Treatment of viral diseases of the cornea and external eye

Herpes Zoster Ophthalmicus Recurrence: Risk Factors and Long-Term Clinical Outcomes

PURPOSE

To examine the frequency of recurrences, risk factors, and long-term clinical outcomes in subjects with herpes zoster ophthalmicus (HZO).

DESIGN

Retrospective cohort study.

METHODS

All subjects with acute HZO seen at a single center from 2006 to 2016 were included in the study. The primary outcome measure was eye disease recurrence. The secondary outcome measure was moderate vision loss (≤20/50).

RESULTS

A total of 869 patients with acute HZO were identified, with a median follow-up time of 6.3 years (interquartile range 3.7-8.9 years). In all, 551 recurrences were observed, and at least 1 recurrence was seen in 200 subjects (23.0%), with uveitis (34.8%) being the most common. The median time to first recurrence was 3.5 months. Predictors of disease recurrence included immunosuppression (P = .026), higher presenting intraocular pressure (P = .001), corneal involvement (P = .001), and uveitis (P < .001) on multivariate analysis. Topical steroids were initiated in the first month of presentation in 437 subjects, and recurrence was observed in 184 (42.1%) of these subjects. Following cessation of topical steroid treatment, recurrence occurred after a median of 1.4 months (90% within 7 months). Moderate vision loss (≤20/50) occurred in 15.5%, 28.6%, 31.4%, 50.0%, and 57.4% of eyes with 0, 1, 2, 3, and 4 or more recurrences.

CONCLUSIONS

Recurrence of HZO eye disease is common, with an increased risk of vision loss with more recurrences. These findings indicate the need for close monitoring for potential recurrences, especially after cessation of topical steroid treatment, and in individuals with identified risk factors for recurrence.

Herpes simplex virus, varicella-zoster virus and cytomegalovirus keratitis: Facts for the clinician

Keratitis due to Herpes simplex virus (HSK), Varicella-Zoster virus (VZK) and Cytomegalovirus remains a frequent source of concern for many ophthalmologists. They are a frequent cause of emergency consultations at eye care centers and carry the risk of permanent loss of visual acuity or visual quality and/or chronic neurotrophic keratitis, resulting in a significant decrease in the quality of life. HSK and VZK can affect the corneal epithelium, stroma, or endothelium or a combination of layers. In contrast, most cases of CMV keratitis present as isolated endothelitis (CMVE), a clinical entity that has been described within the last 2 decades. These three types of viral keratitis are characterized by a high frequency of recurrences and each new episode increases the risk of sequelae. Hence, ophthalmologists must adapt the treatment to the clinical presentation of each recurrent episode in order to mitigate the immediate consequences of viral replication and the immune response on corneal transparency. In patients with frequent recurrences, preventive long-term antiviral treatment is strongly recommended. However, in some rare cases, continuous exposure to antivirals may promote the emergence of resistant viral strains, which can be difficult to manage. In the future, the introduction of new antiviral drugs, with differing modes of action compared to current medical therapy, could be an alternative until a truly effective preventive solution, such as a vaccine, is available.

Management of Adenoviral Keratoconjunctivitis: Challenges and Solutions

Human adenovirus (HAdV) is the most common cause of infectious conjunctivitis, accounting for up to 75% of all conjunctivitis cases and affecting people of all ages and demographics. In addition to ocular complications, it can cause systemic infections in the form of gastroenteritis, respiratory disease, and dissemination in immunocompromised individuals. HAdV causes lytic infection of the mucoepithelial cells of the conjunctiva and cornea, as well as latent infection of lymphoid and adenoid cells. Epidemic keratoconjunctivitis (EKC) is the most severe ocular manifestation of HAdV infection, in which the presence of subepithelial infiltrates (SEIs) in the cornea is a hallmark feature of corneal involvement. SEIs have the tendency to recur and may lead to long-term visual disability. HAdV persistence and dissemination are linked to sporadic outbreaks of adenoviral keratoconjunctivitis. There is no FDA-approved antiviral for treating adenoviral keratoconjunctivitis, and as such, solutions should be proffered to handle the challenges associated with viral persistence and dissemination. Several treatment modalities have been investigated, both systemically and locally, to not only mitigate symptoms but reduce the course of the infection and prevent the risk of long-term complications. These options include systemic and topical antivirals, in-office povidone-iodine irrigation (PVI), immunoglobulin-based therapy, anti-inflammatory therapy, and immunotherapy. More recently, combination PVI/dexamethasone ophthalmic formulations have shown favorable outcomes and were well tolerated in clinical trials for the treatment of EKC. Possible, future treatment considerations include sialic acid analogs, cold atmospheric plasma, N-chlorotaurine, and benzalkonium chloride. Continued investigation and evaluation of treatment are warranted to reduce the economic burden and potential long-term visual debilitation in affected patients. This review will focus on how persistence and dissemination of HAdV pose a significant challenge to the management of adenoviral keratoconjunctivitis. Furthermore, current and future trends in prophylactic and therapeutic modalities for adenoviral keratoconjunctivitis will be discussed.

Fabry keratopathy: manifestations and changes over time

AIMS

The goal was to find if changes in Fabry keratopathy were clinically observable over time. Also observed were variations of Fabry keratopathy, supplemental features, unique presentations and differences between keratopathies of right and left corneas and the same family and genotype.

METHODS

Biomicroscopic images of Fabry keratopathy in 10 persons with classic Fabry disease, 5 men and 5 women, were captured over an 18-month period. The keratopathies were categorised and scrutinised for changes over time, and differences between corneas of the same individual, family and genotype.

RESULTS

Fabry keratopathy ranged from mild change to marked change over 18 months. There was a great variety of whorl patterns. A few keratopathies were amorphous without vortices and many vortices were supplemented with amorphous features. All keratopathies were accompanied by diffuse epithelial haze. There was a range from negligible difference to marked difference between right and left eyes of the same individuals with similarities appearing as imprecise mirror images of each other. In some corneas, prominent vertical streams from the superior limbus integrated into the primary keratopathy. Comparisons between persons with the same family and genotype were obscured by gender and differences between right and left eyes.

CONCLUSIONS

Practitioners should be better able to detect Fabry disease having a fuller understanding of the variety of presentations of the dynamic, pathognomonic Fabry keratopathy. Routes of continuous centripetal renewal of corneal epithelium are spatially unique to each eye, in some cases subsidised by direct contribution of basal cells streamed from the superior limbus.

Allergy and Infections: Long-Term Improvement of Vernal Keratoconjunctivitis following Viral Conjunctivitis

PURPOSE

Vernal keratoconjunctivitis (VKC) is a severe, chronic allergic inflammatory disease of the ocular surface poorly responsive to antiallergic treatments and possibly leading to permanent visual impairment. VKC, because of mast cell, eosinophil, and Th2-type inflammation, polyclonal IgE activation, and tissue remodeling, is considered to be a typical Th2- driven disease. Viral infection stimulates a Th1 type immune response, potentially attenuating allergen-induced inflammation. The purpose of this report is to describe the effect of viral keratoconjunctivitis in a patient with VKC.

METHODS

The authors report on a patient with a severe form of VKC, poorly responsive to antiallergic treatments, who developed a viral keratoconjunctivitis. Signs, symptoms, and cytologic findings were recorded during the 5-year follow-up period.

RESULTS

The authors observed a prompt and permanent improvement of signs and symptoms of the allergic condition after the viral infection. Conjunctival scraping confirms that the inhibition of the eosinophilic inflammation lasts at least for 5 years.

CONCLUSIONS

In this case, the viral infection seemed to induce a clinical recovery of allergic disease, suggesting that an immune deviation induced by Th1-polarizing agents may revert an ongoing Th2 inflammation.

[Evaluating the effectiveness of Solanum tuberosum shoots extract in experimental ocular herpes]

Ocular herpes (OH) is an infectious disease caused by the herpes simplex virus (HSV) characterized by a variable clinical presentation and often accompanied by complications that may lead to deterioration of visual functions, cataract development, or even blindness. Its treatment is arduous. The aim of this work was to evaluate the effectiveness, tolerability, and safety of Panavir eye drops in a rabbit model of OH.

MATERIAL AND METHODS

Ocular infection was induced with HSV-1 (EU strain) in grey rabbits (all males, 2.5-3.0 kg) according to the standard technique. The treatment included Panavir-GLA (Panavir-gamma-linolenic acid) and Panavir medications.

RESULTS

Panavir eye drops instilled 6 times daily for 8 days showed a pronounced therapeutic effect and prevented the development of severe corneal opacities. The most rapid and significant results were seen in rabbits with epithelial keratitis and those with short-term persistence of the virus. Generally, the effectiveness of Panavir eye drops was comparable with that of the reference drug (Oftalmoferon). Panavir instillations caused no irritation, toxic and/or allergic effects and were well tolerated by the rabbits.

CONCLUSION

The data obtained suggest that Panavir eye drops may be included in OH treatment schemes.

Evaluation of the effects of acyclovir and/or human amniotic membrane on herpes virus culture and quantitative virus inactivity by real-time polymerase chain reaction

AIM

To investigate the permeability of amniotic membrane in herpes virus cell culture to acyclovir with real time polymerase chain reaction (RT-PCR).

METHODS

Madin-Darby Bovine Kidney (MDBK) cell culture and Bovine Herpes Virus (BHV1) type 1 were used in the study. Cell cultures were grouped into two on the basis of herpes virus inoculation. Each group was sub-grouped into three. Amniotic membrane (V-HAM), acyclovir (V-A), and amniotic membrane and acyclovir (V-HAM-A) were applied to these subgroup cultures, respectively. After the application of the membrane and the drug, the cultures were evaluated at 24 and 48h for cytopathic effect positive (CPE+) with a tissue culture microscope. In the CPE (+) samples, the DNA was extracted for viral DNA analysis by RT-PCR.

RESULTS

In control cultures without herpes virus CPE was not detected. Besides, amniotic membrane and acyclovir did not have cytotoxic effect on cell cultures. CPE were detected in Bovine Herpesvirus type-1 inoculated cell cultures after amniotic membrane and/or acyclovir application. DNA analysis with RT-PCR indicated that Cycle threshold (Ct) values were lower in the BHV1 and membrane applied group (amniotic membrane group < acyclovir group < membrane and acyclovir group). This showed that membrane did not have antiviral effect. The membrane and acyclovir cell culture groups with high Ct values indicated that membrane was permeable and had a low barrier effect to drug.

CONCLUSION

In our in-vitro study, we found that amniotic membrane, which can be used in the treatment of corneal diseases, did not have antiviral effect. Besides, we detected that amniotic membrane was permeable to acyclovir in BHV-1 inoculated MDBK cell culture. However, more studies are necessary to investigate the quantitative effects of amniotic membrane and acyclovir.

Ocular tropism of respiratory viruses

Respiratory viruses (including adenovirus, influenza virus, respiratory syncytial virus, coronavirus, and rhinovirus) cause a broad spectrum of disease in humans, ranging from mild influenza-like symptoms to acute respiratory failure. While species D adenoviruses and subtype H7 influenza viruses are known to possess an ocular tropism, documented human ocular disease has been reported following infection with all principal respiratory viruses. In this review, we describe the anatomical proximity and cellular receptor distribution between ocular and respiratory tissues. All major respiratory viruses and their association with human ocular disease are discussed. Research utilizing in vitro and in vivo models to study the ability of respiratory viruses to use the eye as a portal of entry as well as a primary site of virus replication is highlighted. Identification of shared receptor-binding preferences, host responses, and laboratory modeling protocols among these viruses provides a needed bridge between clinical and laboratory studies of virus tropism.

Colloidal dispersions for the delivery of acyclovir: a comparative study

This paper describes a comparative study on the performances of ethosomes and solid lipid nanoparticle as delivery systems for acyclovir. Ethosomes were spontaneously produced by dissolution of phosphatidylcholine and acyclovir in ethanol followed by addition of an aqueous buffer while solid lipid nanoparticle were produced by homogenization and ultrasonication. Both colloidal systems were morphologically characterized by cryo-transmission electron microscopy. The encapsulation efficiency was 94.2±2.8% for ethosomes and 53.2±0.2% for solid lipid nanoparticle. Concerning Z potential, both formulations are close to neutrality. The diffusion coefficients of the drug from ethosomes and solid lipid nanoparticle, determined by a Franz cell method, were 9.4 and 1.2-fold lower as compared to the free acyclovir in solution, thus evidencing the ability of both colloidal systems in enhancing the diffusion of the drug. The antiviral activity against HSV-1 of both systems was tested by plaque reduction assay in monolayer cultures of Vero cells. Data showed that no significant differences in the antiviral activity were observed by acyclovir in the free or loaded forms. Taken together these results, colloidal systems could be interesting to mediate the penetration of acyclovir within Vero cells.

The tug-of-war between dendritic cells and human chronic viruses

The human immune system is under constant challenge from many viruses, some of which the body is successfully able to clear. Other viruses have evolved to escape the host immune responses and thus persist, leading to the development of chronic diseases. Dendritic cells are professional antigen-presenting cells that play a major role in both innate and adaptive immunity against different pathogens. This review focuses on the interaction of different chronic viruses with dendritic cells and the viruses' ability to exploit this critical cell type to their advantage so as to establish persistence within the host.

Efficacy of a helicase-primase inhibitor in animal models of ocular herpes simplex virus type 1 infection

PURPOSE

The aim of this study was to evaluate the effect of BAY 57-1293, a helicase-primase inhibitor, on herpes simplex virus type 1 (HSV-1) reactivation in mice and its efficacy on established disease in rabbits.

METHODS

BALB/c mice latent for McKrae-strain HSV-1 were reactivated via heat stress, treated with BAY 57-1293, and their corneas were swabbed for virus or the trigeminal ganglia (TG) obtained for quantification of viral DNA. New Zealand white rabbits were infected and treated topically or orally in comparison with trifluridine or valacyclovir.

RESULTS

Oral BAY 57-1293 suppressed reactivation in HSV-1-infected mice and reduced the viral load in TG up to four orders of magnitude. In the rabbits, the therapeutic efficacies of topical BAY 57-1293 and trifluridine were similar. Once-daily oral BAY 57-1293 was significantly more effective than valacyclovir and as effective as twice a day topical trifluridine.

CONCLUSIONS

BAY 57-1293 may be more effective than valacyclovir, without the cytotoxicity or potential healing retardation seen with trifluridine. Oral BAY 57-1293 may be a substitute for eye drops as an effective treatment for herpetic keratitis and might be useful in treating stromal keratitis and iritis, as well as preventing recurrences of ocular herpes.

Efficacy of topical immunoglobulins against experimental adenoviral ocular infection

PURPOSE

Presently, there is no U.S. Federal Drug Administration (FDA)-approved antiviral therapy for the treatment of adenoviral (Ad) ocular infections. The goal of the present study was to determine the antiviral efficacy of human immunoglobulin (Ig), a preparation of highly purified and concentrated immunoglobulin (IgG) antibodies isolated from a large pool of human plasma donors, in vitro and on acute Ad replication in the Ad5 New Zealand White (NZW) rabbit ocular model.

METHODS

The antiviral activity of human Ig against multiple wild-type and human ocular isolates of adenovirus serotypes was investigated in vitro by using neutralizing assays in different human epithelial cell lines. In vivo bilateral topical ocular toxicity and antiviral efficacy were evaluated with established Ad5/NZW rabbit ocular models. In vivo Ig antiviral results were compared with those obtained with topical 0.5% cidofovir and saline.

RESULTS

In three different epithelial cell lines, <or=6.25 mg/mL of the Ig neutralized several wild-type adenoviral serotypes that cause ocular infections. A dose of <or=10 mg/mL neutralized 88% of ocular isolates of the adenovirus serotypes. After treatment of infected animals, adenovirus-positive cultures per total cultures (days 1-14; P = 0.021), the duration of Ad5 shedding, (P = 0.008), and the mean combined ocular viral titer during the early (days 1-5; P = 0.0001) and the late (days 7-14; P = 0.013) phases of infection were significantly lower in Ig-treated animals than in saline-treated animals and were similar to those in cidofovir-treated animals.

CONCLUSIONS

Ig demonstrated antiviral properties against multiple adenoviral serotypes in vitro and in the Ad5/NZW rabbit ocular model. Further studies are needed to advance topical immunoglobulin for treatment and prophylaxis of ocular infections.

A role for chromosomal protein HMGN1 in corneal maturation

Corneal differentiation and maturation are associated with major changes in the expression levels of numerous genes, including those coding for the chromatin-binding high-mobility group (HMG) proteins. Here we report that HMGN1, a nucleosome-binding protein that alters the structure and activity of chromatin, affects the development of the corneal epithelium in mice. The corneal epithelium of Hmgn1(-/-) mice is thin, has a reduced number of cells, is poorly stratified, is depleted of suprabasal wing cells, and its most superficial cell layer blisters. In mature Hmgn1(-/-)mice, the basal cells retain the ovoid shape of immature cells, and rest directly on the basal membrane which is disorganized. Gene expression was modified in Hmgn1(-/-) corneas: glutathione-S-transferase (GST)alpha 4 and GST omega 1, epithelial layer-specific markers, were selectively reduced while E-cadherin and alpha-, beta-, and gamma-catenin, components of adherens junctions, were increased. Immunofluorescence analysis reveals a complete co-localization of HMGN1 and p 63 in small clusters of basal corneal epithelial cells of wild-type mice, and an absence of p 63 expressing cells in the central region of the Hmgn1(-/-) cornea. We suggest that interaction of HMGN1 with chromatin modulates the fidelity of gene expression and affects corneal development and maturation.

Agents and strategies in development for improved management of herpes simplex virus infection and disease

The quiet pandemic of herpes simplex virus (HSV) infections has plagued humanity since ancient times, causing mucocutaneous infection such as herpes labialis and herpes genitalis. Disease symptoms often interfere with every-day activities and occasionally HSV infections are the cause of life-threatening or sight-impairing disease, especially in neonates and the immuno-compromised patient population. After infection the virus persists for life in neurons of the host in a latent form, periodically reactivating and often resulting in significant psychosocial distress for the patient. Currently no cure is available. So far, vaccines, ILs, IFNs, therapeutic proteins, antibodies, immunomodulators and small-molecule drugs with specific or non-specific modes of action lacked either efficacy or the required safety profile to replace the nucleosidic drugs acyclovir, valacyclovir, penciclovir and famciclovir as the first choice of treatment. The recently discovered inhibitors of the HSV helicase-primase are the most potent development candidates today. These antiviral agents act by a novel mechanism of action and display low resistance rates in vitro and superior efficacy in animal models. This review summarises the current therapeutic options, discusses the potential of preclinical or investigational drugs and provides an up-to-date interpretation of the challenge to establish novel treatments for herpes simplex disease.

Synthesis of novel substituted 2-phenylpyrazolopyridines with potent activity against herpesviruses

Herpesviruses are a significant source of human disease; amongst these herpes simplex virus 1 (HSV-1) and HSV-2 are very prevalent and cause recurrent infections. We recently identified a pyrazolo[1,5-a]pyridine scaffold that showed promising activity against HSV-1 and HSV-2 in Vero cell antiviral assays. Here, we describe the synthesis and anti-herpetic activity of several 3-pyrimidinyl-2-phenylpyrazolo[1,5-a]pyridines with differing 2-phenyl substitution patterns. Approaches to rapidly access a number of analogs with different 2-phenyl substitution patterns are outlined. Several of the compounds described have comparable activity to acyclovir against HSV-1 and HSV-2.

Tolerability and Efficacy of N-Chlorotaurine in Epidemic Keratoconjunctivitis—a Double-Blind, Randomized, Phase-2 Clinical Trial

The aim of this study was to assess the tolerability and efficacy of N-chlorotaurine (NCT), an endogenous antimicrobial agent, in epidemic keratoconjunctivitis. In a prospective double-blind, randomized phase 2b study, the infected eyes were treated for 7 days with eye drops containing 1% aqueous solution of N-chlorotaurine (33 subjects) or gentamicin (27 subjects, control group). Adenovirus types 3, 4, 8, 19, and 37 were detected in 39 subjects (65%), enteroviruses in 8 (13.3%), and staphylococci in 5 (8.3%). Subjective and objective symptoms were scaled and added to a subjective and objective score, respectively, on day 1 (baseline), day 4, and day 8. Analyzing the whole study population, the subjective score on day 8 was lower in the NCT group (P = 0.016), whereas there were no differences in the objective score. However, in severe infections caused by adenovirus type 8 (n = 20) both the subjective and objective score were lower in the NCT group on day 4 (P = 0.003 and 0.015, respectively), which was also true for the subjective score on day 8 (P = 0.004) in this subgroup. The frequency of subepithelial infiltrates was similar in both groups. N-chlorotaurine was well-tolerated, shortened the duration of illness, and seems to be a useful causative therapeutic approach in severe epidemic keratoconjunctivitis.

[The latest in herpes simplex keratitis therapy]

Herpetic keratitis is characterized by spontaneous recurrences and a risk of vision loss, the latter being more serious when relapses are frequent and severe. Two clinical forms are commonly distinguished: epithelial keratitis, usually quickly resolved with topical antivirals, and stromal keratitis, which has a slower progression, even when both steroids and antivirals are used. Great strides have been made during the last 20 Years in the therapy of herpes keratitis, which is now considered and treated as a chronic disease. Randomized controlled studies definitively showed the decrease in spontaneous herpetic ocular events in patients treated with long-term oral acyclovir. The effectiveness of preventive treatment has also been shown during high-risk periods, especially ocular surgery, in patients with a history of herpes keratitis. However, the optimal duration and dosage of antiviral prevention have yet to be defined. We can also hope that in the future novel antiviral strategies such as vaccination will reduce the place of herpes keratitis as an indication for corneal graft.

Comparison of Liposome-Encapsulated Acyclovir with Acyclovir Ointment: Ocular Pharmacokinetics in Rabbits

A positively charged liposomal formulation for topical administration of acyclovir (ACV) was investigated in comparison with a commercial ACV ointment, by determining the pharmacokinetic profile of the drug in the aqueous humor of rabbits after topical administration. The ointment was tested at two different strengths: undiluted (3.0%) and diluted to the same ACV concentration as the liposomal vehicle (0.12%). A liquid formulation containing ACV plus "empty" liposomes and an isotonic aqueous ACV solution were also tested. The applied ACV dose was 0.18 mg, except for the full-strength (3.0%) ointment, in which case it was 1.5 mg. The ACV liposomal dispersion (LIPO-ACV) produced a significantly higher drug concentration profile in the aqueous with respect the three reference formulations containing the same ACV concentration, and showed a 90-minute plateau. The aqueous humor ACV concentration maintained by LIPO-ACV during the plateau was in the upper range of the ID(50)s (0.01 to 0.7 microg/mL) reported for Herpes simplex type 1. In spite of the much higher dose (1.5 versus 0.18 mg), the area under curve (AUC) produced by the full-strength 3.0% ointment was only 1.6 times greater than that corresponding to the liposomal vehicle. In vitro release tests through a cellophane membrane substantiated the concept that positively charged liposomal formulations owe their efficacy to interactions with the positively charged corneal epithelium.

Development of genetically engineered tet HPV16-E6/E7 transduced human corneal epithelial clones having tight regulation of proliferation and normal differentiation

Lack of an optimal in vitro model of human corneal epithelial (HCE) cells is a major limitation in studying normal functions and gene regulations in HCE. Moreover, availability of a multi-layered HCE culture can reduce the usage of animals in the toxicity testing of consumer products. We have developed tetracycline-responsive human papilloma virus (HPV) 16-E6/E7 transduced HCE clones showing tight regulation of proliferation and normal differentiation. Expression of HPV16-E6/E7 mRNA and HPV16-E7 and keratin K3 proteins was examined by RNase protection assay and western blotting, respectively, in presence and absence (+/-) of Dox in identified clones. Localization of cornea-specific keratin k3 in +/- of Dox was evaluated by immunocytochemistry. The response of growth factors such as hepatocyte growth factor (HGF) and epidermal growth factor to the cellular proliferation in +/- of Dox in the newly identified clones was measured by cell counting. Cellular morphology, formation of multi-layered cultures at air-liquid interface and ultrastructural features were evaluated by light and transmission electron microscopy. The physical barrier established by the newly developed clones was determined by the transepithelial permeability to sodium fluorescein and transepithelial electrical resistance assays in the airlifted-stratified cultures.

Pathogenesis and potential antiviral therapy of complications of smallpox vaccination

Vaccination against smallpox may result in a variety of complications, ranging in severity from benign to lethal. Universal vaccination was halted in the US in 1972, so almost half the present population has never been vaccinated. Because side effects occur most often in first-time vaccinees, current plans for rapid large-scale vaccination in the event of bioterrorist attack raise concerns about the occurrence of a large number of adverse events. Most complications result from the excessive replication of vaccinia virus, making them potential targets for antiviral therapy. Effective treatment is especially needed for persons with atopic dermatitis or eczema, who are unusually susceptible to the initiation and spread of vaccinia infection because of defects of innate immunity in the skin, and for individuals with defective cell-mediated immunity, who are unable to eliminate vaccinia infection once it has begun. In the past, many complications were treated with vaccinia immune globulin (VIG) and/or the antiviral drug methisazone, but neither was tested in placebo-controlled trials. New antiviral drugs are now available, but have not yet been evaluated for treating vaccinia infections in humans. Both laboratory research and clinical studies are needed to help prevent serious complications in any major vaccination campaign.

Novel agents and strategies to treat herpes simplex virus infections

The quiet pandemic of herpes simplex virus (HSV) infection has plagued humanity since ancient times, causing mucocutaneous infection, such as herpes labialis and herpes genitalis. Disease symptoms often interfere with everyday activities and occasionally HSV infections are the cause of life-threatening or sight-impairing disease, especially in neonates and the immunocompromised patient population. After primary or initial infection the virus persists for life in a latent form in neurons of the host, periodically reactivating and often resulting in significant psychosocial distress for the patient. Currently, no cure is available. In the mid-1950s the first antiviral, idoxuridine, was developed for topical treatment of herpes disease and, in 1978, vidarabine was licensed for systemic use to treat HSV encephalitis. Acyclovir (Zovirax), a potent, specific and tolerable nucleosidic inhibitor of the herpes DNA polymerase, was a milestone in the development of antiviral drugs in the late 1970s. In the mid-1990s, when acyclovir became a generic drug, valacyclovir (Valtrex) and famciclovir (Famvir), prodrugs of the gold standard and penciclovir (Denavir), Vectavir), a close analogue, were launched. Though numerous approaches and strategies were tested and considerable effort was expended in the search of the next generation of an antiherpetic therapy, it proved difficult to outperform acyclovir. Notable in this regard was the award of a Nobel Prize in 1988 for the elucidation of mechanistic principles which resulted in the development of new drugs such as acyclovir. Vaccines, interleukins, interferons, therapeutic proteins, antibodies, immunomodulators and small-molecule drugs with specific or nonspecific modes of action lacked either efficacy or the required safety profile to replace the nucleosidic drugs acyclovir, valacyclovir, penciclovir and famciclovir as the first choice of treatment. Recently though, new inhibitors of the HSV helicase-primase with potent in vitro antiherpes activity, novel mechanisms of action, low resistance rates and superior efficacy against HSV in animal models have been discovered. This review summarises the current therapeutic options, discusses the potential of preclinical or investigational drugs and provides an up-to-date interpretation of the challenge to establish novel treatments for herpes simplex disease.

The management of the red eye for the generalist

Patients often present to primary care physicians with acute or chronic red eyes. Benign conditions may be evaluated and treated by primary care practitioners. Red eyes due to serious conditions may be vision threatening and require early detection and referral.

Acyclovir-resistant bilateral keratitis associated with mutations in the HSV-1 thymidine kinase gene

PURPOSE

To evaluate the contribution of molecular methods for the diagnosis of an acyclovir-resistant HSV-1 bilateral keratitis in an AIDS patient and to report a new point mutation in the nucleotide sequence of the thymidine kinase (tk) gene involved.

METHODS

A 31 year old HIV-positive female presented with severe, active, bilateral and sight-threatening keratitis of 6 months duration, which was treated unsuccessfully with acyclovir. After corneal biopsy, samples were analysed by standard virological procedures, in situ hybridization, and PCR. The tk gene was cloned and subsequently sequenced.

RESULTS

Conventional virological methods remained inconclusive. However, in situ hybridization and PCR rapidly confirmed the diagnosis of HSV-1 keratitis. The tk gene sequence revealed the presence of five variations previously described in two reference strains, but also a new point mutation at nucleotide position 431 which leads to an amino-acid change at position 144 that supported the hypothesis of a putatively altered functional form of the enzyme. Intravenous foscarnet treatment in an induction regimen was effective and cicatrization occurred within 3 weeks.

CONCLUSIONS

PCR and in situ hybridization are effective and powerful techniques when other virological procedures are non-contributive, particularly in immunocompromised patients previously treated with antiviral drugs. The new point mutation identified in the tk gene may be associated with resistance to acyclovir.