A noninvasive assay for monitoring renal allograft status

Transplant rejection is a serious complication, sometimes threatening life of the patient. Although recent development of the new generation of immunosuppressive drugs reduced the incidence of acute rejection in kidney transplantation, the absence of noninvasive biomarkers of the rejection does not allow often the optimization of a prompt antirejection therapy. Serum creatinine is the most widely used marker for allograft function, however, it is not sensitive and specific enough to detect acute rejection. Other biomarkers are even less valuable for this purpose. Histological examination of renal allograft biopsy still remains the golden standard for diagnosing acute renal allograft rejection. Therefore, there is a high demand for reliable biomarkers for noninvasive monitoring of renal allograft status. Examination of urine in renal transplant recipients provides a logical and readily accessible approach for this monitoring. The high potency biomarkers for kidney allograft monitoring are fragments of DNA in recipient urine that originated from renal allograft cells. Because of the difference in the genetic origin these DNA can be distinguished from recipient DNA. Quantitative analysis of donor’s DNA, derived from cells of renal allograft, in recipient’s urine might be a reliable predictive tool for the kidney transplant rejection. We developed an assay to quantitate donor DNA content in recipient urine. Application of the technique—coamplification at lower denaturation temperature-PCR (COLD-PCR) increased the abundance of donor DNA that usually presents in recipient urine in quantities that are out of the detection range. This assay has a potential for routine application in clinical practice after statistical validation and additional modifications.