Mammalian target of rapamycin signal inhibitors could play a role in the treatment of BK polyomavirus nephritis in renal allograft recipients.

UNLABELLED: BK virus (BKV) nephropathy is a common viral infection in renal transplant patients, with a prevalence of 1-9% at approximately 12 months after surgery. While it is widely agreed that reduction of immunosuppression should be the first intervention after diagnosis of BKV infection, there is no consensus on whether calcineurin inhibitors or antiproliferative drugs should be reduced first. Furthermore, target levels of immunosuppressive drugs are poorly defined, as are criteria for replacing one immunosuppressive agent with another.
RESULTS: We report our series of 15 renal transplant patients who underwent surgery between September 2004 and March 2010 and who developed BKV infection. The first 8 patients were treated with reduction of immunosuppression; 7 of these patients received cidofovir and 6 received intravenous immunoglobulin. The remaining 7 renal transplant recipients received mammalian target of rapamycin inhibitors (imTOR). In this group, we observed faster and more efficacious BKV clearance in plasma and urine and a steady improvement in allograft function, with no episodes of acute allograft rejection during follow-up. The polymerase chain reaction assay for BKV in urine became positive in 2 patients in whom imTOR were stopped due to severe side effects.
CONCLUSIONS: The use of imTOR should be considered a first step in the treatment of renal transplant recipients with BKV infection. In our experience, this change in treatment was safe and resulted in viral clearance.