Surveillance and Modification of Immunosuppression Minimizes BK Virus Nephropathy

Abstract

Background/Aims: Infection of a transplanted kidney with the polyomavirus, BK, is associated with poor allograft survival. Methods: In an attempt to prevent this transplant complication, we studied 144 consecutive transplant recipients for the presence of BK infection with plasma and urine PCR testing at 1, 2, 3, 6 and 12 months. Viruria alone was followed by serial studies. If plasma PCR became positive at >2.6 log copies, mycophenolate was reduced until there was no detectable plasma viral load. Results: Urine PCR was positive in 34 (24%), while plasma PCR turned positive in 22 cases (15%). No patients developed viremia with <6.8 log copies in the urine. Viremia resolved within 3 months or less in 20 of 22 patients after reduction of immunosuppression. Surveillance biopsies at 2 and 6 months revealed no BK nephropathy. Eight patients had acute rejection during reduced immunosuppression; however, all of these reversed with pulse steroids. Patient and graft survival at 1 year was 99 and 98%, respectively. Use of the cell-mediated immunity assay (ImmuKnow®, Columbia, Md., USA) was not useful in identifying infected patients. Conclusion: Active surveillance for BK virus by urine/plasma PCR with prompt reduction in immunosuppression can prevent BK nephropathy.