Researchers at a medical facility in Manhattan say they
have developed a vaccine that counters Chronic Wasting Disease of deer and elk
and therefore holds promise of doing the same for Creutzfeldt Jakob disease of
humans, Bovine Spongiform Encephalopathy of cattle and scrapie of sheep.
“Now that we have found that preventing prion infection
is possible in animals, it’s likely feasible in humans as well,” says senior
study investigator and neurologist Thomas Wisniewski, a professor at NYU
Langone.
According to Dr. Wisniewski and his research team, if
further vaccine experiments prove successful, a relatively small number of
animals (as few as 10 per cent) could be inoculated to induce herd immunity for
elk and deer in the wild. They are considered a threat to spread CWD prions to
cattle.
For the study, five deer were given the vaccine; another
six were given a placebo.
All of the deer were exposed to prion-infected brain
tissue; they also were housed together, engaging in group activities similar to
those in the wild.
Scientists say this kept them in constant exposure to
the infectious prions.
The animals receiving the vaccine were given eight
boosters over 11 months until key immune antibodies were detectable in blood,
saliva, and feces.
The deer also were monitored daily 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 of the deer given the placebo
developed CWD.
Four deer given the real vaccine took significantly
longer to develop infection — and the fifth one continues to remain infection
free.
Wisniewski and his team made the vaccine using
salmonella bacteria, which easily enters the gut, to mirror the most common
mode of natural infection — ingestion of prion-contaminated food or feces.
That’s how BSE, or mad cow’s disease, spread in cattle
herds that were fed rations incorporating rendered brain tissue from deadstock.
To prepare the vaccine, the team inserted a prion-like
protein into the genome of an attenuated (i.e. no longer dangerous) Salmonella
bacterium.
This engineered the salmonella to induce an immune
response in the gut, producing anti-prion antibodies.
“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,” says lead study investigator Fernando Goni, PhD, an
associate professor at NYU Langone.
