The effect of cellular immune tolerance to HSV-1 antigens on the immunopathology of HSV-1 keratitis.

Previous studies have revealed that herpes simplex virus type 1 (HSV-1) corneal stromal lesions do not develop in the absence of a cell-mediated immune (CMI) response to HSV-1 antigens. HSV-1 glycoprotein C (gC) has been shown to play an important role in the induction of the cytotoxic T lymphocyte (CTL) response to HSV-1 infections at anatomical sites other than the eye. Here we report that a deletion mutant lacking gC (gC-39) when used to infect the corneas of A/J mice was a poor inducer of both CTL and delayed type hypersensitivity (DTH) responses. We have also followed histologically and immunohistochemically the course of HSV-1 stromal disease in A/J mice following topical corneal (TC) infection with wild type (WT) HSV-1, TC infection with gC-39 HSV-1, and simultaneous TC and anterior chamber (TC + AC) infection with WT HSV-1. The latter type of infection has been shown to induce a profound state of DTH and CTL tolerance of HSV-1 antigens. Following TC infection with WT HSV-1, stromal disease progressed to severe ulcerative keratitis with neovascularization by day 21. Histologic and immunohistochemical analysis revealed a predominantly mononuclear infiltrate consisting of numerous plasma cells as well as L3T4+ (T helper/inducer) and Lyt-2+ (T suppressor/cytotoxic) T lymphocytes. Following TC infection with gC-39, or simultaneous TC + AC infection with WT HSV-1, the severity of stromal disease did not progress beyond day 7. On day 21, there was at most a mild stromal cellular infiltrate consisting predominantly of polymorphonuclear neutrophils. These findings indicate that early stromal disease consists of a nonspecific inflammatory response, but severe stromal disease involves a CMI response to HSV-1. AC injection of HSV-1 inhibits the CMI response, thereby halting the progression of stromal disease. Similarly, gC-39, a poor inducer of CMI responses, is also a poor inducer of stromal disease.