Neural spread of herpes simplex virus types 1 and 2 in mice after corneal or subcutaneous (footpad) inoculation.

Twelve herpes simplex virus (HSV) strains, 6 of each type, were inoculated subcutaneously into the left hind foot and into the cornea of the right eye of 12-day-old Swiss albino mice. The neural spread of virus to trigeminal and spinal ganglia and to brain and spinal cord was studied by demonstration of infective virus, histology and electron microscopy. Type 1 and type 2 infections seemed to spread equally well by intra-axonal transport. Using a protein tracer (horseradish peroxidase) injected into the same site as the virus, transport of the tracer to neurons corresponding to those infected with virus was observed. The extensive destruction of CNS tissue in the transitional region of the trigeminal root where CNS and the peripheral nervous system meet is discussed with reference to the pathogenesis of HSV encephalitis.