Nephrotoxicity of calcineurin inhibitors as a risk factor for BK polyomavirus replication after kidney transplantation.

BACKGROUND BK polyomavirus-associated nephropathy (PyVAN) is responsible for significant percentage of transplanted kidneys prematurely terminating their function. Its occurrence is closely related to the intensity of immunosuppressive therapy. METHODS In a group of 161 newly transplanted patients we prospectively evaluated 457 protocol renal biopsies performed within the first year after transplantation. Using the calcineurin inhibitors nephrotoxicity score, the incidence of nephrotoxicity was monitored as a manifestation of excessive immunosuppression. Findings were correlated with clinical evidence of active BK polyomavirus (BKPyV) replication and PyVAN. RESULTS Compared to the normal histology, nephrotoxicity was associated with more frequent BKPyV viraemia and viruria (P = 0.01 and P < 0.01, respectively) and more common occurrence of PyVAN. The persistence of toxicity in the subsequent biopsy proved to be a negative risk factor of viraemia and viruria (P = 0.03 and P < 0.01, respectively), independently of the initial BKPyV status. Toxicity could also be used as a predictor of viraemia and viruria (P = 0.04 and P < 0.01, respectively) even in the absence of viral replication at the time of initial biopsy. CONCLUSIONS Early histological manifestation of calcineurin inhibitors nephrotoxicity was associated with significant BKPyV reactivation in the risky first posttransplant year. This article is protected by copyright. All rights reserved.