Oral acyclovir reduces the incidence of recurrent herpes simplex keratitis in rabbits after penetrating keratoplasty

To determine if acyclovir sodium prevents postoperative herpes simplex virus type 1 (HSV-1) recurrences, 21 rabbits harboring latent HSV-1 underwent uniocular autograft penetrating keratoplasty. All operated-on eyes were treated with topical and subconjunctival dexamethasone sodium phosphate. Ten of the 21 rabbits also received oral acyclovir (intravenous acyclovir was given at the time of surgery). Postoperatively, 9 (82%) of 11 operated-on eyes in rabbits not treated with acyclovir had positive HSV-1 ocular cultures. In acyclovir-treated rabbits, however, none of the 10 operated-on eyes had positive ocular cultures. In addition, 9 (82%) of 11 of the operated-on eyes had geographic ulcers develop in the non-acyclovir-treated rabbits, compared with 1 (10%) of 10 in the acyclovir-treated rabbits. Finally, stromal keratitis appeared in 5 (56%) of 9 of the operated-on eyes in non-acyclovir-treated rabbits and 1 (12%) of 8 of the operated-on eyes in acyclovir-treated rabbits. The results of this study indicate that acyclovir significantly lowered the incidence of HSV-1 ocular shedding, geographic ulceration, and stromal keratitis in a rabbit autograft penetrating keratoplasty model.

Exogenous, ocular, and systemic factors associated with keratitic ulceration

Information on type and frequency of empirically observed exogenous, ocular, and systemic predisposing factors for keratitic ulceration is important for clinical identification of groups at risk and may form a basis for planning experimental studies on the pathogenesis of ulceration. Therefore a retrospective study comprising 104 patients with 25 herpetic and 79 non-herpetic corneal ulcerations was performed. Patients with herpetic ulcerations were mainly males and were younger than patients with non-herpetic corneal ulceration. Keratoplasty and steroid treatment was found as frequent co-existing predisposing factors in the herpetic group. In the non-herpetic group an exogenous factor was found in 56%, an ocular factor in 56%, and a systemic predisposing factor in 46% of the patients. In only 2.5% of these patients was there found no predisposing factor. Pathogenetic mechanisms of predisposing factors for non-herpetic corneal ulceration is discussed.

Alterations in the antigenic structure of two major HSV-1 glycoproteins, gC and gB, influence immune regulation and susceptibility to murine herpes keratitis

We previously demonstrated that anterior chamber (AC) injection of HSV-1 before or simultaneous with topical corneal HSV-1 infection resulted in cellular immune tolerance of HSV-1 Ag and a reduced frequency of corneal stromal lesions. In the present study, we have investigated the role of the HSV-1 cell-surface glycoproteins gC and gB in the induction of tolerance, and the resulting reduced susceptibility to HSV-1 corneal stromal disease. These studies utilized mutant strains of HSV-1 with deletion or point mutations in the gene coding for gC or gB. Groups of mice received topical corneal infections with wild-type HSV-1, followed by AC injection of the same eye with wild-type HSV-1 or a mutant strain. Varying the antigenic composition of the virus injected into the AC resulted in three distinct patterns of immune responsiveness. In agreement with our previous findings, AC injection of wild-type HSV-1 induced a state of HSV-1 specific tolerance that extended to both the delayed type hypersensitivity (DTH) and CTL responses. A mutant strain lacking gC (gC-) induced partial tolerance characterized by undetectable CTL activity but a normal DTH response. A mutant strain lacking gB (gB-) caused partial suppression of the CTL response and no reduction of the DTH response. Thus, whereas gB may be involved in CTL tolerance induction in this model, gC clearly is not involved. In contrast, both gC and gB must be present in the AC to induce detectable DTH tolerance. The latter interpretation was strengthened by the observation that AC injection of a mixture of gC- (expressing normal gB) and gB- (expressing normal gC) effectively suppressed the DTH response to wild-type HSV-1. A panel of mar mutants with individual point mutations affecting gC and gB was used to identify the epitopes responsible for induction of DTH tolerance. Two of the gC mutants failed to induce DTH tolerance to wild-type HSV-1 when injected into the AC, suggesting that the sites on the gC molecule that are altered by these mutations are important for the induction of DTH tolerance. Similarly, one of the mar mutants for gB uniformly failed to suppress the DTH response, while another had a variable effect. The unique pattern of cellular immune reactivity exhibited by the mice receiving simultaneous topical corneal infection with wild-type HSV-1 and AC injection of gC- (no CTL but normal DTH) was associated with significantly reduced susceptibility to HSV-1 corneal stromal lesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Ocular herpes simplex infection: pathogenesis and current therapy

Ocular herpes simplex disease has a variable pattern of manifestations and recurrences as a result of the site and extent of the infection, the host immunologic events, the trophic damage within ocular tissues, and the toxic effects of antiviral medications. Laboratory research has established a clinical model and a working hypothesis about the complex pathophysiologic features of the disease and the interaction of the virus with its host tissue. Recent studies have further defined the viral genome and its role in virulence and pathogenicity. Antiviral therapy is effective in some but not all aspects of the ocular infection. A proposed clinical classification of ocular herpes simplex is based on the manifestations associated with viral disease and those associated with the host response and the subsequent structural damage. A plan for medical and surgical management of ocular herpes simplex, based on current knowledge of the disease process, relates to the integrity of the epithelium and the presence of active viral disease.

Bilateral alterations of the ERG and retinal histology following unilateral HSV-1 inoculation

The physiological condition of the retinas of BALB/c mice inoculated unilaterally in the anterior chamber with the KOS strain of herpes simplex virus type 1 (HSV-1) was monitored by ERG recordings. After the ERG recordings, the retinas were examined for histopathological changes. In the inoculated eye, depressed ERGs were recorded on day 2 PI and abolished ERGs on day 4 PI. The changes in the ERGs were complete by day 5-6 PI. Of the 53 inoculated eyes followed for longer than day 6 PI, four (7.5%) remained normal, 30 (56.6%) had reduced ERGs and 19 (35.8%) had abolished ERGs. In the contralateral eyes, the first changes were noted on day 8 PI, and abolished ERGs were recorded on day 9 PI. Of the 55 contralateral eyes followed for longer than 10 days, 15 (27.3%) remained normal, four (7.2%) had reduced ERGs and 36 (65.4%) had abolished ERGs. The percentage of eyes with depressed ERGs was significantly higher in the inoculated than in the uninoculated eyes, and the percentage of eyes with abolished ERGs was significantly higher in the uninoculated eyes than in the inoculated eyes. The histopathological alterations were different for the two eyes. In the inoculated eyes, the changes were mainly in the outer retina, with characteristic folds in the photoreceptor and outer nuclear layer interspersed with normal appearing retina. The pigment epithelium was also abnormal. In the uninoculated eyes, the changes began in the inner retina but rapidly spread to all layers of the retina. This panretinal necrosis accounted for the higher percentage of abolished ERGs in the uninoculated eyes. The differences in the alterations of the ERG and the histopathological changes may be related to the underlying mechanism of action of the HSV-1 during the evolution of the experimental retinopathy.

Immunogenicity versus pathogenicity after anterior chamber inoculation of an acyclovir-induced double mutant of HSV-1

The acyclovir-induced herpes simplex virus Type 1 (HSV-1) strain, R9C2, a double mutant in thymidine kinase (TK) and DNA polymerase (DNA pol), and its parental strain SC16 were compared for their effects on ocular pathology and systemic immunity after unilateral inoculation into the anterior chamber (AC) of BALB/c mouse eyes. Although AC-injected R9C2 produced no retinal necrosis (0/18 eyes), this mutant induced active suppression (33-87%) of anti-HSV delayed type hypersensitivity similar to that induced by another HSV strain, KOS. AC-injected parental strain, SC16, caused fatal disease within 7-10 days, and induced bilateral retinal necrosis and suppression of DTH in 100% of the mice. Preimmunization with R9C2 protected mice in a dose-dependent fashion from the pathologic and lethal effects of AC-injected parental virus. These data suggest that the immunogenicity of the TK and DNA pol double mutant remains intact despite the decreased ocular and systemic pathogenicity observed after intracameral inoculation.

Immunological complications of soft contact lenses

Immunologic reactions may be the basis of some complications associated with the use of soft contact lenses. In the case of giant papillary conjunctivitis, the antigen causing the problem is not known but is presumed to be protein adherent to the lenses. Superior limbic keratoconjunctivitis and dendritic corneal lesions related to soft contact lenses are associated with thimerosal, but occlusive patch tests do not demonstrate consistent delayed hypersensitivity responses to this preservative in these patients, suggesting that a toxic response may be involved. The association of corneal infiltrates and conjunctival hyperemia with delayed hypersensitivity to thimerosal probably represents the strongest immunologic association to date. These patients consistently show delayed hypersensitivity reactions to thimerosal in occlusive patch tests and intradermal tests.

Ocular involvement associated with chronic Epstein-Barr virus disease

Ocular involvement with acute Epstein-Barr virus infection is usually limited to a transient follicular conjunctivitis, although other lesions have been reported. Chronic Epstein-Barr virus infection has recently gained attention, but ocular manifestations have not been emphasized. We describe three patients with chronic infection with prominent ocular involvement. Bilateral uveitis was noted in all patients, ranging from an anterior uveitis that was responsive to steroids to a severe panuveitis with vitritis, cataract, optic disc swelling, and macular edema. In one patient, topical acyclovir ointment resulted in a substantial decrease in the inflammatory reaction when added to systemic acyclovir therapy. Another patient displayed a keratitis that resolved with topical steroid therapy. Cataract and vitreous surgery were also beneficial in the management of these patients.

Recurrent herpes simplex virus type 1 corneal epithelial lesions after radial keratotomy in the rabbit

The effects of radial keratotomy (RK) on herpes simplex virus type 1 ocular shedding and recurrent corneal epithelial lesions were assessed for 14 days after RK in rabbits latently infected with strain McKrae. Ten latently infected rabbits had RK performed on the right eye. The left eye was used as the control. Viral shedding was monitored by ocular tear-film swabs. The recurrent lesions were monitored by slit-lamp examination. In the RK-treated eyes, 15 (11%) of 140 swabs were positive, compared with six (4%) of 140 swabs in control eyes. Slit-lamp examination disclosed recurrent lesions on 18 (33%) of 55 days on which it was performed in the RK group vs three (5%) of 55 days for the control group. The results suggest that patients who have a history of ocular herpes simplex virus type 1 disease are at risk for recurrences after RK.

[Activation of a herpetic infection via corneal transplantation]

Activation of herpes infection in keratoplasty was studied in 26 patients and found to be caused both by operative intervention and the corresponding corticosteroid therapy. The fluorescent antibody technique proved to be the most effective and rapid test for the detection of herpes infection. It is recommended to carry out laboratory control in transplantation of the cornea as well as topical antiviral therapy in the postoperation period not only in patients with herpetic keratitis but also in the subjects operated on for nonspecific leukoma and other diseases of the cornea.

Role of virus-infected mononuclear leukocytes in herpetic chorioretinitis of newborn rabbits

The role of virus-infected mononuclear leukocytes (MNLs) in the pathogenesis of neonatal herpetic chorioretinitis in newborn rabbits was investigated. As early as 2 days after inoculating the animals' skins with type 2 herpes simplex virus (HSV-2), infectious MNLs in the infected animals' peripheral blood were found. The virus was associated, for the most part, with MNLs that belonged to phagocytic and adherent cell fractions. Observations by electron microscopy indicated that HSV-2 was actively replicating in the MNLs. It was also found that as few as 80 virus-infected MNLs injected via the right common carotoid artery were capable of inducing the chorioretinal lesions in 50% of the eyes, but that as many as 10(3) Pfu of free virus were required to produce the same lesions in the same percentage of eyes. This result clearly indicated that virus-infected MNLs were far more efficient in producing chorioretinitis than free virus, and may thus play a crucial role in the pathogenesis of herpetic chorioretinitis in newborn rabbits. When 111In-labeled virus-infected or uninfected MNLs were injected into normal rabbits via the right common carotid artery, the virus-infected MNLs localized more readily in the eye than the uninfected MNLs. The virus-infected MNLs also attached to the cultured vascular endothelial cells significantly more often than the uninfected MNLs. These results suggested that virus-infected MNLs might be easily trapped in the circulation of the eye and, in this way, produce the ocular lesions.

Neonatal herpes simplex virus infections. Presentation and management

Neonatal herpes simplex virus (HSV) infections are recognized to be severe because of their association with significant morbidity and mortality. Through ongoing studies performed by the National Institute of Allergy and Infectious Diseases Collaborative Antiviral Study Group, the presentation, natural history, outcome and value of antiviral chemotherapy have been considered. Infants developing neonatal HSV infections can be classified according to the extent of disease, disseminated or localized. Localized infection can be subdivided into either central nervous system (CNS) disease, occurring in 35% of infected infants, or skin, eye and mouth (SEM) disease, in 41% of infants. Disseminated disease accounts for 24% of neonatal HSV infection. Therapeutic outcome depends upon disease classification. Administration of either 15 or 30 mg/kg/day of vidarabine resulted in significantly decreased mortality for infants with life-threatening disseminated and CNS disease as compared to placebo recipients. Approximately one-third of children developed normally following disseminated disease or CNS infection. When disease was localized to the SEM, no death occurred, and 88% of treated infants developed normally. While these data indicate that therapy is effective for management of infants with neonatal HSV infection, improvements are necessary. Hopefully, a study in progress will demonstrate improved outcome with acyclovir treatment.

[Dendritic keratitis following corneal foreign body]

Traumatogenic herpetic eye disease may be initiated via several pathophysiologic pathways. Trauma of the trigeminal ganglion or adequate systemic alterations are the most effective means of destabilizing ganglionic latency of the herpesvirus with consequent neuronal peripheral virus shedding. Peripheral stimuli seem to have far less effect on ganglionic latency--at least in man. The authors report on a rare case of proven herpetic primary disease. The trigger was probably a small intrastromal foreign body which caused an unusual alteration of the cornea with long-standing healing disorders.

Adrenergic induction of HSV-1 ocular shedding in rabbits

Four groups of latently infected rabbits were induced to shed HSV-1 into the tear film by a one-time ocular iontophoresis of 6-hydroxydopamine (6-HD) followed 3 days later by five consecutive days of twice daily topical epinephrine (Epi). Groups 1 and 4 had both eyes inoculated and Groups 2 and 3 had only one eye inoculated. Groups 1 and 2 had eyes swabbed to detect HSV-1, and Groups 3 and 4 had eyes washed. Group 1 was iontophoresed with 1.0% 6-HD at 0.5 mAmp for 5 min, and Groups 2, 3 and 4 were iontophoresed with 0.1% 6-HD at 0.75 mAmp for 5 min. Group 1 received topical 2.0% Epi, and Groups 2, 3, and 4 received topical 1.0% Epi. Inoculated eyes in all groups shed HSV-1 during the induction period. The peak of HSV-1 shedding occurred on the last day of Epi application for Groups 1 and 2, and on the day after the last Epi application for Groups 3 and 4. The ratio of total positive tear film samples to total samples for inoculated eyes that received 6-HD and Epi were 53/119 (45%), 38/87 (44%), 24/66 (36%), and 14/33 (42%) for Groups 1, 2, 3, and 4, respectively. Therefore, even reduced concentrations of 6-HD and Epi, as well as beginning Epi 3 days after 6-HD, induced HSV-1 ocular shedding.

[Development and practical use of new experimental models of the various forms of herpetic infection]

New experimental models of neurological herpes in cotton rats and genital herpes in male guinea pigs have been developed which are more adequate to the corresponding human diseases, and models of ophthalmic herpes in rabbits and guinea pigs have been improved. These models may be used for screening and evaluation of the effectiveness of drugs for herpes. A high activity against herpes of bromovinyldeoxyuridine and acyclovir has been verified, a marked therapeutic effect of Soviet monophosphates ara-A, ara-C, and original silur preparation in some forms of herpes infection has been demonstrated.

An animal model of ocular herpes. Keratitis, retinitis and cataract in the mouse

Acute ocular infection followed both intracerebral and intranasal inoculation of herpes simplex type I virus (HSVI) in mice. Eye infections were a terminal complication of fatal encephalitis. After intracerebral inoculation HSVI spread directly along the optic nerves to infect the retina provoking a necrotizing retinitis. In contrast after intranasal inoculation, HSVI spread via the fifth cranial nerve to the anterior chamber of the eye producing keratitis and uveitis. Necrotizing retinitis was also produced by intracerebral inoculation of mice with a drug-resistant mutant HSVI known to have relatively low neurovirulence. These animals developed only mild encephalitis but this was associated with florid retinitis. The mice survived cerebral infection with the mutant virus and several weeks after initial inoculation cataracts were observed. There was no evidence, at any time, of virus infection of lens epithelium and cataracts appeared to be a non-specific consequence of retinal injury. It is suggested that these examples of murine ocular infection provide animal models for herpetic eye lesions in man and thus may elucidate the pathogenesis of herpetic keratitis, retinitis and cataract.

Microbial factors in contact lens fitting

As contact lens practitioners, optometrists work in a nonsterile environment and on a nonsterile part of the human body. Our report describes 10 cases of eye infection related to contact lens wear. Practitioners need to be aware of the problems which can occur when a thoroughly sterilized contact lens is placed on an unsterile and biologically complex eye. We recommend taking swabs of the conjuctiva in all eyes where ocular inflammation is present. In those areas in which the professions of optometry and medicine meet, cooperation should exist. Improving our knowledge and skills in microbiology helps to facilitate such cooperation. Our experience has been most rewarding and interaction in this field with medical practitioners has been positive. The use of a high quality slitlamp is essential.

Ocular complications of atopic dermatitis

Atopic dermatitis is a common skin disease associated with other allergic diatheses. Ocular complications were seen in 85 (42.5%) of 200 patients. Blepharoconjunctivitis, cataracts, corneal disease and ocular herpes simplex were frequent. Cataract surgery was usually successful, but there were complications of such surgery. The rate of success in attempts to wear contact lenses was surprisingly high for both phakic and aphakic patients.