Dysregulated Circulating Proteins in Cellular and Antibody-Mediated Rejection, on Behalf of the Graft Investigators

PurposeProteomic analysis has identified circulating biomarkers of primary graft dysfunction after heart transplant, but their role in the biological pathways underlying acute cellular rejection (ACR) or antibody-mediated rejection (AMR) is unknown.MethodsAdult heart transplant patients from the Genomic Research Alliance for Transplantation (GRAfT, a prospective, multicenter, post-transplant study from 2015 to 2019) had the Olink (Uppsala, Sweden) proximity extension assay (PEA) performed on blood samples collected at time of endomyocardial biopsy. Patients were categorized as having ACR (grade ≥2R), AMR (grade ≥1) or no rejection. Biomarkers of inflammation and cardiovascular disease were assessed, and the log2 fold change was compared between patients. Student's T test was utilized with p<0.025 considered significant. REACTOME pathway analysis was used to evaluate protein expression.ResultsThe analysis included 113 GRAfT patients (35% Female, 52% Black race, mean age 50.6±11.8 yrs); 84 patients (74%) had no rejection, 17 (15%) had ACR, and 12 (11%) had AMR. With the PEA, 152 unique proteins were analyzed. In both ACR and AMR, CD5, CXCL9, CXCL10, and IL-6 were upregulated (Figure) compared to controls, suggesting common pathways of cytokine-receptor interaction and chemokine (specifically, IL-10) regulation. Protein dysregulation was more pronounced in AMR with 10 inflammatory and 11 cardiovascular proteins having >1 log2 fold change, compared to 1 inflammatory protein in ACR. Patients with AMR and not ACR had upregulation of known cardiovascular biomarkers: myoglobin (MB), ST2, and NT-proBNP, suggesting more myocardial injury, fibrosis and wall stress.ConclusionProteomic analysis reveals unique biomarkers and pathways upregulated in AMR and ACR. Cardiac biomarkers were more pronounced in AMR, suggesting more severe allograft injury. These protein markers may provide additional insights into the pathophysiologic processes that underly acute rejection. Proteomic analysis has identified circulating biomarkers of primary graft dysfunction after heart transplant, but their role in the biological pathways underlying acute cellular rejection (ACR) or antibody-mediated rejection (AMR) is unknown. Adult heart transplant patients from the Genomic Research Alliance for Transplantation (GRAfT, a prospective, multicenter, post-transplant study from 2015 to 2019) had the Olink (Uppsala, Sweden) proximity extension assay (PEA) performed on blood samples collected at time of endomyocardial biopsy. Patients were categorized as having ACR (grade ≥2R), AMR (grade ≥1) or no rejection. Biomarkers of inflammation and cardiovascular disease were assessed, and the log2 fold change was compared between patients. Student's T test was utilized with p<0.025 considered significant. REACTOME pathway analysis was used to evaluate protein expression. The analysis included 113 GRAfT patients (35% Female, 52% Black race, mean age 50.6±11.8 yrs); 84 patients (74%) had no rejection, 17 (15%) had ACR, and 12 (11%) had AMR. With the PEA, 152 unique proteins were analyzed. In both ACR and AMR, CD5, CXCL9, CXCL10, and IL-6 were upregulated (Figure) compared to controls, suggesting common pathways of cytokine-receptor interaction and chemokine (specifically, IL-10) regulation. Protein dysregulation was more pronounced in AMR with 10 inflammatory and 11 cardiovascular proteins having >1 log2 fold change, compared to 1 inflammatory protein in ACR. Patients with AMR and not ACR had upregulation of known cardiovascular biomarkers: myoglobin (MB), ST2, and NT-proBNP, suggesting more myocardial injury, fibrosis and wall stress. Proteomic analysis reveals unique biomarkers and pathways upregulated in AMR and ACR. Cardiac biomarkers were more pronounced in AMR, suggesting more severe allograft injury. These protein markers may provide additional insights into the pathophysiologic processes that underly acute rejection.