IgA nephropathy in adults-treatment standard.

Immunoglobulin A nephropathy (IgAN) is the most common primary form of glomerular disease worldwide and carries a high lifetime risk of kidney failure. The underlying pathogenesis of IgAN has been characterized to a sub-molecular level; immune complexes containing specific O-glycoforms of IgA1 are central. Kidney biopsy remains the gold-standard diagnostic test for IgAN and histological features (i.e. MEST-C score) have also been shown to independently predict outcome. Proteinuria and blood pressure are the main modifiable risk factors for disease progression. No IgAN-specific biomarker has yet been validated for diagnosis, prognosis or tracking response to therapy. There has been a recent resurgence of investigation into IgAN treatments. Optimized supportive care with lifestyle interventions and non-immunomodulatory drugs remains the backbone of IgAN management. The menu of available reno-protective medications is rapidly expanding beyond blockade of the renin-angiotensin-aldosterone system to include sodium-glucose cotransporter 2 and endothelin type A receptor antagonism. Systemic immunosuppression can further improve kidney outcomes, although recent randomized controlled trials have raised concerns regarding infectious and metabolic toxicity from systemic corticosteroids. Studies evaluating more refined approaches to immunomodulation in IgAN are ongoing: drugs targeting the mucosal immune compartment, B-cell promoting cytokines and the complement cascade are particularly promising. We review the current standards of treatment and discuss novel developments in pathophysiology, diagnosis, outcome prediction and management of IgAN.

Soluble CD89 is a critical factor for mesangial proliferation in childhood IgA nephropathy.

Childhood IgA nephropathy (IgAN) includes a wide spectrum of clinical presentations, from isolated hematuria to acute nephritis with rapid loss of kidney function. In adults, IgAN is an autoimmune disease and its pathogenesis involves galactose deficient (Gd) IgA1, IgG anti-Gd-IgA1 autoantibodies and the soluble IgA Fc receptor (CD89). However, implication of such factors, notably soluble CD89, in childhood IgAN pathogenesis remains unclear. Here, we studied these biomarkers in a cohort of 67 patients with childhood IgAN and 42 pediatric controls. While Gd-IgA1 was only moderately increased in patient plasma, levels of circulating IgA complexes (soluble CD89-IgA and IgG-IgA) and free soluble CD89 were markedly increased in childhood IgAN. Soluble CD89-IgA1 complexes and free soluble CD89 correlated with proteinuria, as well as histological markers of disease activity: mesangial, endocapillary hypercellularity and cellular crescents. Soluble CD89 was found in patient's urine but not in urine from pediatric controls. Mesangial deposits of soluble CD89 were detected in biopsies from patients with childhood IgAN. Serum chromatographic fractions containing covalently linked soluble CD89-IgA1 complexes or free soluble CD89 from patients induced mesangial cell proliferation in vitro in a soluble CD89-dependent manner. Recombinant soluble CD89 induced mesangial cell proliferation in vitro which was inhibited by free soluble recombinant CD71 (also a mesangial IgA receptor) or mTOR blockers. Interestingly, injection of recombinant soluble CD89 induced marked glomerular proliferation and proteinuria in mice expressing human IgA1. Thus, free and IgA1-complexed soluble CD89 are key players in mesangial proliferation. Hence, our findings suggest that soluble CD89 plays an essential role in childhood IgAN pathogenesis making it a potential biomarker and therapeutic target.

Specific immune biomarker monitoring in two children with severe IgA nephropathy and successful therapy with immunoadsorption in a rapidly progressive case.

BACKGROUND: Childhood IgA nephropathy (cIgAN) is one of the most common primary glomerulonephritides with the potential to evolve to kidney failure. IgAN is an autoimmune disease involving 3 key factors: galactose-deficient IgA1 (Gd-IgA1), anti-IgA1 autoantibodies, and soluble (s)CD89 IgA Fc receptor. These molecules and immune complexes have been described recently as potential biomarkers of disease progression in childhood IgAN but their evolution in time under immunosuppressive treatment remains unknown. METHODS: We performed a prospective study of two proliferative cIgAN patients by sequentially biomonitoring immune IgA complexes (sCD89-IgA, IgG-IgA), sCD89, and Gd-IgA1 and correlating them with clinical and histological outcome after treatment. RESULTS: After patient 1's treatment, a decrease in sCD89-IgA, IgG-IgA, and free sCD89 was linked to a decrease in proteinuria whereas eGFR (estimated glomerular filtration rate) and Gd-IgA1 levels remained stable. Patient 1 received tacrolimus and monthly intramuscular steroid injections of Kenacort for 10 months. At the end, a relapse induced an increase in proteinuria consistent with an increase of the 3 biomarkers. Patient 2 displayed rapidly progressive IgAN with crescents in more than 90% of glomeruli and received intense immunosuppression treatment associated with the immunoadsorption (IA) approach. During IA, proteinuria decreased rapidly, as well as levels of CD89-IgA, IgG-IgA, sCD89, and Gd-IgA1 biomarkers. After discontinuation of IA, proteinuria increased as well as IgG-IgA complexes whereas sCD89-IgA and sCD89 remained low. Further re-intensification of IA and addition of cyclophosphamide improved proteinuria again with reduced IgG-IgA. A second biopsy was performed showing a reduction of extracapillary proliferation to 6% of glomeruli and only 9% glomerulsoclerosis. CONCLUSIONS: In conclusion, sequential biomonitoring of Gd-IgA1, IgA-immune complexes, and sCD89 in cIgAN was found to be valuable, by correlating with clinical features and glomerular proliferative lesions in cIgAN. These biomarkers could represent useful tools to evaluate kidney injury without repeat kidney biopsies.

New therapeutic perspectives for IgA nephropathy in children.

Childhood IgA nephropathy (cIgAN) differs from the adult by having an abrupt clinical onset, often presenting as an acute attack that can progress to a chronic phase. No treatment guidelines have been established for the treatment of cIgAN. Given the severity of acute attack in children, and the number of life-years at stake, pediatricians prescribe immunosuppression in addition to renin-angiotensin system blockade. Non-specific immunosuppressors, such as corticosteroids, have systemic toxic effects, and given recent therapeutic advances in adult glomerulonephritis, new tailored strategies should be expected for children. The mucosal immune system has been highlighted as a key player in IgAN pathogenesis, and several biomarkers have been identified with a direct role in pathogenesis. In this review, we discuss current studies of conventional and novel therapeutic approaches for cIgAN.

Renin as a Marker of Tissue-Perfusion and Prognosis in Critically Ill Patients.

OBJECTIVES: To characterize renin in critically ill patients. Renin is fundamental to circulatory homeostasis and could be a useful marker of tissue-perfusion. However, diurnal variation, continuous renal replacement therapy and drug-interference could confound its use in critical care practice. DESIGN: Prospective observational study. SETTING: Single-center, mixed medical-surgical ICU in Europe. PATIENTS: Patients over 18 years old with a baseline estimated glomerular filtration rate greater than 30 mL/min/1.73 m and anticipated ICU stay greater than 24 hours. Informed consent was obtained from the patient or next-of-kin. INTERVENTIONS: Direct plasma renin was measured in samples drawn 6-hourly from arterial catheters in recumbent patients and from extracorporeal continuous renal replacement therapy circuits. Physiologic variables and use of drugs that act on the renin-angiotensin-aldosterone system were recorded prospectively. Routine lactate measurements were used for comparison. MEASUREMENTS AND MAIN RESULTS: One-hundred twelve arterial samples (n = 112) were drawn from 20 patients (65% male; mean ± SD, 60 ± 14 yr old) with septic shock (30%), hemorrhagic shock (15%), cardiogenic shock (20%), or no circulatory shock (35%). The ICU mortality rate was 30%. Renin correlated significantly with urine output (repeated-measures correlation coefficient = -0.29; p = 0.015) and mean arterial blood pressure (repeated-measures correlation coefficient = -0.35; p < 0.001). There was no diurnal variation of renin or significant interaction of renin-angiotensin-aldosterone system drugs with renin in this population. Continuous renal replacement therapy renin removal was negligible (mass clearance ± SD 4% ± 4.3%). There was a significant difference in the rate of change of renin over time between survivors and nonsurvivors (-32 ± 26 µU/timepoint vs +92 ± 57 µU/timepoint p = 0.03; mean ± SEM), but not for lactate (-0.14 ± 0.04 mM/timepoint vs +0.15 ± 0.21 mM/timepoint; p = 0.07). Maximum renin achieved significant prognostic value for ICU mortality (receiver operator curve area under the curve 0.80; p = 0.04), whereas maximum lactate did not (receiver operator curve area under the curve, 0.70; p = 0.17). CONCLUSIONS: In an heterogeneous ICU population, renin measurement was not significantly affected by diurnal variation, continuous renal replacement therapy, or drugs. Renin served as a marker of tissue-perfusion and outperformed lactate as a predictor of ICU mortality.

Modulation of the microbiota by oral antibiotics treats immunoglobulin A nephropathy in humanized mice.

BACKGROUND: Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. IgA is mainly produced by the gut-associated lymphoid tissue (GALT). Both experimental and clinical data suggest a role of the gut microbiota in this disease. We aimed to determine if an intervention targeting the gut microbiota could impact the development of disease in a humanized mouse model of IgAN, the α1KI-CD89Tg mice. METHODS: Four- and 12-week old mice were divided into two groups to receive either antibiotics or vehicle control. Faecal bacterial load and proteinuria were quantified both at the beginning and at the end of the experiment, when blood, kidneys and intestinal tissue were collected. Serum mouse immunoglobulin G (mIgG) and human immunoglobulin A1 (hIgA1)-containing complexes were quantified. Renal and intestinal tissue were analysed by optical microscopy after haematoxylin and eosin colouration and immunohistochemistry with anti-hIgA and anti-mouse CD11b antibodies. RESULTS: Antibiotic treatment efficiently depleted the faecal microbiota, impaired GALT architecture and impacted mouse IgA production. However, while hIgA1 and mIgG serum levels were unchanged, the antibiotic treatment markedly prevented hIgA1 mesangial deposition, glomerular inflammation and the development of proteinuria. This was associated with a significant decrease in circulating hIgA1-mIgG complexes. Notably, final faecal bacterial load strongly correlated with critical clinical and pathophysiological features of IgAN such as proteinuria and hIgA1-mIgG complexes. In addition, treatment with broad-spectrum antibiotics reverted established disease. CONCLUSIONS: These data support an essential role of the gut microbiota in the generation of mucosa-derived nephrotoxic IgA1 and in IgAN development, opening new avenues for therapeutic approaches in this disease.

Acute interstitial nephritis with podocyte foot-process effacement complicating Plasmodium falciparum infection.

BACKGROUND: Malarial acute renal failure (MARF) is a component of the severe malaria syndrome, and complicates 1-5% of malaria infections. This form of renal failure has not been well characterized by histopathology. CASE PRESENTATION: A 44 year-old male presented to the emergency department with a 5-day history of fever and malaise after returning from Nigeria. A blood film was positive for Plasmodium falciparum. His creatinine was 616 µmol/L coming from a normal baseline of 89 µmol/L. He had a urine protein:creatinine ratio of 346 mg/mmol (4.4 g/L). He required dialysis. A renal biopsy showed acute interstitial nephritis with podocyte foot-process effacement. He was treated with artesunate and his renal function improved. At 1 year follow-up his creatinine had plateaued at 120 µmol/L with persistent low-grade proteinuria. CONCLUSION: Acute interstitial nephritis and podocyte foot-process effacement might be under-recognized lesions in MARF. Studying the mechanisms of MARF could give insight into the immunopathology of severe malaria.

High-level artemisinin-resistance with quinine co-resistance emerges in P. falciparum malaria under in vivo artesunate pressure.

BACKGROUND: Humanity has become largely dependent on artemisinin derivatives for both the treatment and control of malaria, with few alternatives available. A Plasmodium falciparum phenotype with delayed parasite clearance during artemisinin-based combination therapy has established in Southeast Asia, and is emerging elsewhere. Therefore, we must know how fast, and by how much, artemisinin-resistance can strengthen. METHODS: P. falciparum was subjected to discontinuous in vivo artemisinin drug pressure by capitalizing on a novel model that allows for long-lasting, high-parasite loads. Intravenous artesunate was administered, using either single flash-doses or a 2-day regimen, to P. falciparum-infected humanized NOD/SCID IL-2Rγ-/-immunocompromised mice, with progressive dose increments as parasites recovered. The parasite's response to artemisinins and other available anti-malarial compounds was characterized in vivo and in vitro. RESULTS: Artemisinin resistance evolved very rapidly up to extreme, near-lethal doses of artesunate (240 mg/kg), an increase of > 3000-fold in the effective in vivo dose, far above resistance levels reported from the field. Artemisinin resistance selection was reproducible, occurring in 80% and 41% of mice treated with flash-dose and 2-day regimens, respectively, and the resistance phenotype was stable. Measuring in vitro sensitivity proved inappropriate as an early marker of resistance, as IC50 remained stable despite in vivo resistance up to 30 mg/kg (ART-S: 10.7 nM (95% CI 10.2-11.2) vs. ART-R30: 11.5 nM (6.6-16.9), F = 0.525, p = 0.47). However, when in vivo resistance strengthened further, IC50 increased 10-fold (ART-R240 100.3 nM (92.9-118.4), F = 304.8, p < 0.0001), reaching a level much higher than ever seen in clinical samples. Artemisinin resistance in this African P. falciparum strain was not associated with mutations in kelch-13, casting doubt over the universality of this genetic marker for resistance screening. Remarkably, despite exclusive exposure to artesunate, full resistance to quinine, the only other drug sufficiently fast-acting to deal with severe malaria, evolved independently in two parasite lines exposed to different artesunate regimens in vivo, and was confirmed in vitro. CONCLUSION: P. falciparum has the potential to evolve extreme artemisinin resistance and more complex patterns of multidrug resistance than anticipated. If resistance in the field continues to advance along this trajectory, we will be left with a limited choice of suboptimal treatments for acute malaria, and no satisfactory option for severe malaria.

The gut microbiota posttranslationally modifies IgA1 in autoimmune glomerulonephritis.

Mechanisms underlying the disruption of self-tolerance in acquired autoimmunity remain unclear. Immunoglobulin A (IgA) nephropathy is an acquired autoimmune disease where deglycosylated IgA1 (IgA subclass 1) auto-antigens are recognized by IgG auto-antibodies, forming immune complexes that are deposited in the kidneys, leading to glomerulonephritis. In the intestinal microbiota of patients with IgA nephropathy, there was increased relative abundance of mucin-degrading bacteria, including Akkermansia muciniphila. IgA1 was deglycosylated by A. muciniphila both in vitro and in the intestinal lumen of mice. This generated neo-epitopes that were recognized by autoreactive IgG from the sera of patients with IgA nephropathy. Mice expressing human IgA1 and the human Fc α receptor I (α1KI-CD89tg) that underwent intestinal colonization by A. muciniphila developed an aggravated IgA nephropathy phenotype. After deglycosylation of IgA1 by A. muciniphila in the mouse gut lumen, IgA1 crossed the intestinal epithelium into the circulation by retrotranscytosis and became deposited in the glomeruli of mouse kidneys. Human α-defensins-a risk locus for IgA nephropathy-inhibited growth of A. muciniphila in vitro. A negative correlation observed between stool concentration of α-defensin 6 and quantity of A. muciniphila in the guts of control participants was lost in patients with IgA nephropathy. This study demonstrates that gut microbiota dysbiosis contributes to generation of auto-antigens in patients with IgA nephropathy and in a mouse model of this disease.

Is There a Role for Gut Microbiome Dysbiosis in IgA Nephropathy?

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis and one of the leading causes of renal failure worldwide. The pathophysiology of IgAN involves nephrotoxic IgA1-immune complexes. These complexes are formed by galactose-deficient (Gd) IgA1 with autoantibodies against the hinge region of Gd-IgA1 as well as soluble CD89, an immune complex amplifier with an affinity for mesangial cells. These multiple molecular interactions result in the induction of the mesangial IgA receptor, CD71, injuring the kidney and causing disease. This review features recent immunological and microbiome studies that bring new microbiota-dependent mechanisms developing the disease based on data from IgAN patients and a humanized mouse model of IgAN. Dysbiosis of the microbiota in IgAN patients is also discussed in detail. Highlights of this review underscore that nephrotoxic IgA1 in the humanized mice originates from mucosal surfaces. Fecal microbiota transplantation (FMT) experiments in mice using stools from patients reveal a possible microbiota dysbiosis in IgAN with the capacity to induce progression of the disease whereas FMT from healthy hosts has beneficial effects in mice. The continual growth of knowledge in IgAN patients and models can lead to the development of new therapeutic strategies targeting the microbiota to treat this disease.

Rifaximin as a Potential Treatment for IgA Nephropathy in a Humanized Mice Model.

IgA Nephropathy (IgAN) is the most common glomerulonephritis worldwide, characterized by the mesangial deposition of abnormally glycosylated IgA1 (Gd-IgA). The production of Gd-IgA occurs in mucose-associated lymphoid tissue (MALT). The microbiota plays a role in MALT modulation. Rifaximin (NORMIX®), a non-absorbable oral antibiotic, induces positive modulation of the gut microbiota, favoring the growth of bacteria beneficial to the host. Here, we evaluate the effect of rifaximin on a humanized mice model of IgAN (α1KI-CD89Tg). Methods: The α1KI-CD89Tg mice were treated by the vehicle (olive oil) or rifaximin (NORMIX®). Serum levels of hIgA, hIgA1-sCD89, and mIgG-hIgA1 immune complexes were determined. Glomerular hIgA1 deposit and CD11b+ cells recruitment were revealed using confocal microscopy. Furthermore, the mRNA of the B-Cell Activating Factor (BAFF), polymeric immunoglobulin receptor (pIgR), and Tumor Necrosing Factor-α (TNF-α) in gut samples were detected by qPCR. Results: Rifaximin treatment decreased the urinary protein-to-creatinine ratio, serum levels of hIgA1-sCD89 and mIgG-hIgA1 complexes, hIgA1 glomerular deposition, and CD11b+ cell infiltration. Moreover, rifaximin treatment decreased significantly BAFF, pIgR, and TNF-α mRNA expression. Conclusions: Rifaximin decreased the IgAN symptoms observed in α1KI-CD89Tg mice, suggesting a possible role for it in the treatment of the disease.

Is complement the main accomplice in IgA nephropathy? From initial observations to potential complement-targeted therapies.

IgA Nephropathy (IgAN) is the main cause of primary glomerulonephritis, globally. This disease is associated with a wide range of clinical presentations, variable prognosis and a spectrum of histological findings. More than fifty years after its first description, this heterogeneity continues to complicate efforts to understand the pathogenesis. Nevertheless, involvement of the complement system in IgAN was identified early on. Dysfunction of the immunoglobulin A (IgA) system, the principal offender in this disease, including modification of isoforms and glycoforms of IgA1, the nature of immune complexes and autoantibodies to galactose deficient IgA1 might all be responsible for complement activation in IgAN. However, the specific mechanisms engaging complement are still under examination. Research in this domain should allow for identification of patients that may benefit from complement-targeted therapy, in the foreseeable future.

Malaria, Collapsing Glomerulopathy, and Focal and Segmental Glomerulosclerosis.

BACKGROUND AND OBJECTIVES: Malaria, a potentially life-threatening disease, is the most prevalent endemic infectious disease worldwide. In the modern era, the spectrum of glomerular involvement observed in patients after malarial infections remains poorly described. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: We therefore performed a retrospective multicenter study to assess the clinical, biologic, pathologic, and therapeutic characteristics of patients with glomerular disease demonstrated by kidney biopsy in France within 3 months of an acute malaria episode. RESULTS: We identified 23 patients (12 men), all but 1 of African ancestry and including 10 patients with concomitant HIV infection. All of the imported cases were in French citizens living in France who had recently traveled back to France from an endemic area and developed malaria after their return to France. Eleven patients had to be admitted to an intensive care unit at presentation. Plasmodium falciparum was detected in 22 patients, and Plasmodium malariae was detected in 1 patient. Kidney biopsy was performed after the successful treatment of malaria, a mean of 24 days after initial presentation. At this time, all patients displayed AKI, requiring KRT in 12 patients. Nephrotic syndrome was diagnosed in 17 patients. Pathologic findings included FSGS in 21 patients and minimal change nephrotic syndrome in 2 patients. Among patients with FSGS, 18 had collapsing glomerulopathy (including 9 patients with HIV-associated nephropathy). In four patients, immunohistochemistry with an antibody targeting P. falciparum histidine-rich protein-2 demonstrated the presence of the malaria antigen in tubular cells but not in podocytes or parietal epithelial cells. An analysis of the apoL1 risk genotype showed that high-risk variants were present in all seven patients tested. After a mean follow-up of 23 months, eight patients required KRT (kidney transplantation in two patients), and mean eGFR for the other patients was 51 ml/min per 1.73 m2. CONCLUSIONS: In patients of African ancestry, imported Plasmodium infection may be a new causal factor for secondary FSGS, particularly for collapsing glomerulopathy variants in an APOL1 high-risk variant background.

Angiotensin II in Refractory Septic Shock.

Refractory septic shock is defined as persistently low mean arterial blood pressure despite volume resuscitation and titrated vasopressors/inotropes in patients with a proven or suspected infection and concomitant organ dysfunction. Its management typically requires high doses of catecholamines, which can induce significant adverse effects such as ischemia and arrhythmias. Angiotensin II (Ang II), a key product of the renin-angiotensin-aldosterone system, is a vasopressor agent that could be used in conjunction with other vasopressors to stabilize critically ill patients during refractory septic shock, and reduce catecholamine requirements. However, very few clinical data are available to support Ang II administration in this setting. Here, we review the current literature on this topic to better understand the role of Ang II administration during refractory septic shock, differentiating experimental from clinical studies. We also consider the potential role of exogenous Ang II administration in specific organ dysfunction and possible pitfalls with Ang II in sepsis. Various issues remain unresolved and future studies should investigate important topics such as: the optimal dose and timing of Ang II administration, a comparison between Ang II and the other vasopressors (epinephrine; vasopressin), and Ang II effects on microcirculation.

What should the characteristics and attributes of an accredited nephrology training programme be? Looking for high standards.

The Renal Section of the European Union of Medical Specialists is working towards harmonization and optimization of nephrology training across Europe and its Mediterranean borders. In addition to the need for harmonization of the heterogeneous time dedicated to training, it is necessary to ensure that the learning environment is of a sufficiently high standard to develop skilled specialists. Thus, there is a need to review the core educational infrastructure and resources that should be provided to trainees in order to be considered centres of excellence for nephrology training. This review addresses most of the characteristics and attributes that constitute a high-calibre training centre of excellence, considering that a training centre might not represent a single institution, but a network of institutions that provide a coordinated and complete curriculum to the trainee. The training institution should provide, apart from the classical current nephrological facilities (clinical nephrology, haemodialysis, peritoneal dialysis and transplantation), a number of other complementary facilities, including immunology, nephropathology-with a dedicated and expert renal pathologist-all the specialities of general medicine and general surgery and, in particular, vascular surgery, radiology and interventional radiology specialist services (renal biopsy, renal ultrasound and permanent vascular access) and intensive care unit. In addition to clinical training, a training centre of excellence should offer research facilities to allow trainees the opportunity to be involved in epidemiological, clinical, translational or basic scientific research. The training centres should ideally hold a certification of training accreditation. If the European and its Mediterranean border countries wish to guarantee a high standard of training in nephrology, their national health services need to recognize their responsibility towards the importance of doctor training, providing enough time for educational activities and investing in the resources required for high-standard specialist training.

Chromosomal rearrangement-A rare cause of complement factor I associated atypical haemolytic uraemic syndrome.

Chromosomal rearrangements affecting the genes encoding complement factor H and the factor H related proteins have been described in aHUS patients. To date such disorders have not been described in other aHUS associated genes. We describe here a heterozygous 875,324bp deletion encompassing the gene (CFI) encoding complement factor I and ten other genes. The index case presented with aHUS and did not recover renal function. No abnormalities were detected on Sanger sequencing of CFI but a low factor I level led to a multiplex ligation-dependent probe amplification assay being undertaken. This showed a complete heterozygous deletion of CFI. The extent of the deletion and the breakpoint was defined. In the Newcastle aHUS cohort we have identified and report here 32 different CFI variants in 56 patients but to date this is the only deletion that we have identified. This finding although rare does suggest that screening for chromosomal rearrangements affecting CFI should be undertaken in all aHUS patients particularly if the factor I level is unexplainably low.