Possible Mechanisms and Potential Urine Protein Biomarkers through Quantitative Proteomics and Bioinformatics.

Abstract

Introduction: Inability to effectively monitor graft injuries leads to graft dysfunction. A non-invasive tool to monitor such injuries is an unmet need. Method: Through a robust and comprehensive proteomics analysis, rigorous bioinformatics, and ELISA on a set of 480 urine samples with matched biopsies, we identified and validated potential biomarkers for acute rejection (AR), chronic allograft injury (CAI), and BK virus nephropathy (BKVN). Result: A panel of 100 statistically significant proteins as potential biomarkers for different transplant injury is identified. Four proteins, FGB, FGG, SUMO2, and HLA-DRB1 were selected based on their relevance in AR. Urinary FBB in AR was significantly higher vs STA (p=0.04), vs CAI (p=0.05), and vs BKV (p=0.03). The increased urine protein level of FBG in AR (p=0.04), vs CAI (p=0.05), and vs BKV (p=0.02). The urine protein level of HLA-DRB1 was significantly higher in AR vs STA (p=0.001), vs CAI (p=0.003), and vs BKV (p=0.04). Urine SUMO2 level was significantly higher in AR vs STA urine (p=0.005), and vs BKVN urine (p=0.04). An ROC analysis to identify AR from the rest of the phenotypes (CAI, BK, and STA) on the data from FBB, FGG, and HLA-DRB1 yielded an AUC of 0.8.Table: No Caption available.Figure: No Caption available.Conclusion: A panel of 3 urinary proteins, mined by high throughput proteomics, and validated by customized ELISA, allows for non-invasive diagnosis of AR, not confounded by BKVN. This urinary assay requires no local sample processing, is robust and can be used as a sensitive assay for out-patient renal transplant injury surveillance.