For instance, when a recombinant HSV-1 constitutively expressing interleukin-2 (IL-2) was inoculated into mice, it provoked CNS demyelination and optic neuropathy, whereas infection with recombinant viruses expressing IL-4, gamma interferon, IL-12p35, IL-12p40, or IL-12p70 did not induce this effect [131]. Here, IL2 is linked to infection.