Banff 2013 meeting report: inclusion of c4d-negative antibody-mediated rejection and antibody-associated arterial lesions

Vesicoureteral Reflux Causes Interstitial Inflammation in Pediatric Kidney Allograft: A Clinicopathological Analysis of 1-Year Protocol Biopsies

INTRODUCTION

At present, there is limited evidence of the histological impact of vesicoureteral reflux (VUR) on pediatric kidney allografts. In this study, we aimed to investigate the relationship between VUR diagnosed by voiding cystourethrography (VCUG) and 1-year protocol biopsy results.

METHODS

One hundred thirty-eight pediatric kidney transplantations were performed in Toho University Omori Medical Center between 2009 and 2019. We included 87 pediatric transplant recipients who were evaluated for VUR by VCUG prior to or at the time of the 1-year protocol biopsy and underwent a 1-year protocol biopsy after transplantation. We evaluated the clinicopathological findings of the VUR and non-VUR groups, and histological scores were evaluated using the Banff score. Tamm-Horsfall protein (THP) within the interstitium was identified by light microscopy.

RESULTS

Of the 87 transplant recipients, 18 cases (20.7%) were diagnosed with VUR by VCUG. The clinical background and findings were not significantly different between the VUR and non-VUR groups. The pathological findings revealed a significantly higher Banff total interstitial inflammation (ti) score in the VUR group than in the non-VUR group. Multivariate analysis indicated a significant relationship between the Banff ti score and THP within the interstitium, and VUR. The 3-year protocol biopsy results (n = 68) revealed a significantly higher Banff interstitial fibrosis (ci) score in the VUR group than in the non-VUR group.

CONCLUSION

VUR caused interstitial fibrosis in the 1-year pediatric protocol biopsies, and interstitial inflammation at the 1-year protocol biopsy may affect interstitial fibrosis at the 3-year protocol biopsy.

The Association Between Kidney Donor Profile Index and 1-y Graft Function

The association between Kidney Donor Profile Index (KDPI) and 1-y estimated glomerular filtration rate (eGFR) with long-term kidney graft survival is well known. Yet, the association between KDPI and 1-y eGFR remains uncertain considering the several concurrent competing risk factors.

Methods

This single-center, retrospective cohort study analyzed data from 3059 consecutive deceased donor kidney transplant recipients with a 1-y follow-up from January 2013 to December 2017. The aim was to determine the association between the KDPI strata (0%-35%, 36%-50%, 51%-85%, 86%-100%) and 1-y eGFR estimated by the CKD-EPI equation.

Results

The incidence of delayed graft function (50.6% versus 59.3% versus 62.7% versus 62.0%; P < 0.001) and cytomegalovirus infection (36.7% versus 36.6% versus 43.3% versus 57.8%; P < 0.001) increased with increasing KDPI strata but not biopsy-proven acute rejection (9.1% versus 9.8% versus 8.4% versus 9.1%; P = 0.736). The median 1-y eGFR decreased with increasing KDPI strata (64.8 versus 53.5 versus 46.9 versus 39.1 mL/min/1.73 m²; P < 0.001). In the Cox regression, the higher the KDPI was, the lower the probability of a lower 1-y eGFR was. Assuming the 0%-35% strata as the reference, the likelihood of eGFR <50 mL/min/1.73 m² was increased by 76.6% (hazard ratio [HR] = 1.767, 95% confidence interval [CI] = 1.406-2.220), 2.24- and 2.87-fold higher for KDPI higher >35%-50% (HR = 2.239, 95% CI = 1.862-2.691), and >51%-85% (HR = 2.871, 95% CI = 2.361-3.491), respectively. Other variables associated with a lower graft function were donor sex (HR male versus female = 0.896, 95% CI = 0.813-0.989) and cold ischemia time (HR for each hour = 1.011, 95% CI = 1.004-1.019). This association was sustained after the Poisson mediation analysis, including delayed graft function, cytomegalovirus, and acute rejection as mediators.

Conclusions

In this cohort of deceased donor kidney recipients, KDPI, and cold ischemia time were the major independent risk factors associated with lower 1-y kidney function.

An automated histological classification system for precision diagnostics of kidney allografts

For three decades, the international Banff classification has been the gold standard for kidney allograft rejection diagnosis, but this system has become complex over time with the integration of multimodal data and rules, leading to misclassifications that can have deleterious therapeutic consequences for patients. To improve diagnosis, we developed a decision-support system, based on an algorithm covering all classification rules and diagnostic scenarios, that automatically assigns kidney allograft diagnoses. We then tested its ability to reclassify rejection diagnoses for adult and pediatric kidney transplant recipients in three international multicentric cohorts and two large prospective clinical trials, including 4,409 biopsies from 3,054 patients (62.05% male and 37.95% female) followed in 20 transplant referral centers in Europe and North America. In the adult kidney transplant population, the Banff Automation System reclassified 83 out of 279 (29.75%) antibody-mediated rejection cases and 57 out of 105 (54.29%) T cell-mediated rejection cases, whereas 237 out of 3,239 (7.32%) biopsies diagnosed as non-rejection by pathologists were reclassified as rejection. In the pediatric population, the reclassification rates were 8 out of 26 (30.77%) for antibody-mediated rejection and 12 out of 39 (30.77%) for T cell-mediated rejection. Finally, we found that reclassification of the initial diagnoses by the Banff Automation System was associated with an improved risk stratification of long-term allograft outcomes. This study demonstrates the potential of an automated histological classification to improve transplant patient care by correcting diagnostic errors and standardizing allograft rejection diagnoses.ClinicalTrials.gov registration: NCT05306795 .

Complement detection in kidney biopsies - utility and challenges

PURPOSE OF REVIEW

This review discusses the important role of staining for components of the complement cascade in both native and transplant kidney biopsies. The use of complement staining as a marker of prognosis, disease activity, and as a potential future tool in identifying patients who may benefit from complement-targeted therapies is discussed.

RECENT FINDINGS

While staining for C3, C1q and C4d can yield valuable information about complement activation in kidney biopsies, to adequately assess complement activation and potential therapeutic targets, expanded staining panels looking at multiple split products and complement regulatory proteins are needed. Recent progress has been made in identifying markers of disease severity in C3 glomerulonephritis and IgA nephropathy, such as Factor H-related Protein-5, which may serve as future tissue biomarkers. In the transplant setting, the limitation of relying on C4d staining to identify antibody mediated rejection is giving way to molecular diagnostics, including The Banff Human Organ Transplant (B-HOT) panel, which includes numerous complement complement-related transcripts, with the classical, lectin, alternative, and common pathways.

SUMMARY

Staining for complement components in kidney biopsies to understand how complement is activated in individual cases may help to identify patients who may benefit from complement-targeted therapies.

The Influence of Antibodies against Angiotensin II Type-1 Receptor on the Outcome of Kidney Transplantation: A Single-Center Retrospective Study

Allo- and autoimmune mechanisms are involved in kidney allograft rejection and loss. This study investigates the impact of anti-angiotensin II type-1 receptor antibodies (anti-AT1RAbs) detected alone or in association with HLA donor-specific antibodies (HLA-DSAs) on the outcome of kidney transplantation (KTx). Anti-AT1RAbs and HLA-DSAs were detected in 71 kidney transplant (KT) recipients who developed biopsy-proven acute or chronic active T-cell rejection (TCMR) (n = 51) or antibody-mediated rejection (ABMR) (n = 20), forming the rejection group (RG). The control group (CG) included 71 KTx recipients with comparable characteristics without rejection. All patients had been transplanted with negative T/B flow crossmatch (T/BFCXM). The median follow-up period was 3.7 years. Antibodies were determined pre- and periodically post-KTx by Luminex method for HLA-DSAs and enzyme-linked immunosorbent assay for anti-AT1RAbs. Before KTx, twenty-three (32.4%) patients in the RG, sixteen with TCMR and seven with ABMR, were found anti-AT1Rabs-positive (≥10 U/mL) versus eleven (15.5%) patients in the CG (p = 0.031). Simultaneous detection of preformed anti-AT1RAbs and HLA-DSAs was found in five patients of the RG versus two of the CG (p = 0.355). At the time of transplant biopsy, fifteen (21.1%) patients, four with ABMR and eleven with TCMR, were positive for anti-AT1RAbs. Anti-AT1RAbs and HLA-DSAs were detected simultaneously in 7/15 (46.7%) cases, three with ABMR and four with TCMR. During the follow-up, thirteen (18.3%) patients in the RG, eight with ABMR and five with TCMR, lost their graft compared to one patient (1.4%) in the CG (p = 0.001). Six out of thirteen (46.2%) RG patients who lost the graft were found positive for anti-AT1RAbs pretransplant. Patient survival with functioning graft did not differ significantly between anti-AT1Rabs-positive and negative KT recipients (log-rank p = 0.88). Simultaneous detection of anti-ATR1Abs and HLA-DSAs did not have a significant influence on patient survival with functioning graft (log-rank p = 0.96). Graft function at the end of the follow-up was better, but not significantly, in anti-AT1Rabs-negative patients, with serum creatinine 1.48 [1.20-1.98] mg/dL and eGFR (CKD-EPI) 48.5 [33.5-59.0] mL/min/1.73 m², compared to anti-AT1Rabs-positive ones who had serum creatinine 1.65 [1.24-2.02] mg/dL (p = 0.394) and eGFR (CKD-EPI) 47.0 [34.8-60.3] mL/min/1.73 m² (p = 0.966). Anti-AT1RAbs detection pretransplant characterizes KT recipients at increased risk of cellular or antibody-mediated rejection. Furthermore, anti-AT1RAbs, detected alone or simultaneously with HLA-DSAs, appear to be associated with impaired graft function, but their role in graft survival has not been documented in this study. Screening for these antibodies appears to complement pretransplant immunological risk assessment.

Outcomes of kidney transplantation in patients with congenital anomalies of the kidney and urinary tract: a propensity-score-matched analysis with case-control design

BACKGROUND

We compared long-term outcomes after kidney transplantation (KTx) in patients with and without congenital anomalies of the kidney and urinary tract (CAKUT).

METHODS

KTx recipients (KTRs) with CAKUT in 1980-2016 were identified; their hard copy and electronic medical records were reviewed and compared to a propensity-score-matched control group (non-CAKUT) from the same period. The primary outcomes were graft loss or death with a functioning graft; secondary outcomes included posttransplant urinary tract infections (UTIs) and biopsy-proven rejection (BPR).

RESULTS

: We identified 169 KTRs with CAKUT and 169 matched controls. Median follow-up was 132 (IQR: 75.0-170.0) months. UTIs were more common in CAKUT patients compared to non-CAKUT group (20.7% vs 10.7%; p = 0.01). Rates of BPR were similar between the two groups. In Kaplan-Meier analysis, 10-year graft survival rates were significantly higher in the CAKUT group than in the non-CAKUT group (87.6% vs 69.2%; p < 0.001), while patient survival rates were similar. In multivariate Cox regression analyses, CAKUT (HR: 0.469; 95% CI: 0.320-0.687; p < 0.001) and PRA positivity before transplantation (HR: 3.756; 95% CI: 1.507-9.364; p = 0.005) predicted graft loss.

DISCUSSION

Graft survival in KTRs with CAKUT appears superior to KTRs without CAKUT. Transplant centers should develop multidisciplinary educational and social working groups to support and encourage CAKUT patients with kidney failure to seek for transplants.

Microvascular inflammation in the absence of human leukocyte antigen-donor-specific antibody and C4d: An orphan category in Banff classification with cytotoxic T and natural killer cell infiltration

Isolated microvascular inflammation (iMVI) without HLA donor-specific antibodies or C4d deposition in peritubular capillaries remains an enigmatic phenotype that cannot be categorized as antibody-mediated rejection (ABMR) in recent Banff classifications. We included 221 kidney transplant recipients with biopsies with ABMR (n = 73), iMVI (n = 32), and normal (n = 116) diagnoses. We compared peripheral blood leukocyte distribution by flow cytometry and inflammatory infiltrates in kidney transplant biopsies among groups. Flow cytometry showed fewer lymphocytes and total, CD4+, and CD8+ peripheral T cells in iMVI compared with ABMR and normal cases. ABMR and iMVI had fewer total natural Killer (NK) cells but more NKG2A+ NK cells. Immunohistochemistry indicated that ABMR and iMVI had greater CD3+ and CD68+ glomerular infiltration than normal biopsies, whereas CD8+ and TIA1+ cells showed only increased iMVI, suggesting they are cytotoxic T cells. Peritubular capillaries displayed more CD3+, CD56+, TIA1+, and CD68+ cells in both ABMR and iMVI. In contrast, iMVI had less plasma cell infiltration in peritubular capillaries and interstitial aggregates than ABMR. iMVI displayed decreased circulating T and NK cells mirrored by T cell and NK cell infiltration in the renal allograft, similar to ABMR. However, the lesser plasma cell infiltration in iMVI may suggest an antibody-independent underlying stimulus.

Significance of Multinucleated Polyploidization of Tubular Epithelial Cells in Kidney Allografts

INTRODUCTION

Multinucleated polyploidization (MNP) of tubular epithelial cells is occasionally observed in kidney allografts. The present study aimed to clarify the clinical and pathological significance of MNP of tubular epithelial cells in kidney allografts.

METHODS

Fifty-eight 1-year biopsies from 58 patients who underwent kidney transplantation at our hospital from January 2016 to December 2017 were included. MNP was counted in each specimen, and the specimens were divided into two groups by the median value. The differences in clinical and pathological characteristics were compared. Ki67-positive cells were counted among tubular epithelial cells to explore the association between cell cycle and MNP. In an additional cohort, MNP was compared between biopsies after precedent T-cell-mediated rejection and precedent medullary ray injury.

RESULTS

The 58 cases were divided into two groups by the median total amount of MNP: group A (MNP > 3) and group B (MNP ≤ 3). Maximum t-score before the 1-year biopsy was significantly higher in group A compared with group B. Other clinical or histological characteristics did not differ significantly. Total amount of Ki67-positive tubular epithelial cells was significantly correlated with total amount of MNP. Significantly higher amount of MNP was observed in cases with precedent T-cell-mediated rejection compared with precedent medullary ray injury. On receiver operating characteristic curve analysis, the cut-off value of MNP to predict precedent T-cell-mediated rejection was 8.5.

CONCLUSIONS

MNP in tubular epithelial cells reflects prior tubular inflammation in kidney allografts. High amount of MNP indicates precedent T-cell-mediated rejection rather than precedent medullary ray injury caused by nonimmune etiologies.

On a Long and Winding Road: Alloantibodies in Organ Transplantation

Today we know that both the humoral and the cellular arm of the immune system are engaged in severe immunological challenges. A close interaction between B and T cells can be observed in most "natural" challenges, including infections, malignancies, and autoimmune diseases. The importance and power of humoral immunity are impressively demonstrated by the current coronavirus disease 2019 pandemic. Organ transplant rejection is a normal immune response to a completely "artificial" challenge. It took a long time before the multifaceted action of different immunological forces was recognized and a unified, generally accepted opinion could be formed. Here, we address prominent paradigms and paradigm shifts in the field of transplantation immunology. We identify several instances in which the transplant community missed a timely paradigm shift because essential, available knowledge was ignored. Moreover, we discuss key findings that critically contributed to our understanding of transplant immunology but sometimes developed with delay and in a roundabout way, as was the case with antibody-mediated rejection-a main focus of this article. These include the discovery of the molecular principles of histocompatibility, the recognition of the microcirculation as a key interface of immune damage, the refinement of alloantibody detection, the description of C4d as a footmark of endothelium-bound antibody, and last but not least, the developments in biopsy-based diagnostics beyond conventional morphology, which only now give us a glimpse of the enormous complexity and pathogenetic diversity of rejection.

Antibody-Mediated Rejection: Diagnosis and Treatment

Antibody-mediated rejection (AMR) is a form of lung allograft rejection that is emerging as an important risk factor for chronic lung allograft dysfunction and decreased long-term survival. In this review, we provide a brief overview of our current understanding of its pathophysiology with an emphasis on donor-specific antibodies before moving on to focus on the current diagnostic criteria and treatment strategies. Our goal is to discuss the limitations of our current knowledge and explore how novel diagnostic and therapeutic options aim to improve outcomes through earlier definitive diagnosis and preemptive targeted treatment.

Immunohistochemical Analysis of Lymphocyte Populations in Acute Skin Rejection: The University Health Network Addition to the Banff Classification

Acute rejection in vascularized composite allotransplantation has been identified using the Banff 2007 working classification. We propose an addition to this classification based on histological and immunological assessment within the skin and subcutaneous tissue.

Methods

Biopsies from vascularized composite transplant patients were obtained at scheduled visits and whenever skin changes occurred. Histology and immunohistochemistry were performed on all samples, looking at infiltrating cells.

Results

Observations were made specifically related to each component of the skin, including the epidermis, dermis, vessels, and subcutaneous tissue. Our findings led to the establishment of the University Health Network addition of skin rejection.

Conclusions

The high rate of rejection where the skin is involved requires novel techniques for early detection. The University Health Network skin rejection addition can serve as an adjunct to the Banff classification.

Quantitative scoring of progression in transplant glomerulopathy using digital pathology may be superior to Banff cg scoring

Antibody-mediated rejection (ABMR) is a major cause of kidney allograft failure. Biopsy-based surrogate endpoints reflecting ABMR progression on sequential biopsies that predict long-term outcome offer the potential to make treatment trials for ABMR feasible. However, the Banff transplant glomerulopathy (TG) scoring system (chronic glomerular injury score [cg]) relies on relatively crude and arbitrary ordinal grades and has low inter-observer concordance that currently limits its usefulness as a surrogate endpoint for ABMR progression in clinical drug trials. Here, we describe and validate a novel quantitative method for quantifying progression of TG in ABMR. Using digital pathology in sequential biopsies from 75 patients at various stages of ABMR, we scored all capillaries in the most affected glomeruli for basement membrane duplication that were correlated with allograft function, outcome, Banff lesion scores, and gene expression. Our digital scoring reflected TG progression better than the categorical Banff cg score and correlated with Banff ABMR and chronicity lesions, but not transcript changes. In multivariate analysis, the delta change between biopsies with serum creatinine and mean percent duplicated glomerular basement membranes was significantly associated with graft loss. Neither the delta in any Banff lesion scores (including cg) nor in gene expression was associated with outcome. Receiver operating characteristic curve analysis showed that the digital pathology approach was superior to the conventional score for predicting graft failure. Thus, our digital pathology-based approach for scoring TG accurately assessed progression in TG. However, further validation as a potential surrogate endpoint in clinical trials for the treatment of ABMR is warranted.

Real-life comparison of efficacy and safety profiles of two prolonged-release tacrolimus formulations in de novo kidney transplant recipients: 24 months of follow-up

INTRODUCTION

Calcineurin inhibitors constitute a cornerstone of immunosuppressive therapy in kidney transplant recipients. There are two main formulations of tacrolimus (Tac) which exhibit a prolonged-release mode of action: Advagraf® (MR-4) and Envarsus® (LCPT). However, they are not bioequivalent. Data comparing both once-daily prolonged-release formulations of Tac are insufficient.

OBJECTIVE

The aim of the study was to compare safety and efficacy profiles of once-daily LCPT and MR-4 formulations of tacrolimus in adult kidney transplant recipients.

PATIENTS AND METHODS

An observational, cohort single-center study was performed. One hundred fifteen kidney transplant recipients transplanted between 2016 and 2019 were enrolled to the study (59 vs 56, Envarsus® vs Advagraf®, respectively). Safety and efficacy profiles were assessed.

RESULTS

Patient and graft survival at 12 and 24 months did not differ between the groups. There were no significant differences in serum creatinine at any timepoint. C/D ratio in the LCPT group was significantly higher at 12 and 24 months. Sepsis occurrence was more frequent in MR-4 group at 12 months.

CONCLUSION

Both prolonged-release formulations of tacrolimus are safe and effective in immunosuppressive therapy in kidney transplant recipients.

Nefropatia por IgA e transplante renal segundo a classificação de Oxford

Resumo Introdução: Nefropatia por IgA (NIgA) é a doença glomerular mais comum mundialmente. Sua suscetibilidade e risco para desenvolvimento de doença renal em fase terminal estão relacionados a fatores genéticos e ambientais. A recidiva de NIgA pós-transplante é relativamente comum, impactando na função e sobrevida do enxerto. Este estudo avaliou fatores de risco e características clínicas, laboratoriais e histológicas da recidiva de NIgA pós-transplante, com base na classificação de Oxford. Material e métodos: Estudo de coorte retrospectivo de centro único, incluindo receptores de transplante renal com NIgA pré-transplante comprovada por biópsia, com análise dos fatores de risco e características clínicas, laboratoriais e histológicas dos casos de recidiva de NIgA. Resultados: 53 pacientes preencheram critérios de inclusão e foram incluídos no estudo. A maioria era homem, branco, eutrófico, com idade média de 27 ± 9 anos no diagnóstico de NIgA. Hipertensão arterial sistêmica e proteinúria foram frequentes no período pré-transplante. Quatro receptores (7,5%) apresentaram recidiva de NIgA entre 6-122 meses pós-transplante. Segundo a classificação de Oxford, eles apresentaram altos escores de hipercelularidade mesangial e glomeruloesclerose segmentar nas biópsias de rins nativos. Houve hipercelularidade mesangial em todas as biópsias de enxerto analisadas. Nenhum destes pacientes recebeu imunossupressão de indução. Todos apresentaram falência do enxerto no acompanhamento. Conclusões: Nesta série, houve alta prevalência de hipercelularidade mesangial e glomeruloesclerose segmentar em biópsias de rins nativos, e hipercelularidade mesangial ocorreu em todas as biópsias do enxerto de recidiva da NIgA. Apesar da menor incidência de recidiva de NIgA pós-transplante comparada a relatos anteriores, a progressão para perda do enxerto foi de 100%.

Comparative Analysis of Determinants and Outcome of Early and Late Acute Antibody Mediated Rejection (ABMR)

Introduction

Antibody-mediated rejection (ABMR) is one of the major determinants of graft survival. Although diagnostic precision and treatment options have improved, response to therapy and graft survival has not improved very significantly. The phenotypes of early and late acute ABMR differ in many ways. In this study, we assessed the clinical characteristics, response to therapy, DSA positivity, and outcomes of early and late ABMR.

Methods

During the study period, 69 patients with acute ABMR diagnosed on renal graft histopathology were included with a median follow-up of 10 months after rejection. Recipients were stratified into early acute ABMR (<3 months of transplant; n = 29) and late acute ABMR (>3 months of transplant; n = 40). Graft survival, patient survival, response to therapy, and doubling of serum creatinine were assessed and compared between the two groups.

Results

Baseline characteristics and immunosuppression protocols were comparable between the early and late ABMR groups. Late acute ABMR had an increased risk of doubling of serum creatinine than the early ABMR group (P = 0.002). Graft and patient survival were not statistically different between the two groups. Response to therapy was inferior in the late acute ABMR group (P = 0.00). Pretransplant DSA was present in 27.6% in the early ABMR group. Late acute ABMR was frequently associated with nonadherence or suboptimal immunosuppression and low DSA positivity (15%). Infections such as CMV, bacterial, and fungal infections were similar in the earlier and late ABMR groups.

Conclusion

Late acute ABMR group had a poor response to anti-rejection therapy and also an increased risk of doubling of serum creatinine compared to the early acute ABMR group. There was also a tendency toward increased graft loss in late acute ABMR patients. Late acute ABMR patients are more frequently associated with nonadherence/suboptimal immunosuppression. There was also a low incidence of anti-HLA DSA positivity in late ABMR.

A Banff-based histologic chronicity index is associated with graft loss in patients with a kidney transplant and antibody-mediated rejection

Antibody-mediated rejection (AMR) is the major cause of graft loss in kidney transplant recipients. The Banff classification defines two classes of AMR, active and chronic active but over time this classification has become increasingly complex. To simplify the approach to AMR, we developed activity and chronicity indices based on kidney transplant biopsy findings and examined their association with graft survival in 147 patients with active or chronic active AMR, all of whom had donor-specific antibodies and were treated for AMR. The activity index was determined as the sum of Banff glomerulitis (g), peritubular capillaritis (ptc), arteritis (v) and C4d scores, with a maximum score of 12. The chronicity index was the sum of interstitial fibrosis (ci), tubular atrophy (ct), chronic vasculopathy (cv), and chronic glomerulopathy (cg) scores, the latter doubled, with a maximum score of 15. While the activity index was generally not associated with graft loss, the chronicity index was significantly associated with graft loss with an optimal threshold value of 4 or greater for predicting graft loss. The association of the chronicity index of 4 or greater with graft loss was independent of other parameters associated with graft loss, including the estimated glomerular filtration rate at the time of biopsy, chronic active (versus active) AMR, AMR with de novo (versus persistent/rebound) donor-specific antibodies, Banff (g+ptc) scores, concurrent T cell-mediated rejection and donor-specific antibody reduction post-biopsy. The association of the chronicity index of 4 or greater with graft loss was confirmed in an independent cohort of 61 patients from Necker Hospital, Paris. Thus, our findings suggest that the chronicity index may be valuable as a simplified approach to decision-making in patients with AMR.

Infliximab Induction Lacks Efficacy and Increases BK Virus Infection in Deceased Donor Kidney Transplant Recipients: Results of the CTOT-19 Trial

BACKGROUND

Ischemia-reperfusion (IR) of a kidney transplant (KTx) upregulates TNF α production that amplifies allograft inflammation and may negatively affect transplant outcomes.

METHODS

We tested the effects of blocking TNF peri-KTx via a randomized, double-blind, placebo-controlled, 15-center, phase 2 clinical trial. A total of 225 primary transplant recipients of deceased-donor kidneys (KTx; 38.2% Black/African American, 44% White) were randomized to receive intravenous infliximab (IFX) 3 mg/kg or saline placebo (PLBO) initiated before kidney reperfusion. All patients received rabbit anti-thymocyte globulin induction and maintenance immunosuppression (IS) with tacrolimus, mycophenolate mofetil, and prednisone. The primary end point was the difference between groups in mean 24-month eGFR.

RESULTS

There was no difference in the primary end point of 24-month eGFR between IFX (52.45 ml/min per 1.73 m 2 ; 95% CI, 48.38 to 56.52) versus PLBO (57.35 ml/min per 1.73 m 2 ; 95% CI, 53.18 to 61.52; P =0.1). There were no significant differences between groups in rates of delayed graft function, biopsy-proven acute rejection (BPAR), development of de novo donor-specific antibodies, or graft loss/death. Immunosuppression did not differ, and day 7 post-KTx plasma analyses showed approximately ten-fold lower TNF ( P <0.001) in IFX versus PLBO. BK viremia requiring IS change occurred more frequently in IFX (28.9%) versus PLBO (13.4%; P =0.004), with a strong trend toward higher rates of BKV nephropathy in IFX (13.3%) versus PLBO (4.9%; P =0.06).

CONCLUSIONS

IFX induction therapy does not benefit recipients of kidney transplants from deceased donors on this IS regimen. Because the intervention unexpectedly increased rates of BK virus infections, our findings underscore the complexities of targeting peritransplant inflammation as a strategy to improve KTx outcomes.Clinical Trial registry name and registration number:clinicaltrials.gov (NCT02495077).

Excellent Clinical Long-Term Outcomes of Kidney Transplantation From Small Pediatric Donors (Age ≤ 5 Years) Despite Early Hyperfiltration Injury

Background:

The use of small pediatric donors (age ≤ 5 years and body weight < 20kg) for adult transplant recipients is still regarded controversially in terms of early complications, long-term outcomes, and development of hyperfiltration injury due to body size mismatch.

Objective:

To investigate long-term outcomes of adult renal allograft recipients receiving a kidney from small pediatric donor (SPD) in terms of kidney function and early features of hyperfiltration injury such as histological changes and proteinuria.

Design:

Retrospective, single center study.

Settings:

Transplant center of the University Hospital of Basel, Switzerland.

Patients:

Adult renal allograft recipients receiving a kidney from a small pediatric donor at our center between 2005 and 2017.

Methods:

The outcome of 47 transplants from SPD were compared with 153 kidney transplants from deceased-standard criteria donors (SCD) occurring during the same time period. Incidence of clinical signs of hyperfiltration injury (eg, proteinuria) was investigated. According to our policy, surveillance biopsies were taken at 3 and 6 months post-transplant and were evaluated in terms of signs of hyperfiltration injury.

Results:

At a median follow-up of 2.3 years post-transplant, death-censored graft survival of SPD was comparable to transplants from SCD (94% vs 93%; P = .54). Furthermore, allograft function at last follow-up (estimated glomerular filtration rate–Modification of Diet in Renal Disease) was significantly higher in pediatric transplant (80 vs 55 ml/min/1.73 m2, P = .002). We found histological signs of early hyperfiltration injury in 55% of SPD. There was an equally low proteinuria in both groups during follow-up.

Limitations:

It is a single center and retrospective observational study with small sample size. The outcomes were investigated in a well-selected population of recipients with low body mass index, low immunological risk, and well-controlled hypertension and was not compared with equal selected group of recipients.

Conclusions:

Early histological and clinical signs of hyperfiltration injury in SPD is frequent. Despite the hyperfiltration injury, there is an equal allograft survival and even superior allograft function in SPD compared with SCD during follow-up. This observation supports the concept of high adaptive capacity of pediatric donor kidneys.

Complement Inhibition in Kidney Transplantation: Where Are We Now?

Kidney transplantation is a life-saving strategy for patients with end-stage renal disease. Although progress has been made in the field of transplantation medicine in recent decades in terms of surgical techniques and immunosuppression, long-term organ survival remains a challenge. Also, for reasons of organ shortage, there is an unmet need for new therapeutic approaches to improve the long-term survival of transplants. There is increasing evidence that the complement system plays a crucial role in various pathological events after transplantation, including ischemia/reperfusion injury as well as rejection episodes. The complement system is part of the innate immune system and plays a crucial role in the defense against pathogens but is also involved in tissue homeostasis. However, the tightly regulated complement system can become dysregulated or activated by non-infectious stimuli, then targeting the organism's own cells and leading to inflammatory tissue damage that exacerbates injury. In this review, we will highlight the role of the complement system after transplantation and discuss ongoing and potential therapeutic approaches.

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.

Machine learning-supported interpretation of kidney graft elementary lesions in combination with clinical data

Interpretation of kidney graft biopsies using the Banff classification is still heterogeneous. In this study, extreme gradient boosting classifiers learned from two large training datasets (n = 631 and 304 cases) where the "reference diagnoses" were not strictly defined following the Banff rules but from central reading by expert pathologists and further interpreted consensually by experienced transplant nephrologists, in light of the clinical context. In three external validation datasets (n = 3744, 589, and 360), the classifiers yielded a mean ROC curve AUC (95%CI) of: 0.97 (0.92-1.00), 0.97 (0.96-0.97), and 0.95 (0.93-0.97) for antibody-mediated rejection (ABMR); 0.94 (0.91-0.96), 0.94 (0.92-0.95), and 0.91 (0.88-0.95) for T cell-mediated rejection; >0.96 (0.90-1.00) with all three for interstitial fibrosis-tubular atrophy. We also developed a classifier to discriminate active and chronic active ABMR with 95% accuracy. In conclusion, we built highly sensitive and specific artificial intelligence classifiers able to interpret kidney graft scoring together with a few clinical data and automatically diagnose rejection, with excellent concordance with the Banff rules and reference diagnoses made by a group of experts. Some discrepancies may point toward possible improvements that could be made to the Banff classification.

Glomerular macrophage index (GMI) in kidney transplant biopsies is associated with graft outcome

BACKGROUND

Macrophages in renal transplants have been shown to participate in antibody-mediated rejection and are associated with impaired renal function. We calculated the glomerular macrophage index (GMI) in a large transplant biopsy cohort, studied its quantity in different diagnostic groups, to clarify its possible impact on graft survival.

METHODS

GMI, defined as the mean number of macrophages in 10 glomeruli, was prospectively quantified in 1440 renal transplant biopsies over a 10-year period. The main histopathological diagnoses were grouped into eight disease entities, and GMI was compared to normal transplant biopsies as the reference group. The impact of GMI on graft survival was analyzed.

RESULTS

GMI was highest in chronic (mean 9.4) and active (9.7) antibody mediated rejections (ABMR), mixed rejections (7.6), and recurrent or de novo glomerulonephritis (7.5) and differed significantly from normal transplants (1.3) in almost all diagnostic groups. Hazard ratios for graft loss were significantly increased for all biopsies with GMI ≥1.9 compared to GMI < .5 (reference group) in an adjusted Cox regression model and increased with higher GMI levels. Biopsies with GMI ≥ 4.6 had < 60% 10-year graft-survival, compared to > 80% with GMI ≤ 1.8.

CONCLUSION

GMI levels were predictive of graft loss independent of histological diagnoses and may guide clinicians to decide follow-up and therapy.

Addition of interleukin-6 receptor blockade to carfilzomib-based desensitization in a highly sensitized nonhuman primate model

Sensitized patients, those who had prior exposure to foreign human leukocyte antigens, are transplanted at lower rates due to challenges in finding suitable organs. Desensitization strategies have permitted highly sensitized patients to undergo kidney transplantation, albeit with higher rates of rejection. This study assesses targeting plasma cell and interleukin (IL)-6 receptor for desensitization in a sensitized nonhuman primate kidney transplantation model. All animals were sensitized using two sequential skin transplants from maximally major histocompatibility complex-mismatched donors. Carfilzomib (CFZ)/tocilizumab (TCZ) desensitization (N = 6) successfully decreased donor-specific antibody (DSA) titers and prevented the expansion of B cells compared to CFZ monotherapy (N = 3). Dual desensitization further delayed, but did not prevent humoral rebound, as evidenced by a delayed increase in post-kidney transplant DSA titers. Accordingly, CFZ/TCZ desensitization conferred a significant survival advantage over CFZ monotherapy. A trend toward increased T follicular helper cells was also observed in the dual therapy group along the same timeline as an increase in DSA and subsequent graft loss. Cytomegalovirus reactivation also occurred in the CFZ/TCZ group but was prevented with ganciclovir prophylaxis. In accordance with prior studies of CFZ-based dual desensitization strategies, the addition of IL-6 receptor blockade resulted in desensitization with further suppression of posttransplant humoral response compared to CFZ monotherapy.

Rationale for the IMAGINE study for chronic active antibody-mediated rejection (caAMR) in kidney transplantation

Chronic active antibody-mediated rejection (caAMR) in kidney transplantation is a major cause of late graft loss and despite all efforts to date, there is no proven effective therapy. Indeed, the Transplant Society (TTS) consensus opinion called for a conservative approach optimizing baseline immunosuppression and supportive care focused on blood pressure, blood glucose, and lipid control. This review provides the rationale and early evidence in kidney transplant recipients with caAMR that supported the design of the IMAGINE study whose goal is to evaluate the potential impact of targeting the IL6/IL6R pathway.

Anti-glutathione S-transferase theta 1 antibodies correlate with graft loss in non-sensitized pediatric kidney recipients

Introduction

Immunity to Human leukocyte antigen (HLA) cannot explain all cases of ABMR, nor the differences observed in the outcome of kidney recipients with circulating DSAs endowed with similar biologic characteristics. Thus, increasing attention has recently been focused on the role of immunity to non-HLA antigenic targets.

Methods

We analyzed humoral auto- and alloimmune responses to the non-HLA antigen glutathione S-transferase theta 1 (GSTT1), along with development of de novo (dn)HLA-DSAs, in a cohort of 146 pediatric non-sensitized recipients of first kidney allograft, to analyze its role in ABMR and graft loss. A multiplex bead assay was employed to assess GSTT1 antibodies (Abs).

Results

We observed development of GSTT1 Abs in 71 recipients after transplantation, 16 with MFI &gt; 8031 (4th quartile: Q4 group). In univariate analyses, we found an association between Q4-GSTT1Abs and ABMR and graft loss, suggesting a potential role in inducing graft damage, as GSTT1 Abs were identified within ABMR biopsies of patients with graft function deterioration in the absence of concomitant intragraft HLA-DSAs. HLA-DSAs and GSTT1 Abs were independent predictors of graft loss in our cohort. As GSTT1 Ab development preceded or coincided with the appearance of dnHLA-DSAs, we tested and found that a model with the two combined parameters proved more fit to classify patients at risk of graft loss.

Discussion

Our observations on the harmful effects of GSTT1Abs, alone or in combination with HLA-DSAs, add to the evidence pointing to a negative role of allo- and auto-non-HLA Abs on kidney graft outcome.

Low Incidence of Acute Antibody-Mediated Rejection after HLA Desensitization in Living Donor Kidney Transplant Recipients

Desensitization allows the performance of human leukocyte antigen (HLA)-incompatible transplants. However, the incidence of acute rejection (AR) is high. This study aims to analyze the incidence of AR after transplantation with HLA-incompatible living donors in patients who underwent desensitization. Patients were immunosuppressed with tacrolimus, mycophenolic acid derivatives, and steroids after being desensitized with rituximab, plasma exchange, and/or immunoadsorption with specific cytomegalovirus immunoglobulins. A negative complement-dependent cytotoxicity or flow cytometry crossmatch and a donor-specific antibody titer < 1000 mean fluorescence intensity (MFI) were used to determine desensitization efficacy. A total of 36 patients underwent desensitization, and 27 (75%) were transplanted. After a follow-up of 58 ± 58 months (Min−Max: 0.13−169.5), five episodes of AR occurred: two antibody-mediated and three T-cell-mediated. No differences were found in baseline calculated panel-reactive antibodies (cPRA), class I or II MFI, number of antibodies, or Relative Intensity Scale (RIS) between AR and non-AR patients. Patients with antibody-mediated AR had higher cPRA (NS), MFI class I (p = 0.07) and class II (p = 0.006), and RIS (p = 0.01). The two patients with antibody-mediated AR and one patient with T-cell-mediated AR lost their grafts. In conclusion, the incidence of acute antibody-mediated rejection after desensitization was 7.4%, which occurred early post-transplantation in patients with high MFI and was associated with early graft loss.

WARS1, TYMP and GBP1 display a distinctive microcirculation pattern by immunohistochemistry during antibody-mediated rejection in kidney transplantation

Antibody-mediated rejection (ABMR) is the leading cause of allograft failure in kidney transplantation. Defined by the Banff classification, its gold standard diagnosis remains a challenge, with limited inter-observer reproducibility of the histological scores and efficient immunomarker availability. We performed an immunohistochemical analysis of 3 interferon-related proteins, WARS1, TYMP and GBP1 in a cohort of kidney allograft biopsies including 17 ABMR cases and 37 other common graft injuries. Slides were interpreted, for an ABMR diagnosis, by four blinded nephropathologists and by a deep learning framework using convolutional neural networks. Pathologists identified a distinctive microcirculation staining pattern in ABMR with all three antibodies, displaying promising diagnostic performances and a substantial reproducibility. The deep learning analysis supported the microcirculation staining pattern and achieved similar diagnostic performance from internal validation, with a mean area under the receiver operating characteristic curve of 0.89 (± 0.02) for WARS1, 0.80 (± 0.04) for TYMP and 0.89 (± 0.04) for GBP1. The glomerulitis and peritubular capillaritis scores, the hallmarks of histological ABMR, were the most highly correlated Banff scores with the deep learning output, whatever the C4d status. These novel immunomarkers combined with a CNN framework could help mitigate current challenges in ABMR diagnosis and should be assessed in larger cohorts.

Feasibility and Potential of Transcriptomic Analysis Using the NanoString nCounter Technology to Aid the Classification of Rejection in Kidney Transplant Biopsies

BACKGROUND

Transcriptome analysis could be an additional diagnostic parameter in diagnosing kidney transplant (KTx) rejection. Here, we assessed feasibility and potential of NanoString nCounter analysis of KTx biopsies to aid the classification of rejection in clinical practice using both the Banff-Human Organ Transplant (B-HOT) panel and a customized antibody-mediated rejection (AMR)-specific NanoString nCounter Elements (Elements) panel. Additionally, we explored the potential for the classification of KTx rejection building and testing a classifier within our dataset.

METHODS

Ninety-six formalin-fixed paraffin-embedded KTx biopsies were retrieved from the archives of the ErasmusMC Rotterdam and the University Hospital Cologne. Biopsies with AMR, borderline or T cell-mediated rejections (BLorTCMR), and no rejection were compared using the B-HOT and Elements panels.

RESULTS

High correlation between gene expression levels was found when comparing the 2 chemistries pairwise (r = 0.76-0.88). Differential gene expression (false discovery rate; P  < 0.05) was identified in biopsies diagnosed with AMR (B-HOT: 294; Elements: 76) and BLorTCMR (B-HOT: 353; Elements: 57) compared with no rejection. Using the most predictive genes from the B-HOT analysis and the Element analysis, 2 least absolute shrinkage and selection operators-based regression models to classify biopsies as AMR versus no AMR (BLorTCMR or no rejection) were developed achieving an receiver-operating-characteristic curve of 0.994 and 0.894, sensitivity of 0.821 and 0.480, and specificity of 1.00 and 0.979, respectively, during cross-validation.

CONCLUSIONS

Transcriptomic analysis is feasible on KTx biopsies previously used for diagnostic purposes. The B-HOT panel has the potential to differentiate AMR from BLorTCMR or no rejection and could prove valuable in aiding kidney transplant rejection classification.

Tacrolimus Monotherapy is Safe in Immunologically Low-Risk Kidney Transplant Recipients: A Randomized-Controlled Pilot Study

In this randomized-controlled pilot study, the feasibility and safety of tacrolimus monotherapy in immunologically low-risk kidney transplant recipients was evaluated [NTR4824, www.trialregister.nl]. Low immunological risk was defined as maximal 3 HLA mismatches and the absence of panel reactive antibodies. Six months after transplantation, recipients were randomized if eGFR >30 ml/min, proteinuria <50 mg protein/mmol creatinine, no biopsy-proven rejection after 3 months, and no lymphocyte depleting therapy given. Recipients were randomized to tacrolimus/mycophenolate mofetil (TAC/MMF) or to taper and discontinue MMF at month 9 (TACmono). 79 of the 121 recipients were randomized to either TACmono (n = 38) or TAC/MMF (n = 41). Mean recipient age was 59 years and 59% received a living donor transplant. The median follow-up was 62 months. After randomization, 3 TACmono and 4 TAC/MMF recipients experienced a biopsy-proven rejection. At 5 years follow-up, patient survival was 84% in TACmono versus 76% in TAC/MMF with death-censored graft survival of 97% for both groups and no differences in eGFR and proteinuria. Eleven TACmono recipients had an infectious episode versus 22 TAC/MMF recipients (p < 0.03). Donor-specific anti-HLA antibodies were not detected during follow-up in both groups. Tacrolimus monotherapy in selected immunologically low-risk kidney transplant recipients appears safe and reduces the number of infections.

The Immunohistochemical Expression of the Von Willebrand Factor: A Potential Tool to Predict Kidney Allograft Outcomes

Few reports assessed endothelial activation biomarkers in kidney allograft biopsies using immunohistochemistry. This retrospective cohort study evaluated the association between posttransplant outcomes and the immunohistochemistry expression of Caveolin-1, Von Willebrand Factor (Vwf), and T-Cadherin in for-cause biopsies diagnosed as interstitial fibrosis and tubular atrophy of unknown etiology. Samples with antibody-mediated changes were excluded. The patients were followed for 3 years after the biopsy or until graft loss/death. Seventy-one (71) samples from 66 patients were included. Eighteen (25.4%) patients lost their grafts, mainly due to chronic rejection (33.3%). Caveolin-1 and T-Cadherin were not associated with graft loss. Vwf had good accuracy in predicting graft failure (AUC 0.637, 95% CI 0.486 to 0.788 P=0.101). The presence of more than 10% of Vwf positivity in the microvasculature (Vwf >10%) was associated with reduced death-censored graft survival (58.2% vs. 85.4% P=0.006), and this result was also observed in the subgroup presenting mild interstitial fibrosis (ci=1) (65.7% vs. 88.6% P=0.033). The multivariate analysis showed that Vwf >10% was an independent risk factor for graft loss (HR=2.88, 95% CI 1.03 to 8.02 P=0.043). In conclusion, Vwf might be an additional tool to predict allograft outcomes in kidney transplant recipients with interstitial fibrosis and tubular atrophy of unknown etiology, probably reflecting immune endothelial activation.

Phosphorylation of S6RP in peritubular capillaries of kidney grafts and circulating HLA donor-specific antibodies

Antibody-mediated rejection (ABMR) caused by donor-specific HLA-antibodies (DSA) is a mediator of allograft loss after kidney transplantation (KT). DSA can activate microvascular endothelium damage through the mTOR pathway. In this study we assessed the mTOR pathway activation by DSA in KT with ABMR (ABMR + DSA+) compared to controls (ABMR−DSA−), biopsies with ABMR changes without DSA (ABMR + DSA−) and DSA without ABMR changes (ABMR−DSA+), and the potential modulation by mTOR inhibitors (mTORi). We evaluated 97 biopsies: 31 ABMR + DSA+, 33 controls ABMR-DSA−, 16 ABMR + DSA−, and 17 ABMR-DSA+ cases. Regarding immunosuppression of full ABMR + DSA+ and controls, 21 biopsies were performed under mTORi treatment (11 of them ABMR + DSA+ cases) and 43 without mTORi (20 of them ABMR + DSA+) so as to explore its effect on the mTOR pathway. Biopsies were stained for C4d, Ki67, and phosphorylated (p) S6RP, ERK, and mTOR by immunohistochemistry. Labeling was graded according to peritubular capillary staining. ABMR biopsies showed significantly higher C4d, p-S6RP, and Ki67 staining in peritubular capillaries (PTC) compared to controls, and light differences in p-ERK or p-mTOR. mTORi treatment did not modify p-S6RP, p-mTOR, and p-ERK staining. Diffuse p-S6RP in PTC in the biopsies significantly associated with circulating HLA-DSA independently of graft rejection, and with worse death-censored graft survival. These findings suggest that activation of endothelium through the mTOR pathway evidence different mechanisms of damage in ABMR + DSA+ and ABMR + DSA− despite similar histological injury.

Belatacept-Based Maintenance Immunosuppression Controls the Post-Transplant Humoral Immune Response in Highly Sensitized Nonhuman Primates

Preexisting donor-specific antibodies (DSA) to MHC antigens increase the risk of antibody-mediated rejection (AMR) in sensitized transplant recipients and reduces graft survival. Pretransplant desensitization with costimulation blockade and proteasome inhibition has facilitated transplantation in our preclinical nonhuman primate (NHP) model. However, long-term graft survival is limited by rebound of DSA after transplantation. In this study, we performed kidney transplants between highly sensitized, maximally MHC-mismatched NHPs (n=14). At kidney transplantation, primates received T cell depletion with rhesus-specific anti-thymocyte globulin (rhATG; n=10) or monoclonal anti-CD4 and anti-CD8 antibodies (n=4). Maintenance immunosuppression consisted of belatacept and tacrolimus (n=5) or belatacept and rapamycin (n=9) with steroids. Rebound of DSA post-kidney transplantation was significantly reduced compared with maintenance immunosuppression with tacrolimus, mycophenolate, and steroids. Protocol lymph node biopsy specimens showed a decrease in germinal center activity, with low frequencies of T follicular helper cells and class-switched B cells after kidney transplantation. Combined belatacept and rapamycin was superior in controlling viral reactivation, enabling weaning of ganciclovir prophylaxis. Tacrolimus was associated with increased morbidity that included cytomegalovirus and parvovirus viremia and post-transplant lymphoproliferative disorder. All primates in the tacrolimus/belatacept group failed discontinuation of antiviral therapy. Overall, belatacept-based immunosuppression increased AMR-free graft survival by controlling post-transplant humoral responses in highly sensitized NHP recipients and should be further investigated in a human clinical trial.

Impact of Glomerulitis on Long-term Outcomes After Kidney Transplantation

The Banff classification scheme provides a framework for interpreting transplant kidney biopsies and has undergone various updates in the past 2 decades especially related to antibody-mediated rejection. The clinical significance of early glomerulitis seen within 4 mo on protocol biopsies has received limited attention. We hypothesized that early glomerulitis seen on protocol biopsies will lead to significant adverse outcomes as assessed by histopathology and allograft outcome.

Function and longevity of renal grafts from high-KDPI donors

BACKGROUND

High kidney-donor profile index (KDPI) kidneys have a shorter survival than grafts with lower KDPI values. It is still unclear, however, whether their shorter longevity depends on an inferior baseline function, faster functional decline, or the combination of both.

METHODS

We analyzed the estimated glomerular filtration rate (eGFR) of 605 consecutive recipients of deceased donor kidney transplants (KT) at 1, 3, 6, 12, 18, 24, 36, 48, and 60 months. Comparisons were performed among four groups based on KDPI quartile: Group I-KDPI ≤ 25% (n = 151), Group II-KDPI 26-50% (n = 182), Group III-KDPI 51-75% (n = 176), and Group IV-KDPI 〉 75% (n = 96). Linear mixed model analysis was subsequently used to assess whether KDPI was independently associated with the decline in eGFR during the first 5-years after KT. We also analyzed the incidence of delayed graft function (DGF), rejection within the first year after KT, patient survival, graft survival, and death censored graft survival based on KDPI group.

FINDINGS

High-KDPI grafts had lower eGFR immediately after KT, had a higher incidence of DGF and rejection. However, there were no signifcant differences in the adjusted rate (slope) of decline in eGFR among the four KDPI groups (P = .06). Although patient survival was signigicantly lower for recipients of high-KDPI grafts, death-censored graft survival was similar among the four KDPI groups (P = .33).

CONCLUSIONS

The shorter functional survival of high-KDPI grafts seems to be due to their lower baseline eGFR rather than a more rapid functional decline after KT.

Impacts of dosing and drug withdrawal period on tacrolimus-based triple therapy in a non-human primate renal transplantation model

Non-human primate (NHP) renal transplantation models are widely used vivo models for researching new immunosuppressive therapies including allograft tolerance strategies. To enroll animals into a tolerance study, an immunosuppressive regimen that efficiently establishes stable renal function in NHPs is needed. Here, we assessed the effect of triple therapy comprising 2.0 mg/kg tacrolimus, mycophenolate mofetil and a steroid and its success rate for achieving stable renal function. In addition, to predict the pathophysiological consequences of withdrawing immunosuppressants, an indispensable process after induction of tolerance, we also assessed changes in the stable renal state maintained by triple therapy after drug withdrawal. Six cynomolgus monkeys were used. The median survival time was >176 days over the dosing period and 45 days after drug withdrawal. The triple therapy successfully induced stable graft function without calcineurin inhibitor nephrotoxicity in three of six recipients, although adopting trough-dependent tacrolimus dose adjustment rather than a preset dose regimen could improve on the present strategy. Further, drug withdrawal led to deterioration of renal function, de novo donor specific antibody production and increased the memory/naïve T cell ratio within two weeks post drug withdrawal. We expect that these findings contribute to establish one of the choices for animal model for evaluating future tolerance therapy for renal transplantation.

PIRCHE-II scores prove useful as a predictive biomarker among kidney transplant recipients with rejection: An analysis of indication and follow-up biopsies

Background

Indication biopsies for deterioration of kidney allograft function often require follow-up biopsies to assess treatment response or lack of improvement. Immune-mediated injury, namely borderline rejection (BLR), T-cell mediated rejection (TCMR), or antibody-mediated rejection (ABMR), results from preformed or de novo alloreactivity due to donor and recipient HLA-mismatches. The impact of HLA-mismatches on alloreactivity is determined by highly immunogenic HLA-epitopes.

Methods

We analyzed 123 kidney transplant recipients (KTRs) from 2009 to 2019 who underwent a first indication and a follow-up biopsy. KTRs were divided into three groups according to the first biopsy: No rejection (NR)/BLR (n=68); TCMR (n=21); ABMR (n=34). The HLA-derived epitope-mismatches were calculated using the Predicted Indirectly Recognizable HLA-Epitopes (PIRCHE-II) algorithm.

Results

Group NR/BLR: KTRs with higher total PIRCHE-II scores were more likely to develop TCMR in the follow-up biopsy (p=0.031). Interestingly, these differences were significant for both HLA-class I- (p=0.017) and HLA-class II-derived (p=0.017) PIRCHE-II scores. Group TCMR: KTRs with ongoing TCMR in the follow-up biopsy were more likely to show higher total PIRCHE-II scores (median 101.50 vs. 74.00). Group ABMR: KTRs with higher total PIRCHE-II scores were more likely to show an increase in the microvascular inflammation score in the follow-up biopsy. This difference was more pronounced for the HLA-class II-derived PIRCHE-II scores (median 70.00 vs. 31.76; p=0.086).

Conclusions

PIRCHE-II scores may prove useful as a biomarker to predict the histopathological changes of immune-related injury from a first indication to a follow-up biopsy. This immunological risk stratification may contribute to individualized treatment strategies.

Genome-wide association study biomarkers in T-cell mediated rejection: selective effect according to the Banff classification

BACKGROUND

A genome-wide association study (GWAS) in kidney transplant recipients reported the association of two polymorphisms located in the PTPRO gene and upstream of the CCDC67 (DEUP1) gene with increased risk of acute T cell-mediated rejection (TCMR). We aimed at replicating the assessment of mentioned associations and additionally ascertaining the influence of treatment and clinical features of the patients.

METHODS

The polymorphisms, PTPRO-rs7976329 and CCDC67-rs10765602 were genotyped by TaqMan chemistry in 641 consecutive kidney transplant recipients. The diagnosis of rejection was confirmed by biopsy and categorized according to the Banff classification. Associations were evaluated by Chi-square test or Fisher's exact test when necessary and multivariate logistic regression.

RESULTS

Considering the GWAS study we only replicated the association of the PTPRO-rs7976329*C allele in the Banff grade < II subjects. However, the homozygous mutant genotypes of both polymorphism seemed to increase the risk of TCMR Banff grade < II in the overall cohort and after stratification by Thymoglobulin induction therapy. In the multivariate analysis, we confirmed the association of PTPRO-rs7976329 with TCMR Banff grade < II, independently of the Thymoglobulin induction therapy and of CCDC67-rs10765602 only in the group of patients not receiving Thymoglobulin induction therapy. No association of these polymorphisms with TCMR Banff grade ≥ II was observed in either the overall cohort or in the subgroups stratified by Thymoglobulin therapy.

CONCLUSIONS

Our study shows that the increased risk of TCMR related to polymorphisms PTPRO-rs7976329 and CCDC67-rs10765602 previously reported in a GWAS was replicated only in homozygous patients who presented TCMR Banff grade < II and for the minor allele of either polymorphism.

[Current insights on monitoring of renal transplants-Banff and beyond]

Renal transplantation represents the best treatment for end-stage renal disease. Much effort has been invested in improvement of longevity of the transplanted organ including a comprehensive and regularly updated histological scoring system (Banff classification) for surveillance; however, survival of transplanted kidneys is still limited to median 15 years. Molecular analyses have increased the understanding of damaging mechanisms within the transplant, especially antibody-mediated rejection, which can be difficult to identify using histological methods. Changes in the Banff classification necessitate to reclassify biopsies included in studies according to current consensus. Digital and molecular innovations as well as new immunologic mechanisms are anticipated.

The Role of Fc Gamma Receptors in Antibody-Mediated Rejection of Kidney Transplants

For the past decades, complement activation and complement-mediated destruction of allograft cells were considered to play a central role in anti-HLA antibody-mediated rejection (AMR) of kidney transplants. However, also complement-independent mechanisms are relevant in the downstream immune activation induced by donor-specific antibodies, such as Fc-gamma receptor (FcγR)-mediated direct cellular activation. This article reviews the literature regarding FcγR involvement in AMR, and the potential contribution of FcγR gene polymorphisms to the risk for antibody mediated rejection of kidney transplants. There is large heterogeneity between the studies, both in the definition of the clinical phenotypes and in the technical aspects. The study populations were generally quite small, except for two larger study cohorts, which obviates drawing firm conclusions regarding the associations between AMR and specific FcγR polymorphisms. Although FcγR are central in the pathophysiology of AMR, it remains difficult to identify genetic risk factors for AMR in the recipient’s genome, independent of clinical risk factors, independent of the donor-recipient genetic mismatch, and in the presence of powerful immunosuppressive agents. There is a need for larger, multi-center studies with standardised methods and endpoints to identify potentially relevant FcγR gene polymorphisms that represent an increased risk for AMR after kidney transplantation.

Granulocyte colony-stimulating factor with or without immunosuppression reduction in neutropenic kidney transplant recipients

Neutropenia post-kidney transplantation is associated with adverse graft and patient outcomes. We aimed to analyze the effect of granulocyte colony-stimulating factor (G-CSF) use with and without immunosuppression reduction on graft outcomes in neutropenic recipients. In this retrospective cohort study, we identified 120 recipients with neutropenia, within the first-year post-transplant. Of these, 45.0% underwent no intervention, 17.5% had immunosuppression reduced, 18.3% were only given G-CSF, and 19.2% had both interventions. Overall, 61 patients experienced the composite outcome of de-novo DSA, biopsy-proven acute rejection, and all-cause graft failure and the cumulative incidence of this outcome did not vary by any of the four interventions (p = 0.93). When stratifying the cohort by G-CSF use alone, those who received G-CSF were more likely to have had severe neutropenia (<500/mm³ :51.1%vs.12.0%, p<0.001), and immunosuppression reduction (51.1%vs.28.0%, p = 0.003). However, the composite outcome was not different in the G-CSF and no G-CSF cohort (53.3%vs.49.3%, p = 0.67), and in a multivariate model, G-CSF use was not associated with this outcome (aHR = 1.18, 95%CI:0.61-2.30). However, a trend towards higher DSA production was noted in the G-CSF cohort (87.5%vs.62.2%) and this observation warrants prospective evaluation. Overall, we conclude that G-CSF use with or without immunosuppression reduction was not associated with graft outcomes. This article is protected by copyright. All rights reserved.

Effects of Bacterial Urinary Tract Infection on Clinical Outcome and Survival of Kidney Transplant Patients

BACKGROUND

There is no consensus on whether the development of urinary tract infections (UTIs) leads to high mortality or graft loss in kidney transplant patients. A high incidence of multidrug resistant (MDR) infections was observed worldwide and is associated with these complications. The aim of this study was to analyze the effects of UTIs on the clinical outcome and survival in kidney transplant patients.

METHODS

This retrospective study evaluated 601 kidney transplant patients who were categorized as follows: group 1 (G1) patients without a UTI, group 2 (G2) patients with a UTI, and group 3 (G3) recipients with a recurrent UTI. Patients were followed up for at least 1 year after transplantation. Graft survival, risk of graft loss, and risk of developing a UTI were analyzed by the Kaplan-Meier method, Cox regression, and logistic regression methods, respectively. Differences with P < .05 were considered statistically significant.

RESULTS

The proportion of rejection episodes was higher in G3 (32.35%) than in G1 (20.89%) and G2 (21.88%) (P < .001). The graft survival after the 10-year follow-up was better in G1 (73.29%) than in G3 (61.62%) (P = .019). UTI recurrent episodes increased the risk of graft loss >2.5-fold. Women and those who received a kidney from a deceased donor (DD) were at risk of at least 1 UTI event during follow-up. A greater proportion of MDR infections was observed in G3 than in G2 (P < .001).

CONCLUSIONS

The risk factors for developing a UTI were female sex, receiving a DD kidney, susceptibility to other infections, episodes of rejection, and delayed graft function. Moreover, a UTI, especially a recurrent UTI, was an important risk factor for allograft loss.

Tacrolimus CYP3A Single-Nucleotide Polymorphisms and Preformed T- and B-Cell Alloimmune Memory Improve Current Pretransplant Rejection-Risk Stratification in Kidney Transplantation

Achieving fast immunosuppression blood exposure after kidney transplantation is key to abrogating both preformed and de novo anti-donor humoral and cellular alloresponses. However, while tacrolimus (TAC) is the cornerstone immunosuppressant inhibiting adaptive alloimmunity, its blood exposure is directly impacted by different single-nucleotide polymorphisms (SNPs) in CYP3A TAC-metabolizing enzymes. Here, we investigated how functional TAC-CYP3A genetic variants (CYP3A4*22/CYP3A5*3) influence the main baseline clinical and immunological risk factors of biopsy-proven acute rejection (BPAR) by means of preformed donor-specific antibodies (DSAs) and donor-specific alloreactive T cells (DSTs) in a large European cohort of 447 kidney transplants receiving TAC-based immunosuppression. A total of 70 (15.7%) patients developed BPAR. Preformed DSAs and DSTs were observed in 12 (2.7%) and 227 (50.8%) patients, respectively. According to the different CYP3A4*22 and CYP3A5*3 functional allele variants, we found 4 differential new clusters impacting fasting TAC exposure after transplantation; 7 (1.6%) were classified as high metabolizers 1 (HM1), 71 (15.9%) as HM2, 324 (72.5%) as intermediate (IM), and 45 (10.1%) as poor metabolizers (PM1). HM1/2 showed significantly lower TAC trough levels and higher dose requirements than IM and PM (p < 0.001) and more frequently showed TAC underexposure (<5 ng/ml). Multivariate Cox regression analyses revealed that CYP3A HM1 and IM pharmacogenetic phenotypes (hazard ratio (HR) 12.566, 95% CI 1.99–79.36, p = 0.007, and HR 4.532, 95% CI 1.10–18.60, p = 0.036, respectively), preformed DSTs (HR 3.482, 95% CI 1.99–6.08, p < 0.001), DSAs (HR 4.421, 95% CI 1.63–11.98, p = 0.003), and delayed graft function (DGF) (HR 2.023, 95% CI 1.22–3.36, p = 0.006) independently predicted BPAR. Notably, a significant interaction between T-cell depletion and TAC underexposure was observed, showing a reduction of the BPAR risk (HR 0.264, 95% CI 0.08–0.92, p = 0.037). Such variables except for DSAs displayed a higher predictive risk for the development of T cell-mediated rejection (TCMR). Refinement of pretransplant monitoring by incorporating TAC CYP3A SNPs with preformed DSAs as well as DSTs may improve current rejection-risk stratification and help induction treatment decision-making.

Decoy Receptor 3 Suppresses T-Cell Priming and Promotes Apoptosis of Effector T-Cells in Acute Cell-Mediated Rejection: The Role of Reverse Signaling

Background

Decoy receptor 3 (DcR3) belongs to the tumor necrosis factor (TNF) receptor superfamily and neutralizes TNF ligands, including FasL and TRAIL, to prevent T activation during T-cell priming. However, the cellular mechanisms underlying acute cell-mediated rejection (ACMR) remain unknown.

Methods

We generated DcR3 transgenic (Tg) mice and mice with high DcR3 expression (HDE) to study both in vivo and in vitro. FasR RNA knockdown in immortalized CD4⁺CD8⁺ T-cells was used to survey the role of DcR3 on FasR/Fas-associated protein with death domain (FADD)/caspase 8 pathway and its cross-link to TNF receptor-associated factor 1 (TNFR1)-associated death domain protein (TRADD) in suppressing TNFR1. TNF/TRADD knockout mice were used to show the importance of TNF adaptor protein.

Results

DcR3.Fc suppressed C57BL/6 female T-cell activation and transformation into CD4⁺CD69⁺, CD4⁺CD44⁺, and CD4⁺CD25⁺Foxp3⁺ when compared with isotype IgG1 and its co-treatment with FasL/TRAIL after exposing to bone marrow-derived dendritic cells (BMDCs) that carried alloantigen with male H-Y and minor antigenic determinant. Interleukin-17 and interferon-γ productions by BMDC-activated T-cells were lowered after co-treating with DcR3.Fc. DcR3.Fc induced effector T-cells (Teffs) and was susceptible to FasR-mediated apoptosis through the FADD/TRADD/caspase 8 pathway. After exposing to DcR3.Fc, TRADD was silenced, likely turning down the inflammatory response. The systemic effects of DcR3 Tg mice and HDE phenotype induced by the promoter of cytomegalovirus not only attenuated ACMR severity but also ameliorated the high serum creatinine and blood urea nitrogen levels even with high T-cell exposure frequencies. Besides this, DcR3 has minor biological effects on both MHC-matched and MHC-mismatched models.

Conclusions

High DcR3 doses protect renal tubular epithelial cells from acute T-cell attack during the T-cell priming stage via interfering with TNF ligand-mediated reverse signaling and possibly promoting Teff apoptosis through FasR upregulation. Our findings supported that the decoy receptor is involved in T-cell modulation in kidney transplant rejection.

Proposed Definitions of Antibody-Mediated Rejection for Use as a Clinical Trial Endpoint in Kidney Transplantation

Antibody-mediated rejection (AMR) is caused by antibodies that recognize donor human leukocyte antigen (HLA) or other targets. As knowledge of AMR pathophysiology has increased, a combination of factors is necessary to confirm the diagnosis and phenotype. However, frequent modifications to the AMR definition have made it difficult to compare data and evaluate associations between AMR and graft outcome. The present paper was developed following a Broad Scientific Advice request from the European Society for Organ Transplantation (ESOT) to the European Medicines Agency (EMA), which explored whether updating guidelines on clinical trial endpoints would encourage innovations in kidney transplantation research. ESOT considers that an AMR diagnosis must be based on a combination of histopathological factors and presence of donor-specific HLA antibodies in the recipient. Evidence for associations between individual features of AMR and impaired graft outcome is noted for microvascular inflammation scores ≥2 and glomerular basement membrane splitting of >10% of the entire tuft in the most severely affected glomerulus. Together, these should form the basis for AMR-related endpoints in clinical trials of kidney transplantation, although modifications and restrictions to the Banff diagnostic definition of AMR are proposed for this purpose. The EMA provided recommendations based on this Broad Scientific Advice request in December 2020; further discussion, and consensus on the restricted definition of the AMR endpoint, is required.

Outcome of ABO-incompatible kidney transplantation using a modified desensitization protocol without plasmapheresis

OBJECTIVES

Several controversies regarding desensitization strategies for successful ABO-incompatible (ABOi) kidney transplantation still exist. This study aimed to investigate whether pretransplant anti-A/B antibody removal is mandatory in an ABOi kidney transplant recipient with low baseline isoagglutinin titers.

METHODS

We adopted a modified desensitization protocol with two doses of rituximab (RTX, 100 mg/body) without pretransplant antibody removal for ABOi kidney transplant recipients with a titer of ≤1:64 (group A; n = 35) and investigated the feasibility of this protocol by comparing it with the clinical outcomes of patients undergoing standard pretransplant plasmapheresis (group B; n = 21).

RESULTS

There was no significant difference in the rate of antibody-mediated rejection within the first month after transplantation between the two groups (11.4% in group A vs. 2% in group B, p = 0.6019). Moreover, no differences were observed in the short- and long-term graft outcomes between the groups. However, two major critical acute antibody-mediated events occurred in group A; one patient lost the graft due to hyperacute rejection, and the other patient developed thrombotic microangiopathy after surgery. Risk factors predicting these perioperative complications were not identified.

CONCLUSIONS

We conclude that not only B-cell depletion using RTX but also pretransplant antibody removal is still recommended even for patients with low isoagglutinin titers. In addition, a new diagnostic tool is needed for accurate risk stratification.

Long term tolerability and clinical outcomes associated with tocilizumab in the treatment of refractory antibody mediated rejection (AMR) in pediatric renal transplant recipients

BACKGROUND

Treatment options for antibody-mediated rejection (AMR) are limited. Recent studies have shown that inhibition of interleukin-6 (IL-6)/interleukin-6 receptor (IL-6R) signaling can reduce inflammation and slow AMR progression.

METHODS

We report our experience using monthly tocilizumab (anti-IL6R) in 25 pediatric renal transplant recipients with AMR, refractory to IVIg/Rituximab. From January 2013 to June 2019, a median (IQR) of 12 (6.019.0) doses of tocilizumab were given per patient. Serial assessments of renal function, biopsy findings, and HLA DSA (by immunodominant HLA DSA [iDSA] and relative intensity score [RIS]) were performed.

RESULTS

Median (IQR) time from transplant to AMR was 41.4 (24.367.7) months, and time from AMR to first tocilizumab was 10.6 (8.317.6) months. At median (IQR) follow up of 15.8 (8.435.7) months post-tocilizumab initiation, renal function was stable except for 1 allograft loss. There was no significant decrease in iDSA or RIS. Follow up biopsies showed reduction in peritubular capillaritis (p = .015) and C4d scoring (p = .009). The most frequent adverse events were cytopenias.

CONCLUSIONS

Tocilizumab in pediatric patients with refractory AMR was well tolerated and appeared to stabilize renal function. The utility of tocilizumab in the treatment of AMR in this population should be further explored.

Notch3 expression in capillary pericytes predicts worse graft outcome in human renal grafts with antibody-mediated rejection

Microvasculature consisting of endothelial cells and pericytes is the main site of injury during antibody-mediated rejection (ABMR) of renal grafts. Little is known about the mechanisms of activation of pericytes in this pathology. We have found recently that activation of Notch3, a mediator of vascular smooth muscle cell proliferation and dedifferentiation, promotes renal inflammation and fibrosis and aggravates progression of renal disease. Therefore, we studied the pericyte expression of Notch3 in 49 non-selected renal graft biopsies (32 for clinical cause, 17 for graft surveillance). We analysed its relationship with patients' clinical and morphological data, and compared with the expression of partial endothelial mesenchymal transition (pEndMT) markers, known to reflect endothelial activation during ABMR. Notch3 was de novo expressed in pericytes of grafts with ABMR, and was significantly correlated with the microcirculation inflammation scores of peritubular capillaritis and glomerulitis and with the expression of pEndMT markers. Notch3 expression was also associated with graft dysfunction and proteinuria at the time of biopsy and in the long term. Multivariate analysis confirmed pericyte expression of Notch3 as an independent risk factor predicting graft loss. These data suggest that Notch3 is activated in the pericytes of renal grafts with ABMR and is associated with poor graft outcome.