Publications by authors named "Maarten Naesens"

148 Publications

Editorial: Changing of the Guard at Transplant International.

Transpl Int 2021 Feb 9. Epub 2021 Feb 9.

Leuven, Belgium.

Transplant International has enjoyed the status of a respected journal in the field of organ transplantation under the 5-year leadership of co-editors-in-chief Thomas Wekerle and Rainer Oberbauer. Wholehearted thanks are due to these two formidable physician-scientists who have succeeded to maintain a high level of scientific quality and increased the impact factor of the journal that was entrusted to them.
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http://dx.doi.org/10.1111/tri.13843DOI Listing
February 2021

A 2020 Banff Antibody Mediated Injury Working Group examination of international practices for diagnosing antibody mediated rejection in kidney transplantation.

Transpl Int 2021 Jan 10. Epub 2021 Jan 10.

Division of Nephrology/Transplant Nephrology, Johns Hopkins University, Baltimore, MD, USA.

The Banff antibody mediated rejection (ABMR) classification is vulnerable to misinterpretation, but the reasons are unclear. To better understand this vulnerability, we evaluated how ABMR is diagnosed in practice. To do this, the Banff Antibody-Mediated Injury Workgroup electronically surveyed an international cohort of nephrologists/surgeons (n=133) and renal pathologists (n=99). Most providers (97%) responded that they use the Banff ABMR classification at least sometimes, but DSA information is often not readily available. Only 41.1%(55/133) of nephrologists/surgeons and 19.2%(19/99) of pathologists reported that they always have DSA results when the biopsy is available. Additionally, only 19.6%(26/133) of nephrologists/surgeons responded that non-HLA antibody or molecular transcripts are obtained when ABMR histologic features are present but DSA is undetected. Several respondents agreed that histologic features concerning for ABMR in the absence of DSA and/or C4d are not well accounted for in the current classification [31.3% (31/99) pathologists and 37.6%(50/133) nephrologist/surgeons]. The Banff ABMR classification appears widely accepted, but efforts to improve the accessibility of DSA information for the multidisciplinary care team are needed. Further clarity is also needed in Banff ABMR nomenclature to account for the spectrum of ABMR and for histologic features suspicious for ABMR when DSA is absent.
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http://dx.doi.org/10.1111/tri.13813DOI Listing
January 2021

Revisiting the changes in the Banff Classification for antibody-mediated rejection after kidney transplantation.

Am J Transplant 2020 Dec 31. Epub 2020 Dec 31.

Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium.

The Banff classification for antibody-mediated rejection (ABMR) has undergone important changes, mainly by inclusion of C4d-negative ABMR in Banff'13 and elimination of suspicious ABMR (sABMR) with the use of C4d as surrogate for HLA-DSA in Banff'17. We aimed to evaluate the numerical and prognostic repercussions of these changes in a single-centre cohort study of 949 single kidney transplantations, comprising 3662 biopsies that were classified according to the different versions of the Banff classification. Overall, the number of ABMR and sABMR cases increased from Banff'01 to Banff'13. In Banff'17, 248/292 sABMR biopsies were reclassified to No ABMR, and 44/292 to ABMR. However, reclassified sABMR biopsies had worse and better outcome than No ABMR and ABMR , which was mainly driven by the presence of microvascular inflammation and absence of HLA-DSA, respectively. Consequently, the discriminative performance for allograft failure was lowest in Banff'17, and highest in Banff'13. Our data suggest that the clinical and histological heterogeneity of ABMR is inadequately represented in a binary classification system. This study provides a framework to evaluate updates of the Banff classification and assess the impact of proposed changes on the number of cases and risk stratification. Two alternative classifications introducing an intermediate category are explored.
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http://dx.doi.org/10.1111/ajt.16474DOI Listing
December 2020

Assessment of the Utility of Kidney Histology as a Basis for Discarding Organs in the United States: A Comparison of International Transplant Practices and Outcomes.

J Am Soc Nephrol 2021 Feb 15;32(2):397-409. Epub 2020 Dec 15.

Université de Paris, Institut National de la Santé et de la Recherche Médicale U970, Paris Translational Research Centre for Organ Transplantation, Paris, France

Background: Many kidneys donated for transplant in the United States are discarded because of abnormal histology. Whether histology adds incremental value beyond usual donor attributes in assessing allograft quality is unknown.

Methods: This population-based study included patients who received a deceased donor kidney that had been biopsied before implantation according to a prespecified protocol in France and Belgium, where preimplantation biopsy findings are generally not used for decision making in the allocation process. We also studied kidneys that had been acquired from deceased United States donors for transplantation that were biopsied during allocation and discarded because of low organ quality. Using donor and recipient characteristics, we fit multivariable Cox models for death-censored graft failure and examined whether predictive accuracy (C index) improved after adding donor histology. We matched the discarded United States kidneys to similar kidneys transplanted in Europe and calculated predicted allograft survival.

Results: In the development cohort of 1629 kidney recipients at two French centers, adding donor histology to the model did not significantly improve prediction of long-term allograft failure. Analyses using an external validation cohort from two Belgian centers confirmed the lack of improved accuracy from adding histology. About 45% of 1103 United States kidneys discarded because of histologic findings could be accurately matched to very similar kidneys that had been transplanted in France; these discarded kidneys would be expected to have allograft survival of 93.1% at 1 year, 80.7% at 5 years, and 68.9% at 10 years.

Conclusions: In this multicenter study, donor kidney histology assessment during allocation did not provide substantial incremental value in ascertaining organ quality. Many kidneys discarded on the basis of biopsy findings would likely benefit United States patients who are wait listed.
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http://dx.doi.org/10.1681/ASN.2020040464DOI Listing
February 2021

Does the definition of chronic active T cell-mediated rejection need revisiting?

Am J Transplant 2020 Nov 29. Epub 2020 Nov 29.

Department of Laboratory Medicine & Pathology, University of Alberta, Edmonton, Canada.

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http://dx.doi.org/10.1111/ajt.16419DOI Listing
November 2020

Missing Self-Induced Activation of NK Cells Combines with Non-Complement-Fixing Donor-Specific Antibodies to Accelerate Kidney Transplant Loss in Chronic Antibody-Mediated Rejection.

J Am Soc Nephrol 2021 Feb 25;32(2):479-494. Epub 2020 Nov 25.

International Center of Infectiology research (CIRI), French Institute of Health and Medical Research (INSERM) Unit 1111, Claude Bernard University Lyon I, National Center for Scientific Research (CNRS) Mixed University Unit (UMR) 5308, Ecole Normale Supérieure de Lyon, University of Lyon, Lyon, France

Background: Binding of donor-specific antibodies (DSAs) to kidney allograft endothelial cells that does not activate the classic complement cascade can trigger the recruitment of innate immune effectors, including NK cells. Activated NK cells contribute to microvascular inflammation leading to chronic antibody-mediated rejection (AMR). Recipient NK cells can also trigger antibody-independent microvascular inflammation by sensing the absence of self HLA class I molecules ("missing self") on allograft endothelial cells. This translational study investigated whether the condition of missing self amplifies DSA-dependent NK cell activation to worsen chronic AMR.

Methods And Results: Among 1682 kidney transplant recipients who underwent an allograft biopsy at Lyon University Hospital between 2004 and 2017, 135 fulfilled the diagnostic criteria for AMR and were enrolled in the study. Patients with complement-fixing DSAs identified by a positive C3d binding assay (=73, 54%) had a higher risk of transplant failure (=0.002). Among the remaining patients with complement-independent chronic AMR (=62, 46%), those in whom missing self was identified through donor and recipient genotyping exhibited worse allograft survival (=0.02). In multivariable analysis, only proteinuria (HR: 7.24; =0.01) and the presence of missing self (HR: 3.57; =0.04) were independent predictors for transplant failure following diagnosis of chronic AMR. Cocultures of human NK cells and endothelial cells confirmed that addition of missing self to DSA-induced NK cell activation increased endothelial damage.

Conclusions: The assessment of missing self at the time of diagnosis of chronic AMR identifies patients at higher risk for kidney transplant failure.
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http://dx.doi.org/10.1681/ASN.2020040433DOI Listing
February 2021

Incidence, Characteristics, and Outcome of COVID-19 in Adults on Kidney Replacement Therapy: A Regionwide Registry Study.

J Am Soc Nephrol 2021 02 5;32(2):385-396. Epub 2020 Nov 5.

Division of Nephrology and Infectious Diseases, AZ Sint-Jan Brugge, Brugge, Belgium

Background: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection disproportionally affects frail, elderly patients and those with multiple chronic comorbidities. Whether patients on RRT have an additional risk because of their specific exposure and complex immune dysregulation is controversial.

Methods: To describe the incidence, characteristics, and outcomes of SARS-CoV-2 infection, we conducted a prospective, multicenter, region-wide registry study in adult patients on RRT versus the general population from March 2 to May 25, 2020. This study comprised all patients undergoing RRT in the Flanders region of Belgium, a country that has been severely affected by coronavirus disease 2019 (COVID-19).

Results: At the end of the epidemic wave, crude and age-standardized cumulative incidence rates of SARS-CoV-2 infection were 5.3% versus 2.5%, respectively, among 4297 patients on hemodialysis, and 1.4% versus 1.6%, respectively, among 3293 patients with kidney transplants (compared with 0.6% in the general population). Crude and age-standardized cumulative mortality rates were 29.6% versus 19.9%, respectively, among patients on hemodialysis, and 14.0% versus 23.0%, respectively, among patients with transplants (compared with 15.3% in the general population). We found no excess mortality in the hemodialysis population when compared with mean mortality rates during the same 12-week period in 2015-2019 because COVID-19 mortality was balanced by lower than expected mortality among uninfected patients. Only 0.18% of the kidney transplant population died of SARS-CoV-2 infection.

Conclusions: Mortality associated with SARS-CoV-2 infection is high in patients on RRT. Nevertheless, the epidemic's overall effect on the RRT population remained remarkably limited in Flanders. Calculation of excess mortality and age standardization provide a more reliable picture of the mortality burden of COVID-19 among patients on RRT.
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http://dx.doi.org/10.1681/ASN.2020060875DOI Listing
February 2021

Differential role of nicotinamide adenine dinucleotide deficiency in acute and chronic kidney disease.

Nephrol Dial Transplant 2021 Jan;36(1):60-68

Department of Cell Physiology and Metabolism, University of Geneva, Geneva, Switzerland.

Background: Nicotinamide adenine dinucleotide (NAD+) is a ubiquitous coenzyme involved in electron transport and a co-substrate for sirtuin function. NAD+ deficiency has been demonstrated in the context of acute kidney injury (AKI).

Methods: We studied the expression of key NAD+ biosynthesis enzymes in kidney biopsies from human allograft patients and patients with chronic kidney disease (CKD) at different stages. We used ischaemia-reperfusion injury (IRI) and cisplatin injection to model AKI, urinary tract obstruction [unilateral ureteral obstruction (UUO)] and tubulointerstitial fibrosis induced by proteinuria to investigate CKD in mice. We assessed the effect of nicotinamide riboside (NR) supplementation on AKI and CKD in animal models.

Results: RNA sequencing analysis of human kidney allograft biopsies during the reperfusion phase showed that the NAD+de novo synthesis is impaired in the immediate post-transplantation period, whereas the salvage pathway is stimulated. This decrease in de novo NAD+ synthesis was confirmed in two mouse models of IRI where NR supplementation prevented plasma urea and creatinine elevation and tubular injury. In human biopsies from CKD patients, the NAD+de novo synthesis pathway was impaired according to CKD stage, with better preservation of the salvage pathway. Similar alterations in gene expression were observed in mice with UUO or chronic proteinuric glomerular disease. NR supplementation did not prevent CKD progression, in contrast to its efficacy in AKI.

Conclusion: Impairment of NAD+ synthesis is a hallmark of AKI and CKD. NR supplementation is beneficial in ischaemic AKI but not in CKD models.
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http://dx.doi.org/10.1093/ndt/gfaa124DOI Listing
January 2021

Replicative senescence and arteriosclerosis after kidney transplantation.

Nephrol Dial Transplant 2020 11;35(11):1984-1995

Department of Microbiology and Immunology, KU Leuven - University of Leuven, Leuven, Belgium.

Background: Replicative senescence is associated with telomere shortening. In native kidneys, obtained prior to transplantation, we recently described and validated a significant association between shorter intrarenal telomere length and renal arteriosclerosis. After renal transplantation, animal experiments suggested that ischaemia-reperfusion injury, acute rejection episodes and cytomegalovirus disease associate with accelerated renal allograft senescence. The association between post-transplant events and replicative senescence has not yet been evaluated in a human setting.

Methods: In a cohort of 134 kidney allograft recipients, we performed protocol-specified renal allograft biopsies at 3 months, 1 year, 2 years and 5 years after transplantation (n = 579 biopsies). We used quantitative real-time polymerase chain reaction to measure intrarenal relative average telomere length (T/S ratio). The association between donor and recipient demographic factors, post-transplant clinical/histological events, renal allograft histological evolution by 5 years post-transplant and intrarenal telomere length at 5 years after transplantation was studied using multiple regression models.

Results: At 5 years after transplantation, shorter intrarenal telomere length was associated with male donor gender, older donor age, donor history of hypertension and donor cardiovascular risk, which confirms the associations observed in native kidneys. Recipient characteristics and post-transplant events like delayed graft function, acute rejection episodes, presence of donor-specific antibodies, cytomegalovirus disease and immunosuppressive regimen did not associate with alterations of intrarenal telomere length at 5 years. Independent of donor age and donor cardiovascular risk, intrarenal arteriosclerosis in protocol biopsies obtained at 5 years after transplantation and progressive arteriosclerosis over time after transplantation associated with shorter telomere length, while this was not the case for other histological lesions. Moreover, telomere attrition augments the association between older donor age and the presence of severe arteriosclerosis. In the group with the oldest donor age and shortest telomere length, there was significantly more severe arteriosclerosis (43%) in protocol biopsies at 5 years after transplantation, compared with other combinations (13-28%) (P = 0.001). Intrarenal arteriosclerosis at 5 years after transplantation did not associate with post-transplant clinical events.

Conclusions: We demonstrate that intrarenal telomere length at 5 years after transplantation, as a marker for replicative senescence, associates with renal arteriosclerosis and reflects kidney donor characteristics, but not post-transplant events.
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http://dx.doi.org/10.1093/ndt/gfaa151DOI Listing
November 2020

Urinary Protein Biomarker Panel for the Diagnosis of Antibody-Mediated Rejection in Kidney Transplant Recipients.

Kidney Int Rep 2020 Sep 29;5(9):1448-1458. Epub 2020 Jun 29.

Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.

Introduction: Antibody-mediated rejection (ABMR) impacts kidney allograft outcome. The diagnosis is made based on findings from invasive kidney transplant biopsy specimens. The aim of this study was to identify a noninvasive urinary protein biomarker for ABMR after kidney transplantation.

Methods: We performed a multicenter case-control study to identify a urinary biomarker for ABMR (training cohort,  = 249) and an independent, prospective multicenter cohort study for validation ( = 391). We used concomitant biopsies to classify the samples according to the Banff classification. After untargeted protein identification and quantification, we used a support vector machine to train the model in the training cohort. The primary endpoint was the diagnostic accuracy of the urinary biomarker for ABMR in the validation cohort.

Results: We identified a set of 10 urinary proteins that accurately discriminated patients with ( = 60) and without ( = 189) ABMR in the training cohort with an area under the curve (AUC) of 0.98 (95% confidence interval [CI], 0.96-1.00). The diagnostic accuracy was maintained in the validation cohort (AUC, 0.88; 95% CI, 0.8-0.93) for discriminating the presence ( = 43) from the absence ( = 348) of ABMR. The negative predictive value of the 10-protein marker set for exclusion of ABMR was 0.99, and the positive predictive value was 0.33. The diagnostic accuracy was independent of the reason for performing the biopsy, time after transplantation, and better than the accuracy of gross proteinuria (AUC, 0.76).

Conclusions: We identified and validated a urinary protein biomarker set that can be used to exclude ABMR.
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http://dx.doi.org/10.1016/j.ekir.2020.06.018DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7486186PMC
September 2020

The effect of IGL-1 preservation solution on outcome after kidney transplantation: A retrospective single-center analysis.

Am J Transplant 2021 02 12;21(2):830-837. Epub 2020 Oct 12.

Laboratory of Abdominal Transplantation, Transplantation Research Group, Department of Microbiology, Immunology, and Transplantation, KU Leuven, Leuven, Belgium.

Institut Georges Lopez-1 (IGL-1) solution is increasingly used for kidney preservation, although little information on outcomes is available. Outcomes of all deceased donor kidneys preserved by IGL-1, University of Wisconsin solution (UW), or histidine-tryptophan-ketoglutarate (HTK) and transplanted in our center (2000-2018) were analyzed. Multivariable analysis for delayed graft function (DGF), functional DGF, estimated glomerular filtration rate (eGFR, CKD-EPI equation), proteinuria, acute rejection, death-censored graft loss, and patient survival were performed. A double robust approach, consisting of propensity score weighting and correction for confounders, minimized the risk of bias. In total, 1943 transplants were included: 234 with IGL-1, 1046 with UW, and 663 with HTK. As IGL-1 was only introduced in 2014, a prespecified sensitivity analysis of 917 kidneys (2010-2018) was performed using the same statistical approach. After weighting, IGL-1 retained a higher proportion of kidneys donated after circulatory death (DCD). IGL-1 was not independently associated with any of the outcomes when compared to UW or HTK. Sensitivity analysis between 2010 and 2018 showed similar results. In this retrospective analysis, using robust methodology to reduce the risk of bias, IGL-1 preservation results in equal outcomes compared to UW or HTK, despite more DCD transplants in the IGL-1 group.
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http://dx.doi.org/10.1111/ajt.16302DOI Listing
February 2021

Author Correction: Altered proximal tubular cell glucose metabolism during acute kidney injury is associated with mortality.

Nat Metab 2020 09;2(9):989

Laboratory of Nephrology, Department of Medicine and Cell Physiology, University Hospital and University of Geneva, Geneva, Switzerland.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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http://dx.doi.org/10.1038/s42255-020-00283-6DOI Listing
September 2020

Trajectories of glomerular filtration rate and progression to end stage kidney disease after kidney transplantation.

Kidney Int 2021 01 8;99(1):186-197. Epub 2020 Aug 8.

Université de Paris, INSERM, PARCC, Paris Translational Research Centre for Organ Transplantation, Paris, France; Kidney Transplant Department, Necker Hospital, Assistance Publique - Hôpitaux de Paris, Paris, France. Electronic address:

Although the gold standard of monitoring kidney transplant function relies on glomerular filtration rate (GFR), little is known about GFR trajectories after transplantation, their determinants, and their association with outcomes. To evaluate these parameters we examined kidney transplant recipients receiving care at 15 academic centers. Patients underwent prospective monitoring of estimated GFR (eGFR) measurements, with assessment of clinical, functional, histological and immunological parameters. Additional validation took place in seven randomized controlled trials that included a total of 14,132 patients with 403,497 eGFR measurements. After a median follow-up of 6.5 years, 1,688 patients developed end-stage kidney disease. Using unsupervised latent class mixed models, we identified eight distinct eGFR trajectories. Multinomial regression models identified seven significant determinants of eGFR trajectories including donor age, eGFR, proteinuria, and several significant histological features: graft scarring, graft interstitial inflammation and tubulitis, microcirculation inflammation, and circulating anti-HLA donor specific antibodies. The eGFR trajectories were associated with progression to end stage kidney disease. These trajectories, their determinants and respective associations with end stage kidney disease were similar across cohorts, as well as in diverse clinical scenarios, therapeutic eras and in the seven randomized control trials. Thus, our results provide the basis for a trajectory-based assessment of kidney transplant patients for risk stratification and monitoring.
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http://dx.doi.org/10.1016/j.kint.2020.07.025DOI Listing
January 2021

The Histological Picture of Indication Biopsies in the First 2 Weeks after Kidney Transplantation.

Clin J Am Soc Nephrol 2020 Oct 10;15(10):1484-1493. Epub 2020 Aug 10.

Department of Microbiology, Immunology and Transplantation, Katholieke Universiteit Leuven, Leuven, Belgium

Background And Objectives: In preclinical studies, ischemia-reperfusion injury and older donor age are associated with graft inflammation in the early phase after transplantation. In human kidney transplantation, impaired allograft function in the first days after transplantation is often adjudicated to donor- and procedure-related characteristics, such as donor age, donor type, and ischemia times.

Design: In a cohort of 984 kidney recipients, 329 indication biopsies were performed within the first 14 days after transplantation. The histologic picture of these biopsies and its relationship with alloimmune risk factors and donor- and procedure-related characteristics were studied, as well as the association with graft failure. Multivariable Cox models were applied to quantify the cause-specific hazard ratios for early rejection and early inflammatory scores, adjusted for potential confounders. For quantification of hazard ratios of early events for death-censored graft failure, landmark analyses starting from day 15 were used.

Results: Early indication biopsy specimens displayed microvascular inflammation score ≥2 in 30% and tubulointerstitial inflammation score ≥2 in 49%. Rejection was diagnosed in 186 of 329 (57%) biopsies and associated with the presence of pretransplant donor-specific HLA antibodies and the number of HLA mismatches, but not nonimmune risk factors in multivariable Cox proportional hazards analysis. In multivariable Cox proportional hazards analysis, delayed graft function, the graft dysfunction that prompted an early indication biopsy, HLA mismatches, and pretransplant donor-specific HLA antibodies were significantly associated with a higher risk for death-censored graft failure, whereas early acute rejection was not.

Conclusions: Indication biopsies performed early after kidney transplantation display inflammatory changes related to alloimmune risk factors. Nonimmune risk factors for ischemia-reperfusion injury, such as cold and warm ischemia time, older donor age, and donor type, were not identified as strong risk factors for early inflammation after human kidney transplantation.
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http://dx.doi.org/10.2215/CJN.04230320DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7536761PMC
October 2020

Eplet Mismatch Load and Occurrence of Donor-Specific Anti-HLA Antibodies, Rejection, and Graft Failure after Kidney Transplantation: An Observational Cohort Study.

J Am Soc Nephrol 2020 09 6;31(9):2193-2204. Epub 2020 Aug 6.

Department of Microbiology, Immunology and Transplantation, Katholieke Universiteit (KU) Leuven, University of Leuven, Leuven, Belgium

Background: In kidney transplantation, evaluating mismatches of HLA eplets-small patches of surface-exposed amino acids of the HLA molecule-instead of antigen mismatches might offer a better approach to assessing donor-recipient HLA incompatibility and improve risk assessment and prediction of transplant outcomes.

Methods: To evaluate the effect of number of eplet mismatches (mismatch load) on formation of donor-specific HLA antibodies (DSAs) and transplant outcomes, we conducted a cohort study that included consecutive adult kidney recipients transplanted at a single center from March 2004 to February 2013. We performed retrospective high-resolution genotyping of HLA loci of 926 transplant pairs and used the HLAMatchmaker computer algorithm to count HLA eplet mismatches.

Results: DSAs occurred in 43 (4.6%) patients. Multivariable analysis showed a significant independent association between antibody-verified eplet mismatch load and DSA occurrence and graft failure, mainly explained by DQ antibody-verified eplet effects. The association with DQ antibody-verified eplet mismatches was linear, without a safe threshold at which DSA did not occur. Odds for T cell- or antibody-mediated rejection increased by 5% and 12%, respectively, per antibody-verified DQ eplet mismatch.

Conclusions: Eplet mismatches in HLA-DQ confer substantial risk for DSA formation, graft rejection, and graft failure after kidney transplantation. Mismatches in other loci seem to have less effect. The results suggest that antibody-verified HLA-DQ eplet mismatch load could be used to guide personalized post-transplant immunosuppression. Adoption of molecular matching for DQA and DQB alleles could also help to minimize DSA formation and potentially improve transplant outcomes.
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http://dx.doi.org/10.1681/ASN.2020010019DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461684PMC
September 2020

Altered proximal tubular cell glucose metabolism during acute kidney injury is associated with mortality.

Nat Metab 2020 08 20;2(8):732-743. Epub 2020 Jul 20.

Laboratory of Nephrology, Department of Medicine and Cell Physiology, University Hospital and University of Geneva, Geneva, Switzerland.

Acute kidney injury (AKI) is strongly associated with mortality, independently of its cause. The kidney contributes to up to 40% of systemic glucose production by gluconeogenesis during fasting and under stress conditions. Whether kidney gluconeogenesis is impaired during AKI and how this might influence systemic metabolism remain unknown. Here we show that glucose production and lactate clearance are impaired during human and experimental AKI by using renal arteriovenous catheterization in patients, lactate tolerance testing in mice and glucose isotope labelling in rats. Single-cell transcriptomics reveal that gluconeogenesis is impaired in proximal tubule cells during AKI. In a retrospective cohort of critically ill patients, we demonstrate that altered glucose metabolism during AKI is a major determinant of systemic glucose and lactate levels and is strongly associated with mortality. Thiamine supplementation increases lactate clearance without modifying renal function in mice with AKI, enhances glucose production by renal tubular cells ex vivo and is associated with reduced mortality and improvement of the metabolic pattern in a retrospective cohort of critically ill patients with AKI. This study highlights an unappreciated systemic role of renal glucose and lactate metabolism under stress conditions, delineates general mechanisms of AKI-associated mortality and introduces a potential intervention targeting metabolism for a highly prevalent clinical condition with limited therapeutic options.
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http://dx.doi.org/10.1038/s42255-020-0238-1DOI Listing
August 2020

Transcriptional Changes in Kidney Allografts with Histology of Antibody-Mediated Rejection without Anti-HLA Donor-Specific Antibodies.

J Am Soc Nephrol 2020 09 8;31(9):2168-2183. Epub 2020 Jul 8.

Department of Microbiology, Immunology and Transplantation, Nephrology and Renal Transplantation Research Group, Katholieke Universiteit (KU) Leuven, Leuven, Belgium

Background: Circulating donor-specific anti-HLA antibodies (HLA-DSAs) are often absent in serum of kidney allograft recipients whose biopsy specimens demonstrate histology of antibody-mediated rejection (ABMR). It is unclear whether cases involving ABMR histology without detectable HLA-DSAs represent a distinct clinical and molecular phenotype.

Methods: In this multicenter cohort study, we integrated allograft microarray analysis with extensive clinical and histologic phenotyping from 224 kidney transplant recipients between 2011 and 2017. We used the term ABMR histology for biopsy specimens that fulfill the first two Banff 2017 criteria for ABMR, irrespective of HLA-DSA status.

Results: Of 224 biopsy specimens, 56 had ABMR histology; 26 of these (46.4%) lacked detectable serum HLA-DSAs. Biopsy specimens with ABMR histology showed overexpression of transcripts mostly related to IFN-induced pathways and activation of natural killer cells and endothelial cells. HLA-DSA-positive and HLA-DSA-negative biopsy specimens with ABMR histology displayed similar upregulation of pathways and enrichment of infiltrating leukocytes. Transcriptional heterogeneity observed in biopsy specimens with ABMR histology was not associated with HLA-DSA status but was caused by concomitant T cell-mediated rejection. Compared with cases lacking ABMR histology, those with ABMR histology and HLA-DSA had higher allograft failure risk (hazard ratio [HR], 7.24; 95% confidence interval [95% CI], 3.04 to 17.20) than cases without HLA-DSA (HR, 2.33; 95% CI, 0.85 to 6.33), despite the absence of transcriptional differences.

Conclusions: ABMR histology corresponds to a robust intragraft transcriptional signature, irrespective of HLA-DSA status. Outcome after ABMR histology is not solely determined by the histomolecular presentation but is predicted by the underlying etiologic factor. It is important to consider this heterogeneity in further research and in treatment decisions for patients with ABMR histology.
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http://dx.doi.org/10.1681/ASN.2020030306DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7461663PMC
September 2020

Diagnostic performance of kSORT, a blood-based mRNA assay for noninvasive detection of rejection after kidney transplantation: A retrospective multicenter cohort study.

Am J Transplant 2021 02 4;21(2):740-750. Epub 2020 Aug 4.

French National Institute of Health and Medical Research (Inserm) Unit 1111, Lyon, France.

The Kidney Solid Organ Response Test (kSORT) blood gene expression assay was developed to noninvasively detect acute rejection (AR) after kidney transplantation. Its performance in a setting with natural disease prevalence has not been evaluated. A retrospective, multicenter cohort study was conducted across all single kidney transplant recipients, transplanted between 2011 and 2015, with samples within the first year after transplantation available in existing biobanks. The primary objective was to determine the diagnostic performance of the kSORT assay to detect AR (T cell-mediated and/or antibody-mediated rejection) as compared to a concomitant renal biopsy. AR was reported on the concomitant biopsy in 188 of 1763 (10.7%) blood samples and any rejection (including borderline changes) in 614 of 1763 (34.8%) blood samples. In 320 of 1763 samples (18.2%) the kSORT risk category was indeterminate. The kSORT assay had no diagnostic value for AR (area under the curve [AUC] 0.51, 95% confidence interval [CI] 0.50-0.56; P = .46) overall, or when considering indication biopsies (N = 487) and protocol-specified biopsies (N = 1276) separately (AUC of 0.53, 95% CI 0.50-0.59, P = .44 and 0.55, 95% CI 0.50-0.61, P = .09, respectively). This large retrospective study utilizing samples obtained under real-world clinical conditions, was unable to validate the kSORT assay for detection of AR in the first year after transplantation.
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http://dx.doi.org/10.1111/ajt.16179DOI Listing
February 2021

Antibody-mediated rejection with and without donor-specific anti-human leucocyte antigen antibodies: performance of the peripheral blood 8-gene expression assay.

Nephrol Dial Transplant 2020 08;35(8):1328-1337

KU Leuven Department of Microbiology, Immunology and Transplantation, Nephrology and Renal Transplantation Research Group, Leuven, Belgium.

Background: Recently a peripheral blood 8-gene expression assay was developed for non-invasive detection of antibody-mediated rejection (ABMR) after kidney transplantation. Its value has not yet been evaluated in detail in clinical scenarios with different baseline disease probability [human leucocyte antigen donor-specific antibodies (HLA-DSA)-positive versus HLA-DSA-negative cases at the time of stable graft function versus graft dysfunction].

Methods: Here we investigated the diagnostic accuracy of the 8-gene expression assay for histology of ABMR (ABMRh) with or without HLA-DSA in a cross-sectional cohort study of 387 blood samples with a concomitant graft biopsy.

Results: In patients with HLA-DSA (n = 64), the 8-gene expression assay discriminated DSA-positive ABMRh (DSAposABMRh) cases (n = 16) with good diagnostic performance {area under the receiver operating characteristic curve [AUROC] 83.1% [95% confidence interval (CI) 70.8-95.3]}. Also, in HLA-DSA-negative samples (n = 323), a clinically relevant diagnostic performance for DSAnegABMRh cases was found (n = 30) with an AUROC of 75.8% (95% CI 67.4-84.4). The 8-gene assay did not discriminate DSAposABMRh cases from DSAnegABMRh cases. There was a net benefit for clinical decision-making when adding the 8-gene expression assay to a clinical model consisting of estimated glomerular filtration rate, proteinuria, HLA-DSA and age.

Conclusion: The 8-gene expression assay shows great potential for implementation in the clinical follow-up of high-risk HLA-DSA-positive patients and clinical relevance in HLA-DSA-negative cases.
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http://dx.doi.org/10.1093/ndt/gfaa096DOI Listing
August 2020

The association between use of proton-pump inhibitors and excess mortality after kidney transplantation: A cohort study.

PLoS Med 2020 06 15;17(6):e1003140. Epub 2020 Jun 15.

Department of Nephrology and Renal Transplantation, University Hospitals Leuven and Nephrology & Renal Transplantation Research Group, Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.

Background: Chronic use of proton-pump inhibitors (PPIs) is common in kidney transplant recipients (KTRs). However, concerns are emerging about the potential long-term complications of PPI therapy. We aimed to investigate whether PPI use is associated with excess mortality risk in KTRs.

Methods And Findings: We investigated the association of PPI use with mortality risk using multivariable Cox proportional hazard regression analyses in a single-center prospective cohort of 703 stable outpatient KTRs, who visited the outpatient clinic of the University Medical Center Groningen (UMCG) between November 2008 and March 2011 (ClinicalTrials.gov Identifier NCT02811835). Independent replication of the results was performed in a prospective cohort of 656 KTRs from the University Hospitals Leuven (NCT01331668). Mean age was 53 ± 13 years, 57% were male, and 56.6% used PPIs. During median follow-up of 8.2 (4.7-9.0) years, 194 KTRs died. In univariable Cox regression analyses, PPI use was associated with an almost 2 times higher mortality risk (hazard ratio [HR] 1.86, 95% CI 1.38-2.52, P < 0.001) compared with no use. After adjustment for potential confounders, PPI use remained independently associated with mortality (HR 1.68, 95% CI 1.21-2.33, P = 0.002). Moreover, the HR for mortality risk in KTRs taking a high PPI dose (>20 mg omeprazole equivalents/day) compared with patients taking no PPIs (HR 2.14, 95% CI 1.48-3.09, P < 0.001) was higher than in KTRs taking a low PPI dose (HR 1.72, 95% CI 1.23-2.39, P = 0.001). These findings were replicated in the Leuven Renal Transplant Cohort. The main limitation of this study is its observational design, which precludes conclusions about causation.

Conclusions: We demonstrated that PPI use is associated with an increased mortality risk in KTRs, independent of potential confounders. Moreover, our data suggest that this risk is highest among KTRs taking high PPI dosages. Because of the observational nature of our data, our results require further corroboration before it can be recommended to avoid the long-term use of PPIs in KTRs.

Trial Registration: ClinicalTrials.gov Identifier: NCT02811835, NCT01331668.
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http://dx.doi.org/10.1371/journal.pmed.1003140DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7295199PMC
June 2020

The Banff 2019 Kidney Meeting Report (I): Updates on and clarification of criteria for T cell- and antibody-mediated rejection.

Am J Transplant 2020 09 28;20(9):2318-2331. Epub 2020 May 28.

Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Canada.

The XV. Banff conference for allograft pathology was held in conjunction with the annual meeting of the American Society for Histocompatibility and Immunogenetics in Pittsburgh, PA (USA) and focused on refining recent updates to the classification, advances from the Banff working groups, and standardization of molecular diagnostics. This report on kidney transplant pathology details clarifications and refinements to the criteria for chronic active (CA) T cell-mediated rejection (TCMR), borderline, and antibody-mediated rejection (ABMR). The main focus of kidney sessions was on how to address biopsies meeting criteria for CA TCMR plus borderline or acute TCMR. Recent studies on the clinical impact of borderline infiltrates were also presented to clarify whether the threshold for interstitial inflammation in diagnosis of borderline should be i0 or i1. Sessions on ABMR focused on biopsies showing microvascular inflammation in the absence of C4d staining or detectable donor-specific antibodies; the potential value of molecular diagnostics in such cases and recommendations for use of the latter in the setting of solid organ transplantation are presented in the accompanying meeting report. Finally, several speakers discussed the capabilities of artificial intelligence and the potential for use of machine learning algorithms in diagnosis and personalized therapeutics in solid organ transplantation.
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http://dx.doi.org/10.1111/ajt.15898DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496245PMC
September 2020

Banff 2019 Meeting Report: Molecular diagnostics in solid organ transplantation-Consensus for the Banff Human Organ Transplant (B-HOT) gene panel and open source multicenter validation.

Am J Transplant 2020 09 27;20(9):2305-2317. Epub 2020 Jun 27.

Department of Pathology, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.

This meeting report from the XV Banff conference describes the creation of a multiorgan transplant gene panel by the Banff Molecular Diagnostics Working Group (MDWG). This Banff Human Organ Transplant (B-HOT) panel is the culmination of previous work by the MDWG to identify a broadly useful gene panel based on whole transcriptome technology. A data-driven process distilled a gene list from peer-reviewed comprehensive microarray studies that discovered and validated their use in kidney, liver, heart, and lung transplant biopsies. These were supplemented by genes that define relevant cellular pathways and cell types plus 12 reference genes used for normalization. The 770 gene B-HOT panel includes the most pertinent genes related to rejection, tolerance, viral infections, and innate and adaptive immune responses. This commercially available panel uses the NanoString platform, which can quantitate transcripts from formalin-fixed paraffin-embedded samples. The B-HOT panel will facilitate multicenter collaborative clinical research using archival samples and permit the development of an open source large database of standardized analyses, thereby expediting clinical validation studies. The MDWG believes that a pathogenesis and pathway based molecular approach will be valuable for investigators and promote therapeutic decision-making and clinical trials.
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http://dx.doi.org/10.1111/ajt.16059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7496585PMC
September 2020

Identification and Characterization of Trajectories of Cardiac Allograft Vasculopathy After Heart Transplantation: A Population-Based Study.

Circulation 2020 Jun 4;141(24):1954-1967. Epub 2020 May 4.

Department of Cardiology, Smidt Heart Institute, Cedars-Sinai Medical Center, Los Angeles, CA (R.L., J.K.P., J.K.).

Background: Cardiac allograft vasculopathy (CAV) is a major contributor of heart transplant recipient mortality. Little is known about the prototypes of CAV trajectories at the population level. We aimed to identify the different evolutionary profiles of CAV and to determine the respective contribution of immune and nonimmune factors in CAV development.

Methods: Heart transplant recipients were from 4 academic centers (Pitié-Salpêtrière and Georges Pompidou Hospital, Paris, Katholieke Universiteit Leuven, and Cedars-Sinai, Los Angeles; 2004-2016). Patients underwent prospective, protocol-based monitoring consisting of repeated coronary angiographies together with systematic assessments of clinical, histological, and immunologic parameters. The main outcome was a prediction for CAV trajectory. We identified CAV trajectories by using unsupervised latent class mixed models. We then identified the independent predictive variables of the CAV trajectories and their association with mortality.

Results: A total of 1301 patients were included (815 and 486 in the European and US cohorts, respectively). The median follow-up after transplantation was 6.6 (interquartile range, 4-9.1) years with 4710 coronary angiographies analyzed. We identified 4 distinct profiles of CAV trajectories over 10 years. The 4 trajectories were characterized by (1) patients without CAV at 1 year and nonprogression over time (56.3%), (2) patients without CAV at 1 year and late-onset slow CAV progression (7.6%), (3) patients with mild CAV at 1 year and mild progression over time (23.1%), and (4) patients with mild CAV at 1 year and accelerated progression (13.0%). This model showed good discrimination (0.92). Among candidate predictors assessed, 6 early independent predictors of these trajectories were identified: donor age (<0.001), donor male sex (<0.001), donor tobacco consumption (=0.001), recipient dyslipidemia (=0.009), class II anti-human leukocyte antigen donor-specific antibodies (=0.004), and acute cellular rejection ≥2R (=0.028). The 4 CAV trajectories manifested consistently in the US independent cohort with similar discrimination (0.97) and in different clinical scenarios, and showed gradients for overall-cause mortality (<0.001).

Conclusions: In a large multicenter and highly phenotyped prospective cohort of heart transplant recipients, we identified 4 CAV trajectories and their respective independent predictive variables. Our results provide the basis for a trajectory-based assessment of patients undergoing heart transplantation for early risk stratification, patient monitoring, and clinical trials. Registration: URL: https://www.clinicaltrials.gov; Unique identifier: NCT04117152.
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http://dx.doi.org/10.1161/CIRCULATIONAHA.119.044924DOI Listing
June 2020

Intrarenal arteriosclerosis and telomere attrition associate with dysregulation of the cholesterol pathway.

Aging (Albany NY) 2020 04 30;12(9):7830-7847. Epub 2020 Apr 30.

Department of Microbiology and Immunology, KU Leuven - University of Leuven, Leuven, Belgium.

Background: Recently, we demonstrated that arteriosclerosis in the smaller intrarenal arteries is associated with shorter telomere length, independently of history of cardiovascular events and calendar age. This suggests that intrarenal arteriosclerosis reflects replicative senescence, although the underlying molecular alterations remain unclear.

Results: Shorter intrarenal telomere length associated significantly with the presence of renal arteriosclerosis (T/S ratio 0.91±0.15 vs. 1.20±0.23 with vs. without arteriosclerosis, p=0.007, test cohort; T/S ratio 0.98 ±0.26 vs. 1.03 ±0.18 with vs. without arteriosclerosis, p=0.02, validation cohort). The presence versus absence of intrarenal arteriosclerosis was associated with differential expression of 1472 transcripts. Pathway analysis revealed enrichment of molecules involved in the superpathway of cholesterol biosynthesis as the most significant. The differential expression of these genes was confirmed in the independent validation cohort. Furthermore, the specific mRNA expression of the molecules in the superpathway of cholesterol biosynthesis associated significantly with intrarenal telomere length, and with history of cardiovascular events.

Interpretation: Our study illustrates that the superpathway of cholesterol biosynthesis interacts with the previously published association between shorter telomere length and arteriosclerosis.

Methods: This study included a test cohort of 40 consecutive kidney donors (calendar age 48.0 ± 15), with biopsies obtained prior to transplantation. Intrarenal leucocyte telomere length content was assessed using quantitative RT-PCR. Whole genome microarray mRNA expression analysis was performed using Affymetrix Gene 2.0 ST arrays. We investigated the associations between mRNA gene expression, telomere length as marker of replicative senescence, and intrarenal arteriosclerosis (Banff "cv" score = vascular fibrous intimal thickening = intimal hyperplasia) using adjusted multiple regression models. For biological interpretation and pathway overrepresentation analysis, we used Ingenuity Pathway Analysis. The significant pathways and genes were validated in an independent validation cohort of 173 kidney biopsies obtained prior to transplantation.
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http://dx.doi.org/10.18632/aging.103098DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7244056PMC
April 2020

Development and validation of an optimized integrative model using urinary chemokines for noninvasive diagnosis of acute allograft rejection.

Am J Transplant 2020 12 27;20(12):3462-3476. Epub 2020 Jun 27.

Department of Nephrology and Kidney Transplantation, Necker Hospital, Assistance Publique-Hôpitaux de Paris, Paris, France.

The urinary chemokines CXCL9 and CXCL10 are promising noninvasive diagnostic markers of acute rejection (AR) in kidney recipients, but their levels might be confounded by urinary tract infection (UTI) and BK virus (BKV) reactivation. Multiparametric model development and validation addressed these confounding factors in a training set of 391 samples, optimizing the diagnostic performance of urinary chemokines. CXCL9/creatinine increased in UTI and BKV viremia with or without nephropathy (BKVN) (no UTI/leukocyturia/UTI: -0.10/1.61/2.09, P = .0001 and no BKV/viremia/BKVN: -0.10/1.90/2.29, P < .001) as well as CXCL10/creatinine (1.17/2.09/1.98, P < .0001 and 1.13/2.21/2.51, P < .001, respectively). An optimized 8-parameter model (recipient age, sex, estimated glomerular filtration rate, donor specific antibodies, UTI, BKV blood viral load, CXCL9, and CXCL10) diagnosed AR with high accuracy (area under the curve [AUC]: 0.85, 95% confidence interval [CI]: 0.80-0.89) and remained highly accurate at the time of screening (AUC: 0.81, 95% CI: 0.48-1) or indication biopsies (AUC: 0.85, 95% CI: 0.81-0.90) and within the first year (AUC: 0.86, 95% CI: 0.80-0.91) or later (AUC: 0.90, 95% CI: 0.84-0.96), achieving AR diagnosis with an AUC of 0.85 and 0.92 (P < .0001) in 2 external validation cohorts. Decision curve analyses demonstrated the clinical utility of the model. Considering confounding factors rather than excluding them, we optimized a noninvasive multiparametric diagnostic model for AR of kidney allografts with unprecedented accuracy.
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http://dx.doi.org/10.1111/ajt.15959DOI Listing
December 2020

Clinical importance of extended second field high-resolution HLA genotyping for kidney transplantation.

Am J Transplant 2020 12 15;20(12):3367-3378. Epub 2020 May 15.

Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.

The need for extended second field high-resolution (2F-HR) HLA genotyping in kidney transplantation is debated. In a cohort of 1000 kidney transplants, we evaluated the impact of different HLA genotyping levels on the assignment of donor-specific anti-HLA antibodies (DSA) and investigated whether inference of 2F-HR genotypes from low-resolution (LR) genotypes could be used to correctly assign DSA. Based on LR genotypes, 224 pretransplant DSAs were present in 140 patients and absent in 860 patients (DSA group). With extended 2F-HR HLA genotyping, we confirmed 173 DSA (77.2%) in 108 (77.1%) patients (2F-HR LR DSA group) and excluded DSA in 32 patients (22.9%) (2F-HR LR DSA group). Kaplan-Meier curves showed that 10-year graft survival rates were similar between the DSA and 2F-HR LR DSA groups (82.4% vs 93.8%; P = .27) and confirmed that DSA determined using LR typing but not confirmed using 2F-HR typing were indeed misclassified. By inferring 2F-HR genotypes using HaploStats, DSA still could not be correctly assigned in 23.3% of cases. We conclude that extended 2F-HR typing of the donor-recipient pairs is relevant for the correct assessment of DSA. Although inference of 2F-HR genotypes may improve the assessment of DSA in some cases, significant misclassification occurs, and warrants caution in using inferred HLA results for clinical and research purposes.
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http://dx.doi.org/10.1111/ajt.15938DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7754319PMC
December 2020

In reply to McGuinty et al.

J Heart Lung Transplant 2020 08 2;39(8):848-850. Epub 2020 Apr 2.

Department of Cardiology, University Hospitals Leuven, Leuven, Belgium.

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http://dx.doi.org/10.1016/j.healun.2020.03.013DOI Listing
August 2020

The role of HLA-DP mismatches and donor specific HLA-DP antibodies in kidney transplantation: a case series.

Transpl Immunol 2020 Mar 16:101287. Epub 2020 Mar 16.

Department of Nephrology and Renal Transplantation, University Hospitals Leuven, Leuven, Belgium; Department of Microbiology, Immunology and Transplantation, KU Leuven, Leuven, Belgium.

Background: The impact of HLA-DP mismatches on renal allograft outcome is still poorly understood and is suggested to be less than that of the other HLA loci. The common association of HLA-DP donor-specific antibodies (DSA) with other DSA obviates the evaluation of the actual effect of HLA-DP DSA.

Methods: From a large multicenter data collection, we retrospectively evaluated the significance of HLA-DP DSA on transplant outcome and the immunogenicity of HLA-DP eplet mismatches with respect to the induction of HLA-DP DSA. Furthermore, we evaluated the association between the MFI of HLA-DP antibodies detected in Luminex assays and the outcome of flowcytometric/complement-dependent cytotoxicity (CDC) crossmatches.

Results: In patients with isolated pretransplant HLA-DP antibodies (N = 13), 6 experienced antibody-mediated rejection (AMR) and 3 patients lost their graft. In HLAMatchmaker analysis of HLA-DP mismatches (N = 72), HLA-DP DSA developed after cessation of immunosuppression in all cases with 84DEAV (N = 14), in 86% of cases with 85GPM (N = 6/7), in 50% of cases with 56E (N = 6/12) and in 40% of cases with 56A mismatch (N = 2/5). Correlation analysis between isolated HLA-DP DSA MFI and crossmatches (N = 90) showed negative crossmatch results with HLA-DP DSA MFI <2000 (N = 14). Below an MFI of 10,000 CDC crossmatches were also negative (N = 33). Above these MFI values both positive (N = 35) and negative (N = 16) crossmatch results were generated.

Conclusions: Isolated HLA-DP DSA are rare, yet constitute a significant risk for AMR. We identified high-risk eplet mismatches that can lead to HLA-DP DSA formation. We therefore recommend HLA-DP typing to perform HLA-DP DSA analysis before transplantation. HLA-DP DSA with high MFI were not always correlated with positive crossmatch results.
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http://dx.doi.org/10.1016/j.trim.2020.101287DOI Listing
March 2020

External Validation of the DynPG for Kidney Transplant Recipients.

Transplantation 2021 02;105(2):396-403

INSERM UMR 1246 - SPHERE, Nantes University, Tours University, Nantes, France.

Background: In kidney transplantation, dynamic prediction of patient and kidney graft survival (DynPG) may help to promote therapeutic alliance by delivering personalized evidence-based information about long-term graft survival for kidney transplant recipients. The objective of the current study is to externally validate the DynPG.

Methods: Based on 6 baseline variables, the DynPG can be updated with any new serum creatinine measure available during the follow-up. From an external validation sample of 1637 kidney recipients with a functioning graft at 1-year posttransplantation from 2 European transplantation centers, we assessed the prognostic performance of the DynPG.

Results: As one can expect from an external validation sample, differences in several recipient, donor, and transplantation characteristics compared with the learning sample were observed. Patients were mainly transplanted from deceased donors (91.6% versus 84.8%; P < 0.01), were less immunized against HLA class I (18.4% versus 32.7%; P < 0.01) and presented less comorbidities (62.2% for hypertension versus 82.7%, P < 0.01; 25.1% for cardiovascular disease versus 33.9%, P < 0.01). Despite these noteworthy differences, the area under the ROC curve varied from 0.70 (95% confidence interval [CI], 0.64-0.76) to 0.76 (95% CI, 0.64-0.88) for prediction times at 1 and 6 years posttransplantation respectively, and calibration plots revealed reasonably accurate predictions.

Conclusions: We validated the prognostic capacities of the DynPG in terms of both discrimination and calibration. Our study showed the robustness of the DynPG for informing both the patient and the physician, and its transportability for a cohort presenting different features than the one used for the DynPG development.
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http://dx.doi.org/10.1097/TP.0000000000003209DOI Listing
February 2021