Regulatory CAR-T cells in autoimmune diseases: Progress and current challenges

Treg Cells Attenuate Pulmonary Venous Remodeling in PH-LHD via NLRC3 Signaling

BACKGROUND

Pulmonary venous remodeling is a key pathological feature of pulmonary hypertension associated with left heart disease (PH-LHD). This study aims to investigate the role of regulatory T (Treg) cells in this process.

METHODS

We used mouse models with transverse aortic constriction and cell depletion of Foxp3-DTR/tdTomato mice to examine Treg cells' function around pulmonary veins in PH-LHD in vivo. To confirm the effect of Nlrc3-/- Treg cells on PH-LHD, we utilized 3 mouse models: Nlrc3 knockout mice, athymic mice, and endothelial cell lineage tracing Cdh5CreERT2+/--mT/mG+/- mice. The interaction proteins and signaling pathways of Treg cells during endothelial-to-mesenchymal transition were elucidated by protein docking prediction, coimmunoprecipitation and cocultivation of Treg cells with venous endothelial cells.

RESULTS

Treg cells were abundant around pulmonary veins of transverse aortic constriction-induced PH-LHD and were essential for promoting inflammation resolution and inhibiting pulmonary venous remodeling. Nlrc3 expression was reduced in mice and patients with PH-LHD. NLRC3 (nucleotide-oligomerization domain-like receptor family CARD domain containing 3) deficiency inhibited Treg cell proliferation and impaired their immunosuppressive and endothelial-to-mesenchymal transition-protective effects. Mechanistically, NLRC3 interacted with TRAM (TRIF-related adaptor molecule) and regulated interferon regulatory factor 3 (IRF3)/NF-κB (nuclear factor-κB) p65 signaling in cluster differentiation 4+ (CD4+) T cells. NLRC3-deficient Treg cells promoted interleukin (IL)-18 expression through IRF3/NF-κB p65 signaling, and thus IL-18 secretion activated endothelial receptor tyrosine kinase (RTK) signaling, favoring endothelial-to-mesenchymal transition progression in pulmonary veins and PH-LHD progress. This process was reversible with IL-18 binding protein in vivo.

CONCLUSIONS

NLRC3 is crucial for Treg cells to prevent pulmonary venous remodeling in PH-LHD, primarily by modulating IL-18 secretion, which inhibits endothelial-to-mesenchymal transition and thereby improves disease progression and prognosis.

Epigenetically Reprogrammed Nanovesicles as Inverse Vaccines for Antigen-Specific Immune Tolerance in Autoimmune Diseases

The development of antigen-specific immunotherapy for autoimmune diseases constitutes an important unmet clinical need. Here we present an innovative inverse vaccine platform leveraging epigenetic reprogramming to induce durable antigen-specific immune tolerance. This inverse vaccine (mDCNVreg) is constructed using artificial cell membrane nanovesicles derived from IFN-γ-primed regulatory dendritic cells subjected to epigenetic modulation. The engineered mDCNVreg features upregulated MHC-II expression enabling targeted antigen presentation, suppressed costimulatory molecules expression, and an enhanced coinhibitory molecules display. Through coordinated mechanisms involving enhanced lymphoid trafficking and phenotype stabilization, this platform significantly enhances antigen delivery to secondary lymphoid organs while maintaining tolerogenic potency. Crucially, mDCNVreg directly induces CD4+ T cell clonal anergy through epitope-specific interactions, establishing long-lasting immune tolerance. This work demonstrates a promising epigenetic engineering approach for reverse vaccine design in personalized autoimmune disease therapy.

T-regulatory cells for the treatment of autoimmune diseases

Autoimmune diseases result from imbalances in the immune system and disturbances in the mechanisms of immune tolerance. T-regulatory cells (Treg) are key factors in the formation of immune tolerance. Tregs modulate immune responses and repair processes, controlling the innate and adaptive immune system. The use of Tregs in the treatment of autoimmune diseases began with the manipulation of endogenous Tregs using immunomodulatory drugs. Then, a method of adoptive transfer of Tregs grown in vitro was developed. Adoptive transfer of Tregs includes polyclonal Tregs with non-specific effects and antigen-specific Tregs in the form of CAR-Treg and TCR-Treg. This review discusses non-specific and antigen-specific approaches to the use of Tregs, their advantages, disadvantages, gaps in development, and future prospects.

Expanding the Horizons of CAR-T Cell Therapy: A Review of Therapeutic Targets Across Diverse Diseases

CAR-T cell therapy has shown promising results in treating malignant hematologic diseases. The principle of this therapy is based on the use of genetically modified T lymphocytes to express a Chimeric Antigen Receptor (CAR) on their membrane that specifically recognizes an antigen predominantly expressed on target cells. The molecular design of the CAR, along with advancements in molecular techniques and the development of "omics", has opened the possibility of discovering new therapeutic targets and thereby expanding the range of diseases treated with CAR-T cells beyond the use of anti-CD19 and anti-BCMA for hematologic cancer. This review summarizes the novel therapeutic targets that are currently used in clinical trials with CAR-T cell therapy on autoimmune diseases and other challenging conditions, such as cardiac fibrosis, and different infections. Additionally, challenges and novel opportunities are discussed for expanding clinical access to this innovative therapy.

The role of CD95 in modulating CAR T-cell therapy: Challenges and therapeutic opportunities in oncology

CAR T cell therapy has revolutionized how we deliver cancer treatment, most notably for hematologic cancers, by compelling T cells to recognize and kill tumor cells. Nevertheless, current obstacles to utilizing this therapy in solid tumors and overcoming cancer resistance include radicalization. This review discusses how CD95 modulation can boost CAR T cell efficacy. Traditionally, CD95 was known to execute apoptosis induction, but it plays a dual role in induced cell death or in supporting cancer cell survival. Recent data have demonstrated that cancer cells escape CD95-mediated apoptosis via the downregulation of CD95, caspase 8 mutation, or the expression of the inhibition protein cFLIP. Additionally, the immunosuppressive tumor microenvironment, containing CD95L expressing immune cells, explains CAR T cell therapy resistance. Furthermore, we characterize the therapeutic potential of CD95 targeted approaches, including CD95L inhibition (APG101) and alterations in CAR T cell manufacturing (tyrosine kinase inhibitors to mitigate fratricide). In this review, we highlight the importance of multi-path way strategies combining CD95 modulation with CAR T cell engineering to overcome resistance, specifically to target tumor cells better and sustain CAR T cell persistence to enhance treatment efficacy in solid tumors.

CAR-T cell therapy: developments, challenges and expanded applications from cancer to autoimmunity

Chimeric Antigen Receptor (CAR)-T cell therapy has rapidly emerged as a groundbreaking approach in cancer treatment, particularly for hematologic malignancies. However, the application of CAR-T cell therapy in solid tumors remains challenging. This review summarized the development of CAR-T technologies, emphasized the challenges and solutions in CAR-T cell therapy for solid tumors. Also, key innovations were discussed including specialized CAR-T, combination therapies and the novel use of CAR-Treg, CAR-NK and CAR-M cells. Besides, CAR-based cell therapy have extended its reach beyond oncology to autoimmune disorders. We reviewed preclinical experiments and clinical trials involving CAR-T, Car-Treg and CAAR-T cell therapies in various autoimmune diseases. By highlighting these cutting-edge developments, this review underscores the transformative potential of CAR technologies in clinical practice.

Advances in chimeric antigen receptor T cell therapy for autoimmune and autoinflammatory diseases and their complications

Chimeric antigen receptor T (CAR-T) cells are genetically engineered T cells expressing transmembrane chimeric antigen receptors with specific targeting abilities. As an emerging immunotherapy, the use of CAR-T cells has made significant breakthroughs in cancer treatment, particularly for hematological malignancies. The success of CAR-T cell therapy in blood cancers highlights its potential for other conditions in which the clearance of pathological cells is therapeutic, such as liver diseases, infectious diseases, heart failure, and diabetes. Given the limitations of current therapies for autoimmune diseases, researchers have actively explored the potential therapeutic value of CAR-T cells and their derivatives in the field of autoimmune diseases. This review focuses on the research progress and current challenges of CAR-T cells in autoimmune diseases with the aim of providing a theoretical basis for the precise treatment of autoimmune diseases. In the future, CAR-T cells may present new therapeutic modalities and ultimately provide hope for patients with autoimmune diseases.

CAR T-cell therapy for systemic lupus erythematosus: current status and future perspectives

Systemic lupus erythematosus (SLE) and lupus nephritis (LN) are debilitating autoimmune disorders characterized by pathological autoantibodies production and immune dysfunction, causing chronic inflammation and multi-organ damage. Despite current treatments with antimalarial drugs, glucocorticoids, immunosuppressants, and monoclonal antibodies, a definitive cure remains elusive, highlighting an urgent need for novel therapeutic strategies. Recent studies indicate that chimeric antigen receptor T-cell (CAR-T) therapy has shown promising results in treating B-cell malignancies and may offer a significant breakthrough for non-malignant conditions like SLE. In this paper, we aim to provide an in-depth analysis of the advancements in CAR-T therapy for SLE, focusing on its potential to revolutionize treatment for this complex disease. We explore the fundamental mechanisms of CAR-T cell action, the rationale for its application in SLE, and the immunological underpinnings of the disease. We also summarize clinical data on the safety and efficacy of anti-CD19 and anti-B cell maturation antigen (BCMA) CAR-T cells in targeting B-cells in SLE. We discuss the clinical implications of these findings and the potential for CAR-T therapy to improve outcomes in severe or refractory SLE cases. The integration of CAR-T therapy into the SLE treatment paradigm presents a new horizon in autoimmunity research and clinical practice. This review underscores the need for continued exploration and optimization of CAR-T strategies to address the unmet needs of SLE patients.

CD19 CAR-T cell therapy: a new dawn for autoimmune rheumatic diseases?

Autoimmune rheumatic diseases (ARDs), such as rheumatoid arthritis, systemic lupus erythematosus, and systemic sclerosis, involve dysregulated immune responses causing chronic inflammation and tissue damage. Despite advancements in clinical management, many patients do not respond to current treatments, which often show limited efficacy due to the persistence of autoreactive B cells. Chimeric antigen receptor (CAR)-T cell therapy, which has shown success in oncology for B cell malignancies, targets specific antigens and involves the adoptive transfer of genetically engineered T cells. CD19 CAR-T cells, in particular, have shown promise in depleting circulating B cells and achieving clinical remission. This review discusses the potential of CD19 CAR-T cells in ARDs, highlighting clinical achievements and addressing key considerations such as optimal target cell populations, CAR construct design, acceptable toxicities, and the potential for lasting immune reset, crucial for the safe and effective adoption of CAR-T cell therapy in autoimmune treatments.

Exercise, autoimmune diseases and T-regulatory cells

Diverse forms of physical activities contribute to improvement of autoimmune diseases and may prevent disease burst. T regulatory cells (Tregs) maintain tolerance in autoimmune condition. Physical activity is one of the key factors causing enhancement of Tregs number and functions, keeping homeostatic state by its secrotome. Muscles secrete myokines like IL-6, PGC1α (PPARγ coactivator-1 α), myostatin, transforming growth factor β (TGF-β) superfamily), IL-15, brain derived neurotrophic factor (BDNF) and others. The current concept points to the role of exercise in induction of highly functional and stable muscle Treg phenotype. The residing-Tregs require IL6Rα signaling to control muscle function and regeneration. Skeletal muscle Tregs IL-6Rα is a key target for muscle-Tregs cross-talk. Thus, interplay between the Tregs-skeletal muscle, following exercise, contribute to the balance of immune tolerance and autoimmunity. The cargo delivery, in the local environment and periphery, is performed by extracellular vesicles (EVs) secreted by muscle and Tregs, which deliver proteins, lipids and miRNA during persistent exercise protocols. It has been suggested that this ensemble induce protection against autoimmune diseases.

Combinatorial genetic engineering strategy for immune protection of stem cell-derived beta cells by chimeric antigen receptor regulatory T cells

Regenerative medicine is a rapidly expanding field harnessing human pluripotent stem cell (hPSC)-derived cells and tissues to treat many diseases, including type 1 diabetes. However, graft immune protection remains a key challenge. Chimeric antigen receptor (CAR) technology confers new specificities to effector T cells and immunosuppressive regulatory T cells (Tregs). One challenge in CAR design is identifying target molecules unique to the cells of interest. Here, we employ combinatorial genetic engineering to confer CAR-Treg-mediated localized immune protection to stem cell-derived cells. We engineered hPSCs to express truncated epidermal growth factor receptor (EGFRt), a biologically inert and generalizable target for CAR-Treg homing and activation, and generated CAR-Tregs recognizing EGFRt. Strikingly, CAR-Tregs suppressed innate and adaptive immune responses in vitro and prevented EGFRt-hPSC-derived pancreatic beta-like cell (sBC [stem cell-derived beta cell]) graft immune destruction in vivo. Collectively, we provide proof of concept that hPSCs and Tregs can be co-engineered to protect hPSC-derived cells from immune rejection upon transplantation.

Engineering CAR-T therapies for autoimmune disease and beyond

Chimeric antigen receptor-T cell (CAR-T) therapy has transformed the management of refractory hematological malignancies. Now that targeting pathogenic cells of interest with antigen-directed cytotoxic T lymphocytes is possible, the field is expanding the reach of CAR-T therapy beyond oncology. Recently, breakthrough progress has been made in the application of CAR-T technology to autoimmune diseases, exploiting the same validated targets that were used by pioneering CAR-T therapies in hematology. Here, we discuss recent advances and outcomes that are paving the way for extension to new therapeutic areas, including autoimmunity.

The landscape of new therapeutic opportunities for IBD

This chapter presents an overview of the emerging strategies to address the unmet needs in the management of inflammatory bowel diseases (IBD). IBD poses significant challenges, as over half of patients experience disease progression despite interventions, leading to irreversible complications, and a substantial proportion do not respond to existing therapies, such as biologics. To overcome these limitations, we describe a diverse array of novel therapeutic approaches. In the area of immune homeostasis restoration, the focus is on targeting cytokine networks, leukocyte trafficking, novel immune pathways, and cell therapies involving regulatory T cells and mesenchymal stem cells (MSC). Recognizing the critical role of impaired intestinal barrier integrity in IBD, we highlight therapies aimed at restoring barrier function and promoting mucosal healing, such as those targeting cell proliferation, tight junctions, and lipid mediators. Addressing the challenges posed by fibrosis and fistulas, we describe emerging targets for reversing fibrosis like kinase and cytokine inhibitors and nuclear receptor agonists, as well as the potential of MSC for fistulas. The restoration of a healthy gut microbiome, through strategies like fecal microbiota transplantation, rationally defined bacterial consortia, and targeted antimicrobials, is also highlighted. We also describe innovative approaches to gut-targeted drug delivery to enhance efficacy and minimize side effects. Reinforcing these advancements is the critical role of precision medicine, which emphasizes the use of multiomics analysis for the discovery of biomarkers to enable personalized IBD care. Overall, the emerging landscape of therapeutic opportunities for IBD holds great potential to surpass the therapeutic ceiling of current treatments.

Cell therapy in Sjögren's syndrome: opportunities and challenges

Sjögren's syndrome (SS) is a chronic autoimmune disease caused by immune system disorders. The main clinical manifestations of SS are dry mouth and eyes caused by the destruction of exocrine glands, such as the salivary and lacrimal glands, and systemic manifestations, such as interstitial pneumonia, interstitial nephritis and vasculitis. The pathogenesis of this condition is complex. However, this has not been fully elucidated. Treatment mainly consists of glucocorticoids, disease-modifying antirheumatic drugs and biological agents, which can only control inflammation but not repair the tissue. Therefore, identifying methods to regulate immune disorders and repair damaged tissues is imperative. Cell therapy involves the transplantation of autologous or allogeneic normal or bioengineered cells into the body of a patient to replace damaged cells or achieve a stronger immunomodulatory capacity to cure diseases, mainly including stem cell therapy and immune cell therapy. Cell therapy can reduce inflammation, relieve symptoms and promote tissue repair and regeneration of exocrine glands such as the salivary glands. It has broad application prospects and may become a new treatment strategy for patients with SS. However, there are various challenges in cell preparation, culture, storage and transportation. This article reviews the research status and prospects of cell therapies for SS.

Evolving understanding of autoimmune mechanisms and new therapeutic strategies of autoimmune disorders

Autoimmune disorders are characterized by aberrant T cell and B cell reactivity to the body's own components, resulting in tissue destruction and organ dysfunction. Autoimmune diseases affect a wide range of people in many parts of the world and have become one of the major concerns in public health. In recent years, there have been substantial progress in our understanding of the epidemiology, risk factors, pathogenesis and mechanisms of autoimmune diseases. Current approved therapeutic interventions for autoimmune diseases are mainly non-specific immunomodulators and may cause broad immunosuppression that leads to serious adverse effects. To overcome the limitations of immunosuppressive drugs in treating autoimmune diseases, precise and target-specific strategies are urgently needed. To date, significant advances have been made in our understanding of the mechanisms of immune tolerance, offering a new avenue for developing antigen-specific immunotherapies for autoimmune diseases. These antigen-specific approaches have shown great potential in various preclinical animal models and recently been evaluated in clinical trials. This review describes the common epidemiology, clinical manifestation and mechanisms of autoimmune diseases, with a focus on typical autoimmune diseases including multiple sclerosis, type 1 diabetes, rheumatoid arthritis, systemic lupus erythematosus, and sjögren's syndrome. We discuss the current therapeutics developed in this field, highlight the recent advances in the use of nanomaterials and mRNA vaccine techniques to induce antigen-specific immune tolerance.

Current cell therapies for systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease in which multiple organs are damaged by the immune system. Although standard treatment options such as hydroxychloroquine (HCQ), glucocorticoids (GCs), and other immunosuppressive or immune-modulating agents can help to manage symptoms, they do not offer a cure. Hence, there is an urgent need for the development of novel drugs and therapies. In recent decades, cell therapies have been used for the treatment of SLE with encouraging results. Hematopoietic stem cell transplantation, mesenchymal stem cells, regulatory T (Treg) cell, natural killer cells, and chimeric antigen receptor T (CAR T) cells are advanced cell therapies which have been developed and evaluated in clinical trials in humans. In clinical application, each of these approaches has shown advantages and disadvantages. In addition, further studies are necessary to conclusively establish the safety and efficacy of these therapies. This review provides a summary of recent clinical trials investigating cell therapies for SLE treatment, along with a discussion on the potential of other cell-based therapies. The factors influencing the selection of common cell therapies for individual patients are also highlighted.

The Future of CAR T Therapeutics to Treat Autoimmune Disorders

The concept of chimeric antigen receptor (CAR) T cell therapy emerged from cancer immunotherapy and has been rapidly adapted and developed for the treatment of autoimmune, especially B-cell-driven, diseases since the first publication of an article featuring a patient with systemic lupus erythematosus in 2021. Phase II studies are about to start, but up to now, only case reports and small series have been published. In contrast to hemato-oncological diseases, where an aggressive response to malignant cells and long-lasting persistence of CAR T cells has been aimed at and observed in many patients, this is not the case with autoimmune diseases but might not be necessary to control disease. Future studies will focus on the optimal target but also on the optimal level of immunogenicity. The latter can be influenced by numerous modulations that affect not only cytokine release but also regulation. In addition, there are potential applications in regulatory cells such as CAR regulatory T cells (Treg). The question of toxicity reduction must also be addressed, as long-term complications such as the potential development of malignant diseases, infections, or cytopenia must be considered even more critically in the area of autoimmune diseases than is the case for patients with oncologic diseases. Alternative antibody-based therapies using the same target (e.g., CD3/CD19 bispecific targeting antibodies) have not been used in these patients and might also be considered in the future. In conclusion, CAR T cell therapy represents a promising therapeutic approach for autoimmune diseases, offering a targeted strategy to modulate immune responses and restore immune tolerance.

Immune regulation and therapeutic application of T regulatory cells in liver diseases

CD4+ CD25+ FOXP3+ T regulatory cells (Tregs) are a subset of the immunomodulatory cell population that can inhibit both innate and adaptive immunity by various regulatory mechanisms. In hepatic microenvironment, proliferation, plasticity, migration, and function of Tregs are interrelated to the remaining immune cells and their secreted cytokines and chemokines. In normal conditions, Tregs protect the liver from inflammatory and auto-immune responses, while disruption of this crosstalk between Tregs and other immune cells may result in the progression of chronic liver diseases and the development of hepatic malignancy. In this review, we analyze the deviance of this protective nature of Tregs in response to chronic inflammation and its involvement in inducing liver fibrosis, cirrhosis, and hepatocellular carcinoma. We will also provide a detailed emphasis on the relevance of Tregs as an effective immunotherapeutic option for autoimmune diseases, liver transplantation, and chronic liver diseases including liver cancer.

Chimeric antigen receptor T-cell therapy in rheumatology: B-cell depletion 2.0

PURPOSE OF REVIEW

Chimeric antigen receptor T-cell therapy (CAR-T) has revolutionized cancer treatment by harnessing the immune system's power to target malignancies. CD19, a B-cell surface antigen, a key target for CAR-T cell therapy in hematological malignancies, displayed remarkable clinical responses. Recently, there has been a growing interest in exploring the application of CD19 CAR-T cell therapy beyond oncology. The rationale for investigating CD19 CAR-T cells in Rheumatology stems from their ability to selectively target B cells, which play a central pathogenic role through autoantibody-dependent and independent mechanisms.

RECENT FINDINGS

Preclinical and five completed clinical studies have shown remarkable efficacy and safety in diseases such as systemic lupus erythematosus, antisynthetase syndrome, and systemic sclerosis. It is thus not surprising that 17 active clinical trials exploring CAR-T cells in Rheumatology are in progress.

SUMMARY

Although CAR-T therapy holds great promise in Rheumatology, many challenges loom. Whether this new way to deplete B-cells is superior to conventional antibody-based B-cell depletion in rheumatic diseases will be closely watched in the coming years.

Hsa-miR-21-5p reflects synovitis and tenosynovitis components of musculoskeletal ultrasonography Seven-joint scores in rheumatoid arthritis disease and predicts the disease flare

Rheumatoid arthritis (RA) is characterized by progressive joint destruction with subsequent serious disability. Objective biomarkers of RA course progression are lacking, which necessitates the discovery of activity indicators and predictors of the disease outcome. Musculoskeletal Ultrasound Seven-joint Score (MSUS7) is proposed as a reliable technique to evaluate radiographic RA progression. Homo sapiens-microRNA-21-5p (hsa-miR-21-5p) plays an important role during joint remodeling and the pro-inflammatory process driving RA progression. We aimed to evaluate plasma hsa-miR-21-5p as a noninvasive RA activity biomarker and to investigate if hsa-miR-21-5p is linked to MSUS7 components in the context of RA activity. This cross-sectional study included 71 RA patients classified into inactive (n = 36) and active (n = 35) groups according to the Disease Activity Score 28-joint count with ESR (DAS28-ESR). Joints were assessed by MSUS7. Gray-scale ultrasound (GSUS) and power Doppler ultrasound (PDUS) were used to rate the synovitis, tenosynovitis, and erosion in the joints. Plasma hsa-miR-21-5p expression was measured by real-time PCR. The absolute count of regulatory T cell (Treg) was calculated after Treg frequency was assessed by flow cytometry. Results: Hsa-miR-21 expression was significantly up-regulated in the active RA group with a median fold change of 51.6 in comparison to the inactive cases with a median fold change of 7.7 (p < 0.001). Hsa-miR-21-5p was positively correlated with DAS28-ESR, C reactive protein (CRP), and rheumatoid factor (r = 0.7, p < 0.001, r = 0. 0.6, p < 0.001, and r = 0.4, p = 0.002, respectively), while negatively correlated with Treg absolute count (r = -0.4, p < 0.001). Hsa-miR-21-5p levels were correlated with synovitis and tenosynovitis in GSUS (r = 0.4, p < 0.001, r = 0.3, p = 0.025, respectively) and in PDUS (r = 0.5, p < 0.001 and 0.4, p = 0.001, respectively). The hsa-miR-21-5p accurately distinguished RA activity [AUC 0.933, 94.3% sensitivity, and 86.1% specificity]. Logistic regression analysis revealed hsa-miR-21-5p as an independent predictor for RA flare (OR = 1.228, p = 0.004). Hsa-miR-21-5p was linked to synovitis and tenosynovitis components of the MSUS7. Up-regulated hsa-miR-21-5p can be utilized as a predictor for RA disease flare.

Bioanalytical Methods for Characterization of CAR-T Cellular Kinetics: Comparison of PCR Assays and Matrices

Recently, multiple chimeric antigen receptor T-cell (CAR-T)-based therapies have been approved for treating hematological malignancies, targeting CD19 and B-cell maturation antigen. Unlike protein or antibody therapies, CAR-T therapies are "living cell" therapies whose pharmacokinetics are characterized by expansion, distribution, contraction, and persistence. Therefore, this unique modality requires a different approach for quantitation compared with conventional ligand binding assays implemented for most biologics. Cellular (flow cytometry) or molecular assays (polymerase chain reaction (PCR)) can be deployed with each having unique advantages and disadvantages. In this article, we describe the molecular assays utilized: quantitative PCR (qPCR), which was the initial platform used to estimate transgene copy numbers and more recently droplet digital PCR (ddPCR) which quantitates the absolute copy numbers of CAR transgene. The comparability of the two methods in patient samples and of each method across different matrices (isolated CD3+ T-cells or whole blood) was also performed. The results show a good correlation between qPCR and ddPCR for the amplification of same gene in clinical samples from a CAR-T therapy trial. In addition, our studies show that the qPCR-based amplification of transgene levels was well-correlated, independent of DNA sources (either CD3+ T-cells or whole blood). Our results also highlight that ddPCR can be a better platform for monitoring samples at the early phase of CAR-T dosing prior to expansion and during long-term monitoring as they can detect samples with very low copy numbers with high sensitivity, in addition to easier implementation and sample logistics.

Supraphysiological FOXP3 expression in human CAR-Tregs results in improved stability, efficacy, and safety of CAR-Treg products for clinical application

The forkhead family transcription factor (FOXP3) is an essential regulator for the development of regulatory T cells (Tregs) and orchestrates both suppressive function and Treg lineage identity. Stable expression of FOXP3 enables Tregs to maintain immune homeostasis and prevent autoimmunity. However, under pro-inflammatory conditions, FOXP3 expression in Tregs can become unstable, leading to loss of suppressive function and conversion into pathogenic T effector cells. Therefore, the success of adoptive cell therapy with chimeric antigen receptor (CAR) Tregs is highly dependent on the stability of FOXP3 expression to ensure the safety of the cell product. To warrant the stable expression of FOXP3 in CAR-Treg products, we have developed an HLA-A2-specific CAR vector that co-expresses FOXP3. The transduction of isolated human Tregs with the FOXP3-CAR led to an increase in the safety and efficacy of the CAR-Treg product. In a hostile microenvironment, under pro-inflammatory and IL-2-deficient conditions, FOXP3-CAR-Tregs showed a stable expression of FOXP3 compared to Control-CAR-Tregs. Furthermore, additional exogenous expression of FOXP3 did not induce phenotypic alterations and dysfunctions such as cell exhaustion, loss of functional Treg characteristics or abnormal cytokine secretion. In a humanized mouse model, FOXP3-CAR-Tregs displayed an excellent ability to prevent allograft rejection. Furthermore, FOXP3-CAR-Tregs revealed coherent Treg niche-filling capabilities. Overexpression of FOXP3 in CAR-Tregs has thereby the potential to increase the efficacy and reliability of cellular products, promoting their clinical use in organ transplantation and autoimmune diseases.

The potential of regulatory T cell-based therapies for alopecia areata

Cytotoxic T lymphocyte has been a concern for the etiopathogenesis of alopecia areata (AA), some recent evidence suggests that the regulatory T (T_reg) cell deficiency is also a contributing factor. In the lesional scalp of AA, T_reg cells residing in the follicles are impaired, leading to dysregulated local immunity and hair follicle (HF) regeneration disorders. New strategies are emerging to modulate T_reg cells' number and function for autoimmune diseases. There is much interest to boost T_reg cells in AA patients to suppress the abnormal autoimmunity of HF and stimulate hair regeneration. With few satisfactory therapeutic regimens available for AA, T_reg cell-based therapies could be the way forward. Specifically, CAR-T_reg cells and novel formulations of low-dose IL-2 are the alternatives.