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Viral Origin, Clinical Course, and Renal Outcomes in Patients With BK Virus Infection After Living-Donor Renal Transplantation

Background BK virus (BKV) nephropathy remains the main cause of renal graft loss after living-donor renal transplantation. The aim of the study was to investigate the source and factors influencing the course of BKV infection. Methods We investigated 214 living donor-recipient pairs. Urine and blood of donors and recipients were tested by qPCR for the presence of BKV DNA before and after transplantation; genotyping of BKV subtypes was performed. Results Eighty-five recipients (40%) had posttransplant BK viruria including 61 with additional viremia and 22 with nephropathy. Pretransplant urinary BKV shedding of donor or recipient was a significant risk factor for posttransplant viruria and viremia (OR, 4.52; CI, 2.33-8.77; P < 0.0001) and nephropathy (OR, 3.03; CI, 1.16-7.9; P = 0.02). In the BKV nephropathy group, urine and blood became BKV positive earlier than in the group with viruria and viremia. Renal function was worse in BKV-nephropathy compared with BKV-negative patients beginning at transplantation. Comparing BKV subtypes of donor and recipient before with the subtype of the infected recipient after transplantation, donor-derived transmission was identified in 24 of 28 corresponding pairs. BKV subtype IV had a higher prevalence in recipients with BKV nephropathy than in those with viruria and viremia (P = 0.045). Conclusions Pretransplant urinary BKV shedding of donor and recipient is a risk for posttransplant infection. Donor-derived BKV transmission is an important mode of infection. BKV subtype IV may be one of the viral determinants. Early BKV positivity of urine and blood indicates later BKV nephropathy. Decreased renal function may favor BKV infection.