An update on the pathogenesis and treatment of IgA nephropathy

Protocol for a systematic review of the application of the kidney failure risk equation and Oxford classification in estimating prognosis in IgA nephropathy

BACKGROUND

IgA nephropathy (IgAN) is a common cause of chronic kidney disease (CKD) and end-stage renal disease (ESRD). Outcomes are highly variable and predicting risk of disease progression at an individual level is challenging. Accurate risk stratification is important to identify individuals most likely to benefit from treatment. The Kidney Failure Risk Equation (KFRE) has been extensively validated in CKD populations and predicts the risk of ESRD at 2 and 5 years using non-invasive tests; however, its predictive performance in IgAN is unknown. The Oxford classification (OC) describes pathological features demonstrated on renal biopsy that are associated with adverse clinical outcomes that may also inform prognosis. The objective of this systematic review is to compare the KFRE with the OC in determining prognosis in IgAN.

METHODS

A systematic review will be conducted and reported in line with PRISMA guidelines (PRISMA-P checklist attached as Additional file 1). Inclusion criteria will be cohort studies that apply the KFRE or OC to determine the risk of CKD progression or ESRD in individuals with IgAN. Multiple databases will be searched in duplicate to identify relevant studies, which will be screened first by title, then by abstract and then by full-text analysis. Results will be collated for comparison. Risk of bias and confidence assessments will be conducted independently by two reviewers, with a third reviewer available if required.

DISCUSSION

Identifying individuals at the highest risk of progression to ESRD is challenging in IgAN, due to the heterogeneity of clinical outcomes. Risk prediction tools have been developed to guide clinicians; however, it is imperative that these aids are accurate and reproducible. The OC is based on observations made by specialist renal pathologists and may be open to observer bias, therefore the utility of prediction models incorporating this classification may be diminished, particularly as in the future novel biomarkers may be incorporated into clinical practice.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42022364569.

Diagnosing and Treating IgAN: Steroids, Budesonide, or Maybe Both?

IgA nephropathy (IgAN), the most common primary glomerulonephritis worldwide, is characterized by a mesangial IgA deposit and a variety of histological lesions, as described by the Oxford classification system. Despite the well-described "four-hit hypothesis", there are still plenty of less or undescribed mechanisms that participate in the disease pathogenesis, such as B-cell priming, which seems to be initiated by different antigens in the intestinal microbiota. Diagnosis of the disease is currently based on kidney biopsy findings, as the sensitivity and specificity of the many serum and urinary biomarkers described so far do not seem to have diagnostic accuracy. Therapeutic strategies consist of the initial step of non-immune medication, aiming to reduce both the intraglomerular pressure and proteinuria to below 0.5 g/day, followed by systemic corticosteroid administration in patients who remain at high risk for progressive chronic kidney disease despite the maximum non-immune treatment. The 6-month systemic corticosteroid treatment reduces proteinuria levels; however, the increased possibility of adverse events and increased relapse rate after treatment raises the need for a new therapeutic approach. Targeted-release budesonide is a therapeutic modality that aims to inhibit disease pathogenetic pathways at early stages; it has minor systemic absorption and proven beneficial effects on renal function and proteinuria. In the present systemic review, the benefits and adverse events of steroids and budesonide are described, and the possibility of combined treatment is questioned in selected cases with active histologic lesions.

A Phase 2 Trial of Sibeprenlimab in Patients with IgA Nephropathy

BACKGROUND

A proliferation-inducing ligand (APRIL) is implicated in the pathogenesis of IgA nephropathy. Sibeprenlimab is a humanized IgG2 monoclonal antibody that binds to and neutralizes APRIL.

METHODS

In this phase 2, multicenter, double-blind, randomized, placebo-controlled, parallel-group trial, we randomly assigned adults with biopsy-confirmed IgA nephropathy who were at high risk for disease progression, despite having received standard-care treatment, in a 1:1:1:1 ratio to receive intravenous sibeprenlimab at a dose of 2, 4, or 8 mg per kilogram of body weight or placebo once monthly for 12 months. The primary end point was the change from baseline in the log-transformed 24-hour urinary protein-to-creatinine ratio at month 12. Secondary end points included the change from baseline in the estimated glomerular filtration rate (eGFR) at month 12. Safety was also assessed.

RESULTS

Among 155 patients who underwent randomization, 38 received sibeprenlimab at a dose of 2 mg per kilogram, 41 received sibeprenlimab at a dose of 4 mg per kilogram, 38 received sibeprenlimab at a dose of 8 mg per kilogram, and 38 received placebo. At 12 months, the geometric mean ratio reduction (±SE) from baseline in the 24-hour urinary protein-to-creatinine ratio was 47.2±8.2%, 58.8±6.1%, 62.0±5.7%, and 20.0±12.6% in the sibeprenlimab 2-mg, 4-mg, and 8-mg groups and the placebo group, respectively. At 12 months, the least-squares mean (±SE) change from baseline in eGFR was -2.7±1.8, 0.2±1.7, -1.5±1.8, and -7.4±1.8 ml per minute per 1.73 m2 in the sibeprenlimab 2-mg, 4-mg, and 8-mg groups and the placebo group, respectively. The incidence of adverse events that occurred after the start of administration of sibeprenlimab or placebo was 78.6% in the pooled sibeprenlimab groups and 71.1% in the placebo group.

CONCLUSIONS

In patients with IgA nephropathy, 12 months of treatment with sibeprenlimab resulted in a significantly greater decrease in proteinuria than placebo. (Funded by Visterra; ENVISION ClinicalTrials.gov number, NCT04287985; EudraCT number, 2019-002531-29.).

The contribution of a proliferation-inducing ligand (APRIL) and other TNF superfamily members in pathogenesis and progression of IgA nephropathy

Advances in our understanding of the pathogenesis of immunoglobulin A nephropathy (IgAN) have led to the identification of novel therapeutic targets and potential disease-specific treatments. Specifically, a proliferation-inducing ligand (APRIL) has been implicated in the pathogenesis of IgAN, mediating B-cell dysregulation and overproduction of pathogenic galactose-deficient IgA1 (Gd-IgA1). Animal and clinical studies support the involvement of APRIL in the pathogenesis and progression of IgAN. An elevated level of APRIL is found in IgAN when compared with controls, which correlates with the level of Gd-IgA1 and associates with more severe disease presentation and worse outcomes. Conversely, anti-APRIL therapy reduces pathogenic Gd-IgA1 and IgA immune complex formation and ameliorates the severity of kidney inflammation and injury. Genome-wide association studies in IgAN have identified TNFSF13 and TNFRSF13B, a cytokine ligand-receptor gene pair encoding APRIL and its receptor, respectively, as risk susceptibility loci in IgAN, further supporting the causal role of the APRIL signalling pathway in IgAN. Several novel experimental agents targeting APRIL, including atacicept, telitacicept, zigakibart and sibeprenlimab, are currently under investigation as potential therapies in IgAN. Preliminary results suggest that these agents are well-tolerated, and reduce levels of Gd-IgA1, with corresponding improvement in proteinuria. Further studies are ongoing to confirm the safety and efficacy of anti-APRIL approaches as an effective therapeutic strategy in IgAN.

Hydroxychloroquine in nephrology: current status and future directions

Hydroxychloroquine is one of the oldest disease-modifying anti-rheumatic drugs in clinical use. The drug interferes with lysosomal activity and antigen presentation, inhibits autophagy, and decreases transcription of pro-inflammatory cytokines. Owing to its immunomodulatory, anti-inflammatory, anti-thrombotic effect, hydroxychloroquine has been an integral part of therapy for systemic lupus erythematosus and lupus nephritis for several decades. The therapeutic versatility of hydroxychloroquine has led to repurposing it for other clinical conditions, with recent studies showing reduction in proteinuria in IgA nephropathy. Research is also underway to investigate the efficacy of hydroxychloroquine in primary membranous nephropathy, Alport's syndrome, systemic vasculitis, anti-GBM disease, acute kidney injury and for cardiovascular risk reduction in chronic kidney disease. Hydroxychloroquine is well-tolerated, inexpensive, and widely available and therefore, should its indications expand in the future, it would certainly be welcomed. However, clinicians should be aware of the risk of irreversible and progressive retinal toxicity and rarely, cardiomyopathy. Monitoring hydroxychloroquine levels in blood appears to be a promising tool to evaluate compliance, individualize the dose and reduce the risk of retinal toxicity, although this is not yet standard clinical practice. In this review, we discuss the existing knowledge regarding the mechanism of action of hydroxychloroquine, its utility in lupus nephritis and other kidney diseases, the main adverse effects and the evidence gaps that need to be addressed in future research. Created with Biorender.com. HCQ, hydroxychloroquine; GBM, glomerular basement membrane; mDC, myeloid dendritic cell; MHC, major histocompatibility complex; TLR, toll-like receptor.

Efficacy and safety of a targeted-release formulation of budesonide in patients with primary IgA nephropathy (NefIgArd): 2-year results from a randomised phase 3 trial

BACKGROUND

IgA nephropathy is a chronic immune-mediated kidney disease and a major cause of kidney failure worldwide. The gut mucosal immune system is implicated in its pathogenesis, and Nefecon is a novel, oral, targeted-release formulation of budesonide designed to act at the gut mucosal level. We present findings from the 2-year, phase 3 NefIgArd trial of Nefecon in patients with IgA nephropathy.

METHODS

In this phase 3, multicentre, randomised, double-blind, placebo-controlled trial, adult patients (aged ≥18 years) with primary IgA nephropathy, estimated glomerular filtration rate (eGFR) 35-90 mL/min per 1·73 m2, and persistent proteinuria (urine protein-creatinine ratio ≥0·8 g/g or proteinuria ≥1 g/24 h) despite optimised renin-angiotensin system blockade were enrolled at 132 hospital-based clinical sites in 20 countries worldwide. Patients were randomly assigned (1:1) to receive 16 mg/day oral capsules of Nefecon or matching placebo for 9 months, followed by a 15-month observational follow-up period off study drug. Randomisation via an interactive response technology system was stratified according to baseline proteinuria (<2 or ≥2 g/24 h), baseline eGFR (<60 or ≥60 mL/min per 1·73 m2), and region (Asia-Pacific, Europe, North America, or South America). Patients, investigators, and site staff were masked to treatment assignment throughout the 2-year trial. Optimised supportive care was also continued throughout the trial. The primary efficacy endpoint was time-weighted average of eGFR over 2 years. Efficacy and safety analyses were done in the full analysis set (ie, all randomly assigned patients). The trial was registered on ClinicalTrials.gov, NCT03643965, and is completed.

FINDINGS

Patients were recruited to the NefIgArd trial between Sept 5, 2018, and Jan 20, 2021, with 364 patients (182 per treatment group) randomly assigned in the full analysis set. 240 (66%) patients were men and 124 (34%) were women, and 275 (76%) identified as White. The time-weighted average of eGFR over 2 years showed a statistically significant treatment benefit with Nefecon versus placebo (difference 5·05 mL/min per 1·73 m2 [95% CI 3·24 to 7·38], p<0·0001), with a time-weighted average change of -2·47 mL/min per 1·73 m2 (95% CI -3·88 to -1·02) reported with Nefecon and -7·52 mL/min per 1·73 m2 (-8·83 to -6·18) reported with placebo. The most commonly reported treatment-emergent adverse events during treatment with Nefecon were peripheral oedema (31 [17%] patients, vs placebo, seven [4%] patients), hypertension (22 [12%] vs six [3%]), muscle spasms (22 [12%] vs seven [4%]), acne (20 [11%] vs two [1%]), and headache (19 [10%] vs 14 [8%]). No treatment-related deaths were reported.

INTERPRETATION

A 9-month treatment period with Nefecon provided a clinically relevant reduction in eGFR decline and a durable reduction in proteinuria versus placebo, providing support for a disease-modifying effect in patients with IgA nephropathy. Nefecon was also well tolerated, with a safety profile as expected for a locally acting oral budesonide product.

FUNDING

Calliditas Therapeutics.

Results from part A of the multi-center, double-blind, randomized, placebo-controlled NefIgArd trial, which evaluated targeted-release formulation of budesonide for the treatment of primary immunoglobulin A nephropathy

The therapeutic potential of a novel, targeted-release formulation of oral budesonide (Nefecon) for the treatment of IgA nephropathy (IgAN) was first demonstrated by the phase 2b NEFIGAN trial. To verify these findings, the phase 3 NefigArd trial tested the efficacy and safety of nine months of treatment with Nefecon (16 mg/d) versus placebo in adult patients with primary IgAN at risk of progressing to kidney failure (ClinicalTrials.gov: NCT03643965). NefIgArd was a multicenter, randomized, double-blind, placebo-controlled two-part trial. In Part A, 199 patients with IgAN were treated with Nefecon or placebo for nine months and observed for an additional three months. The primary endpoint for Part A was 24-hour urine protein-to-creatinine ratio (UPCR) after nine months. Secondary efficacy outcomes evaluated included estimated glomerular filtration rate (eGFR) at nine and 12 months and the UPCR at 12 months. At nine months, UPCR was 27% lower in the Nefecon group compared with placebo, along with a benefit in eGFR preservation corresponding to a 3.87 ml/min/1.73 m2 difference versus placebo (both significant). Nefecon was well-tolerated, and treatment-emergent adverse events were mostly mild to moderate in severity and reversible. Part B is ongoing and will be reported on later. Thus, NefIgArd is the first phase 3 IgA nephropathy trial to show clinically important improvements in UPCR and eGFR and confirms the findings from the phase 2b NEFIGAN study.

Current knowledge of targeted-release budesonide in immunoglobulin A nephropathy: A comprehensive review

Immunoglobulin A (IgA) nephropathy is a common autoimmune kidney disease. Accumulating studies showed that IgA nephropathy may be partially correlated with mucosal immune system dysfunction. Systemic corticosteroid treatment exerts an essential protective effect against renal deterioration in IgA nephropathy. However, long-term use of corticosteroids may cause systemic side effects. The novel targeted-release formulation (TRF) of budesonide has been shown to deliver the drug to the distal ileum with the aim of minimizing adverse events for patients with IgA nephropathy. In this review, we have summarized all the current evidence of the effects of TRF-budesonide protecting against IgA nephropathy. Three randomized controlled trials (RCTs), one cohort, two case reports, and an ongoing Phase 3 trial (Part B, NCT03643965), were under comprehensive review. These included studies demonstrated that TRF-budesonide could remarkably reduce proteinuria, hematuria, and creatinine, as well as preserve renal function. The local immunosuppressive effects exhibited by TRF-budesonide may represent a novel and promising approach to treating IgA nephropathy. However, the current evidence was only derived from limited trials. Therefore, more well-designed RCTs are still warranted to validate the curable profile of TRF-budesonide in treating IgA nephropathy.

Randomized Phase II JANUS Study of Atacicept in Patients With Immunoglobulin A Nephropathy and Persistent Proteinuria

Introduction

Patients with IgA nephropathy (IgAN) and persistent proteinuria are at risk of progression to kidney failure. Atacicept is a novel B-cell–targeted immunomodulator, shown to reduce immunoglobulin levels in patients with autoimmune diseases.

Methods

JANUS (NCT02808429) was a phase II study that assessed the safety, pharmacodynamic effects, and efficacy of atacicept in patients with IgAN and proteinuria ≥1 g/d or 0.75 mg/mg on 24-hour UPCR despite maximal standard of care therapy.

Results

A total of 16 patients were randomized 1:1:1 to placebo (n = 5), atacicept 25 mg (n = 6), or atacicept 75 mg (n = 5) once weekly using subcutaneous injection. Twelve (75%) completed ≥48 weeks of treatment; 8 (50%) completed 72 weeks of treatment and the 24-week safety follow-up period. Fourteen patients reported treatment-emergent adverse events (TEAEs). Most TEAEs were mild or moderate in severity. Three patients (placebo n = 1; atacicept 25 mg n = 2) reported serious TEAEs, none of which were treatment related. Dose-dependent reductions in IgA, IgG, IgM, and galactose-deficient (Gd)-IgA1 with atacicept at week 24 were maintained to week 72. Early reduction in proteinuria was observed at week 24 with atacicept. Renal function progressively declined with placebo but remained stable under exposure to atacicept.

Conclusion

Atacicept has an acceptable safety profile in patients with IgAN and is effective at reducing the levels of pathogenic factor Gd-IgA1, with potential improvements in proteinuria and renal function.

Renal autoimmunity: The role of bacterial and viral infections, an extensive review

Autoimmunity is a process by which the loss of self-tolerance results in an immune attack against the body own tissues and organs. For autoimmunity to occur, various elements serving as triggers were described by which infections are considered one of the leading factors. In turn, renal involvement in autoimmune diseases, whether by an organ-specific attack, or as part of a systemic disease process, is well known. As bacterial and viral infections are considered to be common triggers for autoimmunity in general, we aimed to study their association with renal autoimmunity in particular. We performed an extensive search of the recent and relevant medical literature regarding renal autoimmunity syndromes such as infection-associated glomerulonephritis and vasculitis, associated with bacterial and viral infections. By utilizing PubMed and Google Scholar search engines, over 200 articles and case reports were reviewed. Among other mechanisms, direct infection of the renal parenchyma, molecular mimicry, induction of B-cells or secretion of superantigens, bacterial and viral pathogens were found to correlate with the development of renal autoimmunity. Nevertheless, this was not true for all pathogens, as some mimic autoimmune diseases and others show a surprisingly protective effect. The exact immunopathogenesis is yet to be determined, however. For conclusion, bacterial and viral infections are linked to renal autoimmunity by both direct damage and as mediators of systemic diseases. Further research particularly on the immunopathogenetic mechanisms of renal autoimmunity associated with infections is required.

Urinary C5b-9 as a Prognostic Marker in IgA Nephropathy

C5b-9 plays an important role in the pathogenesis of immunoglobin A nephropathy (IgAN). We evaluated C5b-9 as a prognostic marker for IgAN. We prospectively enrolled 33 patients with biopsy-proven IgAN. We analyzed the correlation between baseline urinary C5b-9 levels, posttreatment changes in their levels, and clinical outcomes, including changes in proteinuria, estimated glomerular filtration rate (eGFR), and treatment response. Baseline urinary C5b-9 levels were positively correlated with proteinuria (r = 0.548, p = 0.001) at the time of diagnosis. Changes in urinary C5b-9 levels were positively correlated with changes in proteinuria (r = 0.644, p < 0.001) and inversely correlated with changes in eGFR (r = −0.410, p = 0.018) at 6 months after treatment. Changes in urinary C5b-9 levels were positively correlated with time-averaged proteinuria during the follow-up period (r= 0.461, p = 0.007) but were not correlated with the mean annual rate of eGFR decline (r = −0.282, p = 0.112). Baseline urinary C5b-9 levels were not a significant independent factor that could predict the treatment response in logistic regression analyses (odds ratio 0.997; 95% confidence interval, 0.993 to 1.000; p = 0.078). Currently, urinary C5b-9 is not a promising prognostic biomarker for IgAN, and further studies are needed.

An Update on Targeted Treatment of IgA Nephropathy: An Autoimmune Perspective

Immunoglobulin (Ig) A nephropathy (IgAN) is the commonest form of primary glomerulonephritis worldwide and is, considered a significant cause of end-stage renal disease in young adults. The precise pathogenesis of IgAN is unclear. The clinical and pathological features vary significantly between individuals and races, which makes treating IgAN difficult. Currently, the therapeutic strategies in IgAN are still optimal blood pressure control and proteinuria remission to improve the renal function in most cases. Immunosuppressive drugs such as corticosteroids can be considered in patients with persistent proteinuria and a high risk of renal function decline; however, they include a high toxicity profile. Therefore, the safety and selectivity of medications are critical concerns in the treatment of IgAN. Various pharmacological therapeutic targets have emerged based on the evolving understanding of the autoimmune pathogenesis of IgAN, which involves the immune response, mucosal immunity, renal inflammation, complement activation, and autophagy; treatments based on these mechanisms have been explored in preclinical and clinical studies. This review summarizes the progress concerning targeted therapeutic strategies and the relevant autoimmune pathogenesis in IgAN.

Aberrantly Glycosylated IgA1 in IgA Nephropathy: What We Know and What We Don't Know

IgA nephropathy (IgAN), the most common primary glomerular disease worldwide, is characterized by glomerular deposition of IgA1-containing immune complexes. The IgA1 hinge region (HR) has up to six clustered O-glycans consisting of Ser/Thr-linked N-acetylgalactosamine usually with β1,3-linked galactose and variable sialylation. Circulating levels of IgA1 with abnormally O-glycosylated HR, termed galactose-deficient IgA1 (Gd-IgA1), are increased in patients with IgAN. Current evidence suggests that IgAN is induced by multiple sequential pathogenic steps, and production of aberrantly glycosylated IgA1 is considered the initial step. Thus, the mechanisms of biosynthesis of aberrantly glycosylated IgA1 and the involvement of aberrant glycoforms of IgA1 in disease development have been studied. Furthermore, Gd-IgA1 represents an attractive biomarker for IgAN, and its clinical significance is still being evaluated. To elucidate the pathogenesis of IgAN, it is important to deconvolute the biosynthetic origins of Gd-IgA1 and characterize the pathogenic IgA1 HR O-glycoform(s), including the glycan structures and their sites of attachment. These efforts will likely lead to development of new biomarkers. Here, we review the IgA1 HR O-glycosylation in general and the role of aberrantly glycosylated IgA1 in the pathogenesis of IgAN in particular.

Mass spectrometry-based screening identifies circulating immunoglobulinA-α1-microglobulin complex as potential biomarker in immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is characterized by predominant IgA deposition in the glomerular mesangium. Previous studies have proved that renal-deposited IgA in IgAN came from circulating IgA1-containing complexes (CICs).

METHODS

To explore the composition of CICs in IgAN, we isolated CICs from IgAN patients and healthy controls and then quantitatively analyzed them by mass spectrometry. Meanwhile, the isolated CICs were used to treat human mesangial cells to monitor mesangial cell injury. Using the protein content and injury effects, the key constituent in CICs was identified. Then the circulating levels of identified key constituent-IgA complex were detected in an independent population by an in-house-developed enzyme-linked immunosorbent assay.

RESULTS

By comparing the proteins of CICs between IgAN patients and controls, we found that 14 proteins showed significantly different levels. Among them, α1-microglobulin content in CICs was associated with not only in vitro mesangial cell proliferation and monocyte chemoattractant protein 1 secretion, but also in vivo estimated glomerular filtration rate (eGFR) levels and tubulointerstitial lesions in IgAN patients. Moreover, we found α1-microglobulin was prone to bind aberrant glycosylated IgA1. Additionally, elevated circulating IgA-α1-microglobulin complex levels were detected in an independent IgAN population and IgA-α1-microglobulin complex levels were correlated with hypertension, eGFR levels and Oxford T- scores in these IgAN patients.

CONCLUSIONS

Our results suggest that the IgA-α1-microglobulin complex is an important constituent in CICs and that circulating IgA-α1-microglobulin complex detection might serve as a potential noninvasive biomarker detection method for IgAN.

Deletion of the miR-25/93/106b cluster induces glomerular deposition of immune complexes and renal fibrosis in mice

IgA nephropathy (IgAN), the most common form of primary glomerulonephritis, is caused by immune system dysfunction and affects only the kidneys. miRNA was involved in IgAN, in which their roles are still unknown. Herein, we found increased glomerular medulla size, proteinuria, kidney artery resistance, kidney fibrosis and immune complex deposition in 5‐month miR‐25/93/106b cluster knockout (miR‐TKO) mice. In vitro, the inhibition of miR‐25 cluster could promote cell proliferation and increase fibrosis‐related protein and transferrin receptor (TFRC) expression in human renal glomerular mesangial cell (HRMC). Luciferase assay revealed that inhibition of miR‐93/106b cluster could upregulate Ccnd1 expression through direct binding with the 3’UTR of Ccnd1. Conversely, inhibition of Ccnd1 expression prevented miR‐93/106b‐induced effect in HRMC. These findings suggested that miR‐25 cluster played an important role in the progression of IgAN, which provided new insights into the pathogenesis and treatment of IgAN.

B cell and monocyte phenotyping: A quick asset to investigate the immune status in patients with IgA nephropathy

Background

IgA nephropathy (IgAN) advances from multiple pathogenic “hits” resulting in poorly O-galactosylated IgA1 glycoforms (Gd-IgA1), production of antibodies and glomerular deposition of immune complexes. A sequence of immune responses arising from plasma cells, T cells and antigen presenting cells (APCs), causes glomerular injury. This study was designed to phenotype subsets of B cells, monocytes and T cells in the peripheral circulation and their association with inflammatory cytokines and kidney function in patients with IgAN, healthy controls (HC) and disease controls with autosomal dominant polycystic kidney disease (ADPKD).

Methods

Patients with IgAN (n = 13), median estimated glomerular filtration rate (eGFR) of 57 ml/min/1.73m² (IQR 42–84), patients with ADPKD (n = 13) matched for kidney function, gender and age and gender and age-matched HC (n = 13) were recruited. CD3+ and CD3- peripheral blood mononuclear cells were isolated and profiled based on their specific surface markers for different subsets of monocytes, B and T cells and analyzed by flow cytometry. Cytokines were analyzed by ELISA.

Results

We observed a significant decrease in the proportion of pre-switched B cells and plasmablasts, but an increase in long-lived plasma cells in the peripheral circulation of IgAN patients compared to HC. The proportion of non-classical monocytes was significantly higher in IgAN patients compared to both HC and ADPKD. We also report an association between sCD40L levels and the proportion of pre-switched B cells, as well as sCD40L and MCP-1 levels and albuminuria in IgAN patients.

Conclusions

We applied an easy-access method to analyze subsets of immune cells as well as relevant inflammatory mediators in IgAN patients. Our data demonstrate an altered B cell profile that indicates a pathophysiological role of the B cell lineage and an increased proportion of non-classical monocytes that suggests their role in the disease process.

Immunoglobulin-A Vasculitis With Renal Involvement in a Patient With COVID-19: A Case Report and Review of Acute Kidney Injury Related to SARS-CoV-2

Rationale:

Acute kidney injury is a common complication of COVID-19 and is associated with significantly increased mortality. The most frequent renal biopsy finding with SARS-CoV-2 infection is acute tubular injury; however, new onset glomerular diseases have been reported. The development of persistent urinary abnormalities in patients with COVID-19 should prompt consideration for renal biopsy to rule out glomerulonephritis.

Presenting Concerns:

A 30-year-old man with no prior medical history presented to the emergency department with symptoms of COVID-19 and new onset painful purpuric rash, arthralgia, and abdominal pain. SARS-CoV-2 infection was confirmed with nucleic acid testing and laboratory investigations revealed preserved renal function with dysmorphic hematuria and nephrotic range proteinuria.

Diagnosis:

A skin biopsy of the purpuric rash was performed, which demonstrated leukocytoclastic vasculitis. Renal biopsy revealed focally crescentic and segmentally necrotizing IgA nephropathy. Overall, given the clinical syndrome of glomerulonephritis with purpuric rash, arthralgia, and abdominal pain, the presentation is most in keeping with a diagnosis of IgA vasculitis in the setting of COVID-19.

Interventions:

The patient was treated conservatively for COVID-19 in the community. A 7-day course of prednisone was started for the vasculitic rash. IgA nephropathy was managed conservatively with blood pressure control and RAAS blockade with losartan.

Outcomes:

With conservative management, the patient’s COVID-19 symptoms resolved completely and he did not require hospital admission. Following prednisone therapy, the patient’s rash, arthralgia, and abdominal pain improved. However, despite resolution of COVID-19, hematuria and proteinuria persisted. With the initiation of RAAS blockade, renal function remained stable and proteinuria improved dramatically at 6 weeks.

Novel Findings:

De novo glomerulonephritis is a renal manifestation of SARS-CoV-2 infection beyond acute tubular injury. IgA vasculitis appears to be a rare complication of COVID-19.

IgA Nephropathy: An Interesting Autoimmune Kidney Disease

Immunoglobulin A nephropathy (IgAN) is the most common primary glomerulonephritis worldwide. It is a leading cause of chronic kidney disease and progresses to end-stage kidney disease in up to 40% of patients about 20 years after diagnosis. Additionally, IgAN is associated with significant mortality. The diagnosis currently necessitates a kidney biopsy, as no biomarker sufficiently specific and sensitive is available to supplant the procedure. Patients display significant heterogeneity in the epidemiology, clinical manifestations, renal progression, and long-term outcomes across diverse racial and ethnic populations. Recent advances in understanding the underlying pathophysiology of the disease have led to the proposal of a four-hit hypothesis supporting an autoimmune process. To date, there is no disease-specific treatment but, with a better understanding of the disease pathogenesis, new therapeutic approaches are currently being tested in clinical trials. In this review, we examine the multiple facets and most recent advances of this interesting disease.

Innate lymphoid cells in kidney diseases

It is well known that innate immune cells, including dendritic cells, macrophages, and natural killer cells, contribute to pathogenesis and protection in various kidney diseases. The understanding of innate immunity has been advanced recently by the discovery of a new group of innate lymphoid cells (ILCs), including ILC1, ILC2, and ILC3. ILCs lack adaptive antigen receptors, yet can be triggered by various pathogens and rapidly provide an abundant source of immunomodulatory cytokines to exert immediate immune reactions and direct subsequent innate and adaptive immune responses. ILCs play critical roles in immunity, tissue homeostasis, and pathological inflammation. In this review, we highlight the biological function of ILC subpopulations in the normal kidney, and their important roles in acute and chronic kidney diseases, thus demonstrating the emerging importance of ILC-regulated immunity in this special organ and providing insights for future research directions and therapeutic interventions.

Upregulation of microRNA‑140‑3p mediates dachshund family transcription factor 1 expression in immunoglobulin A nephropathy through cell cycle‑dependent mechanisms

Immunoglobulin A nephropathy (IgAN) is a kidney disease and one of the commonest forms of glomerulonephritis worldwide. The present study investigated the role of dachshund family transcription factor 1 (DACH1) in IgAN and identified one of its binding microRNAs (miRNAs). The expression of DACH1 in human mesangial cells (HMCs) incubated with polymeric IgA (pIgA) isolated and purified from the serum of patients with IgAN or healthy individuals was evaluated by reverse transcription-quantitative (RT-q) PCR and western blotting. Cell proliferation and cell cycle assays were performed in DACH1-overexpressing HMCs to identify the role of DACH1 in IgAN and enzyme-linked immunosorbent assay was carried out to verify the release of inflammatory factors from HMCs. The target miRNAs of DACH1 were predicted using bioinformatics software and miR-140-3p was identified as a target of DACH1 by luciferase report assay, RT-qPCR and western blotting. The results demonstrated that DACH1 was downregulated in HMCs cultured with pIgA-IgAN at both mRNA and protein levels. Overexpression of DACH1 suppressed HMC growth and inhibited inflammatory cytokine release from HMCs cultured with pIgA-IgAN. The expression of DACH1 was negatively regulated by miR-140-3p in IgAN and miR-140-3p inhibition suppressed HMC growth and inhibited inflammatory cytokine release from HMCs cultured with pIgA-IgAN. The findings of the present study demonstrated that DACH1 decreased HMC growth and the release of inflammatory cytokines from HMCs may be targeted by miR-140-3p. The results suggested that DACH1 could be associated with the progression of IgAN and provide a potential target for further studies related to the mechanism of IgAN.

Perspectives on how mucosal immune responses, infections and gut microbiome shape IgA nephropathy and future therapies

Infections have been considered to play a critical role in the pathogenesis of IgA nephropathy (IgAN) because synpharyngitic hematuria is a common feature in IgAN. However, how infections participate in this process is still debated. More recent studies have also revealed that the alteration of the gut microbiome exerts a profound effect on host immune responses, contributing to the etiology or progression of autoimmunity. Considering IgA as the first line of defense against bacterial and viral antigens, this review evaluates the relationships among intestinal infections, gut microbiome, and IgA for a better understanding of the pathogenesis of IgAN. Moreover, as a prototype of IgA immunity, we provide detailed clarification of IgAN pathogenesis to shed light on other diseases in which IgA plays a role. Finally, we discuss potential therapies focusing on microbes and mucosal immune responses in IgAN.

High-throughput sequencing analysis of genes encoding the B-lymphocyte receptor heavy-chain CDR3 in renal and peripheral blood of IgA nephropathy

Aim: IgA nephropathy (IgAN) is one of the most common chronic glomerulonephritis. Its etiology and pathogenesis remain unclear. We thus explored the immune repertoire of the B-cell receptor (BCR) and the heavy-chain complementarity-determining region 3 (CDR3) in renal tissue and peripheral blood of IgAN patients. Method: Total RNAs extracted from renal tissues and peripheral blood of patients and peripheral blood of healthy controls (HCs) were analyzed via high-throughput multiplex PCR sequencing. We amplified and sequenced BCR heavy-chain CDR3 regions to explore repertoire diversity, V/J gene family distribution, CDR3 lengths, BCR heavy-chain variants, consistency between tissue and peripheral blood data, and clones ‘shared’ by these bodily compartments. Results: We identified the renal tissue and peripheral blood BCR heavy-chain CDR3 immune repertoires of 15 IgAN patients. Top1 could be more readily cloned from peripheral blood of patients than from controls (P<0.05), the average CDR3 length was significantly shorter in patients than in HCs (P<0.05), the variant frequency of the gene encoding the BCR heavy chain was higher in patients than in HCs (P<0.05), and the BCR variant frequency was highest in IgAN kidney tissue. Preliminary screening for ‘shared’ clones showed that, in at least 13 patients, the ‘ALYFHNSAY’, ‘ARWGPMYYYMDV’, ‘ARDQGALNA’, and ‘ARVDNPADF’ CDR3 sequences were evident in peripheral blood samples from patients, but not HCs. Conclusions: We found that the ‘ALYFHNSAY’, ‘ARWGPMYYYMDV’, ‘ARDQGALNA’, and ‘ARVDNPADF’ clonal sequences may be useful for noninvasive diagnosis and treatment planning in IgAN.

A Personalized Update on IgA Nephropathy: A New Vision and New Future Challenges

IgA nephropathy (IgAN) is the most common primary glomerulonephritis in the world among patients undergoing renal biopsy. Approximately 30% of patients with IgAN develop end-stage kidney disease 20 years after renal biopsy. It is a glomerulopathy with a very broad clinical presentation, making it difficult to stratify and treat. IgAN is characterized by dysregulation of the immune system, which causes an abnormal synthesis of IgA1 that is deglycosylated causing its mesangial deposition. IgAN pathogenesis is incompletely understood; the current multi-hit hypothesis of IgAN pathogenesis does not explain the range of glomerular inflammation and renal injury associated with mesangial IgA deposition. Although associations between IgAN and glomerular and circulating markers of complement activation are established, the mechanism of complement activation and contribution to glomerular inflammation and injury are not defined. On the other hand, the renal-gut connection can also play an important role in the pathogenesis of IgAN with possible therapeutic implications. In order to standardize the histological findings, the Oxford Classification has allowed clarifying renal lesions that confer potential risk of progression. Currently, except for the blockade of the renin-angiotensin-aldosterone system, no other therapies are available in clinical setting for the treatment of IgAN, although the range of new drugs under investigation is extensive. The incorporation in the next trials of clinical parameters such as the amount of hematuria and histological lesions may allow more personalized therapeutic approaches. To summarize, in recent years, several important efforts have taken place in the understanding of IgAN, but still, further studies are warranted to elucidate the best therapeutic strategies according to the risk to improve the prognosis of this entity.

Recurrence of immunoglobulin A nephropathy after kidney transplantation: a narrative review of the incidence, risk factors, pathophysiology and management of immunosuppressive therapy

Glomerulonephritis (GN) is the underlying cause of end-stage renal failure in 30–50% of kidney transplant recipients. It represents the primary cause of end-stage renal disease for 25% of the dialysis population and 45% of the transplant population. For patients with GN requiring renal replacement therapy, kidney transplantation is associated with superior outcomes compared with dialysis. Recurrent GN was previously considered to be a minor contributor to graft loss, but with the prolongation of graft survival, the effect of recurrent disease on graft outcome assumes increasing importance. Thus the extent of recurrence of original kidney disease after kidney transplantation has been underestimated for several reasons. This review aims to provide updated knowledge on one particular recurrent renal disease after kidney transplantation, immunoglobulin A nephropathy (IgAN). IgAN is one of the most common GNs worldwide. The pathogenesis of IgAN is complex and remains incompletely understood. Evidence to date is most supportive of a several hit hypothesis. Biopsy is mandatory not only to diagnose the disease in the native kidney, but also to identify and characterize graft recurrence of IgAN in the kidney graft. The optimal therapy for IgAN recurrence in the renal graft is unknown. Supportive therapy aiming to reduce proteinuria and control hypertension is the mainstream, with corticosteroids and immunosuppressive treatment tailored for certain subgroups of patients experiencing a rapidly progressive course of the disease with active lesions on renal biopsy and considering safety issues related to infectious complications.

Improving treatment decisions using personalized risk assessment from the International IgA Nephropathy Prediction Tool

Immunosuppression in IgA nephropathy (IgAN) should be reserved for patients at high-risk of disease progression, which KDIGO guidelines determine based solely on proteinuria 1g or more/day. To investigate if treatment decisions can be more accurately accomplished using individualized risk from the International IgAN Prediction Tool, we simulated allocation of a hypothetical immunosuppression therapy in an international cohort of adults with IgAN. Two decision rules for treatment were applied based on proteinuria of 1g or more/day or predicted risk from the Prediction Tool above a threshold probability. An appropriate decision was defined as immunosuppression allocated to patients experiencing the primary outcome (50% decline in eGFR or ESKD) and withheld otherwise. The net benefit and net reduction in treatment are the proportion of patients appropriately allocated to receive or withhold immunosuppression, adjusted for the harm from inappropriate decisions, calculated for all threshold probabilities from 0-100%. Of 3299 patients followed for 5.1 years, 522 (15.8%) experienced the primary outcome. Treatment allocation based solely on proteinuria of 1g or more/day had a negative net benefit (was harmful) because immunosuppression was increasingly allocated to patients without progressive disease. Compared to using proteinuria, treatment allocation using the Prediction Tool had a larger net benefit up to 23.4% (95% confidence interval 21.5-25.2%) and a larger net reduction in treatment up to 35.1% (32.3-37.8%). Thus, allocation of immunosuppression to high-risk patients with IgAN can be substantially improved using the Prediction Tool compared to using proteinuria.

Long noncoding RNA Mirt2 prohibits lipopolysaccharide-evoked HK-2 cell injury via modulation of microRNA-126

Long noncoding RNA myocardial infarction-associated transcript 2 (lncRNA Mirt2) is a burgeoning lncRNA, its anti-inflammatory capacity has been testified. Nonetheless, the functions of Mirt2 in immunoglobulin A nephropathy are unexplored. We tried to impart the influences of Mirt2 in lipopolysaccharide (LPS)-evoked HK-2 cells damage. HK-2 cells were manipulated with 10 ng/ml LPS, next cell viability, apoptosis, reactive oxygen species (ROS) generation, pro-inflammatory factors and Mirt2 expression were evaluated. After pc-Mirt2 vector transfection, the aforementioned trials were performed. Meanwhile, real-time quantitative polymerase chain reaction (PCR) experiment was used to detect miR-126 expression. Subsequently, functions of miR-126 in LPS-treated HK-2 cells were further delved after transfection with miR-126 mimic. Western blot was used to evaluate NF-κB pathway. The data showed that LPS invoked HK-2 cells inflammatory damage via the suppression of cell viability and the acceleration of apoptosis, ROS level, and IL-1β and IL-6 secretion. LPS inhibited Mirt2 expression and overexpression of Mirt2 mitigated LPS-caused inflammatory damage in HK-2 cells. Additionally, overexpression of Mirt2 repressed miR-126 expression in LPS-stimulated cells. Meanwhile the anti-inflammatory effect of Mirt2 was inverted by upregulating miR-126 expression. Besides, overexpressed Mirt2 retarded LPS-activated NF-κB pathway via repressing miR-126. The research certified the anti-inflammatory impacts of Mirt2 on LPS-impaired HK-2 cells.

Immunological Pattern in IgA Nephropathy

The current gold-standard diagnostic technique for IgA nephropathy (IgAN), the leading form of primary glomerulonephritis, is renal biopsy. CD89 (the main IgA receptor) is expressed on the surface of monocytes and plays a role in disease pathogenesis. Immunocomplexes formed by sCD89 (soluble form) and Gd-IgA1 are related to disease prognosis. We hypothesize that reduced CD89 surface expression on monocytes may be a marker of disease severity. We aimed to analyze leukocyte subpopulations in peripheral blood and CD89 surface expression on monocytes in a prospective study of 22 patients and 12 healthy subjects (HS). Leukocyte subpopulations and CD89 expression were analyzed by flow cytometry. IgAN patients had a higher percentage of activated and effector memory CD4⁺ and CD8⁺ T lymphocytes, a lower percentage of transitional B lymphocytes and plasmablasts, and a higher percentage of CD56^dimCD16⁺ NK cells and myeloid dendritic cells compared with HS. Correlations between reduced CD89 expression levels on nonclassical monocytes, histological findings of a poor prognosis on renal biopsy and baseline renal function were observed. IgAN patients show a characteristic immunological pattern in peripheral blood. A reduced expression level of CD89 on nonclassical monocytes identifies patients with a worse renal prognosis.

Management and treatment of glomerular diseases (part 1): conclusions from a kidney disease: improving global outcomes (KDIGO) controversies conference

The Kidney Disease: Improving Global Outcomes (KDIGO) initiative organized a Controversies Conference on glomerular diseases in November 2017. The conference focused on the 2012 KDIGO guideline with the aim of identifying new insights into nomenclature, pathogenesis, diagnostic work-up, and, in particular, therapy of glomerular diseases since the guideline’s publication. It was the consensus of the group that most guideline recommendations, in particular those dealing with therapy, will need to be revisited by the guideline-updating Work Group. This report covers general management of glomerular disease, IgA nephropathy, and membranous nephropathy.

Management and treatment of glomerular diseases (part 1): conclusions from a Kidney Disease: Improving Global Outcomes (KDIGO) Controversies Conference

The Kidney Disease: Improving Global Outcomes (KDIGO) initiative organized a Controversies Conference on glomerular diseases in November 2017. The conference focused on the 2012 KDIGO guideline with the aim of identifying new insights into nomenclature, pathogenesis, diagnostic work-up, and, in particular, therapy of glomerular diseases since the guideline's publication. It was the consensus of the group that most guideline recommendations, in particular those dealing with therapy, will need to be revisited by the guideline-updating Work Group. This report covers general management of glomerular disease, IgA nephropathy, and membranous nephropathy.

Mesangial C4d deposition at diagnosis in childhood immunoglobulin A nephropathy

BACKGROUND

Immunoglobulin A nephropathy (IgAN) is a major cause of end-stage renal disease. Complement activation via the lectin pathway influences outcomes in IgAN. We examined the association of glomerular C4d deposition with clinicopathological severity at diagnosis and the disappearance of proteinuria in Japanese pediatric IgAN patients.

METHODS

We retrospectively analyzed 25 children newly diagnosed with IgAN at Hokkaido University Hospital. We evaluated glomerular C4d immunofluorescent staining at diagnosis. We compared clinical findings, pathological findings (based on Oxford classification), and the disappearance of proteinuria within 24 months after renal biopsy between C4d-positive and C4d-negative patients.

RESULTS

Glomerular C4d staining was observed in 14 patients (56.0%). C4d-positive patients had significantly higher proteinuria at diagnosis than C4d-negative patients (2.03 g/gCr vs 0.78 g/gCr; P = 0.005). The number of glomeruli with segmental glomerulosclerosis or adhesion (8.0% vs 0.0%; P = 0.046) and the extent of tubular atrophy/interstitial fibrosis (9.46% vs 2.86%; P = 0.031) were significantly increased in C4d-positive patients compared with C4d-negative patients. Further, the proportion of patients with modified T1 (>10%) was significantly higher in the C4d-positive group than the C4d-negative group. There was no significant difference, however, in the disappearance rate of proteinuria at 24 months after renal biopsy between groups (64% vs 82%; P = 0.149).

CONCLUSIONS

Glomerular C4d deposition was associated with clinicopathological severity at diagnosis in Japanese pediatric patients with IgAN. Glomerular C4d deposition, however, was not a predictor of the disappearance of proteinuria within 24 months after diagnosis in Japanese pediatric patients with IgAN.

Efficacy and safety of leflunomide in IgA nephropathy: a systematic review and meta-analysis

BACKGROUND

The optimal therapy for immunoglobulin A nephropathy (IgAN) remains uncertain. Leflunomide (LEF) is an immunosuppressive drug which may reduce deposition of glomerular autoantibodies and immune complexes. Several clinical trials were designed to evaluate the efficacy of LEF, but their results were controversial.

METHODS

Ovid Medline, Embase, the Cochrane Library, PubMed, and CNKI were systematically searched. Search terms included ("glomerulonephritis" OR "nephritis") AND ("immunoglobulin A" OR "IgA") AND "leflunomide". Studies in which patients were diagnosed with IgAN based on renal biopsy were included. Studies needed to report clinical outcomes via either short- or long-term clinical examination, remission rate, or complication rate.

RESULTS

Forty-four studies encompassing 1802 patients were included, of which 35 were randomized controlled trials. Results of 24 h post-treatment urine protein tests and serum creatinine tests were significantly lower in patients treat with LEF and corticosteroids (CS) or valsartan (ACEI) (CS + LEF or CS + ACEI) compared with patients treated with CS or ACEI alone (P < 0.05). More patients treated with CS + LEF (31.2%) achieved complete remission (CR) than patients treated with CS alone (22.2%) (RR = 0.71, 95% CI 0.59-0.85, P < 0.05). Although there was no significant difference in CR between patients treated with cyclophosphamide and CS (CS + CTX) and those treated with CS + LEF, the complication rate in the former group was higher (28.4%) than in the latter one (11.4%) (RR = 2.46, 95% CI 1.47-4.13, P < 0.005).

CONCLUSION

LEF appears to improve renal function while decreasing loss of urine protein. Combination regimens including LEF were better and safer compared with CS or ACEI alone or combinations including CTX.

Noninvasive Urinary Monitoring of Progression in IgA Nephropathy

Standard methods for detecting and monitoring of IgA nephropathy (IgAN) have conventionally required kidney biopsies or suffer from poor sensitivity and specificity. The Kidney Injury Test (KIT) Assay of urinary biomarkers has previously been shown to distinguish between various kidney pathologies, including chronic kidney disease, nephrolithiasis, and transplant rejection. This validation study uses the KIT Assay to investigate the clinical utility of the non-invasive detection of IgAN and predicting the progression of renal damage over time. The study design benefits from longitudinally collected urine samples from an investigator-initiated, multicenter, prospective study, evaluating the efficacy of corticosteroids versus Rituximab for preventing progressive IgAN. A total of 131 urine samples were processed for this study; 64 urine samples were collected from 34 IgAN patients, and urine samples from 64 demographically matched healthy controls were also collected; multiple urinary biomarkers consisting of cell-free DNA, methylated cell-free DNA, DMAIMO, MAMIMO, total protein, clusterin, creatinine, and CXCL10 were measured by the microwell-based KIT Assay. An IgA risk score (KIT-IgA) was significantly higher in IgAN patients as compared to healthy control (87.76 vs. 14.03, p < 0.0001) and performed better than proteinuria in discriminating between the two groups. The KIT Assay biomarkers, measured on a spot random urine sample at study entry could distinguish patients likely to have progressive renal dysfunction a year later. These data support the pursuit of larger prospective studies to evaluate the predictive performance of the KIT-IgA score in both screening for non-invasive diagnosis of IgAN, and for predicting risk of progressive renal disease from IgA and utilizing the KIT score for potentially evaluating the efficacy of IgAN-targeted therapies.

The role of complement in IgA nephropathy

IgA nephropathy (IgAN) is common and often progresses to end stage renal disease. IgAN encompasses a wide range of histology and clinical features. IgAN pathogenesis is incompletely understood; the current multi-hit hypothesis of IgAN pathogenesis does not explain the range of glomerular inflammation and renal injury associated with mesangial IgA deposition. Although associations between IgAN and glomerular and circulating markers of complement activation are established, the mechanism of complement activation and contribution to glomerular inflammation and injury are not defined. Recent identification of specific complement pathways and proteins in severe IgAN cases had advanced our understanding of complement in IgAN pathogenesis. In particular, a growing body of evidence implicates the complement factor H related proteins 1 and 5 and lectin pathway as pathogenic in a subset of patients with severe disease. These data suggest complement deregulation and activity may be dominant drivers of renal injury in IgAN. Thereby, markers of complement activation may identify IgAN patients likely to progress to significant renal impairment and complement inhibition may emerge as an effective method of preventing and reducing glomerular injury in IgAN.

Mesangial Deposition Can Strongly Involve Innate-Like IgA Molecules Lacking Affinity Maturation

BACKGROUND

IgA nephropathy (IgAN) often follows infections and features IgA mesangial deposition. Polymeric IgA deposits in the mesangium seem to have varied pathogenic potential, but understanding their pathogenicity remains a challenge. Most mesangial IgA1 in human IgAN has a hypogalactosylated hinge region, but it is unclear whether this is required for IgA deposition. Another important question is the role of adaptive IgA responses and high-affinity mature IgA antibodies and whether low-affinity IgA produced by innate-like B cells might also yield mesangial deposits.

METHODS

To explore the effects of specific qualitative variations in IgA and whether altered affinity maturation can influence IgA mesangial deposition and activate complement, we used several transgenic human IgA1-producing models with IgA deposition, including one lacking the DNA-editing enzyme activation-induced cytidine deaminase (AID), which is required in affinity maturation. Also, to explore the potential role of the IgA receptor CD89 in glomerular inflammation, we used a model that expresses CD89 in a pattern observed in humans.

RESULTS

We found that human IgA induced glomerular damage independent of CD89. When comparing mice able to produce high-affinity IgA antibodies with mice lacking AID-enabled Ig affinity maturation, we found that IgA deposition and complement activation significantly increased and led to IgAN pathogenesis, although without significant proteinuria or hematuria. We also observed that hinge hypoglycosylation was not mandatory for IgA deposition.

CONCLUSIONS

In a mouse model of IgAN, compared with high-affinity IgA, low-affinity innate-like IgA, formed in the absence of normal antigen-driven maturation, was more readily involved in IgA glomerular deposition with pathogenic effects.

Complement factor H gene polymorphism rs6677604 and the risk, severity and progression of IgA nephropathy: A systematic review and meta-analysis

AIM

Studies reporting the association between complement factor H gene rs6677604 polymorphism and susceptibility to IgA nephropathy (IgAN) had yielded inconsistent results. We performed a systematic review and meta-analysis to clarify the association between rs6677604 and IgAN susceptibility, disease severity and chronic progression.

METHODS

A comprehensive database search was performed to identify eligible studies. Meta-analyses were performed for rs6677604 allele frequency, genotypes and the association with IgAN susceptibility.

RESULTS

10 studies were included in the systematic review. Among them, four studies containing 10 distinct datasets (15,617 cases and 31,957 controls) were included in the meta-analysis. The pooled frequency of the minor allele (A) was significantly higher in Europeans than in Asians across both IgAN cases and controls, and the frequency of the minor allele (A) in IgAN cases was also significantly lower than that in controls across both European and Asian subgroups. Significant associations were detected between rs6677604 and risk of developing IgAN, when comparing allele A vs. G, genotype AA vs. GG, genotype AA vs. AG and genotype AG vs. GG. In analysis stratified by ethnicity, significant association was only observed in Europeans but not in Asians when comparing AA vs. GG or AA vs. AG.

CONCLUSION

Our pooled analysis showed a significant association between rs6677604-(A) allele and IgAN susceptibility, supporting the importance of complement activation in the pathogenesis of IgAN. The presence of rs6677604-(A) allele may be associated with a decreased the risk of IgAN in Europeans, but the association was not confirmed in Asians.

A Proliferation Inducing Ligand (APRIL) targeted antibody is a safe and effective treatment of murine IgA nephropathy

IgA nephropathy (IgAN) is the most prevalent primary chronic glomerular disease for which no safe disease-specific therapies currently exist. IgAN is an autoimmune disease involving the production of autoantigenic, aberrantly O-glycosylated IgA1 and ensuing deposition of nephritogenic immune complexes in the kidney. A Proliferation Inducing Ligand (APRIL) has emerged as a key B-cell-modulating factor in this pathogenesis. Using a mouse anti-APRIL monoclonal antibody (4540), we confirm both the pathogenic role of APRIL in IgAN and the therapeutic efficacy of antibody-directed neutralization of APRIL in the grouped mouse ddY disease model. Treatment with 4540 directly translated to a reduction in relevant pathogenic mechanisms including suppressed serum IgA levels, reduced circulating immune complexes, significantly lower kidney deposits of IgA, IgG and C3, and suppression of proteinuria compared to mice receiving vehicle or isotype control antibodies. Furthermore, we translated these findings to the pharmacological characterization of VIS649, a highly potent, humanized IgG2κ antibody targeting and neutralizing human APRIL through unique epitope engagement, leading to inhibition of APRIL-mediated B-cell activities. VIS649 treatment of non-human primates showed dose-dependent reduction of serum IgA levels of up to 70%. A reduction of IgA⁺, IgM⁺, and IgG⁺ B cells was noted in the gut-associated mucosa of VIS649-treated animals. Population-based modeling predicted a favorable therapeutic dosing profile for subcutaneous administration of VIS649 in the clinical setting. Thus, our data highlight the potential therapeutic benefit of VIS649 for the treatment of IgAN.

Alteration of glycosylation in serum proteins: a new potential indicator to distinguish non-diabetic renal diseases from diabetic nephropathy

Diabetic nephropathy (DN) and nondiabetic renal disease (NDRD) are two major categories of renal diseases in diabetes mellitus patients. The clinical differentiation among them is usually not so clear and effective. In this study, sera from DN and NDRD patients were collected, and glycan profiles of serum proteins from DN and NDRD patients were investigated and compared by using lectin microarray and lectin blot. Then, altered glycoproteins were enriched by lectin coupled magnetic particle conjugate and characterized by LC-MS/MS. We found significant change in glycan patterns between DN and NDRD patients. In particular, the relative abundance of the glycopattern of Galβ1-3GalNAc which was identified by BPL (Bauhinia purpurea lectin) was significantly decreased in DN patients compared to four types of NDRD patients (p < 0.05). Moreover, BPL blotting indicated that the proteins with a molecular weight of about 53 kDa exhibited low staining signal in DN compared to all NDRD groups, which was consistent with results of lectin microarrays. After enriching by BPL and identification by LC-MS/MS, a total of 235 and 258 proteins were characterized from NDRD and DN respectively. Among these, the relative abundance of 12 isolated serum proteins exhibited significantly alteration between DN and NDRD (p < 0.05). Our findings indicated not only the relative abundance of Galβ1-3GalNAc on serum proteins but also certain glycoproteins modified with this glycopattern showed a difference between DN and NDRD patients. This suggested that the analysis of this alteration by using urine specimens may constitute an additional valuable diagnostic tool for differentiating DN and NDRD with a non-invasive method.

Value of urinary levels of interleukin-6, epidermal growth factor, monocyte chemoattractant protein type1 and transforming growth factor β1 in predicting the extent of fibrosis lesions in kidney biopsies of patients with IgA nephropathy

OBJECTIVE

To analyse the associations between urinary levels of IL-6 EGF, MCP-1 and TGFβ1 and clinical, biochemical and histopathological characteristics in patients with primary IgA nephropathy and their ability to predict the extent of lesions of glomerular and/or interstitial sclerosis.

PATIENTS AND METHODS

A total of 58 patients with IgA nephropathy were studied. We determined the urine levels of IL-6, EGF, MCP-1, and TGFβ1 at the time of diagnosis. The extent of glomerular and interstitial fibrosis was analyzed by quantitative morphometry and kidney biopsies were classified according to the Oxford criteria. We analysed the ability of these molecules to predict the extent of glomerular and interstitial fibrosis lesions.

RESULTS

IL-6, TGFβ1 and MCP-1 were associated with focal glomerulosclerosis and interstitial fibrosis extension but not with the presence of mesangial, extracapillary or endocapillary proliferation. EGF showed a negative association with interstitial fibrosis. By categorising patients according to the Oxford classification, patients with T1 and T2 scores had significantly higher levels of IL-6, MCP-1, TGF-β1 and significantly lower levels of EGF than patients with T0 scores. By multiple regression and logistic regression analyses, the levels of MCP-1, IL-6 and EGF were independent predictors of the fibrosis surface, after adjusting for age and eGFR.

CONCLUSION

The urinary concentration of IL-6, EGF and MCP-1 provides additional information that significantly improves the estimation of the surface of interstitial fibrosis in patients with IgA nephropathy.

Effects of Periostracum Cicadae on Cytokines and Apoptosis Regulatory Proteins in an IgA Nephropathy Rat Model

Periostracum cicadae, the cast-off shell of the cicada Cryptotympana pustulata Fabricius, is used in traditional Chinese medicine for its diaphoretic, anticonvulsive, sedative, antipyretic, and antiallergic effects. However, the exact pathogenesis of immunoglobulin A nephropathy (IgAN) remains unclear, thereby hindering investigations to identify novel therapeutic agents. A rat IgAN model was established by administration of bovine serum albumin, lipopolysaccharide, and carbon tetrachloride, which simultaneously established blood stasis and a heat syndrome model. The animals were sacrificed to detect changes in protein levels in urine and blood. Immunofluorescence was performed to assess IgA deposition in the glomeruli. Tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and interleukin 6 (IL-6) levels were measured in bronchoalveolar lavage fluid (BALF) by enzyme-linked immunosorbent assay. Hematology and eosin, periodic acid-Schiff, TUNEL (TdT-mediated dUTP Nick-End Labeling), and immunohistochemical staining were performed to evaluate histopathological changes in kidney tissues. Additionally, target-related proteins were measured by Western blotting. Periostracum cicadae resulted in a reduction in blood and urine protein levels. Serum TNF-α, IL-1β, and IL-6 levels significantly decreased in the periostracum cicadae-treated groups compared to the IgAN group. Furthermore, a reduction in MCP-1 (Monocyte Chemotactic Protein-1), TLR4 ((Toll-Like Receptor 4)), and IgA expression levels and a dose-dependent increase in caspase 3 expression were observed in response to periostracum cicadae treatment. TGF-β1(Transforming Growth Factor-β) levels decreased, whereas that of Fas increased in the kidney tissues of the periostracum cicadae-treated groups. The findings of the present study indicate that periostracum cicadae induces apoptosis and improves kidney inflammation and fibrosis in IgA nephropathy rat models.

Early post-transplant serum IgA level is associated with IgA nephropathy recurrence after kidney transplantation

IgA nephropathy (IgAN), the most frequent primary glomerulonephritis, affects young patients and is associated with a high risk of progression to end-stage renal disease. Consequently, patients with IgAN constitute an important proportion of candidates for kidney transplantation. Several studies showed a significant risk of IgAN recurrence on kidney graft, but the risks factors for recurrence remain to be accurately evaluated. Indeed, early identification of at risk patients may allow the optimization of treatment and the reduction of recurrence rate on the graft. In the present work, we studied the relationship between post-transplant serum IgA (sIgA) levels and the risk of IgAN recurrence after kidney transplantation. Recipients with IgAN had higher levels of sIgA as compared to patients with other nephropathies (p<0.05). The prevalence of IgAN recurrence was 20.8% during the period of analysis (mean follow-up of 6 ± 3.2 years). Serum IgA levels at M6, M12 and M24 post-transplant were significantly higher in patients with IgAN recurrence as compared to those without (p = 0.009, p = 0.035 and p = 0.029, respectively). Using receiver operating curve (ROC), sIgA at M6 and M12 post-transplant were significantly associated with IgAN recurrence (AUC = 0.771, p = 0.004 and AUC = 0.767, p = 0.016, respectively), while serum creatinine and proteinuria were not. Serum IgA level at month 6 was significantly associated with the occurrence of post-transplant IgA recurrence, whether it was analyzed as a continuous or a categorical variable. After successive adjustment on age, gender and proteinuria, sIgA remained a significant risk factor of post-transplant IgAN recurrence. Finally, survival free of IgAN recurrence was significantly better in patients with sIgA<222 mg/dL at month 6 as compare to IgAN patients with sIgA≥222 mg/dL (p = 0.03). Thus, the present work supports a link between post-transplant sIgA levels and IgAN recurrence and suggests that sIgA may be a valuable predictive biomarker of IgAN recurrence in kidney transplant recipients.

Integrated analysis of B‑cell and T‑cell receptors by high‑throughput sequencing reveals conserved repertoires in IgA nephropathy

Immunoglobulin A nephropathy (IgAN) is a type of glomerular disorder associated with immune dysregulation, and understanding B‑/T‑cell receptors (BCRs/TCRs) may be valuable for the development of specific immunotherapeutic interventions. In the present study, B and T cells were isolated from IgAN patients and healthy controls, and the composition of the BCR/TCR complementarity‑determining region (CDR)3 was analyzed by multiplex polymerase chain reaction, high‑throughput sequencing and bioinformatics. The present results revealed that the BCR/TCR CDR3 clones were expressed at very low frequencies, and the composition of clone types in patients with IgAN was skewed; the majority of clones were unique, and only 12 BCR and 228 TCR CDR3 clones were public ones, of which 16 were expressed at a significantly higher frequency in patients with IgAN (P<0.001). There were also certain conserved amino acid residues between unique clones or groups, and the residues GMDV, EQY and EQF were recurring only in the IgAN group. In addition, some VDJ gene recombinations indicated great variation between groups, including 4 high‑frequency VDJ gene recombinations in the IgAN patients (P<0.001). Immune repertoires provide novel information, and conserved BCR/TCR CDR3 clones and VDJ gene recombinations with great variation may be potential therapeutic targets for IgAN patients.

Bortezomib for Reduction of Proteinuria in IgA Nephropathy

Introduction

IgA nephropathy is the most common glomerulonephritis in the world. We conducted a pilot trial (NCT01103778) to test the effect of bortezomib in patients with IgA nephropathy and significant proteinuria.

Methods

We treated 8 consecutive subjects from July 2011 until March 2016 with 4 doses of bortezomib. All subjects had biopsy-proven IgA nephropathy and proteinuria of greater than 1 g per day. They were given 4 doses of bortezomib i.v. at 1.3 mg/m² of body surface area per dose. Changes in proteinuria and renal function were followed for 1 year after enrollment. The primary endpoint was full remission defined as proteinuria of less than 300 mg per day.

Results

All 8 subjects received and tolerated 4 doses of bortezomib over a 2-week period during enrollment. The median baseline daily proteinuria was 2.46 g (interquartile range: 2.29–3.16 g). At 1-year follow-up, 3 subjects (38%) had achieved the primary endpoint. The 3 subjects who had complete remission had Oxford classification T scores of 0 before enrollment. Of the remaining 5 subjects, 1 was lost to follow-up within 1 month of enrollment and 4 (50%) did not have any response or had progression of disease.

Conclusion

Proteasome inhibition by bortezomib may reduce significant proteinuria in select cases of IgA nephropathy. Subjects who responded to bortezomib had Oxford classification T score of 0 and normal renal function.

Inhibition of STAT3 Signaling Reduces IgA1 Autoantigen Production in IgA Nephropathy

Introduction

IgA nephropathy is a chronic renal disease characterized by mesangial immunodeposits that contain autoantigen, which is aberrantly glycosylated IgA1 with some hinge-region O-glycans deficient in galactose. Macroscopic hematuria during an upper respiratory tract infection is common among patients with IgA nephropathy, which suggests a connection between inflammation and disease activity. Interleukin-6 (IL-6) is an inflammatory cytokine involved in IgA immune response. We previously showed that IL-6 selectively increases production of galactose-deficient IgA1 in IgA1-secreting cells from patients with IgA nephropathy.

Methods

We characterized IL-6 signaling pathways involved in the overproduction of galactose-deficient IgA1. To understand molecular mechanisms, IL-6 signaling was analyzed by kinomic activity profiling and Western blotting, followed by confirmation assays using siRNA knock-down and small-molecule inhibitors.

Results

STAT3 was differentially activated by IL-6 in IgA1-secreting cells from patients with IgA nephropathy compared with those from healthy control subjects. Specifically, IL-6 induced enhanced and prolonged phosphorylation of STAT3 in the cells from patients with IgA nephropathy, which resulted in overproduction of galactose-deficient IgA1. This IL-6−mediated overproduction of galactose-deficient IgA1 could be blocked by small molecule inhibitors of JAK/STAT signaling.

Discussion

Our results revealed that IL-6−induced aberrant activation of STAT3-mediated overproduction of galactose-deficient IgA1. STAT3 signaling pathway may thus represent a new target for disease-specific therapy of IgA nephropathy.

Remission of Hematuria Improves Renal Survival in IgA Nephropathy

Hematuria is a cardinal symptom in IgA nephropathy, but its influence on the risk of disease progression has been scarcely investigated. We followed a cohort of 112 patients with IgA nephropathy for a mean±SEM period of 14±10.2 years, during which clinical and analytic risk factors (including urine sediment examination) were regularly recorded. According to the magnitude of time-averaged hematuria, we classified patients as those with persistent hematuria and those with negative or minimal hematuria. We also classified patients according to the magnitude of time-averaged proteinuria (>0.75 or ≤0.75 g/d). The proportion of patients reaching ESRD or a 50% reduction of renal function was significantly greater among patients with persistent hematuria than patients with minimal or negative hematuria (30.4% and 37.0% versus 10.6% and 15.2%, respectively; P=0.01). Multivariable analysis revealed time-averaged hematuria, time-averaged proteinuria, renal function at baseline, and the presence of tubulointerstitial fibrosis on renal biopsy as independent predictors of ESRD. After hematuria disappearance, which occurred in 46% of the patients, the rate of renal function decline changed from -6.45±14.66 to -0.18±2.56 ml/min per 1.73 m² per year (P=0.001). Patients with time-averaged proteinuria >0.75 g/d had significantly poorer renal survival than those with time-averaged proteinuria ≤0.75 g/d. However, on further classification by time-averaged hematuria, only those patients with time-averaged proteinuria >0.75 g/d and persistent hematuria had significantly worse renal survival than those in the other three groups. In conclusion, remission of hematuria may have a significant favorable effect on IgA nephropathy outcomes.

Henoch-Schönlein Purpura Nephritis in Children: Prognosis and Treatment Experiences

Henoch-Schönlein purpura is a type of systemic small vessel vasculitis. The dominant manifestation is the cutaneous component, the illness is self-limiting in nature, and the prognosis and outcome depend mostly on renal manifestations. We analysed the associations among clinical and laboratory parameters with the prognosis and outcome of HSP in children hospitalised at the Paediatrics clinic, Clinical Centre, Kragujevac between January 2011 and January 2012. Children who developed nephritis were older on average and all manifested with arthritis, abdominal complaints, microhaematuria, elevated D-dimer levels in the serum, and significant proteinuria and microalbuminuria (≥ 300 mg/L), and two children had pre-existing allergic conditions. All three children with repeatedly positive proteins in the morning sample urine test had significant proteinuria (≥0,5 g/24 h) and microalbuminuria (≥ 300 mg/L). These children had more bursts of rash and more severe and lasting abdominal pain and arthritis compared to children with normal urine tests. They were therefore treated with glucocorticoids and an angiotensin-converting enzyme inhibitor. The glomerular filtration rate measured by determining creatinine clearance was normal in all patients. These patients were diagnosed with Henoch-Schönlein purpura nephritis, and their condition was regularly monitored. Analysis of this group of patients demonstrated that the average age of 8 years and abdominal complaints were indicative of nephritis development.. Because both of these parameters are easily noted at disease onset, we suggest careful monitoring of disease course in these children.

Study of the variables associated with local complement activation in IgA nephropathy

OBJECTIVES

1. To identify the variables that are associated with urinary levels of properdin, MBL, C4d, and C5b-9 in patients with idiopathic IgA nephropathy. 2. To analyse whether urinary levels of MBL and/or C4d are useful for identifying the presence of mesangial deposits of C4d/MBL.

PATIENTS AND METHOD

A total of 96 patients with IgA nephropathy were studied. Demographic, clinical and biochemical variables were recorded at the time of diagnosis. Renal lesions were quantified using the Oxford classification. Immunohistochemical staining for MBL, MASP-2, properdin, C4d, and C5b-9 was performed in kidney biopsies, and in urine, the levels of properdin, MBL, C4d and C5b-9 were determined.

RESULTS

In multivariate analysis, the independent predictors of C4d and MBL levels in urine were the mesangial deposits of each protein and, to a lesser extent, the urinary protein excretion. The independent predictors of urinary levels of C5b-9 were MBL properdin and proteinuria. Urinary excretion of C4d had a sensitivity of 90% (95% CI: 58,7 to 99) and a specificity of 73% (95% CI: 54-87) for detecting mesangial C4d deposits, and the level of MBL had a sensitivity of 83.9% (95% CI: 62-95) and a specificity of 81.6% (95% CI: 65-92) for identifying mesangial deposits of MBL.

CONCLUSION

The main predictor of urinary concentration of C4d and MBL was the presence of their respective mesangial deposits. Urine MBL may contribute to complement activation in the tubular luz through the lectin pathway. Urinary levels of MBL and C4d could be sensitive and specific biomarkers for the identification of patients with mesangial deposits of MBL and C4d.

Pregnancy and Kidney Outcomes in Patients With IgA Nephropathy: A Cohort Study

BACKGROUND

The outcomes of pregnancy in immunoglobulin A nephropathy (IgAN) are controversial. This cohort study assessed the effects of pregnancy on kidney disease progression and risk factors for adverse pregnancy outcomes in patients with IgAN.

STUDY DESIGN

A cohort study.

SETTING & PARTICIPANTS

Women of child-bearing age with IgAN and minimum follow-up of 1 year after biopsy from December 2003 to September 2014.

PREDICTORS

Pregnancy, treated as a time-dependent variable; baseline (at time of biopsy) estimated glomerular filtration rate (eGFR), proteinuria, blood pressure, and kidney pathology (Oxford MEST classification).

OUTCOMES

Kidney disease progression event, defined as 30% decline in eGFR or end-stage kidney disease; rate of eGFR decline; and adverse pregnancy outcomes, including severe preeclampsia and fetal loss.

RESULTS

Of 413 patients enrolled, 266 (64.4%), 101 (24.5%), 40 (9.6%), and 6 (1.5%) had chronic kidney disease (CKD) stages 1, 2, 3, and 4, respectively. During follow-up, 104 had 116 pregnancies, of which 110 continued beyond week 20; 309 patients did not become pregnant. After adjustment for age, eGFR, mean arterial pressure, proteinuria, and pathology class at the time of biopsy, subsequent pregnancy among patients with CKD stages 3 to 4, but not CKD stages 1 to 2, was associated with faster eGFR decline (-7.44 vs -3.90mL/min/1.73m² per year; P=0.007) and increased incidence of kidney progression events (HR, 5.14; 95% CI, 1.16-22.74) compared with patients who did not become pregnant.

LIMITATIONS

Relatively small sample size and single-center experience.

CONCLUSIONS

Pregnancy accelerated kidney disease progression in women with IgAN and CKD stage 3, but not in those at stage 1 or 2.

Rapamycin Enhances Repressed Autophagy and Attenuates Aggressive Progression in a Rat Model of IgA Nephropathy

BACKGROUND

IgA nephropathy (IgAN) has been considered to be the most frequent form of primary glomerulonephritis that occurs worldwide with a variety of factors involved in its occurrence and development. The impact of autophagy in IgAN, however, remains partially unclear. This study was designed to investigate the effects of rapamycin in an IgAN model.

METHOD

After establishing an IgAN rat model, SD rats were divided into 4 groups: control, control + rapamycin, IgAN, IgAN + rapamycin. Proteinuria and the pathological changes and the level of autophagy of kidney were texted. Identify the expression of phosphorylation and total mammalian target of rapamycin (mTOR) and s6k1 as well as cyclin D1 in the kidney of rats through Western blot and immunohistochemistry.

RESULTS

With rapamycin treatment, we observed a significant reduction in the progression of proteinuria as well as alleviation of pathological lesions in IgAN rats. Besides, autophagy was inhibited, while the mTOR/S6k1 pathway was activated and expression of cyclin D1 was increased in IgAN. Rapamycin treatment increased autophagy and decreased the expression of cyclin D1.

CONCLUSION

These results may suggest that mTOR-mediated autophagy inhibition may result in mesangial cell proliferation in IgAN.