Marisa S. Klein-Gitelman

Identification of IRAK1 as a risk gene with critical role in the pathogenesis of systemic lupus erythematosus

A combined forward and reverse genetic approach was undertaken to test the candidacy of IRAK1 (interleukin-1 receptor associated kinase-1) as an X chromosome-encoded risk factor for systemic lupus erythematosus (SLE). In studying ≈5,000 subjects and healthy controls, 5 SNPs spanning the IRAK1 gene showed disease association (P values reaching 10−10, odds ratio >1.5) in both adult- and childhood-onset SLE, in 4 different ethnic groups, with a 4 SNP haplotype (GGGG) being strongly associated with the disease. The functional role of IRAK1 was next examined by using congenic mouse models bearing the disease loci: Sle1 or Sle3. IRAK1 deficiency abrogated all lupus-associated phenotypes, including IgM and IgG autoantibodies, lymphocytic activation, and renal disease in both models. In addition, the absence of IRAK1 reversed the dendritic cell “hyperactivity” associated with Sle3. Collectively, the forward genetic studies in human SLE and the mechanistic studies in mouse models establish IRAK1 as a disease gene in lupus, capable of modulating at least 2 key checkpoints in disease development. This demonstration of an X chromosome gene as a disease susceptibility factor in human SLE raises the possibility that the gender difference in SLE may in part be attributed to sex chromosome genes.

Systemic lupus erythematosus in childhood

Systemic lupus erythematosus is a disease of immune dysregulation that strikes approximately 1 in 2000 individuals. The usual patient is a young woman of child-bearing age; however, this illness affects patients of all ages, ethnic backgrounds, and both sexes. Twenty percent of all cases of lupus are diagnosed during the first two decades of life. Perhaps the most essential point in treating a child with lupus is to be aware and concerned about how to deliver treatment to a patient in the middle of their physical, intellectual, and emotional development.

Neutrophil gelatinase–associated lipocalin is a predictor of the course of global and renal childhood‐onset systemic lupus erythematosus disease activity

OBJECTIVE To determine whether neutrophil gelatinase-associated lipocalin (NGAL) can predict worsening of global and renal disease activity in childhood-onset systemic lupus erythematosus (SLE). METHODS One hundred eleven patients with childhood-onset SLE were enrolled in a longitudinal, prospective study with quarterly study visits and had at least 3 study visits. At each visit, global disease activity was measured using 3 external standards: the numerically converted British Isles Lupus Assessment Group (BILAG) index, the SLE Disease Activity Index 2000 update score, and the physicians assessment of global disease activity. Renal and extrarenal disease activity were measured by the respective domain scores. The disease course over time was categorized at the most recent visit (persistently active, persistently inactive, improved, or worsening). Plasma and urinary NGAL levels were measured by enzyme-linked immunosorbent assay, and urinary NGAL levels were standardized to the urinary creatinine concentration. The longitudinal changes in NGAL levels were compared with the changes in SLE disease activity using mixed-effect models. RESULTS Significant increases in standardized urinary NGAL levels of up to 104% were detected up to 3 months before worsening of lupus nephritis (as measured by all 3 external standards). Plasma NGAL levels increased significantly by as much as 26% up to 3 months before worsening of global SLE disease activity as measured by all 3 external standards. Plasma NGAL levels increased significantly by 26% as early as 3 months prior to worsening of lupus nephritis as measured by the BILAG renal score. CONCLUSION Serial measurement of urinary and plasma NGAL levels may be valuable in predicting impending worsening of global and renal childhood-onset SLE disease activity.

Neutrophil gelatinase-associated lipocalin as a biomarker of disease activity in pediatric lupus nephritis

We hypothesized that neutrophil gelatinase-associated lipocalin (NGAL) is an early predictive biomarker of disease activity in lupus nephritis. NGAL in serial plasma (PNGAL) and urine (UNGAL) samples was measured by enzyme-linked immunosorbent assay (ELISA) in 85 participants with pediatric systemic lupus erythematosus (pSLE), healthy children (n = 50), and children with juvenile idiopathic arthritis (JIA) (n = 30). Disease activity was measured by the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI). Plasma and urinary NGAL were significantly increased in subjects with pSLE compared with those with JIA or with healthy controls (all p < 0.03), and unrelated to subjects’ age, weight, or height. Plasma and urinary NGAL were stable in pSLE subjects with unchanged disease activity. The pSLE subjects with worsening global or renal disease activity had a mean ± standard error (SE) increase of UNGAL (in ng/ml) of 11.5 ± 6.4 or 36.6 ± 12.1 (p < 0.01), corresponding to a 156% or 380% increase, respectively. PNGAL increased with worsening disease but to a much lesser degree than UNGAL [global disease activity (mean ± SE): 7.3 ± 6.2 or 21%; renal disease activity: 20.2 ± 6.0 or 51%; both p = not significant]. In conclusion, NGAL in urine but not in plasma represents a novel biomarker for renal disease activity in pSLE.

Consensus treatment plans for induction therapy of newly diagnosed proliferative lupus nephritis in juvenile systemic lupus erythematosus

To formulate consensus treatment plans (CTPs) for induction therapy of newly diagnosed proliferative lupus nephritis (LN) in juvenile systemic lupus erythematosus (SLE).

Lupus-associated causal mutation in neutrophil cytosolic factor 2 (NCF2) brings unique insights to the structure and function of NADPH oxidase

Systemic lupus erythematosus (SLE), the prototypic systemic autoimmune disease, is a debilitating multisystem autoimmune disorder characterized by chronic inflammation and extensive immune dysregulation in multiple organ systems, resulting in significant morbidity and mortality. Here, we present a multidisciplinary approach resulting in the identification of neutrophil cytosolic factor 2 (NCF2) as an important risk factor for SLE and the detailed characterization of its causal variant. We show that NCF2 is strongly associated with increased SLE risk in two independent populations: childhood-onset SLE and adult-onset SLE. The association between NCF2 and SLE can be attributed to a single nonsynonymous coding mutation in exon 12, the effect of which is the substitution of histidine-389 with glutamine (H389Q) in the PB1 domain of the NCF2 protein, with glutamine being the risk allele. Computational modeling suggests that the NCF2 H389Q mutation reduces the binding efficiency of NCF2 with the guanine nucleotide exchange factor Vav1. The model predicts that NCF2/H389 residue interacts with Vav1 residues E509, N510, E556, and G559 in the ZF domain of Vav1. Furthermore, replacing H389 with Q results in 1.5 kcal/mol weaker binding. To examine the effect of the NCF2 H389Q mutation on NADPH oxidase function, site-specific mutations at the 389 position in NCF2 were tested. Results show that an H389Q mutation causes a twofold decrease in reactive oxygen species production induced by the activation of the Vav-dependent Fcγ receptor-elicited NADPH oxidase activity. Our study completes the chain of evidence from genetic association to specific molecular function.

Initial validation of a novel protein biomarker panel for active pediatric lupus nephritis.

Lupus nephritis (LN) is among the main determinants of poor prognosis in systemic lupus erythematosus (SLE). The objective of this study was to 1) isolate and identify proteins contained in the LN urinary protein signature (PS) of children with SLE; 2) assess the usefulness of the PS proteins for detecting activity of LN over time. Using surface-enhanced or matrix-assisted laser desorption/ionization time of flight mass spectrometry, the proteins contained in the LN urinary PS were identified. They were transferrin (Tf), ceruloplasmin (Cp), α1-acid-glycoprotein (AGP), lipocalin-type prostaglandin-D synthetase (L-PGDS), albumin, and albumin-related fragments. Serial plasma and urine samples were analyzed using immunonephelometry or ELISA in 98 children with SLE (78% African American) and 30 controls with juvenile idiopathic arthritis. All urinary PS proteins were significantly higher with active vs. inactive LN or in patients without LN (all p < 0.005), and their combined area under the receiver operating characteristic curve was 0.85. As early as 3 mo before a clinical diagnosis of worsening LN, significant increases of urinary Tf, AGP (both p < 0.0001), and L-PGDS (p < 0.01) occurred, indicating that these PS proteins are biomarkers of LN activity and may help anticipate the future course of LN.

High‐density genotyping of STAT4 reveals multiple haplotypic associations with systemic lupus erythematosus in different racial groups

OBJECTIVE Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disorder, with complex etiology and a strong genetic component. Recently, gene products involved in the interferon pathway have been under intense investigation in terms of the pathogenesis of SLE. STAT-1 and STAT-4 are transcription factors that play key roles in the interferon and Th1 signaling pathways, making them attractive candidates for involvement in SLE susceptibility. METHODS Fifty-six single-nucleotide polymorphisms (SNPs) across STAT1 and STAT4 on chromosome 2 were genotyped using the Illumina platform, as part of an extensive association study in a large collection of 9,923 lupus patients and control subjects from different racial groups. DNA samples were obtained from the peripheral blood of patients with SLE and control subjects. Principal components analyses and population-based case-control association analyses were performed, and the P values, false discovery rate q values, and odds ratios with 95% confidence intervals were calculated. RESULTS We observed strong genetic associations with SLE and multiple SNPs located within STAT4 in different ethnic groups (Fishers combined P = 7.02 x 10(-25)). In addition to strongly confirming the previously reported association in the third intronic region of this gene, we identified additional haplotypic association across STAT4 and, in particular, a common risk haplotype that is found in multiple racial groups. In contrast, only a relatively weak suggestive association was observed with STAT1, probably due to its proximity to STAT4. CONCLUSION Our findings indicate that STAT4 is likely to be a crucial component in SLE pathogenesis in multiple racial groups. Knowledge of the functional effects of this association, when they are revealed, might improve our understanding of the disease and provide new therapeutic targets.

Validation of the Pediatric Automated Neuropsychological Assessment Metrics in childhood-onset systemic lupus erythematosus.

To evaluate the reproducibility and validity of the Pediatric Automated Neuropsychological Assessment Metrics (Ped‐ANAM) when used in childhood‐onset systemic lupus erythematosus (cSLE).

Health-related Quality of Life and Its Relationship to Patient Disease Course in Childhood-onset Systemic Lupus Erythematosus

Objective. To (1) estimate the health-related quality of life (HRQOL) of children with childhood-onset systemic lupus erythematosus (cSLE) and compare it to that of normative cohorts; (2) assess the relationship of HRQOL with cSLE disease activity and damage; and (3) determine the effects of changes of disease activity on HRQOL. Methods. Patients with cSLE (n = 98) followed every 3 months completed HRQOL measures, the Pediatric Quality of Life Inventory Generic Core scale (PedsQL-GC), the Rheumatology Module (PedsQL-RM), and the Child Health Questionnaire (CHQ). The British Isles Lupus Activity Group Index (BILAG) was used to measure organ-system-specific disease activity. Physicians rated the course of cSLE between visits. Results. At baseline, mean (standard deviation, SD) score [parent report] of the PedsQL-GC and the PedsQL-RM was 75 (17) and 79 (14), respectively; the mean (SD) of the CHQ physical summary score (CHQ-PHS) was 49 (7) and that of the CHQ psychological summary score was 42 (12). Higher BILAG scores, especially in the general, musculoskeletal, neurological, and vascular, but not the mucocutaneous, renal, cardiovascular, or hematological BILAG domains, were associated with a significantly lower HRQOL. Patients with damage had lower HRQOL than those without damage. All HRQOL measures included were at most modestly responsive to clinically important changes with cSLE. Conclusion. HRQOL with cSLE is significantly lower than that reported in healthy populations. Organ-specific involvement with cSLE has a differential effect on HRQOL. Higher disease activity and damage are associated with significantly lower HRQOL as measured by the PedsQL-RM and the CHQ-PHS, and worsening of cSLE leads to a further decline.