A person bit by a rabid animal has only a finite amount of time to get treated with the proper vaccine before it is too late. Allow a rabid bite to fester long enough for the virus to reach the brain and for neurological symptoms to set in, and the infection is usually fatal.
But a new vaccine, developed by scientists at the University of Georgia, promises to extend that window of opportunity, enabling the successful treatment of a rabies infection well past the traditional cutoff point.
That cutoff point for successful rabies treatment varies depending on the location of the bite and animal involved. For humans, the window of opportunity for successful treatment can run anywhere from six days to a month or more.
But for the mice used in this study, the cutoff was exactly six days. The strain of the rabies virus used by researchers reached the brains of the test subjects within three days, and neurological symptoms typically set in by day six — the sign that the end is near and that treatment is likely futile.
The new vaccine, however, saved 50 percent of the mice treated on day six. With previous vaccines, such a treatment attempt would have usually been in vain.
“This is only the beginning of our work,” said co-author Biao He, a professor of infectious diseases at Georgia’s College of Veterinary Medicine.
“While these preliminary results are very exciting, we are confident that we can combine this new vaccine with other therapies to boost survival rates even higher and rescue animals even when symptoms are severe.”
The new vaccine is created by injecting a protein from the rabies virus into a parainfluenza virus 5 sample. Parainfluenza virus 5, or PIV5, is an upper respiratory virus that typically affects dogs, but that is harmless to humans. It acts as a ideal delivery system for the rabies protein, enabling the immune system to develop antibodies to fight off the infection.
“This is the most effective treatment we have seen reported in the scientific literature,” Biao said. “If we can improve these results and translate them to humans, we may have found one of the first useful treatments for advanced rabies infection.”
Today, human deaths from rabies are exceedingly rare in the United States. But thousands still die around the world from rabies infections, mostly in Africa and Asia. More than a third of those victims are children.
“There is an urgent need in many parts of the world for a better rabies treatment, and we think this technology may serve as an excellent platform,” said study author Zhen Fu, a professor of pathology at the college. “Ultimately, we just want to try to save more lives.”
The study was published in the Journal of Virology.