[Analysis of BK viruria on the long term graft survival in renal transplant recipients].

OBJECTIVE: To observe the clearance of BK viruria and long-term graft survival in renal transplant recipients with BK virus (BKV) infection under the protocol of our center.

METHODS: Urine was taken from 229 renal transplant recipients,who were transplanted between March 2006 to October 2008, for BKV cytological testing and real-time PCR for BKV DNA at 1, 3, 6, 9, and 12 months after transplantation. Graft biopsies were analyzed for SV40-T by immunohistochemical method. Recipients were treated according to the BKV infection protocol of our center and were monitored for BKV and graft function. All the patients were followed for at least 5 years.

RESULTS: By 1 year post-transplant, urinary decoy cells, BK viruria, and BKV associated nephropathy (BKVAN) occurred in 78, 99, and 7 patients, respectively. The median followed-up time was 63.6 (3.0-88.0) months. After reduction of immunosuppression, 81 (81.8%) patients cleared BK viruria with a mean time of (12.1 ± 1.9) months. When compared with non-BKVAN patients, BKVAN patients had a higher median peak level of BK viruria (2.07 × 10⁹ vs 9.28 × 10⁵ copies/ml, P=0.002), lower frequency of clearance (3/7 vs 78/92, P=0.006), longer BK viruria clearance time ((45.4 ± 6.4) vs (8.7 ± 1.5) months, P=0.001). The 1, 3, 5-year graft survival in BK viruria patients were 99.0%, 95.9% and 89.6% respectively, which were not significantly different from those in non-BK viruria patients (97.7%, 95.5% and 93.7%, P=0.289). Graft function of BK viruria patients were not statistical significance compared with non-BK viruria patients (serum creatinine level 5 years post-transplant: (105.7 ± 30.9) vs (111.3 ± 4.6) µmol/L, P=0.322). Graft function of BKVAN patients at 5 years post-transplant was stable without significantly difference from non-BKVAN patients (serum creatinine level: (127.6 ± 41.0) vs (108.3 ± 39.3) µmol/L, P=0.204).

CONCLUSION: On the premise of intensively and regularly BKV monitoring and preemptive reduction of immunosuppression, BK viruria and BKVAN can not impact on the long-term graft survival in renal transplant recipients.