Stabilization of renal function after the first year of follow-up in kidney transplant recipients treated for significant BK polyomavirus infection or BK polyomavirus-associated nephropathy.

Background: BK polyomavirus virus (BKPyV) screening and immunosuppression reduction effectively prevent graft loss due to BKPyV-associated nephropathy (BKPVAN) during the first year after transplantation. The aim of our study was to evaluate the impact of this infection during longer follow-up periods.
Methods: We reviewed the outcome of our screening and immunosuppression reduction protocol in 305 patients who received a kidney transplant between March 2008 and January 2013. Quantitative BKPyV DNA surveillance in plasma was performed at 1, 2, 3, 6, 9, and 12 months after transplantation. Patients with significant viremia and/or biopsy-proven BKPVAN were treated with immunosuppression reduction and leflunomide.
Results: During the first post-transplant year, 24 patients (7.9%) developed significant viremia at a median time of 95 days, and 18 patients had BKPVAN; 23 of the 24 (7.5%) were treated according to our protocol (group BKV+); 225 patients (73.8%) did not develop any BK viremia (group BKV-). Allograft function was similar in both groups at 1 month post transplantation (P=.87), but significantly worse at 1 year in the BKV+ group (P=.002). Thereafter, kidney function stabilized in the BKV+ group and no differences in patient and graft survival were seen between the groups after a median follow-up of 4 years.
Conclusions: We confirm the early occurrence of BKPyV replication after transplantation and the short-term decline in renal function. However, early detection of BKPyV replication, prompt diagnosis, and reduction in immunosuppression may offer long-term benefits for graft function.
(© 2017 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.)