Confirmatory biopsy after treatment for acute rejection is uncommon. Serum creatinine (SCr) and random urine albumin to urine creatinine (Ur alb:Ur Cr) ratios are used to monitor resolution of rejection. Donor-derived cell–free DNA (dd-cfDNA) (AlloSure; CareDX, Brisbane, CA) levels >1% detect active renal allograft injury.1 Given the short half-life of dd-cfDNA (approximately 30 minutes), we believed that if patients with acute rejection were treated appropriately, then dd-cfDNA levels could verify resolution of rejection as early as the final days of treatment.2 We treated 3 patients for biopsy-proven renal allograft rejection, and dd-cfDNA declined <1% upon completion of therapy.
The first patient received a deceased-donor kidney transplant (DDKT) with alemtuzumab induction followed by steroid-sparing immunosuppression with tacrolimus (TAC) and mycophenolate mofetil (MMF). Nine months after transplant, she experienced a gradual rise in SCr and Ur Alb:Ur Cr, prompting us to obtain a dd-cfDNA level of 1.3%. Luminex single antigen bead immunoassay was negative for donor-specific antibody (DSA), and a radiographically directed, percutaneous biopsy revealed Banff IA plasma cell–rich, mild acute T-cell–mediated rejection (TCMR).3 On the final day of pulse-dose intravenous methylprednisolone treatment, repeat dd-cfDNA was 0.42%. SCr and Ur Alb:Ur Cr returned to a new baseline, and weekly dd-cfDNA samples remained <1%, confirming resolution of plasma cell–rich, mild acute TCMR.
Our second patient received a DDKT with rabbit antithymocyte globulin induction plus maintenance TAC + MMF + prednisone until he presented 11 months posttransplant with an elevated SCr and de novo BK viremia (for which we stopped MMF and administered intravenous immunoglobulin-proline). He developed de novo class I DSA, an increased SCr, an increased Ur Alb:Ur Cr, and a dd-cfDNA level of 3.5%, prompting an allograft biopsy that revealed early, borderline TCMR.3 Two days after completion of pulse-dose intravenous methylprednisolone treatment, repeat dd-cfDNA was 0.49%. SCr returned to baseline, BK viremia decreased, class I DSA cleared completely, and serial dd-cfDNA tests remained <1%, confirming resolution of early, borderline TCMR.
A third patient received a DDKT with rabbit antithymocyte globulin induction, followed by maintenance of TAC + MMF + prednisone. Twenty-eight months posttransplant, the patient presented with an elevated SCr, elevated Ur Alb:Ur Cr, de novo class I and II DSA, and 2.6% dd-cfDNA, prompting a biopsy that revealed C4d-positive antibody-mediated rejection.3 The patient received pulse-dose steroids and 5 sessions of alternating day therapeutic plasma exchange with intravenous immunoglobulin-proline. We reasoned that dd-cfDNA would likely be removed with therapeutic plasma exchange and decided to wait 1 day after his final session to repeat dd-cfDNA that was 0.67%. SCr and Ur Alb:Ur Cr returned to baseline, class I and II DSAs decreased, and repeat dd-cfDNA levels remained <1%, suggesting resolution of C4d-positive antibody-mediated rejection.
We believe this is the first report of monitoring dd-cfDNA trends before and upon completion of acute rejection treatment; large-scale studies are needed to formally explore our findings and investigate the accuracy of dd-cfDNA as a potential biomarker for real-time monitoring of response to therapy.
1. Bloom RD, Bromberg JS, Poggio ED, et al. Cell-free DNA and active rejection in kidney allografts. J Am Soc Nephrol. 2017;28:2221–2232.
2. Yu SC, Lee SW, Jiang P, et al. High-resolution profiling of fetal DNA clearance from maternal plasma by massively parallel sequencing. Clin Chem. 2013;59:1228–1237.
3. Haas M, Loupy A, Lefaucheur C, et al. The Banff 2017 Kidney Meeting Report: Revised diagnostic criteria for chronic active T cell-mediated rejection, antibody-mediated rejection, and prospects for integrative endpoints for next-generation clinical trials. Am J Transplant. 2018;18:293–307.