOS is primarily known for its expression in CD4 regulatory T cells, both in humans and mice. In mice, HELIOS is found in exhausted CD8 T cells. However, information on human HELIOS+ CD8 T cells is limited and conflicting.

Methods

In this study, we characterized by flow cytometry and transcriptomic analyses human HELIOS+ CD8 T cells.

Results

These T cells primarily consist of memory cells and constitute approximately 21% of blood CD8 T cells. In comparison with memory HELIOS- T-BEThigh CD8 T cells that displayed robust effector functions, the memory HELIOS+ T-BEThigh CD8 T cells produce lower amounts of IFN-γ and TNF-α and have a lower cytotoxic potential. We wondered if these cells participate in the immune response against viral antigens, but did not find HELIOS+ cells among CD8 T cells recognizing CMV peptides presented by HLA-A2 and HLA-B7. However, we found HELIOS+ CD8 T cells that recognize a CMV peptide presented by MHC class Ib molecule HLA-E. Additionally, a portion of HELIOS+ CD8 T cells is characterized by the expression of CD161, often used as a surface marker for identifying TC17 cells. These CD8 T cells express TH17/TC17-related genes encoding RORgt, RORa, PLZF, and CCL20.

Discussion

Our findings emphasize that HELIOS is expressed across various CD8 T cell populations, highlighting its significance beyond its role as a transcription factor for Treg or exhausted murine CD8 T cells. The significance of the connection between HELIOS and HLA-E restriction is yet to be understood.

Promises and Pitfalls of Next-Generation Treg Adoptive Immunotherapy

Regulatory T cells (Tregs) are fundamental to maintaining immune homeostasis by inhibiting immune responses to self-antigens and preventing the excessive activation of the immune system. Their functions extend beyond immune surveillance and subpopulations of tissue-resident Treg cells can also facilitate tissue repair and homeostasis. The unique ability to regulate aberrant immune responses has generated the concept of harnessing Tregs as a new cellular immunotherapy approach for reshaping undesired immune reactions in autoimmune diseases and allo-responses in transplantation to ultimately re-establish tolerance. However, a number of issues limit the broad clinical applicability of Treg adoptive immunotherapy, including the lack of antigen specificity, heterogeneity within the Treg population, poor persistence, functional Treg impairment in disease states, and in vivo plasticity that results in the loss of suppressive function. Although the early-phase clinical trials of Treg cell therapy have shown the feasibility and tolerability of the approach in several conditions, its efficacy has remained questionable. Leveraging the smart tools and platforms that have been successfully developed for primary T cell engineering in cancer, the field has now shifted towards "next-generation" adoptive Treg immunotherapy, where genetically modified Treg products with improved characteristics are being generated, as regards antigen specificity, function, persistence, and immunogenicity. Here, we review the state of the art on Treg adoptive immunotherapy and progress beyond it, while critically evaluating the hurdles and opportunities towards the materialization of Tregs as a living drug therapy for various inflammation states and the broad clinical translation of Treg therapeutics.

Eras of designer Tregs: Harnessing synthetic biology for immune suppression

Since their discovery, CD4+ CD25hi FOXP3hi regulatory T cells (Tregs) have been firmly established as a critical cell type for regulating immune homeostasis through a plethora of mechanisms. Due to their immunoregulatory power, delivery of polyclonal Tregs has been explored as a therapy to dampen inflammation in the settings of transplantation and autoimmunity. Evidence shows that Treg therapy is safe and well-tolerated, but efficacy remains undefined and could be limited by poor persistence in vivo and lack of antigen specificity. With the advent of new genetic engineering tools, it is now possible to create bespoke "designer" Tregs that not only overcome possible limitations of polyclonal Tregs but also introduce new features. Here, we review the development of designer Tregs through the perspective of three 'eras': (1) the era of FOXP3 engineering, in which breakthroughs in the biological understanding of this transcription factor enabled the conversion of conventional T cells to Tregs; (2) the antigen-specificity era, in which transgenic T-cell receptors and chimeric antigen receptors were introduced to create more potent and directed Treg therapies; and (3) the current era, which is harnessing advanced genome-editing techniques to introduce and refine existing and new engineering approaches. The year 2022 marked the entry of "designer" Tregs into the clinic, with exciting potential for application and efficacy in a wide variety of immune-mediated diseases.

Unlocking the potential of Tregs: innovations in CAR technology

Regulatory T cells (Tregs) adoptive immunotherapy is emerging as a viable treatment option for both autoimmune and alloimmune diseases. However, numerous challenges remain, including limitations related to cell number, availability of target-specific cells, stability, purity, homing ability, and safety concerns. To address these challenges, cell engineering strategies have emerged as promising solutions. Indeed, it has become feasible to increase Treg numbers or enhance their stability through Foxp3 overexpression, post-translational modifications, or demethylation of the Treg-specific demethylated region (TSDR). Specificity can be engineered by the addition of chimeric antigen receptors (CARs), with new techniques designed to fine-tune specificity (tandem chimeric antigen receptors, universal chimeric antigen receptors, synNotch chimeric antigen receptors). The introduction of B-cell targeting antibody receptor (BAR) Tregs has paved the way for effective regulation of B cells and plasma cells. In addition, other constructs have emerged to enhance Tregs activation and function, such as optimized chimeric antigen receptors constructs and the use of armour proteins. Chimeric antigen receptor expression can also be better regulated to limit tonic signaling. Furthermore, various opportunities exist for enhancing the homing capabilities of CAR-Tregs to improve therapy outcomes. Many of these genetic modifications have already been explored for conventional CAR-T therapy but need to be further considered for CAR-Tregs therapies. This review highlights innovative CAR-engineering strategies that have the potential to precisely and efficiently manage immune responses in autoimmune diseases and improve transplant outcomes. As these strategies are further explored and optimized, CAR-Treg therapies may emerge as powerful tools for immune intervention.

A diet rich in fermentable fiber promotes robust changes in the intestinal microbiota, mitigates intestinal permeability, and attenuates autoimmune uveitis

Therapeutic approaches for noninfectious uveitis have expanded greatly over the past 10 years, but are limited by potential side effects and limited efficacy. Thus, therapeutic approaches that include less toxic, potentially preventative strategies to manage noninfectious uveitis are essential areas of study. Diets rich in fermentable fiber are potentially preventative in various conditions such as metabolic syndrome and type 1 diabetes. We studied the effects of various fermentable dietary fibers in an inducible model of experimental autoimmune uveitis (EAU) and found that they differentially modulated uveitis severity. A high pectin diet was the most protective, reducing clinical disease severity through the induction of regulatory T lymphocytes and the suppression of Th1 and Th17 lymphocytes at peak ocular inflammation in either intestinal or extra-intestinal lymphoid tissues. The high pectin diet also promoted intestinal homeostasis as shown by changes in intestinal morphology and gene expression, as well as intestinal permeability. Pectin-induced modulation of intestinal bacteria appeared to be associated with protective changes in immunophenotype in the intestinal tract, and correlated with reduced uveitis severity. In summary, our current findings support the potential for dietary intervention as a strategy to mitigate noninfectious uveitis severity.

Engineered Treg cells as putative therapeutics against inflammatory diseases and beyond

Regulatory T (Treg) cells ensure tolerance against self-antigens, limit excessive inflammation, and support tissue repair processes. Therefore, Treg cells are currently attractive candidates for the treatment of certain inflammatory diseases, autoimmune disorders, or transplant rejection. Early clinical trials have proved the safety and efficacy of certain Treg cell therapies in inflammatory diseases. We summarize recent advances in engineering Treg cells, including the concept of biosensors for inflammation. We assess Treg cell engineering possibilities for novel functional units, including Treg cell modifications influencing stability, migration, and tissue adaptation. Finally, we outline perspectives of engineered Treg cells going beyond inflammatory diseases by using custom-designed receptors and read-out systems, aiming to use Treg cells as in vivo diagnostic tools and drug delivery vehicles.

Regulatory T-cell therapy approaches

Regulatory T cells (Tregs) have enormous therapeutic potential to treat a variety of immunopathologies characterized by aberrant immune activation. Adoptive transfer of ex vivo expanded autologous Tregs continues to progress through mid- to late-phase clinical trials in several disease spaces and has generated promising preliminary safety and efficacy signals to date. However, the practicalities of this strategy outside of the clinical trial setting remain challenging. Here, we review the current landscape of regulatory T-cell therapy, considering emergent approaches and technologies presenting novel ways to engage Tregs, and reflect on the progress necessary to deliver their therapeutic potential to patients.

Dexmedetomidine alleviates acute lung injury by promoting Tregs differentiation via activation of AMPK/SIRT1 pathway

OBJECTIVES

To explore the anti-inflammatory effect and the potential mechanism of dexmedetomidine in ARDS/ALI.

MATERIALS AND METHODS

C57BL/6 mice and EL-4 cells were used in this research. The ALI model was established by CLP. The level of inflammatory cytokines in the lung and blood, the severity of lung injury, the expression of Foxp3, and the proportion of Tregs were detected before and after dexmedetomidine treatment. The expression of the AMPK/SIRT1 after dexmedetomidine treatment was detected in vivo and in vitro. After blocking the AMPK/SIRT1 pathway or depleting Tregs in vivo, the level of the inflammatory response, tissue injury, and Tregs differentiation were detected again to clarify the effect of dexmedetomidine.

RESULTS

Dexmedetomidine significantly reduced systemic inflammation and lung injury in CLP mice. Dexmedetomidine enhanced the Foxp3 expression in the lungs and the frequency of Tregs in the spleen. Dexmedetomidine up-regulated the protein expression of p-AMPK and SIRT1 in lungs and EL-4 cells and facilitated the differentiation of naïve CD4⁺ T cells into Tregs in vitro. Meanwhile, DEX also increased the expression of Helios in Treg cells.

CONCLUSIONS

DEX could improve ARDS/ALI by facilitating the differentiation of Tregs from naïve CD4⁺ T cells via activating the AMPK/SIRT1 pathway.

The small molecule inhibitor BX-795 uncouples IL-2 production from inhibition of Th2 inflammation and induces CD4+ T cells resembling iTreg

Background

Treg cells have been shown to be an important part of immune-homeostasis and IL-2 which is produced upon T cell receptor (TCR)-dependent activation of T lymphocytes has been demonstrated to critically participate in Treg development.

Objective

To evaluate small molecule inhibitors (SMI) for the identification of novel IL-2/Treg enhancing compounds.

Materials and methods

We used TCR-dependent and allergen-specific cytokine secretion of human and mouse T cells, next generation messenger ribonucleic acid sequencing (RNA-Seq) and two different models of allergic airway inflammation to examine lead SMI-compounds.

Results

We show here that the reported 3-phosphoinositide dependent kinase-1 (PDK1) SMI BX-795 increased IL-2 in culture supernatants of Jurkat E6-1 T cells, human peripheral blood mononuclear cells (hPBMC) and allergen-specific mouse T cells upon TCR-dependent and allergen-specific stimulation while concomitantly inhibiting Th2 cytokine secretion. RNA-Seq revealed that the presence of BX-795 during allergen-specific activation of T cells induces a bona fide Treg cell type highly similar to iTreg but lacking Foxp3 expression. When applied in mugwort pollen and house dust mite extract-based models of airway inflammation, BX-795 significantly inhibited Th2 inflammation including expression of Th2 signature transcription factors and cytokines and influx into the lungs of type 2-associated inflammatory cells such as eosinophils.

Conclusions

BX-795 potently uncouples IL-2 production from Th2 inflammation and induces Th-IL-2 cells, which highly resemble induced (i)Tregs. Thus, BX-795 may be a useful new compound for the treatment of allergic diseases.

Regulatory T cells in rheumatoid arthritis: functions, development, regulation, and therapeutic potential

Rheumatoid arthritis (RA) is an autoimmune disease that mainly affects the joints but also leads to systemic inflammation. Auto-reactivity and dysregulation of self-tolerance are thought to play a vital role in disease onset. In the pathogenesis of autoimmune diseases, disturbed immunosuppressive properties of regulatory T cells contribute to the dysregulation of immune homeostasis. In RA patients, the functions of Treg cells and their frequency are reduced. Therefore, focusing on the re-establishment of self-tolerance by increasing Treg cell frequencies and preventing a loss of function is a promising strategy for the treatment of RA. This approach could be especially beneficial for those patients who do not respond well to current therapies. In this review, we summarize and discuss the current knowledge about the function, differentiation and regulation of Treg cells in RA patients and in animal models of autoimmune arthritis. In addition, we highlight the therapeutic potential as well as the challenges of Treg cell targeting treatment strategies.

Single cell transcriptomic analysis of the immune cell compartment in the human small intestine and in Celiac disease

Celiac disease is an autoimmune disorder in which ingestion of dietary gluten triggers an immune reaction in the small intestine leading to destruction of the lining epithelium. Current treatment focusses on lifelong adherence to a gluten-free diet. Gluten-specific CD4⁺ T cells and cytotoxic intraepithelial CD8⁺ T cells have been proposed to be central in disease pathogenesis. Here we use unbiased single-cell RNA-sequencing and explore the heterogeneity of CD45⁺ immune cells in the human small intestine. We show altered myeloid cell transcriptomes present in active celiac lesions. CD4⁺ and CD8⁺ T cells transcriptomes show extensive changes and we define a natural intraepithelial lymphocyte population that is reduced in celiac disease. We show that the immune landscape in Celiac patients on a gluten-free diet is only partially restored compared to control samples. Altogether, we provide a single cell transcriptomic resource that can inform the immune landscape of the small intestine during Celiac disease.

Celiac disease is linked to responsiveness to dietary gluten, which manifests itself as immune cell activation and the immunopathology including destruction of the epithelium of the small intestine. Here the authors apply single cell transcriptomics to characterise the immune cell compartment of the human small intestine during active Celiac disease.

Emerging translational strategies and challenges for enhancing regulatory T cell therapy for graft-versus-host disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is a curative therapy for many types of cancer. Genetic disparities between donor and host can result in immune-mediated attack of host tissues, known as graft versus host disease (GVHD), a major cause of morbidity and mortality following HSCT. Regulatory CD4+ T cells (Tregs) are a rare cell type crucial for immune system homeostasis, limiting the activation and differentiation of effector T cells (Teff) that are self-reactive or stimulated by foreign antigen exposure. Adoptive cell therapy (ACT) with Treg has demonstrated, first in murine models and now in patients, that prophylactic Treg infusion can also suppress GVHD. While clinical trials have demonstrated Treg reduce severe GVHD occurrence, several impediments remain, including Treg variability and practical need for individualized Treg production for each patient. Additionally, there are challenges in the use of in vitro expansion techniques and in achieving in vivo Treg persistence in context of both immune suppressive drugs and in lymphoreplete patients being treated for GVHD. This review will focus on 3 main translational approaches taken to improve the efficacy of tTreg ACT in GVHD prophylaxis and development of treatment options, following HSCT: genetic modification, manipulating TCR and cytokine signaling, and Treg production protocols. In vitro expansion for Treg ACT presents a multitude of approaches for gene modification to improve efficacy, including: antigen specificity, tissue targeting, deletion of negative regulators/exhaustion markers, resistance to immunosuppressive drugs common in GVHD treatment. Such expansion is particularly important in patients without significant lymphopenia that can drive Treg expansion, enabling a favorable Treg:Teff ratio in vivo. Several potential therapeutics have also been identified that enhance tTreg stability or persistence/expansion following ACT that target specific pathways, including: DNA/histone methylation status, TCR/co-stimulation signaling, and IL-2/STAT5 signaling. Finally, this review will discuss improvements in Treg production related to tissue source, Treg subsets, therapeutic approaches to increase Treg suppression and stability during tTreg expansion, and potential for storing large numbers of Treg from a single production run to be used as an off-the-shelf infusion product capable of treating multiple recipients.

Antimetabolite Drugs Exhibit Distinctive Immunomodulatory Mechanisms and Effects on the Intestinal Microbiota in Experimental Autoimmune Uveitis

Purpose

The purpose of this study was to investigate the effect of antimetabolite drugs on T-cell responses and intestinal microbial composition in autoimmune uveitis.

Methods

Experimental autoimmune uveitis (EAU) was induced in C57BL/6J mice treated with 0.00625 mg/mL methotrexate (MTX) or 0.625 mg/mL mycophenolate mofetil (MMF) in drinking water for 4 weeks prior to immunization and 2 weeks thereafter. The effector T cell (Teff) and regulatory T cell (Treg) populations were identified using flow cytometry. The 16S rRNA gene sequencing was applied for gut microbiome characterization. DESeq2 analysis was used to discriminate relative abundances of taxa and PLS-DA to integrate cytometric and microbiome data between groups.

Results

Both MTX and MMF abrogated uveitis in EAU without clinical signs of toxicity as compared to water-fed controls. MTX reduced Teff and Treg expansion in peripheral tissues and eyes. MTX decreased alpha diversity, increased Akkermansia, and reduced Lachnoclostridium abundances. Conversely, MMF enhanced Tregs in the mesenteric lymph node and the eyes. In parallel, MMF increased the gut alpha diversity, including an increased abundance of Lachnospiraceae NK4A136 group and a decreased abundance of Lachnospiraceae UCG-001. A significant congruent correlation among intestinal microbial changes, T-cell responses, and clinical scores was observed for both antimetabolites.

Conclusions

Although MTX and MMF both abrogated uveitis in EAU, they showed different effects on T-cell subsets and the intestinal bacterial composition. This work indicates unique immunomodulation by each drug and is the first to demonstrate potential microbiota-related mechanisms.

Objetivo

Investigar el efecto de los fármacos antimetabolitos sobre las respuestas de células T y la composición microbiana intestinal en la uveítis autoinmune.

Métodos

Se indujo uveítis autoinmune experimental (UAE) en ratones C57BL/6J tratados con 0.00625 mg/ml de metotrexato (MTX) o 0.625 mg/ml de micofenolato mofetilo (MFM) en agua de bebida durante 4 semanas antes de la inmunización y 2 semanas después. Las poblaciones de células T efectoras (Tef) y reguladoras (Treg) se identificaron por citometría de flujo. La caracterización del microbioma intestinal se realizó mediante secuenciación del gen 16S ARNr. El análisis discriminante de abundancias relativas en los taxones se llevó a cabo por DESeq2 y se usó un análisis PLS-DA para integrar los datos microbianos y citométricos entre grupos.

Resultados

MTX y MFM inhibieron la UAE sin signos clínicos de toxicidad comparado con los controles. MTX disminuyó la expansión de Tef y Treg en los tejidos periféricos y oculares. MTX redujo la alfa diversidad, incrementando la abundancia de Akkermansia, y reduciendo la de Lachnoclostridium. En cambio, MFM aumentó los Tregs en el ganglio mesentérico y en los ojos. Paralelamente, MFM aumentó la alfa diversidad, incluyendo un aumento de la abundancia del grupo Lachnospiraceae NK4A136 y un descenso de la de Lachnospiraceae UCG-001. Se observó una correlación congruente significativa, para ambos fármacos, entre los cambios en el microbioma, las respuestas de células T y los grados clínicos de uveítis.

Conclusiones

Aunque ambos, MTX y MFM, suprimieron la UAE, mostraron efectos diferentes sobre los subtipos de células T y sobre la composición del microbioma. Este estudio indica un efecto inmunomodulador único para cada fármaco y es el primero en demostrar potenciales mecanismos relacionados con el microbioma.

Emerging strategies for treating autoimmune disorders with genetically modified Treg cells

Gene editing of living cells is a cornerstone of present-day medical research that has enabled scientists to address fundamental biologic questions and identify novel strategies to treat diseases. The ability to manipulate adoptive cell therapy products has revolutionized cancer immunotherapy and promises similar results for the treatment of autoimmune diseases, inflammatory disorders, and transplant rejection. Clinical trials have recently deemed polyclonal regulatory T (Treg) cell therapy to be a safe therapeutic option, but questions remain regarding the efficacy of this approach. In this review, we discuss how gene editing technologies are being applied to transform the future of Treg cell therapy, focusing on the preclinical strategies that are currently being investigated to enhance the efficacy, function, and survival of human Treg cells. We explore approaches that may be used to generate immunoregulatory cells ex vivo, detail emerging strategies that are being used to modify these cells (such as using chimeric antigen receptors to confer antigen specificity), and outline concepts that have been explored to repurpose conventional T cells to target and destroy autoreactive and alloreactive lymphocytes. We also describe the key hurdles that currently hinder the clinical adoption of Treg cell therapy and propose potential future avenues of research for this field.

Newly Found Peacekeeper: Potential of CD8+ Tregs for Graft-Versus-Host Disease

Allogeneic hematopoietic stem cell transplantation (allo-HSCT) remains the most effective and potentially curative treatment for a variety of hematologic malignancies. However, graft-versus-host disease (GVHD) is a major obstacle that limits wide application of allo-HSCT, despite the development of prophylactic strategies. Owing to experimental and clinical advances in the field, GVHD is characterized by disruption of the balance between effector and regulatory immune cells, resulting in higher inflammatory cytokine levels. A reduction in regulatory T cells (Tregs) has been associated with limiting recalibration of inflammatory overaction and maintaining immune tolerance. Moreover, accumulating evidence suggests that immunoregulation may be useful for preventing GVHD. As opposed to CD4⁺ Tregs, the CD8⁺ Tregs population, which constitutes an important proportion of all Tregs, efficiently attenuates GVHD while sparing graft-versus-leukemic (GVL) effects. CD8⁺ Tregs may provide another form of cellular therapy for preventing GVHD and preserving GVL effects, and understanding the underlying mechanisms that different from those of CD4⁺ Tregs is significant. In this review, we summarize preclinical experiments that have demonstrated the role of CD8⁺ Tregs during GVHD and attempted to obtain optimized CD8⁺ Tregs. Notably, although optimized CD8⁺ Tregs have obvious advantages, more exploration is needed to determine how to apply them in the clinic.

Co-Expression of FOXP3FL and FOXP3Δ2 Isoforms Is Required for Optimal Treg-Like Cell Phenotypes and Suppressive Function

FOXP3 is the master transcription factor in both murine and human FOXP3⁺ regulatory T cells (Tregs), a T-cell subset with a central role in controlling immune responses. Loss of the functional Foxp3 protein in scurfy mice leads to acute early-onset lethal lymphoproliferation. Similarly, pathogenic FOXP3 mutations in humans lead to immunodysregulation, polyendocrinopathy, enteropathy, and X-linked (IPEX) syndrome, which are characterized by systemic autoimmunity that typically begins in the first year of life. However, although pathogenic FOXP3 mutations lead to overlapping phenotypic consequences in both systems, FOXP3 in human Tregs, but not mouse, is expressed as two predominant isoforms, the full length (FOXP3FL) and the alternatively spliced isoform, delta 2 (FOXP3Δ2). Here, using CRISPR/Cas9 to generate FOXP3 knockout CD4⁺ T cells (FOXP3KO^GFP CD4+ T cells), we restore the expression of each isoform by lentiviral gene transfer to delineate their functional roles in human Tregs. When compared to FOXP3FL or FOXP3Δ2 alone, or double transduction of the same isoform, co-expression of FOXP3FL and FOXP3Δ2 induced the highest overall FOXP3 protein expression in FOXP3KO^GFP CD4+ T cells. This condition, in turn, led to optimal acquisition of Treg-like cell phenotypes including downregulation of cytokines, such as IL-17, and increased suppressive function. Our data confirm that co-expression of FOXP3FL and FOXP3Δ2 leads to optimal Treg-like cell function and supports the need to maintain the expression of both when engineering therapeutics designed to restore FOXP3 function in otherwise deficient cells.

IRF4 is Correlated with the Conversion to a Th17-Like Phenotype in Regulatory T Cells from the Malignant Pleural Effusion

Background

RORγt⁺Foxp3⁺ (Th17-like) Tregs are a plastic Treg subset implicated in immune-related diseases; however, the mechanism of Treg phenotypic transformation in malignant pleural effusion (MPE) has not been elucidated.

Methods

The percentage of CD4⁺CD25⁺Foxp3⁺Helios⁺ and RORγt⁺Foxp3⁺ Tregs from peripheral blood and pleural effusion mononuclear cells were measured. The level of interferon regulatory factor 4 (IRF4) mRNA expression was detected by quantitative real-time reverse transcription polymerase chain reaction. The effects of IRF4 on the induction of Tregs from patients with non-small cell lung cancer (NSCLC) were evaluated in vitro. Correlation assays between IRF4 expression and the frequency of RORγt⁺Foxp3⁺ Tregs were performed.

Results

The frequency of CD4⁺CD25⁺Foxp3⁺Helios⁺ Tregs and CD4⁺RORγt⁺ Th17 cells was both increased in the MPE of NSCLC patients. The group of double-positive Foxp3⁺RORγt⁺ Treg phenotype were identified in the pleural effusion. A significant increase in the frequency of Foxp3⁺RORγt⁺ Tregs was found in MPE compared with the non-malignant pleural effusion (NPE). Compared to NPE, the relative level of IRF4 expression was increased in the MPE. IRF4 expression was positively associated with the frequency of Foxp3⁺RORγt⁺ Tregs in the PE. In vitro, the level of Helios mRNA and protein expression was reduced in induced Tregs following IRF4 over-expression. Additionally, the level of RORγt protein expression was substantially increased. However, ectopic Helios expression in induced Tregs reversed the effects induced by enhanced IRF4 expression.

Conclusion

IRF4 may serve as a potential molecule that promotes the conversion of regulatory T cells from MPE to a Th17-like phenotype by modulating Helios.

Improving the Efficacy of Regulatory T Cell Therapy

Autoimmunity is caused by an unbalanced immune system, giving rise to a variety of organ-specific to system disorders. Patients with autoimmune diseases are commonly treated with broad-acting immunomodulatory drugs, with the risk of severe side effects. Regulatory T cells (Tregs) have the inherent capacity to induce peripheral tolerance as well as tissue regeneration and are therefore a prime candidate to use as cell therapy in patients with autoimmune disorders. (Pre)clinical studies using Treg therapy have already established safety and feasibility, and some show clinical benefits. However, Tregs are known to be functionally impaired in autoimmune diseases. Therefore, ex vivo manipulation to boost and stably maintain their suppressive function is necessary when considering autologous transplantation. Similar to autoimmunity, severe coronavirus disease 2019 (COVID-19) is characterized by an exaggerated immune reaction and altered Treg responses. In light of this, Treg-based therapies are currently under investigation to treat severe COVID-19. This review provides a detailed overview of the current progress and clinical challenges of Treg therapy for autoimmune and hyperinflammatory diseases, with a focus on recent successes of ex vivo Treg manipulation.

Super-Treg: Toward a New Era of Adoptive Treg Therapy Enabled by Genetic Modifications

Regulatory Tcells (Treg) are essential components of peripheral immune homeostasis. Adoptive Treg cell therapy has shown efficacy in a variety of immune-mediated diseases in preclinical studies and is now moving from phase I/IIa to larger phase II studies aiming to demonstrate efficacy. However, hurdles such as in vivo stability and efficacy remain to be addressed. Nevertheless, preclinical models have shown that Treg function and specificity can be increased by pharmacological substances or gene modifications, and even that conventional T cells can be converted to Treg potentially providing new sources of Treg and facilitating Treg cell therapy. The exponential growth in genetic engineering techniques and their application to T cells coupled to a large body of knowledge on Treg open numerous opportunities to generate Treg with "superpowers". This review summarizes the genetic engineering techniques available and their applications for the next-generation of Super-Treg with increased function, stability, redirected specificity and survival.

Detection and Monitoring of Regulatory Immune Cells Following Their Adoptive Transfer in Organ Transplantation

Application of cell-based immunotherapy in organ transplantation to minimize the burden of immunosuppressive medication and promote allograft tolerance has expanded significantly over the past decade. Adoptively transferred regulatory immune cells prolong allograft survival and transplant tolerance in pre-clinical models. Many cell products are currently under investigation in early phase human clinical trials designed to assess feasibility and safety. Despite rapid advances in manufacturing practices, defining the appropriate protocol that will optimize in vivo conditions for tolerance induction remains a major challenge and depends heavily on understanding the fate, biodistribution, functional stability and longevity of the cell product after administration. This review focuses on in vivo detection and monitoring of various regulatory immune cell types administered for allograft tolerance induction in both pre-clinical animal models and early human clinical trials. We discuss the current status of various non-invasive methods for tracking regulatory cell products in the context of organ transplantation and implications for enhanced understanding of the therapeutic potential of cell-based therapy in the broad context of control of immune-mediated inflammatory disorders.