IMMUNOLOGICAL, HISTOLOGIC, AND VIROLOGICAL FEATURES OF HERPESVIRUS-INDUCED STROMAL KERATITIS IN CATS

Sequential histologic, immunologic, and virologic features of herpesvi rus-induced keratitis were studied in 18 experimentally infected cats. Histologic changes were assessed by use of light microscopy, and the presence of viral antigen, B lymphocytes, and T lymphocytes was verifi ed immunohistochemically. Flow cytometry was used to monitor changes i n blood T lymphocytes (CD4 and CD8 homologues) and B lymphocytes. Cell ular immunity was assessed by use of the lymphocyte proliferation assa y. Development of stromal keratitis was preceded by prolonged absence of corneal epithelium, decreased numbers of circulating lymphocyte sub sets, decreased mitogen responses, and acquisition of viral antigen by the corneal stroma. Return to normal of circulating lymphocyte number s and function was temporally associated with the arrival of neutrophi ls and B and T lymphocytes in the corneal stroma. Sequelae to stromal inflammation were fibrosis and scarring. Findings suggest that suppres sion of local immune responses allows virus access to the corneal stro ma, and that subsequent keratitis is mediated by an immune response to viral antigen.