Virus-associated demyelination. A model using avirulent Semliki Forest virus infection of mice.

Lesions produced by the infection of Swiss/A2G mice with a single inoculation of an avirulent strain of Semliki forest virus have been studied by light and electron microscopy. Whilst a mild encephalitis was detected in the great majority of mice infected, focal areas of myelin loss were observed in the cerebellar white matter of only 25% of cases. The incidence of myelin loss in other strains of mice ranged from 21% in BSVS mice to 8% in SJL/J mice. The possible mechanisms involved in the pathogenesis of the myelin loss are discussed.