Detecting and Quantifying Donor derived cell free DNA in the blood of kidney transplant recipients as a biomarker for graft injury and immunosuppression

Abstract

Acute or chronic graft rejection is the primary threat to transplant recipients. The golden standard for rejection diagnosis is invasive biopsy. Measurement of donor derived cell free DNA (ddcfDNA) in the blood have been described as a non-invasive biomarker for organ transplantations. To develop a diagnostic system to detect graft injury before diagnosis by biopsy, we established capture-based sequencing procedure on extracted cf DNA which targets 1000 selected single nucleotide polymorphism sites. The ddcfDNA percentages were highly elevated on the first days after transplantation, but ddcfDNA percentages were decreased gradually within 7-14 days in stable patients with no sign of rejection. In 80% of cases having rejection episodes and all cases having biopsy proven rejection, ddcfDNA levels showed greater expressive signals on days of rejection episode. Additionally, we found evidences showing that ddcfDNA level sensitively corresponded with immunosuppressant dosages which were administered on recipients. This non-invasive method enables us close follow up the graft injury and prevent graft rejection.