Galactose-deficient IgA1 Levels Research Articles

Glomerulonephritis with severe nephrotic syndrome induced by immune complexes composed of galactose-deficient IgA1 in primary Sj\xf6gren\u2019s syndrome: a case report

BackgroundPrimary Sjögren’s syndrome (pSS) is an auto-immune disease characterized by sialadenitis and dacryoadenitis with lymphoplasmacytic cell infiltration. In pSS, not only sicca symptoms, but also extra-glandular involvement induced by immune abnormalities based on pSS occurs. Renal involvement is one such important life-threatening extra-glandular involvement. Although the aberrant glycosylated IgA in pSS as a product of over-activated B cells is a risk factor of renal involvement, its association has not been clarified. Here we report a case of glomerulonephritis (GN) induced by immune complexes (IC) composed of galactose-deficient IgA1 (Gd-IgA1) in a patient with pSS.Case presentationA 48-year-old Japanese woman with pSS was admitted to our hospital because of a two-month history of nephrotic syndrome. Seven years before she had been diagnosed with pSS from keratoconjunctivitis sicca, elevation of serum anti-Ro/SSA antibody titer and lymphoplasmacytic cell infiltration around salivary ducts of the small salivary glands. Renal biopsy revealed diffuse bubbling appearance in glomerular basement membrane (GBM) with scarce mesangial proliferation. Immunofluorescence showed granular IgA, C3 and Gd-IgA1 staining of GBM. Light chain staining showed no monoclonality. Electron microscopy showed electron dense deposits mainly in the intra-membranous and paramesangial areas and slightly in the subepithelial area. Additional serum analysis confirmed elevation of Gd-IgA1 (13.5 μg/mL), which was comparable with that seen in IgA nephropathy, and qualitative enzyme-linked immunosorbent assay of IgA-containing circulating immune complex (IgA-CIC) was positive. Thus, we diagnosed GN induced by IC composed of Gd-IgA1. Furthermore, retrospectively performed immunofluorescence of the small salivary gland evaluated at the diagnosis of pSS showed positive Gd-IgA1 staining of infiltrating lymphoplasmacytic cells. Therefore, we concluded that Gd-IgA1 produced by over-activated B cells in pSS formed circulating IC and thereby induced GN. After induction therapy with high dose prednisolone and mycophenolate mofetil, the nephrotic syndrome remitted within 3 weeks, the serum Gd-IgA1 level decreased to the normal range (3.8 μg/mL), and serum IgA-CIC disappeared in the 6th month after induction therapy.ConclusionsOur findings clearly demonstrate an association between aberrant glycosylated IgA and the renal involvement seen in pSS, thereby helping to clarify the renal significance of aberrant glycosylated IgA in pSS.

Interaction between GALNT12 and C1GALT1 Associates with Galactose-Deficient IgA1 and IgA Nephropathy.

Galactose-deficient IgA1 plays a key role in the pathogenesis of IgA nephropathy, the most common primary GN worldwide. Although serum levels of galactose-deficient IgA1 have a strong genetic component, the genetic link between this molecule and IgA nephropathy has not yet been clearly established. To identify novel loci associated with galactose-deficient IgA1, we performed a quantitative genome-wide association study for serum galactose-deficient IgA1 levels, on the basis of two different genome-wide association study panels conducted in 1127 patients with IgA nephropathy. To test genetic associations with susceptibility to IgA nephropathy, we also enrolled 2352 patients with biopsy-diagnosed IgA nephropathy and 2632 healthy controls. Peripheral blood samples from 59 patients and 27 healthy controls were also collected for gene expression analysis. We discovered two loci, in C1GALT1 and GALNT12, that achieved genome-wide significance, explaining about 3.7% and 3.4% of variance in serum galactose-deficient IgA1 levels, respectively. We confirmed the previously reported association of C1GALT1 with serum galactose-deficient IgA1 levels, but with a different lead single-nucleotide polymorphism (rs10238682; β=0.26, P=1.20×10-9); the locus we identified at GALNT12 (rs7856182; β=0.73, P=2.38×10-9) was novel. Of more interest, we found that GALNT12 exhibits genetic interactions with C1GALT1 in both galactose-deficient IgA1 levels (P=1.40×10-2) and disease risk (P=6.55×10-3). GALNT12 mRNA expression in patients with IgA nephropathy was significantly lower compared with healthy controls. Our data identify GALNT12 as a novel gene associated with galactose-deficient IgA1 and suggest novel genetic interactions. These findings support a key role of genetically conferred dysregulation of galactose-deficient IgA1 in the development of IgA nephropathy.

Immune characteristics of renal allograft donors with mesangial IgA deposition

BackgroundThere are few studies describing the prevalence and immune features of people with subclinical mesangial immunoglobulin A (IgA) deposition in the Chinese population. We sought to investigate the prevalence of mesangial IgA deposition among kidney donors and the immune characteristics of donors with mesangial IgA deposition. MethodsFifty blood-related living donors with zero-hour allograft biopsies obtained at Peking University First Hospital were enrolled. Galactose-deficient IgA1 (Gd-IgA1) in glomerular deposits was examined by double immunofluorescent staining using the specific monoclonal antibody KM55. Plasma IgA, IgA1, Gd-IgA1 and antibodies directed against Gd-IgA1 were measured using enzyme-linked immunosorbent assay. ResultsThirteen of 50 (26%) donors had mesangial IgA deposition, which was confirmed by both immunofluorescence and electron microscopy. The levels of plasma IgA, IgA1 and Gd-IgA1 were all increased in donors with IgA deposition compared with those without IgA deposition (mean ± SD, 3.54 ± 0.505 versus 2.356 ± 0.265 mg/ml, p = 0.049; 3.003 ± 0.4048 versus 2.356 ± 0.265 mg/ml, p = 0.057; and 4.719 ± 0.4357 versus 3.356 ± 0.4707 ug/ml, p = 0.0440, respectively). Colocalized IgA1 and Gd-IgA1 indicated that there were galactose-deficient IgA1 deposits in the glomerular mesangium. While donors with IgA deposition showed lower levels of IgG anti-glycan antibodies than patients with IgA nephropathy (37.71 ± 8.886 versus 78.86 ± 5.155 units/ml, p = 0.001). ConclusionsThe immune features of donors with IgA deposition, including IgA1 and Gd-IgA1 deposition, were similar to those of patients with IgA nephropathy, but donors with IgA deposition had lower levels of antiglycan antibodies, which may explain the subclinical status of IgA deposition in donors. Mesangial IgA deposition was common in the Chinese blood related donors cohort, further large study with both living and cadaveric donor kidneys was still needed to confirm these findings.

Clinical Relevance of Serum Galactose Deficient IgA1 in Patients with IgA Nephropathy.

New biomarkers of IgA nephropathy (IgAN) are needed for non-invasive diagnosis and appropriate treatment. There is emerging evidence that galactose deficient IgA1 (Gd-IgA1) is a pivotal molecule in the pathogenesis of IgAN. However, few studies have investigated the role of Gd-IgA1 as a biomarker in IgAN. In this study, we investigated the clinical relevance of serum Gd-IgA1 levels in patients with IgAN. Two hundred and thirty biopsy-proven IgAN patients, 74 disease controls (patients with non-IgAN nephropathy), and 15 healthy controls were enrolled in this study. Levels of serum Gd-IgA1 were measured using an ELISA kit in serum samples obtained the day of renal biopsy. We compared levels of serum Gd-IgA1 according to the type of glomerular disease and analyzed the association between Gd-IgA1 levels and clinical and pathological parameters in patients with IgAN. We then divided IgAN patients into two groups according to Gd-IgA1 level and investigated the predictive value of Gd-IgA1 for progression of chronic kidney disease (CKD). Serum Gd-IgA1 levels were significantly higher in IgAN patients than disease controls and healthy controls. In patients with IgAN, serum Gd-IA1 levels were significantly correlated with estimated glomerular filtration rate, serum IgA level, and tubular atrophy/interstitial fibrosis. CKD progression was more frequent in IgAN patients with higher serum Gd-IgA1 levels than in those with lower serum Gd-IgA1 levels. Cox proportional hazard models showed that high GdIgA1 level was an independent risk factor for CKD progression after adjusting for several confounders. Our results suggest that serum Gd-IgA1 level is a useful diagnostic and prognostic marker in IgAN patients. Further studies with a larger sample size and longer follow-up duration are needed.

Long-Term Beneficial Effects of Tonsillectomy on Patients with Immunoglobulin A Nephropathy.

Tonsillectomy may treat IgA nephropathy (IgAN) by reducing the levels of galactose-deficient IgA1. Therefore, we aimed to analyze the long-term effects of tonsillectomy on patients with IgAN, as an initial treatment and as a treatment at any time in their lives. In this retrospective cohort analysis, 1147 patients with IgAN were grouped according to whether they had undergone tonsillectomy at any time, >1 year after renal biopsy (study 1), or within 1 year after renal biopsy (study 2). The patients were propensity-score matched or divided into four groups according to their proteinuria and renal function. The 20-year renal survival rates were evaluated until serum creatinine levels doubled (primary end point) and ESKD occurred (secondary end point). Patients in both studies had similar background characteristics after propensity score matching. In study 1, the renal survival rates for the primary and secondary end points were significantly higher for patients who underwent tonsillectomy at any time or >1 year after renal biopsy compared with those who did not. In study 2, the renal survival rates for the primary and secondary end points were significantly higher for patients who underwent tonsillectomy soon after renal biopsy compared with those who did not (primary end point, 98% versus 69%, P=0.001; secondary end point, 100% versus 75%, P=0.0001). A stratified analysis showed that significant treatment efficacy was observed for patients with proteinuria >1.0 g/d. Multivariate Cox regression analyses showed that tonsillectomy was associated with disease progression (hazard ratio, 0.27; P=0.04). Complications associated with tonsillectomy occurred in 8% of patients. Among patients with IgAN, tonsillectomy at any time of life, or soon after renal biopsy, prevents disease progression, and the procedure is relatively safe.

Modifications of gut microbiota are associated with the severity of IgA nephropathy in the Chinese population

Immunoglobulin A nephropathy (IgAN) is a common glomerular disease. The pathogenesis of IgAN is associated with dysregulated intestinal mucosal immunity. However, whether gut microbial modifications play a role in IgAN remains unclear. Blood and faecal samples were collected from 52 patients with IgAN and 25 healthy controls (HCs). The gut microbiome was analysed using the 16S ribosomal RNA gene. The levels of galactose-deficient IgA1 (Gd-IgA1), soluble cluster of differentiation 14 (sCD14), lipopolysaccharide binding protein (LBP), intercellular adhesion molecule-1 (ICAM-1), tumour necrosis factor α (TNF-α), interleukin-1, and C-reactive protein were quantified. Substantial differences in the gut microbiota were identified between patients with IgAN and HCs (P < 0.05). Bacteroides and Escherichia-Shigella levels were significantly higher in patients with IgAN than in HCs, while Bifidobacterium and Blautia spp. Levels were lower. Higher proportions of Escherichia-Shigella and lower proportions of Bifidobacterium spp. were observed in patients with IgAN with high urine RBC count (≥10/HP) and proteinuria (≥1 g/24 h) levels. Correlation analysis was used to assess the association between gut microbiota and biomarkers in patients with IgAN. The results showed that Prevotella 7 levels were negatively correlated with Gd-IgA1, LBP, sCD14, ICAM-1, and TNF-α levels, while Bifidobacterium spp. Levels presented a significant inverse relationship with LBP and Gd-IgA1. Additionally, Escherichia-Shigella levels were negatively correlated with Prevotella 7. In patients with IgAN, gut modifications were characterised by an increase in the number of pathogenic bacteria and a reduction in the levels of beneficial bacteria, suggesting that the disturbance of intestinal microflora might be important in the severity of IgAN.

Serum levels of galactose-deficient IgA1 in Chinese children with IgA nephropathy, IgA vasculitis with nephritis, and IgA vasculitis.

IgA nephropathy (IgAN) and IgA vasculitis with nephritis (IgAV-N) are related diseases. Galactose-deficient IgA1 (Gd-IgA1) plays an important role in the pathology of IgAV-N and IgAN, so we aim to compare the serum levels of Gd-IgA1 in Chinese pediatric patients with IgAN, IgAV-N, and IgAV. We retrospectively enrolled 52 patients with IgAN, 57 patients with IgAV-N, 26 patients with IgAV, and 40 healthy children. The serum levels of Gd-IgA1 were measured at the time of biopsy using a lectin-based ELISA method. Gd-IgA1 levels in IgAV-N patients and IgAN patients were higher than in healthy controls (303.94 ± 39.37 U/ml, 314.91 ± 47.79 U/ml vs. 273.57 ± 48.29 U/ml, P < 0.001), and Gd-IgA1 levels in IgAV-N patients were higher than in IgAV patients (303.94 ± 39/ml vs. 286. 21 ± 38.81 U/ml, P = 0.059), but the latter result is not statistically significant. The Gd-IgA1 levels in IgAV patients were comparable with those in healthy controls (286.21 ± 38.81 U/ml vs. 273.57 ± 48.29 U/ml, P = 0.267). Among the four groups, we did not observe significant correlations of Gd-IgA1 levels with eGFR, proteinuria, or the MEST-C score. Serum Gd-IgA1 maybe involved in the pathogenesis of the IgAV-N and IgAN. However, we found no statistically significant correlation between Gd-IgA1 levels and clinical and pathological features.

TLR7 in B cells promotes renal inflammation and Gd-IgA1 synthesis in IgA nephropathy.

TLR7 has been linked to the pathogenesis of glomerulonephritis, but its precise roles are not clear. In this study, we evaluated the roles of TLR7 in IgA nephropathy (IgAN). TLR7 proteins were abundant in CD19+ B cells infiltrated in the kidneys of patients with IgAN. The intensities of both intrarenal TLR7 and CD19 proteins were closely associated with kidney function (estimated glomerular filtration rate [eGFR] and serum creatinine concentration) and renal histopathology (tubular atrophy, leukocyte infiltration, tubulointerstitial fibrosis, and global glomerulosclerosis) in patients with IgAN. Meanwhile, TLR7 mRNA levels were significantly increased in peripheral blood B cells of patients with IgAN. TLR7+CD19+ B cells expressed inflammatory cytokines (IL-6 and IL-12) in kidneys and produced high levels of IgA1 and galactose deficient-IgA1 (Gd-IgA1) in peripheral blood of patients with IgAN. Mechanistically, TLR7 activated B cells to produce high levels of Gd-IgA1 via the TLR7-GALNT2 axis in IgAN. Protein levels of GALNT2 were increased by overexpression of TLR7, while they were reduced by TLR7 knockdown in B cells. GALNT2 overexpression augmented Gd-IgA1 production in B cells derived from patients with IgAN. Taken together, high TLR7 expression in B cells has dual roles in the development and progression of IgAN, by facilitating renal inflammation and Gd-IgA1 antibody synthesis.

ST6Gal1 is up-regulated and associated with aberrant IgA1 glycosylation in IgA nephropathy: An integrated analysis of the transcriptome.

Galactose‐deficient IgA1 (Gd‐IgA1) plays a crucial role in the development of Immunoglobulin A nephropathy (IgAN), however, the underlying pathogenic mechanisms driving Gd‐IgA1 production in B cells are not well understood. In this study, RNA‐seq analysis identified 337 down‐regulated and 405 up‐regulated genes in B cells from 17 patients with IgAN and 6 healthy controls. Among them, ST6Gal1, which was associated with IgAN in a previous genome‐wide association study (GWAS), was up‐regulated in IgAN and significantly positive correlated with elevated Gd‐IgA1. In addition, we identified increased plasma ST6Gal1 levels in 100 patients with IgAN, which were associated with higher levels of proteinuria, plasma IgA, Gd‐IgA1 levels, greater degrees of systemic complement activation including C3a, Bb, C4d, MAC and a lower proportion classified as C2 grade (crescent proportion ≥25%). Interesting, in vitro, recombinant ST6Gal1 (rST6Gal1) exposure reduced the production of Gd‐IgA1 in cultured peripheral blood mononuclear cells from IgAN patients. rST6Gal1 stimuli also increased expression of C1GALT1, which were well‐known proportional to the decrease in galactose deficiency of IgA1. In conclusions, we identified increased plasma ST6Gal1 levels and the association of ST6Gal1 with disease severity of IgAN. Additionally, rST6Gal1 administration in vitro increased expression of C1GALT1 and reduced the production of Gd‐IgA1.

P0379BION-1301, A FULLY BLOCKING ANTIBODY TARGETING APRIL FOR THE TREATMENT OF IGA NEPHROPATHY: ASSESSMENT OF SAFETY, PHARMACOKINETICS AND PHARMACODYNAMICS IN LONG-TERM NONCLINICAL STUDIES

Abstract Background and Aims IgA Nephropathy (IgAN) is a common form of glomerulonephritis and its pathogenesis is thought to consist of sequential pathogenic hits, including the production of auto-antigen galactose-deficient IgA1 (Gd-IgA1) and auto-antibody formation ultimately resulting in immune complex deposition, inflammation and functional deterioration of the kidney. Serum levels of APRIL (A PRoliferation Inducing Ligand, TNFSF13) and levels of Gd-IgA1 are correlated with severity of disease (Zhao et al, 2012). As a ligand for the receptors BCMA and TACI, APRIL is thought to regulate differentiation and proliferation of B cells and plasma cells and IgA class switching. BION-1301 is a humanized antibody neutralizing APRIL. In nonhuman primates, BION-1301 reduced serum levels of IgA, IgM, and IgG with no drug-related toxicity (Dulos J, et al. ASN Annual Meeting. 2018). Here we describe the nonclinical safety assessment of BION-1301, to support its continued clinical development for the treatment of IgA Nephropathy. Method A 14-week repeat-dose toxicity and toxicokinetic/pharmacodynamic (TK/PD) study in non-human primates (NHP) was performed by biweekly intravenous bolus (IV) administration of BION-1301 at three different dose levels. To support a potential change in route of administration, a 4-week repeat-dose NHP bridging study was conducted with weekly subcutaneous (SC) administration of BION-1301 at three different dose levels. Results In both the 14-week IV study and the 4-week SC study, BION-1301 was evaluated for safety, TK and PD. For TK and PD, BION-1301 levels, uncomplexed APRIL levels and immunoglobulin levels (IgA, IgG, IgM) were quantified in serum. Immunophenotyping was performed on peripheral blood to assess the impact of BION-1301 on the B cell compartment. In both studies BION-1301 was well tolerated with no test-article related findings. 14-week IV dosing as well as 4-week SC dosing of BION-1301 reduced serum APRIL levels as well as serum immunoglobulin levels. Conclusion Results of these nonclinical toxicity studies with toxicology, TK and PD endpoints demonstrate that BION-1301 is well tolerated for up to 14 weeks of dosing, corroborates pharmacodynamic proof-of-mechanism and support prolonged dosing and SC administration of BION-1301 in patients with IgA Nephropathy.

P0500RESULTS OF A PHASE 1 TRIAL TO INVESTIGATE THE SAFETY, TOLERABILITY, PHARMACOKINETICS, AND PHARMACODYNAMICS OF BION-1301 IN HEALTHY VOLUNTEERS

Abstract Background and Aims IgA nephropathy (IgAN), the leading cause of primary glomerulonephritis, is an autoimmune disease with no approved treatments. Slow progression to end-stage-renal disease occurs in up to 50% of patients with IgAN over approximately 20-25 years, resulting in the need for dialysis or kidney transplant. A critical step in IgAN pathogenesis is the production of galactose-deficient IgA1 (Gd-IgA1) leading to the generation of anti-Gd-IgA autoantibodies and the formation of immune complexes that result in kidney inflammation and damage. Patients with IgAN have elevated levels of A proliferation-inducing ligand (APRIL), which may contribute to IgAN pathogenesis by regulating differentiation and proliferation of B cells. In a study of patients with IgAN, those with high plasma APRIL levels had higher levels of Gd-IgA1 and proteinuria and lower estimated glomerular filtration rates compared to those with lower plasma APRIL levels. BION-1301 is a first-in-class humanized antagonistic antibody targeting APRIL. BION-1301 reduced serum levels of IgA, IgM, and IgG with no drug-related toxicity in nonhuman primates and was well-tolerated with no dose-limiting toxicities in a Phase 1/2 first-in-human clinical study in patients with late-stage multiple myeloma. The Phase 1 trial described here will characterize the safety, pharmacokinetic (PK), and pharmacodynamic (PD) profiles of BION-1301 in healthy volunteers (HV) and patients with IgAN. Methods The protocol for this study (NCT03945318) is comprised of 3 parts, of which only Parts 1 and 2 are complete. Parts 1 and 2 assess BION-1301 in HV, and Part 3 will assess BION-1301 in patients with IgAN. Parts 1 and 2 are double-blind, randomized, placebo-controlled single and multiple ascending dose designs, respectively. Part 3 will assess a multiple dose regimen in IgAN patients. Part 1 enrolled 36 HV in 5 dose cohorts, randomized in a 3:1 ratio to receive a single dose of BION-1301 or placebo delivered by IV infusion. Part 2 enrolled 27 HV in 3 dose cohorts, randomized in a 2:1 ratio to receive 3 doses of BION-1301 or placebo delivered by IV infusion once every two weeks over a one month period. Dose escalation decisions were made by a Safety Review Team based on safety, tolerability, and PK-related stopping criteria. Results To-date, BION-1301 continues to be well tolerated. Its biological activity in the study is characterized by free APRIL, IgA, IgG, and IgM levels; unblinded safety, PK, and PD results for Parts 1 and 2 in Healthy Volunteers will be presented. Conclusion BION-1301, a humanized anti-APRIL antibody, may provide a novel avenue for the potential treatment of IgAN that offers potential advantages compared to currently used antihypertensive or immunosuppressive therapies.

P0356QUANTITATIVE ASSESSMENT OF GALNAC NUMBER IN THE HINGE REGION OF IGA1 IN IGA NEPHROPATHY WITH CRESCENTS FORMING

Abstract Background and Aims Aberrant IgA1 O-linked glycosylation of IgA1 hinge region (HR) has been shown playing an important role in the pathogenesis of IgA nephropathy (IgAN). Serum levels of galactose-deficient IgA1 (Gd-IgA1) was associated with the development and progression in IgAN, however variations in the composition of IgA1 HR glycoforms are unknown. In this study we aim to quantitative assessment of GalNAc number in the hinge region of IgA1 in IgAN with crescents forming using mass spectrometry. Method Plasma polymeric IgA1 (pIgA1) was purified from a discovery cohort including crescentic IgAN (n=11) non-crescentic IgAN (n=10) and healthy controls (HC, n=10) and a validation cohort (crescentic IgAN, n=10; non-crescentic IgAN, n=10 and healthy controls, n=11). After denaturation, reduction, alkylation and trypsin digestion, liquid chromatography-high-resolution mass spectrometry (LC-MS) was used to analyse the IgA1 HR glycans. The intensity of the identified IgA1 O-glycopeptide was calculated and expressed as the relative abundance for each glycopeptide. The molecular weight (MW) of intact O-glycopeptide was calculated as the formula following: MW = HR + x GalNAc + y Gal + z NeuAc + H+ (x, y and z represent the number of GalNAc, galactose and NeuAc which bind to one HR in IgA1 O-linked glycopeptides respectively) Glycopeptide content ratio = (glycopeptide peak intensity/ total glycopeptide intensity) ×100%. Results In the discovery cohort population, the level of Gd-IgA1 was highest in patients with crescentic IgAN, middle in patients with non-crescentic IgAN and lowest in healthy controls (347.69±57.89 U/ml vs 336.32±38.44 U/ml vs 330.14±33.22 U/ml), albeit that didn’t reach the statistical significance. There were significantly difference in GalNAc number of IgA1 HR among patients with IgAN and healthy controls. Overall the numbers of GalNAc bound to one HR was much lower in the patients than healthy controls. As shown in the Figure 1, the proportion of GalNAc 3, defined as O-glycans that were bound to one HR at 3 sites, were highest in patients with crescentic IgAN, then the non-crescentic IgAN and lowest in the healthy controls (9.92%±3.37% vs 6.65%±1.53% vs 4.05%±1.24%; p-value for the trend&amp;lt;0.001). Similar results were observed in GalNAc 4 (45.91%±4.75% vs 41.13%±2.95% vs 40.98%±2.95%; P=0.004. However regarding the GalNAc 5 and GalNAc 6, crescentic IgAN was lowest, then non-crescentic IgAN and highest in the healthy control (GalNAc 5: 45.17%±5.46% vs 46.90%±2.78% vs 48.05%±3.02%, P=0.001 GalNAc 6:1.62%±1.60% vs 3.95%±1.92% vs 5.39%±2.38%; P&amp;lt;0.001). These results were consistent in the validation cohort (Figure 1). Conclusion GalNAc numbers in IgA1 HR was lower in patients with IgAN especially in crescentic IgAN. These results suggest that the O-glycans of IgA1 were associated with the severe phenotype in IgA nephropathy.

Clinical Significance of Serum Galactose-Deficient IgA1 Level in Children with IgA Nephropathy.

This study was aimed at investigating the clinical significance of serum galactose-deficient IgA1 (Gd-IgA1) levels measured by a novel lectin-independent enzyme-linked immunosorbent assay (ELISA) using an anti-Gd-IgA1 monoclonal antibody (KM55) as a disease-specific biomarker for IgA nephropathy (IgAN) in children. Thirty-three children with IgAN, 40 with non-IgA glomerular diseases, and 38 age-matched healthy controls (HCs) were enrolled. Serum Gd-IgA1 levels were quantified by ELISA using KM55. Results were statistically compared with clinical features and pathological findings of IgAN. Serum Gd-IgA1 levels were significantly elevated in children with IgAN compared with children with non-IgA glomerular diseases and HCs. Serum Gd-IgA1 levels in children with IgAN were positively correlated with serum total IgA levels. However, the serum Gd-IgA1/total IgA ratio (Gd-IgA1/IgA) was also significantly elevated in children with IgAN. Serum Gd-IgA1 levels in children with IgAN increased in an age-dependent manner. The cutoff value of serum Gd-IgA1 levels for differentiating IgAN from non-IgA glomerular diseases was 3236 in children < 12 years and 5284 in children ≥ 12 years, respectively. In contrast, serum Gd-IgA1/IgA was age-independent. The cutoff value of serum Gd-IgA1/IgA for differentiating IgAN from non-IgA glomerular diseases was 0.2401. Serum Gd-IgA1 levels were negatively correlated with eGFR and positively correlated with mesangial IgA deposition. In contrast, serum Gd-IgA1/IgA levels were not correlated with any clinical parameters of IgAN. In conclusion, serum Gd-IgA1 levels were significantly elevated in children with IgAN. However, those levels were age-dependent; therefore, serum Gd-IgA1 levels classified by age and/or serum Gd-IgA1/IgA might have diagnostic values in children with IgAN.

Expression and significance of follicular helper T cells and galactose-deficient IgA1 in children with Henoch-Schönlein purpura

To study the role of follicular helper T (Tfh) cells and galactose-deficient IgA1 (Gd-IgA1) in the pathogenesis of childhood Henoch-Schönlein purpura (HSP) and the correlation between them. A total of 36 children with newly-diagnosed HSP were enrolled. They were divided into two groups: HSP nephritis (HSPN) group with 11 children and non-HSPN group with 25 children according to the presence or absence of HSPN. Another 15 children who underwent physical examination at the outpatient service were enrolled as the healthy control group. Flow cytometry was used to measure the proportion of Tfh cells (CD4+CXCR5+ICOS+) in peripheral blood. ELISA was used to measure the levels of interleukin-21 (IL-21) and interleukin-6 (IL-6) in peripheral blood and the serum levels of IgA1 and Gd-IgA1. A Pearson correlation analysis was used to investigate the correlation of serum Gd-IgA1 concentration with Tfh cells and related factors expression in the children with HSP. Both the HSPN and non-HSPN groups had significantly higher proportion of Tfh cells and expression levels of IL-21 and IL-6 in peripheral blood than the healthy control group (P<0.05). The HSPN group had significant increases in the above indices compared with the non-HSPN group (P<0.05). Both the HSPN and non-HSPN groups had significantly higher serum levels of IgA1 and Gd-IgA1 than the healthy control group (P<0.05). The HSPN group had significantly higher serum levels of IgA1 and Gd-IgA1 than the non-HSPN group (P<0.05). In the children with HSP, serum Gd-IgA1 level was positively correlated with Tfh cells proportion and IL-21 and IL-6 levels (P<0.05). Tfh cells and related cytokines and serum Gd-IgA1 are involved in the development of HSP/HSPN. Tfh cells may mediate the increased production of Gd-IgA1.

A cross-sectional analysis of clinicopathologic similarities and differences between Henoch-Schönlein purpura nephritis and IgA nephropathy.

Recent studies noted that Henoch-Schönlein purpura nephritis (HSPN) and IgA nephropathy (IgAN) share the feature of galactose-deficient IgA1 (Gd-IgA1)-oriented pathogenesis, although there are distinct clinical differences. We aimed to clarify the clinicopathologic differences between these 2 diseases. We cross-sectionally analyzed adult patients with HSPN (n = 24) or IgAN (n = 56) who underwent renal biopsy (RB) between 2008 and 2018 at Showa University Hospital. Serum Gd-IgA1 (s-Gd-IgA1) levels at the time of RB were compared among study groups using enzyme-linked immunosorbent assay (ELISA) with anti-human Gd-IgA1-specific monoclonal antibody (KM55). We also immunohistochemically stained paraffin-embedded sections for glomerular Gd-IgA1 (g-Gd-IgA1)-deposition using KM55. Serum inflammatory cytokines were measured using ELISA. Glomerular endothelial injury with subendothelial IgA deposition was significant in patients with HSPN. Serum IL-8, MCP-1, TNF-α, and IL-6 levels were significantly higher in patients with HSPN than IgAN. Levels of s-Gd-IgA1 were comparable among patients with HSPN and IgAN, and a similar degree of g-Gd-IgA1-deposition was detected in both diseases. Furthermore, g-Gd-IgA1-deposition was evident in patients with histopathologically advanced HSPN or IgAN. In HSPN, significant positive correlations between s-Gd-IgA1 levels and crescent formation or IL-6 elevation were confirmed, and g-Gd-IgA1 intensity showed a significant positive correlation with MCP-1 and a tendency to positively correlate with IL-8. Meanwhile, patients with IgAN showed no correlation between inflammatory cytokines and both-Gd-IgA1. Moreover, most g-Gd-IgA1-positive areas were not double stained with CD31 in HSPN. Although assessing both-Gd-IgA1 alone was insufficient to distinguish between HSPN and IgAN, patients with HSPN showed considerable glomerular capillaritis with subendothelial IgA deposition and significant elevation of serum inflammatory cytokines. Furthermore, such glomerular subendothelial IgA deposition might not contain Gd-IgA1, and factors associated with Gd-IgA1 were inconsistent among these 2 diseases. Thus, developmental mechanisms for IgAN might not apply to HSPN completely, and these 2 diseases still have different aspects.

SUN-364 SERUM LEVELS OF SECRETORY IGA WERE NOT ELEVATED IN JAPANESE PATIENTS WITH IGA NEPHROPATHY

There are increasing evidences that galactose-deficient IgA1 (Gd-IgA1) and Gd-IgA1-containing immune complexes are essential effector molecules in IgAN. Dysregulation of mucosal immune system is considered as a major cause of development of IgAN. Secretary IgA (SIgA), which is dominant in external mucosal secretions, is characterized as the ‘first line defense’ in mucosae. Previous studies suggested that the serum levels of SIgA are elevated in patients with IgAN, and higher serum SIgA is associated with low GFR and proteinuria. In addition, mesangial deposits of SIgA were detected in about 15% of patients with IgAN. However, pathogenic role of SIgA and its glycosylation pattern are not clarified. We measured the serum levels of SIgA in patients with IgAN (n=37) and healthy controls (HC, n=4) by ELISA. Serum levels of SIgA before and after tonsillectomy were also measured. We analyzed the association between serum levels of SIgA and eGFR, proteinuria and histological severity in patients with IgAN. Furthermore, we analyzed whether serum levels of SIgA correlated with those of Gd-IgA1 and Gd-IgA1-containing immune complexes. There was no significant difference in serum levels of SIgA between patients with IgAN and HC. Serum levels of SIgA were not correlated with any clinical parameters such as eGFR, proteinuria and histological severity. Importantly, there were no significant associations between serum levels of SIgA and Gd-IgA1 or Gd-IgA1-containing immune complexes. In addition, serum levels of SIgA did not change before and after tonsillectomy. Serum levels of SIgA were not elevated in Japanese patients with IgAN. We need further investigations at cellular and molecular levels to understand the production site of SIgA and its role in the pathogenesis of IgAN.

SAT-368 Galactose-deficient IgA1 containing immune complexes deposit in mesangium via endothelial cell injuries

IgA nephropathy (IgAN) is the most common primary glomerulonephritis, and causes end-stage renal disease in 20–40% of patients within 20 years after onset of this disease. IgAN is defined by the presence of dominant or co-dominant mesangial IgA1 immune deposits, accompanied by C3 deposits, and deposition of IgA1 includes galactose-deficient IgA1 (Gd-IgA1). Serum levels of Gd-IgA1 and Gd-IgA1-containing immune complexes (IC) with Gd-IgA1-specific autoantibodies are elevated in patients with IgAN. However, the pathogenic role of Gd-IgA1-containing IC and mesangial immune deposits are still unclear. The endothelial surface glycocalyx modulates vascular function. Furthermore, loss of the glomerular endothelial glycocalyx links albuminuric kidney disease. Therefore, we examined that Gd-IgA1-containg ICs deposit in mesangium through glomerular endothelial cell disorder. Gd-IgA1 and recombinant anti-glycan IgG were used to form IC (Gd-IgA1-IgG IC) to inject i.v into nude mice. After various time intervals, mice were sacrificed and kidney was harvested to determine mesangial deposition and kidney injuries. Samples of urine were collected to determine urinary protein and hematuria. Furthermore, human renal glomerular endothelial cells (HRGEC) were co-cultured with Gd-IgA1 alone or Gd-IgA1-IgG IC for 72 h to assess the potential capacity of these IC to activate endothelial cells. Transcript levels of TNF-α, TGF-β, IL-6, ICAM1 and E-selectin in HRGEC were measured by Real-time PCR. Also, to investigate that Gd-IgA1-IgG IC stimulation increases permeability of glomerular microvascular resulted in renal injuries, the renal microvascular endothelial glycocalyx removal was estimated by real-time glycocalyx imaging. Gd-IgA1 alone or Gd-IgA1-IgG IC were injected into nude mice. The glycocalyx were observed for 45 min and after that mice were sacrificed to confirm glomerular deposition. Gd-IgA1 and anti-glycan IgG formed IC that deposited with murine C3 in the mesangium and in small amounts in the subendothelial area of the glomerular capillaries, and induced proteinuria and hematuria. Electron microscopic examination showed that injection of Gd-IgA1-IgG IC induced podocyte and endothelial injuries. Stimulation with Gd-IgA1-IgG IC upregulated transcript levels of TNF-α, IL-6, ICAM1 and E-selectin in HRGEC (P<0.01). Real-time glycocalyx imaging showed that Gd-IgA1-IgG IC removed renal microvascular glycocalyx immediately after injection. Furthermore, after stimulation with Gd-IgA1-IgG IC, IgA and C3 were deposited in mesangium, and proteinuria and hematuria were induced. Gd-IgA1-containg IC might bind to glomerular endothelial cells and induce release of pathogenic cytokines and chemokines. Furthermore, stimulation of Gd-IgA1-containg IC involved in endothelial dysfunction with complementary activation resulted in renal injuries.

Helicobacter pylori infection is associated with elevated galactose-deficient IgA1 in IgA nephropathy

Background Mucosal immunity plays an important role in the pathogenesis of IgA nephropathy (IgAN). This study aimed to investigate if infection of Helicobacter pylori (H. pylori), a common bacteria in the gastrointestinal tract, associated with IgAN. Methods This study included 261 patients with IgAN and 46 healthy controls. Clinical information and plasma samples were collected from patients and healthy controls. H. pylori infection was confirmed by western blot. Plasma IgA1 and galactose-deficient IgA1 (Gd-IgA1) levels were detected by specific enzyme-linked immunosorbent assay. Results Total H. pylori infection rates showed no statistical differences between IgAN patients and healthy controls, but the infection rates of type I H. pylori in IgAN patients were significantly higher than those in healthy controls (44.4 vs. 28.3%, p = 0.040). Compared with uninfected patients, the systolic blood pressure, 24-h proteinuria, and blood urea nitrogen levels were significantly higher in patients with H. pylori infection (126.0 ± 15.5 vs. 119.6 ± 14.5 mmHg, p = 0.010; 1.8 ± 2.7 vs. 1.2 ± 1.4 g/24h, p = 0.013; 7.9 ± 5.4 vs. 6.7 ± 3.9 μmol/L, p = 0.042), especially in patients with type I infection (126.5 ± 15.4 vs. 119.6 ± 14.5 mmHg, p = 0.002; 1.9 ± 2.9 vs. 1.2 ± 1.4 g/24 h, p = 0.033; 8.1 ± 5.6 vs. 6.7 ± 3.9 μmol/L, p = 0.041). Similarly, patients with IgAN and type I H. pylori infection showed higher plasma Gd-IgA1 levels than uninfected patients (5.5 ± 2.2 vs. 4.5 ± 2.2 μg/mL, p = 0.037). Conclusions Virulent type I H. pylori infection is more common in patients with IgAN. Patients with IgAN and type I H. pylori infection showed lower renal function and higher underglycosylation of plasma IgA1.

Elevated hsa-miR-590-3p expression down-regulates HMGB2 expression and contributes to the severity of IgA nephropathy.

Peripheral blood mononuclear cells (PBMCs) play important roles in the pathogenesis of IgA nephropathy (IgAN). Our study aimed to provide a deep understanding of IgAN and focused on the dysregulation of hsa‐miR‐590‐3p and its target gene HMGB2 in PBMCs. Three gene expression profile datasets (GSE14795, GSE73953 and GSE25590) were downloaded from the GEO database. The DEGs (differentially expressed genes)‐miRNA network that was associated with IgAN was constructed by Cytoscape, and HMGB2 and hsa‐miR‐590‐3p were selected for further exploration. The dual‐luciferase reporter system was utilized to verify their interaction. Then, the expression levels of HMGB2 and hsa‐miR‐590‐3p in PBMCs were detected by qPCR in another cohort, and the correlation of their expression levels with the clinical pathological manifestations and serum Gd‐IgA1(galactose‐deficient IgA1) levels was also investigated. HMGB2 was identified as the target gene of hsa‐miR‐590‐3p. Furtherly, the elderly patients had higher HMGB2 expression levels than the expression levels of the younger patients. As the serum creatinine, serum BUN levels increased, the expression of HMGB2 decreased; Besides, the HMGB2 expression was positively correlated with serum complement 3(C3) levels, and it also had a negative correlation with the diastolic blood pressure, but not reach statistical significance. What is more, both hsa‐miR‐590‐3p and HMGB2 expression had a slight correlation tendency with serum Gd‐IgA1 levels in the whole population. In conclusion, HMGB2, the target gene of hsa‐miR‐590‐3p, was identified to correlate with the severity of IgAN, and this provides more clues for the pathogenesis of IgAN.

Comprehensive analysis of aberrantly expressed profiles of mRNA and its relationship with serum galactose-deficient IgA1 level in IgA nephropathy

BackgroundImmunoglobulin A nephropathy (IgAN) is the leading cause of end-stage kidney disease. Previous mRNA microarray profiling studies of IgAN revealed inconsistent data. We sought to identify the aberrantly expressed genes and biological pathways by integrating IgAN gene expression datasets in blood cells and performing systematically experimental validation. We also explored the relationship between target genes and galactose-deficient IgA1 (Gd-IgA1) in IgAN.MethodsWe retrieved Gene Expression Omnibus (GEO) datasets of IgAN. Gene Ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses were used for functional analysis. Deep sequencing on RNA isolated from B cells was used for microarray validation. The relationship between target mRNA expressions and Gd-IgA1 levels in serum were also studied.ResultsThree studies with microarray expression profiling datasets met our inclusion criteria. We identified 655 dyregulated genes, including 319 up-regulated and 336 down-regulated genes in three GEO datasets with a total of 35 patients of IgAN and 19 healthy controls. Based on biological process in GO term, these dyregulated genes are mainly related to pentose-phosphate shunt, non-oxidative branch, post-embryonic camera-type eye development and leukocyte activation. KEGG pathway analysis of microarray data revealed that these aberrantly expressed genes were enriched in human T-cell leukemia virus 1 infection, proteoglycans in cancer, intestinal immune network for IgA production and autophagy. We further performed deep sequencing on mRNAs isolated from B cells of an independent set of five patients with IgAN and three healthy persons with the same clinical and demographic characteristics. Seventy-seven genes overlapped with 655 differentially regulated genes mentioned above, including 43 up-regulated and thirty-four down-regulated genes. We next investigated whether these genes expression correlated with Gd-IgA1 levels in IgAN patients. Pearson correlation analyses showed PTEN (phosphatase and tensin homolog) was the most powerful gene negatively correlated with Gd-IgA1 levels.ConclusionsThese results demonstrated that dyregulated genes in patients with IgAN were enriched in intestinal immune network for IgA production and autophagy process, and PTEN in B cells might be involved in the mechanism of Gd-IgA1 production.