Demyelination induced in mice by avirulent Semliki Forest virus. I. Virology and effects on optic nerve.

Swiss A2G mice were infected intraperitoneally with an avirulent strain of Semliki Forest virus. The virus titres in the optic nerves, retina and brain were estimated on post-inoculation days 3 to 8. High titres of virus were obtained in the optic nerve, retina and brain. The optic nerves, retina and brain were studied by light microscopy up to post-inoculation day 67. Electron microscope studies wee carried out on the optic nerve on post-inoculation days 11 and 14. Inflammatory, microcystic changes and demyelination seen in the optic nerve were similar to those found in he central nervous system.