“Herpes-induced cornea infections are a big problem in cats,” said Gerlinde Van de Walle, DVM, Ph.D., assistant professor of viral pathogenesis, who led the study. “If not treated, FHV-1 infection can eventually lead to blindness. We wanted to develop a model system that could predict whether an antiviral drug would work against FHV-1 in cats.”
The researchers also wanted an easy way to identify drugs that could be given only once every 24 hours. Current available drugs to treat such infections must be applied multiple times a day, a difficult and sometimes painful thing to accomplish, the researchers noted.
As part of the study, the researchers used tissues donated from cats that died of causes other than eye disease. The cornea was of particular importance. To maintain the natural, dome-shaped structure of these corneas under laboratory conditions, the team gently filled them with agarose, waited for the agarose to firm up, then turned them over and kept them in a liquid medium. The model better resembles what happens in the eyes of a cat compared with using a single layer of cells in a dish and can, therefore, better predict what to expect in the animal, according to the researchers.
To use these petri plate corneas as a model of FHV-1 infection, they applied the virus to some of the corneas and left others uninfected. They then tested the effectiveness of two drugs that are used for topical treatment of FHV-1 eye infections in cats: cidofovir, which is frequently used in the clinic, and acyclovir, which has shown some activity when given frequently.
Both drugs cleared the infection when applied every 12 hours, but cidofovir was more effective, according to the researchers.
The researchers also used the model system to identify another drug for treating FHV-1 infections: raltegravir, an antiretroviral drug commonly used in humans to treat HIV infections. Although some reports indicated it could be effective against herpes viruses, it had never been used to treat FHV-1 in cats before, the researchers noted.
“We found that it is very effective against FHV-1,” said Van de Walle. “It even worked when we applied the drug only once every 24 hours.”
This means raltegravir could be just as efficient as the other drugs available for treating FHV-1 infections, but would only have to be administered once daily, according to the researchers.
Van de Walle said she hopes to see the drug tested in a well-controlled clinical trial.
The study, recently reported in the Journal of General Virology, was supported by the Cornell Feline Health Center.