Experimental latent herpesvirus infection in rabbits, mice and hamsters: ultrastructure of the virus activation in explanted gasseric ganglia.

The frequency of latent infection as established in trigeminal ganglia of rabbits, mice and hamsters with human herpesvirus type 1 (HVH) was compared using two different virus strains. Explantation proved to be effective in reisolation of HVH from ganglion tissue, which did not yield infectious virus at time of its removal. After healing of acute keratitis, the latent infection in homolateral gasseric ganglia of rabbits was detected at a relatively high frequency (60-80 per cent) up to 120 days post infection (p.i.) in case of both virus strains. The activation rate was a little lower in hamsters. After inoculation of suckling and young mice with a sublethal dose of HVH by oral and nasal routes, approximately 40-100 per cent of the animals had virus in their gasseric ganglia during the acute period; 30-60 days later only 10-25 per cent had virus in the latent form. Immunofluorescent and electron microscopic examination of the explanted ganglion tissue showed the presence of HVH in neurons, neuronal satellites and Schwann cells. The nuclei of noneural cells contained numerous crystalline arrays. The possibility that pseudounipolar neurons of the regional sensoric ganglion are not the exclusive site of HVH latency is discussed.