Serum Levels Of Galactose-deficient IgA1 Research Articles

#1307 Glomerular galactose-deficient IgA1 (KM55) positive may be associated with poor prognosis in DKD patients

Abstract Background and Aims Diabetic kidney disease (DKD) and IgA nephropathy (IgAN) are prevalent renal diseases with a high incidence rate, and the prognosis is notably poorer when these two diseases coexist. However, it remains uncertain whether the pathological changes associated with DKD combined with IgA deposition (DKD-IgA deposition) are linked to a worsened prognosis. Method To address this question, we conducted an analysis comparing the clinicopathological characteristics and prognosis of DKD-IgA deposition patients to DKD patients as controls (Fig. 1). Results The results revealed that DKD-IgA patients exhibited higher cholesterol levels compared to DKD patients (6.2 ± 2.0 vs. 5.4 ± 1.9 mmol/L, p = 0.042). The group with DKD-IgA deposition had a significantly shorter follow-up duration (10.9 ± 10.6 months) compared to the control group (20.4 ± 18.7 months, p = 0.029). However, they exhibited higher levels of serum creatinine at the end of the follow-up period (343.8 ± 328.0 μ mol/L vs. 182.1 ± 124.6 μmol/L, p = 0.031). Kaplan-Meier analysis showed a higher cumulative incidence of poor events in the DKD-IgA deposition group (p = 0.036) (Fig. 2). In addition, we also detected galactose deficient IgA1 (KM55) in the kidneys and serum of patients with DKD-IgA deposition. Of the 24 patients with DKD-IgA deposition, 54.5% (24/44) showed positive glomerular KM55 results. Immunofluorescence analysis revealed that KM55 and IgA were predominantly colocalized in the mesangial and capillary regions (Fig. 3). Furthermore, the subgroup with KM55 positivity had a shorter disease duration compared to the KM55 negative subgroup (66.0 vs. 120.0 months, p = 0.048). The serum levels of galactose-deficient IgA1 (Gd-IgA1) (6296.4 ± 1535.4 vs. 4057.4 ± 1082.0 ng/mL, p = 0.010) and C4 (0.4 ± 0.1 vs. 0.3 ± 0.1 g/L, p = 0.020) were significantly higher in the KM55 positive subgroup than in the KM55 negative subgroup. Furthermore, it was observed that the KM55 positive subgroup exhibited a considerably higher incidence of reaching the renal endpoint compared to the control group (64.3% vs. 20.0%, p = 0.047). Conclusion These study results suggest that individuals with DKD who display glomerular IgA deposition alongside KM55 positivity may experience a more unfavorable prognosis.

#812 Phase 2b ORIGIN study open label extension with atacicept in patients with IgA nephropathy and persistent proteinuria: week 72 interim analysis

Abstract Background and Aims IgA nephropathy (IgAN), the most common primary glomerulonephritis and a significant contributor to ESKD worldwide, is characterized by elevated serum levels of galactose-deficient IgA1 (Gd-IgA1). The production of Gd-IgA1 and its autoantibodies is driven by both the B-cell Activating Factor (BAFF) and A PRoliferation-Inducing Ligand (APRIL) signaling pathways that stimulate maturation, differentiation, and effector function of B cells and plasma cells. Atacicept is a fusion protein targeting both BAFF and APRIL in clinical development for IgAN treatment. The Phase 2b ORIGIN study met the primary endpoint with statistically significant urine protein:creatinine ratio (UPCR) reduction at 24 weeks vs placebo. At 36 weeks, atacicept 150 mg achieved statistically significant and clinically meaningful UPCR reduction, eGFR stabilization, and Gd-IgA1 reduction vs placebo, with similar safety to placebo. This interim analysis reports 72-week results from the open-label extension period. Method The randomized, double-blind, placebo-controlled Phase 2b ORIGIN study included 116 participants with biopsy-proven IgAN, 24 h urine protein >0.75 g/day or UPCR >0.75 g/g, and eGFR ≥30 mL/min/1.73 m2 despite optimized renin–angiotensin system blockade. Participants were randomized to atacicept 150, 75, or 25 mg, vs placebo (2:2:1:2), self-administered by subcutaneous injection once weekly for up to 36 weeks. The double-blind randomized treatment period was followed by an open-label extension in which participants could receive atacicept 150 mg for up to 60 additional weeks, for a total of 96 weeks. For this interim analysis, changes from baseline in eGFR, natural log transformed UPCR, and Gd-IgA1 through 72 weeks were analyzed using a mixed-effects model for repeated measurements. Microscopic hematuria was evaluated on urine dipstick and participants with hematuria grade 1+ or higher at baseline were evaluated for resolution, defined as a decrease to negative/trace, at 72 weeks. Results Of 116 randomized participants in the double-blind period, 106 participants (91%) completed 72 weeks of treatment. At 72 weeks, eGFR total slope estimate was 0.0 mL/min/1.73m2/year and eGFR change from baseline was 0 mL/min/1.73m2 in all participants originally randomized to atacicept (all-atacicept group; n = 82). After switching to open-label atacicept 150 mg, the original placebo group showed eGFR stabilization with −3.2 mL/min/1.73m2 change from baseline at 72 weeks vs −4.9 mL/min/1.73m2 at 36 weeks (Figure 1). At 72 weeks, UPCR change from baseline was −45% in the all-atacicept group and the placebo switch group showed a −47% UPCR change from baseline at 72 weeks vs +3% at 36 weeks (Figure 2). Open-label atacicept 150 mg was also associated with rapid Gd-IgA1 reduction in the placebo switch group at 48 weeks that was sustained through 72 weeks. Hematuria resolution was observed at 72 weeks in 81% (35/43) of participants in the all-atacicept group and 59% (10/17) in the placebo switch group. Atacicept was generally well tolerated during the open-label extension, with a similar rate of infections compared to the double-blind period and one study drug-related serious adverse event. Conclusion At 72 weeks, treatment with atacicept 150 mg was associated with sustained eGFR stability and deepening UPCR reductions, as well as a reversal of the downward eGFR decline in the placebo switch group. Sustained reductions in hematuria were also observed. The open-label extension showed a favorable safety profile similar to the double-blind period. These results support atacicept 150 mg as a potential disease-modifying treatment for IgAN.

Genetics of IgA nephrology: risks, mechanisms, and therapeutic targets.

IgA nephropathy (IgAN) is a genetically complex multifactorial trait. Over the past decade, population-based genome-wide association studies (GWAS) have identified more than 30 IgAN risk loci, providing novel perspectives on both the epidemiology of the disease and its underlying molecular mechanisms. In addition, the association between IgAN and galactose-deficient IgA1 (Gd-IgA1) presented another avenue for genetic exploration due to the heritability of the elevated serum Gd-IgA1 levels. These endeavors also yielded and enabled refinement of polygenic risk scores, which may help identify specific groups of individuals at significantly increased risks, leading to stratifications of medical treatments. In this review, we aim to explore the existing evidence for genetic causation in IgAN. We summarize the state of genetic research in IgAN and how it has led to the reformulation of the new pathogenesis model and novel therapeutic targets.

Examining the association between serum galactose-deficient IgA1 and primary IgA nephropathy: a systematic review and meta-analysis.

IgA nephropathy (IgAN) is a common primary glomerular disease. The O-glycosylation status of IgA1 plays a crucial role in disease pathophysiology. The level of poorly-O-galactosylated IgA1, or galactose-deficient IgA1 (Gd-IgA1), has also been identified as a potential biomarker in IgAN. We sought to examine the value of serum Gd-IgA1 as a biomarker in IgAN, by investigating its association with clinical, laboratory, and histopathological features of IgAN. The review followed Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) recommendations and was registered in PROSPERO (CRD42021287423). The literature search was conducted in PubMed, Web of Science, Cochrane, and Scopus, and the selected articles were evaluated for eligibility based on predefined criteria. The methodological quality of the studies was assessed using the Newcastle-Ottawa Scale. Statistical analysis was performed to calculate effect sizes and assess heterogeneity among the studies. This review analyzed 29 out of 1,986 studies, conducted between 2005 and 2022, with participants from multiple countries. Gd-IgA1 levels were not associated with age and gender, while associations with hypertension, hematuria, and proteinuria were inconsistent. In the meta-analyses, a correlation between serum Gd-IgA1 and estimated glomerular filtration rate was identified, however, the relationships between Gd-IgA1 levels and chronic kidney disease (CKD) stage and progression to kidney failure were inconsistent. Serum Gd-IgA1 levels were not associated with validated prognostic risk factors, but were negatively correlated with kidney function. Further research in larger studies using standardized assays are needed to establish the value of Gd-IgA1 as a prognostic risk factor in IgAN.

Diagnostic and prognostic value of galactose-deficient IgA1 in patients with IgA nephropathy: an updated systematic review with meta-analysis.

Galactose-deficient IgA1 (Gd-IgA1) is a critical effector molecule in the pathogenesis of IgA nephropathy (IgAN), a leading renal disease without noninvasive assessment options. This updated systematic review aimed to determine the diagnostic and prognostic value of Gd-IgA1 assessment in biological fluids in patients with IgAN. PRISMA guidelines were followed in this review. We searched PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure, China Biology Medicine disc, VIP Information/China Science and Technology Journal Database, and WANFANG for studies published between database inception and January 31, 2023. Eligible studies that evaluated aberrant IgA1 glycosylation in IgAN patients relative to controls were identified, and random effects meta-analyses were used to compare Gd-IgA1 levels in different groups. The quality of the evidence was assessed using the Newcastle-Ottawa Scale. This study was registered on PROSPERO (CRD42022375246). Of the 2727 records identified, 50 were eligible and had available data. The mean Newcastle-Ottawa Scale score was 7.1 (range, 6-8). Data synthesis suggested that IgAN patients had higher levels of blood and/or urine Gd-IgA1 compared with healthy controls (standard mean difference [SMD]=1.43, 95% confidence interval [CI]=1.19-1.68, P<0.00001), IgA vasculitis patients (SMD=0.58, 95% CI=0.22-0.94, P=0.002), and other kidney disease patients (SMD=1.06, 95% CI=0.79-1.33, P<0.00001). Moreover, patients with IgAN had similar levels of serum Gd-IgA1 compared to first-degree relatives (SMD=0.38, 95% CI= -0.04-0.81, P=0.08) and IgA vasculitis with nephritis patients (SMD=0.12, 95% CI= -0.04-0.29, P=0.14). In addition, ten studies demonstrated significant differences in serum Gd-IgA1 levels in patients with mild and severe IgAN (SMD= -0.37, 95% CI= -0.64--0.09, P=0.009). High serum and urine Gd-IgA1 levels suggest a diagnosis of IgAN and a poor prognosis for patients with this immunological disorder. Future studies should use more reliable and reproducible methods to determine Gd-IgA1 levels. https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42022375246, identifier CRD42022375246.

Notoginsenoside R_1 interferes with renal oxidative stress and Nrf2/HO-1 signaling pathway to alleviate kidney injury in mice with IgA nephropathy and its mechanism

The purpose of this study was to investigate the effect of notoginsenoside R_1(NGR_1) on alleviating kidney injury by regulating renal oxidative stress and the Nrf2/HO-1 signaling pathway in mice with IgA nephropathy(IgAN) and its mechanism. The mouse model of IgAN was established using a variety of techniques, including continuous bovine serum albumin(BSA) gavage, subcutaneous injections of carbon tetrachloride(CCl_4) castor oil, and tail vein injections of lipopolysaccharide(LPS). After successful modeling, mice with IgAN were randomly separated into a model group, low, medium, and high-dose NGR_1 groups, and a losartan group, and C57BL6 mice were utilized as normal controls. The model and normal groups were given phosphate buffered saline(PBS) by gavage, the NGR_1 groups were given varying dosages of NGR_1 by gavage, and the losartan group was given losartan by gavage for 4 weeks. The 24-hour urine of mice was collected after the last administration, and serum and kidney tissues of mice were taken at the end of the animal experiment. Then urine red blood cell count(URBCC), 24-hour urine protein(24 h protein), serum creatinine(Scr), and blood urea nitrogen(BUN) levels were measured. The enzyme-linked immunosorbent assay(ELISA) was used to detect the levels of galactose-deficient IgA1(Gd-IgA1), kidney injury molecule 1(Kim-1), and neutropil gelatinase-associated lipocalin(NGAL) in the mouse serum. The assay kits were used to detect the levels of malondialdehyde(MDA) and superoxide dismutase(SOD), and immunofluorescence(IF) was used to detect the expression level of glutathione peroxidase 4(GPX4) in the mesangial region. Western blot was used to detect the protein expression of nuclear transcription factor E2 related factor 2(Nrf2)/heme oxygenase 1(HO-1) signaling pathway in the renal tissue. Hematoxylin-eosin(HE) staining was used to observe pathological alterations in the glomerulus of mice. The results revealed that, as compared with the model group, the serum Gd-IgA1 level, URBCC, 24 h protein level, renal damage markers(Kim-1 and NGAL) in the high-dose NGR_1 group decreased obviously and renal function indicators(BUN, Scr) improved significantly. The activity of SOD activity and expression level of GPX4 increased significantly in the high-dose NGR_1 group, whereas the expression level of MDA reduced and protein expression levels of Nrf2 and HO-1 increased. Simultaneously, HE staining of the renal tissue indicated that glomerular damage was greatly decreased in the high-dose NGR_1 group. In conclusion, this study has clarified that NGR_1 may alleviate the kidney injury of mice with IgAN by activating the Nrf2/HO-1 signaling pathway, improving antioxidant capacity, and reducing the level of renal oxidative stress.

COSMC expression as a predictor of remission in IgA nephropathy.

The impact of core 1,3-galactosyltransferase-specific molecular chaperon (COSMC) gene expression and methylation profile on clinical progression of IgA nephropathy (IgAN) is unclear. The aim of this study was to determine the clinical significance and the relation of the COSMC gene expression and methylation pattern with the progression of IgAN. Thirty-nine biopsy-confirmed IgAN patients, 11 healthy relatives and 20 healthy controls were recruited. The COSMC mRNA levels and methylation profile of COSMC gene promoter were measured using the quantitative real-time PCR. The galactose-deficient IgA1 (Gd-IgA1) levels were measured using ELISA in serum and cell culture supernatant. The effect of IL-4 and AZA on COSMC expression and methylation and the correlation of COSMC gene expression and methylation levels with baseline kidney function tests, histology and long-term outcomes were examined. The mean COSMC mRNA level was significantly lower, and serum Gd-IgA1 level was higher in IgAN patients compared with the control groups (p < 0.001, and p = < 0.001, respectively). The COSMC mRNA levels were correlated with intensity of hematuria (r = -0.41, p = 0.009), serum creatinine level (r = -0.37, p = 0.002) and eGFR (r = 0.36, p = 0.002). The COSMC methylation levels were correlated with age (r = 0.25, p = 0.04) and baseline eGFR (r = -0.326, p = 0.006). Twenty IgAN patients (51.3%) reached to complete (5, 12.8%) or partial remission (15, 38.5%) after a median of 34.5months (IQR, 13.75-71). In multivariable Cox regression analysis, COSMC mRNA expression (adjusted HR (aHR) 1.871, 95% CI 1.287-2.722, p = 0.001) and Oxford T score (aHR 0.355, 95% CI 0.146-0.859, p = 0.022) predicted the remission. COSMC mRNA level is a novel biomarker candidate to predict the remission in IgAN patients.

Oxidative stress and macrophage infiltration in IgA nephropathy.

The aim of this study wasto evaluate the interactions among serum levels of galactose-deficient IgA1 (Gd-IgA1), oxidative stress and macrophage infiltration and their clinical correlates in patients with IgA Nephropathy (IgAN). A total of 47 patients with biopsy-proven primary IgAN, aged between 16 and 79 years,with a follow-up period ≥ 1 year or whoshowed progression to end stage kidney disease (ESKD) regardless the duration of follow-up were included. Study endpoint was the progression to ESKD. Serum Gd-IgA1 and advanced oxidation protein product (AOPP) levels were measured using ELISA assays. Kidney biopsies were evaluated according to the Oxford MEST-C scoring, withC4d and CD68 staining. Seventeen patients (36%) experienced ESKD during a median follow-up time of 6 years (IQR 3.7-7.5). Serum AOPP levels were correlated with the intensity of glomerular C3 deposition (r = 0.325, p = 0.026), glomerular (r = 0.423, p = 0.003) and interstitial CD68 + cell count (r = 0.298, p = 0.042) and Gd-IgA1 levels (r = 0.289, p = 0.049). Serum Gd-IgA1 levels were correlated withthe intensity of C3 deposition (r = 0.447, p = 0.002). eGFR at biopsy (adjusted HR (aHR) 0.979 p = 0.011), and E score (aHR, 8.305, p = 0.001) were associated with progression to ESKD in multivariate analysis. 5-year ESKD-free survival rate was significantly lower in patients with higher E score compared to patients with E score 0 [p = 0.021]. An increased number of macrophages in the glomerular and tubulointerstitial area may play arole in oxidative stress and complement system activation. Endocapillary hypercellularity is a predictive factor for poor prognosis in IgAN.

Clinical significance of serum galactose-deficient immunoglobulin A1 for detection of recurrent immunoglobulin A nephropathy in kidney transplant recipients.

BackgroundRecurrent glomerulonephritis (GN) is a common cause of allograft loss in kidney transplantation (KT), the most frequent of which is immunoglobulin A (IgA) nephropathy (IgAN). Galactose-deficient IgA1 (Gd-IgA1) plays a major role in the pathophysiology of IgAN, but the association between Gd-IgA1 and recurrent IgAN in kidney transplant recipients (KTRs) is uncertain. We aimed to evaluate the efficacy of Gd-IgA1 for prediction of recurrent IgAN and graft and patient survival according to Gd-IgA1 level.MethodsWe enrolled 27 KTRs who underwent allograft biopsy between 2009 and 2016 and measured the serum Gd-IgA1 level of each KTR. We divided the patients into two groups: nonrecurrent IgAN (patients with IgAN prior to KT who were not diagnosed with recurrent IgAN) and recurrent IgAN (patients with IgAN prior to KT who were diagnosed with recurrent IgAN).ResultsThe mean serum Gd-IgA1 level was significantly higher in the recurrent IgAN group than in the nonrecurrent IgAN group (6,419 ± 3,675 ng/mL vs. 3,381 ± 2,844 ng/mL, p = 0.02). The cutoff value of serum Gd-IgA1 in receiver operating characteristic curve analysis was 4,338 ng/mL (area under the curve, 0.76; 95% confidence interval [CI], 0.57–0.95, p = 0.02). Serum Gd-IgA1 level was an independent factor for recurrent IgAN (odds ratio, 17.60; 95% CI, 1.33–233.03, p = 0.03). There was no significant difference in graft or patient survival between the two groups.ConclusionSerum Gd-IgA1 can be used as a diagnostic biomarker for recurrent IgAN in KT.

POS-388 Role Of Serum Galactose Deficient IgA1 As A Noninvasive Biomarker For Diagnosis Of IgA Nephropathy And Its Role In Assessing The Genetic Susceptibility Of Disease

IgA nephropathy(IgAN) is the most common primary glomerular disease with a high risk of progression. Over the years, research has focused on establishing a biomarker for this disease. Galactose deficient IgA1 (Gd-IgA1) is a crucial molecule in the pathogenesis of IgAN and serum levels have found high in previous studies. So this molecule may have potential to be used as a biomarker for IgAN . Aberrant galactosylation of IgA1 could be inherited and family members are predisposposed for the diseaseAims : To determine whether serum Gd-IgA1 levels can be used as a noninvasive biomarker for diagnosis of IgAN. To assess the serum Gd-IgA1 levels in the first degree relatives of patients with IgAN to predict possible heritability of aberrant galactosylation of IgA1.To correlate serum Gd-IgA1 levels with disease severity by clinical and histological parameters We measured serum Gd-IgA1 levels using a non- lectin based enzyme linked immunoassay (ELISA) in 40 biopsy proved IgAN patients and 38 healthy controls. In control group (n=38) we included 18 healthy first degree relatives of IgAN patients.Quantification of Gd-IgA1from patients sample were carried out by using optical density (OD) reading obtained from each sample and comparing with each graph.Receiver operating characteristic (ROC) curve was drawn for serum Gd-IgA1 levels and optimum cut off was determined. Area under the curve (AUC) and 95% confidence interval (CI) for AUC was estimated. Diagnostic validity of serum Gd-IgA1 levels test was determined by sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV). Efficiency, likelihood ratio for a positive result (LR+) and likelihood ratio for a negative result (LR-) were also calculated Mean serum Gd-IgA1 levels were higher in IgAN patients (n=40) 1631.9.±1997.5ng/ml compared with healthy controls (n=38) 429.81.± 571.28 ng/ml.Median (min, max) values were 629 (104.48, 7959.1) and 285.78(18.44, 3152.9) respectively (p<0.0001).Considering a cut-off value of serum Gd-IgA1 ≥ 454.8 ng/ml, the sensitivity for diagnosing IgAN compared to healthy controls without family history (n=20) was 75.3% and specificity 85 % with a positive predictive value of 90.9 % and negative predictive value of 63 % .The area under the curve (AUC) was 0.85 ( 0.749- 0.951 ), p<0.0001 . Efficiency of test was 78.1% , likelihood ratio for a positive result ( LR+) was 5 and likelihood ratio for a negative result ( LR-) was 0.29. When IgAN patients were compared with total controls(n=38) for the same cut off, sensitivity was same with specificity of 71.7 %, positive predictive value of .73.2 % and negative predictive value of 73%. Serum Gd-IgA1 levels in healthy controls with family history were significantly high compared to those without family history (384.12ng/mlvs.202 .81ng/ml, p=0.022) The serum Gd-IgA1 level did not correlate with clinical or histological disease severity parameters Serum Gd-IgA1 level can be used as a potential biomarker for diagnosis of IgAN . High levels of Gd-IgA1 levels in the first degree relatives of patients with IgAN suggests possible heritability of aberrant galactosylation of IgA1 and may predict risk of disease manifestation after a second hit in future. Serum Gd-IgA1 level can’t be used to assess disease severity

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.

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.

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.

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.

过敏性紫癜患者B淋巴细胞Cosmc、T-合酶mRNA的表达与血清低半乳糖基化IgA1水平检测

过敏性紫癜患者B淋巴细胞Cosmc、T-合酶mRNA的表达与血清低半乳糖基化IgA1水平检测

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.