Postinflammatory remyelination in the spinal cord of mice infected with mouse hepatitis virus, JHM strain.

The spinal cords in mice surviving acute infection for 30 days following lumbar inoculation with mouse hepatitis virus, JHM strain, were examined for virus growth and pathologic changes by light and electron microscopy. Virus titer reached a maximum level on day 6 postinoculation (p.i.) and became negative on day 10 p.i. On days 5 to 10 p.i. there were severe disruption of myelin sheath and marked phagocytosis of myelin by macrophages. Viral particles were seen in degenerating glial cells. On days 15 to 20 p.i. proliferation of oligodendrocytes was noticed in association with thinly myelinated axons with decreased number of macrophages. On days 25 to 30 p.i. affected axons were mostly remyelinated by oligodendrocytes and the interaxonal space was packed with the processes of fibrous astrocytes containing myelin debris and lipid droplets. In the subpial areas of more widespread lesions some axons were remyelinated by Schwann cells.