Monotherapy rapamycin allows an increase of CD4 CD25 FoxP3 T cells in renal recipients

Xin-Li formula attenuates heart failure induced by a combination of hyperlipidemia and myocardial infarction in rats via Treg immunomodulation and NLRP3 inflammasome inhibition

Background and aim

Heart failure (HF) is a complex clinical syndrome that represents the end result of several pathophysiologic processes. Despite a dramatic evolution in diagnosis and management of HF, most patients eventually become resistant to therapy. Xin-Li Formula (XLF) is a Chinese medicine formula which shows great potential in the treatment of HF according to our previous studies. The present study was designed to investigate the effects of XLF on HF induced by a combination of hyperlipidemia and myocardial infarction (MI) in rats and reveal the underlying mechanism.

Experimental procedure

A rat model of HF induced by hyperlipidemia and MI was established with intragastric administration of XLF and Perindopril. In vitro, CD4+ T cells from mouse spleen and LPS/ATP-stimulated THP-1 macrophages were employed.

Results and conclusion

XLF was shown to have markedly protective effects on MI-induced HF with hyperlipidemia in rats, including improvement of left ventricular function, reduction of left ventricular fibrosis and infarct size. Moreover, XLF administration significantly increased the number of Foxp3+ Tregs, and inhibited mTOR phosphorylation and NLRP3 signaling pathway. In vitro, we found that XLF had induced Treg activation via the inhibition of mTOR phosphorylation in CD4+ T cells. Additionally, XLF inhibited NLRP3 inflammasome activation in LPS/ATP-stimulated THP-1 macrophages. Taken together, this study raises the exciting possibility that Xin-Li Formula may benefit HF patients due to its immunomodulatory and anti-inflammatory effects via Treg activation and NLRP3 inflammasome inhibition.

Rapamycin limits CD4+ T cell proliferation in simian immunodeficiency virus-infected rhesus macaques on antiretroviral therapy

Proliferation of latently infected CD4⁺ T cells with replication-competent proviruses is an important mechanism contributing to HIV persistence during antiretroviral therapy (ART). One approach to targeting this latent cell expansion is to inhibit mTOR, a regulatory kinase involved with cell growth, metabolism, and proliferation. Here, we determined the effects of chronic mTOR inhibition with rapamycin with or without T cell activation in SIV-infected rhesus macaques (RMs) on ART. Rapamycin perturbed the expression of multiple genes and signaling pathways important for cellular proliferation and substantially decreased the frequency of proliferating CD4⁺ memory T cells (TM cells) in blood and tissues. However, levels of cell-associated SIV DNA and SIV RNA were not markedly different between rapamycin-treated RMs and controls during ART. T cell activation with an anti-CD3LALA antibody induced increases in SIV RNA in plasma of RMs on rapamycin, consistent with SIV production. However, upon ART cessation, both rapamycin and CD3LALA–treated and control-treated RMs rebounded in less than 12 days, with no difference in the time to viral rebound or post-ART viral load set points. These results indicate that, while rapamycin can decrease the proliferation of CD4⁺ TM cells, chronic mTOR inhibition alone or in combination with T cell activation was not sufficient to disrupt the stability of the SIV reservoir.

First-in-human phase 1 trial of induced regulatory T cells for graft-versus-host disease prophylaxis in HLA-matched siblings

Human CD4+25- T cells cultured in interleukin 2 (IL-2), rapamycin, and transforming growth factor β (TGFβ) along with anti-CD3 monoclonal antibody-loaded artificial antigen-presenting cells generate FoxP3+ induced regulatory T cells (iTregs) with potent suppressive function. We performed a phase 1, single-center, dose-escalation study to determine the safety profile of iTregs in adults with high-risk malignancy treated with reduced-intensity conditioning and mobilized peripheral blood stem cells (PBSCs) from HLA-identical sibling donors. Sixteen patients were enrolled and 14 were treated (2 productions failed to meet desired doses). One patient each received 3.0 × 106/kg, 3.0 × 107/kg, and 3.0 × 108/kg iTregs with corresponding T-conventional-to-iTreg ratios of 86:1, 8:1, and 1:2. After 3 patients received 3.0 × 108/kg in the presence of cyclosporine (CSA) and mycophenolate mofetil (MMF) with no dose-limiting toxicities, subsequent patients were to receive iTregs in the presence of sirolimus/MMF that favors Foxp3 stability based on preclinical modeling. However, 2 of 2 developed grade 3 acute graft-versus-host disease (GVHD), resulting in suspension of the sirolimus/MMF. An additional 7 patients received 3.0 × 108/kg iTregs with CSA/MMF. In the 14 patients treated with iTregs and CSA/MMF, there were no severe infusional toxicities with all achieving neutrophil recovery (median, day 13). Of 10 patients who received 3.0 × 108/kg iTregs and CSA/MMF, 7 had no aGVHD, 2 had grade 2, and 1 had grade 3. Circulating Foxp3+ iTregs were detectable through day 14. In summary, iTregs in the context of CSA/MMF can be delivered safely at doses as high as 3 × 108/kg. This trial was registered at www.clinicaltrials.gov as #NCT01634217.

Delivery of Rapamycin Using In Situ Forming Implants Promotes Immunoregulation and Vascularized Composite Allograft Survival

Vascularized composite allotransplantation (VCA), such as hand and face transplantation, is emerging as a potential solution in patients that suffered severe injuries. However, adverse effects of chronic high-dose immunosuppression regimens strongly limit the access to these procedures. In this study, we developed an in situ forming implant (ISFI) loaded with rapamycin to promote VCA acceptance. We hypothesized that the sustained delivery of low-dose rapamycin in proximity to the graft may promote graft survival and induce an immunoregulatory microenvironment, boosting the expansion of T regulatory cells (T_reg). In vitro and in vivo analysis of rapamycin-loaded ISFI (Rapa-ISFI) showed sustained drug release with subtherapeutic systemic levels and persistent tissue levels. A single injection of Rapa-ISFI in the groin on the same side as a transplanted limb significantly prolonged VCA survival. Moreover, treatment with Rapa-ISFI increased the levels of multilineage mixed chimerism and the frequency of T_reg both in the circulation and VCA-skin. Our study shows that Rapa-ISFI therapy represents a promising approach for minimizing immunosuppression, decreasing toxicity and increasing patient compliance. Importantly, the use of such a delivery system may favor the reprogramming of allogeneic responses towards a regulatory function in VCA and, potentially, in other transplants and inflammatory conditions.

Ways Forward for Tolerance-Inducing Cellular Therapies- an AFACTT Perspective

Clinical studies with cellular therapies using tolerance-inducing cells, such as tolerogenic antigen-presenting cells (tolAPC) and regulatory T cells (Treg) for the prevention of transplant rejection and the treatment of autoimmune diseases have been expanding the last decade. In this perspective, we will summarize the current perspectives of the clinical application of both tolAPC and Treg, and will address future directions and the importance of immunomonitoring in clinical studies that will result in progress in the field.

Evaluation of quantitative changes in regulatory T cells in peripheral blood of kidney transplant recipients with skin cancer after conversion to mTOR inhibitors

Introduction

Immunosuppressive therapy, necessary for graft survival, has its clinical consequences with an increased risk of developing malignancies being one of them. It seems that the maintenance of a proper balance between cytotoxic and regulatory activity of the immune system may prevent graft rejection, and with a lower risk of cancer.

Aim

To assess the quantitative changes in regulatory T cells (Tregs) in peripheral blood of kidney transplant recipients with post-transplantation skin neoplasm after conversion to mTOR inhibitors (mTORi) and to assess the incidence of secondary skin cancer in that group of patients.

Material and methods

Fourteen patients with post-transplant cutaneous malignancies converted to mTORi were included into the study. The control group consisted of eighteen patients maintained on immunosuppressive regimens without mTORi. The level of Tregs with a phenotype defined as CD4lowCD25high was measured before, and 6 months after, mTORi introduction.

Results

In all cases, 6 months after conversion, a significant decrease in the ratio of CD4⁺CD25⁺ to CD4^lowCD25^high from 6.52 to 4.29 was detected (p = 0.035). One patient converted to mTORi developed subsequent skin cancer, while in the control group, subsequent skin cancer was recognized in eight patients. Moreover, introducing mTORi significantly improved progression-free survival in this group of patients (p = 0.016).

Conclusions

Introducing mTORi to the immunosuppressive regimen resulted in an increase in the number of regulatory cells without increasing the incidence of secondary skin cancer in the investigated group of patients.

Recent advances in CD8+ regulatory T cell research

Various subgroups of CD8⁺ T lymphocytes do not only demonstrate cytotoxic effects, but also serve important regulatory roles in the body's immune response. In particular, CD8⁺ regulatory T cells (CD8⁺ Tregs), which possess important immunosuppressive functions, are able to effectively block the overreacting immune response and maintain the body's immune homeostasis. In recent years, studies have identified a small set of special CD8⁺ Tregs that can recognize major histocompatibility complex class Ib molecules, more specifically Qa-1 in mice and HLA-E in humans, and target the self-reactive CD4⁺ T ce lls. These findings have generated broad implications in the scientific community and attracted general interest to CD8⁺ Tregs. The present study reviews the recent research progress on CD8⁺ Tregs, including their origin, functional classification, molecular markers and underlying mechanisms of action.

Conversion to mycophenolate mofetil monotherapy in liver recipients: Calcineurin inhibitor levels are key

 The use of calcineurin inhibitors (CNI) after liver transplantation is associated with post-transplant nephrotoxicity. Conversion to mycophenolate mofetil (MMF) monotherapy improves renal function, but is related to graft rejection in some recipients. Our aim was to identify variables associated with rejection after conversion to MMF monotherapy. Conversion was attempted in 40 liver transplant recipients. Clinical variables were determined and peripheral mononuclear blood cells were immunophenotyped during a 12-month follow-up. Conversion was classified as successful (SC) if rejection did not occur during the follow-up. MMF conversion was successful with 28 patients (70%) and was associated with higher glomerular filtration rates at the end of study. It also correlated with increased time elapsed since transplantation, low baseline CNI levels (Tacrolimus ≤ 6.5 ng/mL or Cyclosporine ≤ 635 ng/mL) and lower frequency of tacrolimus use. The only clinical variable independently related to SC in multivariate analysis was low baseline CNI levels (p = 0.02, OR: 6.93, 95%, CI: 1.3-29.7). Mean baseline fluorescent intensity of FOXP3+ T cells was significantly higher among recipients with SC. In conclusion, this study suggests that baseline CNI levels can be used to identify recipients with higher probability of SC to MMF monotherapy. Clinicaltrials.gov identification: NCT01321112.

In Vitro Influence of Mycophenolic Acid on Selected Parameters of Stimulated Peripheral Canine Lymphocytes

Mycophenolic acid (MPA) is an active metabolite of mycophenolate mofetil, a new immunosuppressive drug effective in the treatment of canine autoimmune diseases. The impact of MPA on immunity is ambiguous and its influence on the canine immune system is unknown. The aim of the study was to determine markers of changes in stimulated peripheral canine lymphocytes after treatment with MPA in vitro. Twenty nine healthy dogs were studied. Phenotypic and functional analysis of lymphocytes was performed on peripheral blood mononuclear cells cultured with mitogens and different MPA concentrations– 1 μM (10⁻³ mol/m³), 10 μM or 100 μM. Apoptotic cells were detected by Annexin V and 7-aminoactinomycin D (7-AAD). The expression of antigens (CD3, CD4, CD8, CD21, CD25, forkhead box P3 [FoxP3] and proliferating cell nuclear antigen [PCNA]) was assessed with monoclonal antibodies. The proliferation indices were analyzed in carboxyfluorescein diacetate succinimidyl ester (CFSE)-labeled cells. All analyses were performed using flow cytometry. The influence of MPA on apoptosis was dependent on the mechanism of cell activation and MPA concentration. MPA caused a decrease in the expression of lymphocyte surface antigens, CD3, CD8 and CD25. Its impact on the expression of CD4 and CD21 was negligible. Its negative influence on the expression of FoxP3 was dependent on cell stimulation. MPA inhibited lymphocyte proliferation. In conclusion, MPA inhibited the activity of stimulated canine lymphocytes by blocking lymphocyte activation and proliferation. The influence of MPA on the development of immune tolerance–expansion of Treg cells and lymphocyte apoptosis–was ambiguous and was dependent on the mechanism of cellular activation. The concentration that MPA reaches in the blood may lead to inhibition of the functions of the canine immune system. The applied panel of markers can be used for evaluation of the effects of immunosuppressive compounds in the dog.

Post-transplantation malignancies: here today, gone tomorrow?

From the early days of transplantation onwards, increased cancer development in transplant recipients, who require immunosuppression to avoid graft rejection, has been recognized. Registry data indicate that approximately 10-30% of deaths are attributed to post-transplant malignancy, with an upward trend in this incidence as more patients have been exposed to chronic lifelong immunosuppression. In this Review, the overall incidence and most frequent types of cancer encountered are summarized, along with information about which transplant recipients are at the greatest risk of malignancy. Reasons for why differences exist in susceptibility to cancer in this patient population are examined, and approaches that might improve our understanding of the options available for reducing the incidence of this adverse effect of immunosuppression are described. Whether anti-rejection drugs have been successful in diminishing overall immunosuppressive burden, and consequently show any promise for decreasing post-transplant malignancies is also discussed. The topic shifts to one class of conventional anti-rejection drugs, the mammalian target of rapamycin (mTOR) inhibitors, which paradoxically have both immunosuppressive and anti-neoplastic properties. The complex activities of mTOR are reviewed in order to provide context for how these seemingly opposing effects are possible, and the latest clinical data on use of mTOR inhibitors in the clinic are discussed. The current and future perspectives on how best to normalize these unacceptably high rates of post-transplantation malignancies are highlighted.

Impact of immunosuppressive drugs on the therapeutic efficacy of ex vivo expanded human regulatory T cells

Immunosuppressive drugs in clinical transplantation are necessary to inhibit the immune response to donor antigens. Although they are effective in controlling acute rejection, they do not prevent long-term transplant loss from chronic rejection. In addition, immunosuppressive drugs have adverse side effects, including increased rate of infections and malignancies. Adoptive cell therapy with human Tregs represents a promising strategy for the induction of transplantation tolerance. Phase I/II clinical trials in transplanted patients are already underway, involving the infusion of Tregs alongside concurrent immunosuppressive drugs. However, it remains to be determined whether the presence of immunosuppressive drugs negatively impacts Treg function and stability. We tested in vitro and in vivo the effects of tacrolimus, mycophenolate and methylprednisolone (major ISDs used in transplantation) on ex vivo expanded, rapamycin-treated human Tregs. The in vitro results showed that these drugs had no effect on phenotype, function and stability of Tregs, although tacrolimus affected the expression of chemokine receptors and IL-10 production. However, viability and proliferative capacity were reduced in a dose-dependent manner by all the three drugs. The in vivo experiments using a humanized mouse model confirmed the in vitro results. However, treatment of mice with only rapamycin maintained the viability, function and proliferative ability of adoptively transferred Tregs. Taken together, our results suggest that the key functions of ex vivo expanded Tregs are not affected by a concurrent immunosuppressive therapy. However, the choice of the drug combination and their timing and dosing should be considered as an essential component to induce and maintain tolerance by Treg.

Adoptive cell transfer in autoimmune hepatitis

Adoptive cell transfer is an intervention in which autologous immune cells that have been expanded ex vivo are re-introduced to mitigate a pathological process. Tregs, mesenchymal stromal cells, dendritic cells, macrophages and myeloid-derived suppressor cells have been transferred in diverse immune-mediated diseases, and Tregs have been the focus of investigations in autoimmune hepatitis. Transferred Tregs have improved histological findings in animal models of autoimmune hepatitis and autoimmune cholangitis. Key challenges relate to discrepant findings among studies, phenotypic instability of the transferred population, uncertain side effects and possible need for staged therapy involving anti-inflammatory drugs. Future investigations must resolve issues about the purification, durability and safety of these cells and consider alternative populations if necessary.

Superiority of rapamycin over tacrolimus in preserving nonhuman primate Treg half-life and phenotype after adoptive transfer

Many critical issues remain concerning how best to deploy adoptive regulatory T cell (Treg) immunotherapy to the clinic. These include a determination of their pharmacokinetic characteristics, their optimal dose, their phenotypic stability and the best therapies with which to pair Tregs. By performing a CFSE-labeled autologous Treg pulse experiment, we determined that the accessible peripheral blood Treg pool in rhesus macaques is quite large (75 ± 11 × 10(6) Tregs/kg). Pharmacokinetic analysis revealed that Tregs have two phases of elimination: an α phase, with a T1/2 in the peripheral blood of 32.4 ± 11.3 h and a β phase with a T1/2 of 120.4 ± 19.7 h. In addition to their short initial half-life, Tregs underwent rapid phenotypic shifts after infusion, with significant loss of both CD25 and FoxP3 by day +6. While tacrolimus stabilized CD25 expression, it did not improve T1/2 , nor mitigate the loss of FoxP3. In contrast, rapamycin significantly stabilized both CD25 and FoxP3, and supported an increased half-life, with an α phase of 67.7 ± 6.9 h and a β phase of 252.1 ± 54.9 h. These results suggest that rapamycin may be a necessary addition to Treg immunotherapy, and that tacrolimus may be deleterious to Treg integrity posttransfer.

Cellular and molecular immune profiles in renal transplant recipients after conversion from tacrolimus to sirolimus

Tacrolimus and Sirolimus are commonly used maintenance immunesuppressants in kidney transplantation. Since their effects on immune cells and allograft molecular profiles have not been elucidated, we characterized the effects of Tacrolimus to Sirolimus conversion on frequency and function of T cells, and on graft molecular profiles. Samples from renal transplant patients in a randomized trial of 18 patients with late Sirolimus conversion and 12 on Tacrolimus maintenance were utilized. Peripheral blood was collected at 0, 6, 12 and 24-months post-randomization with T cell subpopulations analyzed by flow cytometry and T cell alloreactivity tested by IFN-γ ELISPOT. Graft biopsy samples obtained 24-months post-randomization were used for gene expression analysis. Sirolimus conversion led to an increase in CD4⁺25⁺⁺⁺Foxp3⁺ regulatory T cells. While Tacrolimus-maintained patients showed a decrease in indirect alloreactivity over time post-transplant, Sirolimus conversion increased indirect alloreactive T cell frequencies compared to Tacrolimus-maintained patients. No histological differences were found in graft biopsies, but molecular profiles showed activation of the antigen presentation, IL-12 signaling, oxidative stress, macrophage-derived production pathways, and increased inflammatory and immune response in Sirolimus-converted patients. Thus, chronic immune alterations are induced after Sirolimus conversion. Despite the molecular profile being favorable to calcineurin inhibitor-based regimen, there was no impact in renal function over 30 months of follow-up.

A systematic review of conversion from calcineurin inhibitor to mammalian target of rapamycin inhibitors for maintenance immunosuppression in kidney transplant recipients

This was a systematic review of randomized controlled trials comparing delayed conversion of mammalian target of rapamycin inhibitors (mTORi) for calcineurin inhibitors (CNIs) versus CNI continuation in kidney transplantation. Databases (2000-2012) and conference abstracts (2009-2012) were searched giving a total of 29 trials. Outcomes analyzed included GFR, graft loss, rejection and adverse events and were expressed as weighted mean differences (WMDs) or as risk ratios (RRs). Patients converted to mTORi up to 1 year posttransplant in intention-to-treat analysis had higher GFR compared with those remaining on CNI (WMD 0.28 mL/min/1.73 m(2) , 95% confidence interval [CI] 0.21-0.36; I(2)  = 68%, p < 0.001). Stratifying trials by time posttransplant or type of mTORi did not change the overall heterogeneity. For on-treatment population, mTORi was associated with higher GFR (14.21 mL/min/1.73 m(2) , 10.34-18.08; I(2)  = 0%, p = 0.970) 2-5 years posttransplant. The risk of rejection at 1 year was higher in mTORi trials (RR 1.72, 1.34-2.22; I(2)  = 12%, p = 0.330). Discontinuation secondary to adverse events was more common in patients on mTORi, whereas the incidence of skin cancers and cytomegalovirus infection was lower in patients on mTORi. Conversion from CNI to mTORi is associated with short-term improvements in GFR in a number of studies but longer-term follow-up data of graft and patient survival are required.

Regulatory T cells as immunotherapy

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

Rapamycin induces ILT3(high)ILT4(high) dendritic cells promoting a new immunoregulatory pathway

ILT3(high)ILT4(high) dendritic cells (DCs) may cause anergy in CD4(+)CD45RO(+)CD25(+) T cells transforming them into regulatory T cells (Tregs). Here, we tested whether chronic exposure to rapamycin may modulate this immunoregulatory pathway in renal transplant recipients. Forty renal transplant patients with biopsy-proven chronic allograft nephropathy and receiving calcineurin inhibitors were randomly assigned to either calcineurin inhibitor dose reduction or withdrawal with rapamycin introduction. At conversion and 2 years thereafter, we measured the rapamycin effects on circulating DCs (BDCA1/BDCA2 and ILT3/ILT4 expression), CD4(+)/CD25(high)/Foxp3(+) Tregs, CD8(+)/CD28(-) T cells, and the Th1/Th2 balance in graft biopsies. In rapamycin-treated patients, peripheral BDCA2(+) cells were significantly increased along with ILT3/ILT4(+) DCs. The number of circulating CD4(+)/CD25(high)/Foxp3(+)/CTLA4(+) Tregs, CD8(+)CD28(-) T cells, and HLA-G serum levels were higher in the rapamycin-treated group. The number of ILT3/ILT4(+)BDCA2(+) DC was directly and significantly correlated with circulating Tregs and CD8(+)CD28(-) T cells. ILT3/ILT4 expression was increased in kidney biopsies at the end of the study period along with a significant bias toward a Th2 response within the graft only in the rapamycin-treated patients. Thus, rapamycin induces the upregulation of ILT3 and ILT4 on the DC surface, and this effect is associated with an increase in the number of Tregs and expansion of the CD8(+)CD28(-) T cell population. This suggests that mTOR inhibition may promote a novel immunoregulatory pathway.

Immunologic monitoring in kidney transplant recipients

Transplant biopsy has always been the gold standard for assessing the immune response to a kidney allograft (Chandraker A: Diagnostic techniques in the work-up of renal allograft dysfunction-an update. Curr Opin Nephrol Hypertens 8:723-728, 1999). A biopsy is not without risk and is unable to predict rejection and is only diagnostic once rejection has already occurred. However, in the past two decades, we have seen an expansion in assays that can potentially put an end to the "drug level" era, which until now has been one of the few tools available to clinicians for monitoring the immune response. A better understanding of the mechanisms of rejection and tolerance, and technological advances has led to the development of new noninvasive methods to monitor the immune response. In this article, we discuss these new methods and their potential uses in renal transplant recipients.

Influence of pharmacological immunomodulatory agents on CD4(+)CD25(high)FoxP3(+) T regulatory cells in humans

T regulatory cells (Tregs) play a critical role in the immunologic tolerance to the graft in transplantation. Thus, due to their immunosuppressive capability, ex vivo expanded Tregs may be used as a cellular therapy and an attractive novel strategy to control chronic rejection and eliminate need for lifelong pharmacological immunosuppression. Since Treg therapy is still in its infancy, initially Tregs still need to be applied in combination with pharmacological agents to prevent rejection. Fortunately, some of the medications have been shown to enhance the function and number of Tregs. In the clinic, different immunosuppressive regimens are used for individual patients for different types of organ transplantation. In this review, we present the most commonly used pharmacological agents for immunosuppression and discuss how they affect the Treg population. It is extremely difficult to dissect the effect of single agent on Tregs population in clinical settings since usually the combination of several medications is applied at the same time for graft protection. Nevertheless, experimental and clinical data indicate that thymoglobulin as immunosuppressive induction and mTOR inhibitors as immunosuppressive maintenance agents have the most beneficial effect on Treg population in the blood. Among supplemental agents promoting Tregs, anti-TNFα preparations have been in clinical use (in autoimmune diseases) for many years, so they are optimal candidates for testing in transplant settings in combination with Treg based cellular therapy.

Analysis of FOXP3 gene and protein expressions in renal allograft biopsies and their association with graft outcomes

BACKGROUND

The transcription factor FOXP3 is increased in acute renal rejection, but its influence on graft outcomes is unclear. This study correlated FOXP3 with dendritic cells and graft outcomes.

METHODS

We assessed 96 kidney transplants undergoing allograft biopsy for cause. FOXP3 mRNA was analyzed by real-time polymerase chain reaction (PCR) and FOXP3 protein and DCsCD83(+) by immunohistochemistry. Graft function and survival were assessed at 5 years post-transplantation, as well as by independent predictors of graft loss.

RESULTS

Intragraft FOXP3 gene and protein expression were significantly correlated (r = 0.541, p < 0.001). Both FOXP3 mRNA and protein were increased in patients with acute rejection (AR). High expression of FOXP3 mRNA or protein in biopsies did not correlate with clinical variables, but there was a trend to higher positive variation in the glomerular filtration rate (GFR) from biopsy to last follow-up. Patients with FOXP3-mRNA(high) had more DCsCD83(+) in biopsy, but these cells did not associate with AR. Five-year graft survival was not influenced by either FOXP3 mRNA or protein expressions.

CONCLUSIONS

FOXP3 mRNA and protein had a good correlation in archival renal graft tissue. Increased FOXP3 expression was found in AR and FOXP3 associated with high numbers of DCs. However, both FOXP3 mRNA and protein was not associated with better allograft outcomes.

Phospho-specific flow cytometry for pharmacodynamic monitoring of immunosuppressive therapy in transplantation

Organ transplant recipients frequently suffer from toxicity or from lack of efficacy of immunosuppressive drugs, which can be attributed to individual variations in drug sensitivity. This problem can be resolved by applying pharmacodynamic monitoring that focuses on measuring the biological effects of drugs. Here we discuss the new technique called phospho-specific flow cytometry to monitor the activity of intracellular immune signaling pathways at the single-cell level in whole blood samples. Through this tool the efficacy of immunosuppressive medication can be assessed, novel targets can be identified, and differences in drug sensitivity between cells and patients can be clarified.

Effect of rapamycin and interleukin-2 on regulatory CD4+CD25+Foxp3+ T cells in mice after allogenic corneal transplantation

BACKGROUND

We explored the effect of rapamycin (RAPA) and interleukin (IL)-2 on regulatory CD4(+)CD25(+)Foxp3(+) T cells (Treg) in recipient mice after allogenic corneal transplantation and analyzed its correlation with graft outcome.

METHODS

Allogenic corneal transplantation was performed using C57/BL6 mice as donors and Balb/c mice as recipients. RAPA, IL-2, and RAPA + IL-2 (mixed group) were administered to recipient mice, with three dosages for each therapeutic protocol. The graft status was assessed twice per week. The percentage of CD4(+)CD25(+)Foxp3(+) Treg in the peripheral blood, spleen, and draining lymph nodes was analyzed. The expression of Foxp3 mRNA in grafts was tested, and the concentration of IL-10 and transforming growth factor (TGF)-β1 in serum and aqueous humor was measured.

RESULTS

The lowest scores of graft neovascularization and opacity were mainly found in mixed groups. The percentage of CD4(+)CD25(+)Foxp3(+) Tregs in blood was increased significantly in mice treated with either high-dose RAPA or high-dose IL-2, and a synergistic effect was found in mixed high-dose group. So were the Tregs in either spleen or draining lymph nodes. However, such effects were weakened with decreased dosage. Foxp3 gene expression in grafts was elevated significantly in the recipients treated with median dosage of RAPA, IL-2, and mixed agents. The concentration of IL-10 in serum and aqueous humor was increased significantly in mice with mixed- high-dose treatment. Mixed treatments also enhanced TGF-β1 level in serum and aqueous humor, except those receiving low dosage.

CONCLUSION

In vivo administration of RAPA prohibited graft rejection after allogenic penetrating keratoplasty through expansion of CD4(+)CD25(+)Foxp3(+) Tregs. Simultaneous treatment of IL-2 enabled further elevation of Tregs. However, the synergistic effect was dosage-dependent, being the most potent at high dosage. The protocol may be beneficial to induce transplantation tolerance.

Translating tolerogenic therapies to the clinic - where do we stand?

Manipulation of the immune system to prevent the development of a specific immune response is an ideal strategy to improve outcomes after transplantation. A number of experimental techniques exploiting central and peripheral tolerance mechanisms have demonstrated success, leading to the first early phase clinical trials for tolerance induction. The first major strategy centers on the facilitation of donor-cell mixed chimerism in the transplant recipient with the use of bone marrow or hematopoietic stem cell transplantation. The second strategy, utilizing peripheral regulatory mechanisms, focuses on cellular therapy with regulatory T cells. This review examines the key studies and novel research directions in the field of immunological tolerance.

On the interactions between mesenchymal stem cells and regulatory T cells for immunomodulation in transplantation

Experimental studies have established the use of mesenchymal stem cells (MSC) as a candidate immunosuppressive therapy. MSC exert their immunomodulatory function through the inhibition of CD4⁺ and CD8⁺ T cell proliferation. It is unknown whether MSC impair the immunosuppressive function of regulatory T cells (Treg). In vitro and in vivo studies suggest that MSC mediate their immunomodulatory effects through the induction of Treg. In this review we will focus on the interactions between MSC and Treg, and evaluate the consequences of these cellular interplays for prospective MSC immunotherapy in organ transplantation.

Successful resolution of inflammation and increased regulatory T cells in sirolimus-treated post-transplant allograft hepatitis

This retrospective case series reviews our center's experience with sirolimus and a CNI as alternative therapy for the treatment of PTAH. It also characterizes regulatory T cells (Tregs) in PTAH. LT recipients with PTAH who had received or were receiving treatment with sirolimus were retrospectively identified (n = 12). Liver enzymes, immunohistochemistry, and histology were compared in all 12 patients. Immunophenotyping for Tregs in peripheral blood mononuclear cells was performed on LT recipients with PTAH on conventional therapy with CNI, azathioprine ± prednisone (CT) (n = 11), recipients with PTAH on sirolimus, CNI ± prednisone (n = 8), recipients without PTAH (n = 25), and pre-transplant patients (n = 5). Severity of necro-inflammatory changes markedly improved with sirolimus. Treg frequency and number were significantly lower in recipients with PTAH on CT compared to (i) those on sirolimus (p = 0.002 and p = 0.01, respectively), and (ii) recipients without PTAH (p = 0.07 and p = 0.009, respectively). Treg frequency was significantly higher in recipients with PTAH on sirolimus compared to recipients without PTAH under CNI therapy (p = 0.027). Sirolimus in addition to a CNI is successful in reversing inflammation in LT recipients with PTAH. This is associated with significantly higher circulating Tregs.

FOXP3+ regulatory T cells: from suppression of rejection to induction of renal allograft tolerance

Naturally occurring and induced regulatory T cells (Tregs) can become hyporesponsive and anergic to antigen stimulation in autoimmune diseases and allograft rejection. The mechanisms of suppression of effector T cells by Tregs remain unclear, but there are in vitro and in vivo evidences showing that these cells are able to suppress antigen-specific responses via direct cell-to-cell contact, secrete anti-inflammatory cytokines such as TGF-β and IL-10, and inhibit the generation of memory T cells, among others. The transcription factor FOXP3 is a specific marker of Tregs and its deficiency is associated with autoimmune diseases and inflammation. During acute rejection of kidney allografts, an augmented FOXP3 gene expression as well as increased CD4(+)CD25(+)FOXP3(+) and other cell populations are observed in graft biopsies. However, it is not clear whether Tregs migrate into the graft and are retained there to suppress the inflammatory process, or whether they are directly associated with more complex mechanisms to induce immune tolerance. FOXP3(+) Tregs may direct the immune response toward a graft acceptance program, potentially affecting the long-term survival of transplanted organs and tissues. Immunosuppressive drugs modulate the number and function of circulating Tregs and FOXP3 expression. Experimental and clinical studies have shown that mTOR inhibitors have positive and calcineurin inhibitors negative effects on Tregs, but it is difficult to set apart the effect of multiple other factors known to be associated with short- and long-term renal graft outcomes. This review aimed to describe the functions of Tregs and its transcription factor FOXP3 in suppression of immune response during rejection and in induction of kidney graft tolerance, as well as to review the individual effects of immunosuppressive drugs on Tregs.

Peripheral blood sampling for the detection of allograft rejection: biomarker identification and validation

Currently, acute allograft rejection can only be detected reliably by deterioration of graft function confirmed by allograft biopsy. A huge drawback of this method of diagnosis is that substantial organ damage has already taken place at the time that rejection is diagnosed. Discovering and validating noninvasive biomarkers that predict acute rejection, and chronic allograft dysfunction, is of great importance. Many studies have investigated changes in the peripheral blood in an attempt to find biomarkers that reflect changes in the graft directly or indirectly. Herein, we will review the promises and limitations of the peripheral blood biomarkers that have been described in the literature so far.

Monitoring of CD4+CD25highIL-7Rαhigh activated T cells in kidney transplant recipients

BACKGROUND AND OBJECTIVES

In humans, circulating CD4(+)CD25(high) T cells contain mainly regulatory T cells (Treg; FoxP3(+)IL-7Rα(low)), but a small subset is represented by activated effector T cells (Tact; FoxP3(-)IL-7Rα(high)). The balance between Tact and Treg may be important after transplantation. The aim of this study was first to analyze and correlate CD4(+)CD25(high) Tact and Treg with the clinical status of kidney transplant recipients and second to study prospectively the effect of two immunosuppressive regimens on Tact/Treg during the first year after transplantation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

CD4(+)CD25(high) Tact and Treg were analyzed by flow cytometry, either retrospectively in 90 patients greater than 1 year after kidney transplantation (cross-sectional analysis) or prospectively in 35 patients receiving two immunosuppressive regimens after kidney transplantation (prospective analysis).

RESULTS

A higher proportion of Tact and a lower proportion of Treg were found in the majority of kidney recipients. In chronic humoral rejection, a strikingly higher proportion of Tact was present. A subgroup of stable recipients receiving calcineurin inhibitor-free immunosuppression (mycophenolate mofetil, azathioprine, or sirolimus) had Tact values that were similar to healthy individuals. In the prospective analysis, the proportion of Tact significantly increased in both immunosuppression groups during the first year after transplantation.

CONCLUSIONS

These data highlight distinct patterns in the proportion of circulating Tact depending on the clinical status of kidney recipients. Moreover, the prospective analysis demonstrated an increase in the proportion of Tact, regardless of the immunosuppressive regimen. The measurement of Tact, in addition to Treg, may become a useful immune monitoring tool after kidney transplantation.

Th17 cells in alemtuzumab-treated patients: the effect of long-term maintenance immunosuppressive therapy

BACKGROUND

Leukocyte depletion at the time of transplantation with alemtuzumab (Campath-1H) has been demonstrated to be a potential strategy for reducing long-term exposure to immunosuppressive drugs. Although the impact of alemtuzumab treatment on the immune system has been explored, the effects of long-term immunosuppressive therapy in alemtuzumab-treated patients still need to be elucidated.

METHODS

T-regulatory cells and Th1/Th17 responses were assessed by flow cytometry and real-time polymerase chain reaction more than 4 years after transplantation in 10 kidney recipients treated with alemtuzumab induction. Seven patients were converted to sirolimus monotherapy at 12 months posttransplant, whereas the remaining three patients with history of graft rejection were treated with sirolimus and mycophenolate mofetil. In addition, we sorted and expanded interleukin (IL)-17A-producing CCR6CD4 T cells and assessed their susceptibility to suppression by regulatory T (Treg) cells in in vitro suppression tests.

RESULTS

Three years of mammalian target of rapamycin inhibitor monotherapy correlates with an increase in the number of IL-17A producing cells, compared with patients treated with sirolimus and mycophenolate mofetil. In these patients, IL-17A expression was compensated for by an increase in Treg cell frequency and number. In addition, we demonstrated that both proliferation and cytokine production by Th17 cells can be effectively regulated by Treg cells.

CONCLUSIONS

Our results demonstrate that history of rejection and long-term maintenance immunosuppression has an impact on the number of circulating Treg and Th17 cells. However, more importantly, we have shown that Treg cells can effectively regulate Th17cells both in vitro and in vivo.

Kidney transplant recipients show an increase in the ratio of T-cell effector memory/central memory as compared to nontransplant recipients on the waiting list

Studies of allotolerance in animal models do not usually consider the presence of preexisting memory T cells and activated immune status. However, humans are exposed throughout life to a multitude of external agents that enhance the immune memory. In this article, we consider the effect that a previous kidney transplant has on the number of regulatory T cells (Tregs), effector memory T cells (TEM), and central memory T cells (TCM). Sixty-three patients with end-stage renal disease were studied just before being transplanted (51 first transplants and 12 retransplants). The numbers of Tregs (CD4+ CD25highCD127lowCD27+CD62L+CD45RO+FOXP3+), TEM (CD3+CD45RO+CD62L+), and TCM (CD3+CD45RO+CD62L-) cell subsets were quantified in peripheral blood by flow cytometry. The absolute number of Tregs was slightly lower in patients with previous allografts (median, 95% confidence interval [CI]: 16.7 cells/mm3, 12-20.5) than in those who received their first transplants (median, 95% CI: 19.6 cells/mm3, 19.3-29.6; P-NS). Clearer differences were found with the number of CD3+ TCM, since the transplanted patients had lower numbers (238 cells/mm3, 153-323) than those who had not yet received transplants (378 cells/mm3, 317-439; P=.029). As a result, the TEM/TCM ratios of both CD4+ and CD8+ T cells in patients with previous allografts were higher than in those who received first transplants. In conclusion, the assessment of just the number of Tregs in renal transplant patients is not enough and must be read together with the number of TEM and TCM. The TEM:TCM ratio increases in patients with previous allografts, probably due to activation of the immune response in renal transplantation.

Rapamycin generates graft-homing murine suppressor CD8(+) T cells that confer donor-specific graft protection

It has been reported that rapamycin (RPM) can induce de novo conversion of the conventional CD4(+)Foxp3(-) T cells into CD4(+)Foxp3(+) regulatory T cells (iTregs) in transplantation setting. It is not clear whether RPM can similarly generate suppressor CD8(+) T cells to facilitate graft acceptance. In this study, we investigated the ability of short-term RPM treatment in promoting long-term acceptance (LTA) of MHC-mismatched skin allografts by generating a CD8(+) suppressor T-cell population. We found that CD4 knockout (KO) mice (in C57BL/6 background, H-2(b)) can promptly reject DBA/2 (H-2(d)) skin allografts with mean survival time (MST) being 13 days (p < 0.01). However, a short course RPM treatment in these animals induced LTA with graft MST longer than 100 days. Adoptive transfer of CD8(+) T cells from LTA group into recombination-activating gene 1 (Rag-1)-deficient mice provided donor-specific protection of DBA/2 skin grafts against cotransferred conventional CD8(+) T cells. Functionally active immunoregulatory CD8(+) T cells also resided in donor skin allografts. Eighteen percent of CD8(+) suppressor T cells expressed CD28 as measured by flow cytometry, and produced reduced levels of IFN-γ, IL-2, and IL-10 in comparison to CD8(+) effector T cells as measured by ELISA. It is unlikely that CD8(+) suppressor T cells mediated graft protection via IL-10, as IL-10/Fc fusion protein impaired RPM-induced LTA in CD4 KO mice. Our data supported the notion that RPM-induced suppressor CD8(+) T cells home to the allograft and exert donor-specific graft protection.

Operational tolerance: past lessons and future prospects

Every liver transplant (LT) center has had patients who either self-discontinue immunosuppressive (IS) therapy or are deliberately withdrawn due to a research protocol or clinical concern (ie, lymphoproliferative disorder [LPD], overwhelming infection). This is understandable because maintenance IS therapy, particularly calcineurin inhibitors (CNI), is associated with significant cost, side effects, and considerable long-term morbidity and mortality. Detrimental effects of IS therapy include increased risk of cardiovascular disease, metabolic syndrome, bone loss, opportunistic and community-acquired infections, and malignancy. In fact, LT recipients have among the highest rates of chronic kidney disease and associated mortality among all nonkidney solid organ recipients. This mortality is only ameliorated by undergoing a curative kidney transplant, usurping costs and valuable organ resources. The search for improved treatment algorithms includes trial and error CNI dose minimization, the use of alternative IS agents (antimetabolites, mammalian target of rapamycin [mTOR] inhibitors), or even complete CNI withdrawal. Yet those who are successful in achieving such operational tolerance (no immunosuppression and normal allograft function) are considered lucky. The vast majority of recipients will fail this approach, develop acute rejection or immune-mediated hepatitis, and require resumption of IS therapy. As such, withdrawal of IS following LT is not standard-of-care, leaving clinicians to currently maintain transplant patients on IS therapy for life. Nonetheless, the long-term complications of all IS therapies highlight the need for strategies to promote immunologic or operational tolerance. Clinically applicable biomarker assays signifying the potential for tolerance as well as tolerogenic IS conditioning are invariably needed if systematic, controlled rather than "hit or miss" approaches to withdrawal are considered. This review will provide an overview of the basic mechanisms of tolerance, particularly in relation to LT, data from previous IS withdrawal protocols and biomarker studies in tolerant recipients, and a discussion on the prospect of increasing the clinical feasibility and success of withdrawal.

Novel immunotherapeutic approaches for allergy and asthma

The immune response is a tightly regulated process, which normally results in protection from infection and tolerance of innocuous environmental antigens. However, in allergic disease, the activated immune response results in a chronic pro-inflammatory state characterized by antibody secretion (IgE) and T cell activation to normally well-tolerated antigens. Currently, the treatment of allergic disease is focused on the suppression of key inflammatory mediators or inflammatory cell populations and include anti-histamines, anti-leukotrienes, &#x03B2;2 adrenergic receptor agonists and corticosteroids. However, these approaches only provide a temporary suppression of disease symptoms. Successful long-term treatment can only be provided by allergen-specific immunotherapy (allergen-SIT), which restores normal immunity against allergens. This review will discuss novel approaches to the management of allergy and asthma by targeting the T regulatory cell via modulation of the commensal microbiota and allergen-SIT.

Infusion of ex vivo expanded T regulatory cells in adults transplanted with umbilical cord blood: safety profile and detection kinetics

Acute graft-versus-host disease (aGVHD) is associated with high risk of morbidity and mortality and is a common complication after double umbilical cord blood (UCB) transplantation. To reduce these risks, we established a method of CD4(+)CD25(+)FoxP3(+) T regulatory cell (Treg) enrichment from cryopreserved UCB followed by a 18 (+) 1-day expansion culture including anti-CD3/anti-CD28 antibody-coated beads and recombinant human interleukin-2. In a "first-in-human" clinical trial, we evaluated the safety profile of UCB Treg in 23 patients. Patients received a dose of 0.1-30 × 10(5)UCB Treg/kg after double UCB transplantation. The targeted Treg dose was achieved in 74% of cultures, with all products being suppressive in vitro (median 86% suppression at a 1:4 ratio). No infusional toxicities were observed. After infusion, UCB Treg could be detected for 14 days, with the greatest proportion of circulating CD4(+)CD127(-)FoxP3(+) cells observed on day (+)2. Compared with identically treated 108 historical controls without Treg, there was a reduced incidence of grade II-IV aGVHD (43% vs 61%, P = .05) with no deleterious effect on risks of infection, relapse, or early mortality. These results set the stage for a definitive study of UCB Treg to determine its potency in preventing allogeneic aGVHD. This study is registered at http://www.clinicaltrials.gov as NCT00602693.

Update in the mechanisms of allergen-specific immunotheraphy

Allergic diseases represent a complex innate and adoptive immune response to natural environmental allergens with Th2-type T cells and allergen-specific IgE predominance. Allergen-specific immunotherapy is the most effective therapeutic approach for disregulated immune response towards allergens by enhancing immune tolerance mechanisms. The main aim of immunotherapy is the generation of allergen nonresponsive or tolerant T cells in sensitized patients and downregulation of predominant T cell- and IgE-mediated immune responses. During allergen-specific immunotherapy, T regulatory cells are generated, which secrete IL-10 and induce allergen-specific B cells for the production of IgG4 antibodies. These mechanisms induce tolerance to antigens that reduces allergic symptoms. Although current knowledge highlights the role of T regulatory cell-mediated immunetolerance, definite mechanisms that lead to a successful clinical outcomes of allergen-specific immunotherapy still remains an open area of research.

CD4+ regulatory T cells in solid organ transplantation

PURPOSE OF REVIEW

Solid organ transplantation is the most effective treatment for end-stage organ failure, but the long-term outcomes remain suboptimal. CD4 regulatory T cells (Tregs) are emerging as a potential therapy to facilitate long-term allograft survival. This review provides a general overview of the biology of CD4 Tregs and then goes on to discuss the most relevant and recent experimental and clinical evidence for their therapeutic use in solid organ transplantation.

RECENT FINDINGS

There have been major advances in our understanding of Tregs, including improvements in methods for their isolation and expansion. Experimental models are providing very important data on the in-vitro and in-vivo behavior of Tregs in transplantation, while recent clinical trials of Treg cellular therapy in graft-versus-host disease are offering a valuable insight into the efficacy of Treg adoptive cellular therapy.

SUMMARY

Data in favor of Treg cellular therapy in transplantation are mounting, and we predict that their use in clinical trials is on the horizon.

The effects of immunosuppressive drugs on CD4(+) CD25(+) regulatory T cells: a systematic review of clinical and basic research

OBJECTIVE

To review the effects of different immunosuppressive drugs on proliferation and function of regulatory T cells (Tregs).

METHODS

We searched MEDLINE, Embase (from inception to September 2009), and the Cochrane Library (Issue 4, 2009) for clinical and basic research about the effects of various immunosuppressive drugs on Tregs. Data were extracted and methodological quality was assessed by two independent reviewers. Outcome measures for clinical research included blood Tregs levels, acute rejection episodes, and graft function. Outcomes for basic research included percentage of Tregs proliferation, function, Tregs phenotype, and evidence for possible mechanisms. We analyzed data qualitatively.

RESULTS

Forty-two studies, including 19 clinical trials and 23 basic studies, were included. The immunosuppressive drugs studied were calcineurin inhibitors (CNIs), Rapa, anti-metabolism drugs, IL-2 receptor-blocking antibodies, T-cell depleting antibodies, and co-stimulation blockade antibodies. Most of the studies were on Rapa and CNIs. Eight basic studies on Rapa and CNIs showed that Rapa could promote the proliferation and function of Tregs, while CNIs could not. Five clinical trials involving a total of 158 patients showed that patients taking Rapa had higher blood concentration of Tregs than patients taking CNIs, but no difference was found in graft function (6-42 months follow-up).

CONCLUSION

There is substantial evidence that Rapa favors Tregs survival and function. However, the higher numbers of blood Tregs in patients treated with Rapa do not show any association with better graft function. Larger clinical studies with longer follow-up are needed to more thoroughly assess the efficacy of immunosuppressive drugs on Tregs, and reveal whether a relationship exists between Tregs and graft function.

Therapeutic manipulation of immune tolerance in allergic disease

Immune tolerance - the adaptation of the immune system to external antigens or allergens - might be therapeutically manipulated to restore normal immunity in conditions such as allergy, asthma and autoimmune diseases. The field of allergen-specific immunotherapy is experiencing exciting and novel developments for the treatment of allergic and autoimmune diseases, and recent insights into the reciprocal regulation and counter-balance between different T-cell subsets is foreseen to facilitate new strategies for immunointervention. This Review highlights current knowledge of immunomodulatory therapies for the manipulation of immune tolerance and highlights recent approaches to improve allergen-specific immunotherapy for the treatment of allergic diseases.