BK Virus-associated Nephropathy in Renal Allograft Recipients: Rescue Therapy by Sirolimus-based Immunosuppression

Background: BK virus nephritis (BKN) in recipients of renal allografts has reemerged during the past 5 years. Despite increased incidence, therapeutic options remain limited and progression of the disease often leads to allograft failure.

Methods: From May 2002 to July 2002, we performed protocol biopsies in 25 recipients of kidney allografts with progressive allograft dysfunction; three patients demonstrated unexpected histopathologic features of BKN. We tested the hypothesis that replacement of their lymphocytotoxic and nephrotoxic immunosuppression (combination of mycophenolate and tacrolimus) with sirolimus- and prednisone-based therapy can lead to disappearance of the virus without increasing the risk of acute rejection.

Results: During the median follow-up of 18 months after sirolimus and prednisone therapy, decoy cells disappeared first, followed by progressive decrease in the median plasma BK virus-DNA load, and undetectable levels at the last follow-up. Patients remained free of acute rejection, and follow-up median estimated creatinine clearance increased to 67 mL/min (range 62-75 mL/min) from 52 mL/min (range 51-54 mL/min) at the time of diagnosis.

Conclusions: Further studies are needed, but at present these preliminary results offer a new direction for therapeutic intervention in recipients of renal allografts with BKN.