The impact of mild and moderate COVID-19 infection on the progression of kidney dysfunction in patients with IgA nephropathy.

Background: Previous research indicates that coronavirus disease 2019 (COVID-19) infection may have a role in triggering immunoglobulin A (IgA) nephropathy. However, limited research has explored the clinical implications of COVID-19 infection in individuals already diagnosed with IgA nephropathy. This study aimed to determine whether COVID-19 infection independently affects the subsequent trajectory of kidney function in IgA nephropathy patients. Methods: This was a single-center cohort study. The study included 199 patients diagnosed with IgA nephropathy. The COVID-19 infection status was determined using a combined method: a questionnaire and the Health Code application, both administered at the end of 2022 in northern China. Kidney function trajectory was assessed by the estimated glomerular filtration rate (eGFR), calculated based on serum creatinine levels measured during follow-up outpatient visits. The primary endpoint of interest was the eGFR trajectory. Results: Out of the 199 participants, 75% (n = 181) reported a confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, determined through antigen or polymerase chain reaction tests, accounting for 79% (n = 143) of the infected patients. A significant majority (98%) experienced mild to moderate symptoms. Over a median follow-up period of 10.7 months post-COVID-19 infection, notable clinical events included gross hematuria in 30 patients (16.6%), which normalized within an average of 3 days. Additionally, a 2-fold increase in proteinuria or progression to the nephrotic range was observed in 10 individuals (5.5%). No cases of acute kidney injury were noted. COVID-19 exposure was associated with an absolute change in eGFR of 2.98 mL/min/1.73 m2 per month (95% confidence interval 0.46 to 5.50). However, in a fully adjusted model, the estimated changes in eGFR slope post-COVID-19 were -0.39 mL/min/1.73 m2 per month (95% confidence interval -0.83 to 0.06, P = .088) which included the possibility of no significant effect. Notably, a higher rate of kidney function decline was primarily observed in patients with a baseline eGFR <45 mL/min/1.73 m2 [-0.56 mL/min/1.73 m2 (-1.11 to -0.01), P = .048]. In the cohort, there were few instances of severe COVID-19 cases. The absence of long-term follow-up outcomes was observed. Conclusions: Overall, mild to moderate COVID-19 infection does not appear to significantly exacerbate the subsequent decline in kidney function among IgA nephropathy patients, particularly in those with preserved baseline kidney function.

Combined Genetic Association and Differed Expression Analysis of UBE2L3 Uncovers a Genetic Regulatory Role of (Immuno)proteasome in IgA Nephropathy.

Introduction: IgA nephropathy (IgAN) is a leading cause of end-stage renal disease. The exact pathogenesis of IgAN is not well defined, but some genetic studies have led to a novel discovery that the (immuno)proteasome probably plays an important role in IgAN. Methods: We firstly analyzed the association of variants in the UBE2L3 region with susceptibility to IgAN in 3,495 patients and 9,101 controls, and then analyzed the association between lead variant and clinical phenotypes in 1,803 patients with regular follow-up data. The blood mRNA levels of members of the ubiquitin-proteasome system including UBE2L3 were analyzed in peripheral blood mononuclear cells from 53 patients and 28 healthy controls. The associations between UBE2L3 and the expression levels of genes involved in Gd-IgA1 production were also explored. Results: The rs131654 showed the most significant association signal in UBE2L3 region (OR: 1.10, 95% CI: 1.04-1.16, p = 2.29 × 10-3), whose genotypes were also associated with the levels of Gd-IgA1 (p = 0.04). The rs131654 was observed to exert cis-eQTL effects on UBE2L3 in various tissues and cell types, particularly in immune cell types in multiple databases. The UBE2L3, LUBAC, and proteasome subunits were highly expressed in patients compared with healthy controls. High expression levels of UBE2L3 were not only associated with higher proteinuria (r = 0.34, p = 0.01) and lower eGFR (r = -0.28, p = 0.04), but also positively correlated with the gene expression of LUBAC and other proteasome subunits. Additionally, mRNA expression levels of UBE2L3 were also positively correlated with IL-6 and RELA, but negatively correlated with the expression levels of the key enzyme in the process of glycosylation including C1GALT1 and C1GALT1C1. Conclusion: In conclusion, by combined genetic association and differed expression analysis of UBE2L3, our data support a role of genetically conferred dysregulation of the (immuno)proteasome in regulating galactose-deficient IgA1 in the development of IgAN.

Hepatitis B Virus Status and Clinical Outcomes in IgA Nephropathy.

Introduction: Immunoglobulin A nephropathy (IgAN) has been reported to coexist with hepatitis B virus (HBV) infection. Despite the clinical significance of this association, there is a lack of comprehensive research investigating the impact of various common conditions following HBV infection and the potential influence of anti-HBV therapy on the progression of IgAN. Methods: We investigated 3 distinct states of HBV infection, including chronic HBV infection, resolved HBV infection, and the deposition of hepatitis B antigens in renal tissue, in a follow-up database of 1961 patients with IgAN. IgAN progression was defined as a loss of estimated glomerular filtration rate (eGFR) >40%. Multivariable cause-specific hazards models to analyze the relationship between HBV states and IgAN progression. Results: Chronic HBV infection was identified as an independent risk factor for IgAN progression, supported by both prematching analysis (hazard ratio [HR], 1.61; 95% confidence interval [CI], 1.06-2.44; P = 0.024) and propensity-score matching analysis (HR, 1.74; 95% CI 1.28-2.37; P < 0.001). Conversely, resolved HBV infection showed no significant association with IgAN progression (HR, 1.01; 95% CI 0.67-1.52; P = 0.969). Moreover, the presence of HBV deposition in the kidneys and the utilization of anti-HBV therapy did not appear to be significant risk factors for renal outcomes (P > 0.05). Conclusion: Chronic HBV infection is an independent risk factor for IgAN progression, whereas resolved HBV infection is not. In patients with IgAN, management of concurrent chronic HBV infection should be enhanced. The presence of HBV deposition in the kidneys and the use of anti-HBV medications do not impact the kidney disease progression in patients with IgAN with concurrent HBV infection.

Unveiling biomarkers and therapeutic targets in IgA nephropathy through large-scale blood transcriptome analysis.

INTRODUCTION: IgA nephropathy (IgAN) is the most prevalent form of glomerulonephritis. Unfortunately, molecular biomarkers for IgAN derived from omics studies are still lacking. This research aims to identify critical genes associated with IgAN through large-scale blood transcriptome analysis. METHODS: We constructed novel blood transcriptome profiles from peripheral blood mononuclear cells (PBMCs) of 53 Chinese IgAN patients and 28 healthy individuals. Our analysis included GO, KEGG, and GSEA for biological pathways. We analyzed immune cell profiles with CIBERSORT and constructed PPI networks with STRING, visualized in Cytoscape. Key differentially expressed genes (DEGs) were identified using CytoHubba and MCODE. We assessed the correlation between gene expressions and clinical data to evaluate clinical significance and identified hub genes through machine learning, validated with an open-access dataset. Potential drugs were explored using the CMap database. RESULTS: We identified 333 DEGs between IgAN patients and healthy controls, mainly related to immune response and inflammation. Key pathways included NK cell mediated cytotoxicity, complement and coagulation cascades, antigen processing, and B cell receptor signaling. Cytoscape revealed 16 clinically significant genes (including KIR2DL1, KIR2DL3, VISIG4, C1QB, and C1QC, associated with sub-phenotype and prognosis). Machine learning identified two hub genes (KLRC1 and C1QB) for a diagnostic model of IgAN with 0.92 accuracy, validated at 1.00 against the GSE125818 dataset. Sirolimus, calcifediol, and efaproxiral were suggested as potential therapeutic agents. CONCLUSION: Key DEGs, particularly VISIG4, KLRC1, and C1QB, emerge as potential specific markers for IgAN, paving the way for future targeted personalized treatment options.

A cluster of type I interferon-regulated genes associates with disease activity and prognosis in patients with IgA nephropathy.

The exact pathogenesis of IgA nephropathy (IgAN) is complex and so far, not well defined. Since it has been shown that microbial infections could induce high levels of type I interferon (IFN-I) and there is an evident link between mucosal infection and gross hematuria in IgAN, we hypothesized that IFN-I may play a role in the pathogenic process. In this study, we investigated the type I interferon status in IgAN based on the expression of 17 IFN-regulated genes (IRGs) in whole blood from 59 IgAN patients in a cross-sectional study, of which 34 patients followed longitudinally. Analysis of the IFN-score showed that there was a significant elevated IFN-score in the IgAN patients compared with healthy controls (n = 28, p = 9.80 × 10-3), and we observed an elevated IFN-score in the group with less tubular atrophy/interstitial fibrosis (p = 1.07 × 10-2) and with a lower proportion of mesangial hypercellularity (p = 1.23 × 10-2). In the longitudinal analysis, Cox regression analysis revealed that a higher IFN level was associated with a better renal outcome in IgAN after adjustments for gender and age (hazard ratio, 0.90; 95 % confidence interval, 0.81 to 0.97; p = 4.20 × 10-2). In conclusion, our finding suggested that IFN score may represent a novel type of biomarker in IgAN, which requires further exploration on its mechanism and therapeutic targeting.

Time-Varying Proteinuria and Progression of IgA Nephropathy: A Cohort Study.

RATIONALE & OBJECTIVE: Proteinuria is a surrogate end point for predicting long-term kidney outcomes in IgA nephropathy (IgAN) with levels<1g/day identified as a therapeutic target. However, this threshold has not been sufficiently studied. We quantified the associations of progression of IgAN with various levels of proteinuria. STUDY DESIGN: Observational cohort study. SETTING & PARTICIPANTS: 1,530 patients with IgAN and at least 12 months of follow-up at Peking University First Hospital. EXPOSURE: Proteinuria levels updated over time (time-varying proteinuria, TVP). OUTCOME: A composite kidney outcome of a 50% reduction in the estimated glomerular filtration rate or end-stage kidney disease. ANALYTICAL APPROACH: Marginal structural models. RESULTS: After a median follow-up period of 43.5 (IQR, 27.2-72.8) months, 254 patients (16.6%) developed the composite kidney outcome. A graded association was observed between TVP and composite kidney outcomes with higher risk among those with proteinuria of≥0.5g/day. Compared with TVP<0.3g/day, the HRs for proteinuria levels of 0.3 to<0.5g/day, 0.5 to<1.0g/day, 1.0 to<2.0g/day, and≥2.0g/day were 2.22 (95% CI, 0.88-5.58), 4.04 (95% CI, 1.93-8.46), 8.46 (95% CI, 3.80-18.83), and 38.00 (95% CI, 17.62-81.95), respectively. The trend was more pronounced in patients with baseline proteinuria of≥1.0g/day, among whom a higher risk was observed with TVP of 0.3 to<0.5g/day compared with TVP<0.3g/day (HR, 3.26 [95% CI, 1.07-9.92], P=0.04). However, in patients with baseline proteinuria levels of<1g/day, the risk of composite kidney outcome only began to increase when TVP was≥1.0g/day (HR, 3.25 [95% CI, 1.06-9.90]). LIMITATIONS: Single-center observational study, selection bias, and unmeasured confounders. CONCLUSIONS: This study showed that patients with IgAN and proteinuria levels of>0.5g/day, have an elevated risk of kidney failure especially among patients with proteinuria levels≥1.0g/day before initiating treatment. These data may serve to inform the selection of proteinuria targets in the treatment of IgAN. PLAIN-LANGUAGE SUMMARY: The presence of proteinuria has often been considered a surrogate end point and a possible therapeutic target in clinical trials in IgA nephropathy (IgAN). Some guidelines recommend a reduction in proteinuria to<1g/day as a treatment goal based on the results of previous longitudinal studies. However, these findings may have been biased because they did not properly adjust for time-dependent confounders. Using marginal structural models to appropriately account for these confounding influences, we observed that patients with IgAN and proteinuria levels≥0.5g/day have an elevated risk of kidney failure, especially among patients who had proteinuria levels of≥1.0g/day before initiating treatment. These data may serve to inform the selection of proteinuria targets in the treatment of IgAN.