Glycoprotein C of Herpes Simplex Virus Type 1 Is Required to Cause Corneal Disease at Low Infectious Doses In Intact Rabbit Corneas
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Rabbit (cipher)
HSL and HSV
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Clearance
Corneal abrasion
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Herpes simplex virus (HSV) DNA persists in the corneas of patients and animals with a history of herpetic keratitis. The purpose of this study was to detect viral transcripts in the corneas of latently infected rabbits with a history of herpetic keratitis to determine whether the viral DNA represents latent virus, characterized by the restricted transcription of HSV genes and accumulation of the stable latency-associated transcripts (LATs), as occurs in neurons.Rabbits were injected in the subalveolar mucosa with HSV strain RE. After 30 days, corneas were infected by intrastromal injection of HSV. Corneal disease was evaluated, and 7 to 378 days after infection, the rabbits were killed. DNA and RNA were isolated from corneas and trigeminal ganglia and amplified by PCR using gene-specific primers.Herpetic keratitis developed in all rabbits. All corneas of these immune rabbits contained viral DNA as many as 120 days after infection and then the frequency decreased over the next 260 days. Overall, viral DNA was detected in all ganglia and in 57% of corneas. All latently infected ganglia but no corneas contained LATs. Transcripts of the early viral gene for thymidine kinase were detected in 23 of 30 ganglia and 10 of 17 corneas. Transcripts for the late viral glycoprotein C were not detected in either tissue.These data document that after HSV keratitis, viral DNA persists in corneas in the absence of stable LATs and with restricted expression of other viral genes.
Virus latency
Alphaherpesvirinae
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Objective:To determine whether COX-2 inhibitor could block herpes viral reactivation.Methods: We infected the corneas of mice and waited 30 days for Herpes simplex virus type 1 latency to the trigeminal ganglia.Prior to the introduction of viral reactivation,the mice were treated with Xafon.Treated and untreated mice were induced to undergo reactivation by UV-B for 170 mJ/cm~(2).The shedding of the virus was determined by ocular swab cultures and ganglion homogenates with indicator cells. Results :The number of corneas and ganglia containing the infectious virus were significantly lower in the animals treated with Xafon(χ~(2)_(cornea)=22.43,P_(cornea)0.01;χ~(2)_(trigeminal ganglia) =29.16,P_( trigeminal ganglia)0.01),compared to the placebo-treated mice. Conclusion:These experiments demonstrate that a selective COX-2 inhibitor-Xafon can suppress UV-B-induced herpes viral reactivation in cornea and nervous system.
Trigeminal ganglion
Viral Shedding
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To determine whether the herpes simplex virus type 1 (HSV-1) viral glycoprotein C (gC) plays a role in induction of keratitis in unscarified and scarified rabbit eyes.A gC deletion mutant (DeltagC) was constructed and then rescued back to wild type (wt) for use as a control. Following ocular infection with each virus in rabbit eyes, with or without prior corneal scarification, keratitis was compared.At low infection doses of 2 x 10(3) and 2 x 10(4) plaque-forming units (PFU)/eye, in unscarified cornea, DeltagC produced significantly less keratitis than did wt virus (p = 0.007 and 0.03, respectively). In contrast, the keratitis induced by DeltagC was similar to that induced by the wt virus (p > 0.60) in scarified cornea. At high infection dose (2 x 10(5) PFU/eye), keratitis induced by DeltagC was similar in scarified and unscarified cornea, and the severity of disease was similar to that seen in scarified eyes at the low-dose DeltagC infections. Interestingly, although DeltagC induced keratitis with or without corneal scarification at high infection doses, the severity of disease was significantly less than that induced by wt infection. At all infection doses, keratitis induced by wt infection was similar in scarified and unscarified eyes.These results suggest that (1) at low infection doses, in unscarified corneas, gC is required for HSV-1 induced keratitis; (2) corneal scarification prior to infection can circumvent the need for gC at low doses, but (3) at higher doses, gC is required for wild-type levels of keratitis even in scarified cornea.
Scarification
Corneal Diseases
Corneal ulceration
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Herpes stromal keratitis (HSK) results from infection of herpes simplex virus (HSV) in the cornea. Recurrent HSV infection is a leading cause of corneal scarring and visual loss. Although it is generally thought that HSK is the result of an immune response to one or more viral proteins, no viral proteins have been detected in HSK corneas. Thus, the viral proteins involved in HSK, if any, remain undetermined. In contrast, it is reported here that when HSK corneal buttons from latently infected rabbits were fixed using standard procedures, the important immediate-early HSV-1 protein ICP0 was readily detected in the fixative by Western blotting. Similarly, when HSK corneal buttons were soaked in buffer (rather than fixative), ICP0 was readily detected in the soaking buffer. Other HSV-1 proteins were not detected either in the fixative or in the soaking buffer. It is also reported here that ICP0 was consistently detected in virus-free tears from the eyes of rabbits acutely infected with HSV-1. These results suggest that ICP0 rapidly diffuses out of the cornea and may explain why ICP0 was detected in the fixative of HSK corneas and in the soaking buffer of acutely infected corneas.
Fixative
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Herpes simplex virus-1 (HSV-1) causes life-long morbidities in humans. While fever blisters are more common, occasionally the cornea is infected resulting in vision loss. A very intriguing aspect of HSV-1 corneal infection is that the virus spread is normally restricted to only a small fraction of cells on the corneal surface that connect with each other in a dendritic fashion. Here, to develop a comprehensive understanding of the susceptibility of human corneal epithelial (HCE) cells to HSV-1 infection, we infected HCE cells at three different dosages of HSV-1 and measured the outcomes in terms of viral entry, gene and protein expression, viral replication and cytokine induction. In cultured cells, infectivity and cytokine induction were observed even at the minimum viral dosage tested, while a more pronounced dose-restricted infectivity was seen in ex vivo cultures of porcine corneas. Use of fluorescent HSV-1 virions demonstrated a pattern of viral spread ex vivo that mimics clinical findings. We conclude that HCE cell cultures are highly susceptible to infection whereas the cultured corneas demonstrate a higher ability to restrict the infection even in the absence of systemic immune system. The restriction is helped in part by local interferon response and the unique cellular architecture of the cornea.
Infectivity
Ex vivo
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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.
Infiltration (HVAC)
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Acute retinal necrosis
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At 5 to 7 months after corneal inoculation of herpes simplex virus type 1 in mice, explants of ocular tissue yielded virus. Immunoperoxidase study of explants undergoing reactivation revealed herpes simplex virus antigens in retinal tissue. These results indicate that herpes simplex virus can establish and maintain latency in ocular tissue, most probably in the retina.
Immunoperoxidase
Simplexvirus
Alphaherpesvirinae
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