Molecular characterization and sequence analysis of polyomavirus BKV-strain in a renal-allograft recipient

The significance of polyomavirus (PV) infection was investigated in a 53-ye ar-old patient who underwent renal transplantation and was treated; with tr iple immunosuppressive therapy (tacrolimus, prednisone, and azathioprine). A renal biopsy taken because of the suspicion of acute rejection showed foc al inflammatory interstitial infiltration, tubulitis, and tubular cell nucl ear changes consistent with the hypothesis of viral infection. Both the tub ular and decoy cells identified by means of urinalysis positively stained f or anti-SV40 antibody. Polymerase chain reaction performed on the DNA extra cted from renal tissue and isolated from urine showed the presence of an an tigenic variant (AS) of the BKV archetype after sequence analysis of the tr anscription control region (TCR). On the basis of the diagnosis of BKV infe ction, immunosuppressive therapy was reduced. The patient's renal function improved and was still stable 8 months later when urinalysis showed only a few decoy cells, which were found to be infected by JC but not BK virus. Th ese data suggest that only the BKV, probably favoured by immunosuppressive therapy (tacrolimus), causes renal damage. It is worth underlining that eve n small and sporadic viral genome mutations may lead to pathologic effects. Copyright (C) 2001 by W.B. Saunders Company.