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Abstract Background and Aims Reactivation of the BK virus in immunosuppressed patients is a risk factor for the development of BKV nephropathy. Ten percent of transplant patients are affected by BKV nephropathy, and 50% of them experience graft loss. The purpose of this study is to assess the medium to long-term effects of an early immunosuppression reduction strategy in the presence of urinary and/or serum BKV replication in a large population of kidney transplant recipients from our center. Method A retrospective observational study was conducted on 681 patients from immediate post-transplant with at least 6 months of observation. 91.5% of them were on the same immunosuppressive therapy (MMF, Steroid, tacrolimus). A total of 16200 samples were collected from blood and urine simultaneously for PCR quantification of BKV over a post-transplant period of 54.4 ± 34.2 months. Immunosuppression reduction began after two repeated biweekly detections of viruria 105 copies/ml and/or viremia 103 copies/ml. Results 35% of cases tested positive for viruria, with 19% also positive for viremia. Onset and peak viruria and viremia were observed at 4.1 ± 3.3 months and 4.2 ± 3.5 months, and 5.3 ± 4.6 and 5.4 ± 4.1 months, respectively. Viruria negativization occurred in 79.4% of patients after 13.2 ± 9.7 months, while viremia disappeared in 94.6% after 9.2 ± 7.5 months. In 5 patients with persistent viruria and viremia, therapy with Cidofovir or Leflunomide was initiated following biopsy. 14.3% of patients with persistent viruria maintained low replication and stable renal function. No episodes of acute rejection occurred. Only one case of irreversible BKV nephropathy was observed. Conclusion Timely reduction of immunosuppression allows excellent control of BKV replication, stability of renal function in the medium to long term, and makes the occurrence of irreversible chronic BKV nephropathy rare.
Iafisco et al. (Wed,) studied this question.