Regulatory T-cell therapy in the induction of transplant tolerance: the issue of subpopulations

Clinical tolerance induction to permit minimization or cessation of immunosuppressive drugs is one of the key research goals in solid organ transplantation. The use of ex vivo expanded or manipulated immunologic cells, including CD4CD25FOXP3 regulatory T cells (Tregs), to achieve this aim is already a reality, with several trials currently recruiting patients. Tregs are a highly suppressive, nonredundant, population of regulatory cells that prevent the development of autoimmune diseases in mammals. Data from transplanted humans and animal models support the notion that Tregs can mediate both induction and adoptive transfer of transplantation tolerance. However, human Tregs are highly heterogeneous and include subpopulations with the potential to produce the proinflammatory cytokine interleukin-17, which has been linked to transplant rejection. Tregs are also small in number in the peripheral circulation, thus they require ex vivo expansion before infusion into man. Selection of the most appropriate Treg population for cell therapy is, therefore, a critical step in ensuring successful clinical outcomes. In this review, we discuss Treg subpopulations, their subdivision based on nonmutually exclusive criteria of origin, expression of immunologic markers and function, availability in the peripheral blood of patients awaiting transplantation, and their suitability for programs of cell-based therapy.

Results of the 4th scientific workshop of the ECCO (Group II): markers of intestinal fibrosis in inflammatory bowel disease

The fourth scientific workshop of the European Crohn's and Colitis Organization (ECCO) focused on intestinal fibrosis in inflammatory bowel disease (IBD). The objective was to better understand basic mechanisms and markers of intestinal fibrosis as well as to suggest new therapeutic targets to prevent or treat fibrosis. The results of this workshop are presented in three separate manuscripts. This section describes markers of fibrosis in IBD, identifies unanswered questions in the field and provides a framework for future studies addressing the unmet needs in the field of intestinal fibrosis.

Efficacy of immunosuppression monotherapy after liver transplantation: A meta-analysis

AIM: To assess the advantages and disadvantages of immunosuppression monotherapy after transplantation and the impact of monotherapy on hepatitis C virus (HCV) recurrence.

METHODS: Articles from Cochrane Hepato-Biliary Group Controlled Trials Register, the Cochrane Central Register of Controlled Trials in The Cochrane Library, MEDLINE, EMBASE, and Science Citation Index Expanded, including non-English literature identified in these databases, were searched up to January 2013. We included randomized clinical trials comparing various immunosuppression monotherapy and prednisone-based immunosuppression combinations for liver transplantation. The modified Jadad scale score or the Oxford quality scoring system was used. Meta-analyses were performed with weighted random-effects models.

RESULTS: A total of 14 randomized articles including 1814 patients were identified. Eight trials including 1214 patients compared tacrolimus monotherapy (n = 610) vs tacrolimus plus steroids or triple therapy regarding acute rejection and adverse events (n = 604). Five trials, including 285 patients, compared tacrolimus monotherapy (n = 143) vs tacrolimus plus steroids or triple therapy regarding hepatitis C recurrence (n = 142). Four trials including 273 patients compared cyclosporine monotherapy (n = 148) vs cyclosporine and steroids regarding acute rejection and adverse events (n = 125). Two trials including 170 patients compared mycophenolate mofetil monotherapy (n = 86) vs combinations regarding acute rejection (n = 84). There were no significant differences in the acute rejection rates between tacrolimus monotherapy (RR = 1.04, P = 0.620), and cyclosporine monotherapy (RR = 0.89, P = 0.770). Mycophenolate mofetil monotherapy had a significant increase in the acute rejection rate (RR = 4.50, P = 0.027). Tacrolimus monotherapy had no significant effects on the recurrence of hepatitis C (RR = 1.03, P = 0.752). More cytomegalovirus infection (RR = 0.48, P = 0.000) and drug-related diabetes mellitus (RR = 0.54, P = 0.000) were observed in the immunosuppression combination therapy groups.

CONCLUSION: Tacrolimus and cyclosporine monotherapy may be as effective as immunosuppression combination therapy. Mycophenolate mofetil monotherapy was not considerable. Tacrolimus monotherapy does not increase recurrence of HCV.

Impact of immunosuppression minimization and withdrawal in long-term hepatitis C virus liver transplant recipients

AIM

To investigate the effects of different immunosuppressive regimens and avoidance on fibrosis progression in hepatitis C virus (HCV) liver transplant (LT) recipients.

METHODS

We retrospectively compared the liver biopsies of well-matched HCV LT recipients under calcineurin inhibitors (CNI group, n = 21) and mycophenolate (MMF group, n = 15) monotherapy, with those patients who successfully withdrawn immunosuppression (IS) therapy from at least 3 years (TOL group, n = 10). To perform the well-matched analysis, all HCV transplanted patients from December 1993 were screened. Only those HCV patients who reached the following criteria were considered for the analysis: (1) at least 3 years of post-operative follow-up; (2) patients with normal liver graft function under low dose CNI monotherapy (CNI group); (3) patients with normal liver graft function under antimetabolite (Micophenolate Mofetil or coated mycophenolate sodium) monotherapy (MMF group); and (4) recipients with normal liver function without any IS. We excluded from the analysis recipients who were IS free or under monotherapy for < 36 mo, recipients with cirrhosis or with unstable liver function tests.

RESULTS

Thirty six recipients were enrolled in the study. Demographics, clinical data, time after LT and baseline liver biopsies were comparable in the three groups. After six years of follow-up, there was no worsening of hepatic fibrosis in the MMF group (2.5 ± 1.5 Ishak Units vs 2.9 ± 1.7 Ishak Units, P = 0.5) and TOL group (2.7 ± 10.7 vs 2.5 ± 1.2, P = 0.2). In contrast, a significant increase in the fibrosis score was observed in the CNI group (2.2 ± 1.7 vs 3.9 ± 1.6, P = 0.008). The yearly fibrosis progression rate was significantly worse in the CNI group (0.32 ± 0.35) vs MMF group (0.03 ± 0.31, P = 0.03), and TOL group (-0.02 ± 0.27, P = 0.02). No differences have been reported in grading scores for CNI group (2.79 ± 1.9, P = 0.7), MMF group (3.2 ± 1.5, P = 0.9) and TOL group (3.1 ± 1.4, P = 0.2). Twenty four patients were treated with low dose ribavirin (8 TOL, 7 MMF, 9 CNI). The hepatitis C titers were comparable in the three groups. No episodes of rejection have been reported despite differences of liver function test in the three groups during the observational period.

CONCLUSION

IS withdrawal and MMF monotherapy is safe and seems to be associated with the slowest fibrosis progression in HCV LT recipients.

Construction of an shRNA expression vector targeting the Crk gene: Potential role of Crk in liver fibrosis

AIM: To construct a short-hairpin RNA (shRNA) eukaryotic expression vector targeting the v-Crk avian sarcoma virus CT10 oncogene homolog gene (Crk) and to study the potential role of Crk in liver fibrosis.

METHODS: The shRNA oligonucleotide fragments were designed and synthesized based on the sequence of Crk mRNA. Double strands were then formed after annealing and inserted into the plko vector. Recombinant lentiviral vector was transfected into 293T cells to package lentivirus. LX-2 cells were then infected with the recombinant lentivirus and the function of Crk was studied after infection.

RESULTS: RT-PCR and Western bolt analyses indicated that after successful infection, both mRNA and protein expression was dramatically down-regulated, compared with the control group. Knockdown of Crk decreased the expression of collagen type 1 (Col1), α-smooth muscle actin (α-SMA) and the capacity of cell migration, but had no effect on cell proliferation.

CONCLUSION: We have successfully constructed an shRNA eukaryotic expression vector targeting the Crk gene. Knockdown of Crk can inhibit liver fibrosis possibly by suppressing the activation and migration of LX-2 cells.

Post-liver transplant hepatitis C virus recurrence: an unresolved thorny problem

Hepatitis C virus (HCV)-related cirrhosis represents the leading cause of liver transplantation in developed, Western and Eastern countries. Unfortunately, liver transplantation does not cure recipient HCV infection: reinfection universally occurs and disease progression is faster after liver transplant. In this review we focus on what happens throughout the peri-transplant phase and in the first 6-12 mo after transplantation: during this crucial period a completely new balance between HCV, liver graft, the recipient's immune response and anti-rejection therapy is achieved that will deeply affect subsequent outcomes. Nearly all patients show an early graft reinfection, with HCV viremia reaching and exceeding pre-transplant levels; in this setting, histological assessment is essential to differentiate recurrent hepatitis C from acute or chronic rejection; however, differentiating the two patterns remains difficult. The host immune response (mainly cellular mediated) appears to be crucial both in the control of HCV infection and in the genesis of rejection, and it is also strongly influenced by immunosuppressive treatment. At present no clear immunosuppressive strategy could be strongly recommended in HCV-positive recipients to prevent HCV recurrence, even immunotherapy appears to be ineffective. Nonetheless it seems reasonable that episodes of rejection and over-immunosuppression are more likely to enhance the risk of HCV recurrence through immunological mechanisms. Both complete prevention of rejection and optimization of immunosuppression should represent the main goals towards reducing the rate of graft HCV reinfection. In conclusion, post-transplant HCV recurrence remains an unresolved, thorny problem because many factors remain obscure and need to be better determined.

Iron metabolism in transplantation

Recipient's iron status is an important determinant of clinical outcome in transplantation medicine. This review addresses iron metabolism in solid organ transplantation, where the role of iron as a mediator of ischemia-reperfusion injury, as an immune-modulatory element, and as a determinant of organ and graft function is discussed. Although iron chelators reduce ischemia-reperfusion injury in cell and animal models, these benefits have not yet been implemented into clinical practice. Iron deficiency and iron overload are associated with reduced immune activation, whose molecular mechanisms are reviewed in detail. Furthermore, iron overload and hyperferritinemia are associated with poor prognosis in end-stage organ failure in patients awaiting kidney, or liver transplantation. This negative prognostic impact of iron overload appears to persist after transplantation, which highlights the need for optimizing iron management before and after solid organ transplantation. In contrast, iron deficiency and anemia are also associated with poor prognosis in patients with end-stage heart failure. Intravenous iron supplementation should be managed carefully because parenterally induced iron overload could persist after successful transplantation. In conclusion, current evidence shows that iron overload and iron deficiency are important risk factors before and after solid organ transplantation. Iron status should therefore be actively managed in patients on the waiting list and after transplantation.

Immunosuppression: trends and tolerance?

Advances in pharmacologic immunosuppression are responsible for the excellent outcomes experienced by recipients of liver transplants. However, long-term follow-up of these patients reveals an increasing burden of morbidity and mortality that is attributable to these drugs. The authors summarize the agents used in contemporary liver transplantation immunosuppression protocols and discuss the emerging trend within the community to minimize or eliminate these agents from use. The authors present recently published data that may provide the foundation for immunosuppression minimization or tolerance induction in the future and review studies that have focused on the utility of biomarkers in guiding immunosuppression management.

Effect of mycophenolate mofetil on progression of interstitial fibrosis and tubular atrophy after kidney transplantation: a retrospective study

OBJECTIVES

Chronic transplant dysfunction after kidney transplantation is a major reason of kidney graft loss and is caused by immunological and non-immunological factors. There is evidence that mycophenolate mofetil (MMF) may exert a positive effect on renal damage in addition to immunosuppression, by its direct antifibrotic properties. The aim of our study was to retrospectively investigate the role of MMF doses on progression of chronic allograft dysfunction and fibrosis and tubular atrophy (IF/TA).

SETTING

Retrospective, cohort study.

PARTICIPANTS

Patients with kidney transplant in a tertiary care institution. This is a retrospective cohort study that included 79 patients with kidney and kidney-pancreas transplantation. Immunosuppression consisted of anti-interleukin 2 antibody induction, MMF, a calcineurin inhibitor±steroids.

PRIMARY OUTCOME MEASURES

An association of average MMF doses over 1 year post-transplant with progression of interstitial fibrosis (Δci), tubular atrophy (Δct) and estimated-creatinine clearance (eCrcl) at 1 year post-transplant was evaluated using univariate and multivariate analyses.

RESULTS

A higher average MMF dose was significantly independently associated with better eCrcl at 1 year post-transplant (b=0.21±0.1, p=0.04). In multiple regression analysis lower Δci (b=-0.2±0.09, p=0.05) and Δct (b=-0.29±0.1, p=0.02) were independently associated with a greater average MMF dose. There was no correlation between average MMF doses and incidence of acute rejection (p=0.68).

CONCLUSIONS

A higher average MMF dose over 1 year is associated with better renal function and slower progression of IF/TA, at least partly independent of its immunosuppressive effects.

Report of the joint ESOT and TTS basic science meeting 2013: current concepts and discoveries in translational transplantation

A joint meeting organized by the European (ESOT) and The Transplantation (TTS) Societies for basic science research was organized in Paris, France, on November 7-9, 2013. Focused on new ideas and concepts in translational transplantation, the meeting served as a venue for state-of-the-art developments in basic transplantation immunology, such as the potential for tolerance induction through regulation of T-cell signaling. This meeting report summarizes important insights which were presented in Paris. It not only offers an overview of established aspects, such as the role of Tregs in transplantation, presented by Nobel laureate Rolf Zinkernagel, but also highlights novel facets in the field of transplantation, that is cell-therapy-based immunosuppression or composite tissue transplantation as presented by the emotional story given by Vasyly Rohovyy, who received two hand transplants. The ESOT/TTS joint meeting was an overall productive and enjoyable platform for basic science research in translational transplantation and fulfilled all expectations by giving a promising outlook for the future of research in the field of immunological transplantation research.

Targeting the PI3K/mTOR Pathway in Pediatric Hematologic Malignancies

A complex interplay of intracellular signaling networks orchestrates normal cell growth and survival, including translation, transcription, proliferation, and cell cycle progression. Dysregulation of such signals occurs commonly in many malignancies, thereby giving the cancer cell a survival advantage, but also providing possible targets for therapeutic intervention. Activation of the phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt)/mammalian target of rapamycin (mTOR) signaling pathway contributes to the proliferative advantage of malignant cells and may confer resistance to chemotherapy in various hematologic malignancies. The initial mTOR inhibitor, sirolimus (also known as rapamycin), was first discovered in 1975 in the soil of Easter Island. Sirolimus was originally developed as an anti-fungal agent given its macrolide properties, but was approved by the Food and Drug Administration (FDA) in 1999 as an immunosuppressive agent for renal transplantation patients once its T cell suppression characteristics were recognized. Shortly thereafter, recognition of sirolimus's ability to inhibit cellular proliferation and cell cycle progression brought sirolimus to the forefront as a possible inhibitor of mTOR. In the subsequent decade, the functional roles of the mTOR protein have been more fully elucidated, and this protein is now known to be a key regulator in a highly complex signaling pathway that controls cell growth, proliferation, metabolism, and apoptosis. This article discusses the dysregulation of PI3K/mTOR signaling in hematologic malignancies, including acute and chronic leukemias, lymphomas, and lymphoproliferative disorders. The current repertoire of PI3K/mTOR pathway inhibitors in development and clinical trials to date are described with emphasis upon pediatric hematologic malignancies (Figure 1). Investigation of small molecule inhibitors of this complex signaling network is an active area of oncology drug development.

Liver transplantation: Fifty years of experience

Since 1963, when the first human liver transplantation (LT) was performed by Thomas Starzl, the world has witnessed 50 years of development in surgical techniques, immunosuppression, organ allocation, donor selection, and the indications and contraindications for LT. This has led to the mainstream, well-established procedure that has saved innumerable lives worldwide. Today, there are hundreds of liver transplant centres in over 80 countries. This review aims to describe the main aspects of LT regarding the progressive changes that have occurred over the years. We herein review historical aspects since the first experimental studies and the first attempts at human transplantation. We also provide an overview of immunosuppressive agents and their potential side effects, the evolution of the indications and contraindications of LT, the evolution of survival according to different time periods, and the evolution of methods of organ allocation.

Liver transplantation for pediatric metabolic disease

Liver transplantation (LTx) was initially developed as a therapy for liver diseases known to be associated with a high risk of near-term mortality but is based upon a different set of paradigms for inborn metabolic diseases. As overall outcomes for the procedure have improved, LTx has evolved into an attractive approach for a growing number of metabolic diseases in a variety of clinical situations. No longer simply life-saving, the procedure can lead to a better quality of life even if not all symptoms of the primary disorder are eliminated. Juggling the risk-benefit ratio thus has become more complicated as the list of potential disorders amenable to treatment with LTx has increased. This review summarizes presentations from a recent conference on metabolic liver transplantation held at the Children's Hospital of Pittsburgh of UPMC on the role of liver or hepatocyte transplantation in the treatment of metabolic liver disease.

Excessive immunosuppression as a potential cause of poor survival in simultaneous liver/kidney transplantation for hepatitis C

Appropriate recipient selection of simultaneous liver/kidney transplantation (SLKT) remains controversial. In particular, data on liver graft survival in hepatitis C virus-infected (HCV+) SLKT recipients are lacking. We conducted a single-center, retrospective study of HCV+ SLKT recipients (N = 25) in comparison with HCV- SLKT (N = 26) and HCV+ liver transplantation alone (LTA, N = 296). Despite backgrounds of HCV+ and HCV- SLKT being similar, HCV+ SLKT demonstrated significantly impaired 5-year liver graft survival of 35% (HCV- SLKT, 79%, P = 0.004). Compared with HCV+ LTA, induction immunosuppression was more frequently used in HCV+ SLKT. Five-year liver graft survival rate for HCV+ SLKT was significantly lower than that for LTA (35% vs. 74%, respectively, P < 0.001). Adjusted hazard ratio of liver graft loss in HCV+ SLKT was 4.9 (95% confidence interval 2.0-12.1, P = 0.001). HCV+ SLKT recipients were more likely to succumb to recurrent HCV and sepsis compared with LTA (32% vs. 8.8%, P < 0.001 and 24% vs. 8.8%, P = 0.030, respectively). Ten HCV+ SLKT recipients underwent anti-HCV therapy for recurrent HCV; only 1 achieved sustained virological response. HCV+ SLKT is associated with significantly decreased long-term prognosis compared with HCV- SLKT and HCV+ LTA.

Prospects for therapeutic tolerance in humans

PURPOSE OF REVIEW

To provide an overview of recent advances and future possibilities for therapeutic tolerance.

RECENT FINDINGS

Allograft survival despite complete immunosuppressant withdrawal has been demonstrated in selected renal-transplant recipients with haematopoietic chimerism. Early clinical trials of mesenchymal stromal cell therapy have shown promising results in several autoimmune diseases. Regulatory T cells show potential benefit in graft versus host disease, although challenges to ex-vivo expansion remain. Targeted modulation of T-cell function in vivo with monoclonal antibodies has shown beneficial effects in phase II/III trials of multiple sclerosis (alemtuzumab) and type I diabetes mellitus (teplizumab, otelixizumab). Emerging data from animal models suggest an important role for the commensal microbiome in the maintenance and disruption of immune tolerance with parallels in human studies.

SUMMARY

After years of slow progress, recent research has reduced the translational gap between animal models and clinical therapeutic tolerance. Early detection of autoimmunity, potentially at preclinical stages, offers a window of opportunity for tolerogenic therapy. Reliable biomarkers of tolerance are urgently needed to provide objective measurements of the effectiveness of tolerogenic therapies, and to allow intelligent immunosuppressant withdrawal in patients whose autoimmune disease is stable.

VIDEO ABSTRACT AVAILABLE

See the Video Supplementary Digital Content 1 (http://links.lww.com/COR/A8).

Gene expression analysis by qPCR in clinical kidney transplantation

Patients with a kidney transplant may encounter chronic dysfunction of their graft. Once damage in the graft has established, therapeutic intervention is less efficient. Clinical parameters and morphologic evaluation of biopsies are used for determining diagnosis and prognosis of the patient. Quantitative polymerase chain reaction (qPCR) may be integrated in clinical practice to facilitate routine diagnostics, risk assessment with respect to graft outcome, and determination of the response to therapy by the patient. The success of qPCR assays is highly dependent on the adequacy of the methodological procedures performed. Here, we describe tips and tricks for processing patient material, RNA analysis, and qPCR primer design and gene expression analyses.

Conversion from Prograf to Advagraf in stable paediatric renal transplant patients and 1-year follow-up

BACKGROUND

The conversion from Prograf to Advagraf on a 1:1 (mg:mg) basis has been questioned in light of the publication of studies showing a decrease in tacrolimus blood concentrations after the administration of Advagraf.

METHODS

The bioavailability of Prograf and Advagraf was evaluated in an open-label conversion study in 21 stable renal transplant paediatric patients. Serial blood samples for determining tacrolimus levels were collected during a 24-h period before (on Prograf) and after (on Advagraf) conversion. Tacrolimus pharmacokinetic parameters were calculated using a non-compartmental approach and the relative bioavailability calculated. Clinical and analytical data were obtained at 30, 90, 180 and 360 days after study enrolment.

RESULTS

The mean ratio and 90 % confidence interval (CI) for peak plasma drug concentration (C(max)) and the area under the time-concentration curve during the first 24 h (AUC(0-24)) were 81.54 (95 % CI 71.6-92.87) and 87.19 (95 % CI 79.91-95.13), respectively. Renal glomerular filtration rate remained stable over the course of the follow-up. Two patients presented clinical events unrelated to tacrolimus. Tacrolimus levels decreased in the first month, the dose/level ratio increased between months 1 and 6 and slight dose adjustments were required during the follow-up period.

CONCLUSIONS

Our results show that Advagraf bioequivalence cannot be ensured in this population. Significant changes in tacrolimus levels and dose were observed on long-term follow-up.

Long term outcomes after pediatric liver transplantation

Long term outcomes after liver transplantation are major determinants of quality of life and of the value of this heroic treatment. As short term outcomes are excellent, our community is turning to take a harder look at long term outcomes. The purpose of this paper is to review these outcomes, and highlight proposed treatments, as well as pressing topics needing to be studied. A systemic review of the English literature was carried in PubMed, covering all papers addressing long term outcomes in pediatric liver transplant from 2000-2013. Late outcomes after pediatric liver transplant affect the liver graft in the form of chronic liver dysfunction. The causes include rejection particularly humoral rejection, but also de novo autoimmune hepatitis, and recurrent disease. The metabolic syndrome is a major factor in long term cardiovascular complication risk. Secondary infections, kidney dysfunction and malignancy remain a reality of those patients. There is growing evidence of late cognitive and executive function delays affecting daily life productivity as well as likely adherence. Finally, despite a good health status, quality of life measures are comparable to those of children with chronic diseases. Long term outcomes are the new frontier in pediatric liver transplantation. Much is needed to improve graft survival, but also to avoid systemic morbidities from long term immunosuppression. Quality of life is a new inclusive measure that will require interventions and innovative approaches respectful not only on the patients but also of their social circle.

Prospective multicenter clinical trial of immunosuppressive drug withdrawal in stable adult liver transplant recipients

Lifelong immunosuppression increases morbidity and mortality in liver transplantation. Discontinuation of immunosuppressive drugs could lessen this burden, but the safety, applicability, and clinical outcomes of this strategy need to be carefully defined. We enrolled 102 stable liver recipients at least 3 years after transplantation in a single-arm multicenter immunosuppression withdrawal trial. Drugs were gradually discontinued over a 6 to 9-month period. The primary endpoint was the development of operational tolerance, defined as successful immunosuppressive drug cessation maintained for at least 12 months with stable graft function and no histopathologic evidence of rejection. Out of the 98 recipients evaluated, 57 rejected and 41 successfully discontinued all immunosuppressive drugs. In nontolerant recipients rejection episodes were mild and resolved over 5.6 months (two nontolerant patients still exhibited mild gradually improving cholestasis at the end of follow-up). In tolerant recipients no progressive clinically significant histological damage was apparent in follow-up protocol biopsies performed up to 3 years following drug withdrawal. Tolerance was independently associated with time since transplantation (odds ratio [OR] 1.353; P = 0.0001), recipient age (OR 1.073; P = 0.009), and male gender (OR 4.657; P = 0.016). A predictive model incorporating the first two clinical variables identified subgroups of recipients with very high (79%), intermediate (30%-38%), and very low (0%) likelihood of successful withdrawal.

CONCLUSION

When conducted at late timepoints after transplantation, immunosuppression withdrawal is successful in a high proportion of carefully selected liver recipients. A combination of clinical parameters could be useful to predict the success of this strategy. Additional prospective studies are now needed to confirm these results and to validate clinically applicable diagnostic biomarkers.

Estrogen-dependent changes in serum iron levels as a translator of the adverse effects of estrogen during infection: a conceptual framework

Elevated levels of estrogen often associate with increased susceptibility to infection. This has been attributed to the ability of estrogen to concomitantly enhance the growth and virulence of pathogens and suppress host immunity. But the exact mechanism of how estrogen mediates such effects, especially in cases where the pathogen and/or the immune components in question do not express estrogen receptors, has yet to be elucidated. Here we propose that translating the adverse effects of estrogen during infection is dependent to a significant degree upon its ability to manipulate iron homeostasis. For elevated levels of estrogen alter the synthesis and/or activity of several factors involved in iron metabolism including hypoxia inducible factor 1α (HIF-1α) and hepcidin among others. This leads to the inhibition of hepcidin synthesis in hepatocytes and the maintenance of ferroportin (FPN) integrity on the surface of iron-releasing duodenal enterocytes, hepatocytes, and macrophages. Intact FPN permits the continuous efflux of dietary and stored iron into the circulation, which further enhances pathogen growth and virulence on the one hand and suppresses host immunity on the other. This new conceptual framework may help explain a multitude of disparate clinical and experimental observations pertinent to the relationship between estrogen and infection.

Immunosuppression minimization vs. complete drug withdrawal in liver transplantation

Despite the increase in long-term survival, liver transplant recipients still exhibit higher morbidity and mortality than the general population. This is in part attributed to the lifelong administration of immunosuppression and its associated side effects. Several studies reported in the last decades have evaluated the impact of immunosuppression minimization in liver transplant recipients, but results have been inconsistent due to the heterogeneity of study designs and insufficient sample sizes. On the other hand, complete immunosuppression withdrawal has proven to be feasible in approximately 20% of carefully selected liver transplant recipients, especially in older patients and those with longer duration after transplantation. The long-term risks and clinical benefits of this strategy, however, also need to be clarified. As a consequence, and despite the general perception that a large proportion of liver recipients are over-immunosuppressed, it is currently not possible to derive evidence-based guidelines on how to manage long-term immunosuppression to improve clinical outcomes. Large clinical trials of drug minimization and/or withdrawal focused on clinically-relevant long-term outcomes are required. Development of personalized medicine tools and a deeper understanding of the pathogenesis of idiopathic inflammatory graft lesions will be pre-requisites to achieve these goals.

Biomarkers of tolerance

PURPOSE OF REVIEW

As the induction and maintenance of donor-specific tolerance is a central aim in solid organ transplantation, it is essential that clinicians are able to identify and monitor tolerance accurately and reliably. This review highlights recent advances in defining sets of biomarkers in noninvasive samples that may guide minimization and withdrawal of immunosuppression in tolerant recipients.

RECENT FINDINGS

Recent studies in liver and kidney transplant recipients have identified distinct biomarker profiles that are associated with operational tolerance. Although there is some heterogeneity in the findings of these studies, these have suggested novel cellular mechanisms for the development of tolerance.

SUMMARY

Multiple platforms such as microarray gene expression analysis, flow cytometry, and immune cell functional assays have been used to discover and validate composite sets of biomarkers, which identify recipients with operational tolerance both in liver and kidney transplantation. These studies suggest that distinct cellular and molecular mechanisms lead to the development of tolerance in different transplanted organs. These putative biomarker profiles now need to be validated prospectively in trials of immunosuppression withdrawal and in novel approaches to induce transplant tolerance.

Organ bioengineering and regeneration as the new Holy Grail for organ transplantation

Organ transplantation is a victim of its own success. In view of the excellent results achieved to date, the demand for organs is escalating whereas the supply has reached a plateau. Consequently, waiting times and mortality on the waiting list are increasing dramatically. Recent achievements in organ bioengineering and regeneration have provided proof of principle that the application of organ bioengineering and regeneration technologies to manufacture organs for transplant purposes may offer the quickest route to clinical application. As investigators are focusing their interest on the utilization and manipulation of autologous cells, ideally the end product will be the equivalent of an autograft such that the recipient will not require any antirejection medication. Achievement of an immunosuppression-free state has been pursued but has proven to be a difficult odyssey since the early days of the transplant era, yet an immediate, stable, durable, and reproducible immunosuppression-free state remains an unfulfilled quest. As organ bioengineering and regeneration has shown the potential to meet both the needs for a new source of organs that may eclipse the increasing organ demand and an immunosuppression-free state, advances in this field could become the new Holy Grail for transplant sciences.

Mechanisms and rescue strategies of calcineurin inhibitor mediated tolerance abrogation induced by anti-CD4 mAb treatment

To ensure safety tolerance induction protocols are accompanied by conventional immunosuppressive drugs (IS). But IS such as calcineurin inhibitors (CNI), for example, cyclosporin A (CsA), can interfere with tolerance induction. We investigated the effect of an additional transient CsA treatment on anti-CD4mAb-induced tolerance induction upon rat kidney transplantation. Additional CsA treatment induced deteriorated graft function, resulting in chronic rejection characterized by glomerulosclerosis, interstitial fibrosis, tubular atrophy and vascular changes. Microarray analysis revealed enhanced intragraft expression of the B cell attracting chemokine CXCL13 early during CsA treatment. Increase in CXCL13 expression is accompanied by enhanced B cell infiltration with local and systemic IgG production and C3d deposition as early as 5 days upon CsA withdrawal. Adding different CNIs to cultures of primary mesangial cells isolated from glomeruli resulted in a concentration-dependent increase in CXCL13 transcription. CsA in synergy with TNF-α can enhance the B cell attracting and activating potential of mesangial cells. Transient B cell depletion or transfer of splenocytes from tolerant recipients 3 weeks after transplantation could rescue tolerance induction and did inhibit intragraft B cell accumulation, alloantibody production and ameliorate chronic rejection.

Trial of complete weaning from immunosuppression for liver transplant recipients: factors predictive of tolerance

Recipients of liver transplantation (LT) may develop immunological tolerance. Factors predictive of tolerance are not clearly understood. Transplant recipients with normal liver function tests and without active viral hepatitis or autoimmune disease who presented with side effects of immunosuppression or a high risk of de novo malignancies were selected to participate in this prospective study. Twenty-four patients fulfilled the inclusion criteria and, therefore, underwent a gradual reduction of immunosuppression. Tolerance was defined as normal liver function tests after immunosuppression withdrawal. Basal clinical and immunological characteristics, including lymphocyte counts and subpopulations (T, B, natural killer, CD4(+) , CD8(+) , and regulatory T cells) and the phytohemagglutinin stimulation index (SI), were compared for tolerant and nontolerant patients. Fifteen of the 24 patients (62.5%) were tolerant at a median of 14 months (interquartile range = 8.5-22.5 months) after complete immunosuppression withdrawal. Tolerant patients had a longer median interval between transplantation and inclusion in the study (156 for tolerant patients versus 71 months for nontolerant patients, P = 0.003) and a lower median SI (7.49 for tolerant patients versus 41.73 for nontolerant patients, P = 0.01). We identified 3 groups of patients with different probabilities of tolerance: in the first group (n = 7 for an interval > 10 years and an SI < 20), 100% reached tolerance; in the second group (n = 10 for an interval > 10 years and an SI > 20 or an interval < 10 years and an SI < 20), 60% reached tolerance; and in the third group (n = 7 for an interval < 10 years and an SI > 20), 29% reached tolerance. In conclusion, a high proportion of select LT recipients can reach tolerance over the long term. Two simple basal variables-the time from transplantation and the SI-may help to identify these patients.

PI3Kδ inhibition augments the efficacy of rapamycin in suppressing proliferation of Epstein-Barr virus (EBV)+ B cell lymphomas

Posttransplant lymphoproliferative disorder (PTLD) continues to be a devastating and potentially life-threatening complication in organ transplant recipients. PTLD is associated with EBV infection and can result in malignant B cell lymphomas. Here we demonstrate that the PI3K/Akt/mTOR pathway is highly activated in EBV+ B cell lymphoma lines derived from patients with PTLD. Treatment with the mTORC1 inhibitor Rapamycin (RAPA) partially inhibited the proliferation of EBV+ B cell lines. Resistance to RAPA treatment correlated with high levels of Akt phosphorylation. An mTORC1/2 inhibitor and a PI3K/mTOR dual inhibitor suppressed Akt phosphorylation and showed a greater anti-proliferative effect on EBV+ B lymphoma lines compared to RAPA. EBV+ B cell lymphoma lines expressed high levels of PI3Kδ. We demonstrate that PI3Kδ is responsible for Akt activation in EBV+ B cell lymphomas, and that selective inhibition of PI3Kδ by either siRNA, or a small molecule inhibitor, augmented the anti-proliferative effect of RAPA on EBV+ B cell lymphomas. These results suggest that PI3Kδ is a novel, potential therapeutic target for the treatment of EBV-associated PTLD and that combined blockade of PI3Kδ and mTOR provides increased efficacy in inhibiting proliferation of EBV+ B cell lymphomas.

Metastatic renal cell carcinoma: update on epidemiology, genetics, and therapeutic modalities

The treatment of advanced renal cell carcinoma (RCC) remains a major therapeutic challenge for clinicians. Despite advances in the understanding of the immunobiology of RCC and the availability of several novel targeted agents, there has been little improvement in the survival of patients with metastatic RCC. This review will focus on the recent understanding of risk factors and treatment options and outcomes of metastatic RCC, in particular, targeted therapeutic agents that inhibit vascular endothelial growth factor and mammalian target of rapamycin pathways. Prospective studies are required to determine whether sequential targeted therapy will further improve progression-free survival in RCC. Ongoing research to develop novel agents with better tolerability and enhanced efficacy in the treatment of metastatic RCC is required.

Tissue biopsy monitoring of operational tolerance in liver allograft recipients

PURPOSE OF REVIEW

Highly selected, long-surviving, liver allograft recipients with normal/near normal liver injury tests can be weaned from immunosuppression. Baseline biopsies document changes before weaning and can help stratify risk of rejection or dysfunction after weaning; biopsies after weaning are used to study mechanisms of operational tolerance and to monitor for subclinical events.

RECENT FINDINGS

Clinicopathological features associated with successful weaning include a lack of sensitization [negative donor-specific antibodies (DSA) and lack of tissue C4d deposits]; 'inexperienced' recipient immune system with limited potential for cross-reactivity (less immunological memory; infant recipients); noninflamed allograft in those with nonviral, nonimmunological original diseases; upregulation of liver genes associated with iron metabolism; allograft colonization with 'immunosuppressive' cells (Treg and γδ-1>γδ-2); and longer time on immunosuppression, which might signal slow clonal deletion or silencing. The differential diagnosis of histopathological findings detected before and after weaning includes emerging infections, typical and atypical cellular rejection, indolent antibody-mediated rejection, 'autoimmunity', and other causes of progressive fibrosis.

SUMMARY

Operationally tolerant liver allograft recipients can be successfully managed with very low, and sometimes no immunosuppression, but challenges exist. Newer approaches to tissue pathology and tissue, serum, and cross-platform analytics are needed to predict successful weaning and to monitor for subclinical events.

Tolerogenic dendritic cell therapy for rheumatoid arthritis: where are we now?

Dendritic cells with tolerogenic function (tolDC) have become a promising immunotherapeutic tool for reinstating immune tolerance in rheumatoid arthritis (RA) and other autoimmune diseases. The concept underpinning tolDC therapy is that it specifically targets the pathogenic autoimmune response while leaving protective immunity intact. Findings from human in-vitro and mouse in-vivo studies have been translated into the development of clinical grade tolDC for the treatment of autoimmune disorders. Recently, two tolDC trials in RA and type I diabetes have been carried out and other trials are in progress or are imminent. In this review, we provide an update on tolDC therapy, in particular in relation to the treatment of RA, and discuss the challenges and the future perspectives of this new experimental immunotherapy.

The pits and pearls in translating operational tolerance biomarkers into clinical practice

PURPOSE OF REVIEW

This review highlights the importance and the role of key biomarker studies in liver and kidney transplant tolerance, discusses the most recent findings with respect to organ-type and cell-type specificity in blood and tissue, and points out the novel research directions in the field of immunological tolerance that involve both adult and pediatric recipients.

RECENT FINDINGS

Recent studies indicate that biomarkers for solid organ transplant tolerance are distinct with respect to organ type and cell type, suggesting distinct tolerogenic mechanisms for different organs. In both liver and kidney transplant tolerant recipients, novel cellular mechanisms have been proposed for natural killer cells, B cells, and dendritic cells in the maintenance of stable operational tolerance.

SUMMARY

Major advances have been made with respect to the understanding of mechanisms and the process of discovery and early validation of peripheral blood biomarkers for operational transplant tolerance both in kidney and liver transplantation. These studies have shed light on the findings that these tolerance mechanisms may be organ specific, as the peripheral blood transcriptional profiling attempts by microarrays and PCR reveal distinct differences and suggest roles for specific cell types. Although these studies are mostly in adults and limited in children, the first tolerance gene signature for pediatric liver transplant tolerance suggests that there are common mechanisms, yet distinct peripheral biomarkers across age. Prospective trials and organ integrative studies are now needed to further develop these biomarkers for future clinical application in addition to expanding novel approaches such as the investigation of miRNAs to better understand the tolerance mechanisms.

Management of recurrent hepatitis C in orthotopic liver transplant recipients

End-stage liver disease and hepatocellular carcinoma from chronic hepatitis C are the most common indications for orthotopic liver transplantation and the incidence of both are projected to increase over the next decade. Recurrent hepatitis C virus infection of the allograft is associated with an accelerated progression to cirrhosis, graft loss, and death. This article presents an overview of the natural history of hepatitis C virus recurrence in liver transplant recipients and guidance on optimal management strategies.

Achieving operational tolerance in transplantation: how can lessons from the clinic inform research directions?

Since the first solid organ transplant between the Herrick twins in 1954, transplantation immunology has sought to move away from harmful immunosuppressive regimens towards tolerogenic strategies that promote long-term graft survival. This has required a concerted multinational effort with scientists and clinicians working towards a common goal. Reports of immunosuppression-free kidney and liver allograft recipients have provided the proof-of-principle, but intentional generation of tolerance in clinical transplantation is still only achieved infrequently. Recently, there have been an increasing number of encouraging developments in the field in both experimental and clinical studies. In this article, we review the latest advances in tolerance research and consider possible future barriers and solutions in achieving reliable graft acceptance in the long term.

Irreversible liver failure: treatment by transplantation: part 3 of a series on liver cirrhosis

BACKGROUND

Liver transplantation is the only established, causally directed treatment for irreversible chronic or acute liver failure.

METHODS

This review is based on papers retrieved by a selective search in the PubMed database, the index of randomized controlled trials of the European Society of Organ Transplantation, and the Cochrane database, along with an analysis of data from the authors' own center.

RESULTS

1199 liver transplantations were performed in Germany in 2011. The most common indications were alcoholic cirrhosis (28%), cirrhosis of other causes (24%), and intrahepatic tumors (20%). Among recipients, the sex ratio was nearly 1:1 and the median age was just under 50. Across Europe, the 1-, 5-, and 10-year survival rates after liver transplantation were 82%, 71% and 61%. In our own center, the Charité in Berlin, the corresponding rates were 90.4%, 79.6% and 70.3%, based on an experience of 100 to 120 cases per year. The current rate of functioning transplants five years after liver transplantation is 52.6% in Germany and 66.2% internationally. Standard immunosuppression consists of a calcineurin inhibitor, tacrolimus or cyclosporine A, and steroids. Early complications include primary functional failure of the transplant, hemorrhage, thrombosis, acute rejection, and biliary complications. Over the long term, complications that can impair the outcome include chronic rejection, biliary strictures, cardiovascular and metabolic adverse effects, nephrotoxicity, neurotoxicity, and opportunistic infections and malignancies.

CONCLUSION

Liver transplantation is a successful and well-established form of treatment that is nonetheless endangered by a shortage of donor organs and other structural and organizational difficulties.

Improved adherence to tacrolimus once-daily formulation in renal recipients: a randomized controlled trial using electronic monitoring

BACKGROUND

With effective agents available to prevent posttransplantation acute organ rejection, medication adherence becomes a key factor for successful treatment outcomes after renal transplantation. A once-daily, modified-release oral formulation of tacrolimus has been developed to simplify dosing and improve medication adherence.

METHODS

Adherence Measurement in Stable Renal Transplant Patients Following Conversion From Prograft to Advagraf is a randomized multicenter controlled trial to evaluate adherence between a tacrolimus once-daily regimen and a tacrolimus twice-daily regimen using an electronic monitor to document drug intake. After enrolment, all patients continued the twice-daily regimen for 3 months and then were randomized 2:1 between the two formulations and followed for 6 months. Adherence was decomposed into patients' persistence and implementation of each regimen.

RESULTS

Two hundred nineteen patients (45% male; 3±2 years after transplantation) were analyzed (145 once daily and 74 twice daily). At 6 months after randomization, 81.5% of the once-daily group and 71.9% of the twice-daily group remained persistent with the treatment (P=0.0824). Among patients who remained engaged with the regimen, 88.2% of the once-daily group and 78.8% of the twice-daily group (P=0.0009) took the prescribed number of daily doses. When the patients took the twice-daily regimen, the average percentage of missed doses was 11.7% in the morning and 14.2% in the evening (P=0.0035).

CONCLUSIONS

Regimen implementation of tacrolimus once daily is significantly superior to the twice-daily regimen. There was a residual prevalence of suboptimal adherence that will have to be countered by means other than reformulation and regimen simplification. Electronically compiled dosing histories provide detailed data on patient adherence that can be used for efficient medication management.

The Tor Vergata weaning of immunosuppression protocols in stable hepatitis C virus liver transplant patients: the 10-year follow-up

We report herein the 10-year outcome of the Tor Vergata weaning off immunosuppression protocol in hepatitis C virus (HCV) liver transplant patients. Thirty-four patients who had received a liver graft for HCV-related cirrhosis were enrolled in a prospective study in which they were progressively weaned off immunosuppression. The primary endpoints were feasibility and safety of the weaning; the second aim was to assess fibrosis progression. At the 10-year follow-up, of the eight original tolerant patients, six remained IS-free. Of the 26 individuals who could not be weaned, 22 were alive. When the baseline biopsies were compared with the 10-year biopsies, the tolerant group showed no differences in staging, whereas the nontolerant group showed a significant increase in staging. The fibrosis progression rates calculated for the tolerant and the nontolerant groups were -0.06 ± 0.12 and 0.1 ± 0.2, respectively (P = 0.04). Furthermore, with the last taken biopsies, nine nontolerant patients were showing frank cirrhosis versus no cirrhosis among the tolerant patients. After a 10-year follow-up of a Tor Vergata weaning protocol, 6/34 patients completed follow-up without reinstitution of immunosuppression and this appeared beneficial regarding a reduction in fibrosis progression.