title: Urine protein profiling identified alpha-1-microglobulin and haptoglobin as biomarkers for early diagnosis of acute allograft rejection following kidney transplantation.
abstract: OBJECTIVE
  Early diagnosis of acute rejection and effective immunosuppressive therapy lead to improvement in graft survival following kidney transplantation. In this study, we aimed to establish a urinary protein profile suitable to distinguish between patients with rejection and stable graft function and to predict acute rejection based on postoperatively collected urine samples. A further objective was to identify candidate proteins for the use as biomarkers in clinical practice.
  
  
  METHODS
  Urine samples of 116 kidney recipients were included. Rejection was proven by biopsy (n = 58), and stable transplant function was monitored for at least 2 years (n = 58). Postoperative urine samples were collected between 3rd and 10th day following transplantation. Urinary protein profiles were obtained by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry. Protein identification and validation were performed using multiplex fluorescence 2DE, peptide mass fingerprinting and enzyme-linked immunosorbent assay.
  
  
  RESULTS
  A protein profile including four mass peaks differentiated acute rejection from stable transplants at the time point of rejection and at the postoperative state with 73 % sensitivity and 88 % specificity. Alpha-1-microglobulin (A1MG) and Haptoglobin (Hp) were identified as putative rejection biomarkers. Protein levels were significantly higher in postoperative urine from patients with rejection (A1MG 29.13 vs. 22.06 μg/ml, p = 0.001; Hp 628.34 vs. 248.57 ng/ml, p = 0.003). The combination of both proteins enabled the diagnosis of early rejection with 85 % sensitivity and 80 % specificity.
  
  
  CONCLUSIONS
  Protein profiling using mass spectrometry is suitable for noninvasive detection of rejection-specific changes following kidney transplantation. A specific protein profile enables the prediction of early acute allograft rejection in the immediate postoperative period. A1MG and Hp appear to be reliable rejection biomarkers.
authors.affiliation: Department of Urology, Jena University Hospital, Jena, Germany.
authors.forename: Beatrice
authors.initials: B
authors.lastname: Stubendorff
authors.forename: Stephanie
authors.initials: S
authors.lastname: Finke
authors.forename: Martina
authors.initials: M
authors.lastname: Walter
authors.forename: Olaf
authors.initials: O
authors.lastname: Kniemeyer
authors.forename: Ferdinand
authors.initials: F
authors.lastname: von Eggeling
authors.forename: Torsten
authors.initials: T
authors.lastname: Gruschwitz
authors.forename: Thomas
authors.initials: T
authors.lastname: Steiner
authors.forename: Undine
authors.initials: U
authors.lastname: Ott
authors.forename: Gunter
authors.initials: G
authors.lastname: Wolf
authors.forename: Heiko
authors.initials: H
authors.lastname: Wunderlich
authors.forename: Kerstin
authors.initials: K
authors.lastname: Junker
mesh_terms: D000328:Adult; D000510:Alpha-Globulins / Q000652:urine*; D015415:Biomarkers / Q000652:urine; D015331:Cohort Studies; D042241:Early Diagnosis; D005260:Female; D006084:Graft Rejection / Q000175:diagnosis* / Q000652:urine*; D006242:Haptoglobins / Q000652:urine*; D006801:Humans; D016030:Kidney Transplantation; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012372:ROC Curve; D051437:Renal Insufficiency / Q000175:diagnosis / Q000601:surgery / Q000652:urine*
chemical_list: D000510:Alpha-Globulins; D015415:Biomarkers; D006242:Haptoglobins; C016001:alpha-1-microglobulin