An observational cohort study of histological screening for BK polyomavirus nephropathy following viral replication in plasma

Systematic screening for BKPyV-DNAemia has been advocated to aid prevention and treatment of polyomavirus associated nephropathy (PyVAN), an important cause of kidney graft failure. The added value of performing a biopsy at time of BKPyV-DNAemia, to distinguish presumptive PyVAN (negative SV40 immunohistochemistry) and proven PyVAN (positive SV40) has not been established. Therefore, we studied an unselected cohort of 950 transplantations, performed between 2008-2017. BKPyV-DNAemia was detected in 250 (26.3%) transplant recipients, and positive SV40 in 91 cases (9.6%). Among 209 patients with a concurrent biopsy at time of first BKPyV-DNAemia, 60 (28.7%) biopsies were SV40 positive. Plasma viral load showed high diagnostic value for concurrent SV40 positivity (ROC-AUC 0.950, 95% confidence interval 0.916-0.978) and the semiquantitatively scored percentage of tubules with evidence of polyomavirus replication (pvl score) (0.979, 0.968-0.988). SV40 positivity was highly unlikely when plasma viral load is below 4 log10 copies/ml (negative predictive value 0.989, 0.979-0.994). In SV40 positive patients, higher plasma BKPyV-DNA load and higher pvl scores were associated with slower viral clearance from the blood (hazard ratio 0.712, 95% confidence interval 0.604-0.839, and 0.327, 0.161-0.668, respectively), whereas the dichotomy positivity/negativity of SV40 immunohistochemistry did not predict viral clearance. Although the pvl score offers some prognostic value for viral clearance on top of plasma viral load, the latter provided good guidance for when a biopsy was unnecessary to exclude PyVAN. Thus, the distinction between presumptive and proven PyVAN, based on SV40 immunohistochemistry, has limited clinical value. Hence, management of BKPyV-DNAemia and immunosuppression reduction should be weighed against the risk of occurrence of rejection, or exacerbation of rejection observed concomitantly.

Association of Predicted HLA T-Cell Epitope Targets and T-Cell-Mediated Rejection After Kidney Transplantation

RATIONALE & OBJECTIVE

The relationship between human leukocyte antigen (HLA) molecular mismatches and T-cell-mediated rejection (TCMR) is unknown. We investigated the associations between the different donor HLA-derived T-cell targets and the occurrence of TCMR and borderline histologic changes suggestive of TCMR after kidney transplantation.

STUDY DESIGN

Retrospective cohort study.

SETTING & PARTICIPANTS

All kidney transplant recipients at a single center between 2004 and 2013 with available biopsy data and a DNA sample for high-resolution HLA donor/recipient typing (N = 893).

EXPOSURE

Scores calculated by the HLA matching algorithm PIRCHE-II and HLA eplet mismatches.

OUTCOME

TCMR, borderline changes suggestive of TCMR, and allograft failure.

ANALYTICAL APPROACH

Multivariable cause-specific hazards models were fit to characterize the association between HLA epitopes targets and study outcomes.

RESULTS

We found 277 patients developed TCMR, and 134 developed only borderline changes suggestive of TCMR on at least 1 biopsy. In multivariable analyses, only the PIRCHE-II scores for HLA-DRB1 and HLA-DQB1 were independently associated with the occurrence of TCMR and with allograft failure; this was not the case for HLA class I molecules. If restricted to rejection episodes within the first 3 months after transplantation, only the T-cell epitope targets originating from the donor's HLA-DRB1 and HLA-DQB1, but not class I molecules, were associated with the early acute TCMR. Also, the median PIRCHE-II score for HLA class II was statistically different between the patients with TCMR compared to the patients without TCMR (129 [IQR, 60-240] vs 201 [IQR, 96-298], respectively; P < 0.0001). These differences were not observed for class I PIRCHE-II scores.

LIMITATIONS

Observational clinical data and residual confounding.

CONCLUSIONS

In the absence of HLA-DSA, HLA class II but not class I mismatches are associated with early episodes of acute TCMR and allograft failure. This suggests that current immunosuppressive therapies are largely able to abort the most deleterious HLA class I-directed alloimmune processes; however, alloresponses against HLA-DRB1 and HLA-DQB1 molecular mismatches remain insufficiently suppressed.

PLAIN-LANGUAGE SUMMARY

Genetic differences in the human leukocyte antigen (HLA) complex between kidney transplant donors and recipients play a central role in T-cell-mediated rejection (TCMR), which can lead to failure of the transplanted kidney. Evaluating this genetic disparity (mismatch) in the HLA complex at the molecular (epitope) level could contribute to better prediction of the immune response to the donor organ posttransplantation. We investigated the associations of the different donor HLA-derived T-cell epitope targets and scores obtained from virtual crossmatch algorithms with the occurrence of TCMR, borderline TCMR, and graft failure after kidney transplantation after taking into account the influence of donor-specific anti-HLA antibodies. This study illustrates the greater importance of the molecular mismatches in class II molecules compared to class I HLA molecules.

Data-Driven Chronic Allograft Phenotypes: A Novel and Validated Complement for Histologic Assessment of Kidney Transplant Biopsies

BACKGROUND

No validated system currently exists to realistically characterize the chronic pathology of kidney transplants that represents the dynamic disease process and spectrum of disease severity. We sought to develop and validate a tool to describe chronicity and severity of renal allograft disease and integrate it with the evaluation of disease activity.

METHODS

The training cohort included 3549 kidney transplant biopsies from an observational cohort of 937 recipients. We reweighted the chronic histologic lesions according to their time-dependent association with graft failure, and performed consensus k-means clustering analysis. Total chronicity was calculated as the sum of the weighted chronic lesion scores, scaled to the unit interval.

RESULTS

We identified four chronic clusters associated with graft outcome, based on the proportion of ambiguous clustering. The two clusters with the worst survival outcome were determined by interstitial fibrosis and tubular atrophy (IFTA) and by transplant glomerulopathy. The chronic clusters partially overlapped with the existing Banff IFTA classification (adjusted Rand index, 0.35) and were distributed independently of the acute lesions. Total chronicity strongly associated with graft failure (hazard ratio [HR], 8.33; 95% confidence interval [CI], 5.94 to 10.88; P<0.001), independent of the total activity scores (HR, 5.01; 95% CI, 2.83 to 7.00; P<0.001). These results were validated on an external cohort of 4031 biopsies from 2054 kidney transplant recipients.

CONCLUSIONS

The evaluation of total chronicity provides information on kidney transplant pathology that complements the estimation of disease activity from acute lesion scores. Use of the data-driven algorithm used in this study, called RejectClass, may provide a holistic and quantitative assessment of kidney transplant injury phenotypes and severity.

Clinicopathological characteristics and disease chronicity in native kidney biopsies in Flanders

Background

The Flemish Collaborative Glomerulonephritis Group (FCGG) registry provides complete population data on kidney disease epidemiology in the region of Flanders (Belgium), as it captures all native kidney biopsies performed in its population of 6.5 million inhabitants.

Methods

From 2017 until 2019, 2054 adult kidney biopsies were included from 26 nephrology centers (one biopsy per patient). Data on nephrotic and nephritic syndrome were available in 1992 and 2026 biopsies, respectively. In a subgroup of 898 biopsies containing ≥10 glomeruli from 2018 to 2019, disease chronicity was graded using the Mayo Clinic Chronicity Score (MCCS). The association between clinical variables and MCCS was determined using simple and multiple linear regression models.

Results

Nephrotic syndrome (present in 378 patients, 19.0%) was most frequently caused by minimal change disease in younger patients (18-44 years), membranous nephropathy in older patients (45-74 years) and amyloidosis in the elderly (>75 years). Nephritic syndrome (present in 421 patients, 20.8%) was most frequently caused by immunoglobulin A nephropathy (IgAN) in younger patients (18-64 years) and ANCA-associated vasculitis (AAV) in older patients (>64 years). AAV and IgAN were the most frequent underlying diagnoses in biopsies in which crescents were identified. In multivariable analysis, acute and chronic kidney disease and diagnoses of diabetic kidney disease, nephrosclerosis and hyperoxaluria/hypercalcemic nephropathy were associated with the highest MCCS increases.

Conclusions

The FCGG registry validates data from previous Western European registries and provides a snapshot of disease chronicity in the whole biopsied Flemish population.

Association of HLA Mismatches and Histology Suggestive of Antibody-Mediated Injury in the Absence of Donor-Specific Anti-HLA Antibodies

BACKGROUND AND OBJECTIVES

The histology of antibody-mediated rejection after kidney transplantation is observed frequently in the absence of detectable donor-specific anti-HLA antibodies. Although there is an active interest in the role of non-HLA antibodies in this phenotype, it remains unknown whether HLA mismatches play an antibody-independent role in this phenotype of microcirculation inflammation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

To study this, we used the tools HLAMatchmaker, three-dimensional electrostatic mismatch score, HLA solvent accessible amino acid mismatches, and mismatched donor HLA-derived T cell epitope targets to determine the degree of HLA molecular mismatches in 893 kidney transplant recipients with available biopsy follow-up. Multivariable Cox proportional hazards models were applied to quantify the cause-specific hazard ratios of the different types of HLA mismatch scores for developing antibody-mediated rejection or histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies. In all survival analyses, the patients were censored at the time of the last biopsy.

RESULTS

In total, 121 (14%) patients developed histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies, of which 44 (36%) patients had concomitant T cell-mediated rejection. In multivariable Cox analysis, all different calculations of the degree of HLA mismatch associated with developing histology of antibody-mediated rejection in the absence of donor-specific anti-HLA antibodies. This association was dependent neither on the presence of missing self (potentially related to natural killer cell activation) nor on the formation of de novo HLA antibodies. Also, glomerulitis and complement C4d deposition in peritubular capillaries associated with the degree of HLA mismatch in the absence of anti-HLA antibodies.

CONCLUSIONS

The histology of antibody-mediated rejection and its defining lesions are also observed in patients without circulating anti-HLA antibodies and relate to the degree of HLA mismatch.

The Pre-Transplant Non-HLA Antibody Burden Associates With the Development of Histology of Antibody-Mediated Rejection After Kidney Transplantation

Background

Many kidney allografts fail due to the occurrence of antibody-mediated rejection (ABMR), related to donor-specific anti-HLA antibodies (HLA-DSA). However, the histology of ABMR can also be observed in patients without HLA-DSA. While some non-HLA antibodies have been related to the histology of ABMR, it is not well known to what extent they contribute to kidney allograft injury. Here we aimed to investigate the role of 82 different non-HLA antibodies in the occurrence of histology of ABMR after kidney transplantation.

Methods

We included all patients who underwent kidney transplantation between 2004-2013 in a single center and had biobanked serum. Pre- and post-transplant sera (n=2870) were retrospectively tested for the presence of 82 different non-HLA antibodies using a prototype bead assay on Luminex (Immucor, Inc). A ratio was calculated between the measured MFI value and the cut-off MFI defined by the vendor for each non-HLA target.

Results

874 patients had available pretransplant sera and were included in this analysis. Of them, 133 (15.2%) received a repeat kidney allograft, and 100 (11.4%) had pretransplant HLA-DSA. In total, 204 (23.3%) patients developed histology of ABMR after kidney transplantation. In 79 patients (38.7%) the histology of ABMR was explained by pretransplant or de novo HLA-DSA. The multivariable Cox analysis revealed that only the broadly non-HLA sensitized (number of positive non-HLA antibodies) patients and those with the highest total strength of the non-HLA antibodies (total ratios of the positive non-HLA antibodies) were independently associated with increased rates of histology of ABMR after transplantation. Additionally, independent associations were found for antibodies against TUBB (HR=2.40; 95% CI 1.37 – 4.21, p=0.002), Collagen III (HR=1.67; 95% CI 1.08 – 2.58, p=0.02), VCL (HR=2.04; 95% CI 1.12 – 3.71, p=0.02) and STAT6 (HR=1.47; 95% CI 1.01 – 2.15, p=0.04). The overall posttransplant non-HLA autoreactivity was not associated with increased rates of ABMRh.

Conclusions

This study shows that patients highly and broadly sensitized against non-HLA targets are associated with an increased risk of ABMR histology after kidney transplantations in the absence of HLA-DSA. Also, some pretransplant non‐HLA autoantibodies are individually associated with increased rates of ABMR histology. However, whether these associations are clinically relevant and represent causality, warrants further studies.

Epidemiology of native kidney disease in Flanders: results from the FCGG kidney biopsy registry

Background

The Flemish Collaborative Glomerulonephritis Group (FCGG) registry is the first population-based native kidney biopsy registry in Flanders, Belgium. In this first analysis, we report on patient demographics, frequency distribution and incidence rate of biopsied kidney disease in adults in Flanders.

Methods

From January 2017 to December 2019, a total of 2054 adult first native kidney biopsies were included. A ‘double diagnostic coding’ strategy was used, in which every biopsy sample received a histopathological and final clinical diagnosis. Frequency distribution and incidence rate of both diagnoses were reported and compared with other European registries.

Results

The median age at biopsy was 61.1 years (interquartile range, 46.1–71.7); male patients were more prevalent (62.1%) and biopsy incidence rate was 129.3 per million persons per year. Immunoglobulin A nephropathy was the most frequently diagnosed kidney disease (355 biopsies, 17.3% of total) with a similar frequency as in previously published European registries. The frequency of tubulointerstitial nephritis (220 biopsies, 10.7%) and diabetic kidney disease (154 biopsies, 7.5%) was remarkably higher, which may be attributed to changes in disease incidence as well as biopsy practices. Discordances between histopathological and final clinical diagnoses were noted and indicate areas for improvement in diagnostic coding systems.

Conclusions

The FCGG registry, with its ‘double diagnostic coding’ strategy, provides useful population-based epidemiological data on a large Western European population and allows subgroup selection for future research.

Missing Self-Induced Microvascular Rejection of Kidney Allografts: A Population-Based Study

BACKGROUND

Circulating anti-HLA donor-specific antibodies (HLA-DSA) are often absent in kidney transplant recipients with microvascular inflammation (MVI). Missing self, the inability of donor endothelial cells to provide HLA I-mediated signals to inhibitory killer cell Ig-like receptors (KIRs) on recipient natural killer cells, can cause endothelial damage in vitro, and has been associated with HLA-DSA-negative MVI. However, missing self's clinical importance as a nonhumoral trigger of allograft rejection remains unclear.

METHODS

In a population-based study of 924 consecutive kidney transplantations between March 2004 and February 2013, we performed high-resolution donor and recipient HLA typing and recipient KIR genotyping. Missing self was defined as the absence of A3/A11, Bw4, C1, or C2 donor genotype, with the presence of the corresponding educated recipient inhibitory KIR gene.

RESULTS

We identified missing self in 399 of 924 transplantations. Co-occurrence of missing self types had an additive effect in increasing MVI risk, with a threshold at two concurrent types (hazard ratio [HR], 1.78; 95% confidence interval [95% CI], 1.26 to 2.53), independent of HLA-DSA (HR, 5.65; 95% CI, 4.01 to 7.96). Missing self and lesions of cellular rejection were not associated. No HLA-DSAs were detectable in 146 of 222 recipients with MVI; 28 of the 146 had at least two missing self types. Missing self associated with transplant glomerulopathy after MVI (HR, 2.51; 95% CI, 1.12 to 5.62), although allograft survival was better than with HLA-DSA-associated MVI.

CONCLUSION

Missing self specifically and cumulatively increases MVI risk after kidney transplantation, independent of HLA-DSA. Systematic evaluation of missing self improves understanding of HLA-DSA-negative MVI and might be relevant for improved diagnostic classification and patient risk stratification.

The evolution of histological changes suggestive of antibody-mediated injury, in the presence and absence of donor-specific anti-HLA antibodies

The interplay between donor-specific anti-HLA antibodies (HLA-DSA), histology of active antibody-mediated rejection (aABMR_h ), transplant glomerulopathy (cg) and graft failure in kidney transplantation remains insufficiently understood. We performed a single-center cohort study (n=1000) including 2761 protocol and 833 indication biopsies. Patients with pre-transplant HLA-DSA were more prone to develop aABMRh (OR 22.7, 95% CI, 11.8 - 43.7, p<0.001), cg (OR 5.76, 95% CI, 1.67 - 19.8, p=0.006) and aABMRh/cg (OR 19.5, 95% CI, 10.6 - 35.9, p<0.001). The negative impact of pre-transplant HLA-DSA on graft survival (HR 2.12, 95% CI, 1.41 - 3.20, p<0.001) was partially mediated through aABMRh and cg occurrence. When adjusted for time-dependent HLA-DSA (HR 4.03, 95% CI, 2.21 - 7.15, p=0.002), graft failure was only affected by aABMR_h when cg was evident. In HLA-DSA negative patients, aABMR_h was associated with impaired graft outcome only when evolving to cg (HR 1.32, 95% CI, 1.07 - 1.61, p=0.008). We conclude that the kinetics of HLA-DSA are important to estimate the rate of graft failure, and that histological follow-up is necessary to discover, often subclinical, ABMR and cg. In the absence of HLA-DSA, patients experience similar histological lesions and the evolution to transplant glomerulopathy associates with impaired graft outcome.

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

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-center 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 of 292 sABMR biopsies were reclassified to No ABMR, and 44 of 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 the 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.

Data-driven Derivation and Validation of Novel Phenotypes for Acute Kidney Transplant Rejection using Semi-supervised Clustering

BACKGROUND

Over the past decades, an international group of experts iteratively developed a consensus classification of kidney transplant rejection phenotypes, known as the Banff classification. Data-driven clustering of kidney transplant histologic data could simplify the complex and discretionary rules of the Banff classification, while improving the association with graft failure.

METHODS

The data consisted of a training set of 3510 kidney-transplant biopsies from an observational cohort of 936 recipients. Independent validation of the results was performed on an external set of 3835 biopsies from 1989 patients. On the basis of acute histologic lesion scores and the presence of donor-specific HLA antibodies, stable clustering was achieved on the basis of a consensus of 400 different clustering partitions. Additional information on kidney-transplant failure was introduced with a weighted Euclidean distance.

RESULTS

Based on the proportion of ambiguous clustering, six clinically meaningful cluster phenotypes were identified. There was significant overlap with the existing Banff classification (adjusted rand index, 0.48). However, the data-driven approach eliminated intermediate and mixed phenotypes and created acute rejection clusters that are each significantly associated with graft failure. Finally, a novel visualization tool presents disease phenotypes and severity in a continuous manner, as a complement to the discrete clusters.

CONCLUSIONS

A semisupervised clustering approach for the identification of clinically meaningful novel phenotypes of kidney transplant rejection has been developed and validated. The approach has the potential to offer a more quantitative evaluation of rejection subtypes and severity, especially in situations in which the current histologic categorization is ambiguous.

Replicative senescence and arteriosclerosis after kidney transplantation

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.

Risk factors, histopathological features, and graft outcome of transplant glomerulopathy in the absence of donor-specific HLA antibodies

Transplant glomerulopathy is established as a hallmark of chronic antibody-mediated rejection in kidney transplant patients with donor-specific HLA antibodies (HLA-DSA). The clinical importance of transplant glomerulopathy in the absence of HLA-DSA is not well established. To help define this, 954 patients (encompassing 3744 biopsies) who underwent kidney transplantation 2004-2013 were studied with retrospective high-resolution HLA genotyping of both donors and recipients. The risk factors, histopathological appearance and prognosis of cases with transplant glomerulopathy in the absence of HLA-DSA were compared to those cases with HLA-DSA, and the impact of the PIRCHE-II score and eplet mismatches on development of transplant glomerulopathy evaluated. In this cohort, 10.3% developed transplant glomerulopathy, on average 3.2 years post-transplant. At the time of glomerulopathy, 23.5% had persistent pre-transplant or de novo HLA-DSA, while 76.5% were HLA-DSA negative. Only HLA-DSA was identified as a risk factor for glomerulopathy development as eplet mismatches and the PIRCHE-II score did not associate. HLA-DSA negative biopsies with glomerulopathy had less interstitial inflammation, less glomerulitis, and less C4d deposition in the peritubular capillaries compared to the HLA-DSA positive biopsies with glomerulopathy. While graft function was comparable between the two groups, HLA-DSA positive glomerulopathy was associated with a significantly higher risk of graft failure compared to HLA-DSA negative glomerulopathy (Hazard Ratio 3.84; 95% confidence interval 1.94-7.59). Landmark analysis three-years post-transplant showed that HLA-DSA negative patients with glomerulopathy still had a significant increased risk of graft failure compared to patients negative for glomerulopathy (2.62; 1.46-4.72). Thus, transplant glomerulopathy often occurs in the absence of HLA-DSA, independent of HLA molecular mismatches, and represents a different phenotype with less concomitant inflammation and better graft survival compared to that developed in the presence of HLA-DSA.

Assessing the Complex Causes of Kidney Allograft Loss

BACKGROUND

Although graft loss is a primary endpoint in many studies in kidney transplantation and a broad spectrum of risk factors has been identified, the eventual causes of graft failure in individual cases remain ill studied.

METHODS

We performed a single-center cohort study in 1000 renal allograft recipients, transplanted between March 2004 and February 2013.

RESULTS

In total, 365 graft losses (36.5%) were identified, of which 211 (57.8%) were due to recipient death with a functioning graft and 154 (42.2%) to graft failure defined as return to dialysis or retransplantation. The main causes of recipient death were malignancy, infections, and cardiovascular disease. The main causes of graft failure were distinct for early failures, where structural issues and primary nonfunction prevailed, compared to later failures with a shift towards chronic injury. In contrast to the main focus of current research efforts, pure alloimmune causes accounted for only 17.5% of graft failures and only 7.4% of overall graft losses, although 72.7% of cases with chronic injury as presumed reason for graft failure had prior rejection episodes, potentially suggesting that alloimmune phenomena contributed to the chronic injury.

CONCLUSIONS

In conclusion, this study provides better insight in the eventual causes of graft failure, and their relative contribution, highlighting the weight of nonimmune causes. Future efforts aimed to improve outcome after kidney transplantation should align with the relative weight and expected impact of targeting these causes.

Hyperhomocysteinemia: a trigger for complement-mediated TMA?

A 34-year-old man of North African descent was referred to the emergency department because of malignant hypertension (220/113 mmHg), acute visual disturbances and acute kidney failure (serum creatinine 14.0 mg/dL). Blood analysis was compatible with thrombotic microangiopathy (TMA). Kidney biopsy confirmed this diagnosis with histological changes including intimal edema, arteriolar thrombi, and severe tubulointerstitial damage. Fundoscopy showed hypertensive retinopathy stage IV. Subsequent biochemical screening revealed normal complement testing and a marked elevation in homocysteine concentration (161 µmol/L; normal value 7-15 µmol/L). Other secondary causes of TMA were excluded. Further genetic testing for cobalamin C (cblC) deficiency showed no pathogenic mutations in the MMACHC gene. However, a homozygous c.665C>T polymorphism (NM_005957.4) in the methylenetetrahydrofolate reductase (MTHFR) gene was found explaining the severe hyperhomocysteinemia due to reduced activity of MTHFR. Additional genetic testing for alternative complement pathway proteins showed mutations in the genes encoding factor H and factor B, both categorized as possibly pathogenic using mutation prediction software. This is the first described case of TMA in a patient with severe hyperhomocysteinemia caused by a genetic defect other than cblC. We postulate that endothelial damage due to hyperhomocysteinemia and hypertension could have triggered the TMA episode in this patient with two possible predisposing pathogenic mutations in the alternative complement pathway. Furthermore, our case demonstrates the need for complete full diagnostic testing in patients with TMA.

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

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.

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

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.

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

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_neg group). With extended 2F-HR HLA genotyping, we confirmed 173 DSA (77.2%) in 108 (77.1%) patients (2F-HR_pos LR_pos DSA group) and excluded DSA in 32 patients (22.9%) (2F-HR_neg LR_pos DSA group). Kaplan-Meier curves showed that 10-year graft survival rates were similar between the DSA_neg and 2F-HR_neg LR_pos 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.

Universal newborn hearing screening: the Belgian experience

Issue

Worldwide 466 million people suffer from hearing loss (HL), of whom 34 million children. Early detection of HL in newborns through screening and subsequent intervention significantly improve their developmental and psychosocial outcome. The WHA adopted a resolution on prevention of deafness and HL (2017), urging the member states 'to develop, implement and monitor screening programs for early identification of ear diseases'. Population based newborn hearing screening (PNHS) by automated otoacoustic emission (AOAE) and/or automated auditory brainstem response (AABR) is considered good practice.

Description of the Problem

Flanders (FL): PNHS by AABR at the age of 2-3 weeks (pass/refer), repeated in case of 'refer'. At 2x 'refer', referral to a tertiary hearing center. French speaking community (FSC): newborns with risk factors for congenital HL are immediately referred to ENT. Others undergo AOAE at day 2-3 (pass/refer with retest in case of 'refer'). At 2x 'refer', referral to ENT for AABR. German speaking community: no data available.

Results

Coverage rate: FL (birth cohort 2014): 96-98%. FSC (birth cohort 2016): 94.9% of newborns without risk factors had a 1st test. 8.7% of newborns with risk factors didn't have any test.

Detection rate/1000 tested newborns

FL: 2.1 newborns with congenital HL. FSC: 2.33 newborns with HL (0.30 perceptive/0.36 permanently conductive/0.75 temporary conductive/0.1 conductive NOS/0.06 mixed type/0.77 NOS).

Lessons

Belgium has at least 2 quality PNHS programs. Due to program differences (different tests/age of testing/registration/financing) in depth comparative analysis on their performance, outcome and cost effectiveness is currently lacking (future perspective).

Key messages

PNHS is common in high income countries, but is not yet integrated worldwide. In the light of the 2017 WHA resolution Belgium might inspire regions and countries starting up PNHS. An in depth comparative analysis of the current Belgian PNHS programs is needed.

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

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

, setting, participants, & measurementsIn 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.

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

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 de novo 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

De novo DSAs occurred in 43 (4.6%) patients. Multivariable analysis showed a significant independent association between antibody-verified eplet mismatch load and de novo 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 de novo 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 de novo 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 DQA₁ and DQB₁ alleles could also help to minimize de novo DSA formation and potentially improve transplant outcomes.

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

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 IFNγ-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.

Whole-body diffusion-weighted magnetic resonance imaging for the detection of bone metastases and their prognostic impact in metastatic renal cell carcinoma patients treated with angiogenesis inhibitors

Background: Metastatic renal cell carcinoma (mRCC) patients with bone metastases (BM) are at high risk for skeletal related events and have a poorer outcome when treated with vascular endothelial growth factor receptor-tyrosine kinase inhibitors (VEGFR-TKIs). Computed tomography (CT) lacks sensitivity to detect BM in mRCC. We aimed to determine the added value of whole body diffusion-weighted magnetic resonance imaging (WB-DWI/MRI) to CT for the detection of BM in mRCC and to estimate the prognostic impact of the number of BM in mRCC patients treated with VEGFR-TKIs.Material and methods: We conducted a prospective study including consecutive mRCC patients treated with a first-line VEGFR-TKI in the metastatic setting. All patients underwent a pretreatment thoracic-abdominal-pelvic CT and WB-DWI/MRI. CT and WB-DWI/MRI were compared for the detection of BM. The number of detected BM was correlated with response rate (RR), progression-free survival (PFS) and overall survival (OS) after start of the VEGFR-TKI.Results: Ninety-two patients were included. BM were found in 55% of the patients by WB-DWI/MRI and in 43% of the patients by CT (p = .003). Mean number of BM discovered per patient was 6.8 by WB-DWI/MRI versus 1.9 by CT (p = .006). The cutoff of ≤5 versus >5 BM on WB-DWI/MRI had the highest discriminative power for all outcome measures. Patients with >5 BM had a lower RR (10% versus 42%), more frequently early progressive disease (43% versus 13%, p = .003), shorter PFS (4 versus 10 months, p = .006) and shorter OS (10 versus 35 months, p < .0001) compared to patients with ≤5 BM.Conclusion: WB-DWI/MRI detects significantly more BM in mRCC patients than CT, allowing better estimation of the prognostic impact of BM in mRCC patients treated with VEGFR-TKIs. The prognostic impact should now be validated in patients treated with immune checkpoint inhibitors.

Bone metastasis is associated with poor prognosis in metastatic papillary renal cell carcinoma patients treated with first agent angiogenesis inhibitors

OBJECTIVE

Papillary renal cell carcinoma (papRCC) is a rare (10%-15%) subtype of renal cancer. Few prognostic biomarkers have been described in metastatic papRCC (m-papRCC) patients treated with vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs). We aimed to study the prognostic impact of bone metastases (BM) on response rate, progression-free and overall survival (PFS and OS) in patients with m-papRCC treated with first agent VEGFR-TKIs.

PATIENTS AND METHODS

A multicentric, retrospective analysis of patient records was conducted. BM were detected by computed tomography and/or bone scintigraphy. The International Metastatic RCC Database Consortium (IMDC) score was calculated at start of first agent VEGFR-TKI treatment.

RESULTS

Forty-nine patients were included. Best objective response was partial response in 20%, stable disease in 60% and early progressive disease in 20% of patients. Median PFS (mPFS) was 6.0 months and median OS (mOS) 14.0 months after start of first agent VEGFR-TKI. The IMDC score correlated with mOS: 77.5 months in good, 17.0 months in intermediate and 8.0 months in poor risk patients (P = 0.002). Patients with BM had a poorer outcome compared to patients without BM: mPFS was 4.0 vs. 7.0 months (P = 0.006) and mOS 7.5 vs. 19.0 months (P = 0.002). On bivariate analysis, the presence of BM was independently associated with PFS (P = 0.02) and OS (P = 0.049), independent of the IMDC risk groups.

CONCLUSION

In m-papRCC patients treated with first agent VEGFR-TKIs, the presence of BM is an unfavorable prognostic factor, associated with shorter PFS and OS.

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

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.

Bone metastases and age are associated with earlier dose reductions in metastatic clear-cell renal cell carcinoma patients treated with angiogenesis inhibitors

Background: Metastatic clear-cell renal cell carcinoma (m-ccRCC) patients with bone metastases (BM) treated with vascular endothelial growth factor receptor (VEGFR) tyrosine kinase inhibitors (TKI) have a poorer outcome compared to patients without BM. We aimed to investigate whether an increased incidence of VEGFR-TKI treatment interruptions and/or dose reductions in patients with BM could explain this difference in outcome. Patients and methods: Retrospective study on m-ccRCC patients treated in first-line with VEGFR-TKI. Analysis of the incidence of treatment interruptions and dose reductions and time-to-event analysis. Study of the correlation with the presence of BM at start of first-line VEGFR-TKIs. Results: Two-hundred-and-five patients were included. In patients with BM, median time-to-dose-reduction was significantly shorter (3 versus 5 cycles; p = 0.005) than in patients without BM. 63% of the total number of cycles was administered at reduced dose, compared to 41% in patients without BM. Age at start of VEGFR-TKI (≤ versus >70 years) was significantly associated with median time-to-dose-reduction (5 versus 3 cycles; p = 0.007). On multivariate analysis, the presence of BM (p = 0.004; HR 1.82, 95%CI 1.21-2.73) and age at start of VEGFR-TKIs (p = 0.017; HR 1.65, 95%CI 1.10-2.50) were independently associated with time-to-dose-reduction. Conclusion: In m-ccRCC patients treated with VEGFR-TKIs, dose reductions occurred earlier in patients with BM compared to patients without BM and in elderly patients.

Granulomatosis with polyangiitis with breast involvement mimicking metastatic cancer: Case report and literature review

Granulomatosis with polyangiitis (GPA) is a systemic inflammatory disease, characterized by the presence of necrotizing vasculitis of small and medium-sized vessels, granulomatous inflammation and anti-neutrophil cytoplasmic antibodies (ANCAs). The diagnosis can be challenging due to the variable clinical presentation and possible involvement of virtually all organ systems. A correct diagnosis is indispensable for a timely start of medical treatment and to avoid unnecessary surgery. Therefore, cooperation with and the input of the pathologist is crucial. We report a case of a woman presenting with suspected metastatic cancer. The diagnosis of GPA was made mainly based on breast biopsy, and the patient was treated accordingly, with full recovery. This report provides a case description and a brief review of the literature.

Specificity, strength, and evolution of pretransplant donor-specific HLA antibodies determine outcome after kidney transplantation

In this cohort study (N = 924), we investigated the evolution and clinical significance of pretransplant donor-specific HLA antibodies (preDSA), detected in the single-antigen beads assay but complement-dependent cytotoxicity crossmatch-negative. Donor specificity of the preDSA (N = 107) was determined by high-resolution genotyping of donor-recipient pairs. We found that in 52% of the patients with preDSA, preDSA spontaneously resolved within the first 3 months posttransplant. PreDSA that persisted posttransplant had higher pretransplant median fluorescence intensity values and more specificity against DQ. Patients with both resolved and persistent DSA had a high incidence of histological picture of antibody-mediated rejection (ABMR_h ; 54% and 59% respectively). Patients with preDSA that persisted posttransplant had worse 10-year graft survival compared to resolved DSA and preDSA-negative patients. Compared to cases without preDSA, Cox modeling revealed an increased risk of graft failure only in the patients with persistent DSA, in the presence (hazard ratio [HR] = 8.3) but also in the absence (HR = 4.3) of ABMR_h . In contrast, no increased risk of graft failure was seen in patients with resolved DSA. We conclude that persistence of preDSA posttransplant has a negative impact on graft survival, beyond ABMR_h . Even in the absence of antibody-targeting therapy, low median fluorescence intensity DSA and non-DQ preDSA often disappear early posttransplantation and are not deleterious for graft outcome.

Development and validation of a peripheral blood mRNA assay for the assessment of antibody-mediated kidney allograft rejection: A multicentre, prospective study

Background

Antibody-mediated rejection, a leading cause of renal allograft graft failure, is diagnosed by histological assessment of invasive allograft biopsies. Accurate non-invasive biomarkers are not available.

Methods

In the multicentre, prospective BIOMARGIN study, blood samples were prospectively collected at time of renal allograft biopsies between June 2011 and August 2016 and analyzed in three phases. The discovery and derivation phases of the study (N = 117 and N = 183 respectively) followed a case-control design and included whole genome transcriptomics and targeted mRNA expression analysis to construct and lock a multigene model. The primary end point was the diagnostic accuracy of the locked multigene assay for antibody-mediated rejection in a third validation cohort of serially collected blood samples (N = 387). This trial is registered with ClinicalTrials.gov, number NCT02832661.

Findings

We identified and locked an 8-gene assay (CXCL10, FCGR1A, FCGR1B, GBP1, GBP4, IL15, KLRC1, TIMP1) in blood samples from the discovery and derivation phases for discrimination between cases with (N = 49) and without (N = 134) antibody-mediated rejection. In the validation cohort, this 8-gene assay discriminated between cases with (N = 41) and without antibody-mediated rejection (N = 346) with good diagnostic accuracy (ROC AUC 79·9%; 95% CI 72·6 to 87·2, p < 0·0001). The diagnostic accuracy of the 8-gene assay was retained both at time of stable graft function and of graft dysfunction, within the first year and also later after transplantation. The 8-gene assay is correlated with microvascular inflammation and transplant glomerulopathy, but not with the histological lesions of T-cell mediated rejection.

Interpretation

We identified and validated a novel 8-gene expression assay that can be used for non-invasive diagnosis of antibody-mediated rejection.

Funding

The Seventh Framework Programme (FP7) of the European Commission.

A Peripheral Blood Gene Expression Signature to Diagnose Subclinical Acute Rejection

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Persistent primary cytomegalovirus infection in a kidney transplant recipient: Multi-drug resistant and compartmentalized infection leading to graft loss

Cytomegalovirus (CMV) is one of the most common opportunistic infections after transplantation. To prevent CMV infections, universal prophylaxis and pre-emptive therapy with ganciclovir or its prodrug valganciclovir is applied. However, prolonged antiviral therapy may result in drug-resistance emergence. We describe a case of a 43-year-old CMV-seronegative patient who underwent kidney transplantation from a CMV-seropositive donor and developed CMV disease despite valganciclovir prophylaxis. CMV viral load increased even though valgangiclovir dose was augmented and immunosuppressive therapy reduced. CMV genotyping revealed mutations in the viral UL97 protein kinase, explaining ganciclovir-resistant CMV infection. The viral load failed to respond to foscavir, cidofovir and CMV-neutralizing immunoglobulins. Kidney allograft dysfunction developed 3 months post-transplantation with a histopathologic diagnosis of CMV nephropathy and potentially concomitant T-cell mediated rejection. A transplantectomy was performed on day 164 post-transplantation since the patient had uncontrollable CMV disease associated with a circulating multidrug-resistant DNA polymerase-mutant virus. Detailed monitoring in this patient demonstrated hallmarks of complicated CMV disease: (i) relatively rapid evolution of drug-resistant CMV mutants in the setting of persistent high blood viral loads, (ii) emergence of viral drug-resistance linked to acute graft rejection, (iii) transient and, thereafter, lack of response to various anti-CMV treatments, (iv) compartmentalization and heterogeneity of CMV viral populations, (v) possible differential ability of viral mutants to cause disease in the graft, and (vi) detection of minor viral variants by next generation sequencing. Translational research platforms that provide rapid molecular genotyping for detection of CMV drug-resistance are essential in guiding CMV disease management in high-risk transplant recipients.

ABCG2 Polymorphism rs2231142 and hypothyroidism in metastatic renal cell carcinoma patients treated with sunitinib

BACKGROUND AND AIM

Vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) cause significant adverse events including thyroid dysfunction, mainly hypothyroidism, in a considerable proportion of patients. In a series of metastatic renal cell carcinoma (mRCC) patients treated with sunitinib, we aimed to study the correlation between hypothyroidism and single nucleotide polymorphisms (SNPs) in genes involved in sunitinib pharmacokinetics and pharmacodynamics.

PATIENTS AND METHODS

We included 79 mRCC patients who started sunitinib between November 2005 and March 2016. Serum thyroid function markers were collected at start and during sunitinib therapy. Germ-line DNA genotyping for 16 SNPs in 8 candidate genes was performed. Endpoints were time to increase in thyroid stimulating hormone (TSH) and time to decrease in T4 or free T4 (FT4) on day 1 and day 28 of each sunitinib cycle.

RESULTS

Patients with the ABCG2 rs2231142 CC-genotype had a significantly longer time-to-TSH-increase on day 1 (11 vs. 5 cycles; p = 0.0011), and time-to-T4/FT4-decrease on day 1 (not reached vs. 10 cycles; p = 0.013) and day 28 (28 vs. 7 cycles; p = 0.03) compared to CA-carriers. Patients with the CYP3A5 rs776746 GG-genotype had a significantly longer time-to-TSH-increase at day 1 compared to GA-patients: 11 vs. 5 cycles (p = 0.0071). Significant associations were also found between PDGFRA rs35597368 and rs1800812 and time-to-TSH-increase at day 28.

CONCLUSION

Polymorphism rs2231142 in the efflux pump ABCG2 is associated with hypothyroidism in mRCC patients treated with sunitinib.

Prospective evaluation of hypogonadism in male metastatic renal cell carcinoma patients treated with targeted therapies

OBJECTIVES

To study the prevalence of hypogonadism in male patients with metastatic renal cell carcinoma (mRCC) starting with targeted therapies and the impact of the vascular endothelial growth factor receptor tyrosine kinase inhibitors (VEGFR-TKIs) sunitinib and pazopanib on the luteinizing hormone (LH)/testosterone (TT)-axis.

METHODS

Male mRCC patients starting with targeted therapies were prospectively included in this study. TT- and LH-levels were sampled at start as well as during systemic therapy. Endpoints of the study were gonadal status (TT- and LH-levels) at start of targeted therapy and TT- and LH-evolution during targeted therapy.

RESULTS

Sixty-three patients were included in this study. At start of targeted therapy, 30% of patients were eugonadal and 48% had secondary hypogonadism. Decreased TT- and increased LH-levels were associated with inflammatory state and poor prognosis. During sunitinib therapy, TT-levels decreased with 32% (p = 0.004) and LH-levels with 14% (p = 0.03). TT-levels were 13% lower (p = 0.007) and LH-levels 15% lower (p = 0.004) on day 28 compared to day 1. In four patients, a dramatic TT decrease was observed shortly after starting sunitinib. In patients treated with pazopanib, no impact on TT- or LH-levels was observed.

CONCLUSION

Hypogonadism is a frequent finding in male mRCC-patients at start of targeted therapies. In contrast to pazopanib, during sunitinib therapy, TT- and LH-levels tend to decrease, leading to an increased incidence of secondary hypogonadism.

Occurrence of Diabetic Nephropathy After Renal Transplantation Despite Intensive Glycemic Control: An Observational Cohort Study

OBJECTIVE

The kinetics and risk factors of diabetic nephropathy after kidney transplantation remain unclear. This study investigated the posttransplant occurrence of diabetic nephropathy and the contribution of posttransplant glycemic control.

RESEARCH DESIGN AND METHODS

We performed a single-center prospective cohort study of 953 renal allograft recipients and 3,458 protocol-specified renal allograft biopsy specimens up to 5 years after transplantation. The effects of pretransplant diabetes and glycemic control (glycated hemoglobin levels) on the posttransplant histology were studied.

RESULTS

Before transplantation, diabetes was present in 164 (17.2%) renal allograft recipients, primarily type 2 (n = 146 [89.0%]). Despite intensive glycemic control (glycated hemoglobin 7.00 ± 1.34% [53 ± 14.6 mmol/mol], 6.90 ± 1.22% [52 ± 13.3 mmol/mol], and 7.10 ± 1.13% [54 ± 12.4 mmol/mol], at 1, 2, and 5 years after transplantation), mesangial matrix expansion reached a cumulative incidence of 47.7% by 5 years in the pretransplant diabetes group versus 27.1% in patients without diabetes, corresponding to a hazard ratio of 1.55 (95% CI 1.07-2.26; P = 0.005). Mesangial matrix expansion was not specific for diabetic nephropathy and associated independently with increasing age. Pretransplant diabetes was associated with posttransplant proteinuria but not with estimated glomerular filtration rate, graft failure, or any other structural changes of the glomerular, vascular, or tubulointerstitial renal compartments. The occurrence of diabetic nephropathy was independent of posttransplant glycated hemoglobin levels.

CONCLUSIONS

Mesangial matrix expansion, an early indicator of diabetic nephropathy, can occur rapidly in patients with diabetes before transplantation, despite intensive glycemic control. Prevention of diabetic nephropathy requires more than pursuing low levels of glycated hemoglobin.

Histological picture of antibody-mediated rejection without donor-specific anti-HLA antibodies: Clinical presentation and implications for outcome

In this cohort study (n = 935 transplantations), we investigated the phenotype and risk of graft failure in patients with histological criteria for antibody-mediated rejection (ABMR) in the absence of circulating donor-specific anti-human leukocyte antigen (HLA) antibodies (DSA), and compared this to patients with definite ABMR and HLA-DSA-positivity. The histological picture did not differ between HLA-DSA-positive (n = 85) and HLA-DSA-negative (n = 123) cases of ABMR histology, apart from increased complement split product 4d (C4d) deposition in the peritubular capillaries in HLA-DSA-positive cases. Histology of ABMR without HLA-DSA was more transient than DSA-positive ABMR, and patients with ABMR histology without HLA-DSA had graft survival superior to that of HLA-DSA-positive patients, independent of concomitant T cell-mediated rejection (38.2%) or borderline changes (17.9%). Multivariate analysis showed that the risk of graft failure was not higher in patients with histological picture of ABMR (ABMR_h ) in the absence of HLA-DSA, compared to patients without ABMR_h . Despite an association between C4d deposition and HLA-DSA-positivity, using C4d deposition as alternative for the DSA criterion in the diagnosis of ABMR, as proposed in Banff 2017, did not contribute to the prognosis of graft function and graft failure. We concluded that biopsies with ABMR_h but without detectable HLA-DSA represent a distinct, often transient phenotype with superior allograft survival.

Natural killer cell infiltration is discriminative for antibody-mediated rejection and predicts outcome after kidney transplantation

Despite partial elucidation of the pathophysiology of antibody-mediated rejection (ABMR) after kidney transplantation, it remains largely unclear which of the involved immune cell types determine disease activity and outcome. We used microarray transcriptomic data from a case-control study (n=95) to identify genes that are differentially expressed in ABMR. Given the co-occurrence of ABMR and T-cell-mediated rejection (TCMR), we built a bioinformatics pipeline to distinguish ABMR-specific mRNA markers. Differential expression of 503 unique genes was identified in ABMR, with significant enrichment of natural killer (NK) cell pathways. CIBERSORT (Cell type Identification By Estimating Relative Subsets Of known RNA Transcripts) deconvolution analysis was performed to elucidate the corresponding cell subtypes and showed increased NK cell infiltration in ABMR in comparison to TCMR and normal biopsies. Other leukocyte types (including monocytes/macrophages, CD4 and CD8 T cells, and dendritic cells) were increased in rejection, but could not discriminate ABMR from TCMR. Deconvolution-based estimation of NK cell infiltration was validated using computerized morphometry, and specifically associated with glomerulitis and peritubular capillaritis. In an external data set of kidney transplant biopsies, activated NK cell infiltration best predicted graft failure amongst all immune cell subtypes and even outperformed a histologic diagnosis of acute rejection. These data suggest that NK cells play a central role in the pathophysiology of ABMR and graft failure after kidney transplantation.

Ischemia-Induced DNA Hypermethylation during Kidney Transplant Predicts Chronic Allograft Injury

Background Ischemia during kidney transplant causes chronic allograft injury and adversely affects outcome, but the underlying mechanisms are incompletely understood. In tumors, oxygen shortage reduces the DNA demethylating activity of the ten-11 translocation (TET) enzymes, yielding hypermethylated genomes that promote tumor progression. We investigated whether ischemia similarly induces DNA hypermethylation in kidney transplants and contributes to chronic injury.Methods We profiled genome-wide DNA methylation in three cohorts of brain-dead donor kidney allograft biopsy specimens: a longitudinal cohort with paired biopsy specimens obtained at allograft procurement (preischemia; n=13), after implantation and reperfusion (postischemia; n=13), and at 3 or 12 months after transplant (n=5 each); a cross-sectional cohort with preimplantation biopsy specimens (n=82); and a cross-sectional cohort with postreperfusion biopsy specimens (n=46).Results Analysis of the paired preischemia and postischemia specimens revealed that methylation increased drastically in all allografts on ischemia. Hypermethylation was caused by loss of 5-hydroxymethylcytosine, the product of TET activity, and it was stable 1 year after transplant. In the preimplantation cohort, CpG hypermethylation directly correlated with ischemia time and for some CpGs, increased 2.6% per additional hour of ischemia. Hypermethylation preferentially affected and reduced the expression of genes involved in suppressing kidney injury and fibrosis. Moreover, CpG hypermethylation in preimplantation specimens predicted chronic injury, particularly fibrosis and glomerulosclerosis, 1 year after transplant. This finding was validated in the independent postreperfusion cohort, in which hypermethylation also predicted reduced allograft function 1 year after transplant, outperforming established clinical variables.Conclusions We highlight a novel epigenetic basis for ischemia-induced chronic allograft injury with biomarker potential.

Pro-angiogenic gene expression is associated with better outcome on sunitinib in metastatic clear-cell renal cell carcinoma

OBJECTIVES

Clear-cell renal cell carcinomas (ccRCC) are characterized by hyper-vascularization and can respond to vascular endothelial growth factor receptor (VEGFR) inhibitors such as sunitinib. We aimed to study the predictive value of the expression of genes in the hypoxia induced factor (HIF) - vascular endothelial growth factor (VEGF) - VEGFR-pro-angiogenic pathway in metastatic ccRCC (m-ccRCC) patients treated with sunitinib and the correlation between the expression of these genes and the molecular ccrcc-classification, the expression of genes involved in the immune-suppressive microenvironment and Von Hippel-Lindau (VHL) - and Polybromo-1 (PBRM1) - mutational status.

MATERIAL AND METHODS

m-ccRCC patients treated with sunitinib as first-line targeted therapy were included. Gene expression was studied in the primary nephrectomy sample by qRT-PCR, VHL- and PBRM1-mutational status by sequencing. Response rate by RECIST, progression-free survival (PFS) and overall survival (OS) were study endpoints.

RESULTS

One hundred and four patients were included. On multivariate-analysis, HIF2A-, platelet derived growth factor receptor beta (PDGFRB)-, VEGFC-, VEGFR1- and VEGFR2-expression were correlated with PFS and HIF1A-, HIF2A-, VEGFR1- and VEGFR2-expression with OS. VEGFR2-expression showed the strongest association with outcome, being significantly correlated with all outcome parameters. HIF2A, VEGFA, VEGFR1, VEGFR2 and VEGFR3 were highly expressed in the transcriptomic ccrcc2-subtype of tumors, known to be highly sensitive to sunitinib. In the total tumor series, there was no correlation nor inverse correlation between the expression of genes involved in angiogenesis and in the immune-suppressive microenvironment. In tumors with a bi-allelic PBRM1-inactivation, HIF2A-, VEGFA-, VEGFR1- and VEGFR2-expression were higher, compared to tumors with one or two functional PBRM1-alleles.

CONCLUSIONS

Intratumoral expression of genes involved in the HIF-VEGF-VEGFR-pro-angiogenic pathway, especially VEGFR2, is associated with favorable outcome on sunitinib in m-ccRCCs. Several genes involved in this pathway are upregulated in the molecular ccrcc2-subgroup, which usually responds well to sunitinib.

Acute renal failure with need for renal replacement therapy as a complication of zoonotic S. zooepidemicus infection: case report and review of the literature

Streptococcus zooepidemicus is an animal commensal with the potential of zoonotic transmission through ingestion of contaminated dairy products, leading to outbreaks of Post-Streptococcal Glomerulonephritis (PSGN). We report for the first time acute renal failure with need for renal replacement therapy, as a complication of S. zooepidemicus bacteremia resulting from direct horse to human transmission in a young adult. Both clinical disease course and immunohistochemical staining patterns on renal biopsy had some atypical features of PSGN suggesting persistent activation of the alternative complement pathway but no known complement factor dysregulations could be identified.

Postconditioning effects of argon or xenon on early graft function in a porcine model of kidney autotransplantation

BACKGROUND

Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Preconditioning, reconditioning and postconditioning with argon and xenon protects against renal ischaemia-reperfusion injury in rodent models. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function in a porcine renal autotransplant model was tested.

METHODS

Pigs (n = 6 per group) underwent left nephrectomy after 60 min of warm ischaemia (renal artery and vein clamping). The procured kidney was autotransplanted in a separate procedure after 18 h of cold storage, immediately after a right nephrectomy. Upon reperfusion, pigs were randomized to inhalation of control gas (70 per cent nitrogen and 30 per cent oxygen), argon (70 per cent and 30 per cent oxygen) or xenon (70 per cent and 30 per cent oxygen) for 2 h. The primary outcome parameter was peak plasma creatinine; secondary outcome parameters included further markers of graft function (creatinine course, urine output), graft injury (aspartate aminotransferase, heart-type fatty acid-binding protein, histology), apoptosis and autophagy (western blot, terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) staining), inflammatory mediators and markers of cell survival/growth (mRNA and tissue protein quantification), and animal survival. Results are presented as median (i.q.r.). ANOVA and Kruskal-Wallis tests were used where indicated.

RESULTS

Peak plasma creatinine levels were similar between the groups: control 20·8 (16·4-23·1) mg/dl, argon 21·4 (17·1-24·9) mg/dl and xenon 19·4 (17·5-21·0) mg/dl (P = 0·607). Xenon was associated with an increase in autophagy and proapoptotic markers. Creatinine course, urine output, injury markers, histology, survival and inflammatory mediators were not affected by the intervention.

CONCLUSION

Postconditioning with argon or xenon did not improve kidney graft function in this experimental model. Surgical relevance Ischaemia-reperfusion injury is inevitable during renal transplantation and can lead to delayed graft function and primary non-function. Based on mainly small animal experiments, noble gases (argon and xenon) have been proposed to minimize this ischaemia-reperfusion injury and improve outcomes after transplantation. The hypothesis that postconditioning with argon or xenon inhalation would improve graft function was tested in a porcine kidney autotransplantation model. The peak plasma creatinine concentration was similar in the control, argon and xenon groups. No other secondary outcome parameters, including animal survival, were affected by the intervention. Xenon was associated with an increase in autophagy and proapoptotic markers. Despite promising results in small animal models, postconditioning with argon or xenon in a translational model of kidney autotransplantation was not beneficial. Clinical trials would require better results.

Patched 1 Expression Correlates with Biochemical Relapse in High-Risk Prostate Cancer Patients

There is an unmet clinical need for adequate biomarkers to aid risk stratification and management of prostate cancer (PCa) patients. Even within the high-risk PCa category, not all patients will invariably have a poor prognosis, and improved stratification of this heterogeneous group is needed. In this context, components of the hedgehog (Hh) pathway may have promise as biomarkers, because the available evidence suggests increased Hh pathway activity may confer a poorer outcome in advanced and castrate-resistant PCa. In this study, potential associations between Hh pathway protein expression and clinicopathological factors, including time to biochemical recurrence (BCR), were investigated using a tissue microarray constructed from benign and malignant prostate samples from 75 predominantly high-risk PCa patients who underwent radical prostatectomy. Hh signaling activity was found to differ between benign and malignant prostate tissue, with a greater amount of active Hh signaling present in malignant than benign prostate epithelium. High expression of Patched 1 in malignant prostate epithelium was found to be an independent predictor of BCR in high-risk PCa patients. Glioma-associated oncogene 1 may potentially represent a clinically useful biomarker of an aggressive tumor phenotype. Evaluation of Hh signaling activity in PCa patients may be useful for risk stratification, and epithelial Patched 1 expression, in particular, may be a prognostic marker for BCR in high-risk PCa patients.

Effect of crizotinib on disease control in patient with advanced papillary renal cell carcinoma type 1 with MET mutations or amplification: Final results of EORTC 90101 CREATE

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Background: Papillary renal cell carcinoma type 1(PRCC1) is associated with MET alterations. Our phase II trial assessed the efficacy and safety of crizotinib in patients (pts) with advanced/metastatic PRCC1 with/without MET mutations( MET+, MET-). Methods: Eligible pts with reference pathology-confirmed PRCC1 received oral crizotinib 250mg twice-daily. Pts were attributed to MET+/ MET- sub-cohorts by sequencing of MET exons 16-19 in tumour tissue. Primary endpoint was objective response rate (ORR). If at least 2 of the first 12 eligible/evaluable MET+ pts achieved a confirmed partial (PR) or complete response (RECIST 1.1), a maximum of 35 pts were enrolled. Other endpoints included duration of response (DOR), disease control rate (DCR), progression-free survival (PFS) and rate (PFSR), overall survival (OS) and safety. Results: 23 of 41 pts consenting were eligible, treated and evaluable. In 4 MET+ pts, 2 achieved a PR and 1 had stable disease (SD) (ORR 50%; 95% CI: 6.8-93.7%), DOR was 666 and 1138 days, 1-year PFSR was 75.0% (12.8-96.1%), 1-year OS: 75.0% (12.8-96.1%). Among 16 MET- pts, 1 achieved a PR lasting 302+ days and 11 had SD (ORR: 6.3%; 0.2-30.2%), 1-year PFSR: 27.3% (8.5-50.4%), 1-year OS: 71.8% (41.1-88.4%). Among 3 pts with unknown MET status ( MET?) due to technical failure, 1 achieved a PR lasting 211+ days and 1 had SD (ORR 33.3%, 0.8%-90.6%), 1-year PFSR: 66.7% (5.4-94.5%), 1-year OS: 100%. MET amplification was found post hoc in 1 MET+ (PR, DOR: 1138 days) and 1 MET- case (SD). Common treatment-related AEs were oedema (47.8%), fatigue (47.8%), nausea (39.1%), diarrhoea (39.1%), and blurred vision (34.8%). Conclusions: Crizotinib is active and well tolerated in advanced, metastatic PRCC1, achieving objective responses and long-lasting disease control in pts with MET mutations or amplification. Sporadic, durable responses are also seen in MET-/ MET? cases, suggesting the presence of other alterations of MET or alternative pathways. Clinical trial information: NCT01524926.