Background/Purpose: Systemic lupus erythematosus (SLE) is a heterogeneous systemic autoimmune disease characterized by the production of autoantibodies directed against highly-conserved nuclear antigens. 15-20% of SLE patients develop disease in childhood or adolescence, and pediatric (pSLE) patients often have more severe disease onset and organ system involvement. Autoantigen microarray technology allows the comprehensive analysis of autoantibodies directed against hundreds of antigens with minimal amounts of sera. The purpose of this study was to characterize the spectrum of autoantibody reactivity in a cohort of new-onset pSLE patients and to identify an autoantibody profile that could serve as a biomarker for class III/IV lupus nephritis.

Methods: New-onset pediatric rheumatology patients meeting the revised ACR diagnostic criteria for SLE were eligible for this study. The study was approved by the Stanford University Institutional Review Board and informed consent was obtained prior to participation in the study. Demographic and clinical data at disease onset were collected. Sera from 51 pSLE patients and 20 healthy age- and sex-matched controls were evaluated using an 1128-feature antigen microarray manufactured with approximately 135 antigens. Microarrays were probed with 1:200 dilutions of serum and a Cy5-conjugated goat-anti-human IgG secondary antibody, scanned with a GenePix 4000 scanner, and analyzed using GenePix 6.1 software to determine median fluorescence intensity minus background for each antigen. Significance Analysis of Microarrays (SAM) software was used to determine differences in autoantibody reactivity between pSLE patients and controls, and between pSLE patients with and without proliferative nephritis. Enzyme-linked immunosorbant assays (ELISAs) were performed to confirm autoantibody reactivity identified by microarray.

Results: SAM identified increased reactivity against 50 autoantigens in sera from new-onset pSLE patients compared to controls, with a false discovery rate of zero. In addition to reactivity against classically-described SLE autoantigens, reactivity against several basement membrane and extracellular matrix proteins was identified. Subgroup analysis comparing patients with class III or IV Iupus nephritis to patients without significant nephritis demonstrated increased reactivity against several autoantigens including double-stranded DNA, C1q, histones, collagen and aggrecan in patients with proliferative nephritis. ELISAs confirmed a significant association between proliferative nephritis and reactivity against double-stranded DNA (p=0.0037), histones H2B (p=0.047) & H1 (p=0.02), C1q (p=0.0005), and type IV collagen (p=0.0051).

Conclusion: New-onset pSLE patients demonstrate a broad spectrum of autoantibodies directed against many autoantigens, including those not classically associated with SLE. Subgroup analysis of pSLE patients with and without nephritis revealed a distinct autoantibody profile that could serve as a biomarker for proliferative nephritis. We are currently developing a composite score, based on these autoantibodies and clinical data, to test on an additional cohort of pSLE patients.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/autoantigen-microarray-analysis-of-sera-from-new-onset-pediatric-systemic-lupus-erythematosus-patients-a-distinct-autoantibody-profile-associated-with-class-iiiiv-lupus-nephritis/