Researchers at the MSU College of Veterinary Medicine have received a $95,714 Michigan Translational Research and Commercialization (MTRAC) grant from the MSU Innovation Center to develop a new feline herpesvirus-1 (FHV-1) vaccine. Dr. Gisela Soboll Hussey, associate professor for the Department of Pathobiology and Diagnostic Investigation (PDI), and Dr. Roger Maes, professor for PDI and section head of virology at the MSU Veterinary Diagnostic Laboratory, are the one-year project’s primary investigators. Their project aims to address shortcomings of current FHV-1 vaccines, specifically virus shedding and latency.
FHV-1 is highly contagious and causes acute upper respiratory infections (also known as “cat flu”). It’s easily transmitted through contact with saliva, nasal, or ocular secretions; this could be through direct or environmental contact. Even after a cat recovers, it is still a lifelong, latent carrier of the virus. Periods of high stress or immune suppression reactivate the latent infection. This results in renewed shedding of virulent virus. In addition, ocular disease—with a clinical picture that is very similar to that of ocular human herpes simplex virus—is common following a reactivation event.
Despite high vaccination rates and FHV-1 belonging to the core vaccine group for cats, disease incidence has remained unchanged. Currently available vaccines induce protection against clinical signs, but do not protect against infection with virulent virus when a vaccinated cat comes in contact with it. This, in turn, leads to virulent virus shedding and the potential for infection of susceptible cats that are in the same environment. As with other herpesviruses, a lifelong latent infection in nervous tissue is established as a consequence.
“We’re due for a better vaccine,” says Soboll Hussey. According to Hussey, vaccination has saved more lives than all other infectious disease control methods combined, but companion animal vaccine technology has not changed much in the past 40 years. “There’s room for advancement with newer and novel vaccine approaches.”
The High Cost of Herpesviruses
Herpesviruses are found in most mammals, and the economic burden of treating these diseases is hefty; for cows, approximately $3 billion is spent each year and for humans, $540 million is spent each year. This doesn’t account for the cost of treating and vaccinating other animals, like pigs, horses, and cats.
Eliminating Feline Injection-Site Sarcomas
The new vaccine Soboll Hussey and Maes are testing also can be administered via the respiratory tract. This counteracts the risk of vaccination-site sarcomas, which are malignant tumors that may develop weeks or years post-vaccination.
Additional Support
Soboll Hussey and Maes are collaborating with Dr. John Kruger, Pat Carrigan Chair in Feline Health and professor for the College’s Department of Small Animal Clinical Sciences. Additionally, Kruger oversees the Center for Feline Health and Wellbeing, which—along with the College’s Office of the Dean and the University’s Animal Care Program—helped fund components of this project’s experimental design.
Soboll Hussey and Maes’s project, called “Design and Testing of a New Generation of Herpesvirus Vaccines Using a Novel Vaccine Development System,” uses bacterial artificial chromosome (BAC) mutagenesis, a technology used to delete selected genes that are associated with virulence and immune suppression in combination with screening of mutants in primary feline respiratory epithelial cells.
Using this technology and extensive previous in vitro testing in feline respiratory epithelial cultures, Soboll Hussey and Maes have identified two candidates to be tested in vivo as FHV-1 vaccines. The goal is to produce a vaccine that addresses the current vaccine’s main shortcomings: protection against infection associated with virulent virus shedding and development of latency, which is easily reactivated and has been associated with serious ocular disease.
A successful vaccine will mean more than just better health for cats. This new vaccine development system will be applicable to other species, including humans, horses, and cows.