Induction of chronic measles encephalitis in C57BL/6 mice.

Chronic measles encephalitis was induced in C57BL/6 mice with the hamster neurotropic strain of measles virus when virus which had been passaged at low dilution in the brains of suckling C57BL/6 mice was inoculated intracerebrally into 1- to 6-month-old mice. One-third to two-thirds of mice surviving the acute infection were consistently found to develop chronic neurologic dysfunction within 3 weeks to 1 year post-infection. The acute mortality was higher in males than in females and showed a slight decline with increasing age in males. Indirect immunofluorescence (IF) studies using measles virus-specific sera from a subacute sclerosing panencephalitis patient and from a hyperimmune rabbit demonstrated abundant viral antigen in regions of telencephalon and diencephalon correlated with the appearance of typical central nervous system signs in both acute and chronic disease. Viral antigen was found in infected neurons in the grey matter. Deposition of immune complexes was minimal as observed in adjacent brain sections stained with goat anti-mouse antibody by direct IF. Occasional necrotic foci and perivascular cuffing were observed in brains from chronically infected mice.