Prevention of Allograft Rejection by Use of Regulatory T Cells With an MHC-Specific Chimeric Antigen Receptor

Nanoneedle-Based Electroporation for Efficient Manufacturing of Human Primary Chimeric Antigen Receptor Regulatory T-Cells

Regulatory T cells (Tregs) play a crucial role in moderating immune responses offering promising therapeutic options for autoimmune diseases and allograft rejection. Genetically engineering Tregs with chimeric antigen receptors (CARs) enhances their targeting specificity and efficacy. With non-viral transfection methods suffering from low efficiency and reduced cell viability, viral transduction is currently the only viable approach for GMP-compliant CAR-Treg production. However, viral transduction raises concerns over immunogenicity, insertional mutagenesis risk, and high costs, which limit clinical scalability. This study introduces a scalable nanoneedle electroporation (nN-EP) platform for GMP-compatible transfection of HLA-A2-specific CAR plasmids into primary human Tregs. The nN-EP system achieves 43% transfection efficiency, outperforming viral transduction at multiplicity of infection 1 by twofold. Importantly, nN-EP preserves Treg viability, phenotype and proliferative capacity. HLA-A2-specific CAR-Tregs generated using nN-EP show specific activation and superior suppressive function compared to polyclonal or virally transduced Tregs in the presence of HLA-A2 expressing antigen presenting cells. These findings underscore the potential of nN-EP as a GMP-suitable method for CAR-Treg production, enabling broader clinical application in immune therapies.

CAR Treg synergy with anti-CD154 promotes infectious tolerance and dictates allogeneic heart transplant acceptance

Successful allograft-specific tolerance induction would eliminate the need for daily immunosuppression and improve posttransplant quality of life. Adoptive cell therapy with regulatory T cells expressing donor-specific chimeric antigen receptors (CAR Tregs) is a promising strategy but, as monotherapy, cannot prolong survival with allografts with multiple MHC mismatches. Using an HLA-A2-transgenic haplo-mismatched heart transplantation model in immunocompetent C57BL/6 recipients, we showed that HLA-A2-specific CAR (A2.CAR) Tregs were able to synergize with a low dose of anti-CD154 to enhance graft survival. Using haplo-mismatched grafts expressing the 2W-OVA transgene and tetramer-based tracking of 2W- and OVA-specific T cells, we showed that in mice with accepted grafts, A2.CAR Tregs inhibited donor-specific T cell, B cell, and antibody responses and promoted a substantial increase in endogenous FOXP3+ Tregs with indirect donor specificity. By contrast, in mice where A2.CAR Tregs failed to prolong graft survival, FOXP3- A2.CAR T cells preferentially accumulated in rejecting allografts, and endogenous donor-specific responses were not controlled. This study therefore provides evidence for synergy between A2.CAR Tregs and CD154 blockade to promote infectious tolerance in immunocompetent recipients of haplo-mismatched heart grafts and defines features of A2.CAR Tregs when they fail to reshape host immunity toward allograft tolerance.

Chimeric anti-HLA antibody receptor engineered human regulatory T cells suppress alloantigen-specific B cells from pre-sensitized transplant recipients

Organ transplantation is a lifesaving procedure, with 50,000 transplants happening every year in the United States. However, many patients harbor antibodies and B cells directed against allogeneic human leukocyte antigen (HLA) molecules, notably HLA-A2, greatly decreasing their likelihood of receiving a compatible organ. Moreover, antibody-mediated rejection is a significant contributor to chronic transplant rejection. Current strategies to desensitize patients non- specifically target circulating antibodies and B cells, resulting in poor efficacy and complications. Regulatory T cells (Tregs) are immune cells dedicated to suppressing specific immune responses by interacting with both innate and adaptive immune cells. Here, we genetically modified human Tregs with a chimeric anti-HLA antibody receptor (CHAR) consisting of an extracellular HLA-A2 protein fused to a CD28-CD3zeta intracellular signaling domain, driving Treg activation upon recognition of anti-HLA-A2 antibodies on the surface of alloreactive B cells. We find that HLA-A2 CHAR Tregs get activated specifically by anti-HLA-A2 antibody-producing cells. Of note, HLA-A2 CHAR activation does not negatively affect Treg stability, as measured by expression of the Treg lineage transcription factors FOXP3 and HELIOS. Interestingly, HLA-A2 CHAR Tregs are not cytotoxic towards anti-HLA-A2 antibody-producing cells, unlike HLA-A2 CHAR modified conventional CD4 + T cells. Importantly, HLA-A2 CHAR Tregs recognize and significantly suppress high affinity IgG antibody production by B cells from HLA-A2 sensitized patients. Altogether, our results provide proof-of-concept of a new strategy to specifically inhibit alloreactive B cells to desensitize transplant recipients.

The Therapeutic Use and Potential of MSCs: Advances in Regenerative Medicine

Mesenchymal stem cells (MSCs) have emerged as a relevant strategy in regenerative medicine due to their multipotent differentiation capacity, immunomodulatory properties, and therapeutic applications in various medical fields. This review explores the therapeutic use of MSCs, focusing on their role in treating autoimmune disorders and neoplastic diseases and in tissue regeneration. We discuss the mechanisms underlying MSC-mediated tissue repair, including their paracrine activity, migration to injury sites, and interaction with the immune system. Advances in cellular therapies such as genome engineering and MSC-derived exosome treatments further enhance their applicability. Key methodologies analyzed include genomic studies, next-generation sequencing (NGS), and bioinformatics approaches to optimize MSC-based interventions. Additionally, we reviewed preclinical and clinical evidence demonstrating the therapeutic potential of MSCs in conditions such as graft-versus-host disease, osteoarthritis, liver cirrhosis, and neurodegenerative disorders. While promising, challenges remain regarding standardization, long-term safety, and potential tumorigenic risks associated with MSC therapy. Future research should focus on refining MSC-based treatments to enhance efficacy and minimize risks. This review underscores the need for large-scale clinical trials to validate MSC-based interventions and fully harness their therapeutic potential.

Tonic signaling in CAR-T therapy: the lever long enough to move the planet

Chimeric antigen receptor (CAR) T-cell therapy has shown remarkable efficacy in treating hematological malignancies and is expanding into other indications such as autoimmune diseases, fibrosis, aging and viral infection. However, clinical challenges persist in treating solid tumors, including physical barriers, tumor heterogeneity, poor in vivo persistence, and T-cell exhaustion, all of which hinder therapeutic efficacy. This review focuses on the critical role of tonic signaling in CAR-T therapy. Tonic signaling is a low-level constitutive signaling occurring in both natural and engineered antigen receptors without antigen stimulation. It plays a pivotal role in regulating immune cell homeostasis, exhaustion, persistence, and effector functions. The "Peak Theory" suggests an optimal level of tonic signaling for CAR-T function: while weak tonic signaling may result in poor proliferation and persistence, excessively strong signaling can cause T cell exhaustion. This review also summarizes the recent progress in mechanisms underlying the tonic signaling and strategies to fine-tune the CAR tonic signaling. By understanding and precisely modulating tonic signaling, the efficacy of CAR-T therapies can be further optimized, offering new avenues for treatment across a broader spectrum of diseases. These findings have implications beyond CAR-T cells, potentially impacting other engineered immune cell therapies such as CAR-NK and CAR-M.

Gene editing of CD3 epsilon to redirect regulatory T cells for adoptive T cell transfer

Adoptive transfer of antigen-specific regulatory T cells (Tregs) is a promising strategy to combat immunopathologies in transplantation and autoimmune diseases. However, their low frequency in peripheral blood poses challenges for both manufacturing and clinical application. Chimeric antigen receptors have been used to redirect the specificity of Tregs, using retroviral vectors. However, retroviral gene transfer is costly, time consuming, and raises safety issues. Here, we explored non-viral CRISPR-Cas12a gene editing to redirect Tregs, using human leukocyte antigen (HLA)-A2-specific constructs for proof-of-concept studies in transplantation models. Knock-in of an antigen-binding domain into the N terminus of CD3 epsilon (CD3ε) gene generates Tregs expressing a chimeric CD3ε-T cell receptor fusion construct (TRuC) protein that integrates into the endogenous TCR/CD3 complex. These CD3ε-TRuC Tregs exhibit potent antigen-dependent activation while maintaining responsiveness to TCR/CD3 stimulation. This enables preferential enrichment of TRuC-redirected Tregs over CD3ε knockout Tregs via repetitive CD3/CD28 stimulation in a good manufacturing practice-compatible expansion system. CD3ε-TRuC Tregs retained their phenotypic, epigenetic, and functional identity. In a humanized mouse model, HLA-A2-specific CD3ε-TRuC Tregs demonstrate superior protection of allogeneic HLA-A2+ skin grafts from rejection compared with polyclonal Tregs. This approach provides a pathway for developing clinical-grade CD3ε-TRuC-based Treg cell products for transplantation immunotherapy and other immunopathologies.

Immunometabolism of Liver Xenotransplantation and Prospective Solutions

End-stage liver diseases, such as hepatocellular carcinoma or acute liver failure, critically necessitate liver transplantation. However, the shortage of available organ donors fails to meet the rapidly growing transplantation demand. Due to the high similarity of liver tissue structure and metabolism between miniature pigs and humans, xenotransplantation of pig livers is considered as a potentially viable solution to organ scarcity. In the 2024, teams from China first time have successfully transplanted a genetically modified Bama miniature pig liver into a clinically brain-dead man lasting for 10 days. This milestone in human xenotransplantation research not only confirms the feasibility of clinical application of xenotransplantation, but also underscores the daunting and protracted nature of this pathway. Despite advanced gene-editing technologies theoretically circumventing the occurrence of most transplant rejection reactions, patients still face challenges such as chronic immune rejection, coagulation disorders, and thrombotic microangiopathy after receiving xenografts. Moreover, prolonged use of immunosuppressive drugs may induce irreversible immune dysfunction, leading to opportunistic infections and metabolic disorders. This article compares the similarities and differences in livers between humans and pigs, summarizes the immunometabolism of xenotransplantation based on current findings, and provides research perspectives on pre-transplantation and post-transplantation strategies for prolonging the survival time of xenografts.

How to focus on autoantigen-specific lymphocytes: a review on diagnosis and treatment of Sjogren's syndrome

Sjogren's syndrome (SS) is an autoimmune epithelitis characterized by focal lymphocytic infiltration against self-antigens leading to progressive glandular dysfunction, which can develop to multisystem manifestation. The classification criteria for SS emphasizes glandular lymphocyte infiltrates and anti-SSA/SSB seropositivity, which is usually manifested in advanced patients. Therapeutically, apart from symptomatic treatment, treatment of SS is based on glucocorticoids and conventional synthetic disease-modifying antirheumatic drugs with global immunosuppression, but the efficacy of biologic or targeted synthetic therapies is still sparse. Currently, emerging studies focus on autoantigen-specific immunotherapies to treat autoimmune disorders by directly eliminating autoreactive cell subsets and inducing tolerance by increasing the autoreactive regulatory lymphocytes. Herein, we summarize the current state of research on the autoantigen-specific approaches for detecting autoreactive lymphocytes and outline the current autoantigen-specific immunotherapies in other autoimmune disorders and their attempts in treatment of SS. Last, we discuss the potential value of focusing on autoantigen-specific lymphocytes in the early diagnosis, monitoring, and targeted treatment of SS. Potential strategies for targeting autoreactive lymphocytes need to be confirmed in SS.

Advances in engineered T cell immunotherapy for autoimmune and other non-oncological diseases

Adoptive immunotherapy using engineered T cells expressing chimeric antigen receptors has shown remarkable success in treating patients with hematological malignancies. However, realizing broader therapeutic applications of engineered T cells in other diseases requires further exploration in clinical investigations. In this review, we highlight recent advances in the engineering of T cells in non-oncology areas, including autoimmune and inflammatory diseases, infections, fibrosis, hemophilia, and aging. Chimeric antigen receptor immunotherapy has shown good outcomes in non-oncology areas, but many challenges remain in improving its safety and efficacy and and expanding its application to the treatment of non-oncological diseases.

Quo vadis autoimmune hepatitis? - Summary of the 5th international autoimmune hepatitis group research workshop 2024

Autoimmune hepatitis (AIH) is a rare chronic liver disease with an increasing incidence in many countries. Chronic autoimmune responses against the liver can cause hepatic and extrahepatic symptoms, decreased quality of life and reduced liver transplant-free survival if inadequately treated. Although standard treatment with corticosteroids and thiopurines improves the life expectancy of patients with AIH, remission rates and tolerability are generally overestimated and the development of alternative first-line and salvage therapies has been disappointingly slow compared to in rheumatological diseases or inflammatory bowel disease. Other gaps include the lack of disease-specific diagnostic markers for AIH. Similarly, the new entity of drug-induced autoimmune-like hepatitis underscores the need to re-evaluate previous diagnostic criteria. The International AIH Group (IAIHG) has initiated a series of research workshops over the last decade to promote the identification of research gaps and subsequently improve the pace of scientific progress by stimulating collaboration between expert centres. This review reports on the results of the 5th Research Workshop, held in Hannover, Germany in June 2024, and summarises the progress made since the 4th Workshop in 2022. Patient representatives from the European Reference Network (ERN) Rare Liver Youth Panel participated in the workshop. The specific objectives of this year's 5th Workshop were: (1) To further improve diagnostics. (2) Initiate clinical trials including knowledge transfer on drugs from extrahepatic immune-mediated diseases, including B cell-depleting CAR T cells. (3) Utilisation of multi-omics approaches to improve the understanding of disease pathogenesis. (4) Application of machine learning-based approaches established in oncology or transplantation medicine to improve diagnosis and outcome prediction in AIH.

Unlocking Transplant Tolerance with Biomaterials

For patients suffering from organ failure due to injury or autoimmune disease, allogeneic organ transplantation with chronic immunosuppression is considered the god standard in terms of clinical treatment. However, the true "holy grail" of transplant immunology is operational tolerance, in which the recipient exhibits a sustained lack of alloreactivity toward unencountered antigen presented by the donor graft. This outcome is resultant from critical changes to the phenotype and genotype of the immune repertoire predicated by the activation of specific signaling pathways responsive to soluble and mechanosensitive cues. Biomaterials have emerged as a medium for interfacing with and reprogramming these endogenous pathways toward tolerance in precise, minimally invasive, and spatiotemporally defined manners. By viewing seminal and contemporary breakthroughs in transplant tolerance induction through the lens of biomaterials-mediated immunomodulation strategies-which include intrinsic material immunogenicity, the depot effect, graft coatings, induction and delivery of tolerogenic immune cells, biomimicry of tolerogenic immune cells, and in situ reprogramming-this review emphasizes the stunning diversity of approaches in the field and spotlights exciting future directions for research to come.

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.

Complement and T cell activation in transplantation

The complement system plays a critical role in modulating adaptive T cell responses. Coordination of the proinflammatory signaling cascade and complement regulators permits efficient T cell priming and survival, while minimizing off-target damage to healthy host cells. In the context of transplantation, anti-donor T cell immunity remains a barrier to long term graft health and complement-targeted therapies have shown the potential to significantly improve patient outcomes. Here we will review our current understanding of complement-mediated T cell function and how these findings may be harnessed in organ transplantation.

Cars pick up another passenger: Organ transplantation

With over 30,000 patients having received CAR T cells as a treatment for malignancy, our experience in oncology has facilitated numerous efforts to adapt the CAR therapeutic platform for diseases and conditions beyond cancer. Recognition of their efficacy, where traditional small molecule or biologic therapies fail, has spurred multiple efforts leveraging CAR T cells for immune modulation in the setting of organ/tissue transplantation. In the present review, we discuss CAR T cell approaches that are currently under development, to target both humoral and cellular alloimmunity. These include CAR T platforms repurposed from oncology and autoimmune diseases, as well as ones designed specifically to target alloimmunity in transplant. We also present important challenges and application considerations that will need to be addressed before we can expect successful clinical translation. Finally, we highlight a few of the exciting advances currently in development that are likely to pave a smoother path to translating CAR T cell therapies into transplant patients.

Conferring alloantigen specificity to regulatory T cells: A comparative analysis of cell preparations undergoing clinical development in transplantation

Conferring alloantigen-specificity to ex vivo expanded CD4+CD25+FOXP3+ regulatory T cells (Tregs) increases their capacity to counteract effector alloimmune responses following adoptive transfer into transplant recipients. Three strategies are currently undergoing clinical development, which involve the following: (1) expanding Tregs in the presence of donor B cells (donor alloantigen-reactive [DAR] Tregs); (2) culturing Tregs with donor cells in the presence of costimulation blockade (CSB-Tregs); and (3) transducing Tregs with an human leukocyte antigen A2-specific chimeric antigen receptor (CAR-Tregs). Our goal in this study was to assess the relative potency of each of these manufactured Treg products both in vitro and in vivo. When compared with polyclonal Tregs, all 3 manufacturing strategies increased the precursor frequency of alloreactive Tregs, and this was proportional to the overall in vitro immunosuppressive properties of the cell products. Accordingly, CAR-Tregs, which contained the highest frequency of donor-reactive Tregs, exhibited the strongest suppressive effects on a cell-per-cell basis. Similarly, in an in vivo mouse model of graft-vs-host disease, infusion of CAR-Tregs conferred a significantly longer recipient survival than any other Treg product. Our results highlighting the alloantigen-reactivity and associated immunosuppressive properties of different manufactured Treg products have implications for the mechanistic interpretation of currently ongoing clinical trials in transplantation.

High-affinity chimeric antigen receptor signaling induces an inflammatory program in human regulatory T cells

Regulatory T cells (Tregs) are promising cellular therapies to induce immune tolerance in organ transplantation and autoimmune disease. The success of chimeric antigen receptor (CAR) T cell therapy for cancer has sparked interest in using CARs to generate antigen-specific Tregs. Here, we compared CAR with endogenous T cell receptor (TCR)/CD28 activation in human Tregs. Strikingly, CAR Tregs displayed increased cytotoxicity and diminished suppression of antigen-presenting cells and effector T (Teff) cells compared with TCR/CD28-activated Tregs. RNA sequencing revealed that CAR Tregs activate Teff cell gene programs. Indeed, CAR Tregs secreted high levels of inflammatory cytokines, with a subset of FOXP3+ CAR Tregs uniquely acquiring CD40L surface expression and producing IFN-γ. Interestingly, decreasing CAR antigen affinity reduced Teff cell gene expression and inflammatory cytokine production by CAR Tregs. Our findings showcase the impact of engineered receptor activation on Treg biology and support tailoring CAR constructs to Tregs for maximal therapeutic efficacy.

Cell Therapy as a Way to Increase the Effectiveness of Hematopoietic Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a standard method for treating a number of pathologies, primarily blood diseases. Timely restoration of the immune system after HSCT is a critical factor associated with the development of complications such as relapses or secondary tumors and various infections, as well as the graft-versus-host reaction in allogeneic transplantation, which ultimately affects the survival of patients. Introduction into the recipient's body of immune system cells that are incapable of sensitization by recipient antigens during the period of immune reconstitution can increase the rate of restoration of the immune system, as well as reduce the risk of complications. This review presents the results of studies on cell therapy with various cell subpopulations of both bone marrow and mesenchymal origin during HSCT.

From promise to practice: CAR T and Treg cell therapies in autoimmunity and other immune-mediated diseases

Autoimmune diseases, characterized by the immune system's attack on the body's own tissues, affect millions of people worldwide. Current treatments, which primarily rely on broad immunosuppression and symptom management, are often associated with significant adverse effects and necessitate lifelong therapy. This review explores the next generation of therapies for immune-mediated diseases, including chimeric antigen receptor (CAR) T cell and regulatory T cell (Treg)-based approaches, which offer the prospect of targeted, durable disease remission. Notably, we highlight the emergence of CD19-targeted CAR T cell therapies, and their ability to drive sustained remission in B cell-mediated autoimmune diseases, suggesting a possible paradigm shift. Further, we discuss the therapeutic potential of Type 1 and FOXP3+ Treg and CAR-Treg cells, which aim to achieve localized immune modulation by targeting their activity to specific tissues or cell types, thereby minimizing the risk of generalized immunosuppression. By examining the latest advances in this rapidly evolving field, we underscore the potential of these innovative cell therapies to address the unmet need for long-term remission and potential tolerance induction in individuals with autoimmune and immune-mediated diseases.

Injectable Genetic Engineering Hydrogel for Promoting Spatial Tolerance of Transplanted Kidney in Situ

The establishment of a tolerant space to realize the co-stimulation of cytokines and contact-dependent molecules remain challenging in allotransplant. Here, an injectable genetically engineered hydrogel (iGE-Gel) is reported, which developed with a multivalent network of FOXP3 engineered extracellular vesicles (Foe-EVs) through the hydrophobic interaction between stearic acid modified hyaluronic acid (HASA) and the membrane phospholipids of extracellular vesicles (EVs). The iGE-Gel exhibited self-healing properties, injectability and biocompatibility. It is revealed that iGE-Gel displayed with abundant regulatory cytokines and coinhibitory contact molecules, promoting the formation of immune tolerance in situ. The multiplex immunohistofluorescence confirmed tolerant niches is dominated by FOXP3+ Tregs and PDL1+ cells in the allograft, which reduced the drainage of alloantigens to subcapsular sinus of lymph nodes, and suppressed the formation of germinal centers. Remarkably, the proportion of alloreactive T cells (IFN-γ/IL-2) and B cells (IgG1/IgG2a/IgG3) as well as the serum titers of donor specific antibody (DSA) is decreased by iGE-Gel. In murine allogeneic transplantation, the injection of iGE-Gel significantly alleviated immune cell infiltration and complement damage in the graft, preserved the structure and function of renal cells and prolonged recipient survival period from 30.8 to 79.3 days, highlighting the potential of iGE-Gel as a transformative treatment in allotransplant.

Chimeric antigen receptor T-cell therapy in autoimmune diseases

The administration of T cells that have been modified to carry chimeric antigen receptors (CARs) aimed at B cells has been an effective strategy in treating B cell malignancies. This breakthrough has spurred the creation of CAR T cells intended to specifically reduce or alter the faulty immune responses associated with autoimmune disorders. Early positive outcomes from clinical trials involving CAR T cells that target the B cell protein CD19 in patients suffering from autoimmune diseases driven by B cells have been reported. Additional strategies are being developed to broaden the use of CAR T cell therapy and enhance its safety in autoimmune conditions. These include employing chimeric autoantireceptors (CAAR) to specifically eliminate B cells that are reactive to autoantigens, and using regulatory T cells (Tregs) engineered to carry antigen-specific CARs for precise immune modulation. This discussion emphasizes key factors such as choosing the right target cell groups, designing CAR constructs, defining tolerable side effects, and achieving a lasting immune modification, all of which are critical for safely integrating CAR T cell therapy in treating autoimmune diseases.

Chimeric antigen receptor T cell therapy for autoimmune disease

Infusion of T cells engineered to express chimeric antigen receptors (CARs) that target B cells has proven to be a successful treatment for B cell malignancies. This success inspired the development of CAR T cells to selectively deplete or modulate the aberrant immune responses that underlie autoimmune disease. Promising results are emerging from clinical trials of CAR T cells targeting the B cell protein CD19 in patients with B cell-driven autoimmune diseases. Further approaches are being designed to extend the application and improve safety of CAR T cell therapy in the setting of autoimmunity, including the use of chimeric autoantibody receptors to selectively deplete autoantigen-specific B cells and the use of regulatory T cells engineered to express antigen-specific CARs for targeted immune modulation. Here, we highlight important considerations, such as optimal target cell populations, CAR construct design, acceptable toxicities and potential for lasting immune reset, that will inform the eventual safe adoption of CAR T cell therapy for the treatment of autoimmune diseases.

CAR Treg synergy with anti-CD154 mediates infectious tolerance to dictate heart transplant outcomes

Successful allograft specific tolerance induction would eliminate the need for daily immunosuppression and improve post-transplant quality of life. Adoptive cell therapy with regulatory T cells expressing donor-specific Chimeric Antigen Receptors (CAR-Tregs) is a promising strategy, but as monotherapy, cannot prolong the survival with allografts with multiple MHC mismatches. Using an HLA-A2-transgenic haplo-mismatched heart transplantation model in immunocompetent C57Bl/6 recipients, we show that HLA-A2-specific (A2) CAR Tregs was able to synergize with low dose of anti-CD154 to enhance graft survival. Using haplo-mismatched grafts expressing the 2W-OVA transgene and tetramer-based tracking of 2W- and OVA-specific T cells, we showed that in mice with accepted grafts, A2.CAR Tregs inhibited endogenous non-A2 donor- specific T cell, B cell and antibody responses, and promoted a significant increase in endogenous FoxP3 + Tregs with indirect donor-specificity. By contrast, in mice where A2.CAR Tregs failed to prolong graft survival, FoxP3 neg A2.CAR T cells preferentially accumulated in rejecting allografts and endogenous donor-specific responses were not controlled. This study therefore provides the first evidence for synergy between A2.CAR Tregs and CD154 blockade to promote infectious tolerance in immunocompetent recipients of haplo-mismatched heart grafts and defines features of A2.CAR Tregs when they fail to reshape host immunity towards allograft tolerance.

Regulatory T cell-based therapy in type 1 diabetes: Latest breakthroughs and evidence

Autoimmune diseases (ADs) are among the most significant health complications, with their incidence rising in recent years. Type 1 diabetes (T1D), an AD, targets the insulin-producing β cells in the pancreas, leading to chronic insulin deficiency in genetically susceptible individuals. Regulatory immune cells, particularly T-cells (Tregs), have been shown to play a crucial role in the pathogenesis of diabetes by modulating immune responses. In diabetic patients, Tregs often exhibit diminished effectiveness due to various factors, such as instability in forkhead box P3 (Foxp3) expression or abnormal production of the proinflammatory cytokine interferon-gamma (IFN-γ) by autoreactive T-cells. Consequently, Tregs represent a potential therapeutic target for diabetes treatment. Building on the successful clinical outcomes of chimeric antigen receptor (CAR) T-cell therapy in cancer treatment, particularly in leukemias, the concept of designing and utilizing CAR Tregs for ADs has emerged. This review summarizes the findings on Treg targeting in T1D and discusses the benefits and limitations of this treatment approach for patients suffering from T1D.

Application of chimeric antigen receptor therapy beyond oncology: A bibliometric and visualized analysis

PURPOSE

Chimeric antigen receptor therapy beyond oncology has gained increasing attention. While a substantial number of publications have emerged in recent years, there has been a paucity of conducted bibliometric studies. Our objective is to systematically summarize and visually analyze the literature in the field of chimeric antigen receptors therapy beyond oncology and explore hotspots in this field.

METHODS

Web of Science Core Collection was selected as the data source, and the data was retrieved on December 23, 2022, according to the search strategy. CiteSpace 6.1.R6 and Vosviewer 1.6.18 were used to analyze publications and explore research hotspots and directions.

RESULTS

A total of 338 publications written by 1832 authors from 516 institutions in 42 countries/regions were selected for the analysis. The number of publications is steadily increasing annually. The United States emerged as the primary contributor, and University of Pennsylvania was the leading institution. Frontiers in Immunology boasted the highest number of published papers. Kitchen SG, Riley JL, and Scott DW were the most productive researchers in this field. The keyword cluster analysis identified HIV, autoimmune diseases, transplant related diseases and COVID-19 as the primary focus areas within the realm of chimeric antigen receptor therapy beyond oncology.

CONCLUSION

The advancement of chimeric antigen receptor therapy beyond oncology has witnessed rapid progress in recent years. We have explored the hotspots and research directions in this field. It is hoped that this study could provide references and directions for future clinical researches.

Graft-Specific Regulatory T Cells for Long-Lasting, Local Tolerance Induction

BACKGROUND

Solid organ transplantation is hindered by immune-mediated chronic graft dysfunction and the side effects of immunosuppressive therapy. Regulatory T cells (Tregs) are crucial for modulating immune responses post-transplantation; however, the transfer of polyspecific Tregs alone is insufficient to induce allotolerance in rodent models.

METHODS

To enhance the efficacy of adoptive Treg therapy, we investigated different immune interventions in the recipients. By utilizing an immunogenic skin transplant model and existing transplantation medicine reagents, we facilitated the clinical translation of our findings. Specifically, antigen-specific Tregs were used.

RESULTS

Our study demonstrated that combining the available induction therapies with drug-induced T-cell proliferation due to lymphopenia effectively increased the Treg/T effector ratios. This results in significant Treg accumulation within the graft, leading to long-term tolerance after the transfer of antigen-specific Tregs. Importantly, all the animals achieved operational tolerance, which boosted the presence of adoptively transferred Tregs within the graft.

CONCLUSIONS

This protocol offers a means to establish tolerance by utilizing antigen-specific Tregs. These results have promising implications for future trials involving adoptive Treg therapy in organ transplantation.

Integration of ζ-deficient CARs into the CD3ζ gene conveys potent cytotoxicity in T and NK cells

ABSTRACT

Chimeric antigen receptor (CAR)-redirected immune cells hold significant therapeutic potential for oncology, autoimmune diseases, transplant medicine, and infections. All approved CAR-T therapies rely on personalized manufacturing using undirected viral gene transfer, which results in nonphysiological regulation of CAR-signaling and limits their accessibility due to logistical challenges, high costs and biosafety requirements. Random gene transfer modalities pose a risk of malignant transformation by insertional mutagenesis. Here, we propose a novel approach utilizing CRISPR-Cas gene editing to redirect T cells and natural killer (NK) cells with CARs. By transferring shorter, truncated CAR-transgenes lacking a main activation domain into the human CD3ζ (CD247) gene, functional CAR fusion-genes are generated that exploit the endogenous CD3ζ gene as the CAR's activation domain. Repurposing this T/NK-cell lineage gene facilitated physiological regulation of CAR expression and redirection of various immune cell types, including conventional T cells, TCRγ/δ T cells, regulatory T cells, and NK cells. In T cells, CD3ζ in-frame fusion eliminated TCR surface expression, reducing the risk of graft-versus-host disease in allogeneic off-the-shelf settings. CD3ζ-CD19-CAR-T cells exhibited comparable leukemia control to TCRα chain constant (TRAC)-replaced and lentivirus-transduced CAR-T cells in vivo. Tuning of CD3ζ-CAR-expression levels significantly improved the in vivo efficacy. Notably, CD3ζ gene editing enabled redirection of NK cells without impairing their canonical functions. Thus, CD3ζ gene editing is a promising platform for the development of allogeneic off-the-shelf cell therapies using redirected killer lymphocytes.

Dawn of CAR-T cell therapy in autoimmune diseases

ABSTRACT

Chimeric antigen receptor (CAR)-T cell therapy has achieved remarkable success in the treatment of hematological malignancies. Based on the immunomodulatory capability of CAR-T cells, efforts have turned toward exploring their potential in treating autoimmune diseases. Bibliometric analysis of 210 records from 128 academic journals published by 372 institutions in 40 countries/regions indicates a growing number of publications on CAR-T therapy for autoimmune diseases, covering a range of subtypes such as systemic lupus erythematosus, multiple sclerosis, among others. CAR-T therapy holds promise in mitigating several shortcomings, including the indiscriminate suppression of the immune system by traditional immunosuppressants, and non-sustaining therapeutic levels of monoclonal antibodies due to inherent pharmacokinetic constraints. By persisting and proliferating in vivo , CAR-T cells can offer a tailored and precise therapeutics. This paper reviewed preclinical experiments and clinical trials involving CAR-T and CAR-related therapies in various autoimmune diseases, incorporating innovations well-studied in the field of hematological tumors, aiming to explore a safe and effective therapeutic option for relapsed/refractory autoimmune diseases.

Combining Treg Therapy With Donor Bone Marrow Transplantation: Experimental Progress and Clinical Perspective

Donor-specific tolerance remains a goal in transplantation because it could improve graft survival and reduce morbidity. Cotransplantation of donor hematopoietic cells to achieve chimerism is a promising approach for tolerance induction, which was successfully tested in clinical trials. However, current protocols are associated with side effects related to the myelosuppressive recipient conditioning, which makes it difficult to introduce them as standard therapy. More recently, adoptive cell therapy with polyclonal or donor-specific regulatory T cells (Treg) proved safe and feasible in several transplant trials, but it is unclear whether it can induce tolerance on its own. The combination of both approaches-Treg therapy and hematopoietic cell transplantation-leads to chimerism and tolerance without myelosuppressive treatment in murine models. Treg therapy promotes engraftment of allogeneic hematopoietic cells, reducing conditioning requirements and enhancing regulatory mechanisms maintaining tolerance. This review discusses possible modes of action of transferred Treg in experimental chimerism models and describes translational efforts investigating the potent synergy of Treg and chimerism.

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.

Immune modulation in transplant medicine: a comprehensive review of cell therapy applications and future directions

Balancing the immune response after solid organ transplantation (SOT) and vascularized composite allotransplantation (VCA) remains an ongoing clinical challenge. While immunosuppressants can effectively reduce acute rejection rates following transplant surgery, some patients still experience recurrent acute rejection episodes, which in turn may progress to chronic rejection. Furthermore, these immunosuppressive regimens are associated with an increased risk of malignancies and metabolic disorders. Despite significant advancements in the field, these IS related side effects persist as clinical hurdles, emphasizing the need for innovative therapeutic strategies to improve transplant survival and longevity. Cellular therapy, a novel therapeutic approach, has emerged as a potential pathway to promote immune tolerance while minimizing systemic side-effects of standard IS regiments. Various cell types, including chimeric antigen receptor T cells (CAR-T), mesenchymal stromal cells (MSCs), regulatory myeloid cells (RMCs) and regulatory T cells (Tregs), offer unique immunomodulatory properties that may help achieve improved outcomes in transplant patients. This review aims to elucidate the role of cellular therapies, particularly MSCs, T cells, Tregs, RMCs, macrophages, and dendritic cells in SOT and VCA. We explore the immunological features of each cell type, their capacity for immune regulation, and the prospective advantages and obstacles linked to their application in transplant patients. An in-depth outline of the current state of the technology may help SOT and VCA providers refine their perioperative treatment strategies while laying the foundation for further trials that investigate cellular therapeutics in transplantation surgery.

High affinity chimeric antigen receptor signaling induces an inflammatory program in human regulatory T cells

Regulatory T cells (Tregs) are promising cellular therapies to induce immune tolerance in organ transplantation and autoimmune disease. The success of chimeric antigen receptor (CAR) T-cell therapy for cancer has sparked interest in using CARs to generate antigen-specific Tregs. Here, we compared CAR with endogenous T cell receptor (TCR)/CD28 activation in human Tregs. Strikingly, CAR Tregs displayed increased cytotoxicity and diminished suppression of antigen-presenting cells and effector T (Teff) cells compared with TCR/CD28 activated Tregs. RNA sequencing revealed that CAR Tregs activate Teff cell gene programs. Indeed, CAR Tregs secreted high levels of inflammatory cytokines, with a subset of FOXP3+ CAR Tregs uniquely acquiring CD40L surface expression and producing IFNγ. Interestingly, decreasing CAR antigen affinity reduced Teff cell gene expression and inflammatory cytokine production by CAR Tregs. Our findings showcase the impact of engineered receptor activation on Treg biology and support tailoring CAR constructs to Tregs for maximal therapeutic efficacy.

Engineered Treg cells: The heir to the throne of immunotherapy

Recently, increased interest in the use of Tregs as adoptive cell therapy for the treatment of autoimmune diseases and transplant rejection had led to several advances in the field. However, Treg cell therapies, while constantly advancing, indiscriminately suppress the immune system without the permanent stabilization of certain diseases. Genetically modified Tregs hold great promise towards solving these problems, but, challenges in identifying the most potent Treg subtype, accompanied by the ambiguity involved in identifying the optimal Treg source, along with its expansion and engineering in a clinical-grade setting remain paramount. This review highlights the recent advances in methodologies for the development of genetically engineered Treg cell-based treatments for autoimmune, inflammatory diseases, and organ rejection. Additionally, it provides a systematized guide to all the recent progress in the field and informs the readers of the feasibility and safety of engineered adoptive Treg cell therapy, with the aim to provide a framework for researchers involved in the development of engineered Tregs.

Chimeric Antigen Receptor (CAR)-Based Cell Therapy for Type 1 Diabetes Mellitus (T1DM); Current Progress and Future Approaches

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that destroys insulin-producing pancreatic β-cells. Insulin replacement therapy is currently the mainstay of treatment for T1DM; however, treatment with insulin does not ameliorate disease progression, as dysregulated immune response and inflammation continue to cause further pancreatic β-cell degradation. Therefore, shifting therapeutic strategies toward immunomodulating approaches could be effective to prevent and reverse disease progression. Different immune-modulatory therapies could be used, e.g., monoclonal-based immunotherapy, mesenchymal stem cell, and immune cell therapy. Since immune-modulatory approaches could have a systemic effect on the immune system and cause toxicity, more specific treatment options should target the immune response against pancreatic β-cells. In this regard, chimeric antigen receptor (CAR)-based immunotherapy could be a promising candidate for modulation of dysregulated immune function in T1DM. CAR-based therapy has previously been approved for a number of hematologic malignancies. Nevertheless, there is renewed interest in CAR T cells' " off-the-shelf " treatment for T1DM. Several pre-clinical studies demonstrated that redirecting antigen-specific CAR T cells, especially regulatory CAR T cells (CAR Tregs), toward the pancreatic β-cells, could prevent diabetes onset and progression in diabetic mice models. Here, we aim to review the current progress of CAR-based immune-cell therapy for T1DM and the corresponding challenges, with a special focus on designing CAR-based immunomodulatory strategies to improve its efficacy in the treatment of T1DM.

Cellular Strategies for Separating GvHD from GvL in Haploidentical Transplantation

GvHD still remains, despite the continuous improvement of transplantation platforms, a fearful complication of transplantation from allogeneic donors. Being able to separate GvHD from GvL represents the greatest challenge in the allogeneic transplant setting. This may be possible through continuous improvement of cell therapy techniques. In this review, current cell therapies are taken into consideration, which are based on the use of TCR alpha/beta depletion, CD45RA depletion, T regulatory cell enrichment, NK-cell-based immunotherapies, and suicide gene therapies in order to prevent GvHD and maximally amplify the GvL effect in the setting of haploidentical transplantation.

Chimeric antigen receptor Treg therapy in transplantation

In the quest for more precise and effective organ transplantation therapies, chimeric antigen receptor (CAR) regulatory T cell (Treg) therapies represent a potential cutting-edge advance. This review comprehensively analyses CAR Tregs and how they may address important drawbacks of polyclonal Tregs and conventional immunosuppressants. We examine a growing body of preclinical findings of CAR Treg therapy in transplantation, discuss CAR Treg design specifics, and explore established and attractive new targets in transplantation. In addition, we explore present impediments where future studies will be necessary to determine the efficacy of CAR Tregs in reshaping alloimmune responses and transplant microenvironments to reduce reliance on chemical immunosuppressants. Overall, ongoing studies and trials are crucial for understanding the full scope of CAR Treg therapy in transplantation.

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.

Elucidating the neuroimmunology of traumatic brain injury: methodological approaches to unravel intercellular communication and function

The neuroimmunology of traumatic brain injury (TBI) has recently gained recognition as a crucial element in the secondary pathophysiological consequences that occur following neurotrauma. Both immune cells residing within the central nervous system (CNS) and those migrating from the periphery play significant roles in the development of secondary brain injury. However, the precise mechanisms governing communication between innate and adaptive immune cells remain incompletely understood, partly due to a limited utilization of relevant experimental models and techniques. Therefore, in this discussion, we outline current methodologies that can aid in the exploration of TBI neuroimmunology, with a particular emphasis on the interactions between resident neuroglial cells and recruited lymphocytes. These techniques encompass adoptive cell transfer, intra-CNS injection(s), selective cellular depletion, genetic manipulation, molecular neuroimaging, as well as in vitro co-culture systems and the utilization of organoid models. By incorporating key elements of both innate and adaptive immunity, these methods facilitate the examination of clinically relevant interactions. In addition to these preclinical approaches, we also detail an emerging avenue of research that seeks to leverage human biofluids. This approach enables the investigation of how resident and infiltrating immune cells modulate neuroglial responses after TBI. Considering the growing significance of neuroinflammation in TBI, the introduction and application of advanced methodologies will be pivotal in advancing translational research in this field.

Induction of long-term tolerance to a specific antigen using anti-CD3 lipid nanoparticles following gene therapy

Development of factor VIII (FVIII) inhibitors is a serious complication in the treatment of hemophilia A (HemA) patients. In clinical trials, anti-CD3 antibody therapy effectively modulates the immune response of allograft rejection or autoimmune diseases without eliciting major adverse effects. In this study, we delivered mRNA-encapsulated lipid nanoparticles (LNPs) encoding therapeutic anti-CD3 antibody (αCD3 LNPs) to overcome the anti-FVIII immune responses in HemA mice. It was found that αCD3 LNPs encoding the single-chain antibodies (Fc-scFv) can efficiently deplete CD3+ and CD4+ effector T cells, whereas αCD3 LNPs encoding double-chain antibodies cannot. Concomitantly, mice treated with αCD3 (Fc-scFv) LNPs showed an increase in the CD4+CD25+Foxp3+ regulatory T cell percentages, which modulated the anti-FVIII immune responses. All T cells returned to normal levels within 2 months. HemA mice treated with αCD3 LNPs prior to hydrodynamic injection of liver-specific FVIII plasmids achieved persistent FVIII gene expression without formation of FVIII inhibitors. Furthermore, transgene expression was increased and persistent following secondary plasmid challenge, indicating induction of long-term tolerance to FVIII. Moreover, the treated mice maintained their immune competence against other antigens. In conclusion, our study established a potential new strategy to induce long-term antigen-specific tolerance using an αCD3 LNP formulation.

Human HLA-DR+CD27+ regulatory T cells show enhanced antigen-specific suppressive function

Regulatory T cells (Tregs) have potential for the treatment of autoimmune diseases and graft rejection. Antigen specificity and functional stability are considered critical for their therapeutic efficacy. In this study, expansion of human Tregs in the presence of porcine PBMCs (xenoantigen-expanded Tregs, Xn-Treg) allowed the selection of a distinct Treg subset, coexpressing the activation/memory surface markers HLA-DR and CD27 with enhanced proportion of FOXP3+Helios+ Tregs. Compared with their unsorted and HLA-DR+CD27+ double-positive (DP) cell-depleted Xn-Treg counterparts, HLA-DR+CD27+ DP-enriched Xn-Tregs expressed upregulated Treg function markers CD95 and ICOS with enhanced suppression of xenogeneic but not polyclonal mixed lymphocyte reaction. They also had less Treg-specific demethylation in the region of FOXP3 and were more resistant to conversion to effector cells under inflammatory conditions. Adoptive transfer of porcine islet recipient NOD/SCID IL2 receptor γ-/- mice with HLA-DR+CD27+ DP-enriched Xn-Tregs in a humanized mouse model inhibited porcine islet graft rejection mediated by 25-fold more human effector cells. The prolonged graft survival was associated with enhanced accumulation of FOXP3+ Tregs and upregulated expression of Treg functional genes, IL10 and cytotoxic T lymphocyte antigen 4, but downregulated expression of effector Th1, Th2, and Th17 cytokine genes, within surviving grafts. Collectively, human HLA-DR+CD27+ DP-enriched Xn-Tregs expressed a specific regulatory signature that enabled identification and isolation of antigen-specific and functionally stable Tregs with potential as a Treg-based therapy.

Chimerism-based Tolerance Induction in Clinical Transplantation: Its Foundations and Mechanisms

Hematopoietic chimerism remains the most promising strategy to bring transplantation tolerance into clinical routine. The concept of chimerism-based tolerance aims to extend the recipient's mechanisms of self-tolerance (ie, clonal deletion, anergy, and regulation) to include the tolerization of donor antigens that are introduced through the cotransplantation of donor hematopoietic cells. For this to be successful, donor hematopoietic cells need to engraft in the recipient at least temporarily. Three pioneering clinical trials inducing chimerism-based tolerance in kidney transplantation have been published to date. Within this review, we discuss the mechanisms of tolerance that are associated with the specific therapeutic protocols of each trial. Recent data highlight the importance of regulation as a mechanism that maintains tolerance. Insufficient regulatory mechanisms are also a likely explanation for situations of tolerance failure despite persisting donor chimerism. After decades of preclinical development of chimerism protocols, mechanistic data from clinical trials have recently become increasingly important. Better understanding of the required mechanisms for tolerance to be induced in humans will be a key to design more reliable and less invasive chimerism protocols in the future.

Immunoregulation: the interplay between metabolism and redox homeostasis

Regulatory T cells are fundamental for the induction and maintenance of immune homeostasis, with their dysfunction resulting in uncontrolled immune responses and tissue destruction predisposing to autoimmunity, transplant rejection and several inflammatory and metabolic disorders. Recent discoveries have demonstrated that metabolic processes and mitochondrial function are critical for the appropriate functioning of these cells in health, with their metabolic adaptation, influenced by microenvironmental factors, seen in several pathological processes. Upon activation regulatory T cells rearrange their oxidation-reduction (redox) system, which in turn supports their metabolic reprogramming, adding a layer of complexity to our understanding of cellular metabolism. Here we review the literature surrounding redox homeostasis and metabolism of regulatory T cells to highlight new mechanistic insights of these interlinked pathways in immune regulation.

Intragraft regulatory T cells in the modern era: what can high-dimensional methods tell us about pathways to allograft acceptance?

Replacement of diseased organs with transplanted healthy donor ones remains the best and often only treatment option for end-stage organ disease. Immunosuppressants have decreased the incidence of acute rejection, but long-term survival remains limited. The broad action of current immunosuppressive drugs results in global immune impairment, increasing the risk of cancer and infections. Hence, achievement of allograft tolerance, in which graft function is maintained in the absence of global immunosuppression, has long been the aim of transplant clinicians and scientists. Regulatory T cells (Treg) are a specialized subset of immune cells that control a diverse array of immune responses, can prevent allograft rejection in animals, and have recently been explored in early phase clinical trials as an adoptive cellular therapy in transplant recipients. It has been established that allograft residency by Tregs can promote graft acceptance, but whether intragraft Treg functional diversification and spatial organization contribute to this process is largely unknown. In this review, we will explore what is known regarding the properties of intragraft Tregs during allograft acceptance and rejection. We will summarize recent advances in understanding Treg tissue residency through spatial, transcriptomic and high-dimensional cytometric methods in both animal and human studies. Our discussion will explore properties of intragraft Tregs in mediating operational tolerance to commonly transplanted solid organs. Finally, given recent developments in Treg cellular therapy, we will review emerging knowledge of whether and how these adoptively transferred cells enter allografts in humans. An understanding of the properties of intragraft Tregs will help lay the foundation for future therapies that will promote immune tolerance.

Integration of ζ-deficient CARs into the CD3-zeta gene conveys potent cytotoxicity in T and NK cells

Chimeric antigen receptor (CAR)-reprogrammed immune cells hold significant therapeutic potential for oncology, autoimmune diseases, transplant medicine, and infections. All approved CAR-T therapies rely on personalized manufacturing using undirected viral gene transfer, which results in non-physiological regulation of CAR-signaling and limits their accessibility due to logistical challenges, high costs and biosafety requirements. Here, we propose a novel approach utilizing CRISPR-Cas gene editing to redirect T cells and natural killer (NK) cells with CARs. By transferring shorter, truncated CAR-transgenes lacking a main activation domain into the human CD3 ζ (CD247) gene, functional CAR fusion-genes are generated that exploit the endogenous CD3 ζ gene as the CAR's activation domain. Repurposing this T/NK-cell lineage gene facilitated physiological regulation of CAR-expression and reprogramming of various immune cell types, including conventional T cells, TCRγ/δ T cells, regulatory T cells, and NK cells. In T cells, CD3 ζ in-frame fusion eliminated TCR surface expression, reducing the risk of graft-versus-host disease in allogeneic off-the-shelf settings. CD3 ζ-CD19-CAR-T cells exhibited comparable leukemia control to T cell receptor alpha constant ( TRAC )-replaced and lentivirus-transduced CAR-T cells in vivo . Tuning of CD3 ζ-CAR-expression levels significantly improved the in vivo efficacy. Compared to TRAC -edited CAR-T cells, integration of a Her2-CAR into CD3 ζ conveyed similar in vitro tumor lysis but reduced susceptibility to activation-induced cell death and differentiation, presumably due to lower CAR-expression levels. Notably, CD3 ζ gene editing enabled reprogramming of NK cells without impairing their canonical functions. Thus, CD3 ζ gene editing is a promising platform for the development of allogeneic off-the-shelf cell therapies using redirected killer lymphocytes.

Key points

Integration of ζ-deficient CARs into CD3 ζ gene allows generation of functional TCR-ablated CAR-T cells for allogeneic off-the-shelf use CD3 ζ-editing platform allows CAR reprogramming of NK cells without affecting their canonical functions.

Emerging cellular and immunotherapies for systemic sclerosis: from mesenchymal stromal cells to CAR-T cells and vaccine-based approaches

PURPOSE OF REVIEW

Although two targeted therapies have received recent approval for systemic sclerosis (SSc)-associated interstitial lung disease, they do not show major disease-modifying activity, highlighting the need for novel therapies and innovative paradigms. To that end, cellular therapies may represent a new opportunity for the treatment of SSc. The purpose of this review is to provide an up-to-date overview of emerging cell-based disease-modifying therapies in SSc.

RECENT FINDINGS

Initial small studies in patients with severe refractory systemic lupus erythematosus (SLE) using engineered regulatory cells show promising results. CD19-directed CAR-T have shown promising results in one case report of refractory diffuse cutaneous SSc patients. T cells engineered to express a chimeric autoantibody receptor (CAAR-T cells) may be even more relevant via the specific elimination of auto-reactive B cells. Targeting pro-fibrotic or senescence-related pathways may also constitute promising approaches in SSc.

SUMMARY

Building on the classification of the clinical phenotype and prediction of clinical trajectory based on individual patients' autoantigen and/or autoantibody profile, cellular therapies targeting the same autoantigen or related autoreactive cells may represent an unprecedented opportunity to implement personalized medicine in SSc.

Advanced Materials and Delivery Systems for Enhancement of Chimeric Antigen Receptor Cells

Chimeric antigen receptor (CAR) cell therapy is a great success and breakthrough in immunotherapy. However, there are still lots of barriers to its wide use in clinical, including long time consumption, high cost, and failure against solid tumors. For these challenges, researches are deplored to explore CAR cells to more appliable products in clinical. This minireview focuses on the advanced non-viral materials for CAR-T transfection ex vivo with better performance, delivery systems combined with other therapy for enhancement of CAR-T therapy in solid tumors. In addition, the targeted delivery platform for CAR cells in vivo generation as a breakthrough technology as its low cost and convenience. In the end, the prospective direction and future of CAR cell therapy are discussed.

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.

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.

Chimeric HLA antibody receptor T cells to target HLA-specific B cells in solid organ transplantation

HLA-sensitized patients on the transplant waiting list harbor antibodies and memory B cells directed against allogeneic HLA molecules, which decreases the chance to receive a compatible donor organ. Current desensitization strategies non-specifically target circulating antibodies and B cells, warranting the development of therapies that specifically affect HLA-directed humoral immune responses. We developed Chimeric HLA Antibody Receptor (CHAR) constructs comprising the extracellular part of HLA-A2 or HLA-A3 coupled to CD28-CD3ζ domains. CHAR-transduced cells expressing reporter constructs encoding T-cell activation markers, and CHAR-transduced CD8+ T cells from healthy donors were stimulated with HLA-specific monoclonal antibody-coated microbeads, and HLA-specific B cell hybridomas. CHAR T cell activation was measured by upregulation of T cell activation markers and IFNγ secretion, whereas CHAR T cell killing of B cell hybridomas was assessed in chromium release assays and by IgG ELISpot. HLA-A2- and HLA-A3-CHAR expressing cells were specifically activated by HLA-A2- and HLA-A3-specific monoclonal antibodies, either soluble or coated on microbeads, as shown by CHAR-induced transcription factors. HLA-A2 and HLA-A3 CHAR T cells efficiently produced IFNγ with exquisite specificity and were capable of specifically lysing hybridoma cells expressing HLA-A2- or HLA-A3-specific B-cell receptors, respectively. Finally, we mutated the α3 domain of the CHAR molecules to minimize any alloreactive T-cell reactivity against CHAR T cells, while retaining CHAR activity. These data show proof of principle for CHAR T cells to serve as precision immunotherapy to specifically desensitize (highly) sensitized solid organ transplant candidates and to treat antibody-mediated rejection after solid organ transplantation.