Polymerase chain reaction (PCR) demonstration of BK viral replication in plasma and urine supports the diagnosis of BK virus nephropathy (BKVN), an important cause of allograft dysfunction after kidney transplantation. Nonetheless, renal biopsy is mandatory for the definitive diagnosis of BKVN, which is invasive and requires unnecessary admission. Recently, bkv-miR-B1-5p, one of the miRNAs, encoded by BK virus (BKV), was reported to be elevated in the blood among the patients with BK virus nephropathy (BKVN). We evaluated the utility of viral miRNA in urinary exosomes for the diagnosis of BKVN in renal allograft recipients.

A total of 80 kidney transplant recipients including 13 patients with confirmed BKVN by renal biopsy were enrolled in this study. Exosomal fraction was isolated from urine samples and the bkv-miR-B1-3p, bkv-miR-B1-5p and miR-16 were quantified using real-time PCR (RT-PCR). BKV DNA loads in plasma and urine were also compared with exosomal miRNA levels.

Urine exosomal bkv-miR-B1-3p and bkv-miR-B1-5p levels were significantly higher in BKVN group than all the other groups, and this finding was consistent after normalization with miR-16. Exosomal viral miRNAs showed positive correlation with both plasma and urine titers of viral DNA. The receiver operator characteristics (ROC) curve analysis for bkv-miR-B1-5p and bkv-miR-B1-5p/miR-16 showed excellent values of area under curve (AUC) for the diagnosis of BKVN.

Our data suggest that urinary exosomal bkv-miR-B1-5p and bkv-miR-B1-5p/miR-16 can be surrogate markers for the diagnosis of BKVN. Further prospective study should be performed for the clinical application of viral miRNAs in transplantation.

CITATION INFORMATION: Seo J.-W, Lee Y, Moon H, Kim Y, Jeong K.-H, Moon J.-Y, Kim C.-D, Park J, Chung B, Kim Y.-H, Lee S.-H. Clinical Utility of Viral miRNA in Urinary Exosomes to Diagnose BK Virus Nephropathy After Kidney Transplantation. Am J Transplant. 2017;17 (suppl 3).

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