title: Proteomic signatures in plasma during early acute renal allograft rejection.
abstract: 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 isobaric tagging for relative and absolute protein quantification (iTRAQ) 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 <0.05). Twelve proteins with a fold-change >or=1.15 were selected for diagnostic purposes: seven were increased (titin, lipopolysaccharide-binding protein, peptidase inhibitor 16, complement factor D, mannose-binding lectin, protein Z-dependent protease and beta(2)-microglobulin) and five were decreased (kininogen-1, afamin, serine protease inhibitor, phosphatidylcholine-sterol acyltransferase, and sex hormone-binding globulin) in patients with BCAR. The first three 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 three (titin, kininogen-1, and lipopolysaccharide-binding protein). Longitudinal monitoring over the first 3 months post-transplant based on ratios of these three 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 four-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.
authors.affiliation: Prevention of Organ Failure (PROOF) Centre of Excellence, Vancouver, British Columbia, Canada.
authors.forename: Gabriela V Cohen
authors.initials: GV
authors.lastname: Freue
authors.forename: Mayu
authors.initials: M
authors.lastname: Sasaki
authors.forename: Anna
authors.initials: A
authors.lastname: Meredith
authors.forename: Oliver P
authors.initials: OP
authors.lastname: Günther
authors.forename: Axel
authors.initials: A
authors.lastname: Bergman
authors.forename: Mandeep
authors.initials: M
authors.lastname: Takhar
authors.forename: Alice
authors.initials: A
authors.lastname: Mui
authors.forename: Robert F
authors.initials: RF
authors.lastname: Balshaw
authors.forename: Raymond T
authors.initials: RT
authors.lastname: Ng
authors.forename: Nina
authors.initials: N
authors.lastname: Opushneva
authors.forename: Zsuzsanna
authors.initials: Z
authors.lastname: Hollander
authors.forename: Guiyun
authors.initials: G
authors.lastname: Li
authors.forename: Christoph H
authors.initials: CH
authors.lastname: Borchers
authors.forename: Janet
authors.initials: J
authors.lastname: Wilson-McManus
authors.forename: Bruce M
authors.initials: BM
authors.lastname: McManus
authors.forename: Paul A
authors.initials: PA
authors.lastname: Keown
authors.forename: W Robert
authors.initials: WR
authors.lastname: McMaster
mesh_terms: D001798:Blood Proteins / Q000378:metabolism*; D015331:Cohort Studies; D004797:Enzyme-Linked Immunosorbent Assay; D006084:Graft Rejection / Q000097:blood*; D006801:Humans; D016030:Kidney Transplantation; D008137:Longitudinal Studies; D008991:Monitoring, Physiologic; D011446:Prospective Studies; D040901:Proteomics; D015203:Reproducibility of Results; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D001798:Blood Proteins