Margaret Brosnahan, DVM, MS, Dipl. ACVIM, a post-doctoral graduate student at Cornell, shared the research at the American Association of Equine Practitioners meeting in Las Vegas.
Small interfering RNA (siRNA) was injected nasally into 10 horses 12 hours before and 12 hours after a nasal injection of equine herpesvirus (EHV-1). Four other horses received an injection of EHV-1 as well as injections of siRNA that targeted an uninvolved gene.
Researchers hoped to see significantly less viral shedding from the virus in the blood. They didn’t. But clinical symptoms and results were much better, with horses less sick and fewer horses needing to be euthanized after neurological symptoms proved too painful and debilitating.
“The whole virus is clearly a lot more complicated,” Brosnahan says. “We saw improvement in clinical signs, in lessening mortality rates, but we didn’t see improvement in the intermediate steps of decreasing viral replication.” Researchers suspect individual horses’ immune system may be influencing the effects of the siRNA on the virus.
“The exciting thing about this is siRNA did something good. We’re just not sure what,” she says.
If siRNA makes its way into an equine medical product, it would fill a gap in the fight against equine herpesvirus between vaccination and treatment. “It’ll never be the silver bullet to end equine herpesvirus,” Brosnahan says. “We envision a product used right before an outbreak, where one horse is sick and other horses have been in contact.”
Data from a larger study at Cornell using different doses of siRNA is being examined now, Brosnahan says.