Comparison of regulatory T cells in hemodialysis patients and healthy controls: implications for cell therapy in transplantation

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.

Multiple infusions of ex vivo-expanded regulatory T cells promote CD163+ myeloid cells and kidney allograft survival in non-lymphodepleted non-human primates

Clinical verification of adoptively transferred regulatory T cell (Treg) efficacy in transplantation remains challenging. Here, we examined the influence of autologous ex vivo-expanded polyclonal Tregs on kidney graft survival in a clinically relevant non-human primate model. Peripheral blood Tregs were isolated and expanded using artificial antigen presenting cells. Immunosuppression was comprised of tapered tacrolimus and CTLA4 immunoglobulin, in five animals each without or with Treg infusions. Escalating Treg doses were administered 6, 10, 13, 16, 20, 23, 27 and 30 days after transplant. Infused Tregs were monitored for Treg signature, anti-apoptotic (Bcl-2) and proliferation (Ki67) marker expression. Treg infusions prolonged median graft survival time significantly from 35 to 70 days. Treg marker (Ki67 and Bcl-2) expression by infused Tregs diminished after their infusion but remained comparable to that of circulating native Tregs. No major changes in circulating donor-reactive T cell responses or total Treg percentages, or in graft-infiltrating T cell subsets were observed with Treg infusion. However, Treg infusion was associated with significant increases in CD163 expression by circulating HLA-DR+ myeloid cells and elevated levels of circulating soluble CD163. Further, graft-infiltrating CD163+ cells were increased with Treg infusion. Thus, multiple Treg infusions were associated with M2-like myeloid cell enhancement that may mediate immunomodulatory, anti-inflammatory and graft reparative effects.

Assoziation zwischen chronischer Nierenerkrankung und dem Risiko für bullöses Pemphigoid: eine nationale bevölkerungsbasierte Kohortenstudie

Hintergrund

Studien haben gezeigt, dass das bullöse Pemphigoid (BP) auch bei Patienten mit chronischer Nierenerkrankung (CKD, chronic kidney disease) auftritt. Unklar ist, wie hoch das BP‐Risiko bei CKD‐Patienten ist.

Zielsetzung

Es sollte untersucht werden, ob eine CKD das BP‐Risiko erhöht.

Methodik

Die Studienteilnehmer wurden für den Zeitraum von 2007 bis 2018 aus der nationalen Datenbank der taiwanesischen Krankenversicherung rekrutiert. Insgesamt wurden 637 664 neu diagnostizierte Patienten mit CKD sowie 637 664 nach Alter, Geschlecht und Komorbidität übereinstimmende Kontrollpersonen ohne CKD in die Untersuchung aufgenommen. Zur Bewertung des BP‐Risikos kam ein Modell für konkurrierende Risiken zum Einsatz.

Ergebnisse

Nach Adjustierung für Alter, Geschlecht und Komorbidität im multivariaten Modell zeigte sich die CKD als signifikanter Risikofaktor für BP (adjustierte Hazard Ratio [aHR]: 1,29; 95%‐Konfidenzintervall [KI]: 1,17–1,42; p < 0,001). CKD‐Patienten wurden in die Gruppen dialysepflichtig und nicht‐dialysepflichtig unterteilt und mit den Patienten ohne CKD verglichen. Es zeigte sich, dass dialysepflichtige CKD‐Patienten das höchste BP‐Risiko aufwiesen (aHR 1,75; 95%‐KI 1,51–2,03), gefolgt von nicht‐dialysepflichtigen CKD‐Patienten (aHR 1,20; 95%‐KI 1,08–1,32).

Limitationen

Detaillierte Laborbefunde zur Einschätzung des CKD‐Schweregrads fehlten.

Schlussfolgerungen

Im Vergleich zu Personen ohne CKD hatten Patienten mit CKD ein 1,3‐fach erhöhtes BP‐Risiko. Bei Patienten mit dialysepflichtiger CKD war das Risiko 1,8‐fach erhöht.

Association between chronic kidney disease and risk of bullous pemphigoid: a nationwide population-based cohort study

BACKGROUND

Studies have shown that bullous pemphigoid (BP) occurs in patients with chronic kidney disease (CKD). However, the risk of developing BP in patients with CKD remains inconclusive.

OBJECTIVE

To investigate whether CKD increases the risk of BP.

METHODS

Participants were recruited from the National Health Insurance Database of Taiwan between 2007 and 2018. Overall, 637,664 newly diagnosed patients with CKD and 637,664 age-, sex-, and comorbidity-matched non-CKD participants were selected. A competing risk model was used to evaluate the risk of development of BP.

RESULTS

After adjusting for age, sex, and comorbid diseases in the multivariate model, CKD was a significant risk factor for BP (adjusted hazard ratio [aHR]: 1.29; 95% confidence interval [CI]: 1.17-1.42; p < 0.001). CKD patients were classified into the dialytic or non-dialytic groups and compared to non-CKD participants, and this revealed that patients with dialysis-dependent CKD had the highest risk of BP (aHR 1.75; 95% CI 1.51-2.03), followed by patients with non-dialysis-dependent CKD (aHR 1.20; 95% CI 1.08-1.32).

LIMITATIONS

We lacked detailed laboratory data on the severity of CKD.

CONCLUSIONS

Compared with individuals without CKD, those with CKD had a 1.3-fold increased risk of BP. Patients with dialysis-dependent CKD had an even higher BP risk (1.8-fold).

Enhancing Regulatory T Cells to Treat Inflammatory and Autoimmune Diseases

Regulatory T cells (Tregs) control immune responses and are essential to maintain immune homeostasis and self-tolerance. Hence, it is no coincidence that autoimmune and chronic inflammatory disorders are associated with defects in Tregs. These diseases have currently no cure and are treated with palliative drugs such as immunosuppressant and immunomodulatory agents. Thereby, there is a great interest in developing medical interventions against these diseases based on enhancing Treg cell function and numbers. Here, we give an overview of Treg cell ontogeny and function, paying particular attention to mucosal Tregs. We review some notable approaches to enhance immunomodulation by Tregs with therapeutic purposes including adoptive Treg cell transfer therapy and discuss relevant clinical trials for inflammatory bowel disease. We next introduce ways to expand mucosal Tregs in vivo using microbiota and dietary products that have been the focus of clinical trials in various autoimmune and chronic-inflammatory diseases.

Operations Research to Solve Kidney Allocation Problems: A Systematic Review

BACKGROUND

Operations research techniques enable health care administrators to optimize resource allocation and to find solutions to staff and patient scheduling problems. We aimed to conduct the first systematic review of the international literature on the use of operations research for allocating deceased-donor kidneys.

METHODS

We searched the MEDLINE, EMBASE, and PubMed databases from inception to February 2023. Two reviewers independently screened the title/abstract and subsequently the full text of potentially eligible articles and abstracted the data. Quality assessment of the final set of studies was conducted using Subben's checklist.

RESULTS

Of the 302 citations identified, 5 studies were included. These studies covered three themes, including (1) provider-facing decision aids to determine the timing of transplant for single or multiple patients; (2) system-level planning on kidney allocation based on blood type matching rules; and (3) patient-facilitated wait times estimation using incomplete information. Markov models, sequential stochastic assignment models, and queuing models were amongst the most used techniques. Although we found all included studies to meet Subben's criteria, we believe the checklist in its current form lacks items to assess the validity of model inferences. As such, we ended this review with a set of practical recommendations.

CONCLUSIONS

Our review demonstrated the utility of operations research techniques in assisting the system, healthcare providers, and patients in the transplantation process. More research is needed to reach a consensus on a model that can be used to support the decision-making of different stakeholders for efficient kidney allocation, with the ultimate goal of reducing the gap between kidney supply and demand and enhancing the population's well-being.

Radiolabelling of Polyclonally Expanded Human Regulatory T Cells (Treg) with 89Zr-oxine for Medium-Term In Vivo Cell Tracking

Regulatory T cells (Tregs) are a promising candidate cell therapy to treat autoimmune diseases and aid the longevity of transplanted solid organs. Despite increasing numbers of clinical trials using human Treg therapy, important questions pertaining to their in vivo fate, distribution, and function remain unanswered. Treg accumulation in relevant tissues was found to be crucial for Treg therapy efficacy, but existing blood-borne biomarkers are unlikely to accurately reflect the tissue state. Non-invasive Treg tracking by whole-body imaging is a promising alternative and can be achieved by direct radiolabelling of Tregs and following the radiolabelled cells with positron emission tomography (PET). Our goal was to evaluate the radiolabelling of polyclonal Tregs with 89Zr to permit their in vivo tracking by PET/CT for longer than one week with current preclinical PET instrumentation. We used [89Zr]Zr(oxinate)4 as the cell-labelling agent and achieved successful radiolabelling efficiency of human Tregs spanning 0.1-11.1 Bq 89Zr/Treg cell, which would be compatible with PET tracking beyond one week. We characterized the 89Zr-Tregs, assessing their phenotypes, and found that they were not tolerating these intracellular 89Zr amounts, as they failed to survive or expand in a 89Zr-dose-dependent manner. Even at 0.1 Bq 89Zr per Treg cell, while 89Zr-Tregs remained functional as determined by a five-day-long effector T cell suppression assay, they failed to expand beyond day 3 in vitro. Moreover, PET imaging revealed signs of 89Zr-Treg death after adoptive transfer in vivo. In summary, 89Zr labelling of Tregs at intracellular radioisotope amounts compatible with cell tracking over several weeks did not achieve the desired outcomes, as 89Zr-Tregs failed to expand and survive. Consequently, we conclude that indirect Treg labelling is likely to be the most effective alternative method to satisfy the requirements of this cell tracking scenario.

The peripheral blood regulatory T-cells analysis as a criterion for assessing the therapy efficacy and a prognostic marker for the duration of remission of psoriasis

Background. The recently discovered regulatory T-cells CD4+CD25+FOXP3+CD127low (Treg-cells) plays an important role in sustaining immune tolerance. These cells demonstrated a significant tremendous potential in suppressing the pathological immune response associated with various autoimmune diseases, including psoriasis vulgaris (VP). Aims. To find the role of Treg-cells in VP pathogenesis and to show the possible use of the Treg-cells analysis for diagnosis, remission duration prediction and measurement of therapeutic effectiveness. Materials and methods. We studied 60 VP patients (35 females and 25 males) aged 1855. The patients were diagnosed with VP at advanced, remedial and retrogressive phases (28, 19 and 13 participants, respectively). The disease severity was assessed with the PASI (Psoriasis Area and Severity Index). The patients were stratified into two groups based on disease duration (less than 20 years, n = 42; over 20 years, n = 28). The study involved 12 VP patients in the advanced stage, whose Treg level was tested prior and after 311 nm UVB course. We followed up the VP patients for two years following the UVB-311 nm phototherapy course to assess the remission duration and the relapse frequency. Results. We found lower levels of Тreg in patients in the study group. Treg peripheral blood levels in VP patients and in HD were 2.84 1.00% and 4.02 0.73%, respectively. The Treg levels were 2.59 0.68%, 2.82 1.55% and 3.68 1.62% at advanced, remedial and retrogressive stages, respectively. The patients with the VP history less than 20 years demonstrated Treg level of 3.42 1.11% and 2.31 0.62% for patients with VP history over 20 years. We found an inverse correlation between the Treg subpopulation CD4+CD25+FOXP3+CD127low and the VP severity level evaluated with PASI (r = 0.39). The UVB-311 nm phototherapy resulted in the significant Treg level increase in 12 patients (2.11 0.61% and 3.43 1.02% prior and after therapy, respectively). Subsequently, we revealed the direct correlation (r = 0.88) between the Treg cell level increase in patients prior and after the phototherapy and the duration of remission in this group of the VP patients. Conclusions. We found decreased in Treg levels in VP patients compared to HD and revealed correlation between Treg-cells level in VP patients and VP phases, duration and the severity of the clinical picture. We demonstrated Treg feasibility as a laboratory indicator of VP therapy treatment with the example of 311 nm UVB and as a predict factor of remission duration.

Longitudinal monitoring of mRNA levels of regulatory T cell biomarkers by using non-invasive strategies to predict outcome in renal transplantation

BACKGROUND

Acute T-cell mediated rejection (aTCMR) is still an issue in kidney transplantation, for it is associated with chronic rejection, graft loss, and overall worse outcomes. For these reasons, a standard non-invasive molecular tool to detect is desirable to offer a simpler monitoring of kidney transplant recipients (KTRs). The purpose of our study was to examine, in peripheral blood before and after transplantation, the expression patterns of regulatory T cell (Treg)-related genes: the forkhead box P3 (FOXP3) and the two CTLA-4 isoforms (full-length and soluble) to predict acute rejection onset, de novo donor-specific antibodies (DSA) development and renal dysfunction 1 year after transplantation.

METHODS

We profiled by using a relative quantification analysis (qRT-PCR) circulating mRNA levels of these biomarkers in peripheral blood of 89 KTRs within the first post-transplant year (at baseline and 15, 60 and 365 days, and when possible at the acute rejection) and compared also the results with 24 healthy controls.

RESULTS

The three mRNA levels drastically reduced 15 days after transplantation and gradually recovered at 1 year in comparison with baseline, with very low levels at the time of aTCMR for FOXP3 (RQ = 0.445, IQR = 0.086-1.264, p = 0.040), maybe for the pro-apoptotic role of FOXP3 during inflammation. A multivariate Cox regression analysis evidenced a significant relation between aTCMR onset and thymoglobuline induction (HR = 6.749 p = 0.041), everolimus use (HR = 7.017, p = 0.007) and an increased risk from the solCTLA-4 expression at 15 days, mainly considering recipients treated with Mycophelolic acid (HR = 13.94 p = 0.038, 95%CI:1.157-167.87). Besides, solCTLA-4 also predisposed to graft dysfunction (eGFR< 60 mL/min/1.73m²) at 1 year (AOR = 3.683, 95%CI = 1.145-11.845, p = 0.029). On the other hand, pre-transplant solCTLA-4 levels showed a protective association with de novo DSAs development (HR = 0.189, 95%CI = 0.078-0.459, p < 0.001).

CONCLUSIONS

mRNA levels of Treg-associated genes, mainly for solCTLA-4, in peripheral blood could put forward as candidate non-invasive biomarkers of cellular and humoral alloreactivity in clinical transplantation and might help shape immunosuppression, tailor monitoring and achieve better long-term outcomes of kidney transplantation in the wake of "precision medicine".

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.

End stage renal disease has an early and continuous detrimental effect on regulatory T cells

End stage renal disease (ESRD) is followed by disturbed adaptive immunity, together with alterations in T cell subsets, including CD4+CD25+FoxP3+ cells (Tregs). In the present study, we assessed the effect of haemodialysis (HD) on the Treg population. CD3+CD4+, CD3+CD8+ and CD4+CD25+FoxP3+ cells were estimated by flow cytometry in 142 ESRD patients (45 ESRD-preHD, 97 on HD) and 30 healthy controls (HC). Patients on HD were classified into three groups according to time on dialysis (HD vintage - HDV): A < 2 years, B: 2-5 years and C: >5 years on HD. The mean age of patients on HD (M/F 53/44) was 54.8 ± 14 years and the median HDV 58 (78) months. We observed a significant progressive reduction in the percentage and count of lymphocytes (p < .001, p < .001, respectively), CD3+CD4+ (p = .003 and, p < .001, respectively) and Tregs (p = .001 and, p < .001, respectively), between HC, ESRD-preHD and HD patients. HDV had a significant inverse correlation with total lymphocyte, CD3+CD4+ and Treg cell counts (p = .001, p < .001, p < .001, respectively) and, the percentage of lymphocytes and CD3+CD4+ cells (p = .005, p = .01, respectively). Furthermore, we stratified patients on HD into three groups according to HDV: A < 2 years, B: 2-5 years and C: >5 years on HD. Total lymphocytes and Tregs were significantly different among the three vintage groups (Kruskal-Wallis H test, p < .001, p < .001 respectively). CD3+CD4+ and CD3+CD8+ cells were also significantly affected (p < .001 and p = .001, respectively), after at least 2 years of HD. Tregs show prompt and significant reduction at the pre-dialysis stage, and continue to decrease gradually even after long-term HD, in a context of total lymphocyte reduction.

The Association of Circulating CD14++CD16+ Monocytes, Natural Killer Cells and Regulatory T Cells Subpopulations With Phenotypes of Cardiovascular Disease in a Cohort of Peritoneal Dialysis Patients

The altered expression of immune cells including monocyte subsets, natural killer (NK) cells and CD4+CD25+ regulatory T cells (Tregs) in end-stage kidney disease, affect the modulation of inflammation and immunity with significant clinical implications. The aim of this study was to investigate the profile of specific immune cells subpopulations and their correlations with phenotypes of established cardiovascular disease (CVD), including coronary artery disease (CAD) and heart failure (HF) in peritoneal dialysis (PD) patients.

Materials and Methods: 29 stable PD patients and 13 healthy volunteers were enrolled. Demographic, laboratory, bioimpedance measurements, lung ultrasound and echocardiography data were collected. The peripheral blood immune cell subsets analysis was performed using flow cytometry.

Results: PD patients compared to normal controls had lower total lymphocytes (22.3 ± 6.28 vs. 31.3 ± 5.54%, p = <0.001) and B-lymphocytes (6.39 ± 3.75 vs. 9.72 ± 3.63%, p = 0.01) as well as higher CD14++CD16+ monocytes numbers (9.28 ± 6.36 vs. 4.75 ± 2.75%, p = 0.0002). PD patients with prevalent CAD had NK cells levels elevated above median values (85.7 vs. 40.9%, p = 0.04) and lower B cells counts (3.85 ± 2.46 vs. 7.2 ± 3.77%, p = 0.03). Patients with increased NK cells (>15.4%) had 3.8 times higher risk of CAD comparing with patients with lower NK cell levels (95% CI, 1.86 – 77.87; p = 0.034). B cells were inversely associated with the presence of CAD (increase of B-lymphocyte by 1% was associated with 30% less risk for presence of CAD (95% CI, −0.71 – 0.01; p = 0.05). Overhydrated patients had lower lymphocytes counts (18.3 ± 4.29% vs. 24.7 ± 6.18%, p = 0.006) and increased NK cells [20.5% (14.3, 23.6) vs. 13.21% (6.23, 19.2), p = 0.04)]. In multiple logistic regression analysis the CRP (OR 1.43; 95% CI, 1.00 – 2.05; p = 0.04)] and lymphocytes counts (OR 0.79; 95% CI, 0.63–0.99; p = 0.04)] were associated with the presence of lung comets. Patients with higher NK cells (>15.4%, n = 15) were more likely to be rapid transporters (D/P creatinine 0.76 ± 0.1 vs. 0.69 ± 0.08, p = 0.04). Patients displaying higher Tregs (>1.79%) were older (70.8 ± 10.7 years vs. 57.7 ± 14.7years, p = 0.011) and had higher nPCR (0.83 ± 0.14 vs. 0.91 ± 0.17, p = 0.09).

Conclusion: Future research is required to evaluate the role of immune cells subsets as potential tools to identify patients at the highest risk for complications and guide interventions.

Chimeric antigen receptor-modified human regulatory T cells that constitutively express IL-10 maintain their phenotype and are potently suppressive

Clinical trials of Treg therapy in transplantation are currently entering phases IIa and IIb, with the majority of these employing polyclonal Treg populations that harbor a broad specificity. Enhancing Treg specificity is possible with the use of chimeric antigen receptors (CARs), which can be customized to respond to a specific human leukocyte antigen (HLA). In this study, we build on our previous work in the development of HLA-A2 CAR-Tregs by further equipping cells with the constitutive expression of interleukin 10 (IL-10) and an imaging reporter as additional payloads. Cells were engineered to express combinations of these domains and assessed for phenotype and function. Cells expressing the full construct maintained a stable phenotype after transduction, were specifically activated by HLA-A2, and suppressed alloresponses potently. The addition of IL-10 provided an additional advantage to suppressive capacity. This study therefore provides an important proof-of-principle for this cell engineering approach for next-generation Treg therapy in transplantation.

Nox2-deficient Tregs improve heart transplant outcomes via their increased graft recruitment and enhanced potency

Nox2 is a ROS-generating enzyme, deficiency of which increases suppression by Tregs in vitro and in an in vivo model of cardiac remodeling. As Tregs have emerged as a candidate therapy in autoimmunity and transplantation, we hypothesized that Nox2 deficiency in Tregs in recipient mice may improve outcomes in a heart transplant model. We generated a potentially novel B6129 mouse model with Treg-targeted Nox2 deletion (Nox2fl/flFoxP3Cre+ mice) and transplanted with hearts from CB6F1 donors. As compared with those of littermate controls, Nox2fl/flFoxP3Cre+ mice had lower plasma levels of alloantibodies and troponin-I, reduced levels of IFN-γ in heart allograft homogenates, and diminished cardiomyocyte necrosis and allograft fibrosis. Single-cell analyses of allografts revealed higher absolute numbers of Tregs and lower CD8+ T cell infiltration in Nox2-deficient recipients compared with Nox2-replete mice. Mechanistically, in addition to a greater suppression of CD8+CD25- T effector cell proliferation and IFN-γ production, Nox2-deficient Tregs expressed higher levels of CCR4 and CCR8, driving cell migration to allografts; this was associated with increased expression of miR-214-3p. These data indicate that Nox2 deletion in Tregs enhances their suppressive ability and migration to heart allografts. Therefore, Nox2 inhibition in Tregs may be a useful approach to improve their therapeutic efficacy.

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.

Spatiotemporal in vivo tracking of polyclonal human regulatory T cells (Tregs) reveals a role for innate immune cells in Treg transplant recruitment

Regulatory T cells (Tregs) are emerging as a new cell-based therapy in solid organ transplantation. Adoptive transfer of Tregs has been shown preclinically to protect from graft rejection, and the safety of Treg therapy has been demonstrated in clinical trials. Despite these successes, the in vivo distribution and persistence of adoptively transferred Tregs remained elusive, which hampers clinical translation. Here we isolated human Tregs using a GMP-compatible protocol and lentivirally transduced them with the human sodium iodide symporter to render them traceable in vivo by radionuclide imaging. Engineered human Tregs were characterized for phenotype, survival, suppressive capacity, and reporter function. To study their trafficking behavior, they were subsequently administered to humanized mice with human skin transplants. Traceable Tregs were quantified in skin grafts by non-invasive nano-single-photon emission computed tomography (nanoSPECT)/computed tomography (CT) for up to 40 days, and the results were validated ex vivo. Using this approach, we demonstrated that Treg trafficking to skin grafts was regulated by the presence of recipient Gr-1+ innate immune cells. We demonstrated the utility of radionuclide reporter gene-afforded quantitative Treg in vivo tracking, addressing a fundamental need in Treg therapy development and offering a clinically compatible methodology for future Treg therapy imaging in humans.

Kidney Failure Associates With T Cell Exhaustion and Imbalanced Follicular Helper T Cells

Individuals with kidney failure are at increased risk of cardiovascular events, as well as infections and malignancies, but the associated immunological abnormalities are unclear. We hypothesized that the uremic milieu triggers a chronic inflammatory state that, while accelerating atherosclerosis, promotes T cell exhaustion, impairing effective clearance of pathogens and tumor cells. Clinical and demographic data were collected from 78 patients with chronic kidney disease (CKD) (n = 42) or end-stage kidney disease (ESKD) (n = 36) and from 18 healthy controls (HC). Serum cytokines were analyzed by Luminex. Immunophenotype of T cells was performed by flow cytometry on peripheral blood mononuclear cells. ESKD patients had significantly higher serum levels of IFN-γ, TNF-α, sCD40L, GM-CSF, IL-4, IL-8, MCP-1, and MIP-1β than CKD and HC. After mitogen stimulation, both CD4⁺ and CD8⁺ T cells in ESKD group demonstrated a pro-inflammatory phenotype with increased IFN-γ and TNF-α, whereas both CKD and ESKD patients had higher IL-2 levels. CKD and ESKD were associated with increased frequency of exhausted CD4⁺ T cells (CD4⁺KLRG1⁺PD1⁺CD57^-) and CD8⁺ T cells (CD8⁺KLRG1⁺PD1⁺CD57^-), as well as anergic CD4⁺ T cells (CD4⁺KLRG1^-PD1⁺CD57^-) and CD8⁺ T cells (CD8⁺KLRG1^-PD1⁺CD57^-). Although total percentage of follicular helper T cell (T_FH) was similar amongst groups, ESKD had reduced frequency of T_FH1 (CCR6^-CXCR3⁺CXCR5⁺PD1⁺CD4⁺CD8^-), but increased T_FH2 (CCR6^-CXCR3^-CXCR5⁺PD1⁺CD4⁺CD8^-), and plasmablasts (CD3^-CD56^-CD19⁺CD27^highCD38^highCD138^-). In conclusion, kidney failure is associated with pro-inflammatory markers, exhausted T cell phenotype, and upregulated T_FH2, especially in ESKD. These immunological changes may account, at least in part, for the increased cardiovascular risk in these patients and their susceptibility to infections and malignancies.

Machine learning for predicting long-term kidney allograft survival: a scoping review

Supervised machine learning (ML) is a class of algorithms that "learn" from existing input-output pairs, which is gaining popularity in pattern recognition for classification and prediction problems. In this scoping review, we examined the use of supervised ML algorithms for the prediction of long-term allograft survival in kidney transplant recipients. Data sources included PubMed, the Cumulative Index to Nursing and Allied Health Literature, and the Institute for Electrical and Electronics Engineers (IEEE) Xplore libraries from inception to November 2019. We screened titles and abstracts and potentially eligible full-text reports to select studies and subsequently abstracted the data. Eleven studies were identified. Decision trees were the most commonly used method (n = 8), followed by artificial neural networks (ANN) (n = 4) and Bayesian belief networks (n = 2). The area under receiver operating curve (AUC) was the most common measure of discrimination (n = 7), followed by sensitivity (n = 5) and specificity (n = 4). Model calibration examining the reliability in risk prediction was performed using either the Pearson r or the Hosmer-Lemeshow test in four studies. One study showed that logistic regression had comparable performance to ANN, while another study demonstrated that ANN performed better in terms of sensitivity, specificity, and accuracy, as compared with a Cox proportional hazards model. We synthesized the evidence related to the comparison of ML techniques with traditional statistical approaches for prediction of long-term allograft survival in patients with a kidney transplant. The methodological and reporting quality of included studies was poor. Our study also demonstrated mixed results in terms of the predictive potential of the models.

Non-invasive Reporter Gene Imaging of Cell Therapies, including T Cells and Stem Cells

Cell therapies represent a rapidly emerging class of new therapeutics. They are intended and developed for the treatment of some of the most prevalent human diseases, including cancer, diabetes, and for regenerative medicine. Currently, they are largely developed without precise assessment of their in vivo distribution, efficacy, or survival either clinically or preclinically. However, it would be highly beneficial for both preclinical cell therapy development and subsequent clinical use to assess these parameters in situ to enable enhancements in efficacy, applicability, and safety. Molecular imaging can be exploited to track cells non-invasively on the whole-body level and can enable monitoring for prolonged periods in a manner compatible with rapidly expanding cell types. In this review, we explain how in vivo imaging can aid the development and clinical translation of cell-based therapeutics. We describe the underlying principles governing non-invasive in vivo long-term cell tracking in the preclinical and clinical settings, including available imaging technologies, reporter genes, and imaging agents as well as pitfalls related to experimental design. Our emphasis is on adoptively transferred T cell and stem cell therapies.

HDAC6-specific inhibitor suppresses Th17 cell function via the HIF-1α pathway in acute lung allograft rejection in mice

Background: Previous animal experiments and clinical studies indicated the critical role of Th17 cells in lung transplant rejection. Therefore, the downregulation of Th17 cell function in lung transplant recipients is of great interest. Methods: We established an orthotopic mouse lung transplantation model to investigate the role of histone deacetylase 6-specific inhibitor (HDAC6i), Tubastatin A, in the suppression of Th17 cells and attenuation of pathologic lesions in lung allografts. Moreover, mechanism studies were conducted in vitro. Results: Tubastatin A downregulated Th17 cell function in acute lung allograft rejection, prolonged the survival of lung allografts, and attenuated acute rejection by suppressing Th17 cell accumulation. Consistently, exogenous IL-17A supplementation eliminated the protective effect of Tubastatin A. Also, hypoxia-inducible factor-1α (HIF-1α) was overexpressed in a lung transplantation mouse model. HIF-1α deficiency suppressed Th17 cell function and attenuated lung allograft rejection by downregulating retinoic acid-related orphan receptor γt (ROR γt) expression. We showed that HDAC6i downregulated HIF-1α transcriptional activity under Th17-skewing conditions in vitro and promoted HIF-1α protein degradation in lung allografts. HDAC6i did not affect the suppression of HIF-1α^-/- naïve CD4⁺ T cell differentiation into Th17 cell and attenuation of acute lung allograft rejection in HIF-1α-deficient recipient mice. Conclusion: These findings suggest that Tubastatin A downregulates Th17 cell function and suppresses acute lung allograft rejection, at least partially, via the HIF-1α/ RORγt pathway.

How Non-invasive in vivo Cell Tracking Supports the Development and Translation of Cancer Immunotherapies

Immunotherapy is a relatively new treatment regimen for cancer, and it is based on the modulation of the immune system to battle cancer. Immunotherapies can be classified as either molecular or cell-based immunotherapies, and both types have demonstrated promising results in a growing number of cancers. Indeed, several immunotherapies representing both classes are already approved for clinical use in oncology. While spectacular treatment successes have been reported, particularly for so-called immune checkpoint inhibitors and certain cell-based immunotherapies, they have also been accompanied by a variety of severe, sometimes life-threatening side effects. Furthermore, not all patients respond to immunotherapy. Hence, there is the need for more research to render these promising therapeutics more efficacious, more widely applicable, and safer to use. Whole-body in vivo imaging technologies that can interrogate cancers and/or immunotherapies are highly beneficial tools for immunotherapy development and translation to the clinic. In this review, we explain how in vivo imaging can aid the development of molecular and cell-based anti-cancer immunotherapies. We describe the principles of imaging host T-cells and adoptively transferred therapeutic T-cells as well as the value of traceable cancer cell models in immunotherapy development. Our emphasis is on in vivo cell tracking methodology, including important aspects and caveats specific to immunotherapies. We discuss a variety of associated experimental design aspects including parameters such as cell type, observation times/intervals, and detection sensitivity. The focus is on non-invasive 3D cell tracking on the whole-body level including aspects relevant for both preclinical experimentation and clinical translatability of the underlying methodologies.

Propionate supplementation promotes the expansion of peripheral regulatory T-Cells in patients with end-stage renal disease

Patients with end-stage renal disease (ESRD) suffer from a progressively increasing low-grade systemic inflammation, which is associated with higher morbidity and mortality. Regulatory T cells (Tregs) play an important role in regulation of the inflammatory process. Previously, it has been demonstrated that short-chain fatty acids reduce inflammation in the central nervous system in a murine model of multiple sclerosis through an increase in tissue infiltrating Tregs. Here, we evaluated the effect of the short-chain fatty acid propionate on the chronic inflammatory state and T-cell composition in ESRD patients. Analyzing ESRD patients and healthy blood donors before, during, and 60 days after the propionate supplementation by multiparametric flow cytometry we observed a gradual and significant expansion in the frequencies of CD25^highCD127^- Tregs in both groups. Phenotypic characterization suggests that polarization of naïve T cells towards Tregs is responsible for the observed expansion. In line with this, we observed a significant reduction of inflammatory marker CRP under propionate supplementation. Of interest, the observed anti-inflammatory surroundings did not affect the protective pathogen-specific immunity as demonstrated by the stable frequencies of effector/memory T cells specific for tetanus/diphtheria recall antigens. Collectively, our data suggest that dietary supplements with propionate have a beneficial effect on the elevated systemic inflammation of ESRD patients. The effect can be achieved through an expansion of circulating Tregs without affecting the protective pathogen-reactive immunity.

Chronic Hepatitis C Infection Has No Effect on Peripheral CD4+CD25+ Tregulatory Cells in Patients with End-Stage Renal Disease

Background: T regulatory cells (Tregs), through variable mechanisms, play a crucial role in Hepatitis C virus (HCV) chronicity and infection tolerance. A great speculation is posed regarding the level, role of Tregs in end-stage renal disease (ESRD), and the presence of associated factors that could influence the Tregs population. Accordingly, we aimed at studying the effect of HCV infection on peripheral CD4⁺CD25⁺Tregs population among patients on hemodialysis (HD) as well as the effect of other comorbidities on these cells.Patients and methods: A group of 77 patients on HD (32 were HD HCV⁺ and 45 were HD HCV^-) and 80 healthy controls (HCs) were included in the study. Flow cytometric analysis was performed for identification and quantification of peripheral CD4⁺ CD25⁺Tregs.Results: The frequency of CD4⁺ CD25⁺Tregs increased significantly in HD patients compared to the HCs (p = <.0001 each). HCV posed no effect on peripheral CD4+ CD25+ Tregs in ESRD patients, when comparing HD HCV- and HD HCV+ groups. In the hypertensive HD HCV-, Tregs percentage was higher than that in the non-hypertensive. However, the difference was not statistically significant. No significant difference was detected between HD HCV- and HD HCV+ patients on the count and percentages of Tregs according to the duration of dialysis.Conclusion: Demonstrating that chronic HCV infection has no effect on CD4+ CD25+ Tregs cells levels in ESRD patients is of great importance to the success of future allografts in such patients.

Next-generation regulatory T cell therapy

Regulatory T cells (Treg cells) are a small subset of immune cells that are dedicated to curbing excessive immune activation and maintaining immune homeostasis. Accordingly, deficiencies in Treg cell development or function result in uncontrolled immune responses and tissue destruction and can lead to inflammatory disorders such as graft-versus-host disease, transplant rejection and autoimmune diseases. As Treg cells deploy more than a dozen molecular mechanisms to suppress immune responses, they have potential as multifaceted adaptable smart therapeutics for treating inflammatory disorders. Indeed, early-phase clinical trials of Treg cell therapy have shown feasibility, tolerability and potential efficacy in these disease settings. In the meantime, progress in the development of chimeric antigen receptors and in genome editing (including the application of CRISPR-Cas9) over the past two decades has facilitated the genetic optimization of primary T cell therapy for cancer. These technologies are now being used to enhance the specificity and functionality of Treg cells. In this Review, we describe the key advances and prospects in designing and implementing Treg cell-based therapy in autoimmunity and transplantation.

Protease Activated Receptor 4 as a Novel Modulator of Regulatory T Cell Function

Regulatory T cells (Tregs) are a subpopulation of T cells that maintain immunological tolerance. In inflammatory responses the function of Tregs is tightly controlled by several factors including signaling through innate receptors such as Toll like receptors and anaphylatoxin receptors allowing an effective immune response to be generated. Protease-activated receptors (PARs) are another family of innate receptors expressed on multiple cell types and involved in the pathogenesis of autoimmune disorders. Whether proteases are able to directly modulate Treg function is unknown. Here, we show using two complimentary approaches that signaling through PAR-4 influences the expression of CD25, CD62L, and CD73, the suppressive capacity, and the stability of Tregs, via phosphorylation of FoxO1 and negative regulation of PTEN and FoxP3. Taken together, our results demonstrate an important role of PAR4 in tuning the function of Tregs and open the possibility of targeting PAR4 to modulate immune responses.

Correction of Defective T-Regulatory Cells From Patients With Crohn's Disease by Ex Vivo Ligation of Retinoic Acid Receptor-α

BACKGROUND & AIMS

Crohn's disease (CD) is characterized by an imbalance of effector and regulatory T cells in the intestinal mucosa. The efficacy of anti-adhesion therapies led us to investigate whether impaired trafficking of T-regulatory (Treg) cells contributes to the pathogenesis of CD. We also investigated whether proper function could be restored to Treg cells by ex vivo expansion in the presence of factors that activate their regulatory activities.

METHODS

We measured levels of the integrin α4β7 on Treg cells isolated from peripheral blood or lamina propria of patients with CD and healthy individuals (controls). Treg cells were expanded ex vivo and incubated with rapamycin with or without agonists of the retinoic acid receptor-α (RARA), and their gene expression profiles were analyzed. We also studied the cells in cytokine challenge, suppression, and flow chamber assays and in SCID mice with human intestinal xenografts.

RESULTS

We found that Treg cells from patients with CD express lower levels of the integrin α4β7 than Treg cells from control patients. The pathway that regulates the expression of integrin subunit α is induced by retinoic acid (RA). Treg cells from patients with CD incubated with rapamycin and an agonist of RARA (RAR568) expressed high levels of integrin α4β7, as well as CD62L and FOXP3, compared with cells incubated with rapamycin or rapamycin and all-trans retinoic acid. These Treg cells had increased suppressive activities in assays and migrated under conditions of shear flow; they did not produce inflammatory cytokines, and RAR568 had no effect on cell stability or lineage commitment. Fluorescently labeled Treg cells incubated with RAR568 were significantly more likely to traffic to intestinal xenografts than Treg cells expanded in control medium.

CONCLUSIONS

Treg cells from patients with CD express lower levels of the integrin α4β7 than Treg cells from control patients. Incubation of patients' ex vivo expanded Treg cells with rapamycin and an RARA agonist induced expression of α4β7 and had suppressive and migratory activities in culture and in intestinal xenografts in mice. These cells might be developed for treatment of CD. ClinicalTrials.gov, Number: NCT03185000.

Aging and End Stage Renal Disease Cause A Decrease in Absolute Circulating Lymphocyte Counts with A Shift to A Memory Profile and Diverge in Treg Population

There is a growing number of elderly kidney transplant (Ktx) recipients. Elderly recipients present lower acute rejection rates but higher incidence of infection and malignancies. Aging per se seems to result in a shift to memory profile and chronic kidney disease (CKD) in premature immunological aging. Understanding aging and CKD effects on the immune system can improve elderly Ktx immunosuppression. We analyzed the effects of aging and CKD in the immune system, comparing healthy adults (HAd) (n=14, 26±2y), healthy elderly (HEld) (n=15, 79±7y), end stage renal disease (ESRD) adults (EnAd) (n=18, 36±7y) and ESRD elderly (EnEld) (n=31, 65±3y) prior to Ktx regarding their naïve, memory and regulatory T and B peripheral lymphocytes. Aging and ESRD presented additive effect decreasing absolute numbers of B and T-lymphocytes, affecting memory, naive and regulatory subsets without synergic effect. Both resulted in higher percentages of T memory subsets and opposing effects on regulatory T (TREG) subsets, higher percentage in aging and lower in ESRD. Combined effect of aging and ESRD also resulted in higher regulatory B cell percentages. In addition to global lymphopenia and TCD4⁺ memory shift in both aging and ESRD, aging shifts to an immunoregulatory profile, inducing a increase in TREG percentages, contrasting with ESRD that decreases TREGs. Differential immunosuppression regimens for elderly Ktx may be required. (ClinicalTrials.gov number: NTC01631058).

Transient increase of activated regulatory T cells early after kidney transplantation

Regulatory T cells (Tregs) are crucial in controlling allospecific immune responses. However, studies in human kidney recipients regarding the contribution of polyspecific Tregs have provided differing results and studies on alloreactive Tregs are missing completely. In this retrospective study, we specifically analyzed activated CD4⁺CD25^highFOXP3⁺GARP⁺ Tregs in 17 patients of a living donor kidney transplantation cohort longitudinally over 24 months by flow cytometry (FOXP3: forkhead box protein 3, GARP: glycoprotein A repetitions predominant). We could demonstrate that Tregs of patients with end-stage renal disease (ESRD) are already pre-activated when compared to healthy controls. Furthermore, even though total CD4⁺CD25^highFOXP3⁺ Treg numbers decreased in the first three months after transplantation, frequency of activated Tregs increased significantly representing up to 40% of all peripheral Tregs. In a cohort of living donor kidney transplantation recipients with stable graft function, frequencies of activated Tregs did not correlate with the occurrence of acute cellular rejection or chronic graft dysfunction. Our results will be important for clinical trials using adoptive Treg therapy after kidney transplantation. Adoptively transferred Tregs could be important to compensate the Treg loss at month 3, while they have to compete within the Treg niche with a large number of activated Tregs.

Would hemodialysis patients benefit from a Staphylococcus aureus vaccine?

Staphylococcus aureus bloodstream infection can have potentially catastrophic consequences for patients on hemodialysis. Consequently, an effective vaccine to prevent S aureus infection would have a significant influence on morbidity and mortality in this group. To date, however, efforts to develop a vaccine have been unsuccessful. Previous antibody-inducing vaccine candidates did not prevent or attenuate S aureus infection in clinical trials. Recent advances have helped to elucidate the role of specific T-cell subsets, notably T-helper cell 1 and T-helper cell 17, in the immune response to S aureus. These cells are essential for coordinating an effective phagocytic response via cytokine production, indirectly leading to destruction of the organism. It is now widely accepted that next-generation S aureus vaccines must also induce effective T-cell-mediated immunity. However, there remains a gap in our knowledge: how will an S aureus vaccine drive these responses in those patients most at risk? Given that patients on hemodialysis are an immunocompromised population, in particular with specific T-cell defects, including defects in T-helper cell subsets, this is likely to affect their ability to respond to an S aureus vaccine. We urgently need a better understanding of T-cell-mediated immunity in this cohort if an efficacious vaccine is ever to be realized for these patients.

Ex vivo expanded natural regulatory T cells from patients with end-stage renal disease or kidney transplantation are useful for autologous cell therapy

Novel concepts employing autologous, ex vivo expanded natural regulatory T cells (nTreg) for adoptive transfer has potential to prevent organ rejection after kidney transplantation. However, the impact of dialysis and maintenance immunosuppression on the nTreg phenotype and peripheral survival is not well understood, but essential when assessing patient eligibility. The current study investigates regulatory T-cells in dialysis and kidney transplanted patients and the feasibility of generating a clinically useful nTreg product from these patients. Heparinized blood from 200 individuals including healthy controls, dialysis patients with end stage renal disease and patients 1, 5, 10, 15, 20 years after kidney transplantation were analyzed. Differentiation and maturation of nTregs were studied by flow cytometry in order to compare dialysis patients and kidney transplanted patients under maintenance immunosuppression to healthy controls. CD127 expressing CD4⁺CD25^highFoxP3⁺ nTregs were detectable at increased frequencies in dialysis patients with no negative impact on the nTreg end product quality and therapeutic usefulness of the ex vivo expanded nTregs. Further, despite that immunosuppression mildly altered nTreg maturation, neither dialysis nor pharmacological immunosuppression or previous acute rejection episodes impeded nTreg survival in vivo. Accordingly, the generation of autologous, highly pure nTreg products is feasible and qualifies patients awaiting or having received allogenic kidney transplantation for adoptive nTreg therapy. Thus, our novel treatment approach may enable us to reduce the incidence of organ rejection and reduce the need of long-term immunosuppression.

Human retinoic acid-regulated CD161+ regulatory T cells support wound repair in intestinal mucosa

Repair of tissue damaged during inflammatory processes is key to the return of local homeostasis and restoration of epithelial integrity. Here we describe CD161⁺ regulatory T (T_reg) cells as a distinct, highly suppressive population of T_reg cells that mediate wound healing. These T_reg cells were enriched in intestinal lamina propria, particularly in Crohn's disease. CD161⁺ T_reg cells had an all-trans retinoic acid (ATRA)-regulated gene signature, and CD161 expression on T_reg cells was induced by ATRA, which directly regulated the CD161 gene. CD161 was co-stimulatory, and ligation with the T cell antigen receptor induced cytokines that accelerated the wound healing of intestinal epithelial cells. We identified a transcription-factor network, including BACH2, RORγt, FOSL2, AP-1 and RUNX1, that controlled expression of the wound-healing program, and found a CD161⁺ T_reg cell signature in Crohn's disease mucosa associated with reduced inflammation. These findings identify CD161⁺ T_reg cells as a population involved in controlling the balance between inflammation and epithelial barrier healing in the gut.

The Potential of In Vivo Imaging for Optimization of Molecular and Cellular Anti-cancer Immunotherapies

This review aims to emphasize the potential of in vivo imaging to optimize current and upcoming anti-cancer immunotherapies: spanning from preclinical to clinical applications. Immunotherapies are an emerging class of treatments for a variety of diseases. The agents include molecular and cellular therapeutics, which aim to treat the disease through re-education of the host immune system, often via complex mechanisms of action. In vivo imaging has the potential to contribute in several different ways: (1) as a drug development tool to improve our understanding of their complex mechanisms of action, (2) as a tool to predict efficacy, for example, to stratify patients into probable responders and likely non-responders, and (3) as a non-invasive treatment response biomarker to guide efficient immunotherapy use and to recognize early signs of potential loss of efficacy or resistance in patients. Areas where in vivo imaging is already successfully implemented in onco-immunology research will be discussed and domains where its use offers great potential will be highlighted. The focus of this article is on anti-cancer immunotherapy as it currently is the most advanced immunotherapy area. However, the described concepts can also be paralleled in other immune-mediated disorders and for conditions requiring immunotherapeutic intervention. Importantly, we introduce a new study group within the European Society of Molecular Imaging with the goal to facilitate and enhance immunotherapy development through the use of in vivo imaging.

Peripheral Blood Regulatory T Cells Are Diminished in Kidney Transplant Patients With Chronic Allograft Nephropathy

BACKGROUND

Our aim in this study was to assess peripheral blood CD4⁺CD25⁺FOXP3⁺ regulatory T cell (Treg) levels in patients with chronic allograft nephropathy (CAN) 1 year after kidney transplantation.

METHODS

Twelve renal transplant patients with an initial onset of CAN, 12 patients with chronic kidney disease (CKD) stage G5 on dialysis, and 13 healthy control individuals were evaluated regarding the proportion of Tregs in their peripheral blood via flow cytometry.

RESULTS

The renal transplant patients with CAN had a significantly lower proportion of Tregs than the hemodialysis CKD patients and healthy controls (P < .0001). In contrast, the hemodialysis CKD patients showed higher levels of Tregs than the renal transplant patients with CAN and the healthy controls (P < .0001).

CONCLUSION

The high level of peripheral blood Tregs in the hemodialysis CKD patients suggests a chronic inflammatory state. However, the low frequency of Tregs in the peripheral blood from the renal transplant patients with CAN suggests an unfavorable prognosis for allograft immune tolerance.

Cell Therapy in Organ Transplantation: Our Experience on the Clinical Translation of Regulatory T Cells

Solid organ transplantation is the treatment of choice for patients with end-stage organ dysfunction. Despite improvements in short-term outcome, long-term outcome is suboptimal due to the increased morbidity and mortality associated with the toxicity of immunosuppressive regimens and chronic rejection (1–5). As such, the attention of the transplant community has focused on the development of novel therapeutic strategies to achieve allograft tolerance, a state whereby the immune system of the recipient can be re-educated to accept the allograft, averting the need for long-term immunosuppression. Indeed, reports of “operational” tolerance, whereby the recipient is off all immunosuppressive drugs and maintaining good graft function, is well documented in the literature for both liver and kidney transplantations (6–8). However, this phenomenon is rare and in the setting of liver transplantation has been shown to occur late after transplantation, with the majority of patients maintained on life-long immunosupression to prevent allograft rejection (9). As such, significant research has focused on immune regulation in the context of organ transplantation with regulatory T cells (Tregs) identified as cells holding considerable promise in this endeavor. This review will provide a brief introduction to human Tregs, their phenotypic and functional characterization and focuses on our experience to date at the clinical translation of Treg immunotherapy in the setting of solid organ transplantation.

A Rapamycin-Based GMP-Compatible Process for the Isolation and Expansion of Regulatory T Cells for Clinical Trials

The concept of regulatory T cell (Treg)-based immunotherapy has enormous potential for facilitating tolerance in autoimmunity and transplantation. Clinical translation of Treg cell therapy requires production processes that satisfy the rigors of Good Manufacturing Practice (GMP) standards. In this regard, we report our findings on the implementation of a robust GMP compliant process for the ex vivo expansion of clinical grade Tregs, demonstrating the feasibility of this developed process for the manufacture of a final product for clinical application. This Treg isolation procedure ensured the selection of a pure Treg population that underwent a 300-fold expansion after 36 days of culture, while maintaining a purity of more than 75% CD4⁺CD25⁺FOXP3⁺ cells and a suppressive function of above 80%. Furthermore, we report the successful cryopreservation of the final product, demonstrating the maintenance of phenotype and function. The process outlined in this manuscript has been implemented in the ONE study, a multicenter phase I/IIa clinical trial in which cellular therapy is investigated in renal transplantation.

The role of age-related T-cell differentiation in patients with renal replacement therapy

Dialysis patients have deficiencies regarding the generation of immune responses and show an increased susceptibility for infections. Persisting uremic conditions are made responsible for the increased aging of their immune system. In this study, we analyzed whether age-related differences in the differentiation of both recent-thymic-emigrant-(RTE)-regulatory (Tregs) and RTE-responder T cells (Tresps) into CD31^--memory Tregs/Tresps led to differences in the suppressive activity of naive and memory Tregs on autologous Tresps between healthy volunteers and dialysis patients. We found that regardless of age, the differentiation of RTE-Treg/Tresps into CD31^--memory-Treg/Tresps was significantly increased in dialysis patients. By analyzing the age-related differences in the differentiation of Tregs/Tresps, we saw that in healthy volunteers RTE-Tregs differentiate via CD31⁺-memory Tregs into CD31^--memory Tregs, which may strengthen the suppressive activity of the total Treg pool. In contrast RTE-Tresps of healthy volunteers differentiate via mature naive (MN)-Tresps into CD31^--memory-Tresps, which may weaken the reactivity of the total Tresp pool. Our data revealed that this normal differentiation via MN-Tresps was lost in dialysis patients, suggesting that their Tresps are less sensitive to Treg-mediated immunosuppression. Functional analysis of Tregs on autologous Tresps showed an increasing suppressive activity with age in healthy individuals, who therefore may have a lower risk of developing autoimmune diseases but owing to decreased reactivity of their Tresps are more likely to suffer from infections. In contrast, dialysis patients exhibited a decreasing suppressive activity with age, owing to strengthened Tresp reactivity, which could explain the higher prevalence of chronic inflammatory conditions in these patients.

CD45RA Distinguishes CD4+CD25+CD127-/low TSDR Demethylated Regulatory T Cell Subpopulations With Differential Stability and Susceptibility to Tacrolimus-Mediated Inhibition of Suppression

Background

Adoptive transfer of forkhead box protein (FOX)3⁺ regulatory T (Treg) cells offers a promising strategy to reduce damage to an allograft by the recipient's immune system. Identification of cell surface markers sufficient to purify Treg cells expanded ex vivo to remove cellular contaminants requires optimization. Furthermore, the expanded Treg must be able to survive, expand, and suppress in allograft recipients exposed to immunosuppressants, such as tacrolimus (TAC). Reduced CD127 expression enhances identification of Treg in the human CD4⁺CD25⁺ population. CD45RA expression identifies naive CD4⁺CD25⁺ Treg with an enhanced stability of Treg phenotype.

Methods

We combine an analysis of CD45RA, CD25, and CD127 expression to identify subpopulations of CD4⁺CD127^−/loCD25⁺ cells. Regulatory T cells were sorted according to expression of CD25 and CD45RA and expanded in the presence of a physiological relevant concentration of TAC. Regulatory T cell–specific demethylation region (TSDR) demethylation, FOXP3 expression, and suppression were analyzed.

Results

CD4⁺CD127^−/loCD25⁺CD45RA⁺ Treg cells had a stable TSDR demethylated FOXP3⁺ phenotype after expansion whereas CD4⁺CD127^lo/−CD25⁺CD45RA⁻ Treg cell lost the TSDR demethylated phenotype. CD45RA⁻ Treg had a greater capacity to suppress after expansion with TAC.

Conclusions

Although CD45RA⁻ Treg retained a greater suppressive capacity when expanded with TAC, the marked loss of the TSDR demethylated status highlights the potential for loss of stability of these cells in transplant recipients treated with TAC based immunosuppression. We show that a population of CD4⁺CD127^−/loCD45RA⁺ Regulatory T cell may offer the best compromise between susceptibility to loss of suppression when exposed to TAC and maintenance of a TSDR demethylated phenotype following in vitro expansion.

Following in vitro expansion with tacrolimus, CD4+CD127-/loCD25+CD45RA- Treg had a greater suppressive capacity vs the CD45RA+ counterpart Treg. Nevertheless, CD45RA+ Treg had a more stable TSDR demethylated FOXP3+ phenotype vs the CD45RA- Treg counterpart. CD4+CD127-/loCD25+CD45RA+ Treg offer the best compromise following expansion. Supplemental digital content is available in the text.

Regulatory T cells: tolerance induction in solid organ transplantation

The concept of regulatory T cell (T_reg ) therapy in transplantation is now a reality. Significant advances in science and technology have enabled us to isolate human T_regs , expand them to clinically relevant numbers and infuse them into human transplant recipients. With several Phase I/II trials under way investigating T_reg safety and efficacy it is now more crucial than ever to understand their complex biology. However, our journey is by no means complete; results from these trials will undoubtedly provoke both further knowledge and enquiry which, alongside evolving science, will continue to drive the optimization of T_reg therapy in the pursuit of transplantation tolerance. In this review we will summarize current knowledge of T_reg biology, explore novel technologies in the setting of T_reg immunotherapy and address key prerequisites surrounding the clinical application of T_regs in transplantation.

Cell Therapy in Kidney Transplantation: Focus on Regulatory T Cells

Renal transplantation is the renal replacement modality of choice for suitable candidates with advanced CKD or ESRD. Prevention of rejection, however, requires treatment with nonspecific pharmacologic immunosuppressants that carry both systemic and nephrologic toxicities. Use of a patient's own suppressive regulatory T cells (Tregs) is an attractive biologic approach to reduce this burden. Here, we review the immunologic underpinnings of Treg therapy and technical challenges to developing successful cell therapy. These issues include the selection of appropriate Treg subsets, ex vivo Treg expansion approaches, how many Tregs to administer and when, and how to care for patients after Treg administration.

Expression of a Chimeric Antigen Receptor Specific for Donor HLA Class I Enhances the Potency of Human Regulatory T Cells in Preventing Human Skin Transplant Rejection

Regulatory T cell (Treg) therapy using recipient-derived Tregs expanded ex vivo is currently being investigated clinically by us and others as a means of reducing allograft rejection following organ transplantation. Data from animal models has demonstrated that adoptive transfer of allospecific Tregs offers greater protection from graft rejection compared to polyclonal Tregs. Chimeric antigen receptors (CAR) are clinically translatable synthetic fusion proteins that can redirect the specificity of T cells toward designated antigens. We used CAR technology to redirect human polyclonal Tregs toward donor-MHC class I molecules, which are ubiquitously expressed in allografts. Two novel HLA-A2-specific CARs were engineered: one comprising a CD28-CD3ζ signaling domain (CAR) and one lacking an intracellular signaling domain (ΔCAR). CAR Tregs were specifically activated and significantly more suppressive than polyclonal or ΔCAR Tregs in the presence of HLA-A2, without eliciting cytotoxic activity. Furthermore, CAR and ΔCAR Tregs preferentially transmigrated across HLA-A2-expressing endothelial cell monolayers. In a human skin xenograft transplant model, adoptive transfer of CAR Tregs alleviated the alloimmune-mediated skin injury caused by transferring allogeneic peripheral blood mononuclear cells more effectively than polyclonal Tregs. Our results demonstrated that the use of CAR technology is a clinically applicable refinement of Treg therapy for organ transplantation.

Targeting Immunity in End-Stage Renal Disease

BACKGROUND

Despite the stable incidence of end-stage renal disease (ESRD), it continues to be associated with an unacceptably high cardiovascular risk.

SUMMARY

ESRD is characterized by enhanced oxidative stress and severe inflammation, which boost cardiovascular risk, thus increasing cardiovascular-associated mortality rate. While substantial effort has been made in the technological innovation of dialytic techniques, few significant advances have been made to reduce inflammation in patients with ESRD. Indeed, this contrasts with the extensive scientific breakthroughs made in the basic field of science in targeting inflammation. There is thus a pressing need for clinical trials to test the effect of reducing inflammation in patients with ESRD. Here, we will revisit the negative effect of ESRD on inflammation and explore the impact of enhanced inflammation on cardiovascular outcomes and survival in patients with ESRD. Finally, we will discuss the need for clinical trials that target inflammation in ESRD, as well as weigh potential disadvantages and offer novel innovative approaches. Key Message: We will try to understand why the issue of inflammation has not been successfully addressed thus far in patients with ESRD, while at the same time weighing the potential disadvantages and offering novel innovative approaches for targeting inflammation in patients with ESRD.

Transient antibody targeting of CD45RC induces transplant tolerance and potent antigen-specific regulatory T cells

Rat and human CD4⁺ and CD8⁺ Tregs expressing low levels of CD45RC have strong immunoregulatory properties. We describe here that human CD45 isoforms are nonredundant and identify distinct subsets of cells. We show that CD45RC is not expressed by CD4⁺ and CD8⁺ Foxp3⁺ Tregs, while CD45RA/RB/RO are. Transient administration of a monoclonal antibody (mAb) targeting CD45RC in a rat cardiac allotransplantation model induced transplant tolerance associated with inhibition of allogeneic humoral responses but maintained primary and memory responses against cognate antigens. Anti-CD45RC mAb induced rapid death of CD45RC^high T cells through intrinsic cell signaling but preserved and potentiated CD4⁺ and CD8⁺ CD45RC^low/- Tregs, which are able to adoptively transfer donor-specific tolerance to grafted recipients. Anti-CD45RC treatment results in distinct transcriptional signature of CD4⁺ and CD8⁺ CD45RC^low/- Tregs. Finally, we demonstrate that anti-human CD45RC treatment inhibited graft-versus-host disease (GVHD) in immune-humanized NSG mice. Thus, short-term anti-CD45RC is a potent therapeutic candidate to induce transplantation tolerance in human.

Treg therapy in transplantation: a general overview

Solid organ transplantation remains the treatment of choice for end-stage organ failure. Whilst the short-term outcomes post-transplant have improved in the last decades, chronic rejection and immunosuppressant side effects remain an ongoing concern. Hematopoietic stem cell transplantation is a well-established procedure for the treatment of patients with haematological disorders. However, donor T cells are continually primed and activated to react against the host causing graft-versus-host disease (GvHD) that leads to tissue damages and death. Regulatory T cells (Tregs) play an essential role in maintaining tolerance to self-antigens, preventing excessive immune responses and abrogating autoimmunity. Due to their suppressive properties, Tregs have been extensively studied for their use as a cellular therapy aiming to treat GvHD and limit immune responses responsible for graft rejection. Several clinical trials have been conducted or are currently ongoing to investigate safety and feasibility of Treg-based therapy. This review summarizes the general understanding of Treg biology and presents the methods used to isolate and expand Tregs. Furthermore, we describe data from the first clinical trials using Tregs, explaining the limitations and future application of these cells.

Successful expansion of functional and stable regulatory T cells for immunotherapy in liver transplantation

Strategies to prevent organ transplant rejection whilst minimizing long-term immunosuppression are currently under intense investigation with regulatory T cells (Tregs) nearing clinical application. The clinical trial, ThRIL, recently commenced at King's College London, proposes to use Treg cell therapy to induce tolerance in liver transplant recipients, the success of which has the potential to revolutionize the management of these patients and enable a future of drug-free transplants. This is the first report of the manufacture of clinical grade Tregs from prospective liver transplant recipients via a CliniMACS-based GMP isolation technique and expanded using anti-CD3/CD28 beads, IL-2 and rapamycin. We report the enrichment of a pure, stable population of Tregs (>95% CD4(+)CD25(+)FOXP3(+)), reaching adequate numbers for their clinical application. Our protocol proved successful in, influencing the expansion of superior functional Tregs, as compared to freshly isolated cells, whilst also preventing their conversion to Th17 cells under pro-inflammatory conditions. We conclude with the manufacture of the final Treg product in the clinical research facility (CRF), a prerequisite for the clinical application of these cells. The data presented in this manuscript together with the much-anticipated clinical results from ThRIL, will undoubtedly inform the improved management of the liver transplant recipient.

Natural regulatory T cells from patients with end-stage renal disease can be used for large-scale generation of highly suppressive alloantigen-specific Tregs

Natural occurring regulatory T cells (nTregs) have the potential to offer a targeted approach of immunosuppression and are the cell type of interest for inducing tolerance in kidney transplantation. End-stage renal disease (ESRD) profoundly affects the composition and function of circulating T cells but little is known with respect to how nTreg potential is affected. To address this, nTregs of patients with ESRD (on dialysis or not) and healthy individuals were isolated, expanded using allogeneic mature monocyte-derived dendritic cells followed by anti-CD3/anti-CD28-coated beads and the different nTregs were extensively characterized by the demethylation status of the Treg-specific demethylated region within FOXP3 and expression of typical nTreg markers. Additionally, the suppressive capacity as well as cytokine producing cells were analyzed for allogeneic mature monocyte-derived dendritic cell-expanded nTregs. Compared to age- and gender-matched healthy individuals, similar frequencies of nTregs were present within the circulation of patients with ESRD either on dialysis or not. The isolated nTregs could be equally well or even better expanded using allogeneic mature monocyte-derived dendritic cells and extensive characterization did not reveal significant differences. The demethylation status of the Treg-specific demethylated region was maintained or even further promoted as was the expression of markers characteristic for nTregs. Moreover, suppressive capacity and the cytokine profile of allogeneic mature monocyte-derived dendritic cell-expanded nTregs was similar to that of healthy individuals. Thus, circulating nTregs of patients with ESRD can effectively be expanded to stable allo antigen-specific nTregs with potential clinical applicability.

Ex vivo expanded regulatory T cells CD4+CD25+FoxP3+CD127Low develop strong immunosuppressive activity in patients with remitting-relapsing multiple sclerosis

Multiple sclerosis (MS) is an autoimmune disease characterized by defect in regulatory function of CD4⁺CD25⁺ T cells. We demonstrated difference in proportion of regulatory T cells CD4⁺CD25⁺FoxP3⁺CD127^low (Tregs) within the same patients' relapse and remission. Proportion of peripheral Tregs (pTregs) dropped almost two times in the relapse compare to remission. Levels of pTregs in patients' remission were lower than in healthy donors. Suppressive ability of pTregs was decreased in MS patients compared to healthy donors. Injections of expanded ex vivo autologous Tregs (eTregs) could be helpful in bringing up the level of Tregs in patients' blood. We developed a simple method for ex vivo expansion of autologous Tregs within a short period of time. The final pool of cells consisted of 90-95% eTregs. When we started the culture with 10-20 × 10⁶ CD4⁺ T cells, we yield 300-400 × 10⁶ eTregs in a week. Expression of FoxP3 and Helios was calculated by two methods. Expanded ex vivo patients' and donors' Tregs were characterized by increased from three to five times expression of FoxP3, as well as almost doubled Helios expression. Peripheral Tregs in MS patients have decreased demethylation of FoxP3 gene promoter in comparison with donors. On the contrary, eTregs showed stable up-regulated demethylation without difference between MS patients and donors. MS patients' and donors' eTregs have much more suppressive ability than pTregs. Our data showed that eTregs can be applied as immunotherapy for MS patients and other autoimmune diseases if further investigated.

Ex Vivo Costimulatory Blockade to Generate Regulatory T Cells From Patients Awaiting Kidney Transplantation

Short-term outcomes of kidney transplantation have improved dramatically, but chronic rejection and regimen-related toxicity continue to compromise overall patient outcomes. Development of regulatory T cells (Tregs) as a means to decrease alloresponsiveness and limit the need for pharmacologic immunosuppression is an active area of preclinical and clinical investigation. Nevertheless, the immunomodulatory effects of end-stage renal disease on the efficacy of various strategies to generate and expand recipient Tregs for kidney transplantation are incompletely characterized. In this study, we show that Tregs can be successfully generated from either freshly isolated or previously cryopreserved uremic recipient (responder) and healthy donor (stimulator) peripheral blood mononuclear cells using the strategy of ex vivo costimulatory blockade with belatacept during mixed lymphocyte culture. Moreover, these Tregs maintain a CD3(+) CD4(+) CD25(+) CD127(lo) surface phenotype, high levels of intracellular FOXP3 and significant demethylation of the FOXP3 Treg-specific demethylation region on allorestimulation with donor stimulator cells. These data support evaluation of this simple, brief Treg production strategy in clinical trials of mismatched kidney transplantation.