Quantification of BKV in urine and plasma in renal transplant recipients at PVAN (Polyomavirus-associated nephropathy) risk

Background. BKV infection usually occurs in early childhood through the respiratory tract.The virus persists in a latent form in the kidney and it could be reactivated under favorable condition.The most important clinical manifestations affect kidney transplanted in which the BK polyomavirus nephropathy (PVAN) can lead to kidney failure. Objectives. The aim of our study was to evaluate the clinical utility of quantification of BKV viruria and especially viremia detected by real-time PCR method to select the patients at risk of PVAN. Study Design. We carried out a quantitative (dosing) assay of BKV-DNA in 24 patients transplanted in Salerno’s hospital, or elsewhere, all treated with cyclosporine or tacrolimus and mycophenolate mofetil or Prednisolone. The enrollment was made on the basis of impaired renal function, in particular of the values of serum creatinine (> 25% of baseline level) and / or appearance of proteinuria. The nucleic acid extraction was performed by EXTRAgen kit (Nanogen); the extracts were submitted to quantitative evaluation by BKV Q-PCR Alert Kit indicare regione target in Real Time PCR (Nanogen) using the instrument ABI7300 (Applied Biosystems). Results. 16 patients were negative both for viremia and viruria,4 patients showed positive viruria but viremia <10,000 copies / ml, 4 patients showed positive viruria and viremia > 10,000 copies / ml. In the last group, biopsy, performed to diagnose PVAN was positive and immunosuppressive therapy was reformulate leading to the decline, but never to the negativity of viral load. Conclusions. The renal impairement combined with the quantification of BKV’s viral load in urine and especially in plasma, can also be effective predictors of PVAN.