Experimental Herpes Simplex Keratitis Research Articles

Ganciclovir: a promising topical antiviral gel for herpetic keratitis

Ganciclovir (GCV) is a potent broad-spectrum antiviral with proven efficacy against herpes viruses. As it inhibits viral but not cellular DNA, it is expected to avoid the toxicity associated with trifluridine – the only currently approved treatment for herpes simplex keratitis in the USA. Preclinical studies have demonstrated GCV to be as effective as trifluridine against experimental herpes simplex keratitis. Clinical studies conducted in Europe, Asia, and Africa that compared the efficacy and tolerability of GCV ophthalmic gel with acyclovir (ACV) ophthalmic ointment in patients with herpetic keratitis showed that GCV-treated patients had higher overall healing rates and lower relapse rates than ACV-treated patients. The ganciclovir gel formulation was also much better tolerated than the ACV ointment base. Finally, a controlled, masked, randomized series of 18 patients with adenoviral keratoconjunctivitis compared GCV gel with preservative-free artificial tears. Ganciclovir-treated patients experienced a shorter acute-disease phase and exhibited significantly fewer subepithelial infiltrates.

Impression Cytology of Herpetic Simplex Keratitis in Rabbits

To use impression cytology to examine the structural changes in corneal epithelial cells infected with the herpes simplex virus in rabbit eyes. Corneal surfaces of 7 rabbits were scratched using a 25-gauge needle. Herpes simplex virus (type 1, Kos strain) was inoculated to the injured cornea. As the corneal diseases were observed using slit lamp biomicroscopy, impression cytology was performed for 18 days after inoculation. Specimens were stained with hematoxylin-eosin and examined using optical microscopy. Corneal lesions consisted mainly of round epithelial cells, inflammatory cells, ballooning cells, multinucleated giant cells, and various inclusion bodies. Over time, the comeal epithelial cells peeled away as a result of corneal edema in the comeal lesions. Dendritic lesions were also observed. In the recovery phase, the number of detached cells and infiltrated inflammatory cells decreased. It was presumed that dendritic lesions might have been formed at the scratched cornea region, thereby aggravating the epithelial cells falling off as a result of the infiltration of inflammatory cells. These cytopathologic effects occur in experimental herpes simplex keratitis.

Tetrandrine potently inhibits herpes simplex virus type-1-induced keratitis in BALB/c mice

This study investigated the effect of tetrandrine (TDR) on ex-perimental herpes simplex keratitis (HSK) in mice. BALB/c mice were di-vided as follows: Group I, untreated; Group 2, acyclovir (ACV)-treated from day o postinfection; Group 3, ACV-treated from day 7; Group 4, TDR-treated from day O; and Group 5, TDR-treated from day 7. All mice were infected in the right cornea with herpes simplex virus (HSV) type I. TDR 30 mg/kg and ACV 120 mg/kg were administered intraperitoneally daily. The mice were observed for 14 days postinfection. Clinical inflammatory reactions and ocular histopathology were analyzed. The herpes specific antibody response and the delayed type hypersensitivity (DTH) response were stud-ied. Of the 22 untreated mice, 16 developed HSK (incidence, 72.7%). TDR given from day 7 reduced the HSK incidence to 8.5% (p< 0.01); the inci-dence of HSK was 45.4% in mice treated with TDR from day o (p >0.05). Systemic ACV given from day o inhibited HSK development (P<0.01); ACV given from day 7 resulted in an HSK incidence of 50% (p >0.05). The specific anti-HSV antibody response in the serum of mice treated with TDR or ACV either from day o or day 7 was significantly less than that of un-treated mice (p<0.01 and p<0.05, respectively), and TDR treatment sup-pressed DTH responses to HSV (p<0.05). Systemic TDR administered after HSV inoculation of the cornea significantly modulates murine HSK devel-opment at least partly by modifying the host immune/inflammatory response to the virus.

T cell receptor V beta gene expression in experimental herpes stromal keratitis.

Our study examined T cell receptor (TCR) V beta mRNA expression in a murine model of experimental herpes simplex keratitis (HSK). We employed a polymerase chain reaction (PCR) technique to detect TCR V beta mRNA expression in the inoculated eyes of both HSK-susceptible and HSK-resistant mice at different time points after corneal inoculation with herpes simplex virus type 1 (HSV-1), followed by Southern blotting and densitometry analysis. In eyes from HSK-susceptible C.AL-20 mice, a more diverse TCR V beta transcript usage pattern was detected as compared with that seen in HSK-resistant C.B-17 mice. V beta 8 family members were expressed in both strains of mice at days 11, 14 and 21 post-inoculation. By densitometry, at day 11, the intensity of expression of V beta 8.2 and V beta 8.3 message was significantly greater in the eyes of C.AL-20 mice; V beta 8.1 was expressed only in C.B-17 mice. There were obvious differences in the TCR V beta expression between HSK-susceptible and HSK-resistant mice. The differences in the intensity of the message expressed by V beta 8 family members between the two strains could be correlated to previous experiments that showed V beta 8.1,2+ T cells as the main infiltrating cells in the corneas of HSK-susceptible mice by day 11 and 14 after challenge with HSV-1.

163 Effect of dexthan sulfate on experimental herpes simplex keratitis in rabbits: S. N. Pancheva. Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria

163 Effect of dexthan sulfate on experimental herpes simplex keratitis in rabbits: S. N. Pancheva. Institute of Microbiology, Bulgarian Academy of Sciences, Sofia, Bulgaria

Effect of saponins from Anagallis arvensis on experimental herpes simplex keratitis in rabbits.

Effect of saponins from Anagallis arvensis on experimental herpes simplex keratitis in rabbits.

The effect of a new lipoxygenase inhibitor on the production of arachidonic acid metabolites during experimental herpes simplex keratitis.

We have studied the effect of a new, selective lipoxygenase inhibitor, TEI-1338, on alterations in arachidonic acid (20:4) metabolism and breakdown of the blood-aqueous barrier during herpes simplex virus (HSV) infection of the rabbit cornea. Synthesis of cyclooxygenase products (prostaglandins) and the lipoxygenase products, hydroxyeicosatetraenoic acids (HETEs) and leukotriene B4 (LTB4), was measured in vitro by assessing conversion of 1-14C-20:4 in infected and non-infected corneas. TEI-1338 inhibited infection-stimulated lipoxygenase activity in a concentration-dependent manner, without affecting cyclooxygenase activity. Treatment of herpes infection in vivo with TEI-1338 (ocular drops) reduced leakage of protein into aqueous humor, a measure of inflammation-induced deterioration of the blood aqueous barrier. These data indicate that drugs that selectively inhibit lipoxygenase may be useful in the treatment of the inflammatory consequences of herpes keratitis, without exacerbating the infectious process.

Evaluation of bromovinyldeoxyuridine-related compounds in the treatment of experimental herpes simplex keratitis.

Several newly synthesized compounds, all structurally related to the highly potent and selective antiherpes agent bromovinyldeoxyuridine ( [E]-5-[2-bromovinyl]-2'-deoxyuridine), have been evaluated for their healing effect on herpes simplex virus type 1 keratitis in rabbits. These novel compounds included chloroethyldeoxyuridine (5-[2-chloroethyl]-2'-deoxyuridine), trifluoropropenyldeoxyuridine ( [E]-5-[3,3,3-trifluoro-1-propenyl]-2'-deoxyuridine), bromovinylaminodideoxyuridine ( [E]-5-[2-bromovinyl]-3'-amino-2',3'-dideoxyuridine), bromovinylarabinofuranosyluracil ( [E]-5-[2-bromovinyl]-1-beta-D-arabinofuranosyluracil), and glycylbromovinyldeoxyuridine (5'-O-aminoacetyl-[E]-5-[2-bromovinyl]-2'-deoxyuridine). Bromovinylaminodideoxyuridine and trifluoropropenyldeoxyuridine did not promote a significant healing of herpes simplex keratitis. Bromovinylarabinofuranosyluracil markedly reduced the severity of keratitis, but to a significantly lesser extent than bromovinyldeoxyuridine. Finally, chloroethyldeoxyuridine and glycylbromovinyldeoxyuridine caused a pronounced healing effect on herpes simplex keratitis, comparable to that obtained with bromovinyldeoxyuridine. Chloroethyldeoxyuridine was even slightly better than bromovinyldeoxyuridine, but the difference in their healing effect was not statistically significant.

Therapy of Experimental Herpes Simplex Keratitis in Rabbits with 5-lodo-5'-Amino-2',5'-Dideoxyuridine

SummaryAIU (5-iodo-5′-amino-2′,5′-dideoxyuridine, AIdUrd) has been shown to be as effective as IdUrd in the treatment of experimental herpes simplex keratitis in rabbits. AIU's striking lack of cellular or systemic toxicity or teratogenicity and its specific inhibition of viral metabolism are discussed.The authors acknowledge the valuable technical assistance of Mr. Alfred S. Fiore and Mr. Ronald Callahan (Departments of Pharmacy and Nuclear Medicine, Massachusetts General Hospital). Mrs. Brigitte A. Prusoff performed the statistical analysis.

Effect of phosphonoacetic acid in the treatment of experimental herpes simplex keratitis.

In the rabbit 5% phosphonoacetic acid ointment suppressed herpetic keratitis as well as 0-5% idoxuridine ointment. After 5 days of treatment quantitative virus titres showed that phosphonoacetic acid was superior to idoxuridine in the inhibition of herpes virus replication. Phosphonoacetic acid was found to be nontoxic to the eye in both clinical and histopathological studies. Recent reports suggest that the mechanism of action of phosphonoacetic acid appears to be the blocking of the virus DNA polymerase, which is essential for the synthesis of herpes virus DNA.

Photodynamic inactivation in experimental herpetic keratitis.

The effect of photodynamic inactivation on experimental herpes simplex keratitis in rabbits was investigated using neutral red as a photosensitizing dye followed by exposure to light at 425nm. Combined dye application and light exposure early in the disease (two days following infection) reduced to a minimal extent the severity and duration of the acute epithelial infection. The effect on well-established keratitis (three days postinfection) was negligible as evaluated by clinical grading, viral recovery, and histopathological study. In initial experiments, it was found that the dye and light did not have any observable deleterious effect on intact corneas or cause any noticeable delay in healing of injured cornias. Further, when light or dye were utilized alone, neither changed the severity or duration of the keratitis. In vitro treatment of the virus with light and dye destroys its ability to produce experimental keratitis.

The Treatment of Experimental Deep Herpes Simplex Keratitis with Ethyl-Deoxy-Uridine and Iodo-Deoxy-Cytidine

Two antiviral agents, ethyl-deoxy-uridine and iodo-deoxy-cytidine, were compared therapeutically for their effect on experimental deep herpetic keratitis in rabbits. While iodo-deoxy-cytidine is a competitive inhibitor of thymidine, ethyl-deoxy-uridine works by blocking the enzyme deoxythymidine-kinase (EC 2.7.1.21). The clinical results and histopathological changes showed that both drugs were effective, and that ethyl-deoxy-uridine as well as iodo-deoxy-lytidine seemed non-toxic for the epithelium.

Spontaneous reactivation of experimental herpes simplex keratitis in rabbits.

Daily slit-lamp biomicroscopic examination and daily virus cultures for six months of 20 herpes simplex infected rabbit corneas have been used to follow the natural course of this experimental infection. More than two months after the signs of primary infection had cleared completely, 13 of 20 eyes (65%)spontaneouslyreleased herpes simplex virus, yielding positive cultures for 1 to 11 days (average seven days). Most of these corneas showed spontaneous recurrence of clinical activity including dendritic figures. The high incidence of spontaneous reactivations stresses the need for critical assessment of studies reportinginducedreactivation of experimental herpes simplex keratitis.

EFFECTIVE TREATMENT OF EXPERIMENTAL HERPES SIMPLEX KERATITIS WITH NEW DERIVATIVE, 5-METHYLAMINO-2'-DEOXYURIDINE (MADU).

SummaryA recently synthesized compound, 5-methylamino-2′-deoxyuridine (MADU) was shown to be highly active in suppressing infection with herpes simplex virus in vitro and to exert beneficial effect in therapeutic and prophylactic-therapeutic treatment of experimental keratitis in the rabbit eye caused by herpes simplex virus. The beneficial effect was equal to or only slightly less than that observed in comparative tests with 5-iodo-2′-deoxyuridine (IDU). The low toxicity of MADU for the rabbit eye, the high level of activity, the absence of halogen, and the apparent low level incorporation into the DNA of host cells justify experimental investigations in man in infections in which IDU would normally be employed. The practical and theoretical implications of use of MADU and IDU in the human being are discussed.

CYTOSINE ARABINOSIDE (CA) AND OTHER NUCLEOSIDES IN HERPES VIRUS INFECTIONS.

Certain inhibitors of normal deoxyribonucleic acid (DNA) synthesis have been found to be clinically effective antiviral agents. After the observation that idoxuridine (5-iodo-2′-deoxyuridine, IUdR, IDU) inhibited herpes simplex virus plaques in a cell culture system (Herrmann, 1961),1it was reported that this agent was highly active in curing herpes simplex keratitis in rabbits (Kaufman, 1962)2and in man (Kaufman et al, 1962).3Subsequently, another pyrimidine nucleoside, 1-β-d-arabinofuranosylcytosine hydrochloride (cytosine arabinoside or CA) was shown to cure herpes keratitis in rabbits (Underwood, 1962)4and in man (Kaufman and Maloney, 1963).5Because of the potential importance of these agents in antiviral chemotherapy, we continued our work on CA and expanded our studies to include other pyrimidine arabinosides. Materials and Methods In Vivo. —Previously described procedures (Underwood, 1962)4used to produce experimental herpes simplex keratitis in rabbits were modified as follows. Two drops of 2%

CORNEAL TOXICITY OF CYTOSINE ARABINOSIDE.

Antiviral agents are, in many ways, similar to antibiotics. They inhibit virus multiplication and can make the use of corticosteroids safer by preventing the reactivation of latent virus and controlling the tendency of virus to multiply in the presence of corticosteroids. Like antibiotics, resistance to these agents can develop and the agents may have some effect on the host. Cytosine arabinoside (CA) is a therapeutically active antiviral agent which has the ability to alter the course of viral and cell multiplication.1In addition to being able to cure experimental herpes simplex keratitis, CA has been extremely useful in treating patients with herpetic keratitis which is resistant to therapy by idoxuridine (5-iodo-2′-deoxyuridine, IDU).2Although CA is more soluble than idoxuridine and allows preparations to be used less frequently than idoxuridine, it has the disadvantage of producing, under some circumstances, a reversible corneal toxicity. Corneal toxicity was first observed in

CHYMOTRYPSIN FOR EXPERIMENTAL HERPES SIMPLEX KERATITIS.

To the Editor: In our experiment, Chymotrypsin for Experimental Herpes Simplex Keratitis, which was reported in the April, 1964, issue ofArchives of Ophthalmology, a concentration of 10,000 units per cubic centimeter of alpha-chymotrypsin was used rather than 1 to 10,000 units per cubic centimeter as printed in the publication; and this preparation was lyophilized chymotrypsin rather than Chymar Aqueous. The Correspondence section welcomes inquiries and comments of a general or specific nature. The Editors may try to answer some of the questions, but more valuable will be the answers volunteered by others who have had especial experience related to the questions posed.

IDU and Cytosine Arabinoside in Experimental Herpetic Keratitis

Recently 5-iodo-2′-deoxyuridine (IDU) has been shown to be effective in experimental herpetic keratitis of rabbits as well as in herpes simplex keratitis in man.^1,2Since the discovery of the therapeutic antiviral activity of this compound, a search for additional compounds has been made. The first success came with the finding that a series of substituted 5-haloginated cytidines also possessed therapeutic antiviral activity in experimental keratitis.³These compounds, although possessing superior solubility, and perhaps stability, were as active as the original compound IDU, being metabolized to this compound by the cells and depending for antiviral activity on the ability of the cell to convert and de-aminate the compound. The mechanism of the action of these agents, therefore, was identical to that of IDU and the other 5-haloginated uridines. Recently, Underwood reported that cytosine arabinoside is also active in the treatment of experimental herpes simplex keratitis.⁴This compound differs

A Double-Blind Study of the Effect of 5-IODO-2'-Deoxyuridine on Experimental Herpes Simplex Keratitis

The therapy of herpes simplex keratitis has been limited almost exclusively to the palliative effect of chemical or mechanical debridement of virus-infected epithelial cells. For this procedure alpha chymotrypsin· was recently added to the list of chem­ icals. Trials with various antibiotics, fever therapy, smallpox vaccination, gamma glob­ ulin and cortisone have also been made but have failed to affect materially the course of the disease. A recent report by Brown et al. on the successful use of cop­ per sulfate iontophoresis has yet to be con­ firmed. Recently Kaufman and Kaufman, Nesburn, and Maloney first used an antimetabolite on experimental herpes simplex keratitis in rabbits. They reported complete cure of all infected animals within 48 hours of instituting therapy with 5-iodo-2' deoxyuridine ( IDU) . The disease recurred in only 16 of their 43 rabbits. When the drug was used in experimental herpes that had invaded the stroma, the results were not as good: seven cures in a total of 17 eyes. This group compared favorably, however, with a

IDU and hydrocortisone in experimental herpes simplex keratitis.

The indiscriminate clinical use of corticosteroids the eye is red has contributed greatly to the severity and variety of herpes simplex keratitis. 1,2 Similarly, the deleterious effects of corticosteroids on experimental herpes simplex keratitis have been well documented. 3,4 Since, when used indiscriminately, corticosteroids are dangerous, and since the antiviral agents described to date are not effective in treating iritis or disease accompanied by folds in Descemet's membrane, 5 it would be desirable if topical corticosteroids could be used with safety. The preparation, 5-iodo-2'-deoxyuridine (IDU), is a specific antiviral agent that stops viral replication. 6,7 The experiments described below document the effects of the combination of IDU with corticosteroids. Methods and Materials Albino rabbits were infected with strains of herpes simplex virus as previously described. 6 Drops of IDU were administered as a 0.1% solution and hydrocortisone as a 0.5% solution. In some experiments, when the two were given