Mechanism of demyelination after HSV type I intraocular injection in rabbits

Intraocular injection of herpes simplex virus (HSV) type I into the vitreous body of 18-day-old rabbits induced, on the 7th day post-inoculation, neurological signs with marked head jerking and atazia. Examination of semi-serial 1-micrometers thick sections of the whole lengths of right and left optic nerves and chiasma of 4--64 days post-inoculated rabbits revealed a small lesion, restricted to the medial side, which had extended 2--3 mm, during the first 4 days, along the optic nerve. Ahead of the developing lesion marked chromatin changes of neuroglial cells were noticed followed by cuffing of blood vessels, infiltration by macrophages, demyelination and remyelination. The present study indicated that demyelination occurred following the infection of the myelinating cells. It appeared that virus did not become latent and many cells survived the viral attack. Repeated episodies of viral activity caused further damage while repair did not keep pace.