BK virus infection in kidney transplant patients.

Polyoma BK virus is associated with graft dysfunction leading to BK viral nephropathy (BKVN) in 1-10% of kidney transplant recipients, moreover 30-80% of kidney transplant recipients experience asymptomatic reactivation of the virus that does not result in BKV associated damage of the renal allograft. The first aim of this study was to introduce monitoring of BK virus replication in the blood and urine of patients within first year after transplantation. Risk factors were evaluated and limit values for viremia and viruria for BKVN development was established. Positive BK viruria >107 copies/ml and positive BK viremia >104 copies/ml occurred in 25.8% and 5%; respectively. 3 patients out of monitoring study developed BKVN. Using ROC analysis, limit values for the development of BKVN were set at 103 copies/ml serum for BK viremia and 6.7x107 copies/ml BK viruria. The second objective was to determine the expression profile of the immune genes in kidney biopsies in three groups of patients with varying degrees of reactivation of the BK virus (without virus reactivation, with asymptomatic viruria, BKVN). 90 genes of immune response were measured by the TaqMan® low density array RT-qPCR. The analysis of biopsies from patients with non-signalling viruses led to the identification of 5 differentially..