Challenges in cryopreservation of regulatory T cells (Tregs) for clinical therapeutic applications

Globular Antifreeze Protein-Inspired Nanoparticle-Based Large-Scale T-Cell Cryoprotection System for Lymphoma Immunotherapy

Large-scale biosafe T-cell cryopreservation is required to bring T-cell therapies to the market, but it remains challenging due to the cytotoxicity of common cryoprotectants [e.g., dimethyl sulfoxide (DMSO)] and unavoidable ice injuries to cells. Herein, inspired by natural globular antifreeze proteins, we establish a biocompatible zwitterionic magnetic nanoparticle (ZMNP)-based cryoprotection system, achieving large-scale cryopreservation of T cells for lymphoma immunotherapy. ZMNPs could form a globular hydration shell to inhibit water molecule aggregation as well as ice growth, and the surficial hydration strength-antifreeze performance relationship of ZMNPs was investigated. During the thawing process, ZMNPs possessed a magnetic field-mediated nanowarming property that enabled rapid heating and also facilitated easy magnetic separation for cell recovery. These combined effects resulted in a high post-thaw viability (>80%) of large-scale T-cell cryopreservation (20 mL). Notably, post-thaw T cells exhibited similar transcript profiles to fresh cells, while up- or downregulation of 1050 genes was found in the DMSO group. In a mouse E.G7-OVA lymphoma model, ZMNP-system-cryopreserved T cells achieved a tumor suppression rate of 77.5%, twice as high as the DMSO group. This work holds great promise for the application of advanced cryopreservation techniques in the development of therapeutic cellular products.

Biomaterial-enhanced treg cell immunotherapy: A promising approach for transplant medicine and autoimmune disease treatment

Regulatory T cells (Tregs) are crucial for preserving tolerance in the body, rendering Treg immunotherapy a promising treatment option for both organ transplants and autoimmune diseases. Presently, organ transplant recipients must undergo lifelong immunosuppression to prevent allograft rejection, while autoimmune disorders lack definitive cures. In the last years, there has been notable advancement in comprehending the biology of both antigen-specific and polyclonal Tregs. Clinical trials involving Tregs have demonstrated their safety and effectiveness. To maximize the efficacy of Treg immunotherapy, it is essential for these cells to migrate to specific target tissues, maintain stability within local organs, bolster their suppressive capabilities, and ensure their intended function's longevity. In pursuit of these goals, the utilization of biomaterials emerges as an attractive supportive strategy for Treg immunotherapy in addressing these challenges. As a result, the prospect of employing biomaterial-enhanced Treg immunotherapy holds tremendous promise as a treatment option for organ transplant recipients and individuals grappling with autoimmune diseases in the near future. This paper introduces strategies based on biomaterial-assisted Treg immunotherapy to enhance transplant medicine and autoimmune treatments.

Pros and Cons of Cryopreserving Allogeneic Stem Cell Products

The COVID-19 pandemic has precipitously changed the practice of transplanting fresh allografts. The safety measures adopted during the pandemic prompted the near-universal graft cryopreservation. However, the influence of cryopreserving allogeneic grafts on long-term transplant outcomes has emerged only in the most recent literature. In this review, the basic principles of cell cryopreservation are revised and the effects of cryopreservation on the different graft components are carefully reexamined. Finally, a literature revision on studies comparing transplant outcomes in patients receiving cryopreserved and fresh grafts is illustrated.

Regulatory T cells (Tregs) and their therapeutic potential against autoimmune disorders - Advances and challenges

Autoimmune diseases are caused when immune cells act against self-protein. This biological self-non-self-discrimination phenomenon is controlled by a distinct group of lymphocytes known as regulatory T cells (Tregs), which are key inflammatory response regulators and play a pivotal role in immune tolerance and homeostasis. Treg-mediated robust immunosuppression provides self-tolerance and protection against autoimmune diseases. However, once this system fails to operate or poorly operate, it leads to an extreme situation where immune system reacts against self-antigens and destroys host organs, thus causing autoimmune diseases. Tregs can target both innate and adaptive immunity via modulating multiple immune cells such as neutrophils, monocytes, antigen-presenting cells, B cells, and T cells. This review highlights the Treg-mediated immunosuppression, role of several markers and their interplay during Treg development and differentiation, and advances in therapeutic aspects of Treg cells to reduce severity of autoimmunity-related conditions along with emphasizing limitations and challenges of their usages.

Distinct cellular dynamics associated with response to CAR-T therapy for refractory B cell lymphoma

Chimeric antigen receptor (CAR)-T cell therapy has revolutionized the treatment of hematologic malignancies. Approximately half of patients with refractory large B cell lymphomas achieve durable responses from CD19-targeting CAR-T treatment; however, failure mechanisms are identified in only a fraction of cases. To gain new insights into the basis of clinical response, we performed single-cell transcriptome sequencing of 105 pretreatment and post-treatment peripheral blood mononuclear cell samples, and infusion products collected from 32 individuals with large B cell lymphoma treated with either of two CD19 CAR-T products: axicabtagene ciloleucel (axi-cel) or tisagenlecleucel (tisa-cel). Expansion of proliferative memory-like CD8 clones was a hallmark of tisa-cel response, whereas axi-cel responders displayed more heterogeneous populations. Elevations in CAR-T regulatory cells among nonresponders to axi-cel were detected, and these populations were capable of suppressing conventional CAR-T cell expansion and driving late relapses in an in vivo model. Our analyses reveal the temporal dynamics of effective responses to CAR-T therapy, the distinct molecular phenotypes of CAR-T cells with differing designs, and the capacity for even small increases in CAR-T regulatory cells to drive relapse.

Untangling the Knots of Regulatory T Cell Therapy in Solid Organ Transplantation

Numerous preclinical studies have provided solid evidence supporting adoptive transfer of regulatory T cells (Tregs) to induce organ tolerance. As a result, there are 7 currently active Treg cell-based clinical trials in solid organ transplantation worldwide, all of which are early phase I or phase I/II trials. Although the results of these trials are optimistic and support both safety and feasibility, many experimental and clinical unanswered questions are slowing the progression of this new therapeutic alternative. In this review, we bring to the forefront the major challenges that Treg cell transplant investigators are currently facing, including the phenotypic and functional diversity of Treg cells, lineage stability, non-standardized ex vivo Treg cell manufacturing process, adequacy of administration route, inability of monitoring and tracking infused cells, and lack of biomarkers or validated surrogate endpoints of efficacy in clinical trials. With this plethora of interrogation marks, we are at a challenging and exciting crossroad where properly addressing these questions will determine the successful implementation of Treg cell-based immunotherapy in clinical transplantation.

Impact of Cryopreservation and Freeze-Thawing on Therapeutic Properties of Mesenchymal Stromal/Stem Cells and Other Common Cellular Therapeutics

Purpose of Review

Cryopreservation and its associated freezing and thawing procedures–short “freeze-thawing”–are among the final steps in economically viable manufacturing and clinical application of diverse cellular therapeutics. Translation from preclinical proof-of-concept studies to larger clinical trials has indicated that these processes may potentially present an Achilles heel to optimal cell product safety and particularly efficacy in clinical trials and routine use.

Recent Findings

We review the current state of the literature on how cryopreservation of cellular therapies has evolved and how the application of this technique to different cell types is interlinked with their ability to engraft and function upon transfer in vivo, in particular for hematopoietic stem and progenitor cells (HSPCs), their progeny, and therapeutic cell products derived thereof. We also discuss pros and cons how this may differ for non-hematopoietic mesenchymal stromal/stem cell (MSC) therapeutics. We present different avenues that may be crucial for cell therapy optimization, both, for hematopoietic (e.g., effector, regulatory, and chimeric antigen receptor (CAR)-modified T and NK cell based products) and for non-hematopoietic products, such as MSCs and induced pluripotent stem cells (iPSCs), to achieve optimal viability, recovery, effective cell dose, and functionality of the cryorecovered cells.

Summary

Targeted research into optimizing the cryopreservation and freeze-thawing routines and the adjunct manufacturing process design may provide crucial advantages to increase both the safety and efficacy of cellular therapeutics in clinical use and to enable effective market deployment strategies to become economically viable and sustainable medicines.

Improvement of bone marrow mononuclear cells cryopreservation methods to increase the efficiency of dendritic cell production

Cryopreservation is now considered an integral part of the biotechnological process, exploiting different types of cells and tissues in clinical practice. Among them, dendritic cells (DCs) deserve special attention, notably the immature tolerogenic cells (tolDCs), which provide natural tolerance in humans and animals. High cryolability of tolDCs has necessitated the search for the methods that would provide cryopreservation of their precursors; those more resistant to negative effects of cryopreservation factors, in particular, bone marrow or peripheral blood mononuclear cells (MNCs). Based on this, the aim of our research was to optimize the cryopreservation conditions for mice bone marrow MNCs with further assessment of their ability to form tolDCs ex vivo. A cryopreservation mode for bone marrow MNCs has been developed which provides structural and functional completeness of tolDCs obtained from them ex vivo. The ability of DCs derived from cryopreserved MNCs by the developed mode to induce T-regulatory (FOXP3⁺) cells in vitro when co-cultured with CD4⁺-lymphocytes was shown.Tolerogenic properties of the DCs derived from cryopreserved MNCs are implemented by increasing the content of hsp70 heat shock proteins and the expression rate of glucocorticoid-induced leucine zipper (GILZ). DCs with increased tolerogenic activities, obtained by the developed cryopreservation regimen, can be used in treatment of autoimmune diseases. In this research we not only evaluated the qualitative characteristics and tolerogenic activity of DCs produced in vitro from cryopreserved MNCs, but also outlined the prospects of accumulating their reserves in low-temperature banks for clinical use.

Assessment of the Impact of Post-Thaw Stress Pathway Modulation on Cell Recovery following Cryopreservation in a Hematopoietic Progenitor Cell Model

The development and use of complex cell-based products in clinical and discovery science continues to grow at an unprecedented pace. To this end, cryopreservation plays a critical role, serving as an enabling process, providing on-demand access to biological material, facilitating large scale production, storage, and distribution of living materials. Despite serving a critical role and substantial improvements over the last several decades, cryopreservation often remains a bottleneck impacting numerous areas including cell therapy, tissue engineering, and tissue banking. Studies have illustrated the impact and benefit of controlling cryopreservation-induced delayed-onset cell death (CIDOCD) through various “front end” strategies, such as specialized media, new cryoprotective agents, and molecular control during cryopreservation. While proving highly successful, a substantial level of cell death and loss of cell function remains associated with cryopreservation. Recently, we focused on developing technologies (RevitalICE™) designed to reduce the impact of CIDOCD through buffering the cell stress response during the post-thaw recovery phase in an effort to improve the recovery of previously cryopreserved samples. In this study, we investigated the impact of modulating apoptotic caspase activation, oxidative stress, unfolded protein response, and free radical damage in the initial 24 h post-thaw on overall cell survival. Human hematopoietic progenitor cells in vitro cryopreserved in both traditional extracellular-type and intracellular-type cryopreservation freeze media were utilized as a model cell system to assess impact on survival. Our findings demonstrated that through the modulation of several of these pathways, improvements in cell recovery were obtained, regardless of the freeze media and dimethyl sulfoxide concentration utilized. Specifically, through the use of oxidative stress inhibitors, an average increase of 20% in overall viability was observed. Furthermore, the results demonstrated that by using the post-thaw recovery reagent on samples cryopreserved in intracellular-type media (Unisol™), improvements in overall cell survival approaching 80% of non-frozen controls were attained. While improvements in overall survival were obtained, an assessment on the impact of specific cell subpopulations and functionality remains to be completed. While work remains, these results represent an important step forward in the development of improved cryopreservation processes for use in discovery science, and commercial and clinical settings.

Process development and validation of expanded regulatory T cells for prospective applications: an example of manufacturing a personalized advanced therapy medicinal product

BACKGROUND

A growing number of clinical trials have shown that regulatory T (Treg) cell transfer may have a favorable effect on the maintenance of self-tolerance and immune homeostasis in different conditions such as graft-versus-host disease (GvHD), solid organ transplantation, type 1 diabetes, and others. In this context, the availability of a robust manufacturing protocol that is able to produce a sufficient number of functional Treg cells represents a fundamental prerequisite for the success of a cell therapy clinical protocol. However, extended workflow guidelines for nonprofit manufacturers are currently lacking. Despite the fact that different successful manufacturing procedures and cell products with excellent safety profiles have been reported from early clinical trials, the selection and expansion protocols for Treg cells vary a lot. The objective of this study was to validate a Good Manufacturing Practice (GMP)-compliant protocol for the production of Treg cells that approaches the whole process with a risk-management methodology, from process design to completion of final product development. High emphasis was given to the description of the quality control (QC) methodologies used for the in-process and release tests (sterility, endotoxin test, mycoplasma, and immunophenotype).

RESULTS

The GMP-compliant protocol defined in this work allows at least 4.11 × 109 Treg cells to be obtained with an average purity of 95.75 ± 4.38% and can be used in different clinical settings to exploit Treg cell immunomodulatory function.

CONCLUSIONS

These results could be of great use for facilities implementing GMP-compliant cell therapy protocols of these cells for different conditions aimed at restoring the Treg cell number and function, which may slow the progression of certain diseases.

Freezing Medium Containing 5% DMSO Enhances the Cell Viability and Recovery Rate After Cryopreservation of Regulatory T Cell Products ex vivo and in vivo

Cell therapies have significant therapeutic potential in diverse fields including regenerative medicine, transplantation tolerance, and autoimmunity. Within these fields, regulatory T cells (Treg) have been deployed to ameliorate aberrant immune responses with great success. However, translation of the cryopreservation strategies employed for other cell therapy products, such as effector T cell therapies, to Treg therapies has been challenging. The lack of an optimized cryopreservation strategy for Treg products presents a substantial obstacle to their broader application, particularly as administration of fresh cells limits the window available for sterility and functional assessment. In this study, we aimed to develop an optimized cryopreservation strategy for our CD4+CD25+Foxp3+ Treg clinical product. We investigate the effect of synthetic or organic cryoprotectants including different concentrations of DMSO on Treg recovery, viability, phenotype, cytokine production, suppressive capacity, and in vivo survival following GMP-compliant manufacture. We additionally assess the effect of adding the extracellular cryoprotectant polyethylene glycol (PEG), or priming cellular expression of heat shock proteins as strategies to improve viability. We find that cryopreservation in serum-free freezing medium supplemented with 10% human serum albumin and 5% DMSO facilitates improved Treg recovery and functionality and supports a reduced DMSO concentration in Treg cryopreservation protocols. This strategy may be easily incorporated into clinical manufacture protocols for future studies.

Anti-thymocyte globulin and post-transplant cyclophosphamide predisposes to inferior outcome when using cryopreserved stem cell grafts

During 2020, the concurrent novel COVID-19 pandemic lead to widespread cryopreservation of allogeneic hematopoietic cell transplant grafts based on National Marrow Donor Program and European Society of Blood and Marrow Transplantation recommendations, in order to secure grafts before the start of conditioning chemotherapy. We sought to examine the impact of this change in practice on patient outcomes. We analyzed the outcomes of 483 patients who received hematopoietic stem cell transplantation (HSCT) between August 2017 and August 2020, at Princess Margaret Cancer Centre, Canada, in the retrospective study, comparing the outcomes between those who received cryopreserved or fresh peripheral blood stem cell grafts. Overall compared with those who received fresh grafts (n = 348), patients who received cryopreserved grafts (n = 135) had reduced survival and GRFS, reduced incidence of chronic graft-versus-host disease (GvHD), delay in neutrophil engraftment, and higher graft failure (GF), with no significant difference in relapse incidence or acute GvHD. However, recipients of cryopreserved matched-related donor HSCT showed significantly worse OS, NRM, GRFS compared with fresh grafts. Multivariable analysis of the entire cohort showed significant impact of cryopreservation on OS, relapse, cGvHD, GF, and GRFS. We conclude that cryopreservation was associated with inferior outcomes post-HSCT, possibly due to the combination of ATG and post-transplant cyclophosphamide impacting differential tolerance to cryopreservation on components of the stem cell graft; further studies are warranted to elucidate mechanisms for this observation.

Cryopreservation of NK and T Cells Without DMSO for Adoptive Cell-Based Immunotherapy

Dimethylsufoxide (DMSO) being universally used as a cryoprotectant in clinical adoptive cell-therapy settings to treat hematological malignancies and solid tumors is a growing concern, largely due to its broad toxicities. Its use has been associated with significant clinical side effects-cardiovascular, neurological, gastrointestinal, and allergic-in patients receiving infusions of cell-therapy products. DMSO has also been associated with altered expression of natural killer (NK) and T-cell markers and their in vivo function, not to mention difficulties in scaling up DMSO-based cryoprotectants, which introduce manufacturing challenges for autologous and allogeneic cellular therapies, including chimeric antigen receptor (CAR)-T and CAR-NK cell therapies. Interest in developing alternatives to DMSO has resulted in the evaluation of a variety of sugars, proteins, polymers, amino acids, and other small molecules and osmolytes as well as modalities to efficiently enable cellular uptake of these cryoprotectants. However, the DMSO-free cryopreservation of NK and T cells remains difficult. They represent heterogeneous cell populations that are sensitive to freezing and thawing. As a result, clinical use of cryopreserved cell-therapy products has not moved past the use of DMSO. Here, we present the state of the art in the development and use of cryopreservation options that do not contain DMSO toward clinical solutions to enable the global deployment of safer adoptively transferred cell-based therapies.

Development and Validation of a Good Manufacturing Process for IL-4-Driven Expansion of Chimeric Cytokine Receptor-Expressing CAR T-Cells

Adoptive cancer immunotherapy using chimeric antigen receptor (CAR) engineered T-cells holds great promise, although several obstacles hinder the efficient generation of cell products under good manufacturing practice (GMP). Patients are often immune compromised, rendering it challenging to produce sufficient numbers of gene-modified cells. Manufacturing protocols are labour intensive and frequently involve one or more open processing steps, leading to increased risk of contamination. We set out to develop a simplified process to generate autologous gamma retrovirus-transduced T-cells for clinical evaluation in patients with head and neck cancer. T-cells were engineered to co-express a panErbB-specific CAR (T1E28z) and a chimeric cytokine receptor (4αβ) that permits their selective expansion in response to interleukin (IL)-4. Using peripheral blood as starting material, sterile culture procedures were conducted in gas-permeable bags under static conditions. Pre-aliquoted medium and cytokines, bespoke connector devices and sterile welding/sealing were used to maximise the use of closed manufacturing steps. Reproducible IL-4-dependent expansion and enrichment of CAR-engineered T-cells under GMP was achieved, both from patients and healthy donors. We also describe the development and approach taken to validate a panel of monitoring and critical release assays, which provide objective data on cell product quality.

A Comparison of Automated Perfusion- and Manual Diffusion-Based Human Regulatory T Cell Expansion and Functionality Using a Soluble Activator Complex

Absence or reduced frequency of human regulatory T cells (Tregs) can limit the control of inflammatory responses, autoimmunity, and the success of transplant engraftment. Clinical studies indicate that use of Tregs as immunotherapeutics would require billions of cells per dose. The Quantum® Cell Expansion System (Quantum system) is a hollow-fiber bioreactor that has previously been used to grow billions of functional T cells in a short timeframe, 8–9 d. Here we evaluated expansion of selected Tregs in the Quantum system using a soluble activator to compare the effects of automated perfusion with manual diffusion-based culture in flasks. Treg CD4⁺CD25⁺ cells from three healthy donors, isolated via column-free immunomagnetic negative/positive selection, were grown under static conditions and subsequently seeded into Quantum system bioreactors and into T225 control flasks in an identical culture volume of PRIME-XV XSFM medium with interleukin-2, for a 9-d expansion using a soluble anti-CD3/CD28/CD2 monoclonal antibody activator complex. Treg harvests from three parallel expansions produced a mean of 3.95 × 10⁸ (range 1.92 × 10⁸ to 5.58 × 10⁸) Tregs in flasks (mean viability 71.3%) versus 7.00 × 10⁹ (range 3.57 × 10⁹ to 13.00 × 10⁹) Tregs in the Quantum system (mean viability 91.8%), demonstrating a mean 17.7-fold increase in Treg yield for the Quantum system over that obtained in flasks. The two culture processes gave rise to cells with a memory Treg CD4⁺CD25⁺FoxP3⁺CD45RO⁺ phenotype of 93.7% for flasks versus 97.7% for the Quantum system. Tregs from the Quantum system demonstrated an 8-fold greater interleukin-10 stimulation index than cells from flask culture following restimulation. Quantum system–expanded Tregs proliferated, maintained their antigenic phenotype, and suppressed effector immune cells after cryopreservation. We conclude that an automated perfusion bioreactor can support the scale-up expansion of functional Tregs more efficiently than diffusion-based flask culture.

Regulatory T cells from patients with end-stage organ disease can be isolated, expanded and cryopreserved according good manufacturing practice improving their function

BACKGROUND

Here, we isolated, expanded and functionally characterized regulatory T cells (Tregs) from patients with end stage kidney and liver disease, waiting for kidney/liver transplantation (KT/LT), with the aim to establish a suitable method to obtain large numbers of immunomodulatory cells for adoptive immunotherapy post-transplantation.

METHODS

We first established a preclinical protocol for expansion/isolation of Tregs from peripheral blood of LT/KT patients. We then scaled up and optimized such protocol according to good manufacturing practice (GMP) to obtain high numbers of purified Tregs which were phenotypically and functionally characterized in vitro and in vivo in a xenogeneic acute graft-versus-host disease (aGVHD) mouse model. Specifically, immunodepressed mice (NOD-SCID-gamma KO mice) received human effector T cells with or without GMP-produced Tregs to prevent the onset of xenogeneic GVHD.

RESULTS

Our small scale Treg isolation/expansion protocol generated functional Tregs. Interestingly, cryopreservation/thawing did not impair phenotype/function and DNA methylation pattern of FOXP3 gene of the expanded Tregs. Fully functional Tregs were also isolated/expanded from KT and LT patients according to GMP. In the mouse model, GMP Tregs from LT or KT patient proved to be safe and show a trend toward reduced lethality of acute GVHD.

CONCLUSIONS

These data demonstrate that expanded/thawed GMP-Tregs from patients with end-stage organ disease are fully functional in vitro. Moreover, their infusion is safe and results in a trend toward reduced lethality of acute GVHD in vivo, further supporting Tregs-based adoptive immunotherapy in solid organ transplantation.

Characterization, biology, and expansion of regulatory T cells in the Cynomolgus macaque for preclinical studies

Reliable in vitro expansion protocols of regulatory T cells (Tregs) are needed for clinical use. We studied the biology of Mauritian Cynomolgus macaque (MCM) Tregs and developed four in vitro Treg expansion protocols for translational studies. Tregs expanded 3000-fold when artificial antigen presenting cells (aAPCs) expressing human CD80, CD58 and CD32 were used throughout the culture. When donor peripheral blood mononuclear cells (PBMCs) were used as the single source of APCs followed by aAPCs, Tregs expanded 2000-fold. Tregs from all protocols suppressed the proliferation of anti-CD2CD3CD28 bead-stimulated autologous PBMCs albeit with different potencies, varying from 1:2-1:4 Treg:PBMC ratios, up to >1:32. Reculture of cryopreserved Tregs permitted reexpansion with improved suppressive activity. Occasionally, CD8 contamination was observed and resolved by resorting. Specificity studies showed greater suppression of stimulation by anti-CD2CD3CD28 beads of PBMCs from the same donor used for stimulation during the Treg cultures and of autologous cells than of third-party PBMC responders. Similar to humans, the Treg-specific demethylated region (TSDR) within the Foxp3 locus correlated with suppressive activity and expression of Foxp3. Contrary to humans, FoxP3 expression did not correlate with CD45RA or CD127 expression. In summary, we have characterized MCM Tregs and developed four Treg expansion protocols that can be used for preclinical applications.

Transforming growth factor-β1-overexpressing mesenchymal stromal cells induced local tolerance in rat renal ischemia/reperfusion injury

BACKGROUND

Regulatory T cells (Tregs) suppress excessive immune responses and play a crucial protective role in acute kidney injury (AKI). The aim of this study was to examine the therapeutic potential of transforming growth factor (TGF)-β1-overexpressing mesenchymal stromal cells (MSCs) in inducing local generation of Tregs in the kidney after ischemia/reperfusion (I/R) injury.

METHODS

MSCs were transduced with a lentiviral vector expressing the TGF-β1 gene; TGF-β1-overexpressing MSCs (designated TGF-β1/MSCs) were then transfused into the I/R-injured kidney via the renal artery.

RESULTS

MSCs genetically modified with TGF-β1 achieved overexpression of TGF-β1. Compared with green fluorescent protein (GFP)/MSCs, TGF-β1/MSCs markedly improved renal function after I/R injury and reduced epithelial apoptosis and subsequent inflammation. The enhanced immunosuppressive and therapeutic abilities of TGF-β1/MSCs were associated with increased generation of induced Tregs and improved intrarenal migration of the injected cells. Futhermore, the mechanism of TGF-β1/MSCs in attenuating renal I/R injury was not through a direct canonical TGF-β1/Smad pathway.

CONCLUSION

TGF-β1/MSCs can induce a local immunosuppressive effect in the I/R-injured kidney. The immunomodulatory activity of TGF-β1-modified MSCs appears to be a gateway to new therapeutic approaches to prevent renal I/R injury.

Isolation of Human Regulatory T Lymphocytes by Fluorescence-Activated Cell Sorting

Regulatory T cells (Tregs) are a population of lymphocytes that exerts suppressive effects upon the immune system. In human peripheral blood, the major population of T lymphocytes with suppressive capacity are defined by expression of the T cell co-receptor CD4 and the interleukin-2 receptor α-chain (CD25), combined with minimal expression of the interleukin-7 receptor α subunit (CD127). We begin by outlining the method for isolating peripheral blood mononuclear cells (PBMCs) from human blood by centrifugation of whole blood overlayed on a hydrophilic polysaccharide, with an additional erythrocyte lysis step. The protocol that follows utilizes Fluorescence-Activated Cell Sorting (FACS) for the isolation of this CD4⁺CD25⁺CD127^lo population of regulatory T cells, with high yield and purity, from immunostained PBMCs. Prior to FACS isolation, this protocol exploits magnetic immunoselection for pre-enrichment of CD25⁺ PBMC, which reduces the duration of the subsequent FACS isolation.

Effect of peripheral blood mononuclear cell cryopreservation on innate and adaptive immune responses

Cryopreservation of blood-derived immune cells is commonly used in clinical trials to examine immunological responses. However, studies elucidating the effects of cryopreservation on peripheral blood mononuclear cell (PBMC) responses have shown inconsistent results making it difficult to draw meaningful conclusions. Therefore we sought to address this issue by comparing key innate and adaptive immune parameters between freshly-isolated and cryopreserved PBMCs from healthy adults. We examined the effect of cryopreservation on the expression of key markers on innate and adaptive immune cell populations (i.e. CD4+ and CD8+ [T cells], CD14+ [monocytes], CD19+ [B cells], CD56+ [NK cells] or CD19 + CD27+ [memory B cells]), on cytokine secretion (TNF-α, INF-γ, IL-1β, IL-10, IL-6, MCP-1 and RANTES) in cultured PBMC supernatants following stimulation with a range of Toll-like receptor (TLR) agonists, as well as on antigen-specific memory B cell enumeration by ELISpot. We found that cryopreservation had no effect on the expression of immune markers on innate and adaptive immune cells as well on the number of antigen-specific memory B cells. However, the response to TLR ligands such as FLA-ST, CpG and LPS was variable with increased cytokine production by cryopreserved PBMCs observed compared to freshly-isolated PBMCs. Our results suggest that the effect of cryopreservation on the biological response of immune cell populations needs to be carefully considered, particularly in the context of clinical studies that rely on these immune outcomes.

Cell banking for regulatory T cell-based therapy: strategies to overcome the impact of cryopreservation on the Treg viability and phenotype

The first clinical trials with adoptive Treg therapy have shown safety and potential efficacy. Feasibility of such therapy could be improved if cells are cryopreserved and stored until optimal timing for infusion. Herein, we report the evaluation of two cell-banking strategies for Treg therapy: 1) cryopreservation of CD4+ cells for subsequent Treg isolation/expansion and 2) cryopreservation of ex-vivo expanded Tregs (CD4+CD25hiCD127lo/- cells). First, we checked how cryopreservation affects cell viability and Treg markers expression. Then, we performed Treg isolation/expansion with the final products release testing. We observed substantial decrease in cell number recovery after thawing and overnight culture. This observation might be explained by the high percentage of necrotic and apoptotic cells found just after thawing. Furthermore, we noticed fluctuations in percentage of CD4+CD25hiCD127- and CD4+FoxP3+ cells obtained from cryopreserved CD4+ as well as Treg cells. However, after re-stimulation Tregs expanded well, presented a stable phenotype and fulfilled the release criteria at the end of expansions. Cryopreservation of CD4+ cells for subsequent Treg isolation/expansion and cryopreservation of expanded Tregs with re-stimulation and expansion after thawing, are promising solutions to overcome detrimental effects of cryopreservation. Both of these cell-banking strategies for Treg therapy can be applied when designing new clinical trials.

Good Manufacturing Practice-Compliant Production and Lot-Release of Ex Vivo Expanded Regulatory T Cells As Basis for Treatment of Patients with Autoimmune and Inflammatory Disorders

In recent years, the exploration of regulatory T cell (Treg)-based cellular therapy has become an attractive strategy to ameliorate inflammation and autoimmunity in various clinical settings. The main obstacle to the clinical application of Treg in human is their low number circulating in peripheral blood. Therefore, ex vivo expansion is inevitable. Moreover, isolation of Treg bears the risk of concurrent isolation of unwanted effector cells, which may trigger or deteriorate inflammation upon adoptive Treg transfer. Here, we present a protocol for the GMP-compliant production, lot-release and validation of ex vivo expanded Tregs for treatment of patients with autoimmune and inflammatory disorders. In the presented production protocol, large numbers of Treg, previously enriched from a leukapheresis product by using the CliniMACS^® system, are ex vivo expanded in the presence of anti-CD3/anti-CD28 expander beads, exogenous IL-2 and rapamycin during 21 days. The expanded Treg drug product passed predefined lot-release criteria. These criteria include (i) sterility testing, (ii) assessment of Treg phenotype, (iii) assessment of non-Treg cellular impurities, (iv) confirmation of successful anti-CD3/anti-CD28 expander bead removal after expansion, and (v) confirmation of the biological function of the Treg product. Furthermore, the Treg drug product was shown to retain its stability and suppressive function for at least 1 year after freezing and thawing. Also, dilution of the Treg drug product in 0.9% physiological saline did not affect Treg phenotype and Treg function for up to 90 min. These data indicate that these cells are ready to use in a clinical setting in which a cell infusion time of up to 90 min can be expected. The presented production process has recently undergone on site GMP-conform evaluation and received GMP certification from the Bavarian authorities in Germany. This protocol can now be used for Treg-based therapy of various inflammatory and autoimmune disorders.

High density lipoproteins selectively promote the survival of human regulatory T cells

HDLs appear to affect regulatory T cell (Treg) homeostasis, as suggested by the increased Treg counts in HDL-treated mice and by the positive correlation between Treg frequency and HDL-cholesterol levels in statin-treated healthy adults. However, the underlying mechanisms remain unclear. Herein, we show that HDLs, not LDLs, significantly decreased the apoptosis of human Tregs in vitro, whereas they did not alter naïve or memory CD4⁺ T cell survival. Similarly, oleic acid bound to serum albumin increased Treg survival. Tregs bound and internalized high amounts of HDL compared with other subsets, which might arise from the higher expression of the scavenger receptor class B type I by Tregs; accordingly, blocking this receptor hindered HDL-mediated Treg survival. Mechanistically, we showed that HDL increased Treg ATP concentration and mitochondrial activity, enhancing basal respiration, maximal respiration, and spare respiratory capacity. Blockade of FA oxidation by etoxomir abolished the HDL-mediated enhanced survival and mitochondrial activity. Our findings thus suggest that Tregs can specifically internalize HDLs from their microenvironment and use them as an energy source. Furthermore, a novel implication of our data is that enhanced Treg survival may contribute to HDLs' anti-inflammatory properties.

Generation of donor-specific Tr1 cells to be used after kidney transplantation and definition of the timing of their in vivo infusion in the presence of immunosuppression

Background

Operational tolerance is an alternative to lifelong immunosuppression after transplantation. One strategy to achieve tolerance is by T regulatory cells. Safety and feasibility of a T regulatory type 1 (Tr1)-cell—based therapy to prevent graft versus host disease in patients with hematological malignancies has been already proven. We are now planning to perform a Tr1-cell—based therapy after kidney transplantation.

Methods

Upon tailoring the lab-grade protocol to patients on dialysis, aims of the current work were to develop a clinical-grade compatible protocol to generate a donor-specific Tr1-cell—enriched medicinal product (named T₁₀ cells) and to test the Tr1-cell sensitivity to standard immunosuppression in vivo to define the best timing of cell infusion.

Results

We developed a medicinal product that was enriched in Tr1 cells, anergic to donor-cell stimulation, able to suppress proliferation upon donor- but not third-party stimulation in vitro, and stable upon cryopreservation. The protocol was reproducible upon up scaling to leukapheresis from patients on dialysis and was effective in yielding the expected number of T₁₀ cells necessary for the planned infusions. The tolerogenic gene signature of circulating Tr1 cells was minimally compromised in kidney transplant recipients under standard immunosuppression and it eventually started to recover 36 weeks post-transplantation, providing rationale for selecting the timings of the cell infusions.

Conclusions

These data provide solid ground for proceeding with the trial and establish robust rationale for defining the correct timing of cell infusion during concomitant immunosuppressive treatment.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1133-8) contains supplementary material, which is available to authorized users.

An innovative method to generate a Good Manufacturing Practice-ready regulatory T-cell product from non-mobilized leukapheresis donors

BACKGROUND AIMS

There is real and sustained interest in preparing T-regulatory cells from leukapheresis collections for cellular therapy through the use of simple, effective and reliable methods conforming to Good Manufacturing Practice (GMP). We describe a GMP-ready isolation procedure for CD25(+) products with the use of a sterile docking device, pigtail sampling, a laminar flow hood and the CliniMACS system that uses leukapheresis collections made by two apheresis machines.

METHODS

We used CD8/CD19 depletion followed by CD25-positive selection. The median number of CD4(+) cells recovered was 72.5 ± 32.6 × 10(6), of which 60.5% ± 17.8% were CD25(+)FOXP3(+) cells. Suppression of autologous CD25(-) cell proliferation by the cryopreserved CD25(+) products was 51.3% ± 4.4%, 49.0% ± 3.7% and 39.0% ± 3.6% at CD25(+):CD25(-) ratios of 1:1, 1:2 and 1:4 (n = 6), respectively, comparable to suppression by fresh CD25(+) products (53% ± 6.2%, 51% ± 3.3% and 39% ± 7.1%).

RESULTS

We found Leukapheresis collections by Cobe Spectra contained more lymphocytes and platelets than collections by Spectra Optia apheresis machine (median, 9.2 × 10(9) versus 6.7 × 10(9); P = 0.04) and platelets (median, 610 × 10(9) versus 170 × 10(9); P = 0.04). The frequency of CD4(+)CD25(+)FOXP3(+) was significantly higher in the leukapheresis (4.85%; 95% confidence interval, 1.95% to 5.38%) than in peripheral blood (3.9%; 95% confidence interval, 2.63% to 6.45%) (P = 0.02). The CD8- and CD19-negative depletion step was associated with significant loss of total CD4(+) T cells (P = 0.001).

CONCLUSIONS

Results suggest that functional CD25(+) products can be isolated with a GMP-ready method, and good recovery can be obtained with the use of an optimized cryopreservation protocol. These data and methods show the potential, possibilities and future work needed to isolate target cell populations in a reproducible, time-efficient and cost-efficient manner for clinical applications.

Research Progress on Regulatory T Cells in Acute Kidney Injury

Immune inflammation is crucial in mediating acute kidney injury (AKI). Immune cells of both the innate and adaptive immune systems substantially contribute to overall renal damage in AKI. Regulatory T cells (Tregs) are key regulator of immunological function and have been demonstrated to ameliorate injury in several murine experimental models of renal inflammation. Recent studies have illuminated the renal-protective function of Tregs in AKI. Tregs appear to exert beneficial effects in both the acute injury phase and the recovery phase of AKI. Additionally, Tregs-based immunotherapy may represent a promising approach to ameliorate AKI and promote recovery from AKI. This review will highlight the recent insights into the role of Tregs and their therapeutic potential in AKI.

Islet cell transplant and the incorporation of Tregs

PURPOSE OF REVIEW

T regulatory cells (Tregs) play a central role in maintaining immune homeostasis and peripheral tolerance to foreign antigens in humans. The immune response to alloantigens and recurrence of autoimmunity contribute to pancreatic islet transplant dysfunction, hence the adoptive transfer of Tregs has the potential to significantly improve islet graft survival. In this review, we provide an in-depth analysis of challenges associated with the application of ex-vivo expanded Tregs therapy in pancreatic islet transplant.

RECENT FINDINGS

Tregs administered systemically may poorly migrate to the site of transplantation, which is critical for tolerance induction and graft protection. Intraportal administration of pancreatic tissue exerts some limitations on the ability to cotransplant Tregs at the same site of islet transplantation. In order to maximize therapeutic potential of Tregs, islet transplantation protocols may need additional refinement. Further to this, the Tregs may require cryopreservation in order to make them readily available at the same time as islet transplant.

SUMMARY

On the basis of current experience and technology, the combination of islet and Treg cotransplantation is feasible and has great potential to improve islet graft survival. The possibility to wean off, or withdraw, traditional immunosuppressive agents and improve patient quality of life makes it an interesting avenue to be pursued.

Generation, cryopreservation, function and in vivo persistence of ex vivo expanded cynomolgus monkey regulatory T cells

We expanded flow-sorted Foxp3(+) cynomolgus monkey regulatory T cells (Treg) >1000-fold after three rounds of stimulation with anti-CD3 mAb-loaded artificial antigen-presenting cells, rapamycin (first round only) and IL-2. The expanded Treg maintained their expression of Treg signature markers, CD25, CD27, CD39, Foxp3, Helios, and CTLA-4, as well as CXCR3, which plays an important role in T cell migration to sites of inflammation. In contrast to expanded effector T cells (Teff), expanded Treg produced minimal IFN-γ and IL-17 and no IL-2 and potently suppressed Teff proliferation. Following cryopreservation, thawed Treg were less viable than their freshly-expanded counterparts, although no significant changes in phenotype or suppressive ability were observed. Additional rounds of stimulation/expansion restored maximal viability. Furthermore, adoptively-transferred autologous Treg expanded from cryopreserved second round stocks and labeled with CFSE or VPD450 were detected in blood and secondary lymphoid tissues of normal or immunosuppressed recipients at least two months after their systemic infusion.

Restimulation After Cryopreservation and Thawing Preserves the Phenotype and Function of Expanded Baboon Regulatory T Cells

BACKGROUND

Regulatory T cells (Treg) are being explored for their tolerance-inducing capabilities. Freezing and banking Treg for future use makes this strategy more clinically applicable. We aimed to devise an improved method of expanding and cryopreserving Treg to maximize yield, purity, and function for use in xenotransplantation.

METHODS

Baboon peripheral blood mononuclear cells (PBMC) were isolated from whole blood. CD4+/CD25^hi cells were isolated by flow cytometric sorting and expanded for 26 days in culture with IL-2, anti-CD3 antibody, artificial APCs transfected with human CD58, CD32, and CD80, and rapamycin with weekly restimulations. Expanded Treg were frozen for 2 months then thawed and cultured for 48 hours in medium plus 1) no additives, 2) IL-2, 3) anti-CD3 antibody, 4) IL-2 + anti-CD3 antibody, and 5) IL-2 + anti-CD3 antibody + L cells. Phenotype and suppression were assessed after expansion, immediately after thawing, and after culturing.

RESULTS

We expanded purified baboon Treg more than 10,000-fold. Expanded Treg exhibited excellent suppression in functional assays. Cryopreservation decreased suppressive function without changing phenotype, but increasing amounts of reactivation after thawing produced significantly better viability and suppressive function with a trend towards greater Treg purity.

CONCLUSIONS

We produced numbers of expanded Tregs consistent with clinical use. In contrast to some previous reports, both Treg phenotype and suppressive function were preserved or even enhanced by increasing amounts of restimulation after thawing. Thus, banking of expanded recipient Tregs for in vivo infusion should be possible.

Effect of chorioamnionitis on regulatory T cells in moderate/late preterm neonates

Regulatory T-cells (Treg) have a protective role for the control of immune activation and tissue damage. The effects of chorioamnionitis (chorio) on Treg in moderate/late preterm newborns are not known. We hypothesized that infants exposed to chorio would have decreased Treg frequency and/or function. We isolated mononuclear cells from adult peripheral blood and cord blood from term and moderate/late preterm infants who were classified for severity of chorio exposure. Mononuclear cells were analyzed by flow cytometry for Treg frequency and phenotype. Treg suppression of activation of conventional T-cells (Tcon) was also quantified. Treg frequencies were similar in all groups of neonates, but lower than that found in adults. Newborn Treg had a naïve phenotype, with decreased levels of CD45RO, HLA-DR, CD39 and TIGIT compared to adult Treg and chorio did not affect the phenotype. Treg from preterm newborns exposed to severe chorio had higher expression of Ki67 compared to the other groups. Treg from preterm newborns were less suppressive than Treg from adults or term, and the level of suppression was reduced with severe chorio. Relative to term, Treg frequency and phenotype were not affected by prematurity and chorio but their functionality was decreased. Lower Treg activity may contribute to inflammation in newborns that is often associated with chorioamnionitis.

Treatment of graft-versus-host disease with naturally occurring T regulatory cells

A significant body of evidence suggests that treatment with naturally occurring CD4⁺CD25⁺ T regulatory cells (Tregs) is an appropriate therapy for graft-versus-host disease (GvHD). GvHD is a major complication of bone marrow transplantation in which the transplanted immune system recognizes recipient tissues as a non-self and destroys them. In many cases, this condition significantly deteriorates the quality of life of the affected patients. It is also one of the most important causes of death after bone marrow transplantation. Tregs constitute a population responsible for dominant tolerance to self-tissues in the immune system. These cells prevent autoimmune and allergic reactions and decrease the risk of rejection of allotransplants. For these reasons, Tregs are considered as a cellular drug in GvHD. The results of the first clinical trials with these cells are already available. In this review we present important experimental facts which led to the clinical use of Tregs. We then critically evaluate specific requirements for Treg therapy in GvHD and therapies with Tregs currently under clinical investigation, including our experience and future perspectives on this kind of cellular treatment.

Therapy of type 1 diabetes with CD4(+)CD25(high)CD127-regulatory T cells prolongs survival of pancreatic islets - results of one year follow-up

It is hypothesized that CD4(+)CD25(+)FoxP3(+) regulatory T cells (Tregs) can prevent destruction of pancreatic islets protecting from type 1 diabetes (DM1). Here we present results of one year follow-up of 12 DM1 children treated with autologous expanded ex vivo Tregs. Patients received either a single or double Tregs infusion up to the total dose of 30×10(6)/kg. No severe adverse effects were observed. The treatment did not impair post-immunization antibody responses. Tregs infusion was followed by increase in Tregs number in peripheral blood. Most of the patients responded to the therapy with increase in C-peptide levels (8/12 and 4/6 after the first and the second dose, respectively). Tregs administration resulted also in lower requirement for exogenous insulin (8/12 treated patients versus 2/10 untreated controls in remission) with two children completely insulin independent at one year. Repetitive administration of Tregs is safe and can prolong survival of β-cells in DM1 (registration: ISRCTN06128462).

Regulatory T cells as immunotherapy

Regulatory T cells (Tregs) suppress exuberant immune system activation and promote immunologic tolerance. Because Tregs modulate both innate and adaptive immunity, the biomedical community has developed an intense interest in using Tregs for immunotherapy. Conditions that require clinical tolerance to improve outcomes – autoimmune disease, solid organ transplantation, and hematopoietic stem cell transplantation – may benefit from Treg immunotherapy. Investigators have designed ex vivo strategies to isolate, preserve, expand, and infuse Tregs. Protocols to manipulate Treg populations in vivo have also been considered. Barriers to clinically feasible Treg immunotherapy include Treg stability, off-cell effects, and demonstration of cell preparation purity and potency. Clinical trials involving Treg adoptive transfer to treat graft versus host disease preliminarily demonstrated the safety and efficacy of Treg immunotherapy in humans. Future work will need to confirm the safety of Treg immunotherapy and establish the efficacy of specific Treg subsets for the treatment of immune-mediated disease.

Stress proteins are used by the immune system for cognate interactions with anti-inflammatory regulatory T cells

Since the initial discovery of the protective role of heat shock protein (HSP) 60 in arthritis, T cell recognition of endogenous HSP was found to be one of the possible underlying mechanisms. Recently we have uncovered potent disease-suppressive Tregs (anti-inflammatory immunosuppressive T cells) recognizing HSP70 self-antigens, and enabling selective targeting of such Tregs to inflamed tissues. HSP70 is a major contributor to the major histocompatibility complex (MHC) Class II ligandome and we have shown that a conserved HSP70-epitope (B29) is abundantly present in murine MHC Class II. Upon transfer, B29-induced CD4+CD25+Foxp3+T cells suppressed established proteoglycan-induced arthritis (PGIA) in mice. These self-antigen specific Tregs were activated in vivo and as little as 4.000 cells sufficed to fully inhibit arthritis. Furthermore, in vivo depletion of transferred Tregs abrogated disease suppression. Given that B29 can be presented by most human MHC class II molecules and that B29 inhibited arthritis in HLA-DQ8 (human MHC) transgenic mice, we feel that therapeutic vaccination with selected HSP peptides can be an effective route for induction of anti-inflammatory Tregs as a novel intervention in chronic inflammatory diseases.