BK Virus Infection in Renal Allograft Recipients

Abstract

BK VIRUS, a nonenveloped, double-strand DNA virus, is one of the widely spread human polyoma viruses. BK virus infection is associated with disease in humans. In healthy individuals, BK virus resides in a latent state in the kidney and can be activated without functional impairment or ill effects. But BK virus causes disease more frequently in immunosuppression patients, including those with AIDS or renal transplants. Three renal allografted patients with high serum creatinine values presented clinical symptoms of rejection. Cells containing viral inclusion bodies (decoy cells) were detected in the urine cytology. Sections of renal allograft biopsy tissue showed infiltration of mononuclear cells in the tubulointerstitium and nuclear enlargement with inclusions in the tubular epithelium. Immunohistochemical stains for SV40 antigen showed positive nuclear staining in BK virus-infected tubular epithelium. Electron microscopy showed paracrystalline arrays of naked viral particles with a diameter 45 nm. BK virus infection in renal allograft recipients has become more frequent since the prescription of new immunosuppressive agents. The morphologic char- acteristics and the diagnostic methods for BK virus infec- tion must be analyzed. Although asymptomated BK virus infection has been documented by urine cytology, other diagnostic tools as well as the clinical course of biopsy- proven interstitial nephritis have not been well defined.