Outcomes in ANCA-Associated Vasculitis in Scotland: Validation of the Renal Risk Score in a Complete National Cohort.

Introduction: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) causes autoimmune-mediated inflammation of small blood vessels in multiple organs, including the kidneys. The ability to accurately predict kidney outcomes would enable a more personalized therapeutic approach. Methods: We used our national renal biopsy registry to validate the ability of ANCA Renal Risk Score (ARRS) to predict end-stage kidney disease (ESKD) for individual patients. This score uses histopathological and biochemical data to stratify patients as high, medium, or low risk for developing ESKD. Results: A total of 288 patients were eligible for inclusion in the study (low risk n = 144, medium risk n = 122, high risk n = 12). Using adjusted Cox proportional hazard models with the low-risk group as reference, we show that outcome differs between the categories: high-risk hazard ratio (HR) 16.69 (2.91-95.81, P = 0.002); medium risk HR 4.14 (1.07-16.01, P = 0.039). Incremental multivariable-adjusted Cox proportional hazards models demonstrated that adding ARRS to a model adjusted for multiple clinical parameters enhanced predictive discrimination (basic model C-statistic 0.864 [95% CI 0.813-0.914], basic model plus ARRS C-statistic 0.877 [95% CI 0.823-0.931]; P <0.01). Conclusion: The ARRS better discriminates risk of ESKD in AAV and offers clinicians more prognostic information than the use of standard biochemical and clinical measures alone. This is the first time the ARRS has been validated in a national cohort. The proportion of patients with high-risk scores is lower in our cohort compared to others and should be noted as a limitation of this study.

Risk Stratification to Predict Renal Survival in Anti-Glomerular Basement Membrane Disease.

SIGNIFICANCE STATEMENT: Most patients with anti-glomerular basement membrane (GBM) disease present with rapidly progressive glomerulonephritis, and more than half develop ESKD. Currently, no tools are available to aid in the prognostication or management of this rare disease. In one of the largest assembled cohorts of patients with anti-GBM disease (with 174 patients included in the final analysis), the authors demonstrated that the renal risk score for ANCA-associated vasculitis is transferable to anti-GBM disease and the renal histology is strongly predictive of renal survival and recovery. Stratifying patients according to the percentage of normal glomeruli in the kidney biopsy and the need for RRT at the time of diagnosis improves outcome prediction. Such stratification may assist in the management of anti-GBM disease. BACKGROUND: Prospective randomized trials investigating treatments and outcomes in anti-glomerular basement membrane (anti-GBM) disease are sparse, and validated tools to aid prognostication or management are lacking. METHODS: In a retrospective, multicenter, international cohort study, we investigated clinical and histologic parameters predicting kidney outcome and sought to identify patients who benefit from rescue immunosuppressive therapy. We also explored applying the concept of the renal risk score (RRS), currently used to predict renal outcomes in ANCA-associated vasculitis, to anti-GBM disease. RESULTS: The final analysis included 174 patients (out of a total of 191). Using Cox and Kaplan-Meier methods, we found that the RRS was a strong predictor for ESKD. The 36-month renal survival was 100%, 62.4%, and 20.7% in the low-risk, moderate-risk, and high-risk groups, respectively. The need for renal replacement therapy (RRT) at diagnosis and the percentage of normal glomeruli in the biopsy were independent predictors of ESKD. The best predictor for renal recovery was the percentage of normal glomeruli, with a cut point of 10% normal glomeruli providing good stratification. A model with the predictors RRT and normal glomeruli ( N ) achieved superior discrimination for significant differences in renal survival. Dividing patients into four risk groups led to a 36-month renal survival of 96.4% (no RRT, N ≥10%), 74.0% (no RRT, N <10%), 42.3% (RRT, N ≥10%), and 14.1% (RRT, N <10%), respectively. CONCLUSIONS: These findings demonstrate that the RRS concept is transferrable to anti-GBM disease. Stratifying patients according to the need for RRT at diagnosis and renal histology improves prediction, highlighting the importance of normal glomeruli. Such stratification may assist in the management of anti-GBM disease. PODCAST: This article contains a podcast at https://dts.podtrac.com/redirect.mp3/www.asn-online.org/media/podcast/JASN/2023_02_27_JASN0000000000000060.mp3.

Bevacizumab-associated glomerular microangiopathy.

Bevacizumab is a humanized monoclonal IgG1 antibody, which neutralizes vascular endothelial growth factor and is used for treating multiple cancer types. As a known and frequent adverse event, this therapy can lead to renal damage including proteinuria and nephrotic syndrome. In a retrospective approach, we analyzed 17 renal biopsies from patients receiving bevacizumab treatment. We observed a distinctive histopathological pseudothrombotic pattern different from the previously reported thrombotic microangiopathy. Since this pattern includes some features similar to acute and chronic thrombotic microangiopathy, focal segmental glomerulosclerosis and cryoglobulinemic membranoproliferative glomerulonephritis, biopsies with these diagnoses were included for comparison. Clinical, laboratory, light microscopic, immunohistochemical (including a proximity ligation assay), proteomic and electron microscopic features were assessed. Nephrotic syndrome was present in 15 of the 17 bevacizumab-treated patients. All 17 displayed a patchy pattern of variably PAS-positive hyaline pseudothrombi occluding markedly dilated glomerular capillaries in their biopsies. Mass spectrometry-based proteome analysis revealed a special protein pattern demonstrating some features of thrombotic microangiopathy and some of cryoglobulinemic glomerulonephritis, including a strong accumulation of IgG in the pseudothrombi. Proximity ligation assay did not show interaction of IgG with C1q, arguing for accumulation without classic pathway complement activation. In contrast to thrombi in thrombotic microangiopathy cases, the hyaline pseudothrombi did not contain clusters of CD61-positive platelets. Electron microscopy of bevacizumab cases did not show fibrin polymers or extensive loss of podocyte foot processes. Even though cases of bevacizumab-associated microangiopathy share some features with thrombotic microangiopathy, its overall histopathological pattern is quite different from acute or chronic thrombotic microangiopathy cases. We conclude that bevacizumab therapy can lead to a unique hyaline occlusive glomerular microangiopathy, likely arising from endothelial leakage followed by subendothelial accumulation of serum proteins. It can be diagnosed by light microscopy and is an important differential diagnosis in cancer patients with nephrotic syndrome.

Development and validation of a renal risk score in ANCA-associated glomerulonephritis.

Predicting renal outcome in antineutrophil cytoplasmic antibody (ANCA)-associated glomerulonephritis (GN) remains a major challenge. We aimed to identify reliable predictors of end-stage renal disease (ESRD) and to develop and validate a clinicopathologic score to predict renal outcome in ANCA-associated GN. In a prospective training cohort of 115 patients, the percentage of normal glomeruli (without scarring, crescents, or necrosis within the tuft) was the strongest independent predictor of death-censored ESRD. Regression tree analysis identified predictive cutoff values for three parameters: percentage normal glomeruli (N0 >25%, N1 10 to 25%, N2 <10%), percentage tubular atrophy and interstitial fibrosis (T0 ≤25%, T1 >25%), and estimated glomerular filtration rate at the time of diagnosis (G0 >15 ml/min/1.73 m2, G1 ≤15 ml/min/1.73 m2). Cox regression analysis was used to assign points to each parameter (N1 = 4, N2 = 6, T1 = 2, G1 = 3 points), and the resulting risk score was used to classify predicted ESRD risk as low (0), intermediate (2 to 7), or high (8 to 11 points). The risk score accurately predicted ESRD at 36 months in the training cohort (0%, 26%, and 68%, respectively) and in an independent validation cohort of 90 patients (0%, 27%, and 78%, respectively). Here, we propose a clinically applicable renal risk score for ANCA-associated GN that highlights the importance of unaffected glomeruli as a predictor of renal outcome and allows early risk prediction of ESRD.

Organisation of lymphocytic infiltrates in ANCA-associated glomerulonephritis.

AIMS: Renal involvement in anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis contributes to significant morbidity and mortality in patients. In chronic inflammation, B cells are recruited to the inflamed tissue and organised lymphoid structures have been described in several autoimmune diseases. The aim of this study was to correlate the lymphoid organisation in renal biopsies with renal outcome in ANCA-associated glomerulonephritis (GN). METHODS AND RESULTS: We investigated 112 renal biopsies from patients with newly diagnosed ANCA-associated necrotising GN. We identified four different levels of the intrarenal organisation of lymphocytes: T cells without B cells, scattered B and T cells, clustered lymphocytic infiltrates and nodular compartmentally arranged B and T cell aggregates. Almost half the patients showed clusters of B and T lymphocytes in their biopsies. In 15 of these biopsies, a higher degree of organisation with lymphocytic compartments was detected. Inflammatory cell organisation was associated with renal failure, but not with tubular atrophy and interstitial fibrosis. Patients with organised lymphocytic infiltrates in their biopsy had worse renal function during follow-up and were more likely to develop end stage renal disease. CONCLUSIONS: In the present study, we show that the renal lymphocytic organisation is associated with renal outcome in ANCA-associated GN. The organisation of the lymphocytic infiltrate may be a morphological correlate of a perpetual and exaggerated inflammation in renal ANCA disease. Classifying the lymphocytic infiltrate could help to predict renal outcome, and might therefore be used for individualised adjustments in the intensity and duration of immunosuppressive therapy.

IL-17C/IL-17 Receptor E Signaling in CD4+ T Cells Promotes TH17 Cell-Driven Glomerular Inflammation.

The IL-17 cytokine family and the cognate receptors thereof have a unique role in organ-specific autoimmunity. Most studies have focused on the founding member of the IL-17 family, IL-17A, as the central mediator of diseases. Indeed, although pathogenic functions have been ascribed to IL-17A and IL-17F in the context of immune-mediated glomerular diseases, the specific functions of the other IL-17 family members in immunity and inflammatory kidney diseases is largely unknown. Here, we report that compared with healthy controls, patients with acute Anti-neutrophil cytoplasmatic antibody (ANCA)-associated crescentic glomerulonephritis (GN) had significantly elevated serum levels of IL-17C (but not IL-17A, F, or E). In mouse models of crescentic GN (nephrotoxic nephritis) and pristane-induced lupus nephritis, deficiency in IL-17C significantly ameliorated the course of GN in terms of renal tissue injury and kidney function. Deficiency of the unique IL-17C receptor IL-17 receptor E (IL-17RE) provided similar protection against crescentic GN. These protective effects associated with a reduced TH17 response. Bone marrow transplantation experiments revealed that IL-17C is produced by tissue-resident cells, but not by lymphocytes. Finally, IL-17RE was highly expressed by CD4+ TH17 cells, and loss of this expression prevented the TH17 responses and subsequent tissue injury in crescentic GN. Our findings indicate that IL-17C promotes TH17 cell responses and immune-mediated kidney disease via IL-17RE expressed on CD4+ TH17 cells. Targeting the IL-17C/IL-17RE pathway may present an intriguing therapeutic strategy for TH17-induced autoimmune disorders.

Disseminated Mycobacterium haemophilum infection in a renal transplant recipient.

Opportunistic infections are a major concern in renal and transplant medicine. We present the case of a renal transplant recipient with a generalised Mycobacterium haemophilum infection after an increase in immunosuppressive therapy and treatment with a tumour necrosis factor-α (TNF-α) inhibitor. Infection involved skin and soft tissue, joints and bones, as well as the renal transplant with an interstitial nephritis. Rapid diagnosis using PCR and DNA sequencing allowed early appropriate treatment. Triple antibiotic therapy and reduction in immunosuppression resulted in a slow but sustained recovery. Immunosuppression causes severe opportunistic infections. TNF-α inhibitors are very effective and well tolerated but have an increased susceptibility to infections with mycobacteria. Mycobacterial infections represent a significant clinical risk to transplant recipients because of their aggressive clinical course and the need for complex toxic antibiotic treatments. In these patients, M. haemophilum is a cause of skin infections.

CC Chemokine Ligand 18 in ANCA-Associated Crescentic GN.

ANCA-associated vasculitis is the most frequent cause of crescentic GN. To define new molecular and/or cellular biomarkers of this disease in the kidney, we performed microarray analyses of renal biopsy samples from patients with ANCA-associated crescentic GN. Expression profiles were correlated with clinical data in a prospective study of patients with renal ANCA disease. CC chemokine ligand 18 (CCL18), acting through CC chemokine receptor 8 (CCR8) on mononuclear cells, was identified as the most upregulated chemotactic cytokine in patients with newly diagnosed ANCA-associated crescentic GN. Macrophages and myeloid dendritic cells in the kidney were detected as CCL18-producing cells. The density of CCL18(+) cells correlated with crescent formation, interstitial inflammation, and impairment of renal function. CCL18 protein levels were higher in sera of patients with renal ANCA disease compared with those in sera of patients with other forms of crescentic GN. CCL18 serum levels were higher in patients who suffered from ANCA-associated renal relapses compared with those in patients who remained in remission. Using a murine model of crescentic GN, we explored the effects of the CCL18 murine functional analog CCL8 and its receptor CCR8 on kidney function and morphology. Compared with wild-type mice, Ccr8(-/-) mice had significantly less infiltration of pathogenic mononuclear phagocytes. Furthermore, Ccr8(-/-) mice maintained renal function better and had reduced renal tissue injury. In summary, our data indicate that CCL18 drives renal inflammation through CCR8-expressing cells and could serve as a biomarker for disease activity and renal relapse in ANCA-associated crescentic GN.

CXCL5 drives neutrophil recruitment in TH17-mediated GN.

Neutrophil trafficking to sites of inflammation is essential for the defense against bacterial and fungal infections, but also contributes to tissue damage in TH17-mediated autoimmunity. This process is regulated by chemokines, which often show an overlapping expression pattern and function in pathogen- and autoimmune-induced inflammatory reactions. Using a murine model of crescentic GN, we show that the pathogenic TH17/IL-17 immune response induces chemokine (C-X-C motif) ligand 5 (CXCL5) expression in kidney tubular cells, which recruits destructive neutrophils that contribute to renal tissue injury. By contrast, CXCL5 was dispensable for neutrophil recruitment and effective bacterial clearance in a murine model of acute bacterial pyelonephritis. In line with these findings, CXCL5 expression was highly upregulated in the kidneys of patients with ANCA-associated crescentic GN as opposed to patients with acute bacterial pyelonephritis. Our data therefore identify CXCL5 as a potential therapeutic target for the restriction of pathogenic neutrophil infiltration in TH17-mediated autoimmune diseases while leaving intact the neutrophil function in protective immunity against invading pathogens.

Stat3 programs Th17-specific regulatory T cells to control GN.

A pathogenic role for Th17 cells in inflammatory renal disease is well established. The mechanisms underlying their counter-regulation are, however, largely unknown. Recently, Th17 lineage-specific regulatory T cells (Treg17) that depend on activation of the transcription factor Stat3 were identified. We studied the function of Treg17 in the nephrotoxic nephritis (NTN) model of crescentic GN. The absence of Treg17 cells in Foxp3(Cre)×Stat3(fl/fl) mice resulted in the aggravation of NTN and skewing of renal and systemic immune responses toward Th17. Detailed analysis of Stat3-deficient Tregs revealed that the survival, activation, proliferation, and suppressive function of these cells remained intact. However, Tregs from Foxp3(Cre)×Stat3(fl/fl) mice lacked surface expression of the chemokine receptor CCR6, which resulted in impaired renal trafficking. Furthermore, aggravation of NTN was reversible in the absence of Th17 responses, as shown in CD4(Cre)×Stat3(fl/fl) mice lacking both Treg17 and Th17 cells, suggesting that Th17 cells are indeed the major target of Treg17 cells. Notably, immunohistochemistry revealed CCR6-bearing Treg17 cells in kidney biopsy specimens of patients with GN. CCR6 expression on human Treg17 cells also appears dependent on STAT3, as shown by analysis of Tregs from patients with dominant-negative STAT3 mutations. Our data indicate the presence and involvement of Stat3/STAT3-dependent Treg17 cells that specifically target Th17 cells in murine and human crescentic GN, and suggest the kidney-specific action of these Treg17 cells is regulated by CCR6-directed migration into areas of Th17 inflammation.