Effects of mycophenolate mofetil on donor-specific antibody formation in renal transplantation

Prevalence of mycophenolate mofetil discontinuation and subsequent outcomes in pediatric kidney transplant recipients: A PNRC study

BACKGROUND

Mycophenolate Mofetil (MMF) is an effective immunosuppressant used in kidney transplant recipients to prevent acute rejection. Complications such as diarrhea, leukopenia, and infections may necessitate the reduction or discontinuation of MMF. The objective of the study was to investigate the prevalence, timing, and reasons for MMF discontinuation and its association with outcomes in pediatric kidney transplant recipients.

METHODS

Seven Pediatric Nephrology Research Consortium (PNRC) centers participated in a retrospective analysis of kidney transplant recipients <21 years of age. Characteristics and outcomes of patients in whom MMF was discontinued were compared to those who continued taking MMF throughout the first 2 years post-transplant.

RESULTS

The study population included 288 participants (mean age 11.2 years) from 7 North American transplant centers. MMF was discontinued in 93/288 (32%) of participants. Common reasons for discontinuation included infections (35%), diarrhea (32%), leukopenia (15%), and others (18%). Increased cumulative alloimmunity (55% vs. 42%, p = .02), increased number of hospitalizations (82% vs. 67%, p = .01), and viral replications (79% vs. 47%, p < .0001) were observed in the MMF discontinuation group compared to the continuation group. Greater eGFR decline also occurred in the MMF discontinuation group over 2 years of follow-up (-7 vs. -1 mL/min/1.73 m2 , p = .05).

CONCLUSIONS

Almost a third of pediatric kidney transplant recipients who begin MMF for maintenance immunosuppression have it discontinued within the first 2 years post-transplant, and this subset of patients is more likely to experience adverse outcomes. New strategies are needed to manage MMF therapy and improve post-transplant outcomes.

Preventing Rejection of the Kidney Transplant

With increasing knowledge of immunologic factors and with the advent of potent immunosuppressive agents, the last several decades have seen significantly improved kidney allograft survival. However, despite overall improved short to medium-term allograft survival, long-term allograft outcomes remain unsatisfactory. A large body of literature implicates acute and chronic rejection as independent risk factors for graft loss. In this article, we review measures taken at various stages in the kidney transplant process to minimize the risk of rejection. In the pre-transplant phase, it is imperative to minimize the risk of sensitization, aim for better HLA matching including eplet matching and use desensitization in carefully selected high-risk patients. The peri-transplant phase involves strategies to minimize cold ischemia times, individualize induction immunosuppression and make all efforts for better HLA matching. In the post-transplant phase, the focus should move towards individualizing maintenance immunosuppression and using innovative strategies to increase compliance. Acute rejection episodes are risk factors for significant graft injury and development of chronic rejection thus one should strive for early detection and aggressive treatment. Monitoring for DSA development, especially in high-risk populations, should be made part of transplant follow-up protocols. A host of new biomarkers are now commercially available, and these should be used for early detection of rejection, immunosuppression modulation, prevention of unnecessary biopsies and monitoring response to rejection treatment. There is a strong push needed for the development of new drugs, especially for the management of chronic or resistant rejections, to prolong graft survival. Prevention of rejection is key for the longevity of kidney allografts. This requires a multipronged approach and significant effort on the part of the recipients and transplant centers.

Pegloticase efficacy and safety in kidney transplant recipients; results of the phase IV, open-label PROTECT clinical trial

INTRODUCTION

Kidney transplant (KT) recipients have a high prevalence and severity of gout. Pegloticase (pegylated recombinant uricase) rapidly metabolizes serum uric acid (sUA), and its efficacy is not impacted by kidney function.

METHODS

This open-label, Phase 4 trial (PROTECT NCT04087720) examined safety and efficacy of pegloticase in 20 participants with KT > 1 year prior to enrollment and with uncontrolled gout (sUA ≥7 mg/dL, intolerance/inefficacy to urate lowering therapy, and ≥1 of the following: tophi, chronic gouty arthritis, ≥2 flares in past year) and functioning KT (estimated glomerular filtration rate [eGFR] ≥15 mL/min/1.73 m2 ) on stable immunosuppression therapy.

RESULTS

The primary endpoint was sUA response during month 6 (sUA < 6 mg/dL for ≥80% of time). The study enrolled 20 participants (mean ± SD); age: 53.9 ± 10.9 years, time since KT: 14.7 ± 6.9 years, sUA: 9.4 ± 1.5 mg/dL, gout duration: 8.4 ± 11.6 years; all on ≥2 stable doses of immunosuppression agents. Pegloticase (8 mg intravenous every 2 weeks) in KT recipients with uncontrolled gout showed a high response rate of 89% (16/18 responders). Two participants discontinued treatment solely due to COVID-19 concerns prior to month 6 were not included in the primary analysis. Pegloticase exposures were higher than those historically observed with pegloticase monotherapy, and no anaphylaxis or infusion reaction events occurred during the study.

CONCLUSIONS

This improved response rate to pegloticase in the KT population reflects observations from other trials and reports on immunomodulation with pegloticase. As the KT population has a high prevalence of gout and limitations with oral urate lowering medication options, these findings suggest a potential option for uncontrolled gout therapy in KT participants.

[Medication adherence in renal transplantation: Evaluation, predictive factors and impact on humoral alloreactivity]

OBJECTIVES

The aims of this study were to assess medication adherence to immunosuppressive treatment in kidney transplanted patients, to identify predictive factors of medication non-adherence and to analyse its impact on the development of Donor Specific Antibodies (DSA) de novo, biomarkers of rejection in transplant recipients.

METHODS

A cross-sectional single-centre study was conducted to assess medication adherence to immunosuppressive treatment with the BAASIS (Basel Assessment of Adherence Scale for Immunosuppressives) self-report questionnaire. Univariate and multivariate analyses were performed to determine non-adherence predictive factors and its role in the development of DSA de novo.

RESULTS

A total of 212 renal transplanted patients completed the BAASIS questionnaire: 36,3 % were non-adherent to their immunosuppressive treatment. Patient's age and taking azathioprine were independent predictors of non-adherence and "married or living together" family status was a protective factor in the multivariate analysis. Medication non-adherence was associated with DSA de novo development in the multivariate model and it multiplied their risk of development by 3.

CONCLUSIONS

This study, which detected a large proportion of patients who did not adhere to immunosuppressive treatment, highlighted non-adherence predictors and showed the association between non-adherence and development of DSA de novo. In case of non-adherent behavior, it is crucial to set up a personalised support for patients with a multidisciplinary approach of therapeutic education, in which the clinical pharmacist has a role.

High Tacrolimus Intrapatient Variability and Subtherapeutic Immunosuppression are Associated With Adverse Kidney Transplant Outcomes

BACKGROUND

Kidney transplant recipients with high intrapatient variability (IPV) in tacrolimus (Tac) exposure experience more rejection and reduced graft survival. To understand the underlying pathophysiology of this association, the authors investigated whether patients with high tacrolimus IPV have a more activated immune system than patients with low IPV. In addition, exposure to tacrolimus and mycophenolic acid (MPA) was studied in relation to rejection and graft survival.

METHODS

At the time of patient inclusion (5-7 years post-transplantation), the frequency of donor-reactive cells was determined by enzyme-linked immunosorbent assay, and the development of donor-specific anti-Human Leukocyte Antigen antibodies (DSA) was measured by Luminex Single Antigen assay. Tacrolimus IPV was retrospectively calculated between 6 and 12 months and the exposure to tacrolimus and MPA was determined between 1 and 5 years post-transplantation.

RESULTS

A total of 371 kidney transplant recipients were included in this study, of whom 56 developed a rejection episode after 12 months and 60 experienced graft failure after 5-7 years. No correlations were found between tacrolimus IPV or immunosuppression exposure and the number of donor-reactive cells after 5 years of transplantation. DSA were detected more often in patients with low exposure to both tacrolimus and MMF [4/21 (19%) versus 17/350 (4.9%), P = 0.04]. In this cohort, neither tacrolimus IPV nor low overall immunosuppression exposure was associated with a higher incidence of rejection. However, regression analysis showed that a higher tacrolimus IPV was associated with an increased incidence of graft failure (odds ratio = 1.03, P = 0.02).

CONCLUSIONS

This study verifies the relationship between high tacrolimus IPV and impaired kidney allograft survival in long-term follow-up. DSA was also found to be more prevalent in patients with subtherapeutic concentrations of tacrolimus and MPA. An increased prevalence of donor-specific alloreactivity is yet to be demonstrated in patients with high IPV.

No Influence of Everolimus on Mycophenolic Acid Area Under the Concentration-Time Curve: Limited Sampling Strategy for Mycophenolic Acid in Japanese Kidney Transplant Recipients Treated With Tacrolimus, Mycophenolate Mofetil, Steroid, and Everolimus

BACKGROUND

Despite a growing need for everolimus (EVR) to reduce calcineurin inhibitor toxicity in kidney transplantation (KTx), the influence of EVR on the pharmacokinetics of mycophenolic acid (MPA), a mycophenolate mofetil (MMF) active metabolite, is obscure, and no suitable limited sampling strategy (LSS) for MPA when EVR is concomitantly present exists. We aimed to investigate the influence of EVR on MPA pharmacokinetics in KTx.

MATERIALS AND METHODS

This study complied with all principles of the Declaration of Helsinki. Twenty patients were initially administered tacrolimus, MMF, and methylprednisolone and then received EVR 4 months after KTx. Approximately 4 weeks before and after EVR administration, the estimated value of the area under the concentration-time curve for MPA from 0 to 12 hours (MPA-AUC0-12) was calculated using MPA blood concentration just before and 1, 2, 4, and 6 hours after MMF administration. We compared several MPA pharmacokinetics parameters before and after EVR addition and determined the best estimation equation for LSS of MPA-AUC0-12.

RESULTS

Although MPA-C6 per dose (MPA-C6/D) significantly decreased after EVR addition (from 3.4 [±2.2] ng/mL/g to 2.5 [±0.9] ng/mL/g), MPA-C0/D, -C1/D, -C2/D, -C4/D, and MPA-AUC0-12/D showed no significant change. MPA-AUC0-12/D did not correlate with EVR-AUC0-12/D. The best estimation equation for LSS of MPA-AUC0-12 by 2 time points was [(2.94 × C2) + (5.09 × C4) + 5.32] (R² = 0.73) and [(5.70 × C0) + (1.39 × C1) + 22.45] (R² = 0.72) before and after EVR addition, respectively.

CONCLUSIONS

EVR can be safely combined with MMF after KTx once our results have been reevaluated.

Everolimus Reduces Cancer Incidence and Improves Patient and Graft Survival Rates after Kidney Transplantation: A Multi-Center Study

Kidney transplantation can prevent renal failure and associated complications in patients with end-stage renal disease. Despite the good quality of life, de novo cancers after kidney transplantation are a major complication impacting survival and there is an urgent need to establish immunosuppressive protocols to prevent de novo cancers. We conducted a multi-center retrospective study of 2002 patients who underwent kidney transplantation between 1965 and 2020 to examine patient and graft survival rates and cumulative cancer incidence in the following groups categorized based on specific induction immunosuppressive therapies: group 1, antiproliferative agents and steroids; group 2, calcineurin inhibitors (CNIs), antiproliferative agents and steroids; group 3, CNIs, mycophenolate mofetil, and steroids; and group 4, mammalian target of rapamycin inhibitors including everolimus, CNIs, mycophenolate mofetil, and steroids. The patient and graft survival rates were significantly higher in groups 3 and 4. The cumulative cancer incidence rate significantly increased with the use of more potent immunosuppressants, and the time to develop cancer was shorter. Only one patient in group 4 developed de novo cancer. Potent immunosuppressants might improve graft survival rate while inducing de novo cancer after kidney transplantation. Our data also suggest that everolimus might suppress cancer development after kidney transplantation.

Approaches for Controlling Antibody-Mediated Allograft Rejection Through Targeting B Cells

Both acute and chronic antibody-mediated allograft rejection (AMR), which are directly mediated by B cells, remain difficult to treat. Long-lived plasma cells (LLPCs) in bone marrow (BM) play a crucial role in the production of the antibodies that induce AMR. However, LLPCs survive through a T cell-independent mechanism and resist conventional immunosuppressive therapy. Desensitization therapy is therefore performed, although it is accompanied by severe side effects and the pathological condition may be at an irreversible stage when these antibodies, which induce AMR development, are detected in the serum. In other words, AMR control requires the development of a diagnostic method that predicts its onset before LLPC differentiation and enables therapeutic intervention and the establishment of humoral immune monitoring methods providing more detailed information, including individual differences in the susceptibility to immunosuppressive agents and the pathological conditions. In this study, we reviewed recent studies related to the direct or indirect involvement of immunocompetent cells in the differentiation of naïve-B cells into LLPCs, the limitations of conventional methods, and the possible development of novel control methods in the context of AMR. This information will significantly contribute to the development of clinical applications for AMR and improve the prognosis of patients who undergo organ transplantation.

Population pharmacokinetics of mycophenolic acid in paediatric patients

Mycophenolic acid (MPA) is widely used in paediatric kidney transplant patients and sometimes prescribed for additional indications. Population pharmacokinetic or pharmacodynamic modelling has been frequently used to characterize the fixed, random and covariate effects of MPA in adult patients. However, MPA population pharmacokinetic data in the paediatric population have not been systematically summarized. The objective of this narrative review was to provide an up-to-date critique of currently available paediatric MPA population pharmacokinetic models, with emphases on modelling techniques, pharmacological findings and clinical relevance. PubMed and EMBASE were searched from inception of database to May 2020, where a total of 11 studies have been identified representing kidney transplant (n = 4), liver transplant (n = 1), haematopoietic stem cell transplant (n = 1), idiopathic nephrotic syndrome (n = 2), systemic lupus erythematosus (n = 2), and a combined population consisted of kidney, liver and haematopoietic stem cell transplant patients (n = 1). Critical analyses were provided in the context of MPA absorption, distribution, metabolism, excretion and bioavailability in this paediatric database. Comparisons to adult patients were also provided. With respect to clinical utility, Bayesian estimation models (n = 6) with acceptable accuracy and precision for MPA exposure determination have also been identified and systematically evaluated. Overall, our analyses have identified unique features of MPA clinical pharmacology in the paediatric population, while recognizing several gaps that still warrant further investigations. This review can be used by pharmacologists and clinicians for improving MPA pharmacokinetic-pharmacodynamic modelling and patient care.

Optimizing Mycophenolic Acid Exposure in Kidney Transplant Recipients: Time for Target Concentration Intervention

The immunosuppressive agent mycophenolate is used extensively in kidney transplantation, yet dosing strategy applied varies markedly from fixed dosing ("one-dose-fits-all"), to mycophenolic acid (MPA) trough concentration monitoring, to dose optimization to an MPA exposure target (as area under the concentration-time curve [MPA AUC0-12]). This relates in part to inconsistent results in prospective trials of concentration-controlled dosing (CCD). In this review, the totality of evidence supporting mycophenolate CCD is examined: pharmacological characteristics, observational data linking exposure to efficacy and toxicities, and randomized controlled trials of CCD, with attention to dose optimization method and exposure achieved. Fixed dosing of mycophenolate consistently leads to underexposure associated with rejection, as well as overexposure associated with toxicities. When CCD is driven by pharmacokinetic calculation to a target concentration (target concentration intervention), MPA exposure is successfully controlled and clinical benefits are seen. There remains a need for consensus on practical aspects of mycophenolate target concentration intervention in contemporary tacrolimus-containing regimens and future research to define maintenance phase exposure targets. However, given ongoing consequences of both overimmunosuppression and underimmunosuppression in kidney transplantation, impacting short- and long-term outcomes, these should be a priority. The imprecise "one-dose-fits-all" approach should be replaced by the clinically proven MPA target concentration strategy.

Clazakizumab in late antibody-mediated rejection: study protocol of a randomized controlled pilot trial

Background

Late antibody-mediated rejection (ABMR) triggered by donor-specific antibodies (DSA) is a cardinal cause of kidney allograft dysfunction and loss. Diagnostic criteria for this rejection type are well established, but effective treatment remains a major challenge. Recent randomized controlled trials (RCT) have failed to demonstrate the efficacy of widely used therapies, such as rituximab plus intravenous immunoglobulin or proteasome inhibition (bortezomib), reinforcing a great need for new therapeutic concepts. One promising target in this context may be interleukin-6 (IL-6), a pleiotropic cytokine known to play an important role in inflammation and adaptive immunity.

Methods

This investigator-driven RCT was designed to assess the safety and efficacy of clazakizumab, a genetically engineered humanized monoclonal antibody directed against IL-6. The study will include 20 DSA-positive kidney allograft recipients diagnosed with ABMR ≥ 365 days after transplantation. Participants will be recruited at two study sites in Austria and Germany (Medical University of Vienna; Charité University Medicine Berlin). First, patients will enter a three-month double-blind RCT (1,1 randomization, stratification according to ABMR phenotype and study site) and will receive either clazakizumab (subcutaneous administration of 25 mg in monthly intervals) or placebo. In a second open-label part of the trial (months 4–12), all patients will receive clazakizumab at 25 mg every month. The primary endpoint is safety and tolerability. Secondary endpoints are the pharmacokinetics and pharmacodynamics of clazakizumab, its effect on drug metabolism in the liver, DSA characteristics, morphological ABMR lesions and molecular gene expression patterns in three- and 12-month protocol biopsies, serum/urinary biomarkers of inflammation and endothelial activation/injury, Torque Teno viral load as a measure of overall immunosuppression, kidney function, urinary protein excretion, as well as transplant and patient survival.

Discussion

Currently, there is no treatment proven to be effective in halting the progression of late ABMR. Based on the hypothesis that antagonizing the effects of IL-6 improves the outcome of DSA-positive late ABMR by counteracting DSA-triggered inflammation and B cell/plasma cell-driven alloimmunity, we suggest that our trial has the potential to provide proof of concept of a novel treatment of this type of rejection.

Trial registration

ClinicalTrials.gov, NCT03444103. Registered on 23 February 2018 (retrospective registration).

Electronic supplementary material

The online version of this article (10.1186/s13063-018-3158-6) contains supplementary material, which is available to authorized users.

Anti-citrullinated protein antibody response after primary EBV infection in kidney transplant patients

Rheumatoid arthritis (RA) is a chronic inflammatory disease of synovial joints, characterized by the presence of the highly disease-specific anti-citrullinated protein antibodies (ACPA) in approximately 70% of patients. Epstein-Barr virus (EBV) has previously been suggested to be involved in the pathophysiology of RA. However, given the high incidence of EBV in the general population and the difficulty of detecting initial infection, providing a direct link between EBV infection and RA development has remained elusive. We hypothesized that primary EBV infection may be a trigger for the development of the ACPA response in vivo. Using a unique cohort of 26 kidney transplant patients with a primary EBV infection, the presence of ACPA before and following infection was determined. No increase in IgG anti-CCP2 titers was detected following EBV infection. IgG anti-CCP2 antibodies were present in two patients and borderline positive in another. These three patients were HLA-DR4 negative. To test whether EBV infection may trigger a non-class switched anti-CCP2 response, IgM anti-CCP2 antibodies were analyzed. No general trend in the IgM anti-CCP2 response was observed following EBV infection. Since two out of the three IgG anti-CCP2 (borderline) positive patients were diagnosed with IgA nephropathy, 23 additional IgA nephropathy patients were tested for IgG anti-CCP2, regardless of their EBV status. All of these patients were IgG anti-CCP2 negative, indicating that IgG anti-CCP2 is not commonly present in IgA nephropathy patients. Collectively, these data do not support the hypothesis that EBV does trigger the highly RA specific ACPA response.

Effect of Early Immunosuppression Therapy on De Novo Anti-Human-Leukocyte-Antigen Antibody After Kidney Transplantation

The aim of the study was to investigate the effect of immunosuppression therapy early after kidney transplantation, particularly exposure of mycophenolic acid (MPA) and calcineurin inhibitor (CNI), on posttransplantation de novo HLA antibody production.

METHODS

A single-center retrospective cohort study was performed at the First Affiliated Hospital of Sun Yat-sen University, enrolling the kidney transplant or pancreas-kidney transplant recipients who had surgery between January 2010 and February 2016.

RESULTS

A total of 214 recipients were included in the study with a median follow-up period of 1.06 years. A total of 30 recipients (14.0%) were positive in HLA antibody detection posttransplant with a median follow-up period of 1.46 years. Ten recipients (4.7%) lost their allograft function during follow-up, and 6 of them (60%) developed de novo HLA antibody after graft failure. Multivariate analysis showed that acute rejection significantly increased the risk of de novo HLA antibody (hazard ratio [HR], 2.732). Intensified MPA dosing therapy reduced the risk by 59.8% (HR, 0.402); low-dose CNI therapy increased the risk by 33.3% (HR, 1.333), and the effect of extremely low-dose CNI therapy was even larger (HR, 2.242).

CONCLUSION

The risk of de novo HLA antibody can be decreased by reducing the risk of acute rejection. A tendency was seen in low-dose CNI therapy to increase the risk of de novo HLA antibody, but intensified MPA dosing therapy may provide an umbrella protection effect by reducing the risk. Prospective study was required to confirm the effects.

A Randomized Trial of Bortezomib in Late Antibody-Mediated Kidney Transplant Rejection

Late antibody-mediated rejection (ABMR) is a leading cause of kidney allograft failure. Uncontrolled studies have suggested efficacy of the proteasome inhibitor bortezomib, but no systematic trial has been undertaken to support its use in ABMR. In this randomized, placebo-controlled trial (the Bortezomib in Late Antibody-Mediated Kidney Transplant Rejection [BORTEJECT] Trial), we investigated whether two cycles of bortezomib (each cycle: 1.3 mg/m² intravenously on days 1, 4, 8, and 11) prevent GFR decline by halting the progression of late donor-specific antibody (DSA)-positive ABMR. Forty-four DSA-positive kidney transplant recipients with characteristic ABMR morphology (median time after transplant, 5.0 years; pretransplant DSA documented in 19 recipients), who were identified on cross-sectional screening of 741 patients, were randomly assigned to receive bortezomib (n=21) or placebo (n=23). The 0.5-ml/min per 1.73 m² per year (95% confidence interval, -4.8 to 5.8) difference detected between bortezomib and placebo in eGFR slope (primary end point) was not significant (P=0.86). We detected no significant differences between bortezomib- and placebo-treated groups in median measured GFR at 24 months (33 versus 42 ml/min per 1.73 m²; P=0.31), 2-year graft survival (81% versus 96%; P=0.12), urinary protein concentration, DSA levels, or morphologic or molecular rejection phenotypes in 24-month follow-up biopsy specimens. Bortezomib, however, associated with gastrointestinal and hematologic toxicity. In conclusion, our trial failed to show that bortezomib prevents GFR loss, improves histologic or molecular disease features, or reduces DSA, despite significant toxicity. Our results reinforce the need for systematic trials to dissect the efficiency and safety of new treatments for late ABMR.

Antibody response to HBV vaccination on dialysis does not correlate with the development of deNovo anti-HLA antibodies after renal transplantation

BACKGROUND

Response to Hepatitis B virus (HBV) vaccination can be diminished in some (50-80%) but not all dialysis patients. We hypothesized, that the response to vaccination on dialysis may correlate with the development of anti-HLA antibodies after renal transplantation and might therefore be a valuable parameter to predict alloresponses.

METHODS

The response to HBV vaccination on dialysis and the development of deNovo anti-HLA antibodies post-transplant was analyzed in 188 non-immunized renal transplant recipients. The response to HBV vaccination was evaluated by measuring the anti-HBs titer at time of transplantation. Anti-HLA antibodies post-transplant were monitored by serial measurements by means of Luminex. Acute rejection episodes, graft loss and renal dysfunction were assessed within a median follow-up of 5.5years.

RESULTS

One hundred and forty-one patients (75%) exhibited an adequate immune response to HBV vaccination on dialysis. Vaccine responder (R) and none responder (NR) did not differ with respect to age, gender and BMI, while R spend significantly more time on dialysis before transplantation (4.58±3.35 vs 3.23±2.55 years, p=0.033). More NR developed deNovo anti-HLA antibodies (27.7 vs 22.7%, p=0.554) and donor-specific anti-HLA antibodies (23.4 vs 14.2%, p=0.173) in comparison to R. Accordingly, the number of acute rejections was higher in NR as compared to R (36.1 vs 24.1%, p=0.130) while graft survival was similar in both groups.

CONCLUSION

Contrary to our hypothesis antibody response to HBV vaccination on dialysis does not predict the development of anti-HLA antibodies post transplant.

Maintenance immunosuppressants in the management of antibody-mediated renal allograft rejection: which regimen is best?

Antibody-mediated rejection (AMR) is a pivotal cause of long-term graft failure following renal transplantation. De novo donor-specific antibody reduction is essential to prevent AMR and improve long-term graft survival in renal transplant recipients. Although the number of early AMR episodes can be successfully controlled by attenuating de novo donor-specific antibodies, the long-term outcomes are unsatisfactory. Numerous studies have focused on new strategies to reverse AMR, but the available evidence suggests that maintenance immunosuppressive agents play important roles. This article reviews data on the use of various maintenance immunosuppressive strategies in the management of AMR, with a focus on antibody-mediated kidney transplant rejection. Its aim is to help provide options benefitting long-term graft survival in renal transplant recipients.

Prospective Clinical Testing of Regulatory Dendritic Cells in Organ Transplantation

Dendritic cells (DC) are rare, professional antigen-presenting cells with ability to induce or regulate alloimmune responses. Regulatory DC (DCreg) with potential to down-modulate acute and chronic inflammatory conditions that occur in organ transplantation can be generated in vitro under a variety of conditions. Here, we provide a rationale for evaluation of DCreg therapy in clinical organ transplantation with the goal of promoting sustained, donor-specific hyporesponsiveness, while lowering the incidence and severity of rejection and reducing patients’ dependence on anti-rejection drugs. Generation of donor- or recipient-derived DCreg that suppress T cell responses and prolong transplant survival in rodents or non-human primates has been well-described. Recently, good manufacturing practice (GMP)-grade DCreg have been produced at our Institution for prospective use in human organ transplantation. We briefly review experience of regulatory immune therapy in organ transplantation and describe our experience generating and characterizing human monocyte-derived DCreg. We propose a phase I/II safety study in which the influence of donor-derived DCreg combined with conventional immunosuppression on subclinical and clinical rejection and host alloimmune responses will be examined in detail.

Review of bortezomib treatment of antibody-mediated rejection in renal transplantation

SIGNIFICANCE

Development of donor-specific antibodies (DSA) after kidney transplantation is associated with reduced allograft survival. A few strategies have been tested in controlled clinical trials for the treatment of antibody-mediated rejection (AMR), and no therapies are approved by regulatory authorities. Thus development of antihumoral therapies that provide prompt elimination of DSA and improve allograft survival is an important goal.

RECENT ADVANCES

Proteasome inhibitor (PI)-based regimens provide a promising new approach for treating AMR. To date, experiences have been limited to off-label bortezomib use in AMR. Key findings with PI-based therapy are that they provide effective primary and rescue therapy for AMR by prompt reduction in immunodominant DSA and improvements in histologic and renal function. Early and late AMR differ immunologically and in response to PI therapy. Bortezomib-related toxicities in renal transplant recipients are similar to those observed in the multiple myeloma population.

CRITICAL ISSUES

Although preliminary evidence with PI therapy for AMR is encouraging, the evidence is limited. Larger, prospective, randomized controlled trials with long-term follow up are needed. Advancement in endpoints of clinical trial designs and rigorous clinical trials with more standardized adjunct therapies are also required to explore the risks and benefits of AMR treatment modalities.

FUTURE DIRECTIONS

In the next few years, new PIs are likely to be introduced and new approaches would be developed for achieving synergy with PIs. The ultimate goal will be to develop a regimen that delivers reliable, rapid, complete, and durable elimination of DSA with an acceptable safety profile.

Renal allograft transplant recipient with ruptured hydatid native kidney

Echinococcosis of the kidneys in a renal transplant recipient is extremely rare and its occurrence being related to immunosuppression is a possibility which needs further characterisation. Ruptured renal hydatid in a renal transplant recipient is not reported so far to our best knowledge. We present a 42-year-old renal allograft receipient who presented one year after transplant with left flank pain, palpable left lumbar mass and gross hydatiduria. Investigations revealed a ruptured native hydatid kidney. Patient was managed with a combination of chemotherapy and left native nephrectomy and discharged in a satisfactory condition.

Can a combined screening/treatment programme prevent premature failure of renal transplants due to chronic rejection in patients with HLA antibodies: study protocol for the multicentre randomised controlled OuTSMART trial

BACKGROUND

Renal transplantation is the best treatment for kidney failure, in terms of length and quality of life and cost-effectiveness. However, most transplants fail after 10 to 12 years, consigning patients back onto dialysis. Damage by the immune system accounts for approximately 50% of failing transplants and it is possible to identify patients at risk by screening for the presence of antibodies against human leukocyte antigens. However, it is not clear how best to treat patients with antibodies. This trial will test a combined screening and treatment protocol in renal transplant recipients.

METHODS/DESIGN

Recipients>1 year post-transplantation, aged 18 to 70 with an estimated glomerular filtration rate>30 mL/min will be randomly allocated to blinded or unblinded screening arms, before being screened for the presence of antibodies. In the unblinded arm, test results will be revealed. Those with antibodies will have biomarker-led care, consisting of a change in their anti-rejection drugs to prednisone, tacrolimus and mycophenolate mofetil. In the blinded arm, screening results will be double blinded and all recruits will remain on current therapy (standard care). In both arms, those without antibodies will be retested every 8 months for 3 years. The primary outcome is the 3-year kidney failure rate for the antibody-positive recruits, as measured by initiation of long-term dialysis or re-transplantation, predicted to be approximately 20% in the standard care group but <10% in biomarker-led care. The secondary outcomes include the rate of transplant dysfunction, incidence of infection, cancer and diabetes mellitus, an analysis of adherence with medication and a health economic analysis of the combined screening and treatment protocol. Blood samples will be collected and stored every 4 months and will form the basis of separately funded studies to identify new biomarkers associated with the outcomes.

DISCUSSION

We have evidence that the biomarker-led care regime will be effective at preventing graft dysfunction and expect this to feed through to graft survival. This trial will confirm the benefit of routine screening and lead to a greater understanding of how to keep kidney transplants working longer.

TRIAL REGISTRATION

Current Controlled Trials ISRCTN46157828.

Management of antibody-mediated rejection in transplantation

Despite intensive traditional immunosuppressive therapy, rates of graft loss have approximated 15% to 20% at 1 year following antibody-mediated rejection (AMR) in solid organ transplant recipients. Therefore, the development of antihumoral therapies that provide prompt elimination of donor-specific anti-HLA antibodies and improve allograft survival is an important goal. Traditional treatment modalities for AMR deplete B-cell populations but not the cell at the source of antibody production, the mature plasma cell. Plasma cell-targeted therapies using proteasome inhibition is a novel approach to treating AMR. This review discusses current and emerging treatment modalities used for AMR.

Panel-reactive antibody levels and renal transplantation rates in sensitized patients after desensitization and human leucocyte antigen amino acid residue matching

OBJECTIVE

To determine whether a new desensitization protocol (mycophenolate mofetil [MMF], plasmapheresis and antithymocyte globulin [ATG], complemented with human leucocyte antigen [HLA] amino acid residue matching) could reduce panel-reactive antibody (PRA) levels in sensitized patients, to facilitate successful renal transplantation.

METHODS

Patients awaiting transplantation with PRA levels >10% received treatment with MMF; those with PRA levels >30% were also treated with plasmapheresis. Patients whose PRA level was <20% after desensitization were eligible for transplantation. When a donor became available, traditional HLA matching and HLA amino acid residue matching were performed. All patients received ATG induction therapy postoperatively.

RESULTS

Thirty-two sensitized patients were enrolled. Desensitization produced a significant decrease in PRA levels; 27 patients (84.4%) became eligible for transplantation and 26 (81.2%) subsequently underwent successful transplantation. Residue matching improved the proportion with a mismatch number of 0-1 from 7.7% to 65.4%, compared with traditional HLA matching. Postoperatively, all patients showed immediate graft function. Acute rejection occurred in three patients (11.5%) and infections in seven patients (25.9%); all were treated successfully.

CONCLUSION

The combination of a desensitization protocol (MMF, plasmapheresis and ATG) and residue matching appears to be an effective strategy for sensitized patients awaiting renal transplantation.

The role of B cells in solid organ transplantation

The role of antibodies in chronic injury to organ transplants has been suggested for many years, but recently emphasized by new data. We have observed that when immunosuppressive potency decreases either by intentional weaning of maintenance agents or due to homeostatic repopulation after immune cell depletion, the threshold of B cell activation may be lowered. In human transplant recipients the result may be donor-specific antibody, C4d+ injury, and chronic rejection. This scenario has precise parallels in a rhesus monkey renal allograft model in which T cells are depleted with CD3 immunotoxin, or in a CD52-T cell transgenic mouse model using alemtuzumab to deplete T cells. Such animal models may be useful for the testing of therapeutic strategies to prevent DSA. We agree with others who suggest that weaning of immunosuppression may place transplant recipients at risk of chronic antibody-mediated rejection, and that strategies to prevent this scenario are needed if we are to improve long-term graft and patient outcomes in transplantation. We believe that animal models will play a crucial role in defining the pathophysiology of antibody-mediated rejection and in developing effective therapies to prevent graft injury. Two such animal models are described herein.

Inferior kidney allograft outcomes in patients with de novo donor-specific antibodies are due to acute rejection episodes

BACKGROUND

Donor-specific antibodies (DSAs) after kidney transplantation have been associated with poor graft outcomes in multiple studies. However, these studies have generally used stored sera or a single cross sectional screening test to identify patients with DSA. We evaluated the effectiveness of a prospective DSA screening protocol in identifying kidney and kidney/pancreas recipients at risk for poor graft outcomes.

METHODS

From September 2007 through September 2009, 244 consecutively transplanted kidney and kidney/pancreas recipients without pretransplant DSA were screened for de novo DSA at 1, 6, 12, and 24 months and when clinically indicated.

RESULTS

DSA was detected in 27% of all patients by protocol or indication screening. Patients with DSA (DSA+) were significantly more likely to have experienced acute rejection (AR) compared with no DSA (DSA-) (29% vs. 9.5%, P<0.001), and lower estimated 2-year graft survival (83% vs. 98%, P<0.001). Only 3 of 19 DSA (+) patients with AR had DSA detected before the AR episode. When excluding patients with AR, 2-year graft survival was similar between DSA (+) and DSA (-) patients (100% vs. 99%) as was estimated glomerular filtration rate. Patients with DSA detected by protocol screening had similar outcomes compared with DSA (-), whereas those with DSA detected by indication experienced significantly worse outcomes.

CONCLUSIONS

Patients with de novo DSA experience worse graft outcomes due to previous/concurrent episodes of AR. A prospective DSA screening protocol failed to identify patients at risk for AR or poor short-term graft outcomes.

Effect of immunosuppression for first kidney or kidney/pancreas transplant on sensitization at the time of second transplant

BACKGROUND

Previously transplanted patients are more likely to be sensitized, leading to prolonged waitlist times and decreased graft survival. This analysis of the United Network for Organ Sharing kidney/pancreas transplant database investigates factors at the time of first transplant associated with increased sensitization in patients undergoing second transplantation.

METHODS

Records of nonsensitized patients (panel reactive antibodies [PRA] <20%) receiving a primary transplant in 1999 or later were analyzed to determine whether immunosuppressive agents at the time of first transplant were associated with a change in PRA from first to second transplant. Variables included gender, race, human leukocyte antigen (HLA) mismatch, rabbit antithymocyte globulin (RATG), interleukin-2 receptor antagonists, tacrolimus (FK), cyclosporine A (CSA), and mycophenolate mofetil/sodium (MMF).

RESULTS

For the primary endpoint of increase in PRA greater than or equal to 20%, African Americans (AA) versus non-AA (OR 2.63, P<0.0001) and HLA nonzero mismatch versus zero mismatch (OR 2.90, P<0.0001) were associated with increased sensitization. The effect of immunosuppressive regimen depended on race and HLA status. In non-AAs/HLA mismatch (1-6), interleukin-2 receptor antagonists versus RATG (OR 1.40, P=0.001), CSA versus FK (OR 1.69, P<0.001) and no MMF versus MMF (OR 1.39, P<0.001) were also associated with increased sensitization. In AAs/HLA mismatch (1-6), no induction versus RATG (OR 1.59, P=0.031) and CSA versus FK (OR 1.68, P=0.006) were associated with increased sensitization.

CONCLUSIONS

These data suggest a reduced risk of sensitization at the time of second transplant when using more potent immunosuppression with RATG, FK, and MMF for nonsensitized primary kidney or kidney/pancreas transplant patients. These effects seem to be related to race and HLA mismatch.

Effect of the proteasome inhibitor bortezomib on humoral immunity in two presensitized renal transplant candidates

BACKGROUND

Recipient presensitization represents a major hurdle to successful renal transplantation. Previous case series have suggested that the proteasome inhibitor bortezomib directly affects the alloantibody-secreting plasma cells in rejecting allograft recipients. However, the ability of this agent to desensitize nonimmunosuppressed transplant candidates before transplantation is currently unknown.

METHODS

In this analysis, two sensitized hemodialysis patients were selected to receive two subsequent bortezomib cycles. Bortezomib was given at 1.3 mg/m(2) on days 1, 4, 8, and 11. Dexamethasone was added to the second cycle to enhance treatment efficiency. Serial immune monitoring included cytotoxic panel reactive antibody testing, Luminex single antigen testing for anti-human leukocyte antigen (HLA) IgG with or without C4d-fixing capability, and ABO antibody detection.

RESULTS

During a half-year follow-up period, cytotoxic panel reactive antibody decreased from 87% to 80% (patient 1) and 37% to 13% (patient 2). Patient 1 showed a 40% reduction in binding intensities of identified Luminex HLA single antigen reactivities and, in parallel, slight reductions in ABO blood group antibody and total immunoglobulin levels. In patient 2, bortezomib did not affect circulating antibody levels in a meaningful way. Both patients showed a more than 50% reduction in the levels of anti-HLA antibody-triggered C4d deposition to Luminex beads.

CONCLUSION

Our initial experience suggests that, without additional immunosuppressive measures, bortezomib has modest effects on circulating antibodies against HLA or blood group antigens. The reduced levels of antibody-triggered complement fixation, however, imply potential clinical relevance of proteasome inhibition for recipient desensitization.

De novo HLA sensitization and antibody mediated rejection following pregnancy in a heart transplant recipient

Here we report a case wherein both donor-specific and third-party, paternal, HLA class II specific antibodies developed following a spontaneous miscarriage resulting in antibody-mediated rejection in a patient who had undergone an orthotopic cardiac transplant six years earlier.

Mycophenolic acid inhibits maturation and function of human dendritic cells and B cells

Mycophenolic acid (MPA) is considered an immunosuppressive compound mainly because of its inhibitory effects on lymphocyte proliferation. Here we studied specifically the effects of MPA on the ability of dendritic cells (DCs) to activate T cells via the indirect pathway and on the maturation and function of B-lineage cells. We demonstrated that DC cell-surface receptors, associated with antigen uptake and antigen processing and presentation (CD83 and CD205), were differentially downregulated in the presence of MPA, translating into a decreased uptake of alloantigens and reduced stimulation of T cells with decreased cytokine secretion (interleukin (IL)-1Ra and transforming growth factor (TGF)-alpha). Similarly, MPA significantly inhibited B-cell differentiation into memory and plasma cells in vitro and decreased secretion of TNF-alpha, IL-1Ra, and IL-10. We further demonstrated for the first time that not only the amount of antibody secretion was significantly lowered in the presence of MPA but also the total number of antibody-producing cells was reduced. Importantly, we provide direct evidence that HLA-specific antibody secretion was also affected using a newly developed HLA antibody-specific B-cell enzyme-linked immunospot assay. Our data indicate additional pathways by which MPA downregulates the immune system. This in turn may lead to improved conditions for allograft tolerance and control of allograft rejection.

Relevance of Posttransplant Flow Cytometric T- and B-cell Crossmatches in Tacrolimus-Treated Renal Transplant Patients

BACKGROUND

De novo development of anti-human leukocyte antigen (HLA) antibodies after transplantation is associated with increased rejection and decreased graft survival. In this study, the effect of posttransplant HLA antibodies on clinical outcome was evaluated in patients treated with tacrolimus by means of flow cytometric crossmatches (FCXm).

METHODS

T- and B-cell FCXm were performed retrospectively on posttransplant sera of patients who received a graft between 1997 and 1999. Ninety-four kidney-only recipients were tested and all FCXm positive sera were investigated for the presence of HLA class I and II antibodies by Flow panel reactive antibodies.

RESULTS

From 94 patients with a negative pretransplant complement-dependent cytotoxicity crossmatch, seven (7%) showed a positive pretransplant FCXm. After transplantation the FCXm became positive in five patients (6%). The predictive value of a positive FCXm after transplantation, and the log-transformed relative change in fluorescence ratio between pretransplant and posttransplant serum, were not significant to rejection within six months, nor to graft survival censored for death.

CONCLUSIONS

The presence of HLA antibodies before rejection or graft failure could only be shown in a minority of patients; most antibodies were detected after graft failure, especially after transplantectomy. Monitoring through antibody testing after transplantation on the basis of our results has no added value with tacrolimus-based immunosuppression.

Treatment of early mixed cellular and humoral renal allograft rejection with tacrolimus and mycophenolate mofetil

This prospective study investigated the efficiency of the tacrolimus (Tac) combined with mycophenolate mofetil (MMF) alone without immunoadsorption (IA) or plasmapheresis (PPH) as treatment for early (within 2 weeks) acute humoral rejection (AHR) in non-sensitized renal allograft recipients. Of 160 patients enrolled in this prospective study, 11 patients had histologically and clinically confirmed early steroid-resistant acute rejection with an antibody response and received Tac-MMF therapy. No other aggressive rescue methods such as IA, PPH were used, according to the study design. Patients (n=11) were followed for 13.8+/-3.5 months; nine were females. The complement-dependent cytotoxicity crossmatch was negative before transplantation in all patients and only positive for panel-reactive antibody in one patient. Most of the rejection episodes were mixed with cellular rejection (four patients met Banff IIA criteria, five patients met Banff IIB, one patient met Banff IB, and one patient met Banff borderline). After 16.19+/-6.16 days of treatment, all rejection episodes were successfully reversed and all graft functions were stable, with a mean serum creatinine level of 1.12+/-0.32 mg/dl during follow-up. No patient suffered from severe infectious complications (except one case of urinary infection). Our investigation suggests that Tac combined with MMF alone is adequate to reverse early mixed cellular and humoral C4d-positive rejection in non-sensitized renal allograft recipients.

Rescue therapy with tacrolimus and mycophenolate mofetil does not prevent deterioration of graft function in C4d-positive chronic allograft nephropathy

BACKGROUND

Humoral alloresponses may contribute to chronic allograft nephropathy (CAN) in a subset of kidney transplant recipients. For chronic humoral rejection, the efficacy of rescue therapy with tacrolimus and mycophenolate mofetil has been suggested.

METHODS

Eleven recipients with C4d-positive CAN (index biopsy performed after a median of 3 years posttransplantation), who had been on cyclosporine A-based immunosuppression, were converted to tacrolimus, and if not part of basal therapy, to mycophenolate mofetil. We evaluated the effect of this tacrolimus/mycophenolate mofetil rescue therapy on clinical outcomes and on alloantibody formation detected with flow cytometric testing of panel-reactive antibody.

RESULTS

Tacrolimus/mycophenolate mofetil rescue therapy (plus anti-rejection treatment in six recipients with additional signs of acute cellular rejection) failed to prevent progressive deterioration of graft function. Four patients returned to dialysis after 4 to 18 months. Serial post-transplant serology detected HLA class I and/or II reactivity in seven recipients. Tacrolimus/mycophenolate mofetil therapy did not affect the time course of alloantibody levels. One patient with C4d-positive transplant glomerulopathy, who did not respond to tacrolimus/mycophenolate mofetil rescue therapy, developed nephrotic-range proteinuria associated with a rapid decline of allograft function. Despite considerable reduction in alloantibody levels and nearly complete clearance of C4d deposits, immunoadsorption failed to prevent graft failure in this patient.

CONCLUSION

Our data argue against the efficacy of tacrolimus/mycophenolate mofetil rescue therapy in established C4d-positive chronic allograft dysfunction. Prospective trials are needed to evaluate whether early initiation of this or other antihumoral strategies are capable of effectively preventing alloantibody-mediated chronic graft injury.

Transplant-related immunosuppression: a review of immunosuppression and pulmonary infections

Solid organ and hematopoietic stem cell transplantation are definitive therapies for a variety of end-stage diseases. Immunosuppression has improved graft survival but leaves the patient susceptible to infectious complications. Of these, pulmonary infections are the leading cause of morbidity and mortality in the transplant recipient. Allograft rejection is mediated primarily by T cells, with B cells playing a role via antibody production. Depending on the transplant type, rejection can be hyperacute, acute, or chronic. Hyperacute rejection occurs as an immediate response to preformed antibodies to donor human leukocyte antigens. Acute cellular rejection involves recipient T-cell recognition of human leukocyte antigen molecules expressed on donor-derived, antigen-presenting cells (direct allorecognition) or presentation of donor-derived peptides by recipient antigen-presenting cells to recipient T cells (indirect allorecognition). Once the alloantigens are recognized as foreign, the activation, proliferation, and production of cytokines by T lymphocytes and other immune cells lead to the amplification of the alloimmune response. This complex process involves the generation of effector T cells, antibody production by activated B cells, and macrophage activation. Alloimmunity is facilitated by the production of many cytokines, chemokines, and other effector molecules, such as complement. The immunosuppressants involve many classes of drugs, including antibody therapies that eliminate specific groups of cells or alter signaling pathways used by effector cells. The article reviews the agents and associated infections.

Simultaneous vs. Sequential Laparoscopic Bilateral Native Nephrectomy and Renal Transplantation

We reviewed our experience with simultaneous single incision bilateral native nephrectomy and renal transplantation in 11 patients (Group 1), compared to seven recipients who underwent staged laparoscopic bilateral nephrectomy followed by kidney transplantation (Group 2). Mean age, donor source, sex, cause of ESRD, and specimen size were similar in both groups (P=0.1). All Group 2 patients and 9 of 11 Group 1 patients had autosomal-dominant polycystic kidney disease. Perioperative Group 1 complications included: bowel injury, transplant urine leak, necrotic pancreatitis, delayed bowel movement, and severe shoulder pain secondary to diaphragmatic irritation. Seven (63.6%) Group 1 patients required an additional surgical procedure: midline incisional hernia, repair ureteral fistula, and repair enterocutaneous fistula. One Group 1 patient lost his graft secondary to bowel injury and intra-abdominal sepsis. No major complications, reoperations, or graft loss occurred in Group 2. For simultaneous bilateral native nephrectomy and kidney transplantation, over 60% of patients required an additional surgical procedure. Laparoscopic bilateral nephrectomy followed by kidney transplantation is a safe and feasible alternative.