Ultrastructural characterization of herpes simplex virus type 1 (strain 17) temperature-sensitive mutants.

We report the ultrastructural features associated with wild-type and temperature-sensitive (ts) mutant infection at non-permissive temperature for each of 18 herpes simplex virus type 1 (HSV-1) (strain 17) ts mutants. The mutants were classified by their ability to induce nucleocapsid-related structures: class I failed to induce any, class II induced empty and partially filled structures while class III induced all of the identified structures including those containing an electron-dense core. The time when expression of the ts lesion blocked virus replication was estimated for most mutants; this allows both mutant gene expression and the resulting ultrastructural features to be correlated with the sequence of virus replicative events. Three ts mutant-triggered features not previously described in HSV-1-infected cells were also recognized: a modification of rough endoplasmic reticulum, intranuclear accumulation of enveloped virus particles and cytoplasmic accumulation of novel doughnut-shaped particles having a concentric double ring appearance in thin section.