Renal Activity Index Research Articles

V-set immunoglobulin domain-containing protein 4 (VSIG4) as a potential non-invasive biomarker of lupus nephritis

Abstract Objective: This study aimed to identify a non-invasive biomarker of lupus nephritis (LN) for diagnosis, disease monitoring or flare prediction of LN. Methods: Both the VSIG4 free form and immune complex (ICx) bound form in the urine of LN patients (N = 97) were examined using ELISA, to compare with chronic kidney diseases (CKD) controls and healthy controls. Immunohistochemistry was used to confirm the elevated tissue expression of VSIG4 in the renal biopsy of LN. Immunofluorescence was used to examine the VSIG4-mediated immune complex deposition in the kidney of LN. Results: The urinary levels of both VSIG4 free form (P = 0.01) and VSIG4-ICx (P = 6.3 x 10-14) and were significantly elevated in LN patients, particularly in renal active LN (P = 4.8 x 10-16) compared to healthy controls. VSIG4-ICx effectively discriminated HC from LN (AUC = 0.84, P< 0.01) and active LN from inactive LN (AUC = 0.91, P< 0.01). The urinary immune complex form of VSIG4 was positively correlated with renal pathology activity index (AI). Immunohistochemistry highlighted the significantly elevated VSIG4 expression in both glomeruli and tubules in LN patients, compared to healthy controls. Conclusion: Our findings underscore the diagnostic potential of VSIG4 as a non-invasive urinary biomarker for LN. With its correlation to disease activity and renal pathology, VSIG4 presents a promising avenue for enhanced diagnosis and monitoring of lupus nephritis, paving the way for improved patient care.

Risk factors and prognosis of pediatric silent lupus nephritis with class Ⅲ to Ⅴ

To study the risk factors and prognostic characteristics of pediatric silent lupus nephritis (SLN) with class Ⅲ to V. A retrospective study was conducted to collect clinical data from 30 children diagnosed with SLN at the Department of Pediatrics, Second Xiangya Hospital, Central South University, from May 2007 to April 2023. Based on renal pathological classification, the patients were divided into a class Ⅱ group (12 cases) and a class Ⅲ to Ⅴ group (18 cases). The risk factors for the occurrence of class Ⅲ to Ⅴ SLN were analyzed, and the prognostic characteristics were summarized. Among the 30 SLN patients, the median follow-up time was 61.50 months. There were no statistically significant differences in the proportions of patients who discontinued glucocorticoids or achieved low disease activity status, nor in the annual decline rate of estimated glomerular filtration rate (eGFR) between the class Ⅱ and class Ⅲ to V groups (P>0.05). However, three patients in the class Ⅱ group progressed to stage 1 chronic kidney disease (CKD), while eight patients in the class III to V group reached stage 1 CKD, and four patients reached stage 2 CKD. Among the 26 female SLN patients, serum complement C3 levels in the class III to V group were lower than those in the class Ⅱ group (P<0.05). Serum C3 levels in SLN patients, as well as in female SLN patients, were negatively correlated with the fluorescence intensity of IgA, IgG, and C3 immune complexes in the kidneys (P<0.05). Additionally, serum C3 levels in female SLN patients were negatively correlated with the renal pathological activity index (P<0.05). Binary logistic regression analysis indicated that being female and having low serum complement C3 levels were risk factors for the occurrence of class Ⅲ to V SLN in children (P<0.05). Class Ⅲ to V SLN is not uncommon among SLN children, and there remains a risk of long-term renal function progression. Being female and having low serum complement C3 levels are identified as risk factors for class Ⅲ to V SLN in children.

Association of Mitochondrial Pyruvate Carrier with the Clinical and Histological Features in Lupus Nephritis.

Mounting evidence suggests that mitochondrial dysfunction contributes to lupus nephritis (LN) pathogenesis. Mitochondrial pyruvate carrier 1 (MPC1) and mitochondrial pyruvate carrier 2 (MPC2) mediating pyruvate transport from the cytoplasm to the mitochondrial matrix, determines the cell survival and cellular energy supply. Here, we aimed to investigate the association of mitochondrial pyruvate carrier expression with the clinical and histological features in LN. Patients with biopsy-proven proliferative LN (class III and class IV, n=18) and membranous LN (class V, n=18) were included. Expression of MPC1 and MPC2 were examined by immunohistochemistry. MPC protein levels in the two groups were evaluated by the Student's t-test. Correlation analysis between MPC levels and clinicopathological features was performed by Spearman's rank correlation. Both MPC1 and MPC2 were exclusively expressed in renal tubules of enrolled LN. Significantly lower MPC1 and MPC2 were observed in patients with proliferative LN compared to membranous LN. In addition, the MPC1 and MPC2 were negatively correlated with SLEDAI-2K score, renal function, and renal pathology activity index. Both MPC1 and MPC2 were localized in renal tubules, and decreased MPC content was more pronounced in proliferative LN than membranous LN. MPC levels were significantly correlated with renal functions and renal pathology activity.

Symposium 1

Proteomics has been a very informative tool in uncovering several biomarkers that may have clinical utility in managing patients with lupus nephritis (LN). Both non-targeted (mass spectrometry-based) and targeted (ligand-based) proteomics point to promising biomarkers in the urine of LN patients. Aptamer-based interrogation of 1129 proteins using the Somascan platform, followed by ELISA-validation in two independent cohorts has indicated that the urine proteins that best distinguish active LN from controls were ALCAM, PF-4, properdin, and VCAM-1 among African Americans, E-selectin, VCAM-1, BFL-1 and Hemopexin among Caucasians, and ALCAM, VCAM-1, TFPI and PF-4 among Asians (PMID: 32366845). Most of these urine proteins correlate significantly with disease activity indices and surpass conventional metrics in identifying active LN. Several elevated urinary molecules are also expressed within LN kidneys, based on single-cell RNA-seq analysis. Of these, ALCAM has been validated in a large multi-ethnic, multi-national cohort of LN subjects, and has also been shown to be a pathogenic driver and therapeutic target in LN (PMID: 34981775). Antibody array based screening of 1000 proteins using the Raybiotech Kiloplex platform has identified urine L-selectin, Angptl4, TGF[Formula: see text] 1, TPP1, TSP-1, FOLR2, PDGFR[Formula: see text], and PRX2, as markers of active renal lupus, outperforming conventional metrics, with L-selectin, Angptl4 and TGF[Formula: see text] 1 tracking well with concurrent or pending disease flares in LN (PMID: 32651195). Of these, urine L-selectin has been validated in large multi-ethnic/national cohorts of LN subjects (under review). Proteomic screens of LN urine using an electrochemiluminescence platform (Mesoscale/MSD) has identified IL-7, IL-12p40, IL-15, IP-10, and TARC as markers of active renal lupus that correlated significantly with disease activity (PMID: 30618193). Very recent global proteomic screens of LN urine using a proximity ligation assay platform from Olink has added several additional biomarker candidates that have been successfully ELISA-validated (under review). Given the plethora of urine biomarkers that have been identified using proteomics, it now becomes important to validate the clinical utility of these urine proteins, using multiple well-annotated patient cohorts, across ethnicities. Among the completed studies, we now know that some urine proteins are diagnostic of concurrent renal pathology LN Class or Activity Index or Chronicity index (e.g. CD163: PMID: 32351512; VCAM-1: PMID: 29076253; Angiostatin: PMID: 29076253; Hemopexin, Kim-1 and Lipoxcalin-2/NGAL; Renin and SAP; PMID: 20065116), while others exhibit prognostic value (e.g., ALCAM and VCAM-1; PMID: 31722419). Ongoing studies also show that most of the urine proteins interrogated in LN are not elevated in circulation (PMID: 36091001), but are expressed within LN kidneys, as ascertained by immunohistochemistry (Clinical Immunology, 2022) and Imaging Mass Cytometry (Tissue CyTOF). To facilitate monitoring of urinary biomarkers in outpatient clinics or to enable self-monitoring of disease status by the patient from the comfort of one’s home, we have recently engineered a smartphone-readable nanophosphor-based lateral flow assay for point of care monitoring of urine ALCAM (Frontiers in Immunology, 2022). The long-term goal is to decipher the clinical utility of different urine biomarkers in managing lupus and LN in the clinics, to empower LN patients with easy-to-use tools to monitor their own disease status, and to understand the mechanistic significance of the uncovered molecules in renal disease pathogenesis. Ongoing research on this front is summarized at: https://mohanlab.bme.uh.edu/ .

Increased formation of neutrophil extracellular traps induced by autophagy and identification of autophagy-related biomarkers in systemic lupus erythematosus.

Abnormal death of neutrophils and the subsequent ineffective clearance of cell fragments result in production of autoantigens that can lead to systemic lupus erythematosus (SLE). Excessive formation of neutrophil extracellular traps (NETs) can trigger the synthesis of pro-inflammatory cytokines such as type I interferons, leading to tissue damage and immune dysfunction in SLE patients. In this study, we found that a decrease in neutrophil counts in the peripheral blood was correlated with clinical parameters in SLE patients. Patients with low neutrophil counts had high renal activity index and chronicity index scores. NET formation and neutrophil autophagy in SLE patients were increased. The autophagy inhibitor hydroxychloroquine was shown to restrict NET formation. Using comprehensive bioinformatics analysis, we found that the expression of the autophagy-related gene, hypoxia-inducible factor 1A (HIF1A), was enhanced in peripheral neutrophils and in the renal glomeruli in SLE patients. Targeting HIF1A could be a potential therapeutic approach for SLE.

Anti-C1q antibodies in lupus nephritis children with glomerular microthrombosis.

Glomerular microthrombosis (GMT) was a common vascular lesion in patients with lupus nephritis (LN). The objective of this study was to investigate the relationship between serum anti-beta2-glycoprotein I antibodies (a-β2GP1) and anti-complement 1q antibodies (a-C1q) antibodies and to investigate the possible mechanism of GMT in children with LN. The subjects were 191 children with LN diagnosed by renal biopsy in our hospital from January 2017 to January 2020. The patients were divided into GMT group and non-GMT group. The clinical manifestations, laboratory tests, renal pathology, prognosis of the two groups and the relationship between a-β2GP1 and a-C1q antibodies were observed. In 191 children with LN, 52 cases (27.23%) presented with GMT. The value of C3, haemoglobin (Hb), estimate glomerular filtration rate (eGFR) and anticardiolipin antibody (ACA) in GMT group were lower than that of non-GMT group (p < .05, p < .01). The value of serum creatinine (Scr), 24 h proteinuria (PRO), urine red blood cells (RBC), N-acetyl-β-d-glucosidase (NAG) and retinol-binding protein (RBP), a-C1q, a-β2GP1, Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) and renal histopathological activity index (AI) score in GMT group were higher than that of non-GMT group (p < .05, p < .01). The positive proportions of serum a-C1q and a-β2GP1 in GMT group were higher than those in non-GMT group (p < .05). According to Spearman correlation analysis, a-C1q was positively correlated with AI score, SLEDAI, a-β2GP1, GMT, LN-III and LN-IV. Hb, eGFR and a-C1q Ab were associated with the formation of GMT in children with LN. The complete proteinuria remission and renal survival in GMT group were significantly lower than those in non-GMT group (p < .05, p < .01). LN children with GMT had more severe clinical manifestations and renal pathologic damages, and poor outcome. Serum a-C1q level was positively correlated with a-β2GP1, and a-β2GP1 may be involved in the formation of GMT in children with LN, which might involve in the activation of complement classical pathway.

The ratio of neutrophil to lymphocyte as a potential marker of clinicopathological activity for lupus nephritis.

The ratio of neutrophil to lymphocyte (NLR) is a novel inflammatory factor that is elevated in systemic lupus erythematosus (SLE). However, the relationship between NLR and renal pathological manifestations in patients with lupus nephritis (LN) has not been investigated. A retrospective study included 240 SLE patients, in which 186 patients with renal involvement and 124 LN patients underwent renal biopsy, 125 healthy volunteers and 125 chronic kidney disease (CKD) controls. Patients with SLE disease activity 2000 (SLEDAI-2K) > 9 and ≤ 9 were defined as severely active and mildly active, respectively. Clinical parameters and renal pathological data were collected from medical records. The correlations between NLR and clinicopathological features were analyzed. The NLR of SLE group was significantly higher than that of the sex-age matched control groups. Patients with nephritis had higher NLR levels than those without nephritis (P = 0.044). Increased NLR was observed in severely active group compared to mildly active group (P = 0.020). NLR was significantly positively related with SLEDAI score, Renal SLEDAI score, C-reactive protein (CRP), 24-h urine protein, renal activity index (AI), cellular crescents and tubular atrophy, and negatively correlated with serum albumin. NLR was significantly decreased after treatment. Based on the receiver operating characteristic (ROC) curve, the best NLR cut-off value to predict severe activity of SLE and cellular crescents in renal pathology was 2.19 and 3.16, respectively. NLR may be a non-invasive and potential inflammatory marker in evaluating clinical and renal pathological activity in LN patients.

V-Set Immunoglobulin Domain-Containing Protein 4 as a Novel Serum Biomarker of Lupus Nephritis and Renal Pathology Activity.

To discover novel serum biomarkers that have diagnostic or predictive value in lupus nephritis (LN). Using a quantitative protein microarray, we screened for high-abundant proteome expression in the serum of patients with LN compared to healthy controls. Top candidates from this screening were validated using a larger cohort of patients with LN compared to a disease control cohort (subjects with other chronic kidney diseases) and a healthy control cohort. Promising markers were then selected using a machine-learning model and further validated with a larger patient cohort. The corresponding autoantibodies and immune complexes containing these proteins were also examined. In total, 13 proteins were found to be significantly elevated in LN patient serum in the screening, among which 8 proteins were validated by enzyme-linked immunosorbent assay using 81 serum samples from LN patients and control subjects. Three serum markers with LN diagnostic potential were identified using feature importance analysis and further validated using 155 serum samples from LN patients and control subjects. V-set immunoglobulin domain-containing protein 4 (VSIG4) appeared to be the most promising marker in distinguishing LN from healthy controls, with an area under the curve of 0.93. VSIG4 could also discriminate active LN from inactive LN. Furthermore, serum VSIG4 levels were positively correlated with all of the following clinical parameters: the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score (Spearman's rank correlation rs = 0.42, P < 0.001), the renal domain score of the SLEDAI (rs = 0.46, P < 0.001), the urinary protein-to-creatinine ratio (rs = 0.56, P < 0.001), and the serum creatinine level (rs = 0.41, P < 0.001). Importantly, we found that serum VSIG4 levels tracked with LN disease activity longitudinally, and that serum VSIG4 levels reflected the renal pathology activity index (AI), particularly the AI components of crescent formation and hyaline deposits. VSIG4 may be a promising novel serum biomarker and therapeutic target in patients with LN.

#5383 THE PREDICTIVE VALUE OF URINARY CONGOPHILIA AS A BIOMARKER IN PREGNANT AND NON-PREGNANT WOMEN WITH LUPUS NEPHRITIS

Abstract Background and Aims Endoplasmic reticulum (ER) stress with protein misfolding has been introduced as a key pathogenetic mechanism in patients with lupus nephritis (LN). Pregnancy is thought to exaggerate ER stress in conjunction with autophagy inhibition. This probably explains disease flares during pregnancy; however, this is not fully addressed. The detection of the abnormally misfolded proteins is made using the Congo red stain, which is referred to as congophilia. This study aimed to assess the predictive value of urinary congophilia as a marker of protein misfolding in pregnant and non-pregnant women with lupus nephritis. Method Urine samples from non-pregnant lupus nephritis patients (n = 45) and pregnant women with lupus nephritis (n = 12), as well as pregnant healthy controls (n = 38) were collected. Urinary congophilia was assessed by Congo Red Dot Blot assay. The disease activity was defined according to SLE Disease Activity Index (SLEDAI) criteria. Renal biopsy was done for 26 adults of non-pregnant lupus nephritis patients at time of urine sampling as it was clinically indicated and modified NIH activity index was assessed. Results The median and range values for SLEDAI score were 14(4-34) for non-pregnant LN patients, and 4(0-6) for pregnant women with LN (Table 1). Congo red retention (CRR) was significantly higher for non-pregnant LN patients (24.18%(0.75-126.29%)), in comparison with pregnant LN patients (0.67%(0.31-27.69%), P = 0.001), and healthy controls (0.33%(0.18-2.7%), P≤0.001). There was a significant positive correlation between CRR on one hand, and anti-ds-DNA (r = 0.791, P≤0.001), as well as SLEDAI score (r = 0.623, P≤0.001) on the other hand. However, no significant correlation has been found between CRR with renal histopathological activity index (r = 0.2, P = 0.425). CRR at a cut point ≥ 21.85% had 83% sensitivity, and 58% specificity to capture high LN activity status (NIH-AI &amp;gt;10) versus lower LN activity status (Fig. 1). Conclusion Urinary congophilia may add a diagnostic value in patients with lupus nephritis and can be a reliable marker of disease activity. CRR is related to disease activity rather than pregnancy.

Renal C4d is a potential biomarker of disease activity and severity in pediatric lupus nephritis patients.

Systemic lupus erythematosus (SLE), a multisystemic autoimmune disease, is very aggressive in pediatric-onset patients as they are prone to develop lupus nephritis (LN). Although renal C4d positivity is correlated with the activity of renal disease and SLE in adult-onset LN patients, available information for pediatric-onset patients is limited. To evaluate the potential diagnostic significance of renal C4d staining in pediatric LN patients, we retrospectively detected C4d staining by immunohistochemistry on renal biopsy specimens from 58 pediatric LN patients. The clinical and laboratory data at the time of the kidney biopsy and the renal disease activity of histological injury were analyzed according to the C4d staining status. Glomerular C4d (G-C4d)-positive staining was detected in all 58 cases of LN. Patients with a G-C4d score of 2 displayed more severe proteinuria than those with a G-C4d score of 1 (24-h urinary protein: 3.40 ± 3.55 g vs. 1.36 ± 1.24 g, P < 0.05). Peritubular capillary C4d (PTC-C4d) positivity was found in 34 of 58 LN patients (58.62%). The PTC-C4d-positive patient groups (patients with a PTC-C4d score of 1 or 2) had higher serum creatinine and blood urea nitrogen levels as well as renal pathological activity index (AI) and SLE disease activity index (SLEDAI) scores; however, they had lower serum complement C3 and C4 levels compared to PTC-C4d-negative patients (P < 0.05). In addition, there was positive tubular basement membrane C4d (TBM-C4d) staining in 11 of 58 LN patients (18.96%), and a higher proportion of TBM-C4d-positive patients than TBM-C4d-negative patients (63.63% vs. 21.27%) had hypertension. Our study revealed that G-C4d, PTC-C4d, and TMB-C4d were positively correlated with proteinuria, disease activity and severity, and hypertension, respectively, in pediatric LN patients. These data suggest that renal C4d is a potential biomarker for disease activity and severity in pediatric LN patients, providing insights into the development of novel identification and therapeutic approaches for pediatric-onset SLE with LN.

Urine biomarker score captures response to induction therapy with lupus nephritis

BackgroundThe Renal Activity Index for Lupus (RAIL) consists of urine protein assessment of neutrophil gelatinase–associated lipocalin, kidney injury molecule-1, monocyte chemotactic protein 1, adiponectin, hemopexin, and ceruloplasmin, which non-invasively identifies lupus nephritis (LN). We aimed to delineate RAIL scores with inactive versus active LN and changes over time with response to LN induction therapy.MethodsThere were 128 pediatric patients with systemic lupus erythematosus (SLE) and age-matched healthy controls recruited in a prospective case control study, with kidney biopsy confirmation of LN. Laboratory and clinical information was recorded and urine collected at diagnosis and end of induction and during maintenance therapy. Response to therapy was assessed by repeat kidney biopsy or laboratory parameters. Urine was assayed for RAIL biomarkers and the RAIL score calculated.ResultsPediatric RAIL (pRAIL) scores from 128 children and young adults with SLE (with/without LN: 70/38) including 25 during LN induction therapy, differentiated clinically active LN from inactive LN or without LN, and controls (all p < 0.0017). pRAIL scores significantly decreased with complete LN remission by 1.07 ± 1.7 (p = 0.03). ConclusionsThe RAIL biomarkers differentiate LN patients based on activity of kidney disease, with decreases of ≥ 1 in pRAIL scores indicating complete response to induction therapy. Significantly lower RAIL scores in healthy controls and in SLE patients without known LN raise the possibility of subclinical kidney disease.Graphical abstractA higher resolution version of the Graphical abstract is available as Supplementary information

Renal NLRP3 Inflammasome activation is associated with disease activity in lupus nephritis

The current study was initiated to comprehensively evaluate renal NLRP3 inflammasome pathway activation in lupus nephritis (LN) patients and their clinicopathological significances based on a Chinese LN cohort. We found that the expressions of NLRP3, ASC, caspase-1, IL-1β and IL-18 were all significantly higher in the kidneys of LN patients and were predominantly expressed in glomerular mesangial cells, podocytes, renal tubular epithelial cells and macrophages. The expressions of NLRP3, ASC, caspase-1 and IL-1β were positively correlated to SLEDAI scores and several renal pathological activity indices, while the expression of NLRP3 was negatively associated with chronicity scores. Moreover, the foot process width was positively correlated with glomerular caspase-1 levels, and several podocyte injury markers were decreased significantly in LN patients with higher caspase-1 expression compared with those with lower expression. Our findings indicated that renal NLRP3 inflammasome was activated in LN patients and correlated with disease activity, which needs further explorations.

Type I interferon and neutrophil transcripts in lupus nephritis renal biopsies: clinical and histopathological associations.

To investigate the expression of type I IFN (IFN-I) and neutrophil transcripts in kidney tissue from patients with different classes of LN and their association with distinct clinical and histopathological features. Quantitation of IFN-I, defensin-α3 and formyl peptide receptor-like 1 (FPRL-1) transcripts was performed in kidney biopsy tissue from 24 patients with various classes of LN (6 class III, 14 class IV, 4 class V) and 3 control samples. Patient demographics, glomerular filtration rate (eGFR) and histopathological characteristics, including activity and chronicity indices, were analysed. IFNα2 and IFNβ transcripts were overexpressed in renal tissues from patients with proliferative forms of LN (III/IV) compared with patients with membranous nephritis and control kidneys. Patients with LN and impaired renal function, attested by eGFR, displayed higher relative expression of IFNα2 transcripts in renal tissues compared with those with normal renal function (23.0 ± 16.2 vs 12.0 ± 14.8, P = 0.04). Defensin-α3, but not FPRL-1, transcripts were overexpressed in LN tissues, particularly those with segmental necrotizing lesions, and were correlated with higher renal pathological activity indices (r = 0.61, P = 0.02), urinary protein levels (r = 0.44, P = 0.048) and IFNα2 expression (r = 0.50, P = 0.01). IFN-I transcripts are expressed locally in kidneys from patients with proliferative LN and are associated with impaired renal function. Elevated defensin-α3 transcripts, a neutrophil product associated with neutrophil extracellular traps, may identify a driver of local IFN-I expression. These findings provide insights into the mechanisms of proliferative LN and may inform therapeutic decisions regarding selection of IFN-I pathway inhibitors.

Exploring urine:serum fractional excretion ratios as potential biomarkers for lupus nephritis.

ObjectivesThe goal of this exploratory study is to determine if urine:serum fractional excretion ratios can outperform the corresponding urinary biomarker proteins in identifying active renal disease in systemic lupus erythematosus (SLE).MethodsThirty-six adult SLE patients and twelve healthy controls were examined for serum and urine levels of 8 protein markers, namely ALCAM, calpastatin, hemopexin, peroxiredoxin 6 (PRDX6), platelet factor 4 (PF4), properdin, TFPI and VCAM-1, by ELISA. Fractional excretion of analyzed biomarkers was calculated after normalizing both the urine and serum biomarker levels against creatinine. A further validation cohort of fifty SLE patients was included to validate the initial findings.ResultsThe FE ratios of all 8 proteins interrogated outperformed conventional disease activity markers such as anti-dsDNA, C3 and C4 in identifying renal disease activity. All but VCAM-1FE were superior to the corresponding urine biomarkers levels in differentiating LN activity, exhibiting positive correlation with renal SLEDAI. ALCAMFE, PF4FE and properdinFE ratios exhibited the highest accuracy (AUC>0.9) in distinguishing active LN from inactive SLE. Four of the FE ratios exhibited perfect sensitivity (calpastatin, PRDX6, PF4 and properdin), while ALCAMFE, PF4FE and properdinFE exhibited the highest specificity values for active LN. In addition, several of these novel biomarkers were associated with higher renal pathology activity indices. In the validation cohort ALCAMFE, PF4FE and properdinFE once again exhibited higher accuracy metrics, surpassing corresponding urine and serum biomarkers levels, with ALCAMFE exhibiting 95% accuracy in distinguishing active LN from inactive SLE.ConclusionsWith most of the tested proteins, urine:serum fractional excretion ratios outperformed corresponding urine and serum protein measurements in identifying active renal involvement in SLE. Hence, this novel class of biomarkers in SLE ought to be systemically evaluated in larger independent cohorts for their diagnostic utility in LN assessment.

Urinary CD163 is a marker of active kidney disease in childhood-onset lupus nephritis.

The objective of this study was to evaluate the utility of urine CD163 for detecting disease activity in childhood-onset SLE (cSLE) patients. Sixty consecutive pediatric patients fulfilling four or more ACR criteria for SLE and 20 healthy controls were recruited for testing of urinary CD163 using ELISA. SLE disease activity was assessed using the SLEDAI-2K. Urine CD163 was significantly higher in patients with active LN than inactive SLE patients and healthy controls, with receiver operating characteristics area under the curve values ranging from 0.93 to 0.96. LN was ascertained by kidney biopsy. Levels of CD163 significantly correlated with the SLEDAI, renal SLEDAI, urinary protein excretion and C3 complement levels. Urine CD163 was also associated with high renal pathology activity index and chronicity index, correlating strongly with interstitial inflammation and interstitial fibrosis based on the examination of concurrent kidney biopsies. Urine CD163 emerges as a promising marker for identifying cSLE patients with active kidney disease. Longitudinal studies are warranted to validate the clinical utility of urine CD163 in tracking kidney disease activity in children with lupus.

Urinary HER2, TWEAK and VCAM-1 levels are associated with new-onset proteinuria in paediatric lupus nephritis

ObjectiveLupus nephritis is a key driver of morbidity and mortality in SLE. Detecting active nephritis on a background of pre-existing renal damage is difficult, leading to potential undertreatment and accumulating...

Stability of novel urinary biomarkers used for lupus nephritis.

BackgroundThe Renal Activity Index for Lupus (RAIL) is a composite score of six urinary biomarkers (neutrophil gelatinase–associated lipocalin (NGAL), monocyte chemoattractant protein-1 (MCP-1), kidney injury molecule-1 (KIM-1), ceruloplasmin, adiponectin, and hemopexin) used to monitor lupus nephritis activity in children. We tested stability of RAIL biomarkers prior to meaningful clinical use.MethodsUrine samples were tested by ELISA under shipping conditions, freeze/thaw, ambient and longer-term storage. Statistical analysis was performed via Deming Regression, Bland-Altman and Spearman Correlation Coefficient.ResultsBiomarker concentration were comparable to freshly collected urine following storage at −80 °C for up to 3 months, and at 4 or 25 °C up to 48 h followed by −80 °C. Neither shipping on dry or wet ice exposure nor addition of two freeze-thaw cycles led to loss of signal, with excellent Spearman Correlation coefficients under all conditions.ConclusionsRAIL biomarkers are stable following short-term storage at clinically relevant conditions.

Efficacy and Safety of Biologic Agents for Lupus Nephritis: A Systematic Review and Meta-analysis.

The aim of this study was to examine the effect and safety of biological agents for lupus nephritis (LN). PubMed, EMBASE, and the Cochrane Library databases were searched from their inception up to November 2021. The outcomes were overall response, complete remission, proteinuria, renal activity index, and adverse events (AEs). Only randomized controlled trials (RCTs) were included. Nine RCTs (1645 patients) were included. The RCTs evaluated abatacept (n = 2), belimumab (n = 1), obinutuzumab (n = 1), atacicept (n = 1), IL-2 (n = 1), ocrelizumab (n = 1), and rituximab (n = 2). The use of biological agents was associated with higher likelihoods of achieving an overall response (relative risk [RR], 1.26; 95% confidence interval [CI], 1.15-1.39; p < 0.001; I2 = 14.3%; pQ = 0.301) and a complete response (RR, 1.33; 95% CI, 1.16-1.54; p < 0.001; I2 = 41.8%; pQ = 0.056). The use of biological agents was not associated with improvements in the urinary protein-to-creatinine ratio (weighted mean difference, 3.83; 95% CI, -3.71 to 11.38; p = 0.319; I2 = 99.4%; pQ < 0.001). The use of biological agents in patients with LN was also not associated with an increased risk of any AEs (RR, 1.01; 95% CI, 0.98-1.04; p = 0.519; I2 = 0.0%; pQ = 0.533), serious AEs (RR, 0.95; 95% CI, 0.82-1.09; p = 0.457; I2 = 0.0%; pQ = 0.667), grade >3 AEs (RR, 0.91; 95% CI, 0.67-1.22; p = 0.522; I2 = 0.0%; pQ = 0.977), infections (RR, 1.09; 95% CI, 0.99-1.20; p = 0.084; I2 = 0.0%; pQ = 0.430), and deaths (RR, 0.67; 95% CI, 0.36-1.24; p = 0.200; I2 = 0.0%; pQ = 0.439). The meta-regression analysis showed that follow-up duration and the sample size did not influence the complete response rate, whereas publications in 2012 to 2014 influence the rate compared with 2015 to 2020. Biological agents seem to be effective and safe for managing patients with LN.

Clinical measurement of lupus nephritis activity is inferior to biomarker-based activity assessment using the renal activity index for lupus nephritis in childhood-onset systemic lupus erythematosus.

ObjectivesThe renal activity index for lupus (RAIL) measures lupus nephritis (LN) activity considering urine levels of 6 biomarkers (neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, kidney injury molecule-1, adiponectin, haemopexin, ceruloplasmin). We aimed to compare the accuracy of the RAIL and the renal domain-score of the SLE disease activity index (rSLEDAI) in detecting LN activity.MethodsRandom urine samples of patients with childhood-onset SLE with and without LN were assayed and scores of the RAIL, and RAIL standardised for urine creatinine (RAIL-Cr) were calculated. Clinical LN activity was measured by the rSLEDAI, and histological activity of LN was categorised as inactive/low-moderate/high for National Institute of Health-activity index scores of <2/2–10/>10, respectively.Results115 patients were included in the analysis (47 patients without and 68 with LN). RAIL, RAIL-Cr and rSLEDAI scores at the time (±3 months) of kidney biopsy were available for 32 patients. Median rSLEDAI, RAIL and RAIL-Cr values were 4, –0.04, 0.02 for inactive LN, 12, 0.7 and 0.9 for low-moderate LN activity and 12, 2 and 1.8 for high LN activity, respectively. The area under the receiver operating characteristic curve (AUC) to capture high LN activity was the lowest for the rSLEDAI (AUC=0.62), followed by the RAIL-Cr (AUC=0.73) and RAIL (AUC=0.79). Notably, when testing urine samples collected during routine clinic visits remote (>3 months) from a kidney biopsy, 50% patients with rSLEDAI scores of 0 had RAIL scores reflecting low-moderate LN activity.ConclusionMonitoring of renal inflammation in children and adolescents with SLE can be improved by the measurement of urine biomarkers. The RAIL may constitute important auxiliary tool for the surveillance of LN in a clinical setting and assist with the decision to obtain a kidney biopsy.

Discovery of Novel Circulating Immune Complexes in Lupus Nephritis Using Immunoproteomics.

ObjectiveThe goal is to discover novel circulating immune complexes (ICx) in the serum of lupus nephritis (LN) as potential biomarkers.MethodsProtein A/G magnetic beads or C1q-coated plates were used to capture ICx in the serum of LN, followed by the identification of immunoglobulin-binding proteins using liquid chromatography and tandem mass spectrometry (LC-MS/MS). Bioinformatic approaches and single-cell RNA sequencing (scRNA Seq) databases were used to select potential candidate ICx markers in LN. The selected ICx markers were further validated using ELISA.ResultsA total of 300 immunoglobulin-binding proteins were discovered in the screening, among which 77 proteins were detectable only in LN samples. Bioinformatics-assisted selection allowed us to further identify 10 potential immunoglobulin-binding proteins, which form ICx as potential biomarkers in LN. In a validation cohort of 62 LN patients and 21 healthy controls (HC), we found that prolyl 3-hydroxylase 1 (P3H1), phosphatase and actin regulator 4 (PHACTR4), and regulator of G-protein signaling 12 (RGS12) ICx exhibited discriminative capability in distinguishing LN from HC, with an area under the curve (AUC) values of 0.82, 0.99, and 0.90, respectively. Furthermore, a biomarker panel comprising CD14, CD34, cystatin A, myocyte enhancer factor 2C (MEF2C), RGS12, and ubiquitin C (UBC) ICx could distinguish active LN from inactive LN with an AUC value of 0.85, which is comparable to or better than pathological parameters such as renal activity index (AI) and renal chronicity index (CI).ConclusionImmunoproteomics-based discovery studies have enabled us to identify circulating immune complexes as potential biomarkers of LN.