Background: Immunosuppression reduction for BK viremia is associated with de novo humoral responses, which are a risk factor for rejection and graft loss. In this pilot project, we tested a protocol of immunosuppression resumption to standard dose after viral clearance for optimal protection against rejection in patients undergoing treatment for BK viremia.
Methods: Thirty-six consecutive kidney transplant recipients who developed BK viremia from 7/1/2014 until 11/18/2016 underwent immunosuppression reduction. After four weeks of absent viremia, mycophenolate mofetil (MMF) was increased by 500mg/day every two weeks up to standard dosage, followed by increase of tacrolimus trough levels to 5-7ng/mL. If viremia recurred during the increase, immunosuppression was reduced in this same stepwise fashion, with stepwise increase again after two months of negative viremia.
Results: Mean tacrolimus trough level (ng/mL) was 8.3+2.7 at viremia onset, 5.3+3.6 at resolution, and 5.6+2.0 at study end date.  Mean daily dose (mg) of MMF was 1574+355 at onset, 910+230 at resolution, and 1377+451 at study end date. Only one patient developed low level viremia recurrence (peak 2875 copies/mL) during the period of immunosuppression resumption that ultimately resolved.
Conclusions: The results of our pilot project indicate that following BK viremia resolution, resumption of standard immunosuppression can be achieved safely without BK viremia recurrence. Larger trials with long-term follow up are required to determine whether such an approach improves long- term graft survival.