Surveillance and modification of immunosuppression minimizes BK virus nephropathy

Infection of a transplanted kidney with the polyomavirus, BK, is associated with poor allograft survival.

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.

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.

Active surveillance for BK virus by urine/plasma PCR with prompt reduction in immunosuppression can prevent BK nephropathy.