Significance of revised criteria for chronic active T cell-mediated rejection in the 2017 Banff classification: Surveillance by 1-year protocol biopsies for kidney transplantation

Screening of novel biomarkers for acute kidney transplant rejection using DIA-MS based proteomics

BACKGROUND

Kidney transplantation is the preferred treatment for patients with end-stage renal disease. However, acute rejection poses a threat to the graft long-term survival. The aim of this study was to identify novel biomarkers to detect acute kidney transplant rejection.

METHODS

The serum proteomic profiling of kidney transplant patients with T cell-mediated acute rejection (TCMR) and stable allograft function (STA) was analyzed using data-independent acquisition mass spectrometry (DIA-MS). The differentially expressed proteins (DEPs) of interest were further verified by enzyme-linked immunosorbent assay (ELISA).

RESULTS

A total of 131 DEPs were identified between STA and TCMR patients, 114 DEPs were identified between mild and severe TCMR patients. The verification results showed that remarkable higher concentrations of serum amyloid A protein 1 (SAA1) and insulin like growth factor binding protein 2 (IGFBP2), and lower fetuin-A (AHSG) concentration were found in TCMR patients when compared with STA patients. We also found higher SAA1 concentration in severe TCMR group when compared with mild TCMR group. The receiver operating characteristics (ROC) analysis further confirmed that combination of SAA1, AHSG, and IGFBP2 had excellent performance in the acute rejection diagnosis.

CONCLUSIONS

Our data demonstrated that serum SAA1, AHSG, and IGFBP2 could be effective biomarkers for diagnosing acute rejection after kidney transplantation. DIA-MS has great potential in biomarker screening of kidney transplantation.

Significance of Perivascular Aggregates in Kidney Allografts: Evaluation of 1-Year Protocol Biopsies Using Recent Banff Classification

BACKGROUND

Perivascular aggregates (PVAs) often occur in kidney allografts; however, their significance needs to be re-evaluated in light of changes in the concept and criteria of allograft rejection.

METHODS

We reviewed 1-year protocol biopsies in 258 patients with kidney transplants to identify PVAs and concurrent pathology based on the Banff 2017 classification, including revised criteria for chronic active T-cell mediated rejection (CA-TCMR). We investigated the incidence of PVA, concurrent allograft lesions, diagnosis, and graft survival. No prisoners were used in this study, and no participants were coerced or paid.

RESULTS

We identified PVA in 81 biopsies (31.4%). The incidence of previous rejection (32.1% vs 12.4%, P= .0003) and total inflammation (1.3 ± 0.8 vs 0.6 ± 0.8, P < .0001), inflammation (0.7 ± 0.8 vs 0.2 ± 0.5, P < .0001), inflammation in the area of interstitial fibrosis and tubular atrophy (1.3 ± 1.2 vs 0.7 ± 0.9, P < .0001), tubulitis (1.4 ± 1.1 vs 0.6 ± 0.9, P < .0001), and interstitial fibrosis scores (1.2 ± 0.9 vs 0.9 ± 0.9, P= .01) were higher in PVA-positive compared with patients with PVA-negative. Diagnoses in the PVA-positive group revealed no rejection in 49.4%, CA-TCMR in 21.0%, borderline changes in 18.5%, and acute TCMR in 6.2%. CA-TCMR was more frequent in patients with PVA-positive (21.0% vs 4.0%, P < .0001). Graft survival was similar in both groups among all patients, no-rejection, any type of rejection, and CA-TCMR subgroups.

CONCLUSIONS

PVAs occur heterogeneously and are associated with previous rejection or concurrent CA-TCMR. The prognostic significance of PVAs in kidney transplantation is inconclusive, and further investigations are needed.

Emerging phenotypes in kidney transplant rejection

PURPOSE OF REVIEW

This review focuses on more recently emerging rejection phenotypes in the context of time post transplantation and the resulting differential diagnostic challenges. It also discusses how novel ancillary diagnostic tools can potentially increase the accuracy of biopsy-based rejection diagnosis.

RECENT FINDINGS

With advances in reducing immunological risk at transplantation and improved immunosuppression treatment renal allograft survival improved. However, allograft rejection remains a major challenge and represent a frequent course for allograft failure. With prolonged allograft survival, novel phenotypes of rejection are emerging, which can show complex overlap and transition between cellular and antibody-mediated rejection mechanisms as well as mixtures of acute/active and chronic diseases. With the emerging complexity in rejection phenotypes, it is crucial to achieve diagnostic accuracy in the individual patient.

SUMMARY

The prospective validation and adoption of novel molecular and computational diagnostic tools into well defined and appropriate clinical context of uses will improve our ability to accurately diagnose, stage, and grade allograft rejection.

The Banff 2022 Kidney Meeting Work Plan: Data-driven refinement of the Banff Classification for renal allografts

The XVIth Banff Meeting for Allograft Pathology was held in Banff, Alberta, Canada, from September 19 to 23, 2022, as a joint meeting with the Canadian Society of Transplantation. In addition to a key focus on the impact of microvascular inflammation and biopsy-based transcript analysis on the Banff Classification, further sessions were devoted to other aspects of kidney transplant pathology, in particular T cell-mediated rejection, activity and chronicity indices, digital pathology, xenotransplantation, clinical trials, and surrogate endpoints. Although the output of these sessions has not led to any changes in the classification, the key role of Banff Working Groups in phrasing unanswered questions, and coordinating and disseminating results of investigations addressing these unanswered questions was emphasized. This paper summarizes the key Banff Meeting 2022 sessions not covered in the Banff Kidney Meeting 2022 Report paper and also provides an update on other Banff Working Group activities relevant to kidney allografts.

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.

Key Points of the Banff 2019 Classification of Renal Allograft Pathology

The Banff 2019 Kidney Meeting Report was published following the 15th Banff Conference for Allograft Pathology, which was held in Pittsburgh on September 23-28, 2019. The diagnosis of renal transplant rejection based on the Banff 2019 classification is globally utilized. The Banff 2019 classification of renal allograft pathology includes several changes. This mini-review summarizes the key points and issues of the Banff 2019 classification. The criteria for borderline change have been reverted to ≥ i1, the t-IFTA score has been incorporated into the classification, the histological classification of polyoma virus nephropathy has been adopted, and a category was added for chronic (inactive) antibody-mediated rejection. In addition, whether the spread is diffuse or focal should now be noted in the presence of peritubular capillaritis. One of the issues with the Banff 2019 classification is the continuing lack of clarity regarding the definition of the t score, which is used to evaluate tubulitis not only in non-scarred areas but also in moderately atrophic tubules that are assumed to be present in scarred areas, which constitutes a contradiction in the definition.

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.

Chronic Active T-Cell Mediated Kidney Rejection as a Clinically Significant Type of Allograft Loss?

The purpose of this article is to assess the present knowledge about chronic active (CA) T-cell mediated rejection (TCMR) of a kidney. In the research authors review current Banff diagnostic criteria used in kidney rejection, focus on their possible future evolution, and investigate the role of currently available molecular methods that could be implemented into the diagnostic scheme. Research also points out previously and currently available treatment methods applied to CA TCMR and takes into account possible side effects consequent upon the therapy. Moreover, attention is being paid to the CA TCMR coincidence with other kidney rejection types such as antibody-mediated rejection (ABMR) and its influence on the treatment approach. Authors also mark the possibility of non-HLA antibodies coexistence in patients with CA TCMR and describe its possible resonance on kidney allograft function. Nonetheless, it seems that current knowledge about CA TCMR is not sufficient and requires further investigation.

Treatment of chronic active T cell-mediated rejection after kidney transplantation: A retrospective cohort study of 37 transplants

AIM

Data on the treatment of chronic active T cell-mediated rejection (CA-TCMR) are scarce, and therapeutical strategies for CA-TCMR have not been established. We retrospectively evaluated the outcomes and effects of treatment on pathological and clinical findings in patients with CA-TCMR.

METHODS

This study comprised 37 patients who underwent kidney transplantation at our institute who were diagnosed with CA-TCMR between January 2018 and December 2020. Patients were followed until October 2021.

RESULTS

Thirty-two of the 37 patients were treated. During the observation period, two patients died (5%), and five patients developed allograft loss (13%). A univariate Cox proportional hazards model showed that indication biopsy, higher spot urine protein/creatinine ratio (UPCR), and Banff ci/ct scores were risk factors for allograft loss. Of the treated patients, 23 underwent follow-up biopsies. The Wilcoxon signed-rank test showed significant improvement in the Baff scores for "ti", "i-IFTA", "t", and "t-IFTA" after treatment. On pathology, 13 (57%) of the patients who underwent follow-up biopsy improved to "no evidence of rejection" or "borderline change". Assuming that improvement in pathology to "borderline change" or "no evidence of rejection" on follow-up biopsy indicates response to treatment, multivariate logistic analysis showed that lower UPCR was a predictive factor for response to treatment. No specific effect of treatment type was observed.

CONCLUSIONS

Our results indicate that treatment could improve the pathological findings in CA-TCMR. This article is protected by copyright. All rights reserved.

Study protocol: the TRAnsplant BIOpsies (TRABIO) study - a prospective, observational, multicentre cohort study to assess the treatment of kidney graft rejections

INTRODUCTION

Despite continued efforts, long-term outcomes of kidney transplantation remain unsatisfactory. Kidney graft rejections are independent risk factors for graft failure. At the participating centres of the TRAnsplant BIOpsies study group, a common therapeutic standard has previously been defined for the treatment of graft rejections. The outcomes of this strategy will be assessed in a prospective, observational cohort study.

METHODS AND ANALYSIS

A total of 800 kidney transplantation patients will be enrolled who undergo a graft biopsy because of deteriorating kidney function. Patients will be stratified according to the Banff classification, and the influence of the treatment strategy on end points will be assessed using regression analysis. Primary end points will be all-cause mortality and graft survival. Secondary end points will be worsening of kidney function (≥30% decline of estimated Glomerular Filtration Rate [eGFR] or new-onset large proteinuria), recurrence of graft rejection and treatment response. Baseline data and detailed histopathology data will be entered into an electronic database on enrolment. During a first follow-up period (within 14 days) and subsequent yearly follow-ups (for 5 years), treatment strategies and clinical course will be recorded. Recruitment at the four participating centres started in September 2016. As of August 2020, 495 patients have been included.

ETHICS AND DISSEMINATION

Ethical approval for the study has been obtained from the ethics committee of Kiel (AZ B 278/16) and was confirmed by the committees of Munich, Mainz and Stuttgart. The results will be reported in a peer-reviewed journal, according to the Strengthening the Reporting of Observational Studies in Epidemiology criteria.

TRIAL REGISTRATION NUMBER

ISRCTN78772632; Pre-results.

Noninvasive Assessment of the Alloimmune Response in Kidney Transplantation

Transplantation remains the optimal mode of kidney replacement therapy, but unfortunately long-term graft survival after 1 year remains suboptimal. The main mechanism of chronic allograft injury is alloimmune, and current clinical monitoring of kidney transplants includes measuring serum creatinine, proteinuria, and immunosuppressive drug levels. The most important biomarker routinely monitored is human leukocyte antigen (HLA) donor-specific antibodies (DSAs) with the frequency based on underlying immunologic risk. HLA-DSA should be measured if there is graft dysfunction, immunosuppression minimization, or nonadherence. Antibody strength is semiquantitatively estimated as mean fluorescence intensity, with titration studies for equivocal cases and for following response to treatment. Determination of in vitro C1q or C3d positivity or HLA-DSA IgG subclass analysis remains of uncertain significance, but we do not recommend these for routine use. Current evidence does not support routine monitoring of non-HLA antibodies except anti-angiotensin II type 1 receptor antibodies when the phenotype is appropriate. The monitoring of both donor-derived cell-free DNA in blood or gene expression profiling of serum and/or urine may detect subclinical rejection, although mainly as a supplement and not as a replacement for biopsy. The optimal frequency and cost-effectiveness of using these noninvasive assays remain to be determined. We review the available literature and make recommendations.

Do we need to treat chronic active T cell-mediated rejection?

Chronic active T cell-mediated rejection, demonstrated by the presence of inflammation in areas of fibrosis, is associated with long-term allograft loss. Kung et al., in this issue of Kidney International, describe a series of cases of CA TCMR and analyze their clinical, molecular, and pathologic features as well as their response to therapy. Their translational study aids in understanding this diverse phenotype and provides future direction for managing these patients.