Pathogenesis of Herpes Simplex Virus Type 1-Induced Corneal Inflammation in Perforin-Deficient Mice

Abstract

Herpetic stromal keratitis (HSK) is an inflammatory disease of the cornea that often results in blindness.It is mediated by a host immune response which is triggered by herpes simplex virus (HSV) infection. Immune effector mechanisms are hypothesized to be important in disease development. We investigated, in a mouse model, whether perforin-dependent cytotoxicity is an important effector mechanism in the production of HSK. Wild-type (C57BL/6) and perforin-deficient (PKO) mice were infected intracorneally with HSV-1 strain F. Clinical disease and histologic lesions of the cornea at 23 days postinfection (p.i.) were significantly less severe in HSV-1-infected PKO mice than in infected wild-type mice. mRNA for the chemokine macrophage inflammatory protein 1␣ (MIP-1␣) was detected by reverse transcription-PCR in the corneas of infected wild-type mice but not in the corneas of infected PKO mice at 23 days p.i. Adoptive transfer of wild-type HSV-1 immune T-cell-enriched splenocytes into HSV-1-infected PKO mice restored the disease phenotype which was seen in infected wild-type mice. In contrast, mice carrying a null-function mutation in the Fas ligand, which is involved in an alternative cytotoxic mechanism, developed clinical disease and histologic lesions which were comparable to those in wild-type mice. Viral clearance from the eyes of PKO mice was not impaired. There was no significant difference between the infectious viral titers isolated from the eyes of PKO and wild-type mice. Our findings show that perforin is important in the pathogenesis of HSK.Herpetic stromal keratitis (HSK) is a chronic inflammation of the cornea which is a consequence of infection by herpes simplex virus (HSV). It is the main nontraumatic cause of corneal blindness in people in developed countries (54). HSV-1-induced corneal inflammation in the mouse model is an immunopathological condition mediated by T lymphocytes (11, 20-22, 38, 48, 49, 54). T-cell-deficient mice, such as athymic nude mice, scid mice, or thymectomized mice, do not develop keratitis following intracorneal infection with HSV-1. However, these mice develop HSK upon intracorneal HSV-1 infection if they have previously received an adoptive transfer of HSV-1 immune T lymphocytes (3,11,12,21,37,43,58).The main effector mechanisms mediated by T lymphocytes are the secretion of soluble factors such as cytokines and chemokines and the lysis of target cells. Cytokines, such as gamma interferon, have been proposed as mediators of HSK (2,20,24). However, studies of gamma interferon knockout mice failed to demonstrate a role for gamma interferon in the pathogenesis of HSV-induced stromal keratitis (5). Chemokines have also been postulated to be involved in the development of HSK (55, 57, 59). There is evidence that macrophage inflammatory protein 1␣ (MIP-1␣), a beta chemokine involved in lymphocyte recruitment, plays a role in the development of HSK (60).Immune cytotoxic effector mechanisms play a role in the development of many immune-mediated disorders. The two main cytotoxic ef...

Development and Migration of Protective CD8+ T Cells into the Nervous System following Ocular Herpes Simplex Virus-1 Infection

“…CD8 ϩ T cells were implicated as potential mediators of acute viral control in the nervous system and of neuropathogenesis (12,13,15,(17)(18)(19)(20)(21) and also as sentinels that potentially control viral reactivation from latency in the TG in situ (22)(23)(24)(25). Such evidence was obtained using infection of animals treated with depleting Abs (13,15,17) or studies in knockout mice lacking CD8␣ (26,27), IFN-␥ (26, 28 -30), or molecules that mediate cytotoxicity (27,(31)(32)(33)(34). Direct proof that the missing effector molecules act via CD8 T cells, however, was often not obtained in these studies, and the results of some studies questioned an obligatory role of CD8 ϩ T cells in fighting HSV (22,35).…”

The Cornea through the Eyes of Knockout Mice

“…Perforin is a cytolysin expressed on cytotoxic T lymphocytes and natural killer cells. HSV-1 induced corneal in¯ammation and keratitic lesions were less severe in perforin -/-mice indicating a role for perforin in the cytotoxicity of effector cells and subsequent release of cytokines and chemokines that promote in¯ux of in¯ammatory in®ltrates (Chang et al, 2000). Cell adhesion proteins, such as P-selectin and I-CAM, also play a role in the migration and in®ltration of in¯ammatory cells in corneal infections.…”

“…Reduced cytoxicity and in¯ammation in HSV 1 keratitis Chang et al (2000) P-selectin, Selp Impaired eosinophil recruitment during in¯ammation Kai® et al (2000) Intercellular adhesion molecule-1, ICAM-1 Impaired recruitment of in¯ammatory in®ltrates Hobden et al (1999) TNF a receptor I and II, TnfrI (p55), TnfrII (p75) Reduced Langheran cell recruitment into central cornea after trauma Dekaris et al (1999) Neurosensory Tyrosine kinase A (TrkA) Reduced number of sensory epithelial and stromal neurons. Reduced sensitivity to noxious stimuli…”

Neurons Differentially Activate the Herpes Simplex Virus Type 1 Immediate-Early Gene ICP0 and ICP27 Promoters in Transgenic Mice

“…Four mice from each of the eight transgenic lines (two ICP0 lines, three ICP27 lines, and three gC lines) and four nontransgenic control mice were inoculated by the corneal route with 10 7 PFU of HSV-1 strain F per eye (9,38,44). Four mice from each line were mock inoculated by the corneal route of inoculation using medium containing no virus.…”