Monitoring of Polyomavirus BK Replication and Impact of Pre-Emptive Immunosuppression Reduction in Renal-Transplant Recipients in China: A 5-Year Single-Center Analysis.

Abstract

Background:A 1-year, single-center trial demonstrated that monitoring and preemptive of immunosuppression reduction were associated with resolution of viremia.Our 5-year prospective subsequent study was conducted to determine the long-term patient/graft survival and outcome of BK viremia and BK virus-associated nephropathy (BKVAN) in renal transplant recipients under the impact of intensive monitoring and reduction of maintenance immunosuppression. Methods:Quantitative BK virus (BKV) DNA surveillance in plasma/urine and cytological test in urine were performed at 1, 3, 6, 9, and 12 months after transplantation in 229 kidney recipients.Patients with BK viremia and BKVAN treated with 30% to 50% reduction in doses of tacrolimus (Tac) or/and mycophenolate mofetil(MMF) without antiviral therapy and were monitored for BKV every 3-6 months. All the patients were followed for 5 years. Results:Overall 5-year patient survival was 95.6% and graft survival was 92.1%. There were no differences in patient/graft survival, renal function, and rejection rate by presence of decoy cells, BK-viruria, viremia, or BKVAN. Multivariate analysis showed that Tac(OR, 2.9; P=0.032)and deceased kidney donation(OR, 2.1; P=0.071) were risk factors for BK viremia. After reduction of immunosuppression, viremia (n=38) resolved in 100%, without increased acute rejection. In the duration of follow-up 2-5 posttransplant years, BK viremia was not observed again in the BK viremic patients (n=30) without BKVAN. BKVAN was diagnosed in 7 cases(3.1%). The treatment of immunosuppression reduction was effective. All the BKVAN patients cleared viremia with a mean time of 5.9 months (range 1-15 months). Three of 7 BKVAN patients cleared viruria. A repeated renal biopsy was performed in two patients and revealed resolving BKVAN. There was no decline in estimated glomerular filtration rate over time from1 month(53.1mL/min) to 5 years(58.5mL/min) after transplantation (P=0.960). Conclusions:Monitoring and preemptive of immunosuppression reduction resulted in the successful resolution of BK viremia, showed effective in BKVAN recipients at the early stage with excellent graft survival and renal function at 5-years.