Cell-Free DNA to Distinguish High Risk Donor Specific Antibodies in Heart Transplantation

Abstract

<h3>Purpose</h3> Donor specific antibodies (DSA) develop in a significant fraction of heart transplant recipients (HTR). Enhanced characterization of high-risk DSA may permit early treatment and prevent downstream antibody-mediated rejection (AMR) and allograft failure. We hypothesize that high risk DSA is associated with allograft injury. Here, we compared allograft injury between high and low risk DSA using donor-derived cell-free DNA (ddcfDNA), a sensitive marker shown to detect AMR ∼3 months earlier than biopsy. <h3>Methods</h3> Using the prospective, multicenter study, Genomic Research Alliance for Transplantation (GRAfT), 81 HTR who underwent surveillance and clinically indicated endomyocardial biopsy, and DSA testing were analyzed. <b>Measurement:</b> Serially collected plasma samples (n=860) were assessed for ddcfDNA by shotgun sequencing. <b>Analysis:</b> DSA were categorized as "high risk" if they were associated with AMR or were otherwise considered "low risk". DSA was further categorized by specificity as class II vs. class I. We compared ddcfDNA between groups with generalized mixed linear models; excluding ddcfDNA before Day 14 post-transplant to reduce transplant surgical contribution. <h3>Results</h3> 47% HTR (n=38) developed DSA at a median 24 days (IQR = 6 - 141 days) post-transplant; and include 28 <i>de novo</i> and 11 preformed DSA. 15.8% (n=6) were categorized as high risk DSA and 84.2% (n=32) were low risk DSA. High risk DSA showed 4X higher ddcfDNA levels compared to low risk DSA (mean [95% CI] 0.30[0.22% - 0.39%] vs. 0.07[0.06%-0.10%], <i>p</i> <0.01, Figure A). As compared to patients without DSA, low risk DSA showed similar ddcfDNA (p=0.52, Figure A). We also found higher ddcfDNA in class II than in class I DSA (Figure B). <h3>Conclusion</h3> High risk DSA show higher allograft injury as measured by ddcfDNA. Similarly, <i>de novo</i> and class II DSA are associated with higher allograft injury than class I or preformed DSA. We provide a novel concept that allows for use of ddcfDNA to stratify high-risk DSA in heart transplantation.