Proteogenomic Monitoring and Assessment of Kidney Transplant Recipients

Overview

Chronic Allograft Nephropathy (CAN)/Interstitial fibrosis and Tubular Atrophy (IFTA) is responsible for most kidney transplant failures. CAN/IFTA on a 3 month kidney biopsy strongly predicts graft survival long term. CAN/IFTA remains a vexing problem for clinicians because current monitoring tools, namely the serum creatinine concentration, are not sensitive to early changes in glomerular filtration rate (GFR) or to histologic damage. Despite advances in prevention of acute rejection (AR), it is still a significant and potentially devastating complication of solid organ transplantation. One strategy to reduce the risk of rejection is to perform kidney biopsies to detect subclinical acute rejection (SCAR) and treat to prevent progression to rejection. There is evidence that treating SCAR can prevent further immune mediated injury to the kidney, a precursor to CAN/IFTA. Kidney biopsies provide better information but are limited due to safety concerns, patient preference and cost issues. Better, early and less invasive markers of CAN/IFTA will allow early intervention as well as improved graft and better patient outcomes. This study seeks to validate specific proteogenomic biomarker panels for AR and CAN/IFTA in a prospective blood, urine and kidney tissue monitoring study of kidney transplant recipients who will be scheduled for standard of care biopsies.

This is a single-center sample study. A total number of 1000 subjects will be consented and enrolled at Northwestern University Transplant clinic at the time of kidney biopsy. At our clinic, protocol biopsy may be performed at 3 months, 12 months , 24 months or any other time the doctor feels necessary post transplant in all kidney recipients. Kidney transplant recipients may also go under "for cause" biopsy procedure at any time point before/after or in between these protocol biopsy time points. Such causes of biopsy include increase in serum creatinine level, decrease in urine output, and/or pain at graft site. Full blood tube set, urine sample for proteomics and flow cytometry of urinary sediment, and an extra core kidney biopsy tissue for gene expression profiling will be collected from subjects at the time of any biopsies obtained during the study course. These specimen samples will be sent to Rules-Based Medicine (RBM) for proteomic analysis. Whole genome expression profiling will be done using Affymetrix GeneChips at The Scripps Research Institute. We estimate that we will find at least 500 subjects with diagnostic CAN/IFTA histology (Banff 1-2) between the 3 months and 12 months post transplant protocol biopsies based on a 50% incidence in the literature and our own experience. We also estimate that there will be 10% (10 subjects) incidence of clinical rejection by the end of 12 months identified initially by an acute rise in the serum creatinine and confirmed by a biopsy. Lastly, we estimate a 10% (10 subjects) incidence of subclinical acute rejection with stable renal function detected by the protocol kidney biopsies.