ELISA Validation of Novel Urine Biomarkers of Lupus Nephritis Discovered Using O-link Proximity Extension Assay

Background: Lupus nephritis (LN) is the inflammation of the kidneys, leading to reduced function. A renal biopsy is currently the preferred diagnosis method, but it cannot be serially repeated for monitoring disease progression and is not optimal for early diagnosis. Urine biomarkers can be used to determine the state of the kidney, diagnose the disease, and monitor disease progression noninvasively. Objective: To determine whether urinary biomarkers discovered using O-link Proximity Extension Assay (O-link) are reliable and reproducible using enzyme-linked immunosorbent assays (ELISA). Methods: Urine from the Hong Kong cohort was interrogated using the O-link technology for the levels of proteins that were significantly different in each step of lupus progression. On the basis of these screens, Human CXCL16, Human IGFBP-2, Human IL-1 RII, Human ICAM-2/CD102, Human FABP4/A-FABP, Human BAFF/BLyS/TNFSF13B, and Human E-selectin were selected for ELISA-based validation in an independent cohort from the University of Texas Southwestern. Results: After the determination of whether the standard proteins worked and the optimal sample dilution factor for each kit, significant differences in the protein levels of the healthy control and active renal samples. Conclusion: It has been demonstrated that O-link is a reliable method of discovering novel biomarkers of LN and the results are reproducible using ELISA screens. Through this study, we hope to find a biomarker that is an accurate and reliable measure for LN patients, with the potential of use in the necessary early detection and diagnosis of renal involvement, regular monitoring of disease activity, and long-term projections for LN.