The task of hunters in the fight against chronic wasting disease in deer is to slow the spread and help buy time for science to find solutions. While potential solutions are still elusive, hunters should know the work is ongoing, and there is slow progress. As a good example, researchers recently announced they tested an experimental CWD vaccine based on a new understanding of CWD prion structure and produced a measurable immune-system response in elk.
To be clear, this does not mean we now have a CWD vaccine, it means we are one step closer to that goal with a long path remaining ahead. Here’s the latest development in the hunt.
It’s Tough To Fight Proteins With Vaccines
CWD is caused by a disfigured protein called a prion, and the nature of proteins makes it very difficult to create vaccines that induce immune responses when bad proteins appear – far more difficult than with viruses. Previous attempts to create CWD vaccines for deer mostly succeeded in infecting the subjects faster rather than protecting them. Though some vaccinated subjects lived longer than the unvaccinated, all of them still died of CWD.
Researchers at the Centre for Prions and Protein Folding Diseases at the University of Alberta in Canada say they found a potential loophole. Proteins are complex structures built of chains of amino acids. Imagine a bird’s nest of fishing line from the last time you backlashed a baitcaster and you’ll be close to picturing protein structure. When a deer’s immune system encounters a disfigured protein like a CWD prion, normal immune reactions aren’t effective.
“It’s not that there’s no immune response in nature,” said Dr. Andrew Fang of UA. “It’s just weak and non-uniform. But you can design an antigen that is uniform enough to be effective.”
According to Dr. Holger Wille, Director of UA’s Centre for Prions and Protein Folding Diseases, his team used new insights into the structure of prion proteins to engineer their unique vaccine. They took a small set of seven amino acids from the mammal protein and grafted it onto a chain from a harmless fungus protein. The patch made the fungus protein look enough like an infectious CWD prion to trigger a mammal’s immune system – without being infectious.
“It’s one of many first steps. If we hadn’t seen an immune response at all, we wouldn’t be having this conversation.”Dr. Peach Van Wick, Wyoming Game & Fish
A New CWD Vaccine Trial
After seeing positive results in trials with lab mice, UA partnered with Wyoming Game & Fish and the University of Wyoming to vaccinate captive elk at the state’s Thorne/Williams Wildlife Research Center. From August to October 2021, eight of 12 elk were vaccinated (the other four received a placebo as a control) with three boosters at three-week intervals after the first injection.
The vaccinated elk displayed a clear immune response where the control elk did not, said Dr. Peach Van Wick, Assistant State Wildlife Veterinarian with Wyoming Game & Fish. The response remained high throughout the booster series and then declined. By one year after vaccination, the elk had no detectable immune activity compared to the elk that received placebo injections.
“Their immune systems recognized they were vaccinated with something, but it didn’t last,” said Dr. Van Wick. “That helps guide future direction for study to see if we can administer a vaccine in a way that leads to a longer response. We’ll look at vaccine schedule, dose, how it’s administered – in this study it was injected in muscle. They are trying to modify it now so it can be administered through mucous membranes in the nose and mouth. That can produce a different response.
“I wouldn’t say this is a break-through, but it’s positive results and positive things we’ve learned,” said Dr. Van Wick. “It’s one of many first steps. If we hadn’t seen an immune response at all, we wouldn’t be having this conversation.”
Up Next: Testing Whitetails
For several reasons, the elk in the first phase of this study were not “challenged” with actual CWD prion exposure to see if they were protected. That’s part of the next phase of study, which involves whitetails. According to Dr. Wille, researchers will vaccinate a group of whitetails in a facility at Colorado State University and then expose them to CWD prions. The study begins in early 2024.
Which brings us back to the hunter’s role in this work: slowing the spread of CWD in captive and wild deer while scientists pursue clues and new leads from studies like this one. Progress is slow, but it is still progress, and we need more time (and funding) for research. We also need patience while scientists learn more about this slow but certain threat to deer populations.
“It takes a long time,” said Dr. Van Wick. “That’s why it’s called chronic.”