Successful treatment of BK viremia using reduction in immunosuppression without antiviral therapy.

Background: Treatment of BK virus (BKV) infection in renal transplant recipients remains controversial. This retrospective analysis evaluated efficacy and safety of reducing immunosuppression without antiviral therapy.

Methods: This single center analysis included 24 patients diagnosed with BK viremia between September 2001 and December 2003. Sixteen patients (66%) presented with BKV nephritis and eight patients (34%) presented with viremia without evidence of nephritis on renal biopsy.

Results: At time of diagnosis, mean plasma BKV DNA (copies/mL) was 460,409 (range 10,205-1,920,691). Mean doses reduction of mycophenolate mofetil and tacrolimus were 44% and 41%, respectively, from time of diagnosis of BKV infection to complete resolution of viremia. A decline in BK viral load was noticed within 15 to 30 days, with successful elimination of viremia over a mean period of 5.8 months (range, 1-9.5). Mean serum creatinine at time of diagnosis of BK viremia was 1.8 mg/dL (range, 1.2-2.8). Mean follow-up period is 30.9 months postdiagnosis. At the most recent visit, serum creatinine was 2.0 mg/dL (range, 1.0-3.6) (P=0.14). With reduction in immunosuppressive therapy, three patients (13%) developed acute cellular rejection and were treated successfully with intravenous bolus steroids. During follow-up, one patient had a relapse of BKV nephritis during pregnancy and lost her graft. After mean follow-up period of 43.5 months posttransplantation, all 24 patients are alive and 23 have a functioning graft. Seventeen patients (71%) have stable or improved graft function.

Conclusion: Our analysis shows that reduction in immunosuppression therapy alone results in clearance of the BK viremia with good long-term outcome.