Cynomolgus polyoma virus infection: a new member of the polyoma virus family causes interstitial nephritis, ureteritis, and enteritis in immunosuppressed cynomolgus monkeys.

Polyoma virus infection causes acute interstitial nephritis and ureteral stenosis in humans but has rarely been noted in other species. In the present study, a hitherto unknown polyoma virus was detected in 12 of 57 cynomolgus monkeys after 3 to 11 weeks of immunosuppression given to promote acceptance of renal allografts or xenografts. This virus, termed cynomolgus polyoma virus (CPV), is antigenically and genomically related to simian virus 40 (SV40). The tubular epithelial nuclei of the collecting ducts in the medulla and cortex reacted with an antibody for the SV40 large T antigen and by electron microscopy contained densely packed paracrystalline arrays of 30- to 32-nm diameter viral particles. A polymerase chain reaction analysis of DNA extracted from affected kidneys detected polyoma virus sequences using primers for a highly conserved region of the large T antigen of polyoma virus. Sequence analysis showed 7 base substitutions and 3 to 5 deletions in the 129-nucleotide segment of amplified products, compared with the corresponding portion of SV40, yielding 84% homology at the amino acid level. CPV caused interstitial nephritis in six renal allografts, a xenograft kidney, and six native kidneys. Infected animals showed renal dysfunction and had tubulointerstitial nephritis with nuclear inclusions, apoptosis, and progressive destruction of collecting ducts. CPV was detected in the urothelium of graft ureters, associated with ureteritis and renal infection. Viral infection was demonstrable in smooth muscle cells of the ureteric wall, which showed apoptosis. One animal had diarrhea and polyoma virus infection in the smooth muscle cells of the muscularis propria of the intestine. Spontaneous resolution occurred in one case; no animal had virus detected in tissues more than 3 months after transplantation. Thus, immunosuppression predisposes cynomolgus monkeys to a polyoma virus infection with clinical consequences quite similar to BK virus infection in humans, including renal dysfunction. We also suggest that this may be the pathogenetic basis for the significant incidence of late onset, isolated ureteral stenosis observed in these recipients.