In renal transplantation, BK virus may contribute to graft dysfunction and graft loss. While reduction in immunosuppression is considered standard therapy for infection, data has suggested a role for cidofovir (CID). The purpose of this study was to describe the course of BK infection in CID-treated patients. Kidney transplant recipients with confirmed BK viremia (BKV) or biopsy-proven nephropathy (BKN) and treated with CID (0.25 – 1 mg/kg every 2 weeks) from 01/2007 through 06/2012 were included in the analysis. Patients with <6 months follow-up after initiation were excluded. Baseline characteristics of the 68 included patients are shown below. Mean BKV at baseline was 5.2 ± 1.0 log₁₀copies and mean time from diagnosis to CID initiation was 1.4 months. At 6 and 12 months of treatment, respectively, 44% and 64% of patients achieved negative BKV. Independent factors associated with persistent BKV at 6 months included older age, delayed graft function, higher baseline BKV, and lack of BKV reduction by 1 log₁₀copies at 1 month of treatment. Gender, ethnicity, induction therapy, transplant type, and presence of BKN did not correlate with clearance at 6 months. Overall time to BKV clearance was 7.4 months, after a mean of 16 ± 11 CID doses. For the entire cohort, creatinine at the end of treatment increased by 39% from baseline. Patients BKV(+) at 6 months had a significantly greater rise in creatinine at the end of therapy compared to BKV(-) patients (68% vs. 1.4%; p=0.008). Repeat biopsies were performed in 20 of 44 patients with BKN and demonstrated histological clearance in 16 (80%) cases, while 3 graft losses occurred due to BK. These data provide insight into the course of BK infection in patients treated with CID. Clearance of BKV at 6 months post-treatment may be associated with maintenance of stable renal function at the end of therapy.

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