Demyelination in mice after two or three infections with avirulent Semliki Forest virus

Abstract

Adult mice give 2 or 3 i.p. inoculations with avirulent Semliki Forest Virus showed typical lesions of a viral encephalitis similar to those caused by a virulent strain of the virus. Demyelination also was seen in the medulla and in the folia of the cerebellar white matter. Neuronophagia was seen only in mice that had had 3 successive infections. The repeated inoculations of avirulent virus exacerbates the encephalitis as seen after a single inoculation and causes demyelination. The mice did not have neurologic clinical signs except for a short lived weakness of the hind legs. No central nervous system lesions were seen by the 7th and 8th wk after the initial infection and all mice rcovered.