Initiation of a screening protocol for polyoma virus results in a decreased rate of opportunistic non-BK viral disease after renal transplantation.

BACKGROUND: Polyoma BK virus nephropathy (PVN) is a leading cause of renal allograft injury and loss. The mainstay of treatment, as there are no target therapies approved by the US Food & Drug Administration, is reduction in immunosuppression. However, current approaches are shifting to screening for viremia as an indicator of oncoming nephropathy, with subsequent reduction in immunotherapy. We attempted not only to replicate these data but also to evaluate the utility of polyoma viremia as a surrogate marker for overimmunosuppression in general, thus allowing prevention not only of PVN but also of other viral opportunistic infections such as cytomegalovirus (CMV) and Epstein-Barr virus (EBV) disease.

PATIENTS AND METHODS: We conducted a retrospective cohort analysis of renal transplant recipients at our center. The historical controls (2003-2005, n = 134) had received their allograft before the institution of a monthly serum polymerase chain reaction (PCR) polyoma screening protocol. The screened cohort received their allograft afterwards (2006-2008, n=134). Screening was performed using PCR techniques with prompt reduction in immunosuppression for viremic patients. The patients were followed for the development of PVN, acute rejection, renal allograft function, and survival.

RESULTS: Polyoma viremia was noted in 16% of the screened population, with none developing PVN after prompt reduction of immunosuppression. Clearance of the viremia occurred by 6 months in 95% of the patients after reduction of immunotherapy. No patient in the screened group developed CMV or EBV disease. Of the controls, 7 (5%) developed PVN and 12 (9%) developed CMV or EBV disease, compared with none of the screened patients (P<0.05). The incidence of acute rejection was comparable between the groups (4% controls, 5% screened). No deleterious effects were noted on patient or allograft survival, allograft function (measured by serum creatinine), rates of fungal infection, or the rate of post-transplant lymphoproliferative disorder in the screened patients.

CONCLUSIONS: Monthly PCR monitoring for BK viremia, together with a modest decrease in immunotherapy, is not only safe but also effectively prevents PVN and is associated with a significantly decreased rate of CMV and EBV disease in renal transplant patients. BK viremia may also serve as a surrogate marker for overimmunosuppression.