Ultrastructural and virological aspects of Langat virus-induced SSPE in suckling hamsters

The morphology of subacute sclerosing panencephalitis (SSPE) lesions in hamsters following i.p. inoculation of Langat virus was studied by light microscopy and electron microscopy. The lesions' temporal relationship to virus presence and antibody production was studied by immunofluorescence, virus isolation from brains and brain cell cultures, and by antibody assay of serum and spinal fluid. All 10-day-old hamsters infected with Langat virus developed SSPE lesions, most prominently in the cerebellum, without any overt signs. The lesions appeared 10 days after infection, progressed in severity until Day 21 and persisted unaltered at least 3 months. They consisted of neuronal degeneration, calcification, and intracellular lipid accumulation. Virus was isolated from Days 3 to 15 and disappeared on Day 21. Demonstration by cerebellar immunofluorescence of viral antigen was observed 10 days after inoculation. Antibody appeared in the serum on Day 6, rose to very high titres by Day 21, and thereafter declined. Cell-associated virus was not demonstrable in negative brain-cell cultures. These findings suggest that SSPE in hamsters, associated with Langat virus infection, is biologically different from measles SSPE. Purkinje-cell lipid accumulation and mineralization sparing mitochondria were manifestations of the response of neurons to cell injury at the threshold of irreversibility.