In a world first, scientists have developed a vaccine that is successful against a prion disease; a rare infectious disorder that causes progressive brain damage. The researchers were able to demonstrate that their novel vaccine was effective against chronic wasting disease (CWD), a fatal illness affecting deer and other animals. Although the study was small, the vaccine is a major scientific milestone and raises the possibility that it may be possible to prevent similar disorders in humans, such as Creutzfeldt-Jakob disease. The work has been published in Vaccine.
Prion diseases are a family of fatal and progressive disorders that affect the brain and nervous system of both humans a variety of animals. Currently, there are no specific treatments or licenced vaccines for any prion disease. Although these disorders are thought to be extremely infectious, they are not caused by microorganisms such as bacteria or viruses. Instead, they are thought to be caused by an infectious agent called a prion, which is a protein in an abnormal form.
The prion protein (PrP) is found throughout the nervous system and is thought to play a variety of important roles, such as protecting brain cells from injury and facilitating neuronal communication. However, this protein can be misfolded into a rogue version which then propagates by triggering a “domino effect,” causing other normal prion proteins to convert into the abnormal form. It is the accumulation of this misfolded protein that leads to the progressive loss of brain tissue and the variety of symptoms associated with the disease.
Prion diseases are known to affect a variety of animals,T including humans. Variant Creutzfeldt-Jakob disease, for example, is the human form of BSE, or “mad cow disease,” which is believed to be caused by eating beef products contaminated with nervous tissue from infected cattle. Another important prion disease is CWD, which affects cervids (a species in the deer family) such as white-tailed deer, elk and moose. CWD affects as much as 100% of North America’s captive deer population and there is a growing concern that it could spread to livestock or even infect humans. In the absence of any proven treatments, there exists a pressing need for an effective vaccine to prevent this from happening.
Now, it seems this could be within our grasp as significant progress has been made by researchers at NYU Langone Medical Center, who recently developed a CWD vaccine. They achieved this by inserting the cervid PrP gene into weakened, or attenuated, Salmonella bacteria. These organisms then produce the prion protein inside the animals, which triggers the immune system to produce anti-prion antibodies.
To test it out, 5 deer were administered the vaccine, followed by 8 boosters, and 6 were given a placebo. All of the animals were then exposed to prion-infected brain tissue and housed together, maintaining constant prion exposure. The animals were then constantly monitored and biopsies were regularly taken to look for signs of prion infection.
Within two years, all of the control deer developed CWD, but four of the vaccinated animals took significantly longer- and the 5th remains CWD free. Although it’s early days, these promising results raise the possibility that this method could be used as a widespread technique to both prevent and treat a variety of prion diseases.