Role of MIP-2 in neutrophil migration and tissue injury in the herpes simplex virus-1-infected cornea.

Neutrophils are the most prominent cell type to migrate initially into the herpes simplex virus type 1 (HSV-1)-infected murine cornea. The role the C-X-C chemokines macrophage inflammatory protein (MIP)-2 and KC play in promoting this response was investigated. MIP-2 and KC were quantitated by enzyme-linked immunosorbent assay. Neutralization of endogenous MIP-2 and KC was achieved by subconjunctival inoculation of the appropriate antibody. Infected corneas were examined immunohistochemically for infiltrating leukocytes and assayed for myeloperoxidase activity using the dye o-dianisidine. Depletion of neutrophils and natural killer cells was accomplished by intraperitoneal administration of RB6-8C5 and asialo GM1 antibodies. Herpes simplex virus type 1, when introduced intracorneally, stimulated the production of MIP-2 and KC, with peak synthesis occurring 48 hours after infection. Dose-response studies showed that exogenous MIP-2 was three to four times more potent than KC in attracting neutrophils as assessed by myeloperoxidase assay and immunohistochemical staining. Subconjunctival administration of neutralizing antibody to MIP-2 resulted in a sharp decrease in neutrophil infiltration and significantly reduced corneal opacity scores. In contrast, in vivo treatment with neutralizing antibody to KC did not suppress ocular inflammation. Additional studies indicated that MIP-2 and KC could be made by corneal epithelial cells and that production was promoted by interleukin (IL)-1. In vivo depletion of neutrophils sharply reduced MIP-2 levels but did not affect KC levels. Collectively, the results suggest that MIP-2 is the major chemokine that attracts neutrophils into the HSV-1 infected cornea, where the cells directly or indirectly cause tissue injury. Resident corneal cells and inflammatory cells contribute to MIP-2 synthesis, whereas KC production seems to be confined largely to corneal cells.