The utility of 1- and 3-month protocol biopsies on renal allograft function: a randomized controlled study

The Value of Protocol Biopsy in Kidney Transplantation on Monitoring Transplant Outcomes: A Systematic Review and Meta-Analysis

BACKGROUND

There is a great debate about the role of biopsies per protocol in kidney transplant recipients, and the published studies show contradictory results. We aimed to assess the safety and effectiveness of protocol biopsies in kidney transplant recipients in improving short- and long-term outcomes.

METHODS

We conducted searches until July of 2023 to identify all randomized clinical trials (RCT). Studies were identified through search strategies for CENTRAL, MEDLINE, EMBASE, and LILACS. Titles and abstracts were screened independently by 2 authors; 2 authors independently assessed retrieved abstracts and the full text. Assessment of risk of bias was carried out using the Cochrane risk of bias tool. The outcomes of interest were: Acute rejection, graft loss, mortality, glomerular filtration rate, and safety outcomes. Meta-analysis was performed for variables of interest when appropriate. Quality of evidence was assessed using GRADE methodology.

RESULTS

We screened 5,695 records. Four trials met all eligibility criteria. No benefit of protocol biopsy was found in detecting acute rejection (3 studies RR: 2.0, 95% CI: 0.68-5.85, p = .2) or preventing graft loss at 12 months (2 studies, RR 0.33, 95% CI 0.06-1.72, p = .19). No differences were found between the groups in the glomerular filtration rate at 6 months post-transplantation (2 studies, MD 2.97, 95% CI 1.4-7.3, p = .18). A total of 23 safety events were present in the biopsy group compared to six in the control group.

CONCLUSION

No benefit was found in performing protocol biopsy following kidney transplantation.

Blood Gene Signature as a Biomarker for Subclinical Kidney Allograft Rejection: Where Are We?

The observation decades ago that inflammatory injuries because of an alloimmune response might be present even in the absence of concomitant clinical impairment in allograft function conduced to the later definition of subclinical rejection. Many studies have investigated the different subclinical rejections defined according to the Banff classification (subclinical T cell-mediated rejection and antibody-mediated rejection), overall concluding that these episodes worsened long-term allograft function and survival. These observations led several transplant teams to perform systematic protocolar biopsies to anticipate treatment of rejection episodes and possibly prevent allograft loss. Paradoxically, the invasive characteristics and associated logistics of such procedures paved the way to investigate noninvasive biomarkers (urine and blood) of subclinical rejection. Among them, several research teams proposed a blood gene signature developed from cohort studies, most of which achieved excellent predictive values for the occurrence of subclinical rejection, mainly antibody-mediated rejection. Interestingly, although all identified genes relate to immune subsets and pathways involved in rejection pathophysiology, very few transcripts are shared among these sets of genes, highlighting the heterogenicity of such episodes and the difficult but mandatory need for external validation of such tools. Beyond this, their application and value in clinical practice remain to be definitively demonstrated in both biopsy avoidance and prevention of clinical rejection episodes. Their combination with other biomarkers, either epidemiological or biological, could contribute to a more accurate picture of a patient's risk of rejection and guide clinicians in the follow-up of kidney transplant recipients.

Optimizing the approach to monitoring allograft inflammation using serial urinary CXCL10/creatinine testing in pediatric kidney transplant recipients

BACKGROUND

Urinary CXCL10/creatinine (uCXCL10/Cr) is proposed as an effective biomarker of subclinical rejection in pediatric kidney transplant recipients. This study objective was to model implementation in the clinical setting.

METHODS

Banked urine samples at a single center were tested for uCXCL10/Cr to validate published thresholds for rejection diagnosis (>80% specificity). The positive predictive value (PPV) for rejection diagnosis for uCXCL10/Cr-indicated biopsy was modeled with first-positive versus two-test-positive approaches, with accounting for changes associated with urinary tract infection (UTI), BK and CMV viremia, and subsequent recovery.

RESULTS

Seventy patients aged 10.5 ± 5.6 years at transplant (60% male) had n = 726 urine samples with n = 236 associated biopsies (no rejection = 167, borderline = 51, and Banff 1A = 18). A threshold of 12 ng/mmol was validated for Banff 1A versus no-rejection diagnosis (AUC = 0.74, 95% CI = 0.57-0.92). The first-positive test approach (n = 69) did not resolve a clinical diagnosis in 38 cases (55%), whereas the two-test approach resolved a clinical diagnosis in the majority as BK (n = 17/60, 28%), CMV (n = 4/60, 7%), UTI (n = 8/60, 13%), clinical rejection (n = 5/60, 8%), and transient elevation (n = 18, 30%). In those without a resolved clinical diagnosis, PPV from biopsy for subclinical rejection is 24% and 71% (p = .017), for first-test versus two-test models, respectively. After rejection treatment, uCXCL10/Cr level changes were all concordant with change in it-score. Sustained uCXCL10/Cr after CMV and BK viremia resolution was associated with later acute rejection.

CONCLUSIONS

Urinary CXCL10/Cr reliably identifies kidney allograft inflammation. These data support a two-test approach to reliably exclude other clinically identifiable sources of inflammation, for kidney biopsy indication to rule out subclinical rejection.

European Survey on Clinical Practice of Detecting and Treating T-Cell Mediated Kidney Transplant Rejection

The KDIGO guideline for acute rejection treatment recommends use of corticosteroids and suggests using lymphocyte-depleting agents as second line treatment. Aim of the study was to determine the current practices of detection and treatment of TCMR of kidney allografts amongst European kidney transplant centres. An invitation was sent through ESOT/EKITA newsletters and through social media to transplant professionals in Europe for taking part in the survey. A total of 129 transplant professionals responded to the survey. There was equal representation of small and large sized transplant centres. The majority of centres treat borderline changes (BL) and TCMR (Grade IA-B, IIA-B) in indication biopsies and protocol biopsies with corticosteroids as first line treatment. Thymoglobulin is used mainly as second line treatment for TCMR Grade IA-B (80%) and TCMR IIA-B (85%). Treatment success is most often evaluated within one month of therapy. There were no differences observed between the large and small centres for the management of TCMR. This survey highlights the common practices and diversity in clinics for the management of TCMR in Europe. Testing new therapies for TCMR should be in comparison to the current standard of care in Europe. Better consensus on treatment success is crucial for robust study designs.

Prediction of very early subclinical rejection with machine learning in kidney transplantation

Protocol biopsy is a reliable method for assessing allografts status after kidney transplantation (KT). However, due to the risk of complications, it is necessary to establish indications and selectively perform protocol biopsies by classifying the high-risk group for early subclinical rejection (SCR). Therefore, the purpose of this study is to analyze the incidence and risk factors of early SCR (within 2 weeks) and develop a prediction model using machine learning. Patients who underwent KT at Samsung Medical Center from January 2005 to December 2020 were investigated. The incidence of SCR was investigated and risk factors were analyzed. For the development of prediction model, machine learning methods (random forest, elastic net, extreme gradient boosting [XGB]) and logistic regression were used and the performance between the models was evaluated. The cohorts of 987 patients were reviewed and analyzed. The incidence of SCR was 14.6%. Borderline cellular rejection (BCR) was the most common type of rejection, accounting for 61.8% of cases. In the analysis of risk factors, recipient age (OR 0.98, p = 0.03), donor BMI (OR 1.07, p = 0.02), ABO incompatibility (OR 0.15, p < 0.001), HLA II mismatch (two [OR 6.44, p < 0.001]), and ATG induction (OR 0.41, p < 0.001) were associated with SCR in the multivariate analysis. The logistic regression prediction model (average AUC = 0.717) and the elastic net model (average AUC = 0.712) demonstrated good performance. HLA II mismatch and induction type were consistently identified as important variables in all models. The odds ratio analysis of the logistic prediction model revealed that HLA II mismatch (OR 6.77) was a risk factor for SCR, while ATG induction (OR 0.37) was a favorable factor. Early SCR was associated with HLA II mismatches and induction agent and prediction model using machine learning demonstrates the potential to predict SCR.

Immune monitoring of prevalent kidney transplant recipients using Torque Teno Virus: Protocol for a single-centre prospective cohort study

INTRODUCTION

Kidney transplant recipients (KTRs) suffer from immunosuppression-related adverse events (iRAEs), such as infections and malignancy from chronic immunosuppression, but are also at risk of graft loss from rejection with underimmunosuppression. Biomarkers that predict both iRAEs and rejection while allowing individualisation of immunosuppression exposure are lacking. Although plasma viral DNA levels of torque teno virus (TTV), a widely prevalent, non-pathogenic virus, have been shown to predict both iRAE and rejection in newly transplanted KTRs within the first year after transplant, its role for prevalent KTRs on stable immunosuppression is less clear.This study aims to determine the prognostic value of TTV levels for severe infections (defined as infections requiring hospitalisation) in prevalent KTRs on stable immunosuppression for at least 3 months and compare it against that of other commonly available biomarkers. The study also aims to explore the relationship between TTV levels and factors affecting the 'net state of immunosuppression' as well as other clinical outcomes.

METHODS AND ANALYSIS

This is a single-centre, prospective, observational cohort study of 172 KTRs on stable immunosuppression for more than 3 months. TTV levels will be measured using the TTV R-GENE kit upon recruitment when study subjects are admitted and when kidney allograft biopsies are performed. Subjects will be monitored for iRAEs and rejection for at least 12 months. The relationship between TTV load and clinical outcomes such as severe infections will be analysed and compared against that from other common biomarkers and previously published predictive scores.

ETHICS AND DISSEMINATION

The study was approved by the SingHealth Centralised Institutional Review Board (2023/2170). The results will be presented at conferences and submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT05836636.

The Clinical Utility of Post-Transplant Monitoring of Donor-Specific Antibodies in Stable Renal Transplant Recipients: A Consensus Report With Guideline Statements for Clinical Practice

Solid phase immunoassays improved the detection and determination of the antigen-specificity of donor-specific antibodies (DSA) to human leukocyte antigens (HLA). The widespread use of SPI in kidney transplantation also introduced new clinical dilemmas, such as whether patients should be monitored for DSA pre- or post-transplantation. Pretransplant screening through SPI has become standard practice and DSA are readily determined in case of suspected rejection. However, DSA monitoring in recipients with stable graft function has not been universally established as standard of care. This may be related to uncertainty regarding the clinical utility of DSA monitoring as a screening tool. This consensus report aims to appraise the clinical utility of DSA monitoring in recipients without overt signs of graft dysfunction, using the Wilson & Junger criteria for assessing the validity of a screening practice. To assess the evidence on DSA monitoring, the European Society for Organ Transplantation (ESOT) convened a dedicated workgroup, comprised of experts in transplantation nephrology and immunology, to review relevant literature. Guidelines and statements were developed during a consensus conference by Delphi methodology that took place in person in November 2022 in Prague. The findings and recommendations of the workgroup on subclinical DSA monitoring are presented in this article.

Progress in Pathological Diagnosis after Kidney Transplantation: Current Trend and Future Perspective

Advances in immunosuppressive therapy; posttransplant management of allograft rejection; and measures against infectious diseases, cardiovascular diseases, and malignancy dramatically improved graft and patient survival after kidney transplantation (KT). Among them, kidney allograft biopsy is an important tool and the gold standard for the diagnosis of various kidney allograft injuries, including allograft rejection, virus-induced nephropathy, calcineurin inhibitor toxicity, and posttransplant glomerular diseases. The Banff Conference on Allograft Pathology has contributed to establishing the diagnostic criteria for kidney allograft rejection and polyomavirus-associated nephropathy that are used as a common standard worldwide. In addition to the for-cause biopsy, many transplant centers perform protocol biopsies in the early and late posttransplant periods to detect and treat allograft injury earlier. Preimplantation biopsy in deceased-donor KT has also been performed, especially in the marginal donor, and attempts have been made to predict the prognosis in combination with clinical information and the renal resistance of hypothermic machine perfusion. Regarding the preimplantation biopsy from a living kidney donor, it can provide useful information on aging and/or early changes in lifestyle diseases, such as glomerulosclerosis, tubulointerstitial changes, and arterial and arteriolar sclerosis, and be used as a reference for the subsequent management of living donors. In this review, morphologic features of important kidney allograft pathology, such as allograft rejection and polyomavirus-associated nephropathy, according to the latest Banff classification and additional information derived from protocol biopsy, and future perspectives with recently developed technologies are discussed.

The Histological Spectrum and Clinical Significance of T Cell-mediated Rejection of Kidney Allografts

T cell-mediated rejection (TCMR) remains a significant cause of long-term kidney allograft loss, either indirectly through induction of donor-specific anti-HLA alloantibodies or directly through chronic active TCMR. Whether found by indication or protocol biopsy, Banff defined acute TCMR should be treated with antirejection therapy and maximized maintenance immunosuppression. Neither isolated interstitial inflammation in the absence of tubulitis nor isolated tubulitis in the absence of interstitial inflammation results in adverse outcomes, and neither requires antirejection treatment. RNA gene expression analysis of biopsy material may supplement conventional histology, especially in ambiguous cases. Lesser degrees of tubular and interstitial inflammation (Banff borderline) may portend adverse outcomes and should be treated when found on an indication biopsy. Borderline lesions on protocol biopsies may resolve spontaneously but require close follow-up if untreated. Following antirejection therapy of acute TCMR, surveillance protocol biopsies should be considered. Minimally invasive blood-borne assays (donor-derived cell-free DNA and gene expression profiling) are being increasingly studied as a means of following stable patients in lieu of biopsy. The clinical benefit and cost-effectiveness require confirmation in randomized controlled trials. Treatment of acute TCMR is not standardized but involves bolus corticosteroids with lymphocyte depleting antibodies for severe, refractory, or relapsing cases. Arteritis may be found with acute TCMR, active antibody-mediated rejection, or mixed rejections and should be treated accordingly. The optimal treatment ofchronic active TCMR is uncertain. Randomized controlled trials are necessary to optimally define therapy.

Treatment of early borderline lesions in low immunological risk kidney transplant patients: a Spanish multicenter, randomized, controlled parallel-group study protocol: the TRAINING study

Background

Subclinical inflammation, including borderline lesions (BL), is very common (30–40%) after kidney transplantation (KT), even in low immunological risk patients, and can lead to interstitial fibrosis/tubular atrophy (IFTA) and worsening of renal function with graft loss. Few controlled studies have analyzed the therapeutic benefit of treating these BL on renal function and graft histology. Furthermore, these studies have only used bolus steroids, which may be insufficient to slow the progression of these lesions. Klotho, a transmembrane protein produced mainly in the kidney with antifibrotic properties, plays a crucial role in the senescence-inflammation binomial of kidney tissue. Systemic and local inflammation decrease renal tissue expression and soluble levels of α-klotho. It is therefore important to determine whether treatment of BL prevents a decrease in α-klotho levels, progression of IFTA, and loss of kidney function.

Methods

The TRAINING study will randomize 80 patients with low immunological risk who will receive their first KT. The aim of the study is to determine whether the treatment of early BL (3rd month post-KT) with polyclonal rabbit antithymocyte globulin (Grafalon®) (6 mg/kg/day) prevents or decreases the progression of IFTA and the worsening of graft function compared to conventional therapy after two years post-KT, as well as to analyze whether treatment of BL with Grafalon® can modify the expression and levels of klotho, as well as the pro-inflammatory cytokines that regulate its expression.

Discussion

This phase IV investigator-driven, randomized, placebo-controlled clinical trial will examine the efficacy and safety of Grafalon® treatment in low-immunological-risk KT patients with early BL.

Trial registration

clinicaltrials.gov: NCT04936282. Registered June 23, 2021, https://clinicaltrials.gov/ct2/show/NCT04936282?term=NCT04936282&draw=2&rank=1. Protocol Version 2 of 21 January 2022. Sponsor: Canary Isles Institute for Health Research Foundation, Canary Isles (FIISC). mgomez@fciisc.org.

Complications of Percutaneous Kidney Allograft Biopsy: Systematic Review and Meta-analysis

BACKGROUND

Kidney biopsy is important to guide the management of allograft dysfunction but has a risk of complications. This review aimed to determine the incidence and risk factors of complications after kidney allograft biopsy.

METHODS

This is a systematic review and meta-analysis of randomized controlled trials, cohort studies, or case-control studies indexed on PubMed, Embase, Cochrane Central Register of Controlled Trials, World Health Organization International Clinical Trials Registry, and ClinicalTrials.gov, limited to the English language, from January 2000 to December 2020, including adult and pediatric kidney allograft biopsies. Primary outcomes were gross hematuria, bleeding requiring transfusion, and major complications (requiring interventions such as blood transfusion or surgical or radiological interventions).

RESULTS

The review included 72 studies (40 082 biopsies). The quality of included studies was suboptimal. Pooled rates of gross hematuria, bleeding requiring transfusion, and major complications were 3.18% [95% confidence interval (95% CI), 2.31-4.19], 0.31% (95% CI, 0.15-0.52) and 0.89% (95% CI, 0.61-1.22), respectively. Gross hematuria rates were lower in high-income compared with middle-income countries (2.59% versus 6.44%, P < 0.01) and biopsies performed by radiology as compared with nephrology departments (1.25% versus 3.71%, P < 0.01). Blood transfusion rates were lower in pediatrics than adults (0.0% versus 0.65%, P < 0.01). Major complications were lower in biopsies performed by specialists as compared with trainees (0.02% versus 3.64%, P < 0.01). Graft loss and mortality were extremely rare. Limitations included missing data, few randomized controlled trials, and possible publication bias.

CONCLUSIONS

The risk of complications after kidney allograft biopsy was low. Given the low quality of included studies, risk factors for complications should be further examined in future studies.

Proposed Definitions of T Cell-Mediated Rejection and Tubulointerstitial Inflammation as Clinical Trial Endpoints in Kidney Transplantation

The diagnosis of acute T cell-mediated rejection (aTCMR) after kidney transplantation has considerable relevance for research purposes. Its definition is primarily based on tubulointerstitial inflammation and has changed little over time; aTCMR is therefore a suitable parameter for longitudinal data comparisons. In addition, because aTCMR is managed with antirejection therapies that carry additional risks, anxieties, and costs, it is a clinically meaningful endpoint for studies. This paper reviews the history and classifications of TCMR and characterizes its potential role in clinical trials: a role that largely depends on the nature of the biopsy taken (indication vs protocol), the level of inflammation observed (e.g., borderline changes vs full TCMR), concomitant chronic lesions (chronic active TCMR), and the therapeutic intervention planned. There is ongoing variability—and ambiguity—in clinical monitoring and management of TCMR. More research, to investigate the clinical relevance of borderline changes (especially in protocol biopsies) and effective therapeutic strategies that improve graft survival rates with minimal patient morbidity, is urgently required. The present paper was developed from documentation produced by the European Society for Organ Transplantation (ESOT) as part of a Broad Scientific Advice request that ESOT submitted to the European Medicines Agency for discussion in 2020. This paper proposes to move toward refined definitions of aTCMR and borderline changes to be included as primary endpoints in clinical trials of kidney transplantation.

Preliminary Investigation of the Biomarkers of Acute Renal Transplant Rejection Using Integrated Proteomics Studies, Gene Expression Omnibus Datasets, and RNA Sequencing

A kidney transplant is often the best treatment for end-stage renal disease. Although immunosuppressive therapy sharply reduces the occurrence of acute allograft rejection (AR), it remains the main cause of allograft dysfunction. We aimed to identify effective biomarkers for AR instead of invasive kidney transplant biopsy. We integrated the results of several proteomics studies related to AR and utilized public data sources. Gene ontology (GO) and pathway analyses were used to identify important biological processes and pathways. The performance of the identified proteins was validated using several public gene expression omnibus (GEO) datasets. Samples that performed well were selected for further validation through RNA sequencing of peripheral blood mononuclear cells of patients with AR (n = 16) and non-rejection (n = 19) from our medical center. A total of 25 differentially expressed proteins (DEPs) overlapped in proteomic studies of urine and blood samples. GO analysis showed that the DEPs were mainly involved in the immune system and blood coagulation. Pathway analysis showed that the complement and coagulation cascade pathways were well enriched. We found that immunoglobulin heavy constant alpha 1 (IGHA1) and immunoglobulin κ constant (IGKC) showed good performance in distinguishing AR from non-rejection groups validated with several GEO datasets. Through RNA sequencing, the combination of IGHA1, IGKC, glomerular filtration rate, and donor age showed good performance in the diagnosis of AR with ROC AUC 91.4% (95% CI: 82–100%). Our findings may contribute to the discovery of potential biomarkers for AR monitoring.

Effects of antirejection therapies for early subclinical acute rejection in renal transplant protocol biopsies

Background

Although recently strengthened immunosuppression protocols have decreased the incidence of clinical acute rejection of renal transplants, subclinical acute rejection and borderline changes remain problematic. This study was performed to evaluate the effects of antirejection therapies for early subclinical acute rejection and borderline changes.

Methods

In total, 269 renal transplant patients who received 3-month and 1-year protocol biopsies after renal transplantation were enrolled this study and divided into those with normal findings (Group A) and those with ≥ borderline changes (Group B) according to the 3-month pathological results. Pathological changes, graft function, and graft survival were evaluated at 1 year.

Results

The 3-month protocol biopsy revealed normal findings in 166 patients (Group A) and borderline changes and subclinical acute rejection in 103 patients (Group B). In Group A, 65.1% (n = 108) of the patients maintained normal findings at 1 year, while 30.1% (n = 50) deteriorated to ≥ borderline changes. In Group B, 52.4% (n = 54) of patients improved to normal. Among patients with subclinical acute rejection, 25.0% (n = 5) maintained subclinical acute rejection at 1 year despite antirejection therapy. The mean estimated glomerular filtration rate decreased from 60.4 ± 24.5 to 58.3 ± 19.0 mL/min/1.73 m2 in Group A and from 57.2 ± 28.2 to 53.7 ± 20.3 mL/min/1.73 m2 in Group B (p = 0.417). The 3-, 5-, and 7-year graft survival rates were 99.4%, 99.4%, and 97.6% in Group A and 100.0%, 98.6%, and 98.6% in Group B, respectively (p = 0.709).

Conclusions

Subclinical acute rejection is likely to recur. However, intervention for subclinical acute rejection in the early period after transplantation may help to prevent subsequent histological changes.

Effectiveness of T cell-mediated rejection therapy: A systematic review and meta-analysis

The effectiveness of T cell-mediated rejection (TCMR) therapy for achieving histological remission remains undefined in patients on modern immunosuppression. We systematically identified, critically appraised, and summarized the incidence and histological outcomes after TCMR treatment in patients on tacrolimus (Tac) and mycophenolic acid (MPA). English-language publications were searched in MEDLINE (Ovid), Embase (Ovid), Cochrane Central (Ovid), CINAHL (EBSCO), and Clinicaltrials.gov (NLM) up to January 2021. Study quality was assessed with the National Institutes of Health Study Quality Tool. We pooled results using an inverse variance, random-effects model and report the binomial proportions with associated 95% confidence intervals (95% CI). Statistical heterogeneity was explored using the I²  statistic. From 2875 screened citations, we included 12 studies (1255 participants). Fifty-eight percent were good/high quality while the rest were moderate quality. Thirty-nine percent of patients (95% CI 0.26-0.53, I² 77%) had persistent ≥Banff Borderline TCMR 2-9 months after anti-rejection therapy. Pulse steroids and augmented maintenance immunosuppression were mainstays of therapy, but considerable practice heterogeneity was present. A high proportion of biopsy-proven rejection exists after treatment emphasizing the importance of histology to characterize remission. Anti-rejection therapy is foundational to transplant management but well-designed clinical trials in patients on Tac/MPA immunosuppression are lacking to define the optimal therapeutic approach.

Two-Week Protocol Biopsy in Renal Allograft: Feasibility, Safety, and Outcomes

Background: Protocol biopsy in renal allograft helps to early detect subclinical rejection (SCR) in patients who have no abnormal clinical and laboratory findings. Still, there are rare reports about the techniques and outcomes of two-week protocol biopsy. The aim of this study was to assess two-week protocol biopsy regarding the technical feasibility, procedure safety, and clinical outcomes. Methods: A total of 894 protocol biopsies were performed in adult recipients between 2012 and 2019. Two-week and one-year protocol biopsies were guided with ultrasound in 842 and 399 patients by one of four radiologists with wide range of biopsy experience, respectively. These protocol biopsies were compared in terms of feasibility and safety. Standard references were clinico-laboratory findings and biopsy examinations. Results: The median period of two-week and one-year protocol biopsies were 12 days (10–20 days) and 383 days (302–420 days), respectively. All protocol biopsies were technically successful and there was no difference between radiologists regarding technical success and complications (p = 0.453). Major complication (Clavien–Dindo grading II–IV) rates of two-week and one-year protocol biopsies were 0.3% (3/842) and 0.2% (1/399), respectively (p = 1.000). However, univariate analysis demonstrated that platelet count < 100 K/mL and blood urea nitrogen ≥ 40 mg/dL were associated with major complications in two-week protocol biopsy. The SCRs of these protocol biopsies were 15.4% (130/842) and 33.6% (134/399), respectively (p < 0.001). Conclusion: Two-week protocol biopsy is technically feasible and safe. It contributes to early detecting a substantial number of SCRs. Prior to the biopsy, platelet count and blood urea nitrogen should be carefully checked to predict major complications.

Pre-transplant Transcriptional Signature in Peripheral Blood Mononuclear Cells of Acute Renal Allograft Rejection

Acute rejection (AR) is closely associated with renal allograft dysfunction. Here, we utilised RNA sequencing (RNA-Seq) and bioinformatic methods to characterise the peripheral blood mononuclear cells (PBMCs) of patients with acute renal allograft rejection. Pretransplant blood samples were collected from 32 kidney allograft donors and 42 corresponding recipients with biopsies classified as T cell-mediated rejection (TCMR, n = 18), antibody-mediated rejection (ABMR, n = 5), and normal/non-specific changes (non-AR, n = 19). The patients with TCMR and ABMR were assigned to the AR group, and the patients with normal/non-specific changes (n = 19) were assigned to the non-AR group. We analysed RNA-Seq data for identifying differentially expressed genes (DEGs), and then gene ontology (GO) analysis, Reactome, and ingenuity pathway analysis (IPA), protein—protein interaction (PPI) network, and cell-type enrichment analysis were utilised for bioinformatics analysis. We identified DEGs in the PBMCs of the non-AR group when compared with the AR, ABMR, and TCMR groups. Pathway and GO analysis showed significant inflammatory responses, complement activation, interleukin-10 (IL-10) signalling pathways, classical antibody-mediated complement activation pathways, etc., which were significantly enriched in the DEGs. PPI analysis showed that IL-10, VEGFA, CXCL8, MMP9, and several histone-related genes were the hub genes with the highest degree scores. Moreover, IPA analysis showed that several proinflammatory pathways were upregulated, whereas antiinflammatory pathways were downregulated. The combination of NFSF14+TANK+ANKRD 33 B +HSPA1B was able to discriminate between AR and non-AR with an AUC of 92.3% (95% CI 82.8–100). Characterisation of PBMCs by RNA-Seq and bioinformatics analysis demonstrated gene signatures and biological pathways associated with AR. Our study may provide the foundation for the discovery of biomarkers and an in-depth understanding of acute renal allograft rejection.

Chronic Allograft Injury

With the incremental improvements in long-term kidney transplant survival, there is renewed focus on what causes failure of the transplanted allograft. Over the past decade, our understanding of the injuries that lead to loss of graft function over time has evolved. Chronic allograft injury includes both immune-mediated and nonimmune-mediated injuries, which may involve the organ donor, the recipient, or both. The targets of injury include the kidney tubular epithelium, the endothelium, and the glomerulus. As a response to injury, there are the expected tissue remodeling and repair processes. However, if inflammation persists, which is not uncommon in the transplant setting, the resulting maladaptive response is matrix deposition and/or fibrosis. This ultimately leads to declining graft function and, finally, failure. With our advancing knowledge of the multiple etiologies and mechanisms, enhanced by more recent cohort studies in humans, there is an opportunity to identify those at greater risk to initiate new strategies to ameliorate the process. Although the most recent studies focus on immune-mediated injuries, there is a critical need to identify both markers of injury and mechanisms of injury. In this review, we highlight the findings of recent studies, highlight the potential therapeutic targets, and identify the continued unmet need for understanding the mechanisms of late graft failure.

Combining Blood Gene Expression and Cellfree DNA to Diagnose Subclinical Rejection in Kidney Transplant Recipients

BACKGROUND AND OBJECTIVES

Subclinical acute rejection is associated with poor outcomes in kidney transplant recipients. As an alternative to surveillance biopsies, noninvasive screening has been established with a blood gene expression profile. Donor-derived cellfree DNA (cfDNA) has been used to detect rejection in patients with allograft dysfunction but not tested extensively in stable patients. We hypothesized that we could complement noninvasive diagnostic performance for subclinical rejection by combining a donor-derived cfDNA and a gene expression profile assay.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We performed a post hoc analysis of simultaneous blood gene expression profile and donor-derived cfDNA assays in 428 samples paired with surveillance biopsies from 208 subjects enrolled in an observational clinical trial (Clinical Trials in Organ Transplantation-08). Assay results were analyzed as binary variables, and then, their continuous scores were combined using logistic regression. The performance of each assay alone and in combination was compared.

RESULTS

For diagnosing subclinical rejection, the gene expression profile demonstrated a negative predictive value of 82%, a positive predictive value of 47%, a balanced accuracy of 64%, and an area under the receiver operating curve of 0.75. The donor-derived cfDNA assay showed similar negative predictive value (84%), positive predictive value (56%), balanced accuracy (68%), and area under the receiver operating curve (0.72). When both assays were negative, negative predictive value increased to 88%. When both assays were positive, positive predictive value increased to 81%. Combining assays using multivariable logistic regression, area under the receiver operating curve was 0.81, significantly higher than the gene expression profile (P<0.001) or donor-derived cfDNA alone (P=0.006). Notably, when cases were separated on the basis of rejection type, the gene expression profile was significantly better at detecting cellular rejection (area under the receiver operating curve, 0.80 versus 0.62; P=0.001), whereas the donor-derived cfDNA was significantly better at detecting antibody-mediated rejection (area under the receiver operating curve, 0.84 versus 0.71; P=0.003).

CONCLUSIONS

A combination of blood-based biomarkers can improve detection and provide less invasive monitoring for subclinical rejection. In this study, the gene expression profile detected more cellular rejection, whereas donor-derived cfDNA detected more antibody-mediated rejection.

Protocol Biopsies on de novo Renal-Transplants at 3 Months after Surgery: Impact on 5-Year Transplant Survival

Background: In many centers, a protocol kidney biopsy (PKB) is performed at 3 months post-transplantation (M3), without a demonstrated benefit on death-censored graft survival (DCGS). In this study, we compared DCGS between kidney transplant recipients undergoing a PKB or without such biopsy while accounting for the obvious indication bias. Methods: In this retrospective, single-center study conducted between 2007 and 2013, we compared DCGS with respect to the availability and features of a PKB. We built a propensity score (PS) to account for PKB indication likelihood and adjusted the DCGS analysis on PKB availability and the PS. Results: A total of 615 patients were included: 333 had a PKB, 282 did not. In bivariate Kaplan–Meier survival analysis, adjusting for the availability of a PKB and for the PS, a PKB was associated with a better 5-year DCGS independently of the PS (p < 0.001). Among the PKB+ patients, 87 recipients (26%) had IF/TA > 0. Patients with an IF/TA score of 3 had the worst survival. A total of 144 patients (44%) showed cv lesions. Patients with cv2 and cv3 lesions had the worst 5-year DCGS. Conclusions: A M3 PKB was associated with improved graft survival independently of potential confounders. These results could be explained by the early treatment of subclinical immunological events. It could be due to better management of the immunosuppressive regimen.

Transitional B cell cytokines predict renal allograft outcomes

Early immunological biomarkers that predict rejection and chronic allograft loss are needed to inform preemptive therapy and improve long-term outcomes. Here, we prospectively examined the ratio of interleukin-10 (IL-10) to tumor necrosis factor-α (TNFα) produced by transitional-1 B cells (T1B) 3 months after transplantation as a predictive biomarker for clinical and subclinical renal allograft rejection and subsequent clinical course. In both Training (n = 162) and Internal Validation (n = 82) Sets, the T1B IL-10/TNFα ratio 3 months after transplantation predicted both clinical and subclinical rejection anytime in the first year. The biomarker also predicted subsequent late rejection with a lead time averaging 8 months. Among biomarker high-risk patients, 60% had early rejection, of which 48% recurred later in the first posttransplant year. Among high-risk patients without early rejection, 74% developed rejection later in the first year. In contrast, only 5% of low-risk patients had early and 5% late rejection. The biomarker also predicted rejection in an External Validation Set (n = 95) and in key patient subgroups, confirming generalizability. Biomarker high-risk patients exhibited progressively worse renal function and decreased 5-year graft survival compared to low-risk patients. Treatment of B cells with anti-TNFα in vitro augmented the IL-10/TNFα ratio, restored regulatory activity, and inhibited plasmablast differentiation. To conclude, the T1B IL-10/TNFα ratio was validated as a strong predictive biomarker of renal allograft outcomes and provides a rationale for preemptive therapeutic intervention with TNF blockade.

Biomarker implementation: Evaluation of the decision-making impact of CXCL10 testing in a pediatric cohort

BACKGROUND

Children are at high risk for subclinical rejection, and kidney biopsy is currently used for surveillance. Our objective was to test how novel rejection biomarkers such as urinary CXCL10 may influence clinical decision-making to indicate need for a biopsy.

METHODS

A minimum dataset for standard decision-making to indicate a biopsy was established by an expert panel and used to design clinical vignettes for use in a survey. Pediatric nephrologists were recruited to review the vignettes and A) estimate rejection risk and B) decide whether to biopsy; first without and then with urinary CXCL10/Cr level. Accuracy of biopsy decisions was then tested against the biopsy results. IRA was assessed by Fleiss Kappa (κ) for binary choice and ICC for probabilities.

RESULTS

Eleven pediatric nephrologists reviewed 15 vignettes each. ICC of probability assessment for rejection improved from poor (0.28, P < .01) to fair (0.48, P < .01) with addition of CXCL10/Cr data. It did not, however, improve the IRA for decision to biopsy (K = 0.48 and K = 0.43, for the comparison). Change in clinician estimated probability of rejection with additional CXCL10/Cr data was correlated with CXCL10/Cr level (r²  = 0.7756, P < .0001). Decision accuracy went from 8/15 (53.3%) cases to 11/15 (73.3%) with CXCL10/Cr, although improvement did not achieve statistical significance. Using CXCL10/Cr alone would have been accurate in 12/15 cases (80%).

CONCLUSION

There is high variability in decision-making on biopsy indication. Urinary CXCL10/Cr improves probability estimates for risk of rejection. Training may be needed to assist nephrologists in better integrate biomarker information into clinical decision-making.

Validity and utility of urinary CXCL10/Cr immune monitoring in pediatric kidney transplant recipients

Individualized posttransplant immunosuppression is hampered by suboptimal monitoring strategies. To validate the utility of urinary CXCL10/Cr immune monitoring in children, we conducted a multicenter prospective observational study in children <21 years with serial and biopsy-associated urine samples (n = 97). Biopsies (n = 240) were categorized as normal (NOR), rejection (>i1t1; REJ), indeterminate (IND), BKV infection, and leukocyturia (LEU). An independent pediatric cohort of 180 urines was used for external validation. Ninety-seven patients aged 11.4 ± 5.5 years showed elevated urinary CXCL10/Cr in REJ (3.1, IQR 1.1, 16.4; P < .001) and BKV nephropathy (median = 5.6, IQR 1.3, 26.9; P < .001) vs. NOR (0.8, IQR 0.4, 1.5). The AUC for REJ vs. NOR was 0.76 (95% CI 0.66-0.86). Low (0.63) and high (4.08) CXCL10/Cr levels defined high sensitivity and specificity thresholds, respectively; validated against an independent sample set (AUC = 0.76, 95% CI 0.66-0.86). Serial urines anticipated REJ up to 4 weeks prior to biopsy and declined within 1 month following treatment. Elevated mean CXCL10/Cr was correlated with first-year eGFR decline (ρ = -0.37, P ≤ .001), particularly when persistently exceeding ≥4.08 (ratio = 0.81; P < .04). Useful thresholds for urinary CXCL10/Cr levels reproducibly define the risk of rejection, immune quiescence, and decline in allograft function for use in real-time clinical monitoring in children.

Economic analysis of screening for subclinical rejection in kidney transplantation using protocol biopsies and noninvasive biomarkers

Subclinical rejection (SCR) screening in kidney transplantation (KT) using protocol biopsies and noninvasive biomarkers has not been evaluated from an economic perspective. We assessed cost-effectiveness from the health sector perspective of SCR screening in the first year after KT using a Markov model that compared no screening with screening using protocol biopsy or biomarker at 3 months, 12 months, 3 and 12 months, or 3, 6, and 12 months. We used 12% subclinical cellular rejection and 3% subclinical antibody-mediated rejection (SC-ABMR) for the base-case cohort. Results favored 1-time screening at peak SCR incidence rather than repeated screening. Screening 2 or 3 times was favored only with age <35 years and with high SC-ABMR incidence. Compared to biomarkers, protocol biopsy yielded more quality-adjusted life years (QALYs) at lower cost. A 12-month biopsy cost $13 318/QALY for the base-case cohort. Screening for cellular rejection in the absence of SC-ABMR was less cost effective with 12-month biopsy costing $46 370/QALY. Screening was less cost effective in patients >60 years. Using biomarker twice or thrice was cost effective only if biomarker cost was <$700. In conclusion, in KT, screening for SCR more than once during the first year is not economically reasonable. Screening with protocol biopsy was favored over biomarkers.

Masked acute rejection of the graft kidney under the recovery of native kidneys in a patient who underwent simultaneous liver and kidney transplantation

INTRODUCTION

Simultaneous liver and kidney transplantation is a life-saving procedure for patients with liver failure and irreversible renal dysfunction. However, some studies have reported the recovery of native renal function after simultaneous liver and kidney transplantation.

CASE PRESENTATION

A 33-year-old woman initially underwent living-donor liver transplantation for liver failure. When graft liver failure developed, she also sustained acute renal failure and required continuous hemodiafiltration for 6 weeks. Simultaneous liver and kidney transplantation from a brain-dead donor recovered her liver and renal function. A 1-year protocol graft kidney biopsy revealed acute cellular rejection despite stable serum creatinine levels. Renal scintigraphy showed functional native kidneys masking acute rejection of the graft kidney. The rejection was improved by pulse steroid therapy.

CONCLUSION

Acute rejection of the graft kidney may silently progress due to recovery of the native kidney function after simultaneous liver and kidney transplantation. Renal scintigraphy and graft kidney biopsy should be considered even if blood tests indicate stable total renal function.

Activity-based protein profiling guided identification of urine proteinase 3 activity in subclinical rejection after renal transplantation

Background

The pathophysiology of subclinical versus clinical rejection remains incompletely understood given their equivalent histological severity but discordant graft function. The goal was to evaluate serine hydrolase enzyme activities to explore if there were any underlying differences in activities during subclinical versus clinical rejection.

Methods

Serine hydrolase activity-based protein profiling (ABPP) was performed on the urines of a case control cohort of patients with biopsy confirmed subclinical or clinical transplant rejection. In-gel analysis and affinity purification with mass spectrometry were used to demonstrate and identify active serine hydrolase activity. An assay for proteinase 3 (PR3/PRTN3) was adapted for the quantitation of activity in urine.

Results

In-gel ABPP profiles suggested increased intensity and diversity of serine hydrolase activities in urine from patients undergoing subclinical versus clinical rejection. Serine hydrolases (n = 30) were identified by mass spectrometry in subclinical and clinical rejection patients with 4 non-overlapping candidates between the two groups (i.e. ABHD14B, LTF, PR3/PRTN3 and PRSS12). Western blot and the use of a specific inhibitor confirmed the presence of active PR3/PRTN3 in samples from patients undergoing subclinical rejection. Analysis of samples from normal donors or from several serial post-transplant urines indicated that although PR3/PRTN3 activity may be highly associated with low-grade subclinical inflammation, the enzyme activity was not restricted to this patient group.

Conclusions

There appear to be limited qualitative and quantitative differences in serine hydrolase activity in patients with subclinical versus clinical renal transplant rejection. The majority of enzymes identified were present in samples from both groups implying that in-gel quantitative differences may largely relate to the activity status of shared enzymes. However qualitative compositional differences were also observed indicating differential activities. The PR3/PRTN3 analyses indicate that the activity status of urine in transplant patients is dynamic possibly reflecting changes in the underlying processes in the transplant. These data suggest that differential serine hydrolase pathways may be active in subclinical versus clinical rejection which requires further exploration in larger patient cohorts. Although this study focused on PR3/PRTN3, this does not preclude the possibility that other enzymes may play critical roles in the rejection process.

Subclinical Inflammation in Renal Transplantation

The standardization of renal allograft pathology began in 1991 at the first Banff Conference held in Banff, Alberta, Canada. The first task of transplant pathologists, clinicians, and surgeons was to establish diagnostic criteria for T-cell-mediated rejection (TCMR). The histological threshold for this diagnosis was arbitrarily set at "i2t2": a mononuclear interstitial cell infiltrate present in at least 25% of normal parenchyma and >4 mononuclear cells within the tubular basement membrane of nonatrophic tubules. TCMR was usually found in dysfunctional grafts with an elevation in the serum creatinine; however, our group and others found this extent of inflammation in "routine" or "protocol" biopsies of normally functioning grafts: "subclinical" TCMR. The prevalence of TCMR is higher in the early months posttransplant and has decreased with the increased potency of current immunosuppressive agents. However, the pathogenicity of lesser degrees of inflammation under modern immunosuppression and the relation between ongoing inflammation and development of donor-specific antibody has renewed our interest in subclinical alloreactivity. Finally, the advances in our understanding of pretransplant risk assessment, and our increasing ability to monitor patients less invasively posttransplant, promises to usher in the era of precision medicine.

Diagnostic yield of 18 F-FDG PET/CT imaging and urinary CXCL9/creatinine levels in kidney allograft subclinical rejection

Subclinical kidney allograft acute rejection (SCR) corresponds to "the unexpected histological evidence of acute rejection in a stable patient." SCR detection relies on surveillance biopsy. Noninvasive approaches may help avoid biopsy-associated complications. From November 2015 to January 2018, we prospectively performed positron emission tomography/computed tomography (PET/CT) after injection of F¹⁸ -fluorodeoxyglucose (¹⁸ F-FDG) in adult kidney transplant recipients with surveillance biopsy at ~3 months posttransplantation. The Banff-2017 classification was used. The ratio of the mean standard uptake value (mSUVR) between kidney cortex and psoas muscle was measured. Urinary levels of CXCL-9 were concomitantly quantified. Our 92-patient cohort was categorized upon histology: normal (n = 70), borderline (n = 16), and SCR (n = 6). No clinical or biological difference was observed between groups. The mSUVR reached 1.87 ± 0.55, 1.94 ± 0.35, and 2.41 ± 0.54 in normal, borderline, and SCR groups, respectively. A significant difference in mSUVR was found among groups. Furthermore, mSUVR was significantly higher in the SCR vs normal group. The area under the receiver operating characteristic curve (AUC) was 0.79, with 83% sensitivity using an mSUVR threshold of 2.4. The AUC of urinary CXCL-9/creatinine ratios comparatively reached 0.79. The mSUVR positively correlated with ti and acute composite Banff scores. ¹⁸ F-FDG-PET/CT helps noninvasively exclude SCR, with a negative predictive value of 98%. External validations are required.

Low-dose Rituximab and Thymoglobulin Induction With Steroid-free Maintenance Immunosuppression and Protocol Biopsies Improves Long-term Patient and Graft Survival After Kidney Transplantation: Survival and Safety Outcomes in More Than 1100 Patients From a Single Center

BACKGROUND

Steroid-free maintenance immunosuppression after kidney transplantation provides acceptable patient and graft survival and minimizes steroid-associated side effects among recipients with a low immunological risk. However, the long-term outcomes of such protocols, incorporating low-dose rituximab and thymoglobulin induction along with protocol biopsies, in non-European populations remains underreported.

METHODS

We retrospectively analyzed 1142 consecutive kidney transplantations conducted at our center from July 2005 to October 2017. Immunosuppression protocol included induction with thymoglobulin and low-dose preoperative rituximab. Maintenance immunosuppression consisted of tacrolimus and mycophenolate mofetil; prednisolone was discontinued on postoperative day 5. Protocol biopsies were carried out at 3 months and at 1, 5, and 10 years after transplantation-in addition to the indicated biopsies. The 12-year patient and graft survival and posttransplantation complications were studied.

RESULTS

The analysis of outcomes was conducted for 1111 transplant recipients. Patients (70.59%) remained steroid-free at 12 years after transplantation. The patient survival rates at 1, 5, and 12 years were 97.7%, 94.8%, and 92.4%, respectively. The corresponding graft survival rates were 97.2%, 90.9%, and 86.1%, respectively. Biopsy-proven acute rejection occurred in 12.7% of recipients, including 3.5% subclinical rejections. The cumulative incidence of graft loss was 6.56% at 12.3 years. The overall incidence of death was 5.3%.

CONCLUSIONS

Steroid-free maintenance immunosuppression was associated with excellent long-term patient and graft survival rates and reduced incidence of prednisolone-related side effects, despite acceptable rejection rates. Low-dose rituximab with thymoglobulin induction with immediate steroid withdrawal and surveillance biopsies resulted in excellent long-term outcomes in our single-center experience.

A Peripheral Blood Gene Expression Signature to Diagnose Subclinical Acute Rejection

BACKGROUND

In kidney transplant recipients, surveillance biopsies can reveal, despite stable graft function, histologic features of acute rejection and borderline changes that are associated with undesirable graft outcomes. Noninvasive biomarkers of subclinical acute rejection are needed to avoid the risks and costs associated with repeated biopsies.

METHODS

We examined subclinical histologic and functional changes in kidney transplant recipients from the prospective Genomics of Chronic Allograft Rejection (GoCAR) study who underwent surveillance biopsies over 2 years, identifying those with subclinical or borderline acute cellular rejection (ACR) at 3 months (ACR-3) post-transplant. We performed RNA sequencing on whole blood collected from 88 individuals at the time of 3-month surveillance biopsy to identify transcripts associated with ACR-3, developed a novel sequencing-based targeted expression assay, and validated this gene signature in an independent cohort.

RESULTS

Study participants with ACR-3 had significantly higher risk than those without ACR-3 of subsequent clinical acute rejection at 12 and 24 months, faster decline in graft function, and decreased graft survival in adjusted Cox analysis. We identified a 17-gene signature in peripheral blood that accurately diagnosed ACR-3, and validated it using microarray expression profiles of blood samples from 65 transplant recipients in the GoCAR cohort and three public microarray datasets. In an independent cohort of 110 transplant recipients, tests of the targeted expression assay on the basis of the 17-gene set showed that it identified individuals at higher risk of ongoing acute rejection and future graft loss.

CONCLUSIONS

Our targeted expression assay enabled noninvasive diagnosis of subclinical acute rejection and inflammation in the graft and may represent a useful tool to risk-stratify kidney transplant recipients.

Clinical Significance of Renal Allograft Protocol Biopsies: A Single Tertiary Center Experience in Malaysia

Background

The role of protocol renal allograft biopsy in kidney transplantation is controversial due to the concern with procedural-related complications; however, its role is slowly evolving. Recent evidence suggests that protocol biopsy is useful in detecting subclinical renal pathology. Early recognition and treatment of renal pathologies can improve long-term outcomes of renal allografts.

Methodology

A total of 362 renal allograft protocol biopsies were performed in adult recipients of kidney transplantation between 2012 and 2017. After excluding those with poor quality or those performed with a baseline serum creatinine level >200 umol/L, we analyzed 334 (92.3%) biopsies. Histology reports were reviewed and categorized into histoimmunological and nonimmunological changes. The immunological changes were subcategorized into the following: (1) no acute rejection (NR), (2) borderline changes (BC), and (3) subclinical rejection (SCR). Nonimmunological changes were subcategorized into the following: (1) chronicity including interstitial fibrosis/tubular atrophy (IFTA), chronic T-cell-mediated rejection (TCMR), unspecified chronic lesions, and arterionephrosclerosis, (2) de novo glomerulopathy/recurrence of primary disease (RP), and (3) other clinically unsuspected lesions (acute pyelonephritis, calcineurin inhibitors toxicity, postinfective glomerulonephritis, and BK virus nephropathy). Risk factors associated with SCR were assessed.

Results

For the histoimmunological changes, 161 (48.2%) showed NR, 145 (43.4%) were BC, and 28 (8.4%) were SCR. These clinical events were more pronounced for the first 5 years; our data showed BC accounted for 59 (36.4%), 64 (54.2%), and 22 (40.7%) biopsies within <1 year, 1-5 years, and > 5 years, respectively (p = 0.011). Meanwhile, the incidence for SCR was 6 (3.7%) biopsies in <1 year, 18 (15.3%) in 1-5 years, and 4 (7.4%) in >5 years after transplantation (p=0.003). For the nonimmunological changes, chronicity, de novo glomerulopathy/RP, and other clinically unsuspected lesions were seen in 40 (12%), 10 (3%), and 12 (3.6%) biopsies, respectively. Living-related donor recipients were associated with decreased SCR (p=0.007).

Conclusions

Despite having a stable renal function, our transplant recipients had a significant number of subclinical rejection on renal allograft biopsies.

Multicentre randomised controlled trial protocol of urine CXCL10 monitoring strategy in kidney transplant recipients

INTRODUCTION

Subclinical inflammation is an important predictor of death-censored graft loss, and its treatment has been shown to improve graft outcomes. Urine CXCL10 outperforms standard post-transplant surveillance in observational studies, by detecting subclinical rejection and early clinical rejection before graft functional decline in kidney transplant recipients.

METHODS AND ANALYSIS

This is a phase ii/iii multicentre, international randomised controlled parallel group trial to determine if the early treatment of rejection, as detected by urine CXCL10, will improve kidney allograft outcomes. Incident adult kidney transplant patients (n~420) will be enrolled to undergo routine urine CXCL10 monitoring postkidney transplant. Patients at high risk of rejection, defined as confirmed elevated urine CXCL10 level, will be randomised 1:1 stratified by centre (n=250). The intervention arm (n=125) will undergo a study biopsy to check for subclinical rejection and biopsy-proven rejection will be treated per protocol. The control arm (n=125) will undergo routine post-transplant monitoring. The primary outcome at 12 months is a composite of death-censored graft loss, clinical biopsy-proven acute rejection, de novo donor-specific antibody, inflammation in areas of interstitial fibrosis and tubular atrophy (Banff i-IFTA, chronic active T-cell mediated rejection) and subclinical tubulitis on 12-month surveillance biopsy. The secondary outcomes include decline of graft function, microvascular inflammation at 12 months, development of IFTA at 12 months, days from transplantation to clinical biopsy-proven rejection, albuminuria, EuroQol five-dimension five-level instrument, cost-effectiveness analysis of the urine CXCL10 monitoring strategy and the urine CXCL10 kinetics in response to rejection therapy.

ETHICS AND DISSEMINATION

The study has been approved by the University of Manitoba Health Research Ethics Board (HS20861, B2017:076) and the local research ethics boards of participating centres. Recruitment commenced in March 2018 and results are expected to be published in 2023. De-identified data may be shared with other researchers according to international guidelines (International Committee of Medical Journal Editors [ICJME]).

TRIAL REGISTRATION NUMBER

NCT03206801; Pre-results.

Benefits and risks of protocol biopsies in pediatric renal transplantation

Protocol biopsies are defined as sampling of allograft tissue at predetermined times regardless of function. This procedure can be justified due to the lack of non-invasive methods to reliably diagnose rejection (acute or subclinical). Changes in creatinine are not seen with subclinical rejection or early acute rejection and do not always correlate with efficacy of treatment. Parents and providers are still hesitant to pursue protocol biopsy due to the potential complications and lack of definitive evidence of a benefit from doing this procedure. Importantly, the rate of transplant renal biopsy complications requiring additional intervention is low. It is unclear if detection and treatment of subclinical rejection detected on protocol biopsy will lead to improved graft survival. Our goal is to review the literature on this topic and share some of the experience in our center. Definition, indications, and complications of diagnostic transplant renal biopsies are not included in this review.

The 1-year Renal Biopsy Index: a scoring system to drive biopsy indication at 1-year post-kidney transplantation

Surveillance biopsies after renal transplantation remain debatable. To drive the decision of such intervention, we propose a predictive score of abnormal histology at 1-year post-transplantation, named 1-year Renal Biopsy Index (1-RBI). We studied 466 kidney recipients from the DIVAT cohort alive with a functioning graft and a surveillance biopsy at 1-year post-transplantation. Patients displaying abnormal histology (49%) (borderline, acute rejection, interstitial fibrosis and tubular atrophy [IFTA] grade 2 or 3, glomerulonephritis) were compared to the normal or subnormal (IFTA grade 1) histology group. Obtained from a lasso penalized logistic regression, the 1-RBI was composed of recipient gender, serum creatinine at 3, 6, and 12 month post-transplantation and anticlass II immunization at transplantation (internal validation: AUC = 0.71, 95% CI [0.53-0.83]; external validation: AUC = 0.62, 95% CI [0.58-0.66]). While we could not determinate a threshold able to identify patients at high chance of normal or subnormal histology, we estimated and validated a discriminating threshold capable of identifying a subgroup of 15% of the patients with a risk of abnormal histology higher than 80%. The 1-RBI is computable online at www.divat.fr. The 1-RBI could be a useful tool to standardize 1-year biopsy proposal and may for instance help to indicate one in case of high risk of abnormal histology.

Practice Patterns in the Treatment and Monitoring of Acute T Cell-Mediated Kidney Graft Rejection in Canada

Background

One of the goals of the Canadian National Transplant Research Program (CNTRP) is to develop novel therapies for acute rejection that could positively affect graft outcomes with greater efficacy or less toxicity. To develop innovative management strategies for kidney graft rejection, new modalities need to be compared with current clinical practices. However, there are no standardized practices concerning the management of acute T cell-mediated rejection (TCMR).

Objectives

To describe clinicians' practice patterns in the diagnosis, treatment, and monitoring of acute TCMR in Canada.

Design

Survey.

Setting Patients/Participants

Canadian transplant nephrologists and transplant surgeons involved in the management of acute TCMR.

Methods and Measurements

We developed an anonymous, web-based survey consisting of questions related to the diagnosis, treatment, and monitoring of TCMR. The survey was disseminated on 3 occasions between June and October 2016 through the Canadian Society of Transplantation (CST) kidney group electronic mailing list.

Results

Forty-seven respondents, mostly transplant nephrologists (97%), originating from at least 18 of the 25 Canadian centers offering adult or pediatric kidney transplantation, participated in the study. Surveillance biopsies were used by 28% of respondents to screen for kidney graft rejection. High-dose steroids were used by most of the respondents to treat clinical and subclinical Banff grade 1A and 1B rejections. Nine percent (95% confidence interval [CI]: 1-17) of practitioners used lymphocyte-depleting agents as the first-line approach for the treatment of Banff grade 1B acute rejection. Eighteen percent (95% CI: 7-29) and 36% (95% CI: 8-65) of respondents reported that they would not use high-dose steroids for treating clinical and subclinical borderline rejections, respectively. Seventy percent (95% CI: 54-83) of respondents answered that there was no indication to assess histological response to treatment independent of the change in kidney function.

Limitations

The limitations of this study are its limited sample size and the low representation of pediatric specialists.

Conclusions

There is heterogeneity regarding the use of surveillance biopsies, treatment of borderline rejection, and modalities to monitor treatment response among transplant physicians. Our results illustrate the current state of practice patterns across Canada and can be used to inform the design of future trials.

Utility of Serial Protocol Biopsies Performed After 1 Year in Predicting Long-Term Kidney Allograft Function According to Histologic Phenotype

OBJECTIVES

Prognostic implications of early protocol biopsies have been studied; however, the value of late protocol biopsy in predicting graft outcome has not been well defined. Here, we compared the effects of early and late protocol biopsy histologic findings in stable kidney allografts and aimed to understand the significance of "borderline" rejection on allograft function.

MATERIALS AND METHODS

We studied 261 biopsies from 159 renal transplant recipients who were on a steroid-free, calcineurin inhibitor and mycophenolate mofetil regimen and who received transplants between 2004 and 2012 with mean follow-up of 5 years. Early (between 3 and 9 mo) and subsequent late (between 12 and 24 mo) protocol biopsies were performed. Biopsies were classified as normal, interstitial fibrosis and/or tubular atrophy, subclinical acute rejection with interstitial fibrosis and/or tubular atrophy, and borderline rejection with interstitial fibrosis and/or tubular atrophy. A linear mixed-effects model was used to determine the effects of early and late protocol biopsies on estimated glomerular filtration rate changes, with baseline time for estimated glomerular filtration rate fixed at 12 months.

RESULTS

The adjusted model showed that estimated glomerular filtration rate at 3 months, donor age, delayed graft function, and early protocol biopsies were associated with baseline estimated glomerular filtration rate at 12 months. Estimated glomerular filtration rate changes over time were associated with findings of interstitial fibrosis and/or tubular atrophy at early biopsy and subclinical acute rejection and borderline rejection at late biopsy. At last follow-up, final estimated glomerular filtration rate was significantly associated with interstitial fibrosis and/or tubular atrophy at early biopsy and with subclinical acute rejection at late biopsy.

CONCLUSIONS

Although early protocol biopsy predicted baseline estimated glomerular filtration rate, late biopsy was important for predicting changes in function over time. In addition, a diagnosis of "borderline" rejection on protocol biopsies predicted long-term graft function.

Subclinical Rejection in Renal Transplantation: Reappraised

Short-term outcomes in renal transplantation have improved significantly in the past few years. However, the improvement in long-term outcomes has been modest. The reasons for graft failure beyond the first year of transplantation have been attributed to several different factors. We believe that subclinical rejection (SCR) may be 1 of the factors that contribute to graft loss in the long run. We also believe that there are data to suggest that SCR leads to progressive fibrosis and loss of graft function. This has been demonstrated even in patients who have mild degrees of subclinical inflammation. This review outlines the major studies that have been published on this important topic. It also outlines potential risk factors for the development of SCR. The current approach and diagnostic methods are discussed as well as their pros and cons. Newer noninvasive methods of diagnosis as well as molecular diagnostics and their merits and shortcomings are also discussed in some depth. Thus, the proposed state of the art review on SCR will create a renewed interest at all levels including transplant clinicians, transplant researchers, pharmaceutical industries as well as regulatory organizations.

Kidney Fibrosis: Origins and Interventions

All causes of renal allograft injury, when severe and/or sustained, can result in chronic histological damage of which interstitial fibrosis and tubular atrophy are dominant features. Unless a specific disease process can be identified, what drives interstitial fibrosis and tubular atrophy progression in individual patients is often unclear. In general, clinicopathological factors known to predict and drive allograft fibrosis include graft quality, inflammation (whether "nonspecific" or related to a specific diagnosis), infections, such as polyomavirus-associated nephropathy, calcineurin inhibitors (CNI), and genetic factors. The incidence and severity of chronic histological damage have decreased substantially over the last 3 decades, but it is difficult to disentangle what effects individual innovations (eg, better matching and preservation techniques, lower CNI dosing, BK viremia screening) may have had. There is little evidence that CNI-sparing/minimization strategies, steroid minimization or renin-angiotensin-aldosterone system blockade result in better preservation of intermediate-term histology. Treatment of subclinical rejections has only proven beneficial to histological and functional outcome in studies in which the rate of subclinical rejection in the first 3 months was greater than 10% to 15%. Potential novel antifibrotic strategies include antagonists of transforming growth factor-β, connective tissue growth factor, several tyrosine kinase ligands (epidermal growth factor, platelet-derived growth factor, vascular endothelial growth factor), endothelin and inhibitors of chemotaxis. Although many of these drugs are mainly being developed and marketed for oncological indications and diseases, such as idiopathic pulmonary fibrosis, a number may hold promise in the treatment of diabetic nephropathy, which could eventually lead to applications in renal transplantation.

Kidney allograft surveillance biopsy practices across US transplant centers: A UNOS survey

BACKGROUND

The approach to the diagnosis and management of subclinical rejection (SCR) in kidney transplant recipients remains controversial.

METHODS

We conducted a survey through UNOS across US transplant centers regarding their approach to surveillance biopsies and reasons for the nonperformance of surveillance biopsies.

RESULTS

Responses were obtained from 106/238 centers (45%), and only 18 (17%) of the centers performed surveillance biopsies on all patients and 22 (21%) performed biopsy for select cases. The most common time points for surveillance biopsies were 3 and 12  months post-transplant. The common reasons for not performing biopsies were low yield (n = 44, 65%) and the belief that it will not change outcome (n = 24, 36%). The incidence of SC-TCMR was ≥ 10% among 39% of centers. The mean serum creatinine was slightly worse by 0.06 mg/dL at 1 year and 0.07 mg/dL at 3 years among centers performing biopsy, P < .0001. The. 1-and 3-year Observed-Expected (O-E) graft survival was similar among centers performing biopsies vs. those not performing biopsy (P = .07, .88).

CONCLUSION

Only 17% of US centers perform surveillance biopsies, with another 21% performing surveillance biopsies in select cases (among centers that responded to the survey). Greater uniformity in the approach and management of this condition is of paramount importance.

Protocol Biopsies: Utility and Limitations

As both T cell and antibody-mediated rejection can have a subclinical phase, protocol biopsies provide an early opportunity to intervene before the onset of clinical allograft dysfunction. Protocol biopsies are usually done after reperfusion to establish baseline, between 3 and 6 months to identify subclinical rejection, and at 6-12 months to assess chronicity and persistent inflammation that have prognostic implication. Treatment of both subclinical T cell and antibody-mediated rejection prevents progression of rejection and development of interstitial fibrosis/tubular atrophy or transplant glomerulopathy. Although subclinical rejection has become less frequent in low-risk patients on triple immunosuppression containing tacrolimus, protocol biopsies may still be useful in selected population. Protocol biopsies are more likely to benefit patients at higher risk for rejection, including those who are highly sensitized, transplanted across donor-specific antibody barriers, or on calcineurin inhibitor/corticosteroids sparing regimens. Interstitial fibrosis on protocol biopsies, especially in conjunction with persistent inflammation, predicts lower allograft survival.

Total inflammation in early protocol kidney graft biopsies does not predict progression of fibrosis at one year post-transplant

INTRODUCTION

There is an uncertainty whether total inflammation in early protocol kidney graft biopsies is associated with fibrosis progression. We investigated whether total inflammation, both in fibrotic and non-fibrotic areas, at week 6 would predict fibrosis progression at one yr post-transplant.

METHODS

We included 156 single adult ABO compatible kidney recipients with adequate week 6 and one yr transplant protocol biopsies (312 biopsies). Biopsies were scored according to the current Banff criteria. In addition, fibrosis and inflammation in fibrotic and non-fibrotic areas were scored in a 10-grade semi-quantitative eyeballing system from 0% to 100%.

RESULTS

Fibrosis increased significantly from week 6 to one yr both by the 10-grade scoring system from 0.69 ± 1.07 to 1.45 ± 1.86, (mean ± SD), p < 0.001 and by Banff interstitial fibrosis (ci) scoring 0.81 ± 0.65 to 1.13 ± 0.87, p < 0.001. The 10-grade scoring system detected a larger proportion of fibrosis progressors than the Banff scoring 40.4% vs. 35.5%, p < 0.001. No significant positive association was found between inflammation at week 6 and progression of fibrosis in either of the scoring systems.

CONCLUSIONS

Total inflammation in kidney transplant biopsies at week 6 did not predict progression of fibrosis at one yr post-transplant.

Advances in pharmacotherapy to treat kidney transplant rejection

INTRODUCTION

Current immunosuppressive combination therapy provides excellent prevention of T-cell-mediated rejection following renal transplantation; however, antibody-mediated rejection remains of high concern and accounts for a large number of long-term allograft losses. The recent development of protocol biopsies resulted in the definition of subclinical rejection (SCR), showing histologic evidence for rejection but unremarkable clinical course.

AREAS COVERED

This review describes the current knowledge and evidence of pharmacotherapy to treat kidney allograft rejections and covers SCR treatment options. Each substance is analyzed with regard to its classical indication and further discussed for the treatment of other forms of rejection.

EXPERT OPINION

Despite a lack of randomized trials, early acute T-cell-mediated rejection can be treated effectively in most cases without graft loss. The necessity to treat SCR is currently unclear. Due to a lack of effective therapies, new treatment approaches for antibody-mediated rejection are an urgent medical need to improve long-term outcomes. Future research should aim to better define pathophysiology and histology, stratify risk, and develop rational treatment strategies from randomized controlled trials, in order to establish the value of novel therapies in the arsenal of rejection pharmacotherapy. However, the effective prevention of rejection with minimal side effects still remains the goal in immunosuppression.

Developing renal allograft surveillance strategies - urinary biomarkers of cellular rejection

Purpose of review

Developing tailored immunosuppression regimens requires sensitive, non-invasive tools for serial post-transplant surveillance as the current clinical standards with serum creatinine and proteinuria are ineffective at detecting subclinical rejection. The purpose of this review is: (i) to illustrate the rationale for allograft immune monitoring, (ii) to discuss key steps to bring a biomarker from bench-to-bedside, and (iii) to present an overview of promising biomarkers for cellular rejection.

Sources of information

PubMed.

Findings

Recent multicentre prospective observational cohort studies have significantly advanced biomarker development by allowing for the adequately powered evaluation of multiple biomarkers capable of detecting allograft rejection. These studies demonstrate that urinary CXCR3 chemokines (i.e. CXCL9 and CXCL10) are amongst the most promising for detecting subclinical inflammation; increasing up to 30 days prior to biopsy-proven acute rejection; decreasing in response to anti-rejection therapy; and having prognostic significance for the subsequent development of allograft dysfunction. Urinary CXCR3 chemokines are measured by simple and cost-effective ELISA methodology, which can readily be implemented in clinical labs.

Limitations

Many biomarker studies are performed in highly selected patient groups and lack surveillance biopsies to accurately classify healthy transplants. Few validation studies have been done in unselected, consecutive patient populations to characterize population-based diagnostic performance.

Implications

Based on these data, prospective interventional trials should be undertaken to determine if chemokine-based post-transplant monitoring strategies can improve long-term renal allograft outcomes. This last step will be necessary to move novel biomarkers from the bench-to-bedside.

Urinary cell mRNA profiles predictive of human kidney allograft status

Kidney allograft status is currently characterized using the invasive percutaneous needle core biopsy procedure. The procedure has become safer over the years, but challenges and complications still exist including sampling error, interobserver variability, bleeding, arteriovenous fistula, graft loss, and even death. Because the most common type of acute rejection is distinguished by inflammatory cells exiting the intravascular compartment and gaining access to the renal tubular space, we reasoned that a kidney allograft may function as an in vivo flow cytometer and sort cells involved in rejection into urine. To test this idea, we developed quantitative polymerase chain reaction (PCR) assays for absolute quantification of mRNA and pre-amplification protocols to overcome the low RNA yield from urine. Here, we review our single center urinary cell mRNA profiling studies that led to the multicenter Clinical Trials in Organ Transplantation (CTOT-04) study and the discovery and validation of a 3-gene signature of 18S rRNA-normalized measures of CD3ε mRNA and IP-10 mRNA and 18S rRNA that is diagnostic and predictive of acute cellular rejection in the kidney allograft. We also review our development of a 4-gene signature of mRNAs for vimentin, NKCC2, E-cadherin, and 18S rRNA diagnostic of interstitial fibrosis/tubular atrophy (IF/TA).

Subclinical Rejection Phenotypes at 1 Year Post-Transplant and Outcome of Kidney Allografts

Kidney allograft rejection can occur in clinically stable patients, but long-term significance is unknown. We determined whether early recognition of subclinical rejection has long-term consequences for kidney allograft survival in an observational prospective cohort study of 1307 consecutive nonselected patients who underwent ABO-compatible, complement-dependent cytotoxicity-negative crossmatch kidney transplantation in Paris (2000-2010). Participants underwent prospective screening biopsies at 1 year post-transplant, with concurrent evaluations of graft complement deposition and circulating anti-HLA antibodies. The main analysis included 1001 patients. Three distinct groups of patients were identified at the 1-year screening: 727 (73%) patients without rejection, 132 (13%) patients with subclinical T cell-mediated rejection (TCMR), and 142 (14%) patients with subclinical antibody-mediated rejection (ABMR). Patients with subclinical ABMR had the poorest graft survival at 8 years post-transplant (56%) compared with subclinical TCMR (88%) and nonrejection (90%) groups (P<0.001). In a multivariate Cox model, subclinical ABMR at 1 year was independently associated with a 3.5-fold increase in graft loss (95% confidence interval, 2.1 to 5.7) along with eGFR and proteinuria (P<0.001). Subclinical ABMR was associated with more rapid progression to transplant glomerulopathy. Of patients with subclinical TCMR at 1 year, only those who further developed de novo donor-specific antibodies and transplant glomerulopathy showed higher risk of graft loss compared with patients without rejection. Our findings suggest that subclinical TCMR and subclinical ABMR have distinct effects on long-term graft loss. Subclinical ABMR detected at the 1-year screening biopsy carries a prognostic value independent of initial donor-specific antibody status, previous immunologic events, current eGFR, and proteinuria.