Biology and molecular aspects of herpes simplex and varicella-zoster virus infections

Adoption of Innovation in Herpes Simplex Virus Keratitis

Herpes simplex keratitis, caused primarily by human herpes simplex virus type 1 (HSV-1), remains the most common infectious cause of unilateral blindness and vision impairment in the industrialized world. Major advances in the care of HSV keratitis have been driven in large part by the landmark Herpetic Eye Disease Study randomized clinical trials, which were among the first in ophthalmology to reflect emerging trial conventions, including multicenter subject enrollment, double-masking, placebo controls, and a priori sample size determinations. The results of these trials now form much of the evidence basis for the management of this disease. However, management patterns in clinical practice often deviate from evidence-based care. These perceived quality gaps have given rise to the evolving field of implementation science, which is concerned with the methods of promoting the application of evidence-based medicine within routine care. To overcome variations in the quality and consistency of care for HSV keratitis, a range of clinical- and technology-based innovations are proposed. The most pressing needs include the following: a rational and tractable disease classification scheme that provides an immediate link between the anatomical localization of disease (corneal epithelial, stromal, or endothelial) and the appropriate treatment, and the actualization of an electronic medical record system capable of providing evidence-based treatment algorithms at relevant points of care. The latter would also input data to population-wide disease registries to identify implementation-rich targets for quality improvement, education, and research. These innovations may allow us to reduce the human and economic burdens of this highly morbid, and often blinding, disease.

Role of TH17 Responses in Increasing Herpetic Keratitis in the Eyes of Mice Infected with HSV-1

Purpose

T_H17 cells play an important role in host defense and autoimmunity yet very little is known about the role of IL17 in herpes simplex virus (HSV)-1 infectivity. To better understand the relationship between IL17 and HSV-1 infection, we assessed the relative impact of IL17A-deficiency and deficiency of its receptors on HSV-1 responses in vivo.

Methods

We generated IL17RA^−/− and IL17RA^−/−RC^−/− mice in-house and infected them along with IL17A^−/− and IL17RC^−/− mice in the eyes with 2 × 10⁵ PFU/eye of wild type (WT) HSV-1 strain McKrae. WT C57BL/6 mice were used as control. Virus replication in the eye, survival, corneal scarring (CS), angiogenesis, levels of latency-reactivation, and levels of CD8 and exhaustion markers (PD1, TIM3, LAG3, CTLA4, CD244, and CD39) in the trigeminal ganglia (TG) of infected mice were determined on day 28 postinfection.

Results

No significant differences in virus replication in the eye, survival, latency, reactivation, and exhaustion markers were detected among IL17A^−/−, IL17RA^−/−, IL17RC^−/−, IL17RA^−/−RC^−/−, and WT mice. However, mice lacking IL17 had significantly less CS and angiogenesis than WT mice. In addition, angiogenesis levels in the absence of IL17RC and irrespective of the absence of IL17RA were significantly less than in IL17A- or IL17RA-deficient mice.

Conclusions

Our results suggest that the absence of IL17 protects against HSV-1-induced eye disease, but has no role in protecting against virus replication, latency, or reactivation. In addition, our data provide rationale for blocking IL17RC function rather than IL17A or IL17RA function as a key driver of HSV-1-induced eye disease.

Ocular herpes: the pathophysiology, management and treatment of herpetic eye diseases

Herpesviruses are a prominent cause of human viral disease, second only to the cold and influenza viruses. Most herpesvirus infections are mild or asymptomatic. However, when the virus invades the eye, a number of pathologies can develop and its associated sequelae have become a considerable source of ocular morbidity. The most common culprits of herpetic eye disease are the herpes simplex virus (HSV), varicella zoster virus (VZV), and cytomegalovirus (CMV). While primary infection can produce ocular disease, the most destructive manifestations tend to arise from recurrent infection. These recurrent infections can wreck devastating effects and lead to irreversible vision loss accompanied by a decreased quality of life, increased healthcare usage, and significant cost burden. Unfortunately, no method currently exists to eradicate herpesviruses from the body after infection. Treatment and management of herpes-related eye conditions continue to revolve around antiviral drugs, although corticosteroids, interferons, and other newer therapies may also be appropriate depending on the disease presentation. Ultimately, the advent of effective vaccines will be crucial to preventing herpesvirus diseases altogether and cutting the incidence of ocular complications.

Corneal neovascularization and the utility of topical VEGF inhibition: ranibizumab (Lucentis) vs bevacizumab (Avastin)

Corneal avascularity is necessary for the preservation of optimal vision. The cornea maintains a dynamic balance between pro- and antiangiogenic factors that allows it to remain avascular under normal homeostatic conditions; however, corneal avascularity can be compromised by pathologic conditions that negate the cornea's "angiogenic privilege." The clinical relevance of corneal neovascularization has long been recognized, but management of this condition has been hindered by a lack of safe and effective therapeutic modalities. Herein, the etiology, epidemiology, pathogenesis, and treatment of corneal neovascularization are reviewed. Additionally, the authors' recent findings regarding the clinical utility of topical ranibizumab (Lucentis®) and bevacizumab (Avastin®) in the treatment of corneal neovascularization are summarized. These findings clearly indicate that ranibizumab and bevacizumab are safe and effective treatments for corneal neovascularization when appropriate precautions are observed. Although direct comparisons are not conclusive, the results suggest that ranibizumab may be modestly superior to bevacizumab in terms of both onset of action and degree of efficacy. In order to justify the increased cost of ranibizumab, it will be necessary to demonstrate meaningful treatment superiority in a prospective, randomized, head-to-head comparison study.

Incidence, recurrence, and outcomes of herpes simplex virus eye disease in Olmsted County, Minnesota, 1976-2007: the effect of oral antiviral prophylaxis

OBJECTIVES

To provide an estimate of the incidence of herpes simplex virus (HSV) eye disease in a community-based cohort, and to investigate the effect of prophylactic oral antiviral therapy on HSV recurrences and outcomes.

METHODS

All Olmsted County, Minnesota, residents diagnosed with ocular HSV from 1976 through 2007 were retrospectively reviewed. The frequency of recurrences and adverse outcomes, such as vision loss or need for surgery, were compared between untreated patients and those treated prophylactically with oral antiviral medication.

RESULTS

Three hundred ninety-four patients with ocular HSV were identified, yielding an annual incidence of 11.8 per 100,000 people (95% confidence interval [CI], 10.6-13.0). No trends in incidence or adverse outcomes were identified during the 32-year period. Oral antiviral therapy was prescribed in 175 patients. Patients were 9.4 times more likely (95% CI, 5.0-17.9) to have a recurrence of epithelial keratitis, 8.4 times more likely (95% CI, 5.2-13.7) to have a recurrence of stromal keratitis, and 34.5 times more likely (95% CI, 10.8-111.1) to have a recurrence of blepharitis or conjunctivitis if not being treated prophylactically at the time of the recurrence. Twenty patients experienced adverse outcomes, and 17 (85%) were not being treated with oral antiviral medications immediately preceding the adverse event.

CONCLUSIONS

Oral antiviral prophylaxis was associated with a decreased risk of recurrence of epithelial keratitis, stromal keratitis, conjunctivitis, and blepharitis due to HSV. Patients with adverse outcomes due to ocular HSV were usually not being treated with oral antiviral prophylaxis.

A viral model for corneal scarring and neovascularization following ocular infection of rabbits with a herpes simplex virus type 1 (HSV-1) mutant

PURPOSE

Herpes simplex virus type 1 (HSV-1) remains a major cause of corneal scarring and visual loss. Although efforts have been made, no reproducible animal model is available to examine recurrent corneal disease. Here we propose a rabbit ocular model to study recurrent corneal disease using an HSV-1 mutant that reactivates with high efficiency.

METHODS

Rabbits were ocularly infected with 2 x 10 PFU/eye of the parental McKrae, dLAT2903 (a LAT-null virus with a low-reactivation phenotype), or CJLAT (a high-reactivation virus). Acute ocular disease [days 2, 4, 7, and 10 postinfection (pi)], recurrent ocular disease, and neovascularization (days 30 to 58 pi) were monitored.

RESULTS

All acute ocular disease symptoms, including conjunctivitis and corneal disease, were similar with all 3 viruses. No corneal scarring was detected in any eyes up to day 30 pi. Between days 35 and 58 pi, corneal scarring was observed in 11/14 (experiment 1) and 18/22 (experiment 2) eyes of CJLAT-infected rabbits. Significantly less corneal scarring was seen in eyes of rabbits infected with McKrae (0/18 and 0/16) or dLAT2903 (0/16 and 3/24) (P < 0.0001). Many of the eyes with corneal scarring developed obvious, measurable neovascularization.

CONCLUSIONS

Rabbits infected with CJLAT developed corneal scarring and neovascularization similar to that of clinical ocular HSV-1 recurrent disease. Because this occurred well after the acute infection had resolved, the corneal scarring and neovascularization appeared to be recurrent disease. Thus, CJLAT ocular infection of rabbits may provide a good and reproducible animal model to study factors involved in corneal scarring and neovascularization from recurrent ocular HSV-1.

Concurrent reactivation of varicella zoster virus and herpes simplex virus in an immunocompetent child

Latency within the nervous system is a characteristic feature of herpesviridae infection. It is reactivated by triggering factors such as UV exposure, stress, and trauma. Simultaneous reactivation of herpes simplex and herpes zoster is uncommon, however, an observation provably explained by differences in the triggering mechanism. Concurrent reactivation of herpes simplex virus (HSV) and varicella zoster virus (VZV) is occasionally encountered in immunosuppressed patients; on the other hand, it is rarely reported in immunocompetent individuals. We present the case of an immunocompetent 8-yr-old female patient with concurrent reactivation of HSV on the face and VZV on the right L2 dermatome.

Herpes simplex virion entry into and intracellular transport within mammalian cells

Alphaherpesviruses, membrane-enveloped DNA viruses that are responsible for a host of human ailments, bind to, enter and are directly targeted to specific intracellular domains within their mammalian host cells. This review emphasizes recent work on the best studied of the alphaherpesviruses, Herpes simplex virus type 1 (HSV1). One area of focus is on recent work that has identified viral glycoproteins that are important in binding and internalization of the virus to the host cell. Complementary work on the receptors for those viral glycoproteins that reside on the host cell surface is also presented, with some discussion of how receptor variety might lead to the tissue tropism demonstrated by alphaherpes viruses. An additional area of focus in this review is how HSV uses the host cell transport systems to achieve intracellular targeting of the incoming virion toward the cell nucleus, and, after production of newly synthesized and assembled viral progeny, targeting them toward the plasma membrane for release.

Detection of herpes simplex virus in pseudoexfoliation syndrome and exfoliation glaucoma

PURPOSE

The pathogenesis of pseudoexfoliation syndrome (PEX) remains unknown. An infection, possibly viral, is one of the proposed pathogenetic mechanisms. This study examines the presence of herpes simplex virus (HSV) and varicella-zoster virus (VZV) in iris and anterior capsule specimens of PEX and non-PEX patients.

METHODS

Iris and anterior capsule specimens were obtained from 64 patients with PEX (study group, SG) and 61 patients without PEX (control group, CG). The presence of HSV and VZV DNA was evaluated with a polymerase chain reaction (PCR).

RESULTS

Herpes simplex virus type I was detected significantly more often in iris specimens from the SG (13.79%), compared to those from the CG (1.75%). Varicella-zoster virus DNA was not detected in any of the examined specimens.

CONCLUSION

Results imply a possible relationship between HSV type I and PEX, although no aetiological role of HSV infection in PEX pathogenesis can be established. Results also advocate against any association between VZV and PEX.

Corneal ulceration in pediatric patients: a brief overview of progress in topical treatment

Pediatric microbial keratitis is a rare but potentially devastating condition. The condition is similar to adult microbial keratitis, but is often characterized by a more severe inflammatory response. The micro-organisms that cause microbial keratitis in children are similar to the causative agents in adults, with herpes simplex and bacteria being the predominant causative agents, and fungi being less frequent. Of the bacterial pathogens, Pseudomonas aeruginosa, Staphylococcus aureus and alpha-hemolytic streptococci are common. The risk factors for pediatric keratitis include colonization of the eyes during birth and trauma to the cornea. Certain microbial factors involved in microbial keratitis are common to all micro-organisms, including adhesion to the cornea, penetration into the cornea, destruction of the corneal stroma (usually by microbial and/or host proteases), and recruitment of white blood cells to help defend the eye. Specific inflammatory responses that occur during pediatric microbial keratitis are not known in detail, but it is likely that cytokines and polymorphonuclear leucocytes are major factors, as they are in adult microbial keratitis. Treatment for pediatric microbial keratitis is usually the same as treatment for adult microbial keratitis; topical application of antimicrobial agents initially, followed by application of anti-inflammatory agents. With pediatric microbial keratitis, extra care must be taken to ensure nontoxicity due to blood adsorption. New microbial keratitis treatments are being developed and these mainly focus on new antimicrobials, antivirulence agents (such as vaccination against microbial toxins) or specific anti-inflammatory agents. There remains a clear need for increased research into the specific responses during microbial keratitis in children which will help progress new therapies as well as the development of new antimicrobials, especially new antifungal therapies.

Phase transitions in a model for the formation of herpes simplex ulcers

The critical properties of a cellular automaton model describing the spreading of infection of the herpes simplex virus in corneal tissue are investigated through the dynamic Monte Carlo method. The model takes into account different cell susceptibilities to the viral infection, as suggested by experimental findings. In a two-dimensional square lattice the sites are associated with two distinct types of cells, namely, permissive and resistant to the infection. While a permissive cell becomes infected in the presence of a single infected cell in its neighborhood, a resistant cell needs to be surrounded by at least R>1 infected or dead cells in order to become infected. The infection is followed by the death of the cells resulting in ulcers whose forms may be dendritic (self-limited clusters) or amoeboid (percolating clusters) depending on the degree of resistance R of the resistant cells as well as on the density of permissive cells in the healthy tissue. We show that a phase transition between these two regimes occurs only for R>/=5 and, in addition, that the phase transition is in the universality class of the ordinary percolation.

Prevalence of herpesviruses in cranial nerve ganglia

A number of cranial nerve disorders are known to result from viral infection or reactivation, including Bell's palsy, Ramsay Hunt syndrome and herpetic laryngitis. The consequences of these diseases are well established although the patient population at risk is not. Prevalence studies in the general population are an initial step toward defining individuals at risk. The aim of this study was to determine the prevalence of herpesvirus DNA in cranial nerve ganglia in a random population sample. Qualitative molecular biologic analysis using polymerase chain reaction assay of the trigeminal, geniculate, vestibular, spiral and vagal ganglia was used in 18 randomly selected fresh cadaver heads. Herpes simplex virus (HSV) DNA was detected in 42% of all ganglia surveyed. Varicella zoster virus (VZV) DNA was detected in 44% of all ganglia. The difference in the prevalence rate between viruses was not significant (p = 0.63). At least 1 of the 2 viruses was found in 65% of all ganglia. Both HSV and VZV can commonly be recovered from cranial nerve ganglia. In order to confirm a viral etiology for various cranial nerve disorders, demonstration of a significant difference in prevalence of the viruses in specimens from afflicted individuals will be necessary.

Herpes simplex virus epidemiology and ocular importance

PURPOSE

To review the changing epidemiology of herpes simplex disease and correlate it with the epidemiology of ocular herpes simplex disease.

METHOD

A review of pertinent reports in the world literature about the epidemiology of herpes simplex and specifically about ocular herpes simplex.

RESULTS

In developed countries, many individuals are reaching adolescence and adulthood without prior herpesvirus infection. Herpes simplex genital infection is increasing at a rapid rate in sexually active adolescents and adults, with about one in six adults now infected in the United States. Similar statistics are confirmatory worldwide in developed countries. Active herpes simplex infection is a risk factor for acquisition of human immunodeficiency virus. The Herpetic Eye Disease Study, as well as prior studies from Moorfields Eye Hospital and the Mayo Clinic in Rochester, Minnesota, provides us with the epidemiology of ocular herpes simplex. Recent studies suggest an older age of onset and perhaps overall more severe ocular disease as compared with the older literature.

CONCLUSIONS

Herpes simplex is a significant health concern at present with genital infections increasing in epidemic proportions. This is also reflected in a rise in the incidence of neonatal herpes. Herpes simplex virus type 1 (HSV-1) infection is being acquired for the first time in an older age group. A significant and increasing proportion of genital herpes is caused by HSV-1. Serologic studies are no longer as useful in distinguishing orofacial herpes from genital herpes. More acute retinal necrosis syndrome cases are associated with HSV-2. Speculation about the future of ocular herpes is made based on this changing epidemiology.

The prevalence of herpes family virus DNA in the conjunctiva of patients positive and negative for human immunodeficiency virus using the polymerase chain reaction

OBJECTIVE

To help understand the pathogenesis of herpes family virus ocular infection among patients positive for HIV, the authors compared the rates of detection of herpes family virus DNA from the conjunctiva of patients who are positive and negative for human immunodeficiency virus (HIV) using the polymerase chain reaction (PCR).

DESIGN

Cross-sectional study.

PARTICIPANTS

The conjunctival scrapings of 30 patients positive for HIV and 30 patients negative for HIV were examined.

INTERVENTION

PCR was used to assay for the presence of herpes simplex virus type 1 (HSV), varicella-zoster virus (VZV), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) DNA (n = 240 samples).

MAIN OUTCOME MEASURE

The rate of detection of virus DNA in the two groups, controlling for age, gender, and race, was measured.

RESULTS

HSV and VZV DNA were not detected in any of the HIV-positive or HIV-negative samples. CMV DNA was detected in 20% (6 of 30) of patients positive for HIV and was undetected in control subjects negative for HIV (P = 0.01). EBV DNA was detected in 40% (12 of 30) of patients positive for HIV and in 47% (14 of 30) of control subjects negative for HIV (P = 0.58).

CONCLUSIONS

There was no difference in the frequency of detection of HSV, VZV, or EBV DNA from the conjunctiva of patients positive or negative for HIV. Only CMV DNA was detected at a significantly higher rate in the conjunctiva of patients positive for HIV compared with control subjects negative for HIV. These different rates of peripheral virus shedding may be one possible explanation for the different rates of clinical infection among the herpes family viruses among patients positive for HIV.

Virus infections of the eye

In reviewing the clinical features, diagnostic evaluations and therapies of the most common ocular viral infections we attempt to whet your appetite for attacking the numerous challenges in diagnosis and treatment of viral eye disease. The herpes viruses, HSV, VZV and CMV are the cause of significant ocular morbidity. HSV most commonly affects the cornea producing keratitis that can be recurrent and may lead to corneal clouding and neovascularisation. Manifestations can be purely infectious or immunological and treatment options must be tailored to the underlying pathophysiology. Herpes zoster ophthalmicus, caused by VZV infection of the first branch of the trigeminal nerve, produces a characteristic rash and can progress to keratitis and uveitis. HSV and VZV can cause retinitis in both immunocompetent and immunocompromised individuals. There has been a significant increase in the incidence of CMV retinitis since the beginning of the AIDS epidemic. We review the numerous new treatments, diagnostic tests and treatment strategies which have been developed in response to this potentially blinding retinal infection. Adenovirus produces an epidemic conjunctivitis and epidemic keratoconjunctivitis which are severe and extremely contagious conjunctival infections. HIV, molluscum contagiosum, EBV and rubeola also cause ocular diseases which are described.Copyright 1998 John Wiley & Sons, Ltd.

Detection of varicella zoster virus DNA and viral antigen in human eyes after herpes zoster ophthalmicus

OBJECTIVE

The purpose of the study was to identify varicella zoster virus (VZV) DNA and viral antigen in human eyes at various intervals after clinical onset of herpes zoster ophthalmicus (HZO).

DESIGN

A retrospective case series.

PARTICIPANTS

There were 9 eyes and 4 corneal buttons surgically obtained from 13 patients with HZO at the University Eye Hospital of Erlangen-Nürnberg between 1984 and 1994. Specimens were examined at different timepoints after clinical onset of HZO (range, 1 day-19 years; median, 36 months).

METHODS

Histopathologic evaluation was performed on formalin-fixed and paraffin-embedded tissue by routine histology, immunohistochemistry (5-B-7 murine monoclonal antibody to VZV; peroxidase-antiperoxidase method), and DNA-in situ hybridization (35S deoxyadenosine triphosphate-labeled HindIII fragments [A and C] of VZV).

RESULTS

Typical histopathologic changes associated with HZO were identified: vascularization of the corneal stroma (11 of 13), granulomatous reaction to Descemet's membrane (8 of 13), fusiform-shaped ciliary scarring (5 of 9), optic neuritis (4 of 9), and perineuritis (8 of 9) and perivasculitis (8 of 9) of the long posterior ciliary nerves and arteries. VZV antigen was detected in two patients with acute infection 1 and 7 days after onset of HZO, respectively. VZV-DNA was identified in seven patients up to 10 years after onset of HZO in corneal epithelial cells (2 of 13), corneal stroma (5 of 13), inflammatory infiltrate of the anterior chamber (1 of 9), episclera (2 of 9), posterior ciliary nerves (1 of 9) and arteries (5 of 9), optic nerve (5 of 9), and adjacent leptomeninges (2 of 9).

CONCLUSION

Persistence of viral genomes, most likely accompanied by gene expression or slow viral replication, appears to be responsible for the often smoldering panophthalmitis and the chronic recurrent keratouveitis in patients with HZO. Localization of viral DNA in vascular structures suggests a role for vasculitis in the pathogenesis of some ocular findings associated with HZO.

Ocular complications of heart, lung, and liver transplantation

AIM

To document the nature and frequency of ocular complications in a large group of patients who underwent heart, lung, or liver transplantation.

METHODS

A retrospective audit of the medical records of all patients undergoing heart, lung, or combined heart-lung transplantation at St Vincent's Hospital, Sydney, or liver transplantation at Royal Prince Alfred Hospital Sydney, was performed to detect patients with symptomatic ocular complications following transplantation. 19 of 860 patients were identified as having ocular complications.

RESULTS

Ocular complications occurred in 2% of patients with 65% of these being opportunistic infections. Herpes group viral retinitis (77%) and fungal chorioretinitis (22%) were seen. Other complications included choroidal pseudolymphoma, central retinal vein occlusion, herpes zoster ophthalmicus, herpetic keratitis, dacryocystitis, cyclosporin retinopathy, and rifabutin associated uveitis.

CONCLUSION

Herpes group viral retinitis was the most common ocular opportunistic infection and occurred most frequently during the second year after transplantation. Delayed diagnosis was associated with poor visual outcome.

Aerosolization of infectious virus by excimer laser

PURPOSE

To determine the potential for aerosolization of infectious virus present within the tear film during excimer laser photoablation of the cornea.

METHODS

Cell monolayers infected with herpes simplex virus or adenovirus, simulating virus-infected corneas, were ablated with the 193-nm excimer laser. Adjacent dishes containing noninfected cell monolayers were subsequently assayed for viral infection.

RESULTS

Viral spread to sentinel dishes occurred with both herpes simplex and adenovirus. The titer of virus present in the infected cell monolayers influenced the likelihood of spread to adjacent dishes. The presence of a vacuum aspiration system appeared to influence the direction of virus spread, with dishes located in the direction of the vacuum most likely to contain virus.

CONCLUSIONS

The potential for aerosolization of infectious virus exists with photoablation using a large-diameter excimer laser beam. Our experimental design, however, does not prove that spread of infectious virus is likely to occur in the clinical setting. Appropriate measures should be taken to reduce the possibility of the spread of virus from the patient to the surgeon, other medical staff, or other patients.

DNA amplification for the in vitro detection of Candida albicans in head and neck squamous cell carcinomas

DNA was extracted from whole cells of Candida albicans and digested with HindIII restriction enzyme. After electrophoresis in a segment of the lane containing between 800 and 1200 base pairs (bp) of DNA fragments, a 1.1-kilobase (kb) fragment was found that hybridizes to biopsied tumor cells from head and neck squamous cell carcinomas (SCC). From the nucleotide sequence of the putative gene locus, primers were synthesized for use in a polymerase chain reaction (PCR) with DNA extracted from 18 SCC of the upper aerodigestive tract. After 30 cycles of amplification all tumors were found to contain sufficient amplified DNA to be detected in polyacrylamide or agarose gels. In contrast, template DNA from lymph nodes and malignant lymphomas failed to generate positive signals under these conditions. However, samples of DNA obtained from head and neck SCC cells in vitro, Candida glabrata, and Candida parapsilosis after PCR were found to contain homologous sequences. Application of this technique to head and neck SCC biopsies may help to identify quickly the presence of concurrent candidal species.

Recombinants are isolated at high frequency following in vivo mixed ocular infection with two avirulent herpes simplex virus type 1 strains

Mixed infections with different strains of herpes simplex virus type 1 (HSV-1) may result in more severe disease than infection with either strain alone. This phenomenon is important because it may facilitate the identification of virulence genes through the transfer of virulence determinants between complementing strains, and it may pose a problem in the use of attenuated HSV strains for vaccines and gene delivery vectors. In this study, we have compared the percentage of recombinants present after mixed infection with HSV-1 strains OD4 and 994 in vitro and in vivo. After corneal inoculation, we found that 74% of randomly picked isolates from the trigeminal ganglia were recombinants, compared with 59% from the cornea. Twenty-six percent of randomly picked isolates were recombinant following mixed infection of Vero cells in vitro. Seventeen recombinant strains isolated from the in vivo mixed infections were assayed for ocular virulence, and they were found to exhibit a wide range of virulence phenotypes. The presence of virulent recombinants suggests that recombination plays a role in the increased disease observed in this mixed infection, and the broad range of virulence indicates that there may be multiple genetic factors involved in the increased virulence observed after mixed infection with these two strains. The recombinants were also tested for their ability to grow in NIH 3T3 fibroblasts, and though some correlation was observed between growth in vitro and ability to cause ocular disease, improved growth in murine cells does not sufficiently explain the increased virulence observed in some recombinants.

Recurrence and rejection rates following corneal transplantation for herpes simplex keratitis

Seventy-two penetrating primary keratoplasties for herpes simplex keratitis performed from 1970 to 1993 were reviewed. Postoperative follow-up periods ranged from 6 months to 16 years with 2 years median. Epithelial herpetic recurrence occurred in 25% of the transplants the first year and in 44% during the first 2 years. Primary allograft rejection was observed in 29% of the grafts the first year and in 46% during the first 2 years. Preoperative inflammation was a risk factor for preservation of a clear cornea (p < 0.10). The degree of corneal vascularization prior to operation did not influence the survival of the grafts. The overall one-year survival rate of a clear graft was 84% and the 2-year survival rate was 67%. Prophylactic antiviral treatment is discussed.

Herpetic Eye Disease Study. A controlled trial of topical corticosteroids for herpes simplex stromal keratitis

PURPOSE

To evaluate the efficacy of topical corticosteroids in treating herpes simplex stromal keratitis.

METHODS

The authors performed a randomized, double-masked, placebo-controlled, multicenter clinical trial of 106 patients with active herpes simplex stromal keratitis who had not received any corticosteroids for at least 10 days before study enrollment. Patients were assigned to the placebo group (n = 49) or the steroid group (topical prednisolone phosphate; n = 57); both regimens were tapered over 10 weeks. Both groups received topical trifluridine. Visual acuity assessment and slit-lamp biomicroscopy were performed weekly for 10 weeks, every other week for an additional 6 weeks or until removal from the trial, and at 6 months after randomization.

RESULTS

The time to treatment failure (defined by specific criteria as persistent or progressive stromal keratouveitis or an adverse event) was significantly longer in the steroid group compared with the placebo group. Compared with placebo, corticosteroid therapy reduced the risk of persistent or progressive stromal keratouveitis by 68%. The time from randomization to resolution of stromal keratitis and uveitis was significantly shorter in the steroid group compared with the placebo group even though both groups included patients who were removed from the study and treated with topical corticosteroids according to best medical judgment. Nineteen (33%) of the steroid-treated patients and 11 (22%) of the placebo-treated patients completed the 10 weeks of protocol therapy and had stable, noninflamed corneas after 16 weeks. At 6 months after randomization, no clinically or statistically significant differences in visual outcome or recurrent herpetic eye disease were identified between the steroid and placebo groups.

CONCLUSIONS

The topical corticosteroid regimen used in this study was significantly better than placebo in reducing persistence or progression of stromal inflammation and in shortening the duration of herpes simplex stromal keratitis. Postponing steroids during careful observation for a few weeks delayed resolution of stromal keratitis but had no detrimental effect as assessed by visual outcome at 6 months.

Association of herpes zoster ophthalmicus with acquired immunodeficiency syndrome and acute retinal necrosis

We conducted a review to investigate the prevalence of human immunodeficiency virus (HIV), or acquired immunodeficiency syndrome (AIDS), in patients with herpes zoster ophthalmicus, as well as the incidence of acute retinal necrosis after herpes zoster ophthalmicus. All charts of patients seen at our institution between 1987 and 1992 with a primary diagnosis of herpes zoster ophthalmicus were reviewed. Of 112 patients with herpes zoster ophthalmicus, 29 (26%) had HIV or AIDS. All these patients were younger than 50 years at the time of diagnosis. Five of 29 (17%) immunocompromised patients had acute retinal necrosis after herpes zoster ophthalmicus. No acute retinal necrosis was identified in the nonimmunocompromised patients after herpes zoster ophthalmicus. We recommend that all patients younger than 50 years who have herpes zoster ophthalmicus at initial examination be tested for HIV. Additionally, HIV-infected patients should be monitored closely after herpes zoster ophthalmicus for development of acute retinal necrosis. Long-term oral prophylactic as well as initial high-dose intravenous acyclovir may be appropriate in HIV-infected individuals with herpes zoster.

Recurrence of presumed varicella-zoster virus retinopathy in patients with acquired immunodeficiency syndrome

Five patients with acquired immunodeficiency syndrome (AIDS) and presumed varicella-zoster virus retinopathy had recurrence of retinopathy after stabilization with initial intravenous antiviral therapy. Recurrences were recognized as increased retinal opacification at the borders of preexisting lesions or as new lesions. In four of the five patients, recurrences were temporally associated with a reduction in the amount of antiviral medication being received. Changes included switch from intravenous to oral acyclovir (two patients), taper of oral acyclovir (one patient), and discontinuation of medications (one patient). In four patients disease was initially unilateral; in three of these four, disease subsequently developed in the previously unaffected fellow eye at the time of recurrence. The median time from stabilization of disease to recurrence was 51 days (range, 14 to 90 days). In contrast to the management of varicella-zoster virus retinopathy in immunocompetent patients and varicella-zoster virus lesions of the skin, varicella-zoster virus retinopathy in patients with AIDS appears to require chronic suppressive antiviral therapy to prevent recurrences. In this respect it is similar to other opportunistic retinal infections in patients with AIDS. The best drugs and optimal treatment regimens for maintenance antiviral therapy remain unknown.