Moreover, blocking PD-1 in vitro resulted in an increase in IFN-γ expression in JCV-stimulated CD8+ T cells in an HIV-positive patient with active PML [55] and increased PD-1 and PD-L1 expression has been described in post-mortem PML lesion tissue [54••]. This evidence concerns the gene IFNG and progressive multifocal leukoencephalopathy.