Prevalence and Impact of BK Polyomavirus in the Ureters of Kidney Donors: Research Letter.

Background: More than 75% of the population is seropositive for BK polyomavirus (BKV), which remains quiescent in the urothelium in immunocompetent hosts. However, it can reactivate in kidney transplant recipients (KTRs), and up to 30% of them will develop BKV viremia in the 2 years following transplant, with a risk of developing BKV-associated nephropathy (BKVAN). Viral reactivation is associated with the level of immunosuppression, but there is currently no way to predict which patients are at high risk for reactivation.

Objective: As BKV originates from kidney donors, our primary objective was to determine the prevalence of detectable BKV in donor ureters. Our secondary objective was to see if there is a correlation between the presence of BKV in donor urothelium and the development of BKV viremia and BKVAN in KTR.

Design: Prospective cohort study.

Setting: Single-center academic kidney transplant program.

Patients: Prospective sequential KTRs that received a kidney transplant between March 2016 and March 2017.

Measurements: The presence of BKV in donor ureters was determined by TaqMan-based quantitative polymerase chain reaction (PCR; qPCR).

Methods: We performed a prospective study which was done on 35 out of the 100 donors initially foreseen to take part in the study. During surgery, the distal part of donor ureter was kept and analyzed by qPCR (to establish the presence of BKV in the urothelium). The primary outcome was the development of BKV viremia in KTR over a period of 2 years after transplant. Secondary outcome was the development of BKVAN.

Results: Out of 35 ureters analyzed, only one had a positive qPCR for BKV (2.86%, 95% confidence interval [CI]: [0.07-14.92]). Considering the primary objective would not be met, the study was interrupted after 35 specimens. After surgery, 9 recipients had a slow graft function and 4 had delayed graft function, one of which never recovered graft function. Over the 2-year follow-up, 13 patients developed BKV viremia, while 5 patients developed BKVAN. The patient who received a graft from a positive qPCR donor eventually developed BKV viremia and nephropathy.

Limitations: The specimen analyzed was a distal rather than a proximal portion of the ureter. However, BKV replication is known to concentrate in the corticomedullary junction.

Conclusion: BK polyomavirus prevalence in the distal part of donor ureters is lower than previously reported. It cannot be used as a predictor for the development of BKV reactivation and/or nephropathy.