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

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

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.

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.

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.