Monitoring of Organ Transplants (MOAT) Study

Abstract

Solid organ transplantation (SOT) is the only treatment option for patients with end stage organ failure. Yet transplantation is not a lifelong cure, in paediatric patients over half of recipients will not live beyond 25 years post transplantation. Short-term outcomes have improved with advances in surgery and immunosuppression, but medium- and long-term outcomes have not seen the same improvements due to allograft rejection. Tissue biopsies are the gold standard for monitoring and detecting allograft rejection, which can allow for early intervention, but irreversible allograft damage may have already occurred by the time a biopsy is performed. The use of an alternative biomarker which can be performed more regularly to detect early sub-clinical rejection is of great interest. Research into the use of cell free DNA (cfDNA) as a non-invasive biomarker is expanding rapidly as a new test to detect allograft damage. However, quantifying the low fraction of donor-derived cfDNA (ddcfDNA) is challenging, requiring a highly sensitive technique. ddcfDNA detection through unique donor single nucleotide polymorphisms (SNPs) is a recent new approach, however there are limited data in paediatric SOT recipients. An assay using a combination of 61 SNPs was developed to accurately quantify ddcfDNA using a custom R script to model for both the patient and donor genotypes requiring only a single sample from the allograft recipient (a donor sample is not required). Performance of the assay was validated using genomic DNA (gDNA) , cfDNA and donor samples where available. 159 paediatric SOT recipients (kidney, heart and lung) were tested without the need for donor’s genotyping. Serial sampling was obtained from 82 patients. The R ‘’genotype-free’’ method gave results comparable to when using the known donor genotype, applicable to both related and unrelated pairs and can reliably measure ddcfDNA (limit of blank, below 0.12%; limit of detection, above 0.25%; limit of quantification 0.5% resulting in 84% accuracy, 99.65% success rate). High levels of ddcfDNA were detected immediately post-transplantation (post-transplant) and also in acute rejection. This method can provide results in 48 hours at a low cost. Additional prospective studies are required to demonstrate its clinical validity in a larger cohort of paediatric SOT recipients.

Date of Award	1 Aug 2021
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Alexander Heazell (Supervisor)