Effects of Anti Herpetic Drugs on Mice with Herpetic Epithelial Keratitis After Reactivation of Herpes Simplex Virus Type 1

Management of herpes simplex virus epithelial keratitis

PURPOSE OF REVIEW

To review recent advancements in the management of herpes simplex virus (HSV) epithelial keratitis.

RECENT FINDINGS

Trifluridine eye drop, acyclovir (ACV) ointment, ganciclovir gel, and oral ACV are still the main therapeutic agents. Cryopreserved amniotic membrane has been recently used as an adjuvant treatment. Resistance to ACV has become a concerning issue. The animal models of HSV vaccine are able to reduce HSV keratitis. New antivirals are under development.

SUMMARY

Current cases of HSV epithelial keratitis are manageable with available medications, but new advancements are required to decrease disease burden in the future. HSV vaccine can be revolutionary.

Effects of antiviral medications on herpetic epithelial keratitis in mice

PURPOSE

Aciclovir (ACV), valaciclovir (VACV) and famciclovir (FCV) are used for systemic infections caused by herpes virus. In Japan, only topical ACV is permitted for use against herpetic keratitis. We investigated the effectiveness of topical ACV, oral VACV and oral FCV on mouse epithelial herpetic keratitis.

METHODS

C57/BL76 mice were inoculated with HSV-1 McKrae strain in the cornea. Once infection was confirmed 4 days after inoculation, topical ACV, oral VACV and FCV were started and administered for 5 days. Control groups were given either topical or oral saline. On days 2, 4, 6 and 10 after medication started, tears, eyeballs, and trigeminal ganglia were examined using viral culture and real-time PCR.

RESULTS

Viral culture of tears detected no HSV in the topical ACV group on day 4 after administration start; with similar results for the oral VACV group on day 4; and the oral FCV group on day 6. Real-time PCR of the eyeballs showed significant decrease of HSV DNA copy number in the topical ACV group on days 4 and 6 compared to the topical saline group. Real-time PCR of the trigeminal ganglia showed significant decrease of HSV DNA copy number in the oral VACV group on days 4 and 6, and in the oral FCV group on day 6 compared to the oral saline group.

CONCLUSION

We suggest that 5-day administration of topical ACV, oral VACV and oral FCV are effective for mouse epithelial herpetic keratitis and sufficiently decrease HSV amounts in the ocular surface and eyeballs.

Pharmacokinetics of famciclovir and penciclovir in tears following oral administration of famciclovir to cats: a pilot study

OBJECTIVE

To validate a means of collecting tears from cats, develop an assay for quantifying famciclovir and penciclovir in tears, and to assess famciclovir and penciclovir concentrations and pharmacokinetics in the tears of cats being treated orally with famciclovir for suspected herpetic disease.

ANIMALS

Seven client-owned cats.

PROCEDURES

Cats were treated orally with a median (range) dose of 40 (39-72) mg of famciclovir/kg three times daily for at least 24 h. At various time points following famciclovir administration, tear samples were collected using Schirmer tear test strips. Tear famciclovir and penciclovir concentrations were measured using liquid chromatography-mass spectrometry, and concentration-time profiles were analyzed noncompartmentally. The relationship between famciclovir dose and tear penciclovir concentration near its maximum was evaluated using least squares linear regression.

RESULTS

Maximum tear famciclovir concentration of 0.305 μg/mL occurred at 2.64 h; elimination half-life was 2.28 h. Maximum tear penciclovir concentration (0.981 μg/mL) occurred 2.25 h following oral administration of famciclovir; elimination half-life was 2.77 h. A significant positive correlation was noted between famciclovir dose and tear penciclovir concentration at various time points between 0.5 and 3.75 h following drug administration (P = 0.025). Tear penciclovir concentration exceeded the concentration shown to have in vitro efficacy against feline herpesvirus (FHV-1) (0.304 μg/mL) in about half of samples collected.

CONCLUSIONS

Oral administration of 40 mg of famciclovir/kg to cats resulted in a tear penciclovir concentration-time profile that approximated the plasma penciclovir concentration-time profile and frequently achieved a penciclovir concentration at the ocular surface likely to be effective against FHV-1.

Evaluation of orally administered famciclovir in cats experimentally infected with feline herpesvirus type-1

OBJECTIVE

To evaluate orally administered famciclovir for treatment of cats with experimentally induced disease attributable to feline herpesvirus type-1 (FHV-1).

ANIMALS

16 nonvaccinated specific-pathogen-free cats.

PROCEDURES

Cats were treated orally with famciclovir (90 mg/kg; n = 10) or a similar volume of lactose (400 mg; 6) 3 times/d for 21 days. Cats were inoculated with FHV-1 and administered the first treatment dose on day 0. Disease score; weight; results of urinalysis, serum biochemical analysis, and CBC; histologic conjunctivitis score; herpetic DNA shedding; goblet cell density; anti-FHV-1 antibody concentration; and plasma penciclovir concentration were measured.

RESULTS

On days 4 to 18 following inoculation, disease scores were lower in famciclovir-treated cats than in lactose-treated cats. Lactose-treated cats decreased in weight during the first 7 days after inoculation, but famciclovir-treated cats increased in weight throughout the study. Percentage change in weight was greater in famciclovir-treated cats on days 7 and 14 than in lactose-treated cats. Serum globulin concentration was lower on days 3 through 9, conjunctivitis histologic score was lower on day 14, herpetic DNA was shed less frequently throughout the study, goblet cell density was greater on day 21, and circulating anti-FHV-1 antibody concentration at study end was lower in famciclovir-treated cats, compared with these measurements in lactose-treated cats. Approximate peak plasma penciclovir concentration was 2.0 μg/mL.

CONCLUSIONS AND CLINICAL RELEVANCE

Famciclovir administration improved outcomes for systemic, ophthalmic, clinicopathologic, virologic, and histologic variables in cats experimentally infected with FHV-1. Adjunctive topical mucinomimetic and antimicrobial treatments may also be necessary.

Aciclovir-resistant herpes keratitis

Herpes simplex virus (HSV) keratitis is a common cause of ocular morbidity. Resistance to aciclovir is probably under recognized. We describe three cases of aciclovir-resistant herpes simplex virus keratitis treated with systemic foscarnet and present a review of the pharmacological options available to manage this condition.