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Papers by Christoph Licht

A 4-month-old male infant was diagnosed with nephrogenic diabetes insipidus (NDI). Genetic testin... more A 4-month-old male infant was diagnosed with nephrogenic diabetes insipidus (NDI). Genetic testing of the arginine vasopressin receptor-2 (AVPR2) yielded a novel X-linked mutation, termed Q96H, in both the propositus and his mother; there was no family history. Protein sequence comparison between AVPR subtypes shows that Q96 is part of a highly conserved motif. Many other disease-causing mutations , confirmed with in vitro expression studies, map to surrounding residues. Molecular modelling studies showed that the equivalent residue in AVPR1 is likely critical for vasopressin binding. We posit that Q96 must be important for the integrity of AVPR2 function.

Canadian Journal of Kidney Health and Disease, 2021

Purpose of review: Thrombotic microangiopathy (TMA) is suspected in patients presenting with thro... more Purpose of review: Thrombotic microangiopathy (TMA) is suspected in patients presenting with thrombocytopenia and evidence of a microangiopathic hemolytic anemia. Patients with TMA can be critically ill, so rapid and accurate identification of the underlying etiology is essential. Due to better insights into pathophysiology and causes of TMA, we can now categorize TMAs as thrombotic thrombocytopenic purpura, postinfectious (mainly Shiga toxin-producing Escherichia coli–induced) hemolytic uremic syndrome (HUS), TMA associated with a coexisting condition, or atypical HUS (aHUS). We recognized an unmet need in the medical community to guide the timely and accurate identification of TMA, the selection of tests to clarify its etiology, and the sequence of steps to initiate treatment. Sources of information: Key published studies relevant to the identification, classification, and treatment of TMAs in children or adults. These studies were obtained through literature searches conducted wi...

Pediatric Nephrology, 2017

Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The dis... more Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The disease spectrum of TMA includes, amongst others, thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS). TTP is caused by defective cleavage of von Willebrand factor (VWF), whereas aHUS is caused by overshooting complement activation and subsequent endothelial cell (EC) injury. Despite their distinct pathophysiology, the clinical manifestation of TTP and aHUS consisting of microangiopathic haemolytic anaemia and thrombocytopenia is often similar and difficult to distinguish. Recent evidence hints at both a genetic and functional link between TTP and aHUS, especially between VWF and the complement system. There is novel in vitro evidence that complement activation not only results in VWF release from ECs, but that VWF also functions as a negative complement regulator, thus protecting the EC surface from ongoing complement attack. Although contrary to previous experimental work suggesting that complement can be activated on VWF multimers, there may be an explanation in vivo that rationalizes these apparently contradictory findings, whereby a system primarily meant to regulate becomes overwhelmed or pathologic in the disease state. The importance of unravelling these recent findings for our understanding of TMA pathology becomes even more evident considering that glomerular ECs express VWF in a heterogeneous pattern with an overall decreased expression level, thus potentially leaving the glomerular ECs vulnerable to complement-mediated injury. Taken together, these findings support the concept that TTP and aHUS represent two extreme ends of a TMA disease spectrum rather than isolated disease entities.

Pediatric nephrology (Berlin, Germany), Jan 17, 2017

This is a report of an infant born near term with neonatal stroke and haematuria. Changes were no... more This is a report of an infant born near term with neonatal stroke and haematuria. Changes were noted on foetal magnetic resonance images, and these persisted postnatally. A routine renal ultrasound scan during follow-up detected haematuria with no associated proteinuria. A likely pathogenic genetic mutation was identified. This case highlights a relatively newly discovered cause for hereditary nephropathy affecting the basement membrane, initially affecting the glomerular but later the renal tubular basement membranes. The renal phenotype, pathogenic genotype and pathological findings on renal biopsy are discussed.

Pediatric nephrology (Berlin, Germany), Jan 17, 2017

This is a report of an infant born near term with neonatal stroke and haematuria. The renal pheno... more This is a report of an infant born near term with neonatal stroke and haematuria. The renal phenotype, pathogenic genotype and pathological findings on renal biopsy are discussed. Prenatal magnetic resonance imaging revealed anomalies which persisted postnatally. Haematuria was detected during follow-up. The posttnatal renal ultrasound scan was normal, and there was no associated proteinuria. A likely pathogenic genetic mutation was detected. This case highlights a relatively newly discovered cause of hereditary nephropathy in which the basement membrane is affected, with initial effects on the glomerular membranes and subsequent effects on the renal tubular basement membranes.

Pediatric nephrology (Berlin, Germany), Jan 8, 2017

No controlled trials in children with end-stage kidney disease have assessed the benefits of more... more No controlled trials in children with end-stage kidney disease have assessed the benefits of more frequently administered hemodialysis (HD). We conducted a multicenter, crossover pilot trial to determine if short, more frequent (5 days per week) in-center HD was feasible and associated with improvements in blood pressure compared with three conventional HD treatments per week. Because adult studies have not controlled for the weekly duration of dialysis, we fixed the total treatment time at 12 h a week of dialysis during two 3-month study periods; only frequency varied from 5 to 3 days per week between study periods. Eight children (median age 16.7 years) consented at three children's hospitals. The prespecified primary composite outcome was a sustained 10% decrease in systolic blood pressure and/or a decrease in antihypertensive medications relative to each study period's baseline. Among the six patients completing both study periods, five (83.3%) experienced the primary ou...

Orphanet journal of rare diseases, Nov 21, 2016

Patients are becoming increasingly involved in research which can promote innovation through nove... more Patients are becoming increasingly involved in research which can promote innovation through novel ideas, support patient-centred actions, and facilitate drug development. For rare diseases, registries that collect data from patients can increase knowledge of the disease's natural history, evaluate clinical therapies, monitor drug safety, and measure quality of care. The active participation of patients is expected to optimise rare-disease management and improve patient outcomes. However, few reports address the type and frequency of interactions involving patients, and what research input patient groups have. Here, we describe a collaboration between an international group of patient organisations advocating for patients with atypical haemolytic uraemic syndrome (aHUS), the aHUS Alliance, and an international aHUS patient registry (ClinicalTrials.gov NCT01522183). The aHUS Registry Scientific Advisory Board (SAB) invited the aHUS Alliance to submit research ideas important to p...

Pediatric Nephrology, 2016

Recent advances in our understanding of the disease pathology of membranoproliferative glomerulon... more Recent advances in our understanding of the disease pathology of membranoproliferative glomerulonephritis has resulted in its re-classification as complement C3 glomerulopathy (C3G) and immune complex-mediated glomerulonephritis (IC-GN). The new consensus is based on its underlying pathomechanism, with a key pathogenetic role for the complement alternative pathway (AP), rather than on histomorphological characteristics. In C3G, loss of AP regulation leads to predominant glomerular C3 deposition, which distinguishes C3G from IC-GN with predominant immunoglobulin G staining. Electron microscopy further subdivides C3G into C3 glomerulonephritis and dense deposit disease depending on the presence and distribution pattern of electron-dense deposits within the glomerular filter. Mutations or autoantibodies affecting the function of AP activators or regulators, in particular the decay of the C3 convertase (C3 nephritic factor), have been detected in up to 80 % of C3G patients. The natural outcome of C3G is heterogeneous, but 50 % of patients progress slowly and reach end-stage renal disease within 10-15 years. The new classification not only marks significant advancement in the pathogenic understanding of this rare disease, but also opens doors towards more specific treatment with the potential for improved outcomes.

Frontiers in Immunology, 2016

Neutrophils deposit antimicrobial proteins, such as myeloperoxidase and proteases on chromatin, w... more Neutrophils deposit antimicrobial proteins, such as myeloperoxidase and proteases on chromatin, which they release as neutrophil extracellular traps (NETs). Neutrophils also carry key components of the complement alternative pathway (AP) such as properdin or complement factor P (CFP), complement factor B (CFB), and C3. However, the contribution of these complement components and complement activation during NET formation in the presence and absence of bacteria is poorly understood. We studied complement activation on NETs and a Gram-negative opportunistic bacterial pathogen Pseudomonas aeruginosa (PA01, PAKwt, and PAKgfp). Here, we show that anaphylatoxin C5a, formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol myristate acetate (PMA), which activates NADPH oxidase, induce the release of CFP, CFB, and C3 from neutrophils. In response to PMA or P. aeruginosa, neutrophils secrete CFP, deposit it on NETs and bacteria, and induce the formation of terminal complement complexes (C5b-9). A blocking anti-CFP antibody inhibited AP-mediated but not non-AP-mediated complement activation on NETs and P. aeruginosa. Therefore, NET-mediated complement activation occurs via both AP-and non AP-based mechanisms, and AP-mediated complement activation during NETosis is dependent on CFP. These findings suggest that neutrophils could use their "AP tool kit" to readily activate complement on NETs and Gram-negative bacteria, such as P. aeruginosa, whereas additional components present in the serum help to fix non-AP-mediated complement both on NETs and bacteria. This unique mechanism may play important roles in host defense and help to explain specific roles of complement activation in NET-related diseases.

Pediatric Nephrology, 2016

Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have ... more Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have an atypical, severe presentation, and these exceptional cases have been linked to the dysregulation of the complement alternative pathway (CAP). There is a considerable overlap in the histopathological features of PIGN and C3 glomerulopathy (C3G), which is also associated with CAP dysregulation but has a poorer outcome. We hypothesized that PIGN and C3G define a disease spectrum, and that in the past there may be some children with C3G who were misclassified with PIGN before C3G was described as a separate disease entity. Children with PIGN (n = 33) diagnosed between 1985 and 2010 who underwent a renal biopsy due to their unusual course were reviewed and of them, 8 were reclassified into C3G based on the current classification criteria. Outcome was based on the degree of proteinuria, C3 level, and renal function at follow-up. Sixteen (72.7%) children with typical PIGN recovered completely as compared to only 2 (25%) with C3G. Of note, children with "typical" PIGN had a more severe disease course at onset; however, the outcome at last follow up was favorable. Our results support the hypothesis that PIGN and C3G form a disease spectrum and have different long-term clinical implications and management strategies.

Nature communications, Jan 24, 2016

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we s... more Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linki...

Kidney International, 2016

A typical hemolytic uremic syndrome (aHUS) is a progressive life-threatening thrombotic microangi... more A typical hemolytic uremic syndrome (aHUS) is a progressive life-threatening thrombotic microangiopathy (TMA) associated with dysregulation of the complement alternative pathway. 1-3 Complement gene mutations (e.g., complement factor H [CFH], membrane cofactor protein [MCP], complement factor I [CFI], complement factor B [CFB], complement protein 3 [C3]), or factor H autoantibodies are identified in 50% to 60% of patients with aHUS. 4-6 Abnormalities in genes encoding thrombomodulin, plasminogen, and diacylglycerol kinase ε (DGKE) 7-9 occur in a small number of patients. Evidence of a genetic abnormality is not required for diagnosis. 4,10-13 Although onset may occur at any age, 40% of patients develop aHUS by 18 years of age. 1,2,5 Clinical manifestations in children generally include anemia, thrombocytopenia, and acute kidney injury, 5 but peripheral gangrene, 14 arterial stenoses, 15 dilated cardiomyopathy, cardiorespiratory arrest, 16 and neurologic, 5,17 pulmonary, 11 and gastrointestinal complications 17 have been reported. Historically, aHUS was managed with plasma exchange/plasma infusion (PE/PI) and was associated with high morbidity and mortality rates, 1-3,5,18 with children having higher mortality than adults. 5 PE/PI may induce stabilization of hematologic parameters (but generally not significant renal function improvement), 19 is associated with complications, and impairs quality of life. 19,20 The availability of eculizumab (Soliris, Alexion Pharmaceuticals, Inc., Cheshire, CT, USA) 21,22an anti-C5 monoclonal antibody and the first and only currently approved therapy for adult and pediatric patients-has profoundly changed aHUS management. 13,23 The efficacy and safety of

Pediatric Nephrology, 2015

Christoph Licht*, Magdalena Riedl, Matthew C. Pickering and Michael Braun Division of Nephrology,... more Christoph Licht*, Magdalena Riedl, Matthew C. Pickering and Michael Braun Division of Nephrology, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada Research Institute, Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada Department of Paediatrics, University of Toronto, Toronto, ON, Canada Department of Paediatrics, Innsbruck Medical University, Innsbruck, Tyrol, Austria Centre for Complement and Inflammation Research, Imperial College, London, UK Renal Section, Department of Pediatrics, Texas Children’s Hospital, Balyor College of Medicine, Houston, TX, USA

Pediatric Nephrology, 2015

Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of ... more Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of complement dysregulation. This advance facilitated the development of novel, rational treatment options targeting terminal complement activation, e.g., using an anti-C5 antibody (eculizumab). We review treatment and patient management issues related to this therapeutic approach. We present consensus clinical practice recommendations generated by HUS International, an international expert group of clinicians and basic scientists with a focused interest in HUS. We aim to address the following questions of high relevance to daily clinical practice: Which complement investigations should be done and when? What is the importance of anti-factor H antibody detection? Who should be treated with eculizumab? Is plasma exchange therapy still needed? When should eculizumab therapy be initiated? How and when should complement blockade be monitored? Can the approved treatment schedule be modified? What approach should be taken to kidney and/or combined liver-kidney transplantation? How should we limit the risk of meningococcal infection under

Seminars in Thrombosis and Hemostasis, 2014

Thrombotic microangiopathy (TMA) is a rare but severe disorder characterized by endothelial cell ... more Thrombotic microangiopathy (TMA) is a rare but severe disorder characterized by endothelial cell activation and thrombus formation. It manifests with the triad of hemolytic anemia, thrombocytopenia, and organ failure. Prompt diagnosis and treatment initiation are crucial for long-term outcome. TMA often manifests subsequent to infectious events, of which (enterohemorrhagic) Escherichia coli is the most frequently reported. TMA also occurs on the background of genetic/autoimmune defects in the complement system (atypical hemolytic uremic syndrome [aHUS]) and underlying conditions, such as pregnancy, transplantation, drugs, other glomerulopathies, vasculitides, or metabolic defects. Complement activation or defects in its regulation have now been described in an increasing number of acquired diseases with TMA. Coinciding with this expanding spectrum of complement-mediated diseases, the question arises which patients might benefit from a complement-targeted therapy. Success of therapy depends on the individual contribution of complement activation in disease pathogenesis. The advent of eculizumab, a monoclonal antibody that blocks terminal complement activation, has markedly improved outcome and quality of life in patients with aHUS. This review discusses the contribution of complement and highlights its complex interaction with inflammation, coagulation, and the endothelium. Treatment experiences focusing on eculizumab therapy are discussed in detail across the emerging spectrum of complement-mediated thrombotic microangiopathies.

Pediatric Nephrology, 2010

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective ... more Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective complement regulation in over 50% of cases. Mutations have been identified in genes encoding both complement regulators [complement factor H (CFH), complement factor I (CFI), complement factor H-related proteins (CFHR), and membrane cofactor protein (MCP)], as well as complement activators [complement factor B (CFB) and C3]. More recently, mutations have also been identified in thrombomodulin (THBD), an anticoagulant glycoprotein that plays a role in the inactivation of C3a and C5a. Inhibitory autoantibodies to CFH account for an additional 5-10% of cases and can occur in isolation or in association with mutations in CFH, CFI, CFHR 1, 3, 4, and MCP. Plasma therapies are considered the mainstay of therapy in aHUS secondary to defective complement regulation and may be administered as plasma infusions or plasma exchange. However, in certain cases, despite initiation of plasma therapy, renal function continues to deteriorate with progression to end-stage renal disease and renal transplantation. Recently, eculizumab, a humanized monoclonal antibody against C5, has been described as an effective therapeutic strategy in the management of refractory aHUS that has failed to respond to plasma therapy. Clinical trials are now underway to further evaluate the efficacy of eculizumab in the management of both plasma-sensitive and plasma-resistant aHUS.

Pediatric Nephrology, 2013

Practice variation is common for nephrotic syndrome (NS) treatment. A cross-sectional, web-based ... more Practice variation is common for nephrotic syndrome (NS) treatment. A cross-sectional, web-based survey on NS treatment was administered to 58 Canadian pediatric nephrologists with the aim to document existing practice variation and compare practice with the recommendations of the Kidney Disease Improving Global Outcomes Clinical Practice Guideline for NS. Of the 58 nephrologists asked to participate in the survey, 40 (69 %) responded. Among these, 62 % prescribed initial daily glucocorticoid (GC) therapy for 6 weeks, 26 % for 4 weeks by 26 %, and 10 % prescribed 'other'. Alternate-day GC was continued for 6 weeks by 63 % of respondents and for >6 and <6 weeks by 32 and 6 %, respectively. For biopsy-confirmed minimal change disease, 65 and 46 % of respondents chose oral cyclophosphamide for frequently relapsing and steroid-dependent phenotypes, respectively; calcineurin inhibitors or mycophenolate were the second most popular choices. Kidney biopsy was 'always' performed by 16, 39, and 97 % of respondents for frequently relapsing, steroid-dependent, and steroid-resistant patients, respectively. Rituximab had been administered by 60 % of respondents; 22, 56, and 72 % reported that they would consider rituximab for frequently relapsing, steroid-dependent, and steroid-resistant patients, respectively. Most notable differences between practice and Guideline recommendations were first presentation GC duration, GC-sparing agent choices in frequently relapsing and steroid-dependent patients, and biopsy practices. There is substantial Canadian…

A 4-month-old male infant was diagnosed with nephrogenic diabetes insipidus (NDI). Genetic testin... more A 4-month-old male infant was diagnosed with nephrogenic diabetes insipidus (NDI). Genetic testing of the arginine vasopressin receptor-2 (AVPR2) yielded a novel X-linked mutation, termed Q96H, in both the propositus and his mother; there was no family history. Protein sequence comparison between AVPR subtypes shows that Q96 is part of a highly conserved motif. Many other disease-causing mutations , confirmed with in vitro expression studies, map to surrounding residues. Molecular modelling studies showed that the equivalent residue in AVPR1 is likely critical for vasopressin binding. We posit that Q96 must be important for the integrity of AVPR2 function.

Canadian Journal of Kidney Health and Disease, 2021

Purpose of review: Thrombotic microangiopathy (TMA) is suspected in patients presenting with thro... more Purpose of review: Thrombotic microangiopathy (TMA) is suspected in patients presenting with thrombocytopenia and evidence of a microangiopathic hemolytic anemia. Patients with TMA can be critically ill, so rapid and accurate identification of the underlying etiology is essential. Due to better insights into pathophysiology and causes of TMA, we can now categorize TMAs as thrombotic thrombocytopenic purpura, postinfectious (mainly Shiga toxin-producing Escherichia coli–induced) hemolytic uremic syndrome (HUS), TMA associated with a coexisting condition, or atypical HUS (aHUS). We recognized an unmet need in the medical community to guide the timely and accurate identification of TMA, the selection of tests to clarify its etiology, and the sequence of steps to initiate treatment. Sources of information: Key published studies relevant to the identification, classification, and treatment of TMAs in children or adults. These studies were obtained through literature searches conducted wi...

Pediatric Nephrology, 2017

Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The dis... more Thrombotic microangiopathy (TMA) is caused by thrombus formation in the microvasculature. The disease spectrum of TMA includes, amongst others, thrombotic thrombocytopenic purpura (TTP) and atypical haemolytic uraemic syndrome (aHUS). TTP is caused by defective cleavage of von Willebrand factor (VWF), whereas aHUS is caused by overshooting complement activation and subsequent endothelial cell (EC) injury. Despite their distinct pathophysiology, the clinical manifestation of TTP and aHUS consisting of microangiopathic haemolytic anaemia and thrombocytopenia is often similar and difficult to distinguish. Recent evidence hints at both a genetic and functional link between TTP and aHUS, especially between VWF and the complement system. There is novel in vitro evidence that complement activation not only results in VWF release from ECs, but that VWF also functions as a negative complement regulator, thus protecting the EC surface from ongoing complement attack. Although contrary to previous experimental work suggesting that complement can be activated on VWF multimers, there may be an explanation in vivo that rationalizes these apparently contradictory findings, whereby a system primarily meant to regulate becomes overwhelmed or pathologic in the disease state. The importance of unravelling these recent findings for our understanding of TMA pathology becomes even more evident considering that glomerular ECs express VWF in a heterogeneous pattern with an overall decreased expression level, thus potentially leaving the glomerular ECs vulnerable to complement-mediated injury. Taken together, these findings support the concept that TTP and aHUS represent two extreme ends of a TMA disease spectrum rather than isolated disease entities.

Pediatric nephrology (Berlin, Germany), Jan 17, 2017

This is a report of an infant born near term with neonatal stroke and haematuria. Changes were no... more This is a report of an infant born near term with neonatal stroke and haematuria. Changes were noted on foetal magnetic resonance images, and these persisted postnatally. A routine renal ultrasound scan during follow-up detected haematuria with no associated proteinuria. A likely pathogenic genetic mutation was identified. This case highlights a relatively newly discovered cause for hereditary nephropathy affecting the basement membrane, initially affecting the glomerular but later the renal tubular basement membranes. The renal phenotype, pathogenic genotype and pathological findings on renal biopsy are discussed.

Pediatric nephrology (Berlin, Germany), Jan 17, 2017

This is a report of an infant born near term with neonatal stroke and haematuria. The renal pheno... more This is a report of an infant born near term with neonatal stroke and haematuria. The renal phenotype, pathogenic genotype and pathological findings on renal biopsy are discussed. Prenatal magnetic resonance imaging revealed anomalies which persisted postnatally. Haematuria was detected during follow-up. The posttnatal renal ultrasound scan was normal, and there was no associated proteinuria. A likely pathogenic genetic mutation was detected. This case highlights a relatively newly discovered cause of hereditary nephropathy in which the basement membrane is affected, with initial effects on the glomerular membranes and subsequent effects on the renal tubular basement membranes.

Pediatric nephrology (Berlin, Germany), Jan 8, 2017

No controlled trials in children with end-stage kidney disease have assessed the benefits of more... more No controlled trials in children with end-stage kidney disease have assessed the benefits of more frequently administered hemodialysis (HD). We conducted a multicenter, crossover pilot trial to determine if short, more frequent (5 days per week) in-center HD was feasible and associated with improvements in blood pressure compared with three conventional HD treatments per week. Because adult studies have not controlled for the weekly duration of dialysis, we fixed the total treatment time at 12 h a week of dialysis during two 3-month study periods; only frequency varied from 5 to 3 days per week between study periods. Eight children (median age 16.7 years) consented at three children's hospitals. The prespecified primary composite outcome was a sustained 10% decrease in systolic blood pressure and/or a decrease in antihypertensive medications relative to each study period's baseline. Among the six patients completing both study periods, five (83.3%) experienced the primary ou...

Orphanet journal of rare diseases, Nov 21, 2016

Patients are becoming increasingly involved in research which can promote innovation through nove... more Patients are becoming increasingly involved in research which can promote innovation through novel ideas, support patient-centred actions, and facilitate drug development. For rare diseases, registries that collect data from patients can increase knowledge of the disease's natural history, evaluate clinical therapies, monitor drug safety, and measure quality of care. The active participation of patients is expected to optimise rare-disease management and improve patient outcomes. However, few reports address the type and frequency of interactions involving patients, and what research input patient groups have. Here, we describe a collaboration between an international group of patient organisations advocating for patients with atypical haemolytic uraemic syndrome (aHUS), the aHUS Alliance, and an international aHUS patient registry (ClinicalTrials.gov NCT01522183). The aHUS Registry Scientific Advisory Board (SAB) invited the aHUS Alliance to submit research ideas important to p...

Pediatric Nephrology, 2016

Recent advances in our understanding of the disease pathology of membranoproliferative glomerulon... more Recent advances in our understanding of the disease pathology of membranoproliferative glomerulonephritis has resulted in its re-classification as complement C3 glomerulopathy (C3G) and immune complex-mediated glomerulonephritis (IC-GN). The new consensus is based on its underlying pathomechanism, with a key pathogenetic role for the complement alternative pathway (AP), rather than on histomorphological characteristics. In C3G, loss of AP regulation leads to predominant glomerular C3 deposition, which distinguishes C3G from IC-GN with predominant immunoglobulin G staining. Electron microscopy further subdivides C3G into C3 glomerulonephritis and dense deposit disease depending on the presence and distribution pattern of electron-dense deposits within the glomerular filter. Mutations or autoantibodies affecting the function of AP activators or regulators, in particular the decay of the C3 convertase (C3 nephritic factor), have been detected in up to 80 % of C3G patients. The natural outcome of C3G is heterogeneous, but 50 % of patients progress slowly and reach end-stage renal disease within 10-15 years. The new classification not only marks significant advancement in the pathogenic understanding of this rare disease, but also opens doors towards more specific treatment with the potential for improved outcomes.

Frontiers in Immunology, 2016

Neutrophils deposit antimicrobial proteins, such as myeloperoxidase and proteases on chromatin, w... more Neutrophils deposit antimicrobial proteins, such as myeloperoxidase and proteases on chromatin, which they release as neutrophil extracellular traps (NETs). Neutrophils also carry key components of the complement alternative pathway (AP) such as properdin or complement factor P (CFP), complement factor B (CFB), and C3. However, the contribution of these complement components and complement activation during NET formation in the presence and absence of bacteria is poorly understood. We studied complement activation on NETs and a Gram-negative opportunistic bacterial pathogen Pseudomonas aeruginosa (PA01, PAKwt, and PAKgfp). Here, we show that anaphylatoxin C5a, formyl-methionyl-leucyl-phenylalanine (fMLP) and phorbol myristate acetate (PMA), which activates NADPH oxidase, induce the release of CFP, CFB, and C3 from neutrophils. In response to PMA or P. aeruginosa, neutrophils secrete CFP, deposit it on NETs and bacteria, and induce the formation of terminal complement complexes (C5b-9). A blocking anti-CFP antibody inhibited AP-mediated but not non-AP-mediated complement activation on NETs and P. aeruginosa. Therefore, NET-mediated complement activation occurs via both AP-and non AP-based mechanisms, and AP-mediated complement activation during NETosis is dependent on CFP. These findings suggest that neutrophils could use their "AP tool kit" to readily activate complement on NETs and Gram-negative bacteria, such as P. aeruginosa, whereas additional components present in the serum help to fix non-AP-mediated complement both on NETs and bacteria. This unique mechanism may play important roles in host defense and help to explain specific roles of complement activation in NET-related diseases.

Pediatric Nephrology, 2016

Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have ... more Post-infectious glomerulonephritis (PIGN) usually follows a benign course, but few children have an atypical, severe presentation, and these exceptional cases have been linked to the dysregulation of the complement alternative pathway (CAP). There is a considerable overlap in the histopathological features of PIGN and C3 glomerulopathy (C3G), which is also associated with CAP dysregulation but has a poorer outcome. We hypothesized that PIGN and C3G define a disease spectrum, and that in the past there may be some children with C3G who were misclassified with PIGN before C3G was described as a separate disease entity. Children with PIGN (n = 33) diagnosed between 1985 and 2010 who underwent a renal biopsy due to their unusual course were reviewed and of them, 8 were reclassified into C3G based on the current classification criteria. Outcome was based on the degree of proteinuria, C3 level, and renal function at follow-up. Sixteen (72.7%) children with typical PIGN recovered completely as compared to only 2 (25%) with C3G. Of note, children with "typical" PIGN had a more severe disease course at onset; however, the outcome at last follow up was favorable. Our results support the hypothesis that PIGN and C3G form a disease spectrum and have different long-term clinical implications and management strategies.

Nature communications, Jan 24, 2016

Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we s... more Steroid-resistant nephrotic syndrome (SRNS) causes 15% of chronic kidney disease (CKD). Here we show that recessive mutations in FAT1 cause a distinct renal disease entity in four families with a combination of SRNS, tubular ectasia, haematuria and facultative neurological involvement. Loss of FAT1 results in decreased cell adhesion and migration in fibroblasts and podocytes and the decreased migration is partially reversed by a RAC1/CDC42 activator. Podocyte-specific deletion of Fat1 in mice induces abnormal glomerular filtration barrier development, leading to podocyte foot process effacement. Knockdown of Fat1 in renal tubular cells reduces migration, decreases active RAC1 and CDC42, and induces defects in lumen formation. Knockdown of fat1 in zebrafish causes pronephric cysts, which is partially rescued by RAC1/CDC42 activators, confirming a role of the two small GTPases in the pathogenesis. These findings provide new insights into the pathogenesis of SRNS and tubulopathy, linki...

Kidney International, 2016

A typical hemolytic uremic syndrome (aHUS) is a progressive life-threatening thrombotic microangi... more A typical hemolytic uremic syndrome (aHUS) is a progressive life-threatening thrombotic microangiopathy (TMA) associated with dysregulation of the complement alternative pathway. 1-3 Complement gene mutations (e.g., complement factor H [CFH], membrane cofactor protein [MCP], complement factor I [CFI], complement factor B [CFB], complement protein 3 [C3]), or factor H autoantibodies are identified in 50% to 60% of patients with aHUS. 4-6 Abnormalities in genes encoding thrombomodulin, plasminogen, and diacylglycerol kinase ε (DGKE) 7-9 occur in a small number of patients. Evidence of a genetic abnormality is not required for diagnosis. 4,10-13 Although onset may occur at any age, 40% of patients develop aHUS by 18 years of age. 1,2,5 Clinical manifestations in children generally include anemia, thrombocytopenia, and acute kidney injury, 5 but peripheral gangrene, 14 arterial stenoses, 15 dilated cardiomyopathy, cardiorespiratory arrest, 16 and neurologic, 5,17 pulmonary, 11 and gastrointestinal complications 17 have been reported. Historically, aHUS was managed with plasma exchange/plasma infusion (PE/PI) and was associated with high morbidity and mortality rates, 1-3,5,18 with children having higher mortality than adults. 5 PE/PI may induce stabilization of hematologic parameters (but generally not significant renal function improvement), 19 is associated with complications, and impairs quality of life. 19,20 The availability of eculizumab (Soliris, Alexion Pharmaceuticals, Inc., Cheshire, CT, USA) 21,22an anti-C5 monoclonal antibody and the first and only currently approved therapy for adult and pediatric patients-has profoundly changed aHUS management. 13,23 The efficacy and safety of

Pediatric Nephrology, 2015

Christoph Licht*, Magdalena Riedl, Matthew C. Pickering and Michael Braun Division of Nephrology,... more Christoph Licht*, Magdalena Riedl, Matthew C. Pickering and Michael Braun Division of Nephrology, The Hospital for Sick Children, University of Toronto, Toronto, ON, Canada Research Institute, Cell Biology Program, The Hospital for Sick Children, Toronto, ON, Canada Department of Paediatrics, University of Toronto, Toronto, ON, Canada Department of Paediatrics, Innsbruck Medical University, Innsbruck, Tyrol, Austria Centre for Complement and Inflammation Research, Imperial College, London, UK Renal Section, Department of Pediatrics, Texas Children’s Hospital, Balyor College of Medicine, Houston, TX, USA

Pediatric Nephrology, 2015

Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of ... more Atypical hemolytic uremic syndrome (aHUS) emerged during the last decade as a disease largely of complement dysregulation. This advance facilitated the development of novel, rational treatment options targeting terminal complement activation, e.g., using an anti-C5 antibody (eculizumab). We review treatment and patient management issues related to this therapeutic approach. We present consensus clinical practice recommendations generated by HUS International, an international expert group of clinicians and basic scientists with a focused interest in HUS. We aim to address the following questions of high relevance to daily clinical practice: Which complement investigations should be done and when? What is the importance of anti-factor H antibody detection? Who should be treated with eculizumab? Is plasma exchange therapy still needed? When should eculizumab therapy be initiated? How and when should complement blockade be monitored? Can the approved treatment schedule be modified? What approach should be taken to kidney and/or combined liver-kidney transplantation? How should we limit the risk of meningococcal infection under

Seminars in Thrombosis and Hemostasis, 2014

Thrombotic microangiopathy (TMA) is a rare but severe disorder characterized by endothelial cell ... more Thrombotic microangiopathy (TMA) is a rare but severe disorder characterized by endothelial cell activation and thrombus formation. It manifests with the triad of hemolytic anemia, thrombocytopenia, and organ failure. Prompt diagnosis and treatment initiation are crucial for long-term outcome. TMA often manifests subsequent to infectious events, of which (enterohemorrhagic) Escherichia coli is the most frequently reported. TMA also occurs on the background of genetic/autoimmune defects in the complement system (atypical hemolytic uremic syndrome [aHUS]) and underlying conditions, such as pregnancy, transplantation, drugs, other glomerulopathies, vasculitides, or metabolic defects. Complement activation or defects in its regulation have now been described in an increasing number of acquired diseases with TMA. Coinciding with this expanding spectrum of complement-mediated diseases, the question arises which patients might benefit from a complement-targeted therapy. Success of therapy depends on the individual contribution of complement activation in disease pathogenesis. The advent of eculizumab, a monoclonal antibody that blocks terminal complement activation, has markedly improved outcome and quality of life in patients with aHUS. This review discusses the contribution of complement and highlights its complex interaction with inflammation, coagulation, and the endothelium. Treatment experiences focusing on eculizumab therapy are discussed in detail across the emerging spectrum of complement-mediated thrombotic microangiopathies.

Pediatric Nephrology, 2010

Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective ... more Atypical hemolytic uremic syndrome (aHUS) is a heterogeneous disease that is caused by defective complement regulation in over 50% of cases. Mutations have been identified in genes encoding both complement regulators [complement factor H (CFH), complement factor I (CFI), complement factor H-related proteins (CFHR), and membrane cofactor protein (MCP)], as well as complement activators [complement factor B (CFB) and C3]. More recently, mutations have also been identified in thrombomodulin (THBD), an anticoagulant glycoprotein that plays a role in the inactivation of C3a and C5a. Inhibitory autoantibodies to CFH account for an additional 5-10% of cases and can occur in isolation or in association with mutations in CFH, CFI, CFHR 1, 3, 4, and MCP. Plasma therapies are considered the mainstay of therapy in aHUS secondary to defective complement regulation and may be administered as plasma infusions or plasma exchange. However, in certain cases, despite initiation of plasma therapy, renal function continues to deteriorate with progression to end-stage renal disease and renal transplantation. Recently, eculizumab, a humanized monoclonal antibody against C5, has been described as an effective therapeutic strategy in the management of refractory aHUS that has failed to respond to plasma therapy. Clinical trials are now underway to further evaluate the efficacy of eculizumab in the management of both plasma-sensitive and plasma-resistant aHUS.

Pediatric Nephrology, 2013

Practice variation is common for nephrotic syndrome (NS) treatment. A cross-sectional, web-based ... more Practice variation is common for nephrotic syndrome (NS) treatment. A cross-sectional, web-based survey on NS treatment was administered to 58 Canadian pediatric nephrologists with the aim to document existing practice variation and compare practice with the recommendations of the Kidney Disease Improving Global Outcomes Clinical Practice Guideline for NS. Of the 58 nephrologists asked to participate in the survey, 40 (69 %) responded. Among these, 62 % prescribed initial daily glucocorticoid (GC) therapy for 6 weeks, 26 % for 4 weeks by 26 %, and 10 % prescribed 'other'. Alternate-day GC was continued for 6 weeks by 63 % of respondents and for >6 and <6 weeks by 32 and 6 %, respectively. For biopsy-confirmed minimal change disease, 65 and 46 % of respondents chose oral cyclophosphamide for frequently relapsing and steroid-dependent phenotypes, respectively; calcineurin inhibitors or mycophenolate were the second most popular choices. Kidney biopsy was 'always' performed by 16, 39, and 97 % of respondents for frequently relapsing, steroid-dependent, and steroid-resistant patients, respectively. Rituximab had been administered by 60 % of respondents; 22, 56, and 72 % reported that they would consider rituximab for frequently relapsing, steroid-dependent, and steroid-resistant patients, respectively. Most notable differences between practice and Guideline recommendations were first presentation GC duration, GC-sparing agent choices in frequently relapsing and steroid-dependent patients, and biopsy practices. There is substantial Canadian…