IL4 and infection: In contrast, demyelination was not detectable after infection of the mice with wild-type (wt) HSV-1 alone or infection of the mice with the HSV-IL-4 or HSV-IFN-γ viruses, which are identical to HSV-IL-2 except that they express IL-4 or IFN-γ instead of IL-2 [17], [18].