High purity and yield of natural Tregs from cord blood using a single step selection method

Multiply restimulated human cord blood-derived Tregs maintain stabilized phenotype and suppressive function and predict their therapeutic effects on autoimmune diabetes

BACKGROUND

Regulatory T cells (Tregs) are involved in the maintenance of immune homeostasis and immune regulation. Clinical trials on the adoptive transfer of Tregs have been ongoing for > 10 years. However, many unresolved issues remain in the production of readymade Treg products and selection of patients. Hence, this study aimed to develop a method to expand off-the-shelf Tregs derived from umbilical cord blood (UCB-Tregs) in vitro without changing their phenotype and inhibitory function. In addition, the study intended to design an approach to precisely select patients who are more likely to benefit from the adoptive Treg transfer therapy.

METHODS

UCB-Tregs were isolated and cultured in a medium containing human recombinant IL-2 and rapamycin and then multiply restimulated with human T-activator CD3/CD28 dynabeads. The phenotype and suppressive capacity of Tregs were assessed on days 18 and 42. The relationship between the suppressive function of UCB-Tregs in vitro and clinical indicators was analyzed, and the ability of the in vitro suppressive capacity to predict the in vivo therapeutic effects was evaluated.

RESULTS

UCB-Tregs expanded 123-fold and 5,981-fold at 18 and 42 days, respectively. The suppressive function of UCB-Tregs on the proliferation of immune cells at 42 days was not significantly different compared with that of UCB-Tregs obtained at 18 days. The suppression rate of UCB-Tregs to PBMCs was negatively correlated with the course of diabetes. Moreover, the high-suppression group exhibited a better treatment response than the low-suppression group during the 12-month follow-up period.

CONCLUSIONS

Multiply restimulated UCB-Tregs expanded at a large scale without any alterations in their classical phenotypic features and inhibitory functions. The suppressive function of Tregs in vitro was negatively correlated with the disease duration. The present study revealed the possibility of predicting the in vivo therapeutic effects via the in vitro inhibition assay. Thus, these findings provided a method to obtain off-the-shelf Treg products and facilitated the selection of patients who are likely to respond to the treatment, thereby moving toward the goal of precision treatment.

Umbilical cord blood and peripheral blood-derived regulatory T cells therapy: Progress in type 1 diabetes

Regulatory T cells (Tregs) are key regulators for the inflammatory response and play a role in maintaining the immune tolerance. Type 1 diabetes (T1D) is a relatively common autoimmune disease that results from the loss of immune tolerance to β-cell-associated antigens. Preclinical models have demonstrated the safety and efficacy of Tregs given in transplant rejection and autoimmune diseases such as T1D. Adoptive transfer of Tregs has been utilized in clinical trials for over a decade. However, the achievement of the adoptive transfer of Tregs therapy in clinical application remains challenging. In this review, we highlight the characterization of Tregs and compare the differences between umbilical cord blood and adult peripheral blood-derived Tregs. Additionally, we summarize conditional modifications in the expansion of Tregs in clinical trials, especially for the treatment of T1D. Finally, we discuss the existing technical challenges for Tregs in clinical trials for the treatment of T1D.

Enumerating regulatory T cells in cryopreserved umbilical cord blood samples using FOXP3 methylation specific quantitative PCR

BACKGROUND

Allogeneic haematopoietic cell transplantation (HCT) is a curative therapy for severe haematological disorders. However, it carries significant risk of morbidity and mortality. To improve patient outcomes, better graft selection strategies are needed, incorporating HLA matching with clinically important graft characteristics. Studies have shown that the cellular content of HCT grafts, specifically higher ratios of T regulatory (Tregs)/T cells, are important factors influencing outcomes when using adult peripheral blood mobilised grafts. So far, no equivalent study exists in umbilical cord blood (CB) transplantation due to the limitations of cryopreserved CB samples.

STUDY DESIGN AND METHODS

To establish the most robust and efficient way to measure the Treg content of previously cryopreserved CB units, we compared the enumeration of Treg and CD3+ cells using flow cytometry and an epigenetic, DNA-based methodology. The two methods were assessed for their agreement, consistency and susceptibility to error when enumerating Treg and CD3+ cell numbers in both fresh and cryopreserved CB samples.

RESULTS

Epigenetic enumeration gave consistent and comparable results in both fresh and frozen CB samples. By contrast, assessment of Tregs and CD3+ cells by flow cytometry was only possible in fresh samples due to significant cell death following cryopreservation and thawing.

CONCLUSION

Epigenetic assessment offers significant advantages over flow cytometry for analysing cryopreserved CB; similar cell numbers were observed both in fresh and frozen samples. Furthermore, multiple epigenetic assessments can be performed from DNA extracted from small cryopreserved CB segments; often the only CB sample available for clinical studies.

Ex vivo generation of umbilical cord blood T regulatory cells expressing the homing markers CD62L and cutaneous lymphocyte antigen

Regulatory T cells (Tregs) are an important component of the immune system involved in regulation of immune cell proliferation and inflammatory responses and preventing autoimmune diseases. The use of Tregs in cellular therapy has recently been explored in clinical trials specifically evaluating the role of ex vivo expanded Tregs in the prevention of graft-versus-host disease during stem cell transplantation. The possibility of Treg use in the clinic requires clinical grade expansion of Tregs for development of cell therapy protocols and proper homing of Tregs to the intended target. Here we demonstrate a novel medium composition to expand CB Tregs, specifically upregulation the homing and activation markers CD62L and cutaneous lymphocyte antigen (CLA). CLA expression was uniquely acquired during activation of Tregs with subsequent loss or lack of expression with media change. This finding highlights the importance of proper growth conditions unique to Tregs that can alter expression of proteins and establishes a baseline for expanding marker specific Tregs that home and target unique tissues.

Immunotherapy after hematopoietic stem cell transplantation using umbilical cord blood-derived products

Umbilical cord blood (UCB) is being increasingly used as a source of hematopoietic stem cells (HSC) for transplantation. UCB transplantation (UCBT) has some advantages such as less stringent HLA-matching requirements, fast availability of the graft and reduced incidence and severity of graft-versus-host disease. However, UCBT is also associated with a higher incidence of infection, graft failure, slow engraftment and slow immune reconstitution. UCB is mainly used as a source of HSC; however, it is also rich in immune cells that could be used to treat some of the main complications post-UCBT as well as other diseases, thus implicating the use of UCB for immunotherapy. Here, we aim to describe some of the therapies currently developed that use UCB as a cell source, focusing in particular on regulatory T cells and natural killer cells.

Regulatory T cells inhibit CD34+ cell differentiation into NK cells by blocking their proliferation

Graft versus Host Disease (GvHD) remains one of the main complications after hematopoietic stem cell transplantation (HSCT). Due to their ability to suppress effector cells, regulatory T cells (Tregs) have been proposed as a cellular therapy to prevent GvHD, however they also inhibit the functions of natural killer (NK) cells, key effectors of the Graft versus Leukemia effect. In this study, we have explored whether a Tregs therapy will also impact on NK cell differentiation. Using an in vitro model of hematopoietic stem cell (HSC) differentiation into NK cells, we found that activated Tregs led to a 90% reduction in NK cell numbers when added at the time of commitment to the NK cell lineage. This effect was contact dependent and was reversible upon Tregs depletion. The few NK cells that developed in these cultures were mature and exhibited normal functions. Furthermore, adoptive transfer of activated Tregs in rag(-/-) γc(-/-) mice abrogated HSC differentiation into NK cells thus confirming our in vitro findings. Collectively, these results demonstrate for the first time that activated Tregs can inhibit NK cell differentiation from HSC under specific conditions.

Expression levels of MHC class I molecules are inversely correlated with promiscuity of peptide binding

Highly polymorphic major histocompatibility complex (MHC) molecules are at the heart of adaptive immune responses, playing crucial roles in many kinds of disease and in vaccination. We report that breadth of peptide presentation and level of cell surface expression of class I molecules are inversely correlated in both chickens and humans. This relationship correlates with protective responses against infectious pathogens including Marek's disease virus leading to lethal tumours in chickens and human immunodeficiency virus infection progressing to AIDS in humans. We propose that differences in peptide binding repertoire define two groups of MHC class I molecules strategically evolved as generalists and specialists for different modes of pathogen resistance. We suggest that differences in cell surface expression level ensure the development of optimal peripheral T cell responses. The inverse relationship of peptide repertoire and expression is evidently a fundamental property of MHC molecules, with ramifications extending beyond immunology and medicine to evolutionary biology and conservation.

Harnessing regulatory T cells for clinical use in transplantation: the end of the beginning

Owing to the adverse effects of immunosuppression and an inability to prevent chronic rejection, there is a pressing need for alternative strategies to control alloimmunity. In three decades, regulatory T cells (Tregs) have evolved from a hypothetical mediator of adoptively transferred tolerance to a well-defined population that can be expanded ex vivo and returned safely to patients in clinical trials. Herein, we review the historical developments that have permitted these advances and the current status of clinical trials examining Tregs as a cellular therapy in transplantation. We conclude by discussing the critical unanswered questions that face this field in the coming years.

The minimum number of cord blood units needed for Koreans is 51,000

BACKGROUND

The inventory size for cord blood (CB) depends on the ethnic diversity of human leukocyte antigen (HLA) and the size estimation is important for public health in each ethnicity.

STUDY DESIGN AND METHODS

We estimate the CB inventory size in Koreans with stored CB units (CBUs) and patients who underwent allogeneic hematopoietic stem cell transplantation. Two-digit HLA specificities were determined using intermediate DNA typing. From 17,508 stored Korean CBUs, 1460 haplotypes with a frequency greater than 0.001% were used for reconstitution of the HLA. A total of 1002 transplanted patients' HLA was used for matching probability calculation.

RESULTS

The best probability for 6/6 matching is 47% in 500,000 hypothetical size. Ninety-five percent probability is achieved with 51,000 CBUs in 5/6, and 2150 in 4/6 matching condition. Because 4/6 matched CB is rarely selected in the Korean situation, 51,000 units is the lowest limit of CBUs required and the number will be adjusted depending on the cell number required for patients and the resolution of HLA typing.

CONCLUSION

Approximately 51,000 units could provide the minimum requirement for hematopoietic transplantation in Korea.

Multiple unit pooled umbilical cord blood is a viable source of therapeutic regulatory T cells

BACKGROUND

Regulatory T cells (Treg) are potentially a useful therapeutic option for the treatment of immunopathological conditions including graft-versus-host disease. Umbilical cord blood (UCB) offers certain advantages over adult peripheral blood (APB) as a source of Treg for cellular therapy but yields far fewer Treg per unit. Pooling of Treg from multiple donors may overcome this challenge.

METHODS

In this study, we assessed the in vitro and in vivo efficacy of multiple donor pooled UCB or APB-derived Treg.

RESULTS

In vitro, pooled freshly isolated UCB-derived Treg were as suppressive as APB-derived Treg. However, in a mouse model of human skin allodestruction, pooled UCB-derived Treg were more potent at suppressing alloresponses and prolonging skin survival compared with pooled APB-derived Treg. Improved survival of UCB Treg in an in vivo cell survival assay and their lower expression of human leukocyte antigen-ABC suggested that lower immunogenicity may account for their superior efficacy in vivo.

CONCLUSION

Multiple-unit UCB is therefore a viable source of human Treg for cellular therapy, and pooling of Treg from multiple donors offers a useful strategy for achieving required therapeutic doses.

CD4+CD25highCD127low regulatory T cells in peripheral blood are not an independent factor for chronic graft-versus-host disease after allogeneic stem cell transplantation

Background. The therapeutic efficacy of allogeneic hemopoietic stem cell transplantation (HSCT) largely relies on the graft-versus-leukemia (GVL) effect. Uncontrolled graft-versus-host disease (GVHD) is a feared complication of HSCT. Regulatory T cells (Treg) are a subset of CD4+ T-helper cells believed to maintain tolerance after HSCT. It remains unclear whether low peripheral blood Treg have an impact on the risk for acute (aGVHD) and chronic GVHD (cGVHD). Methods. In this paper we enumerated the CD4+CD25highCD127low Treg in the peripheral blood of 84 patients after at least 150 days from HSCT and in 20 healthy age-matched controls. Results. Although similar mean lymphocyte counts were found in patients and controls, CD3+CD4+ T-cell counts were significantly lower in patients. Patients also had significantly lower Treg percentages among lymphocytes as compared to controls. Patients with cGVHD had even higher percentages of Treg if compared to patients without cGVHD. In multivariate analysis, Treg percentages were not an independent factor for cGVHD. Conclusions. This paper did not show a relation between deficient peripheral blood Treg and cGVHD, therefore cGVHD does not seem to occur as a result of peripheral Treg paucity.

Mesenchymal stem cells: mechanisms of inflammation

In adults, human mesenchymal stem cells (hMSCs) are found in vivo at low frequency and are defined by their capacity to differentiate into bone, cartilage, and adipose tissue, depending on the stimuli and culture conditions under which they are expanded. Although MSCs were initially hypothesized to be the panacea for regenerating tissues, MSCs appear to be more important in therapeutics to regulate the immune response invoked in settings such as tissue injury, transplantation, and autoimmunity. MSCs have been used therapeutically in clinical trials and subsequently in practice to treat graft-versus-host disease following bone marrow transplantation. Reports of successful immune modulation suggest efficacy in a wide range of autoimmune conditions, such as demyelinating neurological disease (multiple sclerosis), systemic lupus erythematosus, and Crohn's disease, among others. This review provides background information about hMSCs and also describes their putative mechanisms of action in inflammation. We provide a summary of ongoing clinical trials to allow (a) full comprehension of the range of diseases in which hMSC therapy may be beneficial and (b) identification of gaps in our knowledge about the mechanisms of action of therapeutic MSCs in disease.