642 Urine protein array analysis to identify key inflammatory markers in children with IgA Vasculitis nephritis

Abstract

<h3>Aims</h3> Chronic kidney disease is a recognised complication of Immunoglobulin A Vasculitis (IgAV, previously Henoch Schonlein Purpura, HSP). The exact pathophysiology of this disease and the reasons why some patients develop significant renal involvement remain largely unknown (1). Identifying urinary inflammatory markers could aid identification of targets for earlier diagnosis and/or treatment. The aim of this exploratory study was to perform a large protein array analysis to identify key urinary markers of kidney inflammation in children with IgAV nephritis (IgAVN). <h3>Methods</h3> Paediatric patients with IgAV and healthy controls (HC) were recruited as part of the IgA Vasculitis Study (Alder Hey Children’s NHS Foundation Trust, Liverpool, REC 17/NE/0390). Patients with a diagnosis of IgAV were grouped into those with nephritis (IgAVN) and those without (IgAVwoN). Nephritis was defined as a urinary albumin to creatinine ratio (UACR) &gt;30 mg/mmol with a renal biopsy demonstrating IgAVN. Determination of the relative levels of 124 key proteins (encompassing inflammatory cytokines and known markers of kidney inflammation) was performed using commercially available proteome profiler array kits (Human Kidney Biomarker and Human XL Cytokine kits, R&amp;D System Ltd). ImageJ software was used for the pixel density analysis and data was normalised to control points and urinary creatinine. The average fold-change of the relative expression of each protein was calculated and volcano plots were generated to identify significant proteins. Statistical analysis was performed using MetaboAnalyst 5.0 and VolcaNoseR online platforms. <h3>Results</h3> 12 children were included in this study (IgAVN n=4, IgAVwoN n=4, HC n=4). Median age was 7.6 years [4.0-13.44] and male:female ratio was 1:1. For IgAVN, median UACR was 542.2mg/mmol [110.4-2,357.37]. 20 proteins were significantly upregulated (p &lt; 0.05) in nephritis patients compared to those without (<b>figure 1</b>). The largest fold-changes (FC) were reported for B-cell depleting factor (BAFF, FC 9.7), Cripto-1 (FC=7.8), sex-hormone binding globulin (SHBG, FC=7.6) and Angiotensinogen (FC=6.5). Urinary levels of complement components C5/C5a (FC=4.6) and Factor D (FC=2.6) were also significantly elevated in IgAVN compared to IgAVwoN. A total of 69 proteins were significantly upregulated in comparisons made between IgAVN v HC and 9 proteins in IgAVwoN v HC respectively. <h3>Conclusion</h3> This study has identified key urinary proteins providing new insight into the pathophysiology of IgAVN. Further longitudinal studies are needed to quantitatively analyse these biomarkers in a larger cohort. <h3>Reference</h3> Reamy BV, Servey JT, Williams PM. Henoch-Schönlein Purpura (IgA Vasculitis): Rapid Evidence Review. Am Fam Physician (2020)