(15) - Increased Plasma Levels of Graft-Derived Cell-Free DNA Correlate with Rejection in Heart Transplant Recipients

Abstract

Purpose: Circulating graft-derived cell-free DNA (cfDNA) isolated from plasma is a potential biomarker of acute cellular rejection in organ transplant recipients. We sought to investigate if plasma levels of either total or graft derived cfDNA correlate with clinically proven rejection in heart transplant patients. Methods: 118 samples from 76 subjects from the CARGO and CARGO II studies were selected for this cohort study. Levels of total cfDNA were determined by quantitative real-time PCR (qRT-PCR) using assays for HBA, HBB, 18S and PDCD1 genes. Initial investigation of the value of graft-derived cfDNA took advantage of the gender difference in female recipients with a heart from a male donor. Proportions of graft-derived cfDNA relative to total cfDNA were determined in these subjects by qRT-PCR using an assay for the male-specific TSPY-1 gene. Results: Levels of total cfDNA are not different between stable heart transplant recipients and subjects with biopsy-confirmed rejection. Interestingly, heart transplant recipients have higher levels of total cfDNA compared to non-transplant controls. Graft-derived cfDNA proportion is significantly increased in subjects with biopsy-confirmed rejection compared to stable subjects (median difference 10-fold in CARGO and 5-fold in CARGO II subjects older than 15 years and at least 55 days post transplant). Conclusion: Graft-derived cfDNA is a useful biomarker of heart transplant rejection. This non-invasive test may aid in the identification of patients with acute cellular rejection and may be applicable to monitoring other organ transplants, such as lung or kidney. This study was funded by XDx.