Urine Exosomal bkv-miR-B1-5p and BK Virus Nephropathy in Kidney Transplant Recipients

Background: Urine exosomal bkv-miR-B1-5p is associated with BK virus (BKV) nephropathy (BKVN); however, its posttransplantation changes and predictability for BKVN have not been determined in kidney transplant recipients (KTRs). Methods: Urine exosomal bkv-miR-B1-5p and urine and plasma BKV DNA were measured at 2 weeks and 3, 6, and 12 months posttransplant in 83 KTRs stratified into biopsy-proven or presumptive BKVN, BKV viruria, and no evidence of BKV reactivation. Joint model, multivariable Cox model and receiver operating characteristic curve (ROC) were used to investigate the association of each assay with the following events: a composite of biopsy-proven or presumptive BKVN, and biopsy-proven BKVN. Results: Urine exosomal bkv-miR-B1-5p and urine and plasma BKV DNA showed similar posttransplant time-course changes. Joint models incorporating serial values demonstrated significant associations of all assays with the events, and Cox analyses using single time point values at 2 weeks posttransplant showed that only urine exosomal bkv-miR-B1-5p was significantly associated with the events, although it did not outperform urine BKV DNA in ROC analyses. Conclusions: Urine exosomal bkv-miR-B1-5p was associated with BKVN as were urine and plasma BKV DNA loads on serial follow-up, and might have potential as a predictive marker for BKVN during the early posttransplant period. Clinical Trials Registration: Clinical Research Information Service (https://cris.nih.go.kr/cris/), KCT0001010.