Feline herpes virus infection

Ten cases of naturally occurring dendritic keratitis (feline herpes keratitis), which are manifestations of the disease commonly known as feline viral rhinotracheitis, have been identified in domestic cats in San Fancisco. Neonatal, juvenile, and adult forms of the disease are described and their treatment is discussed.

[Herpes therapy and prophylaxis. I. A critical review (author's transl)]

This critical review is based upon controlled experimental and clinical data. Dendritic keratitis initially should be treated by debridement of the diseased epithelium followed by antiviral medication. The advantages and disadvantages of different debridement techniques and different synthetic antivirals are discussed. Rational treatment of other forms of herpetic eye disease with antivirals, steroids, therapeutic soft lenses, collagenase inhibitors etc. necessitates first of all an exact diagnosis (disciform edema, interstitial herpetic keratitis, herpetic (kerato-)uveitis, metaherpetic erosion, metaherpetic ulcer). Therapeutic or prophylactic measures which as yet have found no valid experimental or clinical basis are discussed as well as further developments. Special interest is laid upon the application of human interferon.

Vidarabine therapy of simple and IDU-complicated herpetic keratitis

Large scale, multiclinic evaluations of vidarabine (Ara-A, Vira A, adenine arabinoside) for treating herpetic keratitis have been conducted as double-blind studies (169 patients) in comparison with IDU and open studies (146 patients). In the open studies, the disease in the majority of patients had been refractory to IDU. The effects of vidarabine and IDU were approximately the same in improvement of symptoms (lacrimination, photophobia, sensitivity) and percent of and time for corneal reepithelialization. With vidarabine, significantly more patients had improved distant visual acuity than did with IDU. In the open studies, vidarabine also was effective. Of 116 patients whose ulcers had not responded to IDU, 91 (78%) had reepithelialization within four weeks of treatment with vidarabine. On the basis of results from these studies, vidarabine appears to be a safe and effective drug for treating herpes simplex keratitis.

The management of ocular herpesvirus infections

The many treatment methods in current use for every known complaint only seem to aggravate the difficulty of treating ocular herpes simplex virus (HSV) infections, which are generally self-limited in the immunocompetent host. The cornea is already a somewhat immune-deficient tissue since its lack of blood vessels separates it partially from the host, and treatment with glucocorticoids, which are immunosuppressive, increases the risk of damaging complications such as scarring, prolonged morbidity, bacterial or fungal superinfection, and the occasional corenal perforation. Accepted methods of treatment of specific lesions, are discussed, as are some methods that are not yet accepted, but which seem promising. Herpes zoster may result in scarring and significant loss of vision even without the use of glucocorticoids, the disease often manifesting itself in the already compromised host. The major complication is postherpetic neuralgia. None of the available treatment methods has been fully satisfactory, and every effort should be made to prevent eye lesions in patients with early infection of the ophthalmic branch of the trigeminal nerve. Stimulation of cellular immunity by various means appears to offer some new promise for control of the disease. Management of varicella, cytomegalovirus, and infectious mononucleosis are also discussed.

Historical observations on herpetic keratitis

The history of herpetic keratitis is presented. The similarities and differences between dendritic keratitis and herpes labialis are enumerated, with the suggestion that the similarities (in onset, pathology, and clinical course) far outweigh the differences. The principal difference seems to be that the avascalarity of the cornea retards the immunologic responses. Important points in the history of herpetic keratitis include (1) the close association of herpetic disease with malaria around the turn of the century; (2) the relatively benign nature of the disease, in contrast to herpes zoster keratitis; (3) the unfavorable response of the disease to immunosuppressive measures and diseases; (4) the failure of chemotherapy to influence favorably the natural history of the disease; and (5) the increasing visual damage caused by the disease since 1952 when corticosteroids were introduced into ocular therapy. Mention is made of the increasing problem of venereal herpes, with resultant neonatal herpetic keratitis, retinitis, and encephalitis.

Treatment of vaccinial keratitis with vidarabine

Vaccinial epithelial keratitis was produced in rabbits. When the therapeutic effect of vidarabine on the experimentally-induced disease was evaluated and compared to the effect of idoxuridine, vidarabine was found to be highly effective, substantially more effective than idoxuridine, and nontoxic to the eye.

The need for antiviral therapy and prophylaxis of viral ocular disease

The cost of development of a compound with clinical potential as an antiviral agent is so great that it cannot be undertaken unless there is likely to be a market that will return the investment. The current practice, assessment of the prospect on the basis of the present market for idoxuridine and calculation of a likely percentage of capture by a potentially superior compound, is basically erroneous and may lead to gross underestimates of the market. In addition to the market for agents effective in treatment of dendritic and amoeboid ulcers, there is a potentially much greater market, first, for somewhat less toxic compounds that may be used more or less continuously over very long periods for prevention of recurrences. Substances with promise of filling each of these requirements are already under investigation. There is also a potential market for therapeutic preparations with activities against a range of agents, particularly herpesviruses, adenoviruses, and chlamydiae, that commonly cause follicular conjunctivitis or keratoconjunctivitis.

Advantages and limitations of animal models in the evaluation of antiviral substances

Since many antiviral substances with potential for use in humans are in various phases of evaluation, criteria must be developed for selection of those compoinds with the greatest probability of efficacy and least toxicity. We lack background experience in evaluation of antivirals to permit extrapolation from in vitro tests to use in humans; it is of critical importance, therefore, to develop animal models for evaluation of antiviral substances before trials in humans and to establish guidelines for the relative predictive reliability of in vitro screening and evaluation in animal models. The complexity of drug-host and virus-host interaction and other factors may limit the predictive value of some or all experimental systems. Although the use of animal models is an important phase in the evaluation of antiviral chemotherapeutic agents, the models must be carefully studied and the interaction of drug and virus in the experimental animal specifically defined if optimal guidelines for the predictive value of model systems are to be developed. These guidelines must then be modified as experience is gained with antiviral substances that reach human trials.

Ocular antiviral therapy in perspective

The eye presents a unique model for the study of the pathogenesis of viral disease, drugs, and local and general host factors. Disease is easily observed and quantitated, and the presence of two organs sometimes permits controlled observations that are otherwise impossible. Perhaps most important, ocular viral infection is disabling and blinding, and the success of its treatment with antiviral drugs has clearly demonstrated the potential for the use of antiviral drugs in other areas.

Treatment of infections due to Herpesvirus in humans: a critical review of the state of the art

Results of experimental trials with antiviral agents in humans have varied from encouraging to controversial to negative, usually as a result of the difficulty in defining the true therapeutic index (ratio of efficacy to toxicity) of toxic drugs for the treatment of diseases that are potentially severely debilitating or lethal. Reasons for current difficulties relate mainly to inadequacies of preclinical studies and the lack of appropriate controls. The inadequacies include poor definition of the effect of drugs or viruses on cellular metabolism, incomplete pharmacologic studies in animals or humans, and, because of the latter, inappropriate animal models. In human trials, historical data have often been used instead of true controls because of the presumed severity of candidate diseases. Use of such data led to a false impression of drug efficacy, an impression later refuted when proper control studies demonstrated that the range of disease was much greater than had been previously supposed. Data bearing on these points for the most commonly employed experimental compounds (cytosine arabinoside, adenine arabinoside, and 5-iodo-2'-deoxyuridine) are contrasted to highlight difficulties as well as to provide perspectives for antiviral chemotherapy of herpesvirus infections.

An assessment of methods of treating viral warts by comparative treatment trials based on a standard design

A series of eleven comparative wart treatment trials undertaken between 1969 and 1975 and involving 1802 patients is described. A method of coding provided groups of patients matched for age, type, number and duration of warts, within which treatments could be randomized. The variation in response to treatment was shown to be influenced significantly by these factors and the level of cure to depend on the proportions of the various response groups within the population under consideration. These proportions were found to vary geographically and at different periods. In all the trials the results were assessed at 12 weeks. In the treatment of hand warts, the percentage cure of patients treated with liquid nitrogen fell significantly from 75 to 40% when the interval between freezings was increased from 3 to 4 weeks. The average number of freezings required for a cure was 3-1 amongst all patients cured by 6 or less freezings at intervals of 2 or 3 weeks. In a two-centre trial there was no significant difference between the percentage cure of patients with hand warts treated with liquid nitrogen (69%) and of those applying a paint containing salicylic and lactic acids (SAL) (67%). Patients receiving both treatments concurrently did better (78%) but the difference was not found to be statistically significant. In the treatment of simple plantar warts the percentage cure for the SAL paint (84%) was found to compare favourably with that for a podophyllin treatment (81%). Only one of the patients cured by the paint in that trial was found to have had a recurrence after 6 months. The paint was found to be satisfactory for use under general practice conditions. Additions to the formula did not alter its effectiveness. In the treatment of mosaic plantar warts the overall percentage cure for the SAL paint in a series of comparative trials (1969-75) was 45%. In these trials it was compared directly with one or more other preparations. No differences were found between its efficacy and that of 10% buffered gluteraldehyde (47%), 40% benzalkonium chloride dibromide (Callusolve 40) (30%) and 5% 5-fluorouracil in dimethyl sulphoxide (53%). Only 25% of thirty-six patients treated with 5% idoxuridine in dimethylsulphoxide were cured. Throughout the trials approximately 30% of patients with hand warts, 20% of those with simple plantar warts and 50% of those with mosaic plantar warts were found to be resistant to treatment. The adoption of treatment with SAL paint for hand warts and simple plantar warts by the general practitioners in the Edinburgh area has proved satisfactory. Only resistant cases are now referred to hospital and these can be treated within a few weeks instead of 4-5 months as was the case in 1969.

Cold sores-an epidemiological survey

A survey was carried out in a general practice in North Wales to determine the incidence, frequency, duration, and severity of cold sores. Of the 1,855 adults interviewed, 46 per cent gave a definite history of having had a cold sore at some time while 28 per cent continued to have one or more a year. More than half of the latter considered their sores of moderate or severe inconvenience.

Herpes encephalitis. Rapid diagnosis and treatment with antiviral drugs

The use of specific IgM antibodies and direct electron-microscopic examination of brain biopsies or vesicle fluid was tested as means of raped diagnosis in 6 cases of herpes simplex encephalitis seen consecutively in Montreal. In 2 of 3 biopsies herpes viruses were seen by negative staining of a cell extract within 1 hr. In the negative case, the biopsy was done almost 1 month after onset. In 2 additional cases herpes virus particles were found directly in the fluid of isolated vesicles. In the last 2 cases, who survived, the diagnosis of herpes encephalitis rested upon the demonstration of a greater than 4-fold rise in complement fixing herpes simplex virus antibodies in convalescent sera and upon the appearance late in the course of the encephalitis of specific antibodies in the cerebrospinal fluid. The early appearance of specific IgM antibodies contributed to the diagnosis in 4 of the 6 cases. Antiviral therapy was attempted in alternate cases (3 cases) but was not successful. Brain biopsy is rarely performed for diagnostic purposes but when prompt antiviral therapy is contemplated, the examination of the biopsy material for herpes virus particles by electron microscopy in negative staining and thin sections can rapidly and reliably confirm the diagnosis.

Evaluation of 6-azauridine and 5-iododeoxyuridine in the treatment of experimental viral infections

The potential antiviral activity of 6-azauridine and 5-iododeoxyuridine was evaluated in a coordinated study at five institutions. Experimental models in five species, the mouse, rabbit, swine, cat, and ferret, were established with use of 10 viruses: Herpesvirus hominis types 1 and 2, murine cytomegalovirus, vaccinia virus, Shope fibroma virus, transmissible gastroenteritis virus, swine influenza virus, feline viral rhinotracheitis virus, feline panleukopenia virus, and ferret distemper virus. Criteria for selection were: (1) representation from a number of major groups of viruses, (2) reproduction of natural routes of infection, and (3) simulation of potentially treatable viral infections of man. Antiviral activity was observed for 5-iododeoxyuridine in H. hominis infections in hairless mice and influenza in swine, and a slight degree of efficacy was noted in rabbits infected with Shope fibroma virus. Toxicity was also observed in most of the experimental models. There was a suggestion of antiviral activity with 6-azauridine in swine infected with transmissible gastroenteritis virus; however, enhancement of disease and some toxicity were seen in most of the other models. Efficacy of these two compounds was not well substantiated by these studies.

Herpes simplex virus types 1 and 2: therapeutic response to antiviral drugs

In vitro studies have demonstrated a relative resistance of herpes simplex virus type 2 to antiviral therapy when compared with herpes simplex virus type 1. The in vivo studies, however, show an excellent therapeutic response to both antiviral drugs in experimentally induced viral keratoconjunctivitis.

Intranasal challenge of mice with herpes simplex virus: an experimental model for evaluation of the efficacy of antiviral drugs

An experimental model of herpetic infection based on intranasal challenge of 12-day-old mice with herpes simplex virus (type 1) has been developed for assessment of the efficacy of a variety of antiviral compounds with clinical potential: cytosine arabinoside, adenine arabinoside, iododeoxyuridine, ribavirin, chloriteoxidized oxyamylose, polyriboinosinic-polyribocytidylic acid, and interferon. The model employed is reminiscent of herpetic encephalitis in humans in both the portal of entry (nasopharyngeal cavity) and the mode of transmission (nerve route) of the virus to the target organ (brain). The mortality rate from viral infection was significantly reduced (greater than or equal to 30%) by the following treatment regimens: cytosine arabinoside, adenine arabinoside, iododeoxyuridine, and ribavirin, administered daily for seven consecutive days starting immediately after inoculation of virus, at dosage levels of 4-20 mg/kg, 20-100mg/kg, 100mg/kg, and 20-100 mg/kg, respectively; and chlorite-oxidized oxyamylose, polyriboinosinic-polyribocytidylic acid, and mouse interferon, administered 24 hr before viral challenge, as single doses of 100-500 mg/kg, 20mg/kg, and 10(7)-10(8) international reference units/kg respectively. Similar doses of polyriboinosinic-polyribocytidylic acid and mouse interferon administered after inoculation of virus did not alter the final mortality rate.

Clinical trials of topical interferon therapy of ulcerative viral keratitis

An open trial suggested that monkey interferon had a therapeutic effect on ulcerative vaccinial keratitis in humans. A randomized, double-blind, placebo-controlled trial of either monkey interferon or drops of idoxuridine (given hourly by day and at 2-hr intervals by night for three days) suggested a therapeutic effect from idoxuridine but not from monkey interferon. Results of experiments with rabbits suggested that a daily application of human interferon (1.1 X 10(7) international units/ml) would be effective in the prevention of herpetic ulcers but might not affect established lesions. Preliminary results are encouraging in a placebo-controlled, randomized trial of human interferon given once daily for seven days for prevention of recrudescence of epithelial herpetic lesions after minimal wiping debridement with a cotton-tipped swab. The design of the trial is closely analogous to that of the experiments with rabbits and permits ethically acceptable, placebo-controlled trials of antiviral agents.

[Herpes simplex encephalitis in newborns. Treatment with 5-iodo-2'-deoxyuridin? (author's transl)]

Premature twins both affected with generalized herpes simplex infection including CNS involvement were treated with 5-Iodo-2'-deoxyuridin (IDU). Therapy was started 6 days and 5 days, respectively, after appearance of the first symptoms. Nevertheless both babies died, twin A at the age of 24 and twin B at the age of 28 days. Herpes virus was cultured from all organs in twin A. The literature shows a decrease in mortality in children treated with IDU for herpes simplex encephalitis. The percentage of survivors with ultimate severe CNS damage, however, is very high and remains in treated or untreated patients the same. The institution of IDU therapy in neonates with manifest HSV encephalitis is therefore not unequivocally justified.