Effect of Mycophenolate Mofetil Dose on BK Virus Infection in Kidney Transplant Recipients

Background: Intensity of overall immunosuppression is a risk factor for BK virus infection (BKVI). However, the exact impact of exposure to tacrolimus and mycophenolate mofetil (MMF) to BKVI is unclear. The aim of this study was to determine if BKVI in kidney transplant (KT) recipients (KTR) is associated with drug exposure to MMF. Methods: This prospective randomised controlled clinical trial (NCT01860183) included 36 KTR who underwent KT from May 2013 to February 2015 at Clinical Hospital Merkur. Immunosuppression consisted of basiliximab induction, with tacrolimus, MMF ±steroid maintenance. KTR were randomized in two groups, with respect to MMF dose (2g or 3 g daily). Urine cytology for decoy cells was performed at prespecified time-points posttransplant. KTR were followed up to 12 months post KT. Graft biopsy was performed per protocol at 2, 6 and 12 months, or in case of graft dysfunction. Kaplan-Meier analysis with log-rank test was used to assess graft survival. A Cox regression was used to determine variables associated with graft survival. Results: 13 (37.1%) KTR had decoy cells in urine, 4 (11.4%) KTR had biopsy-proven BK virus-associated nephropathy (BKVAN). The mean time-to-occurrence was 4.8 months for decoy cells and 4.3 months for BKVAN. Cumulative one-year overall graft survival was 93.5%. Incidence of decoy cells, BKVAN, or acute rejection was similar in the two MMF groups. Rejection was not a risk factor for decoy cell positivity or for BKVAN. Conclusions: MMF dose may not increase risk for BKVI after kidney transplantation.