Herpes Simplex Keratitis as a Complication of Pterygium Surgery

BACKGROUND Infectious keratitis after pterygium surgery is a rare but potentially devastating complication. The present study presents 5 cases of herpes simplex keratitis (HSK) after pterygium surgery. CASE REPORT This study was conducted in our clinic in a 5-year period from February 2017 to September 2021. The 5 patients were men, aged between 42 and 73 years, with no prior history of herpes simplex virus (HSV) infections. Symptoms appeared near 1 month (median 30 days, range 10 to 70 days) after primary pterygium surgery. Diagnosis was based on clinical symptoms and laboratory test results, such as tear HSV-sIgA, corneal tissue polymerase chain reaction, and next-generation sequencing of metagenomics. The epithelial (1/5) and stromal (4/5) subtypes of HSK were identified. The patients received topical ganciclovir gel, immunosuppressive eyedrops, and oral acyclovir tablets, along with additional surgical interventions if necessary. Three were healed with conservative therapy, 1 eye required amniotic membrane transplantation due to corneal melt, and 1 was perforated and followed by corneal grafting. Finally, a literature review of previous publications on HSK after ocular surgeries was conducted. CONCLUSIONS HSK is a rare but serious complication that can arise after uneventful pterygium surgery. It is worthy of attention that both epithelial and stromal forms can occur. Timely diagnosis and treatment are crucial to prevent unfavorable outcomes. Consequently, routine corneal fluorescein staining, tear sIgA examination, and corneal scraping for polymerase chain reaction or next-generation sequencing of metagenomics should be performed in any suspected cases.

New-Onset of Herpes Simplex Keratitis After Blepharoplasty, Case Series and Review of the Literature

PURPOSE

To report 3 cases of new-onset herpes simplex keratitis (HSK) after uncomplicated extraocular plastic surgery and discuss potential risk factors.

METHODS

This case series includes 3 patients who underwent uncomplicated blepharoplastic surgery. Within 2 weeks postoperatively, all patients reported ocular discomfort, and their ophthalmic examinations revealed corneal lesions suspicious of HSK. One case was confirmed as an active herpes infection, and the other 2 cases were clinically diagnosed with HSK. The patients were treated with oral acyclovir and followed up for up to 6 weeks.

RESULTS

All patients demonstrated improvement without sequelae at follow-up visits from 5 days to 4 weeks after initiating acyclovir treatment.

CONCLUSIONS

Risk factors for new-onset HSK after uncomplicated extraocular surgeries may be related to an immunocompromised state, postoperative administration of topical or periocular corticosteroids, or environmental factors such as psychological stress. Ophthalmologists, particularly plastic surgeons, should be vigilant for ocular discomfort following eyelid surgeries and consider the possibility of herpes infection. This report highlights the importance of recognizing and managing HSK in the context of extraocular plastic surgery.

Herpetic Eye Disease Following the SARS-CoV-2 Vaccinations

PURPOSE

To describe herpetic ocular infections following SARS-CoV-2 vaccinations.

METHODS

A retrospective study of herpetic ocular infections after BNT162b2mRNA vaccination and a literature review.

RESULTS

A cohort of five patients: three varicella zoster virus (VZV) and two herpes simplex virus (HSV) cases, as well as 19 literature cases: 9 cases of VZV and 10 cases of HSV post BNT162b2mRNA, AZD1222, mRNA-1273, and CoronaVac vaccinations. All cases presented within 28 days post vaccination. Most VZV and HSV cases (15/19) reported in the literature presented post first vaccine dose, while in our cohort 2 VZV cases presented post second dose and both HSV cases and one VZV case post third dose. The most common presentations were HZO with ocular involvement and HSV keratitis. All eyes had complete resolution; however, one had retinal detachment and three corneal scars.

CONCLUSION

Herpetic ocular infections may develop shortly after SARS-CoV-2 vaccinations. Overall, the outcome is good.

Reactivation of Herpes Simplex Keratitis on a Corneal Graft Following SARS-CoV-2 mRNA Vaccination

Background

Ocular herpes simplex is usually caused by herpes simplex virus type 1 (HSV-1) and less commonly by the type 2 virus (HSV-2). Ocular manifestations of HSV include blepharitis, conjunctivitis, lacrimal system obstruction, corneal involvement, and uveitis. Corneal involvement is one of the causes of loss of vision and can be epithelial herpetic keratitis or stromal herpetic keratitis.

Objective

A significant population has a colonization of herpes viruses. Under certain circumstances, these viruses can reactivate with a significant ocular morbidity. Globally, COVID-19 vaccines are recommended; however, the vaccine safety data are limited.

Case report

Herein, we reported a case of herpetic keratitis reactivation that occurred 2 days after receiving SARS-CoV-2 mRNA vaccine. The patient is a 50-year-old man who underwent penetrating keratoplasty (PKP) in 2020 for corneal opacity caused by a previous herpes simplex keratitis in 2013. Herpetic keratitis was treated successfully with topical antiviral acyclovir along with topical moxifloxacin and artificial tears. After treatment, prophylactic oral acyclovir was started.

Conclusion

Both ophthalmologist and patients should be aware of this phenomenon. Long-term prophylactic antiviral treatment may be recommended for those patients.

Epithelial keratitis mimicking herpes simplex keratitis in a patient after cataract surgery: A case report

RATIONALE

Epithelial keratitis is a common complication after cataract surgery. Many factors have been attributed to this clinical phenomenon.

PATIENT CONCERNS

An 82-year-old woman without previous herpes simplex keratitis (HSK) underwent an uncomplicated clear corneal phacoemulsification procedure in the right eye. In the late postoperative period, epithelial keratitis developed in this same eye.

DIAGNOSIS

An initial diagnosis of HSK was made clinically. The lesion was refractory to antiviral treatment and had progressed. After topical acyclovir cessation and vigorous lubrication, a diagnosis of toxic keratitis was finally made.

OUTCOMES

The corneal epithelial defect and dendritic lesion presented initially. Responding to antiviral treatment, this corneal lesion aggravated and revealed large epithelial erosion. After topical acyclovir cessation and initiation of vigorous lubrication, the toxic keratitis was completely resolved.

LESSONS

Epithelial keratitis following cataract surgery is a common complication and can be misdiagnosed early in its disease course. Physicians should be alert to the possibility of HSK. Polymerase chain reaction detection is helpful in diagnosing this disease.

[Uveitis treated with biotherapy and/or DMARD: Analysis from the French Pharmacovigilance Study Base]

PURPOSE

To report the characteristics of uveitis cases occurring while on biologic therapy or disease-modifying antirheumatic drugs (DMARDs) reported to the French national pharmacovigilance database.

METHODS

All the uveitis cases occurring in patients with chronic rheumatologic diseases, chronic inflammatory intestinal diseases or connective tissue diseases, while treated with DMARDs and/or biologic therapies between 2000 and 2015 and reported to the French National Pharmacovigilance Database were collected.

RESULTS

During the study period, 32 cases of uveitis were reported (15 men, 17 women). Two patients were treated with one DMARD alone, 24 with biologic therapy alone, and six with both treatments. Anterior uveitis was diagnosed in 19 patients (8 cases were bilateral); intermediate uveitis was found (unilaterally) in one patient; posterior and diffuse uveitis occurred in 5 and 2 cases respectively. Five cases were inconclusive with regard to the anatomical type of uveitis. The uveitis was of infectious origin in 5 cases: 2 toxoplasmosis, 2 herpes virus and 1 tuberculosis. In the 27 other cases, it was not possible to state whether the uveitis was associated with the underlying disease (uncontrolled) or a side effect of the biologic/DMARD treatments. The occurrence of the uveitis led to 9 switches in biologic therapy and 13 discontinuations of treatment (8 complete discontinuations, 5 discontinuations only until uveitis remission was obtained). In 4 cases, the treatments were not modified. The database does not specify the ultimate course or rheumatologic disease activity at the time of the uveitis.

CONCLUSIONS

The presence of uveitis while on biologic therapy must not be taken to indicate a therapeutic failure, especially if the ocular manifestation is isolated. In the case of uveitis occurring in patients treated with biologic therapies and/or DMARDs, infectious complications should be ruled out.

Adverse effects of low-dose systemic cyclosporine therapy in high-risk penetrating keratoplasty

PURPOSE

The purpose of this study was to investigate the adverse effects of low-dose oral cyclosporine (CsA) therapy following high-risk corneal transplantation.

METHODS

The medical records from 88 subjects who had undergone high-risk penetrating keratoplasties and had been administered oral CsA were retrospectively analyzed. High risk was defined as a history of graft rejection, three or more quadrants of vascularization, or the presence or history of intraocular inflammation. An initial CsA dose of 3-5 mg/kg per day was given for 3-7 days, followed by 2.5-3.5 mg/kg per day for approximately 1 month. The concentration of CsA was maintained at the target trough level of 120-150 ng/ml for at least 6 months or until serious complications developed. The relationship between the cumulative dose and duration of CsA administration and the adverse systemic effects, including the frequency of herpes keratitis, was evaluated. The incidence of herpes keratitis in the study subjects was compared with the incidence in 185 patients who had not received CsA therapy following penetrating keratoplasty.

RESULTS

The mean survival time of the grafts was 33.6 months. Adverse effects occurred in 81.8 % of subjects. Hypertension, elevated liver enzyme levels, elevated serum creatinine level, and decreased absolute neutrophil count (ANC) were observed in 14.8, 6.8, 5.7, and 5.7 % of subjects, respectively. Simvastatin-induced rhabdomyolysis also developed in one case. Some patients exhibited minor complications, with gastrointestinal problems and hypertrichosis recorded in 5.7 and 3.4 % of subjects, respectively. Hypertension and hepatotoxicity most frequently occurred after 4 to 8 weeks of medication, while ANC decrease and nephrotoxicity generally developed after 24 weeks of treatment, with incidence related to the cumulative dose. Herpes keratitis occurred more frequently (31.8 %) in the CsA-treated subjects than in subjects that did not receive CsA therapy (p = 0.005). Most of the adverse effects were reversed after discontinuation of CsA therapy.

CONCLUSION

The results of this study suggest that low-dose oral CsA therapy may induce various adverse effects, the most common of which are herpes keratitis and hypertension.

Prevention of herpes simplex virus induced stromal keratitis by a glycoprotein B-specific monoclonal antibody

The increasing incidence of acyclovir (ACV) and multidrug-resistant strains in patients with corneal HSV-1 infections leading to Herpetic Stromal Keratitis (HSK) is a major health problem in industrialized countries and often results in blindness. To overcome this obstacle, we have previously developed an HSV-gB-specific monoclonal antibody (mAb 2c) that proved to be highly protective in immunodeficient NOD/SCID-mice towards genital infections. In the present study, we examined the effectivity of mAb 2c in preventing the immunopathological disease HSK in the HSK BALB/c mouse model. Therefore, mice were inoculated with HSV-1 strain KOS on the scarified cornea to induce HSK and subsequently either systemically or topically treated with mAb 2c. Systemic treatment was performed by intravenous administration of mAb 2c 24 h prior to infection (pre-exposure prophylaxis) or 24, 40, and 56 hours after infection (post-exposure immunotherapy). Topical treatment was performed by periodical inoculations (5 times per day) of antibody-containing eye drops as control, starting at 24 h post infection. Systemic antibody treatment markedly reduced viral loads at the site of infection and completely protected mice from developing HSK. The administration of the antiviral antibody prior or post infection was equally effective. Topical treatment had no improving effect on the severity of HSK. In conclusion, our data demonstrate that mAb 2c proved to be an excellent drug for the treatment of corneal HSV-infections and for prevention of HSK and blindness. Moreover, the humanized counterpart (mAb hu2c) was equally effective in protecting mice from HSV-induced HSK when compared to the parental mouse antibody. These results warrant the future development of this antibody as a novel approach for the treatment of corneal HSV-infections in humans.

[Lamellar minikeratoplasty for recurrent herpes keratitis in the late post-LASIK period]

The article presents a case report of sutureless lamellar minikeratoplasty for progressive corneal ulceration associated with herpes simplex infection in the late period after LASIK.

Herpesvirus entry mediator is a serotype specific determinant of pathogenesis in ocular herpes

Infection with herpes simplex virus type 1 (HSV-1) and HSV-2 is initiated by viral glycoprotein D (gD) binding to a receptor on the host cell. Two receptors, herpesvirus entry mediator (HVEM) and nectin-1, mediate entry in murine models of HSV-1 and HSV-2. HVEM is dispensable for HSV-2 infection of the vagina and brain, but is required for WT pathogenesis of HSV-1 infection of the cornea. By challenging WT and HVEM KO mice with multiple strains of HSV-1 and HSV-2, we demonstrate that without HVEM, all HSV-1 strains tested do not replicate well in the cornea and infection does not result in severe symptoms, as observed in WT mice. In contrast, all HSV-2 strains tested had no requirement for HVEM to replicate to WT levels in the cornea and still cause severe disease. These findings imply that HSV-2 does not require HVEM to cause disease regardless of route of entry, but HVEM must be present for HSV-1 to cause full pathogenesis in the eye. These findings uncover a unique role for HVEM in mediating HSV-1 infection in an area innervated by the trigeminal ganglion and may explain why the presence of HVEM can lead to severe inflammation in the cornea. Thus, the dependence on HVEM is a dividing point between HSV-1 and HSV-2 that evolved to infect areas innervated by different sensory ganglia.

Quantifying changes in corneal neovascularization using fluorescein and indocyanine green angiography

PURPOSE

To quantify changes in corneal neovascularization in patients with active keratitis after treatment using color imaging, fluorescein angiography (FA), and indocyanine green angiography (ICGA).

DESIGN

Prospective, interventional case series.

METHODS

Twelve consecutive patients were studied. A comparison of corneal neovascularization parameters was undertaken before and after resolution of the keratitis. A slit-lamp digital camera acquired images of the neovascularization using color imaging, FA, and ICGA. The best-quality images were selected using a grading system, and the neovascular regions of interest were analyzed using automated in-house software. The parameters of analysis were vessel area, diameter, tortuosity, and FA dye leakage.

RESULTS

There was a significant reduction in the area of neovascularization after treatment on color imaging (0.78 mm(2); P < .05), FA (2.33 mm(2); P < .01), and ICGA (2.07 mm(2); P < .01). There was also a significant reduction in mean vessel diameter across the region of interest for each patient, more marked on FA (42.74 to 32.52 μm; P < .01) and ICGA (44.77 to 33.29 μm; P < .01) than on color imaging (29.10 to 25.17 μm; P < .01). A significant change in vessel tortuosity was not observed. There was a significant increase in FA dye leakage time (12.41 seconds; P < .05) after treatment.

CONCLUSIONS

We demonstrate application of an objective method for analyzing changes in corneal neovascularization. The excellent vessel delineation with ICGA even in the presence of stromal scars makes it an ideal agent for measurement of vessel parameters. FA is useful at detecting vessel leakage, and the time to leakage provides a possible measure of vessel staging.

Unusual clinical presentations of new-onset herpetic eye disease after ocular surgery

PURPOSE

To report five cases of new-onset herpetic eye disease with unusual presentation after ocular surgery.

METHODS

Herpetic eye disease was suspected in five cases, three after cataract surgery and two after lamellar corneal transplantation surgery. Of these, four cases presented within 2-6 weeks of surgery. The clinical presentation was in the form of an epithelial defect, suspected epithelial down growth, graft oedema with unexplained anterior chamber inflammation and graft-host interface infection. A swab for viral detection with real-time polymerase chain reaction was performed in all the described cases.

RESULTS

Herpes simplex disease was detected in all cases. All cases responded to the antiherpetic medications.

CONCLUSIONS

Our study shows that new-onset herpetic eye disease may occur after cataract surgery and lamellar corneal transplantation, and a high index of suspicion may be necessary for the diagnosis in such cases.

Human herpes simplex virus keratitis: the pathogenesis revisited

Infections with several members of the human herpesviruses are the cause of significant ocular morbidity. Of the human herpesviruses, HSV-1 is the most frequent cause of primary and recurrent eye disease. Despite the availability of effective antiviral treatment, recurrent HSV-1 infection continues to be the leading cause of corneal blindness in industrialized nations. This review recapitulates the current insights in the role of the virus and the intra-corneal T cell response involved in the pathogenesis of human HSV-1-induced keratitis.

Glycoprotein C of herpes simplex virus type 1 is required to cause keratitis at low infectious doses in intact rabbit corneas

PURPOSE

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.

MATERIALS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Susceptibility of Human Corneal Endothelial Cells to HSV-1 Infection

PURPOSE

The purpose of this study was to examine the intrinsic susceptibility of cultured human corneal endothelial cells (HCEC) to herpes simplex virus-1 (HSV-1) infection. We compared HSV-1 adsorption, kinetics of HSV-1 production, and pattern of viral plaque formation in cultured HCEC with those of a cell line used routinely for laboratory HSV propagation (African green monkey kidney fibroblast CV-1 cells).

METHODS

Cultured HCEC and CV-1 cells were exposed to the McKrae strain of HSV-1 at 5 and 0.0001 multiplicities of infection (MOI). Using the 50% tissue culture infectious dose (TCID(50)) titration method, viral adsorption (at 5 MOI) and total virus production (at 5 and 0.0001 MOI) were compared to assess both susceptibility to viral attachment and productive viral infection, respectively. Additionally, visual observations were made at 0.0001 MOI using bright-field microscopy and immunofluorescence staining of viral antigens to compare patterns of viral spread in confluent monolayers of both cell types.

RESULTS

The percentage of HSV-1 virion particles adsorbed by cultured HCEC and CV-1 cells was similar (35.9% and 33.0%, respectively, p = 0.07, NS), indicating similar susceptibility of the two cell types to initial HSV-1 attachment and adsorption. However, maximum total virus production was more than 3-fold higher for HCEC than for CV-1 cells (p < 0.005), suggesting higher susceptibility of HCEC cells to productive viral infection. Immunofluorescence studies of infected cell monolayers corroborated these quantitative findings, with HCEC monolayers demonstrating more rapid progression of cytopathic effect than CV-1 monolayers.

CONCLUSIONS

In comparison to reference CV-1 cells, cultured HCEC show similar susceptibility to HSV-1 adsorption, but higher capacity to support productive HSV-1 infection. Our results suggest that human corneal endothelial cells may be inherently susceptible to HSV-1 infection.

Primary herpes virus keratitis after penetrating keratoplasty

We present a case of a newly acquired herpetic infection in the graft after penetrating keratoplasty.

[The clinical features of piarenchymatous keratitis depending on its etiology]

Social, pharmacological, and environmental alterations were responsible for a change in the classical clinical picture of many long-forgotten diseases. The authors comparatively analyzed the clinical picture of parenchymatous keratitis of varying genesis in 16 patients (20 cases) with this condition. The distinguishing characteristics of keratitis were noted in herpes, tuberculosis, syphilis, sarcoidosis, the knowledge of which allows ophthalmologists to make an etiological diagnosis in earlier periods.

A Case of Herpetic Keratitis After Intravitreal Triamcinolone Injection

PURPOSE

We report a case of herpetic epithelial keratitis that developed after intravitreal triamcinolone acetonide injection.

METHODS

An 81-year-old man with diabetes with severe nonproliferative diabetic retinopathy and diffuse macular edema in both eyes received bilateral intravitreal injections of 0.4 mg/0.1 mL of triamcinolone acetonide.

RESULTS

Eighteen days after the injections, the patient presented with redness, tearing, foreign body sensation, and decreased visual acuity in the right eye. The cornea showed dendriform ulcers that exhibited positive fluorescein staining. Diagnosis for herpes simplex epithelial keratitis was made, and topical acyclovir ointment therapy was initiated. The epithelial lesions healed after 7 days of therapy.

CONCLUSIONS

Herpes simplex epithelial keratitis can be a possible complication of intravitreal triamcinolone acetonide injection. The course and response to conventional therapy was no different from that of the classical course of the disease.

Herpes Simplex Keratitis After Intravitreal Triamcinolone Acetonide

PURPOSE

To report a case of recurrent herpes simplex virus (HSV) epithelial keratitis after intravitreal triamcinolone acetonide injection for the treatment of diabetic macular edema.

METHODS

Case report.

RESULTS

We describe a case of a 59-year-old woman with a history of ocular HSV disease and severe proliferative diabetic retinopathy. She received an intravitreal injection of triamcinolone acetonide for macular edema in the right eye. One week later, she developed foreign body sensation, redness, and photophobia in the same eye. Slit-lamp examination revealed a corneal epithelial dendritic lesion. She was diagnosed with a recurrence of HSV epithelial keratitis and was treated with oral acyclovir 400 mg, 5 times a day, with good resolution of HSV signs and symptoms.

CONCLUSIONS

Intravitreal triamcinolone acetonide injection may result in reactivation of HSV keratitis.

Progressive Herpetic Linear Endotheliitis

PURPOSE

To report the clinical course of a rare case of bilateral herpetic linear endotheliitis.

METHODS

A 70-year-old man presented with bilateral circumferential bullous edema with stromal edema progressing centrally in the left cornea and bilateral sensorineural hearing impairment simultaneously. Serum immunoglobulin G (IgG) and IgM antibodies against herpes simplex virus type 1 (HSV1) were tested for, and aqueous humor from both eyes was examined separately using polymerase chain reaction for the presence of HSV1 DNA.

RESULTS

Serum antibody titers against HSV1 were positive. In the polymerase chain reaction, the aqueous humor showed HSV1 DNA in both eyes. Forty milligrams of prednisolone was given per day and 200 mg of oral acyclovir was given 4 times daily, but corneal edema progressed. After penetrating keratoplasty surgery in the left eye, recurrent herpetic endotheliitis also seemed to occur.

CONCLUSIONS

HSV-1 may cause bilateral corneal linear endotheliitis and hearing impairment simultaneously. Linear endotheliitis should be regarded as a manifestation of HSV1 corneal infection. There is a poor prognosis, and severe corneal edema can result if aggressive treatment is not used.

Atopic disease and herpes simplex eye disease: a population-based case-control study

PURPOSE

To determine whether atopy is associated with herpes simplex virus (HSV) ocular disease.

DESIGN

Retrospective, population-based, case-control study.

METHODS

SETTING

Large, regional health maintenance organization (Northern California Kaiser Permanente).

STUDY POPULATION

1,042,351 people over a one-year period.

OBSERVATION PROCEDURES

Electronic database search for HSV ocular disease and subsequent chart review determined study eligibility. Two age-matched control groups (one population-based and one clinic-based) were randomly chosen. Medical record review determined the presence of atopy. Severe atopic disease was defined by diagnostic code or illness requiring an emergency room visit, hospitalization, or treatment with a systemic corticosteroid.

MAIN OUTCOME MEASURES

Presence of HSV eye disease, presence of atopy, and characterization of atopy severity.

RESULTS

HSV eye disease was found in 172 patients. HSV cases had a greater prevalence of atopy (34%, 58/172) than the clinic-based (25%, 43/172) or the population-based controls (21%, 36/172, odds ratio (OR) 1.5, 95% confidence interval (CI) 0.9 to 2.6 and OR 1.9, 95%, CI 1.1 to 3.3, respectively). The association of HSV ocular disease with severe atopy was even greater, with a history of severe atopic disease in 13% (22/172) of patients with HSV ocular disease as compared with 6% (11/172) of patients in the clinic control group and 3% (5/172) of patients in the population control group (OR 2.0, 95% CI 0.7 to 5.9 and OR 4.8, 95% CI 1.6 to 19.2, respectively).

CONCLUSIONS

Patients with HSV ocular disease are more likely to have a history of atopic disease, especially severe atopic disease, than age-matched controls.

Increased risk for herpetic eye disease in patients with allergic conjunctivitis

PURPOSE

To evaluate the risk of ocular surface herpetic eye disease (osHED) in allergic eye disease.

METHODS

We calculated the risk for osHED in 11,205 patients on antiallergic ocular topical agents compared with 453,069 controls based on filled prescriptions for topical acyclovir between 2001 and 2003.

RESULTS

Significantly more allergic patients, of all age groups, received treatment for osHED (p < 0.01). The age and gender adjusted relative risk for allergic patients to suffer an osHED event was 2.31 (95% CI: 1.84-2.90), raising to 3.55 (95% CI: 2.0-6.4) in patients that filled > or = 4 antiallergic prescriptions.

CONCLUSIONS

Patients treated for allergic eye disease have an increased risk of osHED.

Histology of Posterior Lamellar Keratoplasty

PURPOSE

To report histology of a posterior lamellar graft performed to treat clinically significant endothelial disease in a patient with Fuchs dystrophy.

METHODS

A 78-year-old patient with Fuchs dystrophy underwent posterior lamellar keratoplasty (PLK), the original form of endothelial keratoplasty performed with manual lamellar dissection of the recipient and donor corneas. Eighteen months later, the patient had herpes simplex virus keratitis and graft rejection episodes. One year after the infection resolved (2.5 years after PLK), penetrating keratoplasty was performed, and the excised corneal button was examined.

RESULTS

Histopathologic evaluation of the corneal button showed no discernible interface, opacity, or gapping between the anterior host stromal tissue and PLK donor tissue or any signs of significant migration of donor endothelial cells onto recipient tissue.

CONCLUSION

This PLK histology showed firm attachment with no visible interface between the posterior donor and anterior host stromal tissue. Surprisingly, no significant donor endothelial cell migration was detected on adjacent recipient tissue where Descemet membrane had been excised or where endothelial cells were lost as a result of the procedure.

Presumed herpetic endotheliitis following phacoemulsification surgery*

The authors present an observational case series. Three cases of presumed herpetic endotheliitis presented as cases of pseudophakic bullous keratopathy many years after successful phacoemulsification surgery. All patients had reduction of vision in the involved eye, corneal oedema and secondary glaucoma. The patients were treated with medical therapy consisting of topical corticosteroids, antiviral and antiglaucoma drugs. Resolution of corneal oedema, control of glaucoma and restoration of visual acuity were achieved in all cases. Specular microscopy performed thereafter demonstrated relatively normal endothelial cell counts. The authors conclude that pseudophakic bullous keratopathy occurring after phacoemulsification surgery may be caused by herpetic endotheliitis.

Herpes Simplex Keratitis Following Excimer Laser Application

PURPOSE

To report two cases of herpes simplex keratitis following excimer laser application.

METHODS

Two immunocompetent patients with no history of ocular viral infection developed ulcers after LASIK and phototherapeutic keratectomy (PTK), respectively.

RESULTS

Antiviral treatment was administered, and the lesions healed within 14 days.

CONCLUSIONS

These two cases suggest that herpes simplex virus was associated with the use of the excimer laser.

Role of inflammatory cytokine-induced cyclooxygenase 2 in the ocular immunopathologic disease herpetic stromal keratitis

Ocular infection with herpes simplex virus (HSV) results in a blinding immunoinflammatory stromal keratitis (SK) lesion. Early preclinical events include polymorphonuclear neutrophil (PMN) infiltration and neovascularization in the corneal stroma. We demonstrate here that HSV infection of the cornea results in the upregulation of the cyclooxygenase 2 (COX-2) enzyme. Early after infection, COX-2 was produced from uninfected stromal fibroblasts as an indirect effect of virus infection. Subsequently, COX-2 may also be produced from other inflammatory cells that infiltrate the cornea. The induction of COX-2 is a critical event, since inhibition of COX-2 with a selective inhibitor was shown to reduce corneal angiogenesis and SK severity. The administration of a COX-2 inhibitor resulted in compromised PMN infiltration into the cornea, as well as diminished corneal vascular endothelial growth factor levels, likely accounting for the reduced angiogenic response. COX-2 stimulation by HSV infection represents a critical early event accessible for therapy and the control of SK severity.

Herpes Simplex Virus Keratitis After Laser in situ Keratomileusis

PURPOSE

To report two cases of herpes simplex virus (HSV) keratitis after laser in situ keratomileusis (LASIK).

METHODS

Interventional small case series. Two patients underwent uneventful LASIK. History of herpes labialis in one patient and herpetic eye disease > 10 years prior to intervention in the other patient was reported. Both patients developed stromal herpetic keratitis 6 weeks and 2 years after the procedure, respectively.

RESULTS

Treatment consisting of topical steroid drops and topical and systemic antiviral therapy was administered. Recurrences of the herpetic keratitis were seen after tapering of the topical steroids; four and three recurrences were observed, respectively. Final visual acuity was > 6/9 in both cases.

CONCLUSIONS

Herpetic keratitis after LASIK is an uncommon, possibly under-reported, entity. Even patients without history of herpetic eye disease can present with this complication. Oral antiviral prophylaxis may be appropriate when performing LASIK on patients with a history of ocular or systemic HSV infection.

Mikrobielle Keratitis nach Laser-in-situ-Keratomileusis

Laser in situ keratomileusis (LASIK) is an effective option and currently one of the most commonly applied surgical techniques in the correction of refractive errors such as myopia, hyperopia, and astigmatism. In contrast to photorefractive keratectomy, it maintains the integrity of Bowman's membrane and the epithelium leading to faster visual rehabilitation as well as less pain and discomfort. Nevertheless, following LASIK the stroma is exposed to infectious organisms. Sight-threatening complications after LASIK are reported to be as rare as 1 in 1000 procedures. However, any infectious keratitis remains potentially devastating. Reports about infectious keratitis following LASIK have increasingly surfaced in recent years. We present a review of the literature on microbial keratitis and present our own cases and recommendations for possible prophylaxis and therapy.

Herpesvirus infection of ICAM-1-deficient mice

PURPOSE

To determine the effect of ICAM-1 deficiency on viral infection of the cornea.

MATERIALS AND METHODS

Wild-type and intercellular adhesion molecule 1 (ICAM-1)-deficient mice were infected with the RE strain of herpes simplex virus type 1 (HSV-1). Corneal swabs and trigeminal ganglia were obtained and analyzed for infectious virus. Corneas and trigeminal ganglia were evaluated for signs of inflammation by immunohistochemical staining and for interferon-gamma (IFN-gamma)-producing cells by enzyme-linked immunospot assay (ELISPOT). Serum anti-HSV-1 antibody titers were determined by enzyme-linked immunosorbent assay (ELISA).

RESULTS

Viral titers in corneal swabs from the wild-type and ICAM-1-deficient mice were not significantly different during the 21-day study. Infectious virus was present in the trigeminal ganglia of wild-type and ICAM-1-deficient mice through day 6 after infection. Serum anti-HSV-1 antibody titers were significantly higher in wild-type mice 6 days after infection, compared with ICAM-1-deficient mice; by day 8 and thereafter, however, antibody titers were not significantly different. Production of interferon gamma was greater in trigeminal ganglion cells from wild-type mice stimulated with interleukin 12 and interleukin 18 on days 4, 6, and 8 after infection compared with cells from ICAM-1-deficient mice. Histopathologic analysis of corneal and ganglion sections from wild-type and ICAM-1-deficient mice showed no significant differences in the time-course of appearance or the intensity of the inflammatory infiltrate. Immunohistochemical staining for CD3(+) T-lymphocytes and CD11b(+) neutrophils and macrophages demonstrated equivalent numbers of these cells in the corneas and trigeminal ganglia of wild-type and ICAM-1-deficient mice.

CONCLUSIONS

The results of these experiments indicate that ICAM-1 deficiency has only a modest effect on viral infection of the cornea and the development of an acquired immune response.

Excimer Laser Photokeratectomy Reactivates Latent Herpes Simplex Virus

BACKGROUND

It has been reported that excimer laser irradiation might elicit herpes simplex virus (HSV) genome activation. We describe a clinical case in which HSV DNA sequences were detected quantitatively after phototherapeutic keratectomy (PTK).

CASE

A 90-year-old woman underwent excimer laser photokeratectomy for bilateral band-shaped keratopathy. Tear film was collected from both eyes using a Schirmer's strip before and 3 and 7 days after phototherapeutic keratectomy.

OBSERVATIONS

HSV-DNA was quantified by a real-time polymerase chain reaction assay. HSV-DNA was detected only on the third day postoperatively in both eyes. The amount of viral DNA was 2.0 x 10(5) (OD) and 1.3 x 10(5) (OS) copies/sample, respectively.

CONCLUSIONS

Excimer laser photokeratectomy stimulated viral shedding in the tear film. Ophthalmologists should be aware that laser irradiation can reactivate latent HSV.

Re-evaluating natural resistance to herpes simplex virus type 1

It is often stated that individuals of a species can differ significantly in their innate resistance to infection with herpes simplex virus type 1 (HSV-1). Three decades ago Lopez reported that C57BL/6 mice could survive a 5,000-fold-higher inoculum of HSV-1 given intraperitoneally than mice of the A or BALB/c strain (Nature 258:152-153, 1975). Susceptible strains of mice died of encephalitis-like symptoms, suggesting that viral spread to the central nervous system was the cause of death. Although Lopez's study documented that C57BL/6 mice were resistant to the development of HSV-1 encephalitis and mortality, the resistance of C57BL/6 mice to other steps of the HSV-1 infection process was not assessed. The results of the present study extend these observations to clarify the difference between resistance to (i) HSV-1 pathogenesis, (ii) HSV-1 replication, (iii) HSV-1 spread, and (iv) the establishment of latent HSV-1 infection. Although C57BL/6 mice are more resistant to HSV-1 pathogenesis than BALB/c mice, the results of the present study establish that HSV-1 enters, replicates, spreads, and establishes latent infections with virtually identical efficiencies in C57BL/6 and BALB/c mice. These observations raise questions about the validity of the inference that differences in natural resistance are relevant in explaining what differentiates humans with recurrent herpetic disease from the vast majority of asymptomatic carriers of HSV-1 and HSV-2.

Recurrent Herpetic Keratouveitis Following YAG Laser Peripheral Iridotomy

OBJECTIVE

To report recurrent herpetic keratouveitis following YAG laser peripheral iridotomy.

METHODS

Case report.

RESULTS

A 64-year-old woman with a history of dendritic keratitis underwent Nd:YAG laser peripheral iridotomy and developed geographic epithelial keratitis with stromal keratouveitis. Culture of a corneal swab grew herpes simplex virus type I. Keratouveitis subsided with acyclovir and corticosteroid therapy.

CONCLUSIONS

Recurrent herpetic keratouveitis may be induced by YAG laser iridotomy.

[Herpes simplex keratitis following laser in situ keratomileusis]

CASE REPORT

A 40-year-old woman underwent bilateral Laser In Situ Keratomileusis (LASIK) for the correction of myopia and astigmatism. The day after, four dendritic ulcers appeared in her left eye. She was treated with topical antiviral agents until complete recovery. She had a history of recurrent labial herpetic infection.

DISCUSSION

Reactivation of herpes simplex virus type 1 can occur, even without any previous history of corneal infection. Although this does not contraindicate surgery, all patients with a history of herpetic infection should be made aware of the complications related to this technique.

Pathogenesis and management of herpes simplex virus keratitis

Herpes simplex keratitis (HSK) remains a common cause of unilateral corneal disease. Despite intense research over three decades, the mainstay of therapy continues to be topical and, more recently, systemic acyclovir plus topical corticosteroid in some cases. There is increasing recognition that HSK after keratoplasty can occur not only as a result of recurrence in patients with HSK, but also in patients with other primary diagnoses as a result of activation of HSV in the host, or by transmission of virus in the donor tissue.

[Herpes simplex keratitis after ophthalmic surgery]

PURPOSE

We report 6 cases of herpes simplex keratitis after ophthalmic surgery, in eyes without clinical history of herpes simplex keratitis.

CASES

These cases comprised 6 patients examined at our hospital between April 1992 and November 2001. Past operations were keratoplasty in 5 eyes and cataract surgery in 1 eye. Clinical findings and predisposing factors were evaluated retrospectively. The period between herpetic epithelial keratitis onset and ophthalmic surgery ranged from 1.5 to 79 months. Predisposing factors included corticosteroid therapy and operative wound. The herpetic epithelial lesions were dendritic ulcers in 2 eyes, geographic ulcer in 1 eye, and atypical epithelial lesions in 3 eyes; in all cases, herpes simplex virus (HSV)-DNA was detected by polymerase chain reaction (PCR) in tear fluid. All herpetic epithelial lesions healed with oral and topical acyclovir.

CONCLUSIONS

When corticosteroids are used following ophthalmic surgery, physicians should be alert to the possibility of herpetic epithelial keratitis, even in patients with no clinical history of herpes simplex keratitis. PCR detection in tear fluid is helpful in diagnosing this disease.

The effects of Xalatan on the recovery of ocular herpes simplex virus type 1 (HSV-1) in the induced reactivation and spontaneous shedding rabbit models

PURPOSE

Xalatan treatment has been reported both clinically and experimentally to promote recurrences of herpetic keratitis. Our goal was to determine the effects of topical Xalatan and its components on the recovery of ocular herpes simplex virus type 1 (HSV-1) in the Induced Reactivation (IR) and Spontaneous Shedding (SS) HSV-1/NZW rabbit latency models using virological outcome measures.

METHODS

HSV-1 latently-infected rabbits in both the IR and SS studies were divided into different topical treatment groups to evaluate commercial Xalatan, its preservatives, and vehicle against appropriate negative and positive controls. In the IR Studies, 91 rabbits received intra-stromal injections of water in both eyes to promote ocular shedding of latent HSV-1. All eyes were then treated and cultured for 10 days. In the SS Studies, 65 rabbits were treated and cultured in both eyes for 30 days.

RESULTS

Dexamethasone, a positive control, promoted extensive ocular shedding of HSV-1 in both the IR and SS Models. In general, neither Xalatan nor its components demonstrated any adverse effects, but some experimental variation was noted. All groups demonstrated comparable recovery of latent HSV-1 from respective trigeminal ganglia.

CONCLUSIONS

Our experimental studies support the world wide clinical epidemiological experience that commercial Xalatan does not appear to promote HSV-1 ocular shedding.

Reactivation and donor-host transmission of herpes simplex virus after corneal transplantation

PURPOSE

To review our previous studies regarding herpes simplex virus type 1 (HSV-1) corneal latency in the rabbit lamellar keratoplasty (LK) and penetrating keratoplasty (PKP) models.

METHODS

Rabbits latently infected with HSV- I received allografts from naive rabbits, and naive rabbits received grafts from rabbits latently infected with HSV-1. In rabbits undergoing LK, viral shedding in tear film and the occurrence of herpetic lesions were investigated for 7 days after operation. In rabbits undergoing PKP, latency-associated transcript (LAT)-positive and -negative HSV- I mutants were used to establish latency. Ninety days after PKP, reactivation of HSV-1 was induced by transcorneal iontophoresis of epinephrine. Viral shedding was then assessed by tear-film swabbing. Donor corneal buttons, recipient corneal rims, and corresponding trigeminal ganglia were analyzed for HSV DNA concentration and viral transcription.

RESULTS

In rabbits undergoing LK, the occurrence of positive tear-film cultures and number of days on which corneal epithelial lesions were observed were significantly higher in the operated eyes of latently infected rabbits as compared with controls. In rabbits undergoing PKP, HSV- I could transmit between host and donor tissues both in anterograde and retrograde fashion. LAT-positive virus had a significantly greater ability to transmit. Higher concentrations of HSV DNA detected in cornea and trigeminal ganglia correlated with active viral transcription and higher percentage of viral shedding.

CONCLUSION

Corneas from latently infected rabbits contain HSV-1 DNA that can replicate and transmit after induced reactivation. Our studies provide further evidence for corneal latency of this virus.

A novel herpes simplex virus type 1 transcript (AL-RNA) antisense to the 5' end of the latency-associated transcript produces a protein in infected rabbits

Following primary ocular infection, herpes simplex virus type 1 (HSV-1) establishes a lifelong latent infection in sensory neurons of the trigeminal ganglia. Latency-associated transcript (LAT), the only known viral gene abundantly transcribed during HSV-1 neuronal latency, is required for high levels of reactivation. Recently we showed that three different mutants that do not alter the LAT promoter but contain deletions within the 5' end of the primary LAT transcript affect viral virulence (G. C. Perng et al., J. Virol. 75:9018-9028, 2001). In contrast, in LAT-null mutants viral virulence appears unaltered (T. M. Block et al., Virology 192:618-630, 1993; D. C. Bloom et al., J. Virol. 68:1283-1292, 1994; J. M. Hill et al., Virology 174:117-125, 1990; G. C. Perng et al., J. Virol. 68:8045-8055, 1994; F. Sedarati, K. M. Izumi, E. K. Wagner, and J. G. Stevens, J. Virol. 63:4455-4458, 1989). We therefore hypothesized that the 5' end of LAT and/or an as yet unidentified gene that overlaps part of this region is involved in viral virulence. We report here on the discovery and initial characterization of a novel HSV-1 RNA consistent with such a putative gene. The novel RNA was antisense to the 5' end of LAT and was designated AL-RNA (anti-LAT sense RNA). The AL-RNA overlapped the core LAT promoter and the first 158 nucleotides of the 5' end of the primary LAT transcript. AL-RNA was detected in extracts from neuron-like cells (PC-12) infected with wild-type HSV-1 but not in cells infected with a mutant with the AL region deleted. The deletions in each of the above three mutants with altered virulence encompass the 5' end of the AL-RNA, and these mutants cannot transcribe AL. This supports the hypothesis that the AL gene may play a role in viral virulence. Based on comparison to the corresponding genomic sequence, the AL-RNA did not appear to be spliced. The AL-RNA was polyadenylated and contained an open reading frame capable of encoding a protein 56 amino acids in length with a predicted molecular mass of 6.8 kDa. Sera from three of three rabbits infected with wild-type HSV-1 but not sera from any of three rabbits infected with a mutant with the AL-RNA region deleted recognized the Escherichia coli recombinantly expressed AL open reading frame on Western blots. In addition, four of six rabbits infected with wild-type virus developed enzyme-linked immunosorbent assay titers against one or more AL synthetic peptides. These results suggest that an AL protein is produced in vivo.

Spontaneous molecular reactivation of herpes simplex virus type 1 latency in mice

Infection of the mouse trigeminal ganglia (TG) is the most commonly used model for the study of herpes simplex virus type 1 (HSV-1) latency. Its popularity is caused, at least in part, by the perception that latent infection can be studied in this system in the absence of spontaneous viral reactivation. However, this perception has never been rigorously tested. To carefully study this issue, the eyes of Swiss-Webster mice were inoculated with HSV-1 (KOS), and 37-47 days later the TG were dissected, serial-sectioned, and probed for HSV-1 ICP4, thymidine kinase, glycoprotein C, and latency-associated transcript RNA by in situ hybridization. Serial sections of additional latently infected TG were probed with HSV-1-specific polyclonal antisera. Analysis of thousands of probed sections revealed abundant expression of viral transcripts, viral protein, and viral DNA replication in about 1 neuron per 10 TG tested. These same neurons were surrounded by a focal white cell infiltrate, indicating the presence of an antigenic stimulus. We conclude that productive cycle viral genes are abundantly expressed in rare neurons of latently infected murine TG and that these events are promptly recognized by an active local immune response. In the absence of detectable infectious virus in these ganglia, we propose the term "spontaneous molecular reactivation" to describe this ongoing process.

Bystander activation involving T lymphocytes in herpetic stromal keratitis

Herpes simplex virus infection of mouse corneas can lead to the development of an immunopathological lesion, termed herpetic stromal keratitis (HSK). Such lesions also occur in TCR-transgenic mice backcrossed to SCID (TgSCID) that are unable to mount detectable HSV-specific immune responses. The present study demonstrates that lesion expression in such mice depends on continuous viral replication, whereas in immunocompetent mice, lesions occurred even if virus replication was terminated at 4 days after infection. The continuous replication in TgSCID mice was considered necessary to produce an activating stimulus to CD4(+) T cells that invade the cornea. Lesions in TgSCID were resistant to control by cyclosporin A, but were inhibited by treatment with rapamycin. This result was interpreted to indicate that T cell activation involved a non-TCR-mediated cytokine-driven bystander mechanism. Bystander activation was also shown to play a role in HSK lesions in immunocompetent mice. Accordingly, in immunocompetent DO11.10 mice, lesions were dominated by KJ1.26(+) OVA-specific CD4(+) T cells that were unreactive with HSV. In addition, KJ1.26(+) HSV nonimmune cells parked in ocularly infected BALB/c mice were demonstrable in HSK lesions. These results provide insight for the choice of new strategies to manage HSK, an important cause of human blindness.

Keratitis

Corneal inflammation or keratitis is a significant cause of ocular morbidity around the world. Fortunately, the majority of the cases are successfully managed with medical therapy, but the failure of therapy does occur, leading to devastating consequences of either losing the vision or the eye. This review attempts to provide current information on most, though not all, aspects of keratitis. Corneal inflammation may be ulcerative or nonulcerative and may arise because of infectious or noninfectious causes. The nonulcerative corneal inflammation may be confined to the epithelial layer or to the stroma of the cornea or may affect both. For clarity, this section has been divided into nonulcerative superficial keratitis and nonulcerative stromal keratitis. While the former usually includes hypersensitivity responses to microbial toxins and unknown agents, the latter can be either infectious or noninfectious. In the pathogenesis of ulcerative keratitis, microorganisms such as bacteria, fungi, parasites (Acanthamoeba), or viruses play an important role. Approximately, 12.2% of all corneal transplantations are done for active infectious keratitis. Available world literature pertaining to the incidence of microbial keratitis has been provided special place in this review. On the other hand, noninfectious ulcerative keratitis can be related to a variety of systemic or local causes, predominantly of autoimmune origin.

Recurrent ocular herpes simplex keratitis following excimer laser photorefractive keratectomy in a rabbit model

PURPOSE

Reactivation of latent herpes simplex virus (HSV) by excimer laser photorefractive keratectomy(PRK) has been reported previously in the literature. This study evaluates the extent of such HSV reactivation and determines whether corneal de-epithelialization prior to PRK or the laser treatment itself induces this response.

METHODS

Twenty three normal 1.5-2.5 kg New Zealand white rabbits were infected on the surface of the cornea with HSV-1, strain RE. The animals were monitored until resolution and then divided into two treatment groups: 1) de-epithelialization alone, and 2) de-epithelialization plus laser. Animals were evaluated in a masked fashion by clinical examination and viral cultures twice a week through day 28.

RESULTS

The reactivation rate for group 1 (de-epithelization alone) was 0.0%, and for group 2 (PRK) was 67% by slit lamp biomicroscopy. Viral culture positivity rate matched these findings.

CONCLUSIONS

Excimer laser (193 nm) treatment can trigger viral shedding and reactivation of herpetic ocular disease in the latently infected rabbit. De-epithelialization alone is not sufficient to cause such viral reactivation or keratitis. Our findings suggest that patients with a history of herpetic keratitis undergoing PRK are at increased risk of HSV reactivation as a result of exposure to the excimer laser.

Experimental laser-assisted in situ keratomileusis induces the reactivation of latent herpes simplex virus

PURPOSE

We determined whether laser-assisted in situ keratomileusis acts as a trigger for the reactivation and ocular shedding of herpes simplex virus type-1 in a rabbit latency model.

METHODS

Herpes simplex virus type-1 latently infected rabbits were divided into three treatment groups: Group I received surface excimer laser ablation in both eyes (positive control), Group II received laser-assisted in situ keratomileusis in both eyes, and Group III received no treatment (negative control). Eyes were cultured daily for 10 days to determine herpes simplex virus type-1 reactivation.

RESULTS

The number of herpes simplex virus type-1 positive eye cultures and total herpes simplex virus type-1 shedding days were significantly greater after surface excimer laser ablation and laser-assisted in situ keratomileusis compared with the untreated control group (P < 0.002 and P < 0.000001, respectively).

CONCLUSION

Laser-assisted in situ keratomileusis as well as surface excimer laser ablation act as a trigger for the reactivation of herpes simplex virus type-1 in the rabbit latency model.

Herpes simplex virus-induced keratitis: evaluation of the role of molecular mimicry in lesion pathogenesis

Viruses are suspected but usually unproven triggering factors in autoimmunity. One favored mechanism to explain the role of viruses in the genesis of autoimmunity is molecular mimicry. An immunoinflammatory blinding lesion called herpetic stromal keratitis (HSK) that follows ocular infection with herpes simplex virus (HSV) is suggested to result from a CD4(+) T-cell response to a UL6 peptide of HSV that cross-reacts with a corneal autopeptide shared with the immunoglobulin G2a(b) (IgG2a(b)) isotype. The present report reevaluates the molecular mimicry hypothesis to explain HSK pathogenesis. Our results failed to reveal cross-reactivity between the UL6 and IgG2a(b) peptides or between peptide reactive T cells and HSV antigens. More importantly, animals infected with HSV failed to develop responses that reacted with either peptide, and infection with a recombinant vaccinia UL6 vector failed to cause HSK, in spite of generating UL6 reactivity. Other lines of evidence also failed to support the molecular mimicry hypothesis, such as the failure to affect HSK severity upon tolerization of susceptible BALB/c and B-cell-deficient mice with IgG2a(b) or UL6 peptides. An additional study system revealed that HSK could be induced in mouse strains, such as the OT2 x RAG1(-/-) mice (T cell receptor transgenic recognizing OVA(323-339)) that were unable to produce CD4(+) T-cell responses to any detectable HSV antigens. Our results cast doubt on the molecular mimicry hypothesis as an explanation for the pathogenesis of HSK and indicate that if autoimmunity is involved its likely proceeds via a bystander activation mechanism.