Proteomic signatures in plasma during early acute renal allograft rejection

Molecular and Cellular Proteomics (2010 Sept 1;9, 1954-1967.)
Cohen Freue GV, Sasaki M, Meredith A, Gunther OP, Bergman A, Takhar M, Mui A, Balshaw RF, Ng RT, Opushneva N, Hollander Z, Li G, Borchers C, Wilson-McManus J, McManus BM, Keown PA, and McMaster WR.

Acute graft rejection is an important clinical problem in renal transplantation and an adverse predictor for long-term graft survival. Plasma biomarkers may offer an important option for post-transplant monitoring, and permit timely and effective therapeutic intervention to minimize graft damage. This case-control discovery study (n=32) used iTRAQ-MALDI-TOF/TOF technology to quantitate plasma protein relative concentrations in precise cohorts of patients with and without biopsy-confirmed acute rejection (BCAR). Plasma samples were depleted of the 14 most abundant plasma proteins to enhance detection sensitivity. A total of 18 plasma proteins that encompassed processes related to inflammation, complement activation, blood coagulation, and wound repair exhibited significantly different relative concentrations between patient cohorts with and without BCAR (p-value below 0.05). Twelve proteins with a fold-change >/= 1.15 were selected for diagnostic purposes: 7 were increased (TTN, LBP, PI16, CFD, MBL2, SERPINA10, B2M) and 5 were decreased (KNG1, AFM, SERPINA5, LCAT and SHBG) in patients with BCAR. The first 3 principal components of these proteins showed clear separation of cohorts with and without BCAR. Performance improved with the inclusion of sequential proteins reaching a primary asymptote after the first 3 (TTN, KNG1, LBP). Longitudinal monitoring over the first 3 months post-transplant based on ratios of these 3 proteins showed clear discrimination between the two patient cohorts at time of rejection. The score then declined to baseline following treatment and resolution of the rejection episode and remained comparable between cases and controls throughout the period of quiescent follow up. Results were validated using ELISA where possible and initial cross-validation estimated a sensitivity of 80% and specificity of 90% for classification of BCAR based on a 4-protein-ELISA classifier. This study provides evidence that protein concentrations in plasma may provide a relevant measure for the occurrence of BCAR, and offers a potential tool for immunologic monitoring.