Kidney transplantation is the treatment of choice for end stage renal disease (ESRD) improving the quantity and quality of life for dialysis patients. Although prolongation of graft survival in the short term by preventing the release is observed by immunosuppression (IS) powerful, the longer-term survival has not improved . Indeed, the IS can not only have a direct deleterious effect on the kidney transplant , but too weak IS can promote rejection, and too strong, promote the emergence of a viral disease polyomavirus BK ( BKV ) . BK nephropathy (BKVAN ) virus is accompanied by an irreversible impairment of the renal function , leading to a loss of the graft followed by a premature return to dialysis in at least 50 % of cases. Plasma BKV reactivation was observed mainly during the first year of transplantation in 15% of patients and complications annually BKVAN concern about 5 % of recipients . Currently , treatment options are very limited , only the decrease in IS shows a partially effective when care is early . There is no specific antiviral effective treatment of this disease . In addition, there is no way to predict which patients will develop BKV reactivation BKVAN despite lower tax.