Immune cell infiltration in corneas of mice with recurrent herpes simplex virus disease

Reactivation of latent herpes simplex virus type 1 (HSV-1) infection was induced by UV irradiation of the corneas of latently infected mice. On days 1-4 after stimulation, infectious virus was sought in nervous and ocular tissue. On days 4, 7 and 10, eyes with either recurrent epithelial or stromal disease and appropriate controls were stained to identify immune cells and HSV-1 antigens. The maximum incidence of infectious virus was on day 2 when 5/10 ophthalmic parts of the trigeminal ganglion yielded HSV. Thus in this mouse model, as in humans, reactivation of virus in the trigeminal ganglion is the likely source of virus producing recurrent disease and shedding in the tear film. On day 4, when virus antigens were still present, granulocytes were the predominant infiltrating cell in corneas with either type of disease. Small numbers of T cells, dendritic cells and cells expressing MHC class II were also present. In stromal disease, the granulocyte infiltrate persisted and T cells remained sparse. In contrast, in epithelial disease, granulocyte numbers rapidly declined and both CD4+ and CD8+ T cells (present at a ratio of 1:1) increased significantly. The secondary immune response to virus antigen is more rapid and vigorous than that during primary corneal infection. Granulocytes may play a role in the initial clearance of virus, however, the other types of cells present early on provide the potential for a local secondary immune response. The high proportion of CD8+ cells in epithelial disease compared with stromal disease suggests that they may be acting as suppressors.