Recurrent demyelination in chronic central nervous system infection produced by Theiler's murine encephalomyelitis virus

A morphologic study of demyelination produced by Theiler's encephalomyelitis virus (TMEV) infection in C3H/He mice was performed. Demyelination in this strain of mouse was less intense and had a milder gliomesodermal response than that observed in SJL mice. As early as 80 days after infection numerous remyelinated axons were present in C3H/He mice, and later, extensive remyelination was observed and was mainly by Schwann cells. About one-third of remyelinated plaques showed recurrent demyelinating activity at 200 days. The best evidence of recurrent demyelination was the loss of myelin by axons which had been previously remyelinated by Schwann cells. In addition, acute areas of demyelination were also seen in spinal cords which contained chronic or quiescent plaques. The demonstration of recurrent demyelination in TMEV infection is important for it increases the relevance of this model to multiple sclerosis (MS). In addition TMEV infection of C3H/He mice appears to be an excellent model for further studies of Schwann cell remyelination and recurrent demyelination in the central nervous system (CNS).