Despite being a vaccine-preventable disease, rabies claims more than 55,000 lives each year, almost 50% of whom are children under the age of 15. Part of the problem is that once symptoms start showing, the virus has already spread through the nervous system and post-exposure treatment becomes ineffective, meaning the disease is almost always fatal. But now, new research suggests that scientists could be closer to a more effective treatment that works significantly longer after infection than what was originally thought possible.
Virologists from the University of Georgia have tested out an experimental rabies therapy on infected mice, which was found to cure a significant amount of animals even after the virus reached the brain. Although it’s early days yet, the study raises hope that, with further development, this promising treatment could help rabies patients even after the virus has progressed through the nervous system and symptoms start appearing. The work can be found in the Journal of Virology.
Rabies is a viral disease of mammals which is present on every continent except Antarctica, occurring in more than 150 countries and territories across the globe. The disease affects various domestic and wild animals, such as dogs and bats, but can be transmitted to humans through a deep bite or wound.
Following infection, the virus spreads to the central nervous system, causing progressive, fatal inflammation of the brain and spinal cord. It can take up to a year for symptoms to show up, but some infected individuals show signs within a week. Although there is an effective vaccine which prevents infection both pre- and post-exposure, there is only a narrow window in which to seek treatment before it is too late. But that might not be the case for too much longer, thanks to a newly developed vaccine.
The vaccine was created by inserting the gene for the rabies virus surface protein into a different virus, called parainfluenza 5 (PIV5). This virus is thought to cause respiratory tract infections in dogs but is harmless to humans. After administration, the modified virus begins to churn out the rabies virus proteins, which the immune system then generates antibodies against. This then helps the body recognize the invading rabies virus and mount a response against it.
The researchers tested out this experimental vaccine on mice infected with a strain of rabies virus which usually takes three days to reach the animal’s brain. Six days after exposure, the animals began displaying typical rabies symptoms, indicating that it had progressed through the central nervous system. However, the scientists managed to save 50% of the mice with the vaccine, even when it was administered after the onset of symptoms.
“This is the most effective treatment we have seen reported in the scientific literature,” lead researcher Biao He said in a news release. “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.”
Furthermore, the researchers point out that this vaccine may be safer than existing vaccines which use an attenuated, or weakened, version of the rabies virus.