Extracorporeal photopheresis for refractory BK virus-associated nephropathy in kidney transplantation.

Background: BK virus-associated nephropathy (BKVAN) remains an important risk factor for kidney graft loss. The current strategy to treat the BKVAN consists in reducing immunosuppressants. However, this strategy increases the risk of graft rejection, especially in highly sensitized patients or those with previous rejection episodes. Extracorporeal photopheresis (ECP) has been used for the treatment of T cell-mediated disorders, such as solid organ rejection in cardiac, lung and hepatic transplantation, due to its immunotolerogenic effect. In addition, some data suggest that ECP might also have an immunogenic effect, generating an immune response against infections. Methods: Herein we present a single-center case series of 13 patients with refractory histological-diagnosed BKVAN, where ECP was used after the failure of standard therapy. The cohort had a median age of 51 years (interquartile range 42-59), with 46% considered low immunological risk (cPRA 0%) and 54% high risk (cPRA >50%). ECP was initiated a median of 21.3 weeks (5.9-49.1) after BKVAN diagnosis, with patients receiving a median of 11 sessions (10-20). Results: After starting ECP, serum BK viral load significantly decreased by 55.3%, 95.9%, 99.7% and 99.9% at 3, 6, 12 and 18 months after ECP, respectively, while kidney function slowly decreased but at a lower rate than the historical group not treated with ECP, and no adverse events were observed. Despite the reduction in immunosuppression, only one patient experienced graft rejection during follow-up, with no major impact on graft function. Conclusion: These findings indicate that ECP may provide potential therapeutic benefits for BKVAN and could warrant further investigation in the context of kidney transplantation.