Differences in neurovirulence among isolates of Herpes simplex virus types 1 and 2 in mice using four routes of infection.

Differences in neurovirulence between herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) were investigated using recent clinical isolates and laboratory-passaged strains in intravaginal, intranasal, intraperitoneal, and intracerebral infections of mice. The HSV-2 isolates caused higher death rates in all four infections. No differences in death rate were observed between recent and passaged isolates of either HSV-1 or HSV-2. After intravaginal inoculation, HSV-1 isolates replicated to higher titers in the vaginal mucosa, but HSV-2 isolates produced a higher death rate and a greater frequency of latent infection in lumbosacral ganglia of surviving animals. After intranasal inoculation, HSV-2 isolates again produced a higher death rate, but the frequency of latent infection in trigeminal ganglia was higher with HSV-1 isolates. The data suggest that the HSV-2 isolates have an enhanced capacity to enter and replicate in the central nervous system of mice but that latency is influenced by both virus type and route of inoculation.