Long-term renal allograft survival: have we made significant progress or is it time to rethink our analytic and therapeutic strategies?

Impact of acute rejection and new-onset diabetes on long-term transplant graft and patient survival

BACKGROUND AND OBJECTIVES

Development of new therapeutic strategies to improve long-term transplant outcomes requires improved understanding of the mechanisms by which these complications limit long-term transplant survival.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

The association of acute rejection and new-onset diabetes was determined in the first posttransplantation year with the outcomes of transplant failure from any cause, death-censored graft loss, and death with a functioning graft in 27,707 adult recipients of first kidney-only transplants, with graft survival of at least 1 yr, performed between 1995 and 2002 in the United States.

RESULTS

In multivariate analyses, patients who developed acute rejection or new-onset diabetes had a similar risk for transplant failure from any cause, but the mechanisms of transplant failure were different: Acute rejection was associated with death-censored graft loss but only weakly associated with death with a functioning graft. In contrast new-onset diabetes was not associated with death-censored graft loss but was associated with an increased risk for death with a functioning graft.

CONCLUSIONS

Acute rejection and new-onset diabetes have a similar impact on long-term transplant survival but lead to transplant failure through different mechanisms. The mechanisms by which new-onset diabetes leads to transplant failure should be prospectively studied. Targeted therapeutic strategies to minimize the impact of various early posttransplantation complications may lead to improved long-term outcomes.

Alemtuzumab (Campath-1H) in kidney transplantation

Kidney transplantation has become the treatment of choice for both the quality of life and survival in patients with end-stage renal disease (ESRD). However, the immunosuppressive regimen which allows optimal kidney transplant outcome remains elusive. One of the more promising induction agents, Alemtuzumab, was introduced to kidney transplantation by Calne in the late 1990s with low dose cyclosporine A monotherapy, with the hope of establishing 'prope' or near tolerance. Subsequent pilot studies with Alemtuzumab alone or monotherapy (DSG, Rapa) demonstrated high rates of acute rejection (AR) along with occasional humoral components that lead to abandoning the concept of Alemtuzumab as a 'magic bullet' to achieve tolerance, prope or otherwise. A number of programs (including our own) has since modified maintenance immunosuppression using low dose tacrolimus, and shown acceptable rates of AR, with relatively low incidence of viral infection and lymphoproliferative disorders along with cost benefit. However, there are only three prospective, randomized studies which are small with one year or less follow-up, and most published series utilize historical control groups with relatively short follow-up. As extrapolation from short-term data is far from secure, long-term, prospective, randomized studies with Alemtuzumab will be necessary to determine the optimal immunosuppressive regimen.

Conversion to sirolimus for chronic allograft dysfunction: long-term results confirm predictive value of proteinuria

The aim was to evaluate long-term graft survival and function after conversion to sirolimus (SRL) for chronic calcineurin inhibitor (CNI) toxicity and the predictive value of baseline proteinuria. This is a follow-up conversion study of 59 renal transplant patients with deteriorating graft function and histologic signs of CNI toxicity. Previously, baseline proteinuria <800 mg/day was identified as a short-term predictor for successful conversion. Follow-up was 5.3 +/- 0.8 (3.7-6.8) years. Patient survival was 88%, graft survival 38%. Creatinine clearance at the last follow-up was 33.7 +/- 14 ml/min, proteinuria 826 +/- 860mg/day. Baseline proteinuria <800 mg/day was associated with better graft survival. In a cox analysis including proteinuria >800 mg, glomerular filtration rate, age at conversion, chronic Banff score at conversion and time after transplantation at conversion, higher proteinuria was associated with a relative risk of graft loss of 3.98. Prognosis of chronic allograft dysfunction is poor. However, conversion to SRL remains an option for patients with low baseline proteinuria, which can slow down deterioration of graft function during a follow-up period of up to 5 years.

Trends in kidney transplantation in Australia and New Zealand, 1993-2004

BACKGROUND

We hypothesize that transplant outcome in Australia and New Zealand has improved despite more unfavorable transplant characteristics. Data from the Australia and New Zealand Dialysis and Transplant registry was used to examine this hypothesis.

METHODS

All adult kidney-only transplants from January 1993 to December 2004 in Australia or New Zealand were followed-up until death or December 2005. Outcomes were adjusted for covariates in multivariate models, with transplant year modeled as a continuous variable.

RESULTS

Altogether 6764 patients were included. There were proportionately more live donor and primary transplants, older donors and recipients, and higher recipient body mass index, waiting time, and human leukocyte antigen mismatch in recent cohorts. Death-censored graft loss decreased (adjusted hazard ratio: 0.92 [0.90-0.95] per year, P<0.001). This trend was seen at both 0-1 and 1-5 years posttransplant, and was mainly for immune-mediated graft losses. Patient survival improved only in New Zealand, and only for the first posttransplant year (adjusted odds ratio: 0.88 [0.82-0.95] per year, P=0.001). Cardiovascular deaths decreased while infection or cancer deaths were unchanged. Adjusted delayed graft function rates were unchanged. The acute rejection incidence at 6 months decreased (adjusted odds ratio: 0.88 [0.85-0.90] per year, P<0.001). One and 3-year graft function significantly improved, even after adjusting for rejection. All outcomes did not vary by expanded donor criteria status.

CONCLUSIONS

Graft survival and function have improved in recent years, but long-term patient survival remains unchanged. With longer follow-up, the improvement in rejection rates and graft function may lead to further improvements in long-term graft survival and potentially better patient survival.

Renal cortex neuronal nitric oxide synthase in response to rapamycin in kidney transplantation

Decreased renal neuronal nitric oxide synthase (nNOS) is present in various chronic kidney diseases although there is relative little known in chronic allograft nephropathy (CAN). Female sex increases the risk of acute rejection and calcineurin-inhibitor toxicity but decreases the risk of CAN. Rapamycin (RAPA) is an alternative immunosuppress although there is no information whether it is effective in females. We therefore investigated the efficacy of RAPA in both sexes and the impact of RAPA on renal cortex structure and nNOS expression. Male (M) and female (F) F344 kidneys were transplanted into same sex Lewis (ALLO) or F344 (ISO) recipients and treated with 1.6 mg/kg/day of RAPA for 10 days. Grafts were removed for renal histology and endothelial (e)NOS and neuronal (n)NOS protein measurements at 22 weeks. All ALLO rats survived without acute rejection. ALLO F survived with mild proteinuria and CAN at 22 weeks similar to ALLO M, while ISO F had better outcome than ISO M. Cortical nNOSalpha was undetectable in all RAPA groups; however, nNOSbeta transcript and protein were compensatory increased. Both ALLO and ISO F showed higher medullary nNOSalpha but lower cortical eNOS abundance than M groups. In male ALLO RAPA decreased renal cortical nNOSalpha but increased nNOSbeta expression. This may represent compensatory upregulation of nNOSbeta when nNOSalpha-derived NO is deficient.

Specific alloantigen self-control by regulatory T cells in organ transplantation: a review

Multidrug immunosuppressive protocols have increased short-term patient and graft survival rates from 50% to 90% in the past two decades. Unfortunately, chronic graft rejection still remains the main cause of long-term failure and patients must undergo lifelong immunosuppression. The severe side effects such as life-threatening infections, secondary malignancies, and cardiovascular dysfunction all together include roughly 50% of deaths among kidney transplant patients with functioning grafts. Therefore, it should be of crucial importance to reduce immunosuppression and seek induction of specific tolerance to donor alloantigens. Several investigations have suggested that the acquisition of tolerance to self and/or foreign antigens is dependent on the number and function of naturally occurring and acquired regulatory T cells, which can control all aggressive T cells. The regulatory T cells together with their receptors, costimulatory molecules, cytokines, chemokines, and growth factors all contribute to maintain an equilibrium between aggressive and suppressive effector immune responses. As a consequence of increased knowledge, new immunosuppressive approaches based on either alloantigen-specific regulatory T-cell expansion in vivo or in vitro have been proposed to achieve donor-specific transplantation tolerance in kidney allograft recipients. This contribution attempted to summarize knowledge about regulatory T cells and developing methods to induce specific tolerance in kidney transplantation.

To Biopsy or Not to Biopsy? Should We Screen the Histology of Stable Renal Grafts?

Chronic allograft dysfunction is currently the main cause of late allograft failure. Recent encouraging evidence suggests that it may be possible to delay the development of graft damages if adequate management is initiated early in the course of the disease. These observations have renewed interest in the performance of protocol biopsies as routine follow-up procedure for the screening of renal transplants. In the present review, we summarize the available data from the literature to determine the pros and cons of protocol renal allograft biopsies. On the basis of this evidence, we discuss the ethical concerns raised by this procedure.

Immunosuppressive strategies to improve outcomes of kidney transplantation

The introduction of several immunosuppressive agents over the past decade has reduced the rate of acute rejection significantly and has improved short-term renal allograft survival. However, their impact on long-term outcomes remains unclear. Current immunosuppressive strategies are focused on improving long-term graft and patient survival along with maintaining allograft function. The approval of the new immunosuppressive agents: rabbit antithymocyte globulin, basiliximab, daclizumab, tacrolimus, mycophenolate, and sirolimus, also has facilitated the development of steroid- and calcineurin inhibitor-sparing regimens in kidney transplantation. We discuss the impact of various immunosuppressive regimens on the outcome measures of kidney transplantation: acute rejection episodes, allograft survival, and renal function.

Renal transplant rejection markers

Acute rejection is one of the key factors which determine long-term graft function and survival in renal transplant patients. Timely detection and treatment of rejection is therefore, an important goal in the post-transplant surveillance. The standard care with serum creatinine measurements and biopsy upon allograft dysfunction implies that acute rejection is detected in an advanced stage. Therefore, non-invasive monitoring for acute rejection by markers in blood and urine has been tried over the past decades. This review describes the requirements that should be met by non-invasive markers. The experience with single biomarkers and with newer approaches--mRNA expression analysis, metabolomics, and proteomics--will be discussed, including future directions of necessary research.

Determinants of coronary artery calcification progression in renal transplant recipients

Coronary artery calcification (CAC) is associated with increased atherosclerotic burden and cardiovascular events. The objective of this study was to determine the natural history and risk factors associated with CAC progression in a cohort of incident asymptomatic renal transplant recipients with no history of coronary revascularization. Electron-beam computed tomography was performed in 82 subjects at time of transplantation and at least 1 year later. Mean (SD) and median CAC score increased for all subjects from 392.4 (747.9) and 75.8 at time of transplant to 475.3 (873.5), (p = 0.002[log]) and 98.9 (p < 0.001), respectively. Most subjects (89%) with no calcifications remained without calcification. Mean annualized rate (SD) of CAC score change was 52.5 (150) with a median of 0.5. Average yearly percent change was 67.3 (409.6) with a median of 1.4. In multivariate analysis, diastolic blood pressure at 3 months post-transplant, Caucasian race, glomerular filtration rate at 3.0, months post-transplant, body mass index and baseline CAC score were independent predictors of annualized rate of CAC change. There is significant progression of CAC post-renal transplantation in most subjects. Progression is most likely to occur in white patients and is associated with clinical factors such as blood pressure, body mass index, renal function and baseline CAC score.

Tacrolimus exposure and evolution of renal allograft histology in the first year after transplantation

Tacrolimus has a narrow therapeutic window and is characterized by a large inter-individual variability in bioavailability. The impact of tacrolimus exposure on subclinical evolution of graft histology has not been studied in renal recipients. This analysis included 239 protocol biopsies (obtained at implantation, 3 and 12 months) of 120 consecutive kidney recipients treated with tacrolimus, mycophenolate mofetil (MMF) and corticosteroids. Biopsies were scored according to the Banff 2001 criteria and a chronicity score was calculated. Prospective pharmacokinetic data were included in the analysis (5544 tacrolimus predose blood concentrations and tacrolimus AUC(0-12) at 3 and 12 months). Higher donor age and higher number of human leukocyte antigen-DR (HLA-DR) mismatches were independent predictors of subclinical acute rejection at 3 months, present in 8.7% of patients. The number of HLA-DR mismatches was independently associated with biopsy-proven clinical acute rejection. Biopsy-proven acute rejection episodes and low mean tacrolimus exposure were independently associated with higher increase in chronicity scores between 3 and 12 months after transplantation. This observational study suggests that rejection phenomena and immune-mediated mechanisms remain important in the early progression of chronic allograft pathology. Tacrolimus doses or systemic exposure were not associated with lesions of calcineurin inhibitor nephrotoxicity, suggesting that other factors determine susceptibility to tacrolimus nephrotoxicity.

Calcineurin inhibitor-free immunosuppression in kidney transplantation

The introduction of calcineurin inhibitors (CNI) revolutionized kidney transplantation (KTx). Exceptionally low acute rejection rates and excellent graft survival could be achieved with CNI-based (cyclosporine and tacrolimus) immunosuppressive protocols. However, despite short-term success, long-term graft attrition continues to be a significant problem, thus leaving clinicians looking for possible interventions. CNI nephrotoxicity is but one of numerous factors that may be contributing to long-term damage in transplant kidneys. Therefore, newer immunosuppressive agents such as mycophenolate mofetil and sirolimus (Rapa) have raised the possibility of withdrawing or avoiding CNIs altogether. Protocols exploring these options have gained greater attention over the last few years. Herein, we review studies addressing either CNI withdrawal or CNI avoidance strategies as well as discuss the risks versus benefits of these protocols. Given the accumulated experience to date, in our opinion, the use of CNIs as a part of immunosuppressive regimens remains the proven standard of care for renal transplant patients. The long-term safety and efficacy of CNI withdrawal and avoidance strategies need to be further validated in controlled clinical trials.

Acute rejection in non-compliant renal allograft recipients: a distinct morphology

Non-compliance for immunosuppressive medication is frequent in renal transplant recipients, and associated with late acute rejection and graft loss. Although numerous studies were published on risk factors and outcome, no data are available on the histopathology of the 'non-compliant' allograft. As non-compliant patients swing between subtherapeutic and toxic doses of immunosuppression, trough levels show large variation. We questioned whether the histology of acute rejection in non-compliers (i) differs from the 'classical' acute rejection; (ii) shows more concomitant calcineurin-inhibitor toxicity; (iii) is associated with C4d and plasma cell (PC)-rich infiltrates. Based on validated interview methods/self reporting, 145 adult renal allograft recipients, transplanted for greater than one yr, on cyclosporine A and corticosteroids, were categorized as either compliant or non-compliant. Non-compliance was defined in 32 patients (22.1%). All late (greater than one yr) allograft biopsies were reviewed (Banff) and immuno-stained for C4d. Computerized morphometry was performed on late biopsies with features of acute cellular rejection. Sixty-two patients had > or =1 late biopsy [41 (36.2%) compliant/21 (65.6%) non-compliant; p = 0.0043], comprising a pool of 90 biopsies (61 compliant/29 non-compliant; p = 0.0303). 'Non-compliant' biopsies had higher scores of C4d (p = 0.0092), acute tubular damage (p = 0.0058), and peritubular capillaritis (p = 0.0070). 'Non-compliant' biopsies with acute cellular rejection showed less interstitial edema (p = 0.0165), more interstitial infiltrate (p = 0.0100), more interstitial fibrosis (p = 0.0277), and more tubular atrophy (p = 0.0197). PC-rich infiltrates correlated with C4d (p = 0.0080). Detection of non-compliance is mandatory as it represents an important cause of graft loss. This study describes histologic features of renal allograft biopsies in non-compliant patients that could help identifying this patient profile.

Can mTOR inhibitors reduce the risk of late kidney allograft failure?

The most frequent causes of late kidney allograft failure are chronic rejection, nonalloimmune injury and death, all of which may depend on the characteristics of the donor and recipient, but may also be influenced by the type of immunosuppression. Combining calcineurin inhibitors (CNIs) and corticosteroids offers potent immunosuppression, but may also cause side effects leading to progressive graft dysfunction or an increased risk of death. New immunosuppressive strategies may come from the availability of inhibitors of mTOR, a downstream effector of phosphatidylinositol-3 kinase that provides the signal for cell proliferation by phosphorylating a cascade of kinases. Recent trials have shown that it is possible to minimize the dose or withdraw CNIs a few weeks after transplantation when they are combined with mTOR inhibitors and their combination may also make it possible to minimize or avoid the use of corticosteroids. Moreover, by inhibiting the signal for cell proliferation, mTOR inhibitors may reduce the replication of cytomegalovirus inside host cells, prevent transplant vasculopathy, and exert anti-oncogenic activity. All of these characteristics offer a ray of hope for reducing the risk of long-term allograft failure.

Chronic Allograft Nephropathy

Chronic allograft nephropathy (CAN) remains the Achilles heel of renal transplantation. In spite of the significant strides achieved in one-year renal allograft survival with newer immunosuppressant strategies, the fate of long-term renal allograft survival remains unchanged. The number of renal transplant recipients returning to dialysis has doubled in the past decade. This is especially important since these patients pose a significantly increased likelihood of dying while on the waiting list for retransplantation, due to increasing disparity between donor organ availability versus demand and longer waiting time secondary to heightened immunologic sensitization from their prior transplants. In this review we analyze the latest literature in detail and discuss the definition, natural history, pathophysiology, alloantigen dependent and independent factors that play a crucial role in CAN and the potential newer therapeutic targets on the horizon. This article highlights the importance of early identification and careful management of all the potential contributing factors with particular emphasis on prevention rather than cure of CAN as the core management strategy.

The role of angiotensin II type 1 receptor-activating antibodies in renal allograft vascular rejection

Acute rejection with vascular involvement remains a challenging problem in renal allotransplantation. Fibrinoid necrosis of the arteries with secondary thrombotic occlusions is C4d negative in 50% of cases and has the worst prognosis among all allograft vascular lesions. Nonhuman leukocyte antigen (HLA) non-complement-fixing antibodies reacting to artery-specific antigens have been speculated to be responsible for causing severe vascular injury. We recently reported the presence of agonistic antibodies against the angiotensin II type 1 receptor (AT(1)R-AA) in 16 recipients of renal allografts who had severe vascular rejection and malignant hypertension but who did not have anti-HLA antibodies. AT(1)R-AA stimulate AT(1)R and induce mediators of inflammation and thrombosis. Removal of AT(1)R-AA by plasmapheresis in combination with pharmacologic AT(1)R blockade leads to improved renal function and graft survival in AT(1)R-AA-positive patients. We have shown that the analysis of the subtle diagnostic and mechanistic differences may help to identify patients at particular risk and improve outcome of rejections with vascular pathology.

Clinical transplantation tolerance: many rivers to cross

Modern immunosuppressive regimens for organ transplantation have resulted in excellent short-term results but less dramatic improvements in long-term outcomes. Moreover, they are associated with significant deleterious effects. One solution that should avoid the adverse drug effects and result in improved graft and patient longevity as well as positively impacting on the organ shortage is the establishment of transplantation tolerance. Ever since the original description of transplantation tolerance in rodent allografts, there have been significant efforts made to translate tolerance-promoting strategies to the clinical arena. However, >50 years later, we are still faced with significant barriers that are preventing such a goal from being widely attained. Nonetheless, pilot clinical tolerance protocols are underway in selected transplant recipients. In this review, we discuss the scientific and nonscientific issues that must be overcome for successful transplantation tolerance to become a clinical reality.

A role for HO-1 in renal function impairment in animals subjected to ischemic and reperfusion injury and treated with immunosuppressive drugs

INTRODUCTION

Ischemia/reperfusion injury (IRI) represents the single major antigen-independent factor implicated in pathogenesis of chronic graft dysfunction. Tacrolimus is a calcineurin inhibitor, which has been suggested to be helpful in cyclosporine-related chronic toxicity. Rapamycin has antiproliferative properties that may impair renal regeneration after IRI. Therefore, immunosuppressive drugs might impair renal graft outcome in those organs suffering IRI.

MATERIAL AND METHODS

C57B1/6 male mice subjected to 45 minutes of renal pedicle ligation were reperfused for 24 hours. Mice were treated with rapamycin, cyclosporine, or tacrolimus. Blood and renal tissue samples were collected at 24 hours after IRI. Urea levels were measured. Heme Oxygenase 1 (HO-1) gene transcript was amplified by a real-time polymerase chain reaction technique.

RESULTS

Animals treated with cyclosporine and subjected to IRI showed impaired renal function that peaked at 24 hours. Additional pretreatment with rapamycin produced even more impairment of renal function, when compared with controls. However, tacrolimus pretreatment was associated with a better renal outcome. HO-1 expression was upregulated after IRI by 2.6 arbitrary units at 24 hours. Rapamycin showed worse impairment of renal function.

CONCLUSION

Tacrolimus was not associated with worsening renal function when compared with animals just subjected to IRI. Upregulation of HO-1 may be an attractive approach to limit graft injury.

Rapamycin enhances the number of alloantigen-induced human CD103+CD8+ regulatory T cells in vitro

BACKGROUND

Regulatory T cells (T(reg) cells) may be operational in both the induction and maintenance of transplantation tolerance. We recently showed that alloantigen-induced CD103+ CD8+ T cells strongly suppressed T-cell proliferation in mixed lymphocyte culture (MLC) via a contact-dependent mechanism. CD103 directs T lymphocytes to their ligand E-cadherin, which is expressed on renal tubular epithelial cells, and CD103+ CD8+ T cells have been described to be present in late renal allograft rejection.

METHODS

We studied the influence of prednisolone, cyclosporin, tacrolimus, CD25 monoclonal antibodies, rapamycin, and mycophenolate mofetil (MMF) on the development and functional activity of alloantigen-activated CD103+ CD8+ T cells in MLC.

RESULTS

Calcineurin inhibitors, MMF, and CD25mAb did not influence the number of CD103 expressing CD8+ T cells. In contrast, corticosteroids diminished CD103 expression on alloactivated CD8+ T cells, which appeared to be caused by their inhibitory action on myeloid dendritic cells. Addition of rapamycin to allocultures led to an increased percentage of CD103+ CD8+ alloreactive T cells. Moreover, in the presence of rapamycin, these cells tended to show higher suppressive capacity.

CONCLUSIONS

Alloreactive CD103+ CD8+ T(reg) cells may expand and exert their suppressive function during immunosuppressive treatment with rapamycin. These data are relevant in the design of immunosuppressive drug regimens intended to induce and/or maintain transplantation tolerance.

Patient characteristics influencing ciclosporin pharmacokinetics and accurate Bayesian estimation of ciclosporin exposure in heart, lung and kidney transplant patients

BACKGROUND AND OBJECTIVES

Population pharmacokinetic studies of ciclosporin microemulsion are needed to identify the individual factors influencing ciclosporin pharmacokinetic variability in transplant patients and to design efficient tools for the accurate estimation of ciclosporin overall exposure (area under the plasma concentration-time curve from 0 to 12 hours [AUC12]). In the present retrospective study, a large database of heart, lung (with or without cystic fibrosis) and kidney (both adult and paediatric) transplant patients receiving ciclosporin microemulsion was analysed with the aims of (i) building a population pharmacokinetic model and finding the main covariates linked with ciclosporin microemulsion pharmacokinetic parameters; and (ii) developing a maximum a posteriori probability Bayesian estimator (MAP-BE) to estimate ciclosporin microemulsion pharmacokinetic parameters using a limited-sampling strategy.

METHODS

3,072 concentration data from 147 patients (i.e. 309 full pharmacokinetic profiles) were analysed using the nonlinear mixed-effects model program NONMEM. The influence of numerous covariates was tested, and the final model was validated by data splitting. For Bayesian estimation, the best limited-sampling strategy was determined based on the D-optimality criterion, and validation performed in an independent group of 60 patients.

RESULTS

The pharmacokinetics of ciclosporin microemulsion were accurately described by a two-compartment model with Erlang distribution for the absorption process. The type of graft and post-transplantation period were identified as significant sources of variability of the absorption parameter. Both apparent volume of the central compartment after oral administration (V1/F) and apparent oral clearance (CL/F) increased with bodyweight. The best limited-sampling strategy for Bayesian estimation was 0 hour, 1 hour and 3 hour post-dose, providing accurate estimation of ciclosporin microemulsion AUC12 in all patients of the test group, with a mean bias of 2.0 +/- 10.5% (range: -19.1% to -21.4% and 95% CI -0.6, +4.7).

CONCLUSION

Population pharmacokinetic analysis of ciclosporin microemulsion in allograft transplants resulted in the design of a new pharmacokinetic model for ciclosporin microemulsion, identification of significant covariates and the design of an accurate MAP-BE based on three blood concentrations and these covariates.

Five-Year Outcome in Pediatric Patients With Mycophenolate Mofetil-Based Renal Transplantation

BACKGROUND

Mycophenolate mofetil (MMF) based immunosuppression after renal transplantation has proven to be safe and beneficial for children and adolescents. However, long-term analysis, in particular of pediatric patients, is scarce.

PATIENTS

Data of 140 patients receiving MMF versus azathioprine (AZA) in combination with cyclosporine A (CsA) and prednisone without induction were analyzed with a main focus on survival and renal function in long-term follow-up.

RESULTS

After 5 years of follow-up, 44 MMF and 20 AZA patients were still on study. Graft survival of intent to treat (ITT) groups was 90.7% for MMF and 68.5% for AZA patients (P<0.001). Cumulative rejection free survival was 51.2% in MMF versus 37.0% in AZA patients (P<0.05). In association with early acute rejections (ARE), projected half-life was 14.4/4.5 years in patients with and 18.7/14.5 years without rejection in the MMF/AZA group, respectively.

CONCLUSIONS

MMF based protocols improved long-term graft survival without an increase in side effects. Early ARE were associated with worse half-life of the graft, although more stressed in the AZA group. Thus, to improve quality of life in children for very long-term outcome, ARE should be further decreased and renal function should be better preserved.

Why hasn't eliminating acute rejection improved graft survival?

Although patients with end-stage renal disease can be maintained with dialysis therapy, the superiority of patient survival with renal transplantation makes transplantation the preferred method of renal replacement. Potent immunosuppressive therapies, particularly calcineurin inhibitors, have greatly reduced the incidence of acute rejection. However, long-term allograft survival remains limited. We discuss the impact of acute rejection on long-term allograft survival and discuss other factors leading to late allograft loss, including calcineurin inhibitor toxicity, chronic allograft nephropathy, and BK virus nephropathy, as well as donor and recipient factors associated with long-term allograft loss.

Establishing the molecular pathways involved in chronic allograft nephropathy for testing new noninvasive diagnostic markers

BACKGROUND

Chronic allograft nephropathy (CAN) is a cause of graft loss. The multistage processes that result in CAN are poorly understood. Noninvasive assays for detecting allograft dysfunction and predicting long-term outcomes are a priority in transplantation (Tx).

METHODS

Renal tissue from kidney transplant patients (KTP) with CAN (n=11) and normal kidneys (NK; n=7) were studied using microarrays. Markers resulting from the microarray analysis (transforming growth factor [TGF]-beta, epidermal growth factor receptor [EGFR], angiotensinogen [AGT]) were tested in urine (Ur) and peripheral blood (PB) samples from the CAN patients (collected at the biopsy time) using reverse-transcriptase real-time polymerase chain reaction. Ur and PB samples from long-term KTP with stable renal function (SRF; n=20) were used as control.

RESULTS

Assuming unequal variances between CAN and NK, using a false discovery rate of 0.005, and running 1,000 of all possible permutations, 728 probe sets were differentially expressed. Genes related to fibrosis and extracellular matrix deposition (i.e., TGF-beta, laminin, gamma 2, metalloproteinases-9, and collagen type IX alpha 3) were up-regulated. Genes related to immunoglobulins, B cells, T-cell receptor, nuclear factor of activated T cells, and cytokine and chemokines receptors were also upregulated. EGFR and growth factor receptor activity (FGFR)2 were downregulated in CAN samples. AGT, EGFR, and TGF-beta levels were statistical different in urine but not in blood samples of CAN patients when compared to KTP with SRF (P<0.001, P=0.04, and P<0.001, respectively).

CONCLUSIONS

Genes related to fibrosis, extracellular matrix deposition, and immune response were found up-regulated in CAN. Markers resulting from the microarray analysis were differentially expressed in Ur samples of the CAN patients and in concordance with the microarray profiles.

Improved outcomes of renal transplantation from cardiac death donors: a 30-year single center experience

Outcomes of renal transplantation from donation after cardiac death (DCD) donors over 30 years were analyzed. Between 1975 and 2004, 256 renal transplantations from DCD donors were performed. The recipients were divided into four groups according to a time period as follows: 1975-1979 (Group 1; n = 18), 1980-1989 (Group 2; n = 81), 1990-1999 (Group 3; n = 84) and 2000-2004 (Group 4; n = 73). Of the 256 transplanted kidneys from DCD donors, 38 (15%) functioned immediately after transplantation. The incidence of delayed graft function (DGF) was 72%. Warm ischemic time and total ischemic time were 7.4 +/- 9.4 min and 11.9 +/- 5.6 h, respectively. The overall graft survival rates at 1, 5 and 10 years were 80%, 72% and 53%, respectively. Graft survival rates in each group have continually improved over time (5-year graft survival; 23% vs. 64% vs. 74% vs. 91%, respectively). However, there was no significant difference in graft survival rates between the groups of patients who survived with a functioning graft for more than 1 year. A multivariate Cox regression analysis showed acute rejection and donor age to be independently associated with graft outcome. DCD donors are a valuable source of kidneys for transplantation with promising long-term outcomes.

The burden of new-onset diabetes mellitus after transplantation

The clinical impact of new-onset diabetes mellitus (NODM) is frequently underestimated by clinicians. NODM occurs in approximately 15-20% of renal transplant patients and 15% of liver transplant recipients. Diabetes after transplantation is a leading risk factor for cardiovascular events, with a higher prognostic value than in the non-transplant population. NODM also appears to have a negative influence on graft function, and graft survival rates after renal transplantation are significantly lower in patients who develop diabetes than in controls. Patient mortality following renal transplantation is generally found to be higher in patients with NODM, due to increased cardiovascular and peripheral vascular disease, accelerated graft deterioration and diabetes-related complications, notably infection. A renal registry analysis has reported an increase of 87% in risk of death following onset of NODM. There is also limited evidence that NODM is associated with increased risk of death in liver transplant patients. The relative incidence and severity of diabetic complications in transplant recipients have not been assessed rigorously in a clinical trial but registry data indicate that 20% of renal transplant patients with NODM experience at least one clinically significant diabetic complication within three years. Financially, the additional healthcare costs incurred over the first two years following onset of NODM amount to 21,500 dollars. Routine pre-transplant assessment of diabetic risk, with requisite modification of lifestyle, glycaemic monitoring and immunosuppressive regimens, and coupled with standardized, aggressive hypoglycaemic management as necessary, offers an important opportunity to alleviate the burden of NODM for transplant patients.

Prevalence and risk factors of non-adherence with immunosuppressive medication in kidney transplant patients

Non-adherence with immunosuppressive regimen is a major risk factor for poor outcome after kidney transplantation. Identifying patients at risk for non-adherence requires understanding the risk factors for non-adherence. This prospective study included a convenience sample of 249 adult kidney transplant patients >1 year post-transplant. Non-adherence was monitored electronically using MEMS(R). Selected socio-economic, therapy-, patient-, condition- and healthcare team-related risk factors for non-adherence were assessed. Period prevalences were expressed as the percent of prescribed doses taken (taking adherence), the percent of correctly dosed days (dosing adherence), the percentage of inter-dose intervals not exceeding 25% of the prescribed interval (timing adherence), and the number of drug holidays per 100 days (no intake for > 48 h if once daily or for > 24 h if twice daily intake). Testing occurred by simple mixed logistic regression analysis. Factors significant after correction for multiple testing were entered into a multiple logistic regression model. Mean taking, dosing, timing adherence, and drug holidays were 98%, 96%, 93%, and 1.1 days, respectively. Non-adherence was associated with lower self-efficacy, higher self-reported non-adherence, no pillbox usage, and male gender. Adherence declined between Monday and Sunday. This study provides a framework for identifying patients at risk for non-adherence and for developing adherence-enhancing interventions.

Renal Transplantation in High-Risk Patients

Renal transplantation in high-risk patients is a growing phenomenon. More patients are progressing to endstage renal failure, in the setting of an increased incidence of diabetes mellitus and cardiovascular disease. Current organ shortages and the use of more marginal donors have affected both patient and graft survival. Acute rejection has been minimised under modern immunosuppression; however, patient and long-term allograft outcomes have not improved concurrently. Specific understanding of donor, recipient and allograft variables associated with stratification of patients as 'high risk for renal transplantation' is necessary to facilitate appropriate peri- and post-transplant pharmacotherapy. Induction and maintenance immunosuppression choices are different for high-risk patients and must be made to ensure optimal immunosuppression, while limiting patient and allograft toxicity.

The Association Between Angiotensin Converting Enzyme Inhibitor or Angiotensin Receptor Blocker Use During Postischemic Acute Transplant Failure and Renal Allograft Survival

BACKGROUND

Postischemic acute renal transplant failure occurs in approximately one fourth of all dead donor transplantations. Uncertainty exists regarding the putative association between the use of angiotensin converting enzyme inhibitors (ACEIs) or angiotensin II AT1 receptor blockers (ARBs) and kidney transplant graft survival in patients with delayed allograft function.

METHODS

We conducted an open cohort study of all 436 patients who experienced an acute renal transplant failure out of all 2,031 subjects who received their first kidney transplant at the Medical University of Vienna between 1990 and 2003. Actual and functional graft survival was compared between users and nonusers of ACEI/ARB using exposure propensity score models and time-dependent Cox regression models.

RESULTS

Ten-year actual graft survival averaged 44% in the ACEI/ARB group, but only 32% in patients without ACEI/ARB (P=0.002). The hazard ratio of actual graft failure was 0.58 (95% confidence interval: 0.35-0.80, P=0.002) for ACEI/ARB users compared with nonconsumers. Seventy-one percent of subjects with ACEI/ARB had a functional graft at 10 years versus 64% of ACEI/ARB nonusers (P=0.027). The hazard ratio of functional graft loss was 0.48 (95% confidence interval: 0.24-0.91, P=0.025).

CONCLUSIONS

Use of ACEI/ARB in patients experiencing delayed allograft function was associated with longer actual and functional transplant survival.

Drug Insight: maintenance immunosuppression in kidney transplant recipients

Kidney transplantation is the treatment of choice for patients with end-stage renal disease, in part because of ongoing efforts towards improving immunosuppressive strategies. Although calcineurin inhibitors remain the mainstay of immunosuppression in kidney transplant recipients, within this class of drug there has been a shift from use of ciclosporin to use of tacrolimus. Mycophenolate mofetil and mycophenolate sodium are now the antimetabolites of choice. A new class of drugs (inhibitors of mammalian target of rapamycin) that includes sirolimus is being increasingly used in stable kidney transplant recipients. New data, however, indicate that a more cautious approach to the use of this drug is warranted. Many transplant centers are now using steroid avoidance, minimization and withdrawal protocols. The impact of these different drugs and therapeutic strategies on outcomes has to be weighed against their immunosuppressive benefit. As more and more community-based nephrologists and primary care physicians are becoming involved in the care of stable kidney transplant recipients, it is important for these clinicians to familiarize themselves with novel immunosuppressive drugs and their pharmacokinetic properties.

Developing a tool for noninvasive monitoring of renal allografts

Renal transplantation has emerged as the therapy of choice for many patients with end-stage renal disease. One of the major goals is to tailor immunosuppressive therapy to the individual needs of every patient at every time point post transplant, balancing the risk for rejection and over-immunosuppression. Such individualized treatment will require assays that can detect harmful processes in the allograft early and that can be measured repeatedly. In this review, advantages and disadvantages of current assays to monitor renal allografts noninvasively and how proteomic technology might contribute to the development of novel biomarkers to improve patient management will be discussed.

BOLD-MRI assessment of intrarenal oxygenation and oxidative stress in patients with chronic kidney allograft dysfunction

Blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) uses deoxyhemoglobin as an endogenous contrast agent for the noninvasive assessment of tissue oxygen bioavailability. We hypothesized that intrarenal oxygenation was impaired in patients with chronic allograft nephropathy (CAN). Ten kidney-transplant recipients with CAN and nine healthy volunteers underwent BOLD-MRI. Medullary R2* (MR2*) and cortical R2* (CR2*) levels (measures directly proportional to tissue deoxyhemoglobin levels) were determined alongside urine and serum markers of oxidative stress (OS): hydrogen peroxide (H(2)O(2)), F(2)-isoprostanes, total nitric oxide (NO), heat shock protein 27 (HSP27), and total antioxidant property (TAOP). Mean MR2* and CR2* levels were significantly decreased in CAN (increased local oxyhemoglobin concentration) compared with healthy volunteers (20.7 +/- 1.6 vs. 23.1 +/- 1.8/s, P = 0.03 and 15.9 +/- 1.9 vs. 13.6 +/- 2.3/s, P = 0.05, respectively). There was a significant increase in serum and urine levels of H(2)O(2) and serum HSP27 levels in patients with CAN. Conversely, urine NO levels and TAOP were significantly increased in healthy volunteers. Multiple linear regression analyses showed a significant association between MR2* and CR2* levels and serum/urine biomarkers of OS. BOLD-MRI demonstrated significant changes in medullary and cortical oxygen bioavailability in allografts with CAN. These correlated with serum/urine biomarkers of OS, suggesting an association between intrarenal oxygenation and OS.

Costimulation blockade and its possible future use in clinical transplantation

The nonimmune effects of currently used immunosuppressive drugs result in a high incidence of late graft loss due to nephrotoxicity and death of patients. As an immune-specific alternative to conventional immunosuppressants, new biotechnology tools can be used to block the costimulation signals of T-cell activation. Many experimental studies--particularly preclinical studies in nonhuman primates--have focused on blocking the 'classical' B7/CD28 and CD40/CD40L pathways, which are critical in primary T-cell activation. Here, we review the limitations, the recent advances and the first large-scale clinical application of the CTLA4-Ig fusion protein to block the B7/CD28 costimulation pathway. We also focus on new B7/CD28 and tumor necrosis factor (TNF)/TNF-R family costimulatory molecules that can deliver positive or negative costimulation signals regulating the alloimmune response. Strategies that use single agents to block costimulation have often proved to be insufficient. Given the diversity of the different costimulation molecules, future strategies for human transplantation may involve the simultaneous blockade of several selected pathways or the simultaneous use of conventional immunosuppressants.

Basic Transplantation Immunology

Humans are protected from a daily onslaught of pathogenic organisms by an immune system that provides multiple layers of protection. Until solid organ transplantation became technically feasible in the early twentieth century, this constant state of surveillance for foreign cells that are associated with the immune response mostly was viewed as advantageous. Unfortunately for patients who have end-stage failure of heart, lungs, kidney, liver, and pancreas, the immune system is incapable of distinguishing between the presence of beneficial foreign tissue and harmful foreign pathogens; it mounts an effective attack against both. Improving our understanding of the factors that initiate and perpetuate the alloimmune response will result in the development of more refined and better tolerated immunosuppressive strategies.

Renal transplantation: older recipients and donors

The majority of patients receiving a renal allograft, including a kidney from an older donor, do well. Renal transplantation from a living donor is associated with distinct advantages, including prolonged allograft survival. When live donors are not available, however, deceased donor kidneys provide suitable renal function that frequently lasts the lifetime of elderly recipients. Elderly patients who receive a kidney transplant enjoy improved survival, better quality of life, and lower medical costs than those who remain on dialysis.

Maintenance immunosuppression regimens: conversion, minimization, withdrawal, and avoidance

A wide choice of drug combinations is available to clinicians for immunosuppression regimens for their kidney transplant patients. Although many protocols have minimized early graft loss, the optimal long-term regimen is unknown. Recent studies clearly showed that cardiovascular death is now the leading cause of graft loss. Strategies must be developed that address this risk while keeping immunologic events low. Transplant physicians have focused on exploring regimens that minimize or avoid the use of corticosteroids. Studies also have started to explore protocols that minimize calcineurin inhibitor therapy.

Relative risk of new-onset diabetes during the first year after renal transplantation in patients receiving tacrolimus or cyclosporine immunosuppression

Clinical trials have consistently shown a higher incidence of new-onset diabetes mellitus with tacrolimus than cyclosporine. However, in protocol-driven studies steroid doses are comparable in both treatment arms, while in clinical practice steroid dose used in conjunction with tacrolimus or cyclosporine may differ. This retrospective study analysed renal transplant recipients without pre-existing diabetes receiving tacrolimus (n = 100) or cyclosporine (n = 100) for whom one-year follow-up data were available. Diabetes was defined as use of insulin or oral hypoglycemic agents; fasting glucose >6.9 mmol/L; or non-fasting glucose >11 mmol/L on three consecutive occasions. Tacrolimus-treated patients were significantly older than cyclosporine-treated patients (49 +/- 14 vs. 44 +/- 13 yr, p < 0.05) and received a significantly lower cumulative dose of corticosteroids over the first three months post-transplant (1284 +/- 379 vs. 1714 +/- 486 mg, p < 0.0001). At 3, 6, 9 and 12 months significantly more tacrolimus-treated patients had new-onset diabetes than cyclosporine- treated patients. At 12 months, 18 patients receiving tacrolimus and two receiving cyclosporine had diabetes (p < 0.0001). There was a clear relationship between age and incidence of new-onset diabetes at three months in the tacrolimus cohort. After stratifying patients by age group, the frequency of diabetes was significantly higher with tacrolimus than with cyclosporine in patients aged 40-60 yr [8/46 (17.4%) vs. 2/48 (4.2%), p < 0.05] and >60 yr [9/28 (32.1%) vs. 0/14 (0%), p < 0.05]. The mean tacrolimus trough level during the first three months was similar in patients with diabetes (13.1 +/- 2.3 ng/mL) or without diabetes (13.0 +/- 2.8 ng/mL, n.s.). These results indicate that new-onset diabetes is strongly and significantly associated with tacrolimus vs. cyclosporine in renal transplant recipients, even when steroid dosing is lower with tacrolimus.

How can we measure immunologic tolerance in humans?

Prevention and treatment of allograft rejection in organ transplant recipients relies primarily on non-antigen-specific immunosuppression, with all its associated potential hazards and costs. Currently, the status of the recipient immune response is measured by monitoring pharmacologic drug levels and clinical/pathologic evaluation of graft function. Development of reliable assays that can measure accurately the status of the immune response not only would help clinicians customize the prescription of immunosuppressive drugs in individual patients but also may allow their complete withdrawal in some patients with immunologic tolerance. Furthermore, these assays would facilitate the safe evaluation of novel tolerogenic regimens. Achieving this goal has proved to be very difficult because it requires both a more in-depth understanding of complex mechanisms of tolerance and also identification of transplant patients with acquired tolerance to an allograft that can be studied. This review discusses the current understanding of tolerance mechanisms and outlines the unique and specific challenges in development of tolerance/monitoring assays in the field of transplantation. In addition, several of the most promising candidate assays are discussed in detail.

Regulatory dendritic cell therapy in organ transplantation

Dendritic cells (DCs) are uniquely well equipped antigen (Ag)-presenting cells. Their classic function was thought to be that of potent initiators of innate and adaptive immunity to infectious organisms and other Ags (including transplanted organs). Evidence has emerged, however, that DCs have a central and crucial role in determining the fate of immune responses toward either immunity or tolerance. This dichotomous function of DCs, coupled with their remarkable plasticity, renders them attractive therapeutic targets for immune modulation. In transplantation, much recent work has focused on the ability of DCs to silence immune reactivity in an Ag-specific manner in the hope of preventing rejection and diminishing reliance on potentially harmful immunosuppressive agents. Experimental strategies have included in vivo targeting of DCs, as well as ex vivo generation of regulatory (or tolerogenic) DCs with subsequent reinfusion (i.e. cell therapy). Different approaches to 'program' DC toward tolerogenic properties include genetic (transgene insertion), biologic (differential culture conditions, anti-inflammatory cytokine exposure) and pharmacologic manipulation. Recent data suggest a promising role for pharmacologic treatment as a means of generating potent regulatory DCs and have further stimulated speculation regarding their potential clinical application. Herein, we discuss evidence that the potential of regulatory DC therapy is considerable and that there are compelling reasons to evaluate it in the setting of organ transplantation in the near future.