Immunocytochemical localization of MAG, MBP and P₀ protein in acute and relapsing demyelinating lesions of Theiler's virus infection

Acute demyelinating and relapsing demyelinating lesions from spinal cords of mice infected with the WW strain of Theiler's encephalomyelitis virus (TMEV) were studied immunocytochemically with antisera to various myelin constituents. Acute lesions were studied for differences in the distribution of myelin basic protein (MBP) and myelin associated glycoprotein. (MAG). Relapsing lesions, characterized by demyelination of areas previously remyelinated by Schwann cells, were studied for differences in the distriution of P₀ and MAG. In both instances the earliest lesions were characterized by preferential disappearance of MBP and P₀ respectively when compared to MAG. In well-developed lesions, MAG, MBP and P₀ were absent in essentially equal proportion. These observations are in agreement with previous findings suggesting a primary loss of myelin rather than a direct attack on oligodendrocytes as the main pathogenetic mechanism of demyelination in this viral model.