Ultrastructural study of lesions induced in rabbit cornea by Herpes Simplex virus types 1 and 2

Herpes simplex virus types 1 and 2 were used to infect rabbit corneas (without abrasion), and the resulting lesions were compared by light and electron microscopy. The type 1-induced lesion developed more quickly; the infected epithelial cells underwent a progression of defined morphological changes leading to organelle destruction, cell rounding, and death. Virus particles were abundant in the nuclei and cytoplasm of all types of cell in the epithelium, in intercellular spaces, and on the basement membrane. Occasionally, virus was seen to replicate within stromal fibroblasts. In contrast, type 2, although causing similar changes in the epithelial cells, was relatively inefficient in the production of mature virions. Thus type 2 nucleocapsids were synthesized within nuclei in numbers comparable to those of types 1, but intact cytoplasmic virions were uncommon, apparently because of degradation of type 2 virions in cytoplasmic vesicles or tubules. Extracellular type 2 particles were rarely seen. This finding offers an explanation for the relatively slow development of the type 2-induced lesion, but not for its greater severity. All epithelial cells appeared to be capable of supporting replication of either type of virus.