Analysis of proteolipid protein and P0 transcripts in mice infected with Theiler's virus.

Inbred strains of mice vary in their susceptibility to the chronic inflammatory and demyelinating disease caused by Theiler's virus. The severity of this disease depends on the extent of demyelination but also on the occurrence of remyelination. We studied the extent of demyelination and remyelination in mice with different genetic backgrounds. To estimate the extent of demyelination, we analyzed the abundance of proteolipid protein (PLP) transcripts in the spinal cord 45 days after inoculation. RNA transcripts were quantitated at the single cell level using in situ hybridization. We observed a correlation between the reduction of PLP mRNA and the extent of inflammation in the SJL/J, C3H, F1 SJL x C3H and C3H.Q strains. Remyelination by Schwann cells was estimated by the detection of P0 mRNA and was observed in C3H mice only. It is likely that intense inflammation in highly susceptible strains prevents the migration of Schwann cells into the central nervous system (CNS).