In vitro studies in mouse embryonic fibroblasts (MEFs), mouse lung fibroblasts and RAW 264.7 cells have demonstrated an antiviral role for Isg15 during Sindbis virus20, vaccinia virus16, Ebola virus21, Dengue virus and West Nile virus22 infection, although there are several reports of viruses exhibiting no enhanced replication in the absence of Isg15 (murine gammaherpesvirus 68, HSV-1, Sindbis virus, IAV14). The gene discussed is ISG15; the disease is infection.