Ectopic FOXP3 Expression in Combination with TGF-β1 and IL-2 Stimulation Generates Limited Suppressive Function in Human Primary Activated Thymocytes Ex Vivo

Extracorporeal photopheresis as a promising strategy for the treatment of graft-versus-host disease after CAR T-cell therapy

ABSTRACT

Graft-versus-host disease (GVHD) occurs in about 10% to 33% of patients receiving "allogeneic" or "autologous" chimeric antigen receptor T (CAR-T) cells after preceding allogeneic hematopoietic stem cell transplantation (allo-HSCT) due to the substantial presence of alloreactive T cells. Extracorporeal photopheresis (ECP) shows promising clinical outcomes in the treatment of GVHD after allo-HSCT without hampering antitumor and antiviral effects. This raises an interesting question: whether ECP might constitute a new way to treat patients with GVHD after CAR T-cell therapy without compromising CAR-T cells significantly. Third-generation CD19-specific CAR-T cells were generated and an in vitro ECP protocol was established. The impact of ECP on CAR-T cells was comprehensively investigated in 2 models: the nondilution model reflects days after CAR T-cell infusion and the dilution model weeks after infusion. The therapeutic effect of ECP on GVHD was examined in an in vitro mixed lymphocyte reaction (MLR) assay. We found, ECP-treated CAR-T cells demonstrated reduced potency in inducing alloreaction compared with that of the group without ECP treatment in MLR assay. ECP could selectively induce apoptosis, thereby enriching the naive and central memory CAR-T cells with a reduced alloreactivity. The cytokine milieu of CAR-T cells could be switched from immune stimulation to immune tolerance in both models. Moreover, ECP could modulate the proliferative capacity of CAR-T cells without hampering their long-term functionality in the dilution model. In conclusion, ECP constitutes a promising treatment strategy for GVHD after allo-HSCT and CAR T-cell transfusion, as ECP reduces the alloreactivity without hampering CAR T-cell functionality.

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.

CAR-Treg cell therapies and their future potential in treating ocular autoimmune conditions

Ophthalmic autoimmune and autoinflammatory conditions cause significant visual morbidity and require complex medical treatment complicated by significant side effects and lack of specificity. Regulatory T cells (Tregs) have key roles in immune homeostasis and in the resolution of immune responses. Polyclonal Treg therapy has shown efficacy in treating autoimmune disease. Genetic engineering approaches to produce antigen-specific Treg therapy has the potential for enhanced treatment responses and fewer systemic side effects. Cell therapy using chimeric antigen receptor modified T cell (CAR-T) therapy, has had significant success in treating haematological malignancies. By modifying Tregs specifically, a CAR-Treg approach has been efficacious in preclinical models of autoimmune conditions leading to current phase 1-2 clinical trials. This review summarises CAR structure and design, Treg cellular biology, developments in CAR-Treg therapies, and discusses future strategies to apply CAR-Treg therapy in the treatment of ophthalmic conditions.

Treg-targeted efficient-inducible platform for collagen-induced arthritis treatment

Regulatory T cells (Tregs) display great promise in rheumatoid arthritis (RA) therapy. However, their low number and differentiation rate limit their further application in the clinics. In the present study, we first optimized a combination of IL-2, TGF-β and cyclin dependent kinase inhibitor AS2863619 (IL-2/TGF-β/AS), which could induce Tregs with high efficiency in vitro. After the induced Tregs (iTregs) were confirmed to suppress lymphocyte proliferation and pro-inflammatory T help cells (Th1 and Th17) activation, a chitosan-stabilized nanoparticle drug delivery system (NDDS) was developed according to the optimized formula of IL-2/TGF-β/AS. In vivo study, the NDDS was injected into the knees of mice with collagen-induced arthritis (CIA). As a result, the NDDS remarkably reduced the pathological score of the CIA, alleviated the inflammatory cell infiltration and synovial hyperplasia, and minimized cartilage tissue damage in the knee joint of the CIA mice. Mechanically, the NDDS administration promoted Treg differentiation and decreased Th17 production, consequently reversing the ratio of Treg/Th17, and reducing the secretion of TNF-α in the sera, which facilitated to relieve the severity and progression of arthritis. In sum, NDDS capable of efficiently inducing Tregs were constructed successfully and provided a potential platform for treating RA by restoring the equilibrium of Treg/Th17 destroyed in RA.

Do Treg Speed Up with CARs? Chimeric Antigen Receptor Treg Engineered to Induce Transplant Tolerance

Adoptive transfer of regulatory T cells (Treg) can induce transplant tolerance in preclinical models by suppressing alloantigen-directed inflammatory responses; clinical translation was so far hampered by the low abundance of Treg with allo-specificity in the peripheral blood. In this situation, ex vivo engineering of Treg with a T-cell receptor (TCR) or chimeric antigen receptor (CAR) provides a cell population with predefined specificity that can be amplified and administered to the patient. In contrast to TCR-engineered Treg, CAR Treg can be redirected toward a broad panel of targets in an HLA-unrestricted fashion' making these cells attractive to provide antigen-specific tolerance toward the transplanted organ. In preclinical models, CAR Treg accumulate and amplify at the targeted transplant, maintain their differentiated phenotype, and execute immune repression more vigorously than polyclonal Treg. With that, CAR Treg are providing hope in establishing allospecific, localized immune tolerance in the long term' and the first clinical trials administering CAR Treg for the treatment of transplant rejection are initiated. Here, we review the current platforms for developing and manufacturing alloantigen-specific CAR Treg and discuss the therapeutic potential and current hurdles in translating CAR Treg into clinical exploration.

Roles of TGF-β in cancer hallmarks and emerging onco-therapeutic design

Transforming growth factor-beta (TGF-β) is a double-edged sword in cancer treatment because of its pivotal yet complex and roles played during cancer initiation/development. Current anti-cancer strategies involving TGF-β largely view TGF-β as an onco-therapeutic target that not only substantially hinders its full utilisation for cancer control, but also considerably restricts innovations in this field. Thereby, how to take advantages of therapeutically favourable properties of TGF-β for cancer management represents an interesting and less investigated problem. Here, by categorising cancer hallmarks into four critical transition events and one enabling characteristic controlling cancer initiation and progression, and delineating TGF-β complexities according to these cancer traits, we identify the suppressive role of TGF-β in tumour initiation and early-stage progression and its promotive functionalities in cancer metastasis as well as other cancer hallmarks. We also propose the feasibility and possible scenarios of combining cold atmospheric plasma (CAP) with onco-therapeutics utilising TGF-β for cancer control given the intrinsic properties of CAP against cancer hallmarks.