Treatment with indoleamine dioxygenase-1 (IDO1) inhibitors reduced both viremia and B cell transformation in animal models of post-transplant lymphoproliferative disorder (PTLD), while IDO1 up-regulation occurred in patients who would go on to develop PTLD. The findings, which were reported in the May 24, 2024, issue of Science by researchers from the University of Basel and the University Hospital Basel, point to new ways to predict, prevent and treat complications of Epstein-Barr virus (EBV) infection.