ISG15 and primary effusion lymphoma: Numerous ISGs were strongly upregulated in primary human oral fibroblasts latently infected with Kaposi’s sarcoma-associated herpesvirus (KSHV) and in KSHV-positive primary effusion lymphoma cells, while knockdown of ISG15 or the ISG15 ligase HERC5 induced virus reactivation and the release of infectious virus [74,75].