BK virus-induced renal allograft nephropathy.

BK virus nephropathy (BKVN) is a serious opportunistic infection threatening renal function especially during the first year after transplantation. Its incidence is now on the rise and is closely related to the level of the recipient's immune system inhibition. This is more intensive with current trends in transplantation medicine, where more potent immunosuppressive protocols are used and more aggressive antirejection therapy is applied. In the absence of BK virus (BKV) specific therapy and limited treatment options for advanced BKVN, active screening of BKV replication and subsequent preemptive adjustment of immunosuppression are essential measures to prevent BKVN. However, it remains unclear how to modify immunosuppressive protocols as well as how to address initial stages of BKV replication. This comprehensive review summarizes the currently applied and not completely uniform procedures for the detection, prophylaxis and therapy of BKV replication and BKVN. The pitfalls brought by reduced immunosuppression, as a typical response to a significant viral replication or a developed BKVN, are also mentioned, particularly in the form of graft rejection. The paper also outlines the authors' experiences, and lists currently ongoing studies on the subject. The perspectives of new, especially immune-based, procedures in the treatment of complications associated with BKV infections are highlighted. Different views on the management of patients indicated for kidney re-transplantation whose previous graft failed because of BKVN are also discussed.