Early success for vaccine against brain-wasting disease

Chuck Bednar for redOrbit.com – Your Universe Online
Researchers have reportedly developed the first successful vaccination against a condition similar to Mad Cow Disease that affects deer – a discovery that could not only help prevent US livestock from contracting the ailment, but could help prevent similar infections in humans.
Dr. Thomas Wisniewski, a neurologist at New York University’s Langone Medical Center, and his colleagues explain that the condition known as chronic wasting disease (CWD) is caused by unusual infectious proteins known as prions, spread by converting other proteins.
Their research, which was published Sunday in the journal Vaccine, represents what the authors call “a scientific milestone.” Not only is it the first successful vaccination of deer against CWD, it is also said to hold promise in combating human diseases believed to be caused by prion infection, including Creutzfeldt-Jakob disease, kuru and variably protease-sensitive prionopathy.
Up to 100 percent of captive deer in North America have been infected by CWD, as have large numbers of wild deer, elk, carbiou and moose. Scientists have grown increasingly concerned that the condition could spread to livestock populations in the same regions, especially cattle.
If additional experiments involving the vaccine prove successful, Dr. Wisniewski’s team plan to inoculate a relatively small sample of animals (as few as 10 percent) in an attempt to induce herd immunity and prevent a possible widespread outbreak similar to the way Mad Cow Disease (bovine spongiform encephalopathy) spread through the UK nearly 20 years ago.
“Now that we have found that preventing prion infection is possible in animals, it’s likely feasible in humans as well,” explained Dr. Wisniewski, whose team fashioned the vaccine using Salmonella, a gut bacteria used to mirror the most common form of natural prion-infection, the ingestion of prion-contaminated food or feces.
During their experiments, five deer were given the vaccine, which consisted of an attenuated (no longer dangerous) Salmonella bacterium genome that had been injected with a prion-like protein in order to encourage the production of anti-prion antibodies. Six other deer were given a placebo, and all of them were exposed to prion-infected brain tissue.
The deer were all housed together and engaged in group activities similar to those living in the wild. Dr. Wisniewski’s team explained that this kept them in constant exposure to the infectious prions. The deer that were vaccinated were given a series of eight boosters over 11 months until key immune antibodies were detectable in blood, saliva, and feces.
All of the creatures were monitored each day for signs of illness, and investigators performed biopsies of the animals’ tonsils and gut tissue every three months to search for signs of CWD infection. Within two years, all deer in the placebo group developed CWD, while four members of the vaccine group took far longer to develop the condition and one remained infection free.
“Although our anti-prion vaccine experiments have so far been successful on mice and deer, we predict that the method and concept could become a widespread technique for not only preventing, but potentially treating many prion diseases,” said Dr. Fernando Goni, lead investigator of the study and an associate professor at NYU Langone.
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