BK Viremia After Kidney Transplantation: Efficacy of Stepwise Treatments

Background: BK polyomavirus (BKV) increases the risk of graft loss in kidney transplant recipients.However, there is no consensus on treatment methods and outcomes are different.The purpose of this study was to compare the outcomes according to the different treatment methods in kidney transplant recipients who developed BKV viremia.Methods: From January 1, 2016 to June 30, 2020, patients with BKV viremia after kidney transplantation at two participating institutions was retrospectively enrolled.The demographics, clinical information, and laboratory data were collected and analyzed.Results: A total of 199 patients were enrolled and classified into three groups according to the stepwise treatments; group A (reduction of tacrolimus and mycophenolate) (n=123), group B (reduction of tacrolimus and mycophenolate and addition of leflunomide) (n=23), and group C (reduction of tacrolimus and mycophenolate and addition of mTOR inhibitor) (n=53).The average age was 50.7 years, and 125 (62.78%) patients were male.The number of patients suffering BKV-associated nephropathy (BKVAN) was 23 (11.6%), and four (3.3%), two (8.7%), 17 (32.1%)respectively in group A, B, and C (P<0.001).Acute rejection occurred in 69 (34.7%) patients, 31 (44.9%),11 (47.8%), and 27 (50.9%)patients, respectively (P =0.001).The de novo donor-specific antibody (DSA) was found in 21 (10.6%)patients.DSA was found in 13 (10.6%),0 (0.0%), and eight (15.1%)patients, respectively (P=0.529).The mean follow-up period was 45.7 months.The 3-year graft survival was 98.0%.The 3-year patient survival was 97.0% in total.The initial viral load at the time of diagnosis was 2000.0 (IQR, 1000.0-5000.0),4198.0 (IQR, 811.0-10715.0),and 7500.0 (IQR, 2250.0-25750.0)copies/mL, respectively (P<0.001).The rate of decreasing serum viral load was 1000.0 (IQR, 359.3-2646.3),1397.7 (IQR, 1077.0-3571.7),and 6333.3 (IQR, 2666.7-14525.0)copies/mL/month, respectively (P<0.001).Conclusions: We compared three different treatments to manage BKV infection in kidney transplant recipients.Considering costs and effects, treatment modalities for BKV infection should be carefully chosen in kidney transplant recipients.