Distribution of Theiler's virus in the CNS of athymic nude mice: effect of varying the route of inoculation.

Immunohistochemical and ultrastructural techniques were used to map the distribution of Theiler's virus in the central nervous system (CNS) of the nude mouse, after intracerebral (i.c.), intravenous (i.v.) or intraocular (i.o.) inoculation. Expression of viral antigen was largely restricted to the subthalamus, substantia nigra, ventral tegmental tract and the grey and white matter of the spinal cord. Electron microscopy showed paracrystalline arrays of viral particles within neurons in the substantia nigra and spinal cord. Inoculation of virus i.v. or i.o. rather than i.c. delayed the onset of neurological signs but did not affect the distribution of virus within the CNS. In particular, there was no evidence of spread along the optic pathways after i.o. inoculation. The localization of Theiler's virus within certain regions of the CNS seems to depend on differential susceptibility to infection or differential restriction of replication rather than on the route of inoculation.