Proteomics in Acute Heart Transplant Rejection, on Behalf of the GRAfT Investigators.

Background: Proteomic phenotyping can provide insights into rejection pathophysiology, novel biomarkers, and therapeutic targets.

Methods: Within the prospective, multicenter Genomic Research Alliance for Transplantation study, 181 proteins were evaluated from blood drawn at the time of endomyocardial biopsy; protein fold change, logistic regression, and pathway analyses were conducted, with protein discovery adjusted for a 5% false discovery rate.

Results: Among 104 adult heart transplant patients (31% female sex, 53% Black race, median age 52 y), 74 had no rejection, 18 developed acute cellular rejection (ACR), and 12 developed antibody-mediated rejection (AMR). Differential expression was found in 2 proteins during ACR (inflammatory proteins CXCL10 and CD5) and 73 proteins during AMR. The most abundant AMR proteins were the heart failure biomarkers N-terminal pro-B-type natriuretic peptide and suppression of tumorigenicity 2. In univariate logistic regression, odds of identifying ACR on endomyocardial biopsy increased with doubling of CXCL10 (odds ratio [OR] 2.2 [95% confidence interval (CI), 1.3-3.6]) and CD5 (OR 4.7 [95% CI, 1.7-12.9]) concentrations, and odds of AMR increased with doubling of N-terminal pro-B-type natriuretic peptide (OR 13.0 [95% CI, 2.7-62.7) and suppression of tumorigenicity 2 (OR 4.8 [95% CI, 2.1-10.7]) concentrations. After multivariable analysis with clinical covariates, these proteins showed similar odds of ACR or AMR on biopsy. Pathway analysis identified T cell-receptor signaling and cell differentiation as key pathways in ACR and cardiovascular disease and cell turnover in AMR.

Conclusions: Proteomic analysis reveals unique biomarkers and biological pathway expression in ACR and AMR. Cardiac injury-associated biomarkers were more pronounced in AMR, whereas inflammatory biomarkers were more pronounced in ACR. Proteomic analysis may provide insights into rejection pathophysiology, detection, and therapy.