Background: BK viremia can lead to nephritis, which can progress to irreversible kidney transplant failure. Our prospective study provides management and outcome of BK viremia in renal transplant recipients.
Methods: Two hundred forty de novo kidney-only recipients were enrolled from July 2007 to July 2010 and followed for 1 year. Standard immunosuppression with Thymoglobulin/interleukin 2 receptor blocker and mycophenolate mofetil/tacrolimus (Tac)/prednisone was employed. Quantitative BK virus (BKV) DNA surveillance in plasma/urine was performed at 1, 3, 6, 12, and 24 months after transplantation. Patients with significant viremia (defined as ≥10,000 viral copies/mL) underwent renal biopsy and treated with 30% to 50% reduction in doses of both mycophenolate mofetil and Tac without antiviral therapy. The target 12-hr Tac trough levels were lowered to 4 to 6 ng/mL in the significant viremia group, whereas the target levels remained unchanged at 5 to 8 ng/mL for all other groups.
Results: Sixty-five patients (27%) developed BK viremia; 28 (12%) of whom had significant viremia. A total of five (21%) of the 23 (of 28) patients who underwent biopsy presented with subclinical BKV nephritis. The mean plasma BKV DNA declined by 98% (range, 76%-100%) at 1 year after peak viremia. Acute cellular rejection seen in four (14%) of 28 patients, responded to bolus steroids. There was no decline in estimated glomerular filtration rate over time from 1 month after transplantation to 1 year after peak viremia (P=0.57).
Conclusion: Reduction in immunosuppression alone resulted in the successful resolution of viremia with preservation of renal function and prevention of clinical BKV nephritis and graft loss.