Comparison of activity of herpes virus inhibitors

Activity of 1-(2'-fluoro-2'-deoxy-beta-D-arabinofuranosyl)thymine against herpes simplex virus in cell cultures and rabbit eyes

A new antiviral compound 1-(2'-fluoro-2'-deoxy-beta-D-arabinofuranosyl)thymine (2'-fluoro-5-methyl-ara-uracil [FMAU]), was compared with acyclovir and idoxuridine in vitro against two strains of both herpes simplex virus type 1 (HSV-1) and HSV-2. Determinations of the 50% effective dose varied slightly with each strain and with the host cells employed. The 50% effective dose for FMAU and acyclovir against HSV-1 ranged from 0.1 microM to 0.5 to 0.6 microM in rabbit kidney cells and from 0.5 microM to 0.6 to 0.78 microM in Vero cells. Beginning 4 days post-inoculation, topical FMAU therapy given five times per day to rabbits with acute herpetic keratitis either suppressed or delayed the severity of corneal epithelial involvement, conjunctivitis, iritis, and corneal clouding. Responses to treatment with FMAU were similar to those obtained with acyclovir and significantly better than those attained with idoxuridine and vidarabine. At 30 to 40 days after the end of treatment, rabbit eyes were subjected to iontophoresis with epinephrine in an attempt to induce reactivation and enhance detection of previously latent HSV-1. Latent HSV-1 was detected in 67 to 92% of trigeminal ganglia in FMAU-treated animals and in 90% of placebo-treated animals.

Prophylactic studies against herpes infections in severely immunocompromised patients with acyclovir

A total of 59 patients, including 20 undergoing bone marrow transplantation (BMT) and 39 who were receiving cytotoxic chemotherapy (CT), were included in a placebo-controlled trial of intravenous acyclovir as a prophylactic against herpes simplex virus infections. Fifty per cent of the patients (both BMT and CT) receiving placebo developed herpes simplex virus infections; in those receiving acyclovir, none of the BMT group and 10 per cent of the CT group became infected with herpes simplex. Prevention of herpes infections in the immunosuppressed is clearly both desirable and, in the case of herpes simplex virus, attainable.

Acyclovir treatment of experimental herpetic keratitis in the rabbit eye

In the rabbit eye model of experimental herpetic keratitis a satisfactory cure was obtained with ointments containing 1 percent, 2 percent, and 3 percent acyclovir, and also with idoxuridine. Trifluorothymidine and vidarabine were less effective in the particular conditions of the experiment. A cure was also obtained with acyclovir sodium salt injected intravenously, thus demonstrating that a local infection of the eye can be treated systematically.

Trifluridine: a review of its antiviral activity and therapeutic use in the topical treatment of viral eye infections

Trifluridine (trifluorothymidine) is an antiviral agent for topical use in the eye, and is structurally related to idoxuridine. In vitro studies have shown that it effectively inhibits the replication of herpes simplex virus type 1, which causes primary keratoconjunctivitis and recurrent epithelial keratitis in man. In masked comparative studies, predominantly in patients with dendritic ulcers, trifluridine 1% solution was effective in over 90% of patients; in such studies it was comparable with vidarabine in treating dendritic ulcers, and was at least as effective as, and in some studies more effective than, idoxuridine. The drug was also effective in treating a small number of patients with geographic ulcers (sometimes associated with the usage of topical corticosteroids), and this could be an important advantage if confirmed in further well-designed studies. However, experience at present is too limited to reliably determine the usual response rate in this difficult therapeutic area. In open studies the drug proved to be particularly useful in treating ulcers previously unresponsive to idoxuridine or vidarabine, and in treating patients intolerant of idoxuridine, with a high success rate and minimal side effects being reported. The role of trifluridine in treating deep stromal disease, uveitis, or adenovirus kerato-conjunctivitis has not been established. The drug is well tolerated and cross-hypersensitivity and cross-toxicity between trifluridine, idoxuridine and vidarabine are rare. Thus, trifluridine is an effective alternative to the drugs available for treating herpetic keratitis, and seems especially useful in 'difficult' cases.

Rapid assay of herpes simplex virus sensitivity to drugs

A 16 h immunofluorescence microplaque reduction assay for herpes simplex virus (HSV) was compared with a plaque reduction assay to assess its feasibility as a rapid technique for determining viral sensitivity to drugs. A drug-sensitive HSV strain (HSV-1 Patton) and a drug resistant strain (HSV-1-P-ACG-R), both grown in cell cultures, were compared against serial dilutions of adenine arabinoside (Ara-A) and acycloguanosine (ACG). Similar studies were done with virus obtained directly from experimentally infected rabbit corneas. The microplaque assay yielded results similar to the plaque assay and has the advantage of speed, which may be useful in clinical situations.

Inhibition of cellular alpha and virally induced deoxyribonucleic acid polymerases by the triphosphate of acyclovir

The effect of the triphosphate of 9-(2-hydroxyethoxymethyl)guanine (acyclovir, acycloguanosine) on cellular alpha deoxyribonucleic acid (DNA) polymerases (DNA nucleotidyltransferases), DNA polymerases of several members of the herpes group, vaccinia virus DNA polymerase, and Friend leukemia virus ribonucleic acid-dependent DNA polymerase was examined. Several viruses, which were found to be susceptible to acyclovir, were found to induce DNA polymerases which were sensitive to acyclovir triphosphate (acyclo-GTP). Human cytomegalovirus and the H29R strain of herpes simplex virus type 1, however, were found to be relatively insusceptible to acyclovir, even though their induced DNA polymerases were inhibited by low concentrations of acyclo-GTP. The amount of acyclovir anabolized to acyclo-GTP was significantly lower for human cytomegalovirus and H29R than for the more susceptible viruses. Vaccinia virus and Friend leukemia virus induced DNA polymerases which were insensitive to inhibition by low concentrations of acyclo-GTP, anabolized little acyclovir to acyclo-GTP, and were found to be insensitive to inhibition by acyclovir. Uninfected WI-38 cells were not susceptible to inhibition by acyclovir, anabolized little acyclovir to acyclo-GTP, and had an alpha DNA polymerase which was insensitive to inhibition by low concentrations of acyclo-GTP.

Ineffectiveness of adenine arabinoside and adenine arabinoside 5'-monophosphate in simian varicella infection

Adenine arabinoside and adenine arabinoside 5'-monophosphate (ara-AMP) have been evaluated for antiviral activity against simian varicella virus infection in monkeys. In a preliminary study for toxicity, intramuscular injection of ara-AMP at 15 mg/kg per day as a single injection for 5 days to two normal patas monkeys caused no detectable local reaction, no weight loss or changes in serum transaminase levels, and no hematological abnormalities. When this dose was given in the treatment of four simian varicella virus-infected patas monkeys, no effect was observed on the clinical course of infection, as compared with four infected monkeys which received phosphate-buffered saline. Treatment was begun 43 h after virus inoculation and was continued for 16 days. Toxicity of intravenously administered ara-AMP at 100 to 50 mg/kg per day for 5 days to pairs of uninfected patas monkeys was evident by hematological and hepatic histological alterations, as well as the death of one monkey in each pair. No gross evidence of toxicity occurred in two monkeys which received 20 mg of ara-AMP per kg per day. The antiviral efficacy of intravenous treatment was studied in groups of four African green monkeys which received adenine arabinoside at 15 mg/kg per day or ara-AMP at 18.4 mg/kg per day. Drug administration began 48 h after inoculation with simian varicella virus and continued for 10 days. The monkeys that received treatment did not respond to infection differently from four infected control monkeys similarly treated with phosphate-buffered saline.

In vitro and in vivo resistance of herpes simplex virus to 9-(2-hydroxyethoxymethyl)guanine (acycloguanosine)

In vitro passage of the Patton strain of herpes simplex virus type 1 (HSV-1-P) in the presence of acycloguanosine (ACG) led to the emergence of a highly drug-resistant strain (HSV-1-P-ACG-R). Over 1% of virions in 6 of 15 HSV strains tested were able to form plaques in the presence of 10 mumol of ACG on first exposure to the drug. Therefore, there exists among HSV strains a broad range of susceptibilities to ACG, and some strains contain particles which are partially resistant to ACG before ever contacting the drug. HSV-1-P-ACG-R was partially resistant to iododeoxyuridine; conversely, iododeoxyuridine-resistant virus was highly resistant to ACG. ACG-resistant virus (HSV-1-P-ACG-R) was equal to its parent strain (HSV-1-P) in susceptibility to adenine arabinoside. The HSV-1-P-ACG-R strain produced corneal lesions in rabbits which were completely refractory to topical treatment with 1% unguent ACG, but responsive to 3% ACG. Partially resistant HSV could be isolated from the eyes of rabbits infected with ACG-susceptible virus and treated topically with either 1 or 3% ACG for 6 days.

Application of immunofluorescence technique to clinical virology

Virologists for many years have striven to achieve the goal of rapid virus diagnosis. This book has described in detail one of the methods. The achievement of success in a method of rapid virus diagnosis cannot, in itself, be a final aim, otherwise the method would degenerate solely into a rapid routine method for identifying virus agents and the virologist would become a biological philatelist. An applied science, to justify itself, must bring benefit to the main clientele, which is in this case the physicians and the patients. In this chapter it is intended to evaluate the applications of rapid immunofluorescence diagnosis in clinical medicine.

Intraocular penetration of trifluridine

We studied intraocular penetration of topically applied trifluridine in five patients with herpetic keratitis undergoing penetrating keratoplasty. We compared the concentration of trifluridine and its metabolite 5-carboxy 2'-deoxyuridine in the aqueous humor to those of normal control patients undergoing routine cataract extraction without preoperative antiviral therapy. Significant concentrations of intact trifluridine were achieved in the acqueous humor after topical application of 1% trifluridine ophthalmic drops. The metabolite, 5-carboxy 2'-deoxyuridine, was not found in the aqueous humor. Unlike idoxuridine and vidarabine, it is possible to achieve therapeutic levels of trifluridine at intraocular sites that would be advantageous in the treatment of deep herpetic disease involving the stroma and iris.

Treatment of experimental herpes simplex keratitis with acycloguanosine

Acycloguanosine, a recently developed compound with high inhibitory activity against viruses belonging to the herpes group, has been evaluated in experimental herpes simplex keratitis in rabbits in comparison with trifluorothymidine and preparations of idoxuridine and vidarabine at present in clinical use. All compunds were used in the form of ophthalmic ointments which were applied 5 times a day at intervals of 2 hours. Treatment began on the third day of infection and was continued for 4 days. Complete cure was obtained with acycloguanosine and idoxurdine; trifluorothymidine and vidarabine were considerably less effective. Acycloguanosine was equally effective when given intravenously in the form of its sodium salt, and could be detected in the tear fluid in inhibitory concentrations when given by mouth. The compound was relatively free from toxicity.

A combined chemical-physical treatment for herpes simplex lesions in guinea pigs

Determination of the effectiveness of chemical treatments for Herpes simplex type 2 infections has generally relied on a reduction in the rate of mortality. A more natural progression of the disease is seen when non-progressive cutaneous lesions are induced. Treatment of characteristic cutaneous lesions with ultrasound alone, a cream compound designated Herpigon alone, or a combination of ultrasound and Herpigon were compared to determine the time required for lesions to heal and the amount of virus recoverable from treated lesions. Results indicate that the use of Herpigon alone or in combination with ultrasound resulted in a significant reduction in the time required for the lesions to heal. A comparison of the amount of virus present in treated lesions indicated that the combined treatment was most effective in reducing the amount of recoverable virus.

Comparison of the therapeutic effects of five antiviral agents on cutaneous herpesvirus infection in guinea pigs

Cutaneous herpesvirus infection of guinea pigs has been evaluated as a model for testing antiviral compounds. Six infected sites on each animal can be used independently for local treatment. The severity of the infection has been graded in a score system. The cumulative scores during infection and the time to healing can be used to determine antiviral effects. The effects of adenine arabinoside, cytosine arabinoside, iododeoxyuridine, ribavirin and phosphonoacetic acid on the cutaneous infection was compared. Phosphonoacetic acid was the only compound with a good therapeutic activity against herpesvirus infection, causing a reduction of both the cumulative score and the time to healing. Phosphonoacetic acid was skin irritating at 2 per cent, but at 1 per cent, which still had a good therapeutic activity, skin irritation was seen only occasionally.