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Leading the hunt

  • Drs. Jason Bartz, Tiffany Wolf, Peter Larsen, Qi Yuan, Diana Karwan, and Marc Schwabenlander.

    Leading the hunt

    In an effort to find and control chronic wasting disease, a University of Minnesota center is forging the path.

    Drs. Jason Bartz, Tiffany Wolf, Peter Larsen, Qi Yuan, Diana Karwan, and Marc Schwabenlander. The researchers, part of the Minnesota Center for Prion Research and Outreach, are helping to advance understanding of chronic wasting disease. 

A cadre of scientists, standing at the tailgate of a pickup on the edge of a country road, put the finishing touches on their sub sandwiches and went over the day’s plan before zipping themselves into Tyvek suits and heading into the woods. It was late September in northern Minnesota, the sun was shining, and it was unseasonably warm. Nearby, chronic wasting disease (CWD) had been detected in that part of the state for the first time.

The always-fatal neurodegenerative disease, affecting animals in the deer family, is exceedingly difficult to track in real time for a couple of reasons. First, deer, particularly wild deer, will likely die from a hunter’s rifle, a four-legged predator, or a vehicle’s grill before they ever display the telltale signs of a body wasting away—which can take up to two years or more.

Second, official testing for the misfolded protein that causes the disease, called a prion, remains restricted to federally approved labs—and to certain lymphoid and nervous tissues only extractable after a deer’s death. By then, an infected deer had been shedding infectious prions through saliva, urine, and feces, passing them directly to other deer or into the environment for other deer to walk by and pick up.

MNPRO researchers prepare to collect samples
MNPRO researchers prepare to collect samples they would later test
​​​​​with RT-QuIC technology.

Prions are stubborn: They don’t contain genetic material, so they technically aren’t alive. They can remain infectious outside of a deer’s body for years, and can only be destroyed by harsh chemicals or temperatures of more than 1,000 degrees fahrenheit. When the misfolded protein first enters a deer’s system, it starts by grabbing a regular protein and convincing it to misfold. Each newly converted protein then converts another until, over time, the prions spread throughout the body and reach the central nervous system, wreaking debilitating havoc.

The result is a highly infectious disease that poses a threat to the livelihood of Minnesota’s deer farmers, the state’s deeply entrenched and economically robust hunting heritage, and the animals themselves. To control the disease would be to mitigate that threat, but to control it requires understanding where it is and how it moves.

And that’s why, on this day, the collection of scientists trekking into the northern Minnesota pine and aspen included wildlife and molecular biologists, epidemiologists, hydrologists, and prion experts—who were eager to seize the rare opportunity to look for prions in an environment where they were known to exist.

They were all a part of the Minnesota Center for Prion Research and Outreach (MNPRO), an action-oriented think tank assembled by University of Minnesota scientists to develop and share knowledge in service of their mission to tamp down CWD and other protein misfolding diseases like Alzheimer’s and Parkinson’s.

If we’re going to fight the war against CWD we have to know where the enemy is

Peter Larsen

The group is led by evolutionary biologist Peter Larsen, wildlife epidemiologist Tiffany Wolf, and wildlife disease specialist Marc Schwabenlander—all in the College of Veterinary Medicine—and nanotechnology expert ​​Sang-Hyun Oh, in the College of Science and Engineering. The minds they’ve assembled at MNPRO include researchers and wildlife managers from the University and throughout the country.

“If we’re going to fight the war against CWD we have to know where the enemy is,” said Larsen, who that day would lead a team surveying and sampling the landscape where the positive CWD samples had been discovered. Another team, led by Wolf and prion expert Jason Bartz, of Creighton University, would lead a ‘negative control’ team grabbing soil and leaf samples from a parcel of state land to the south and west.

They would later run the samples through technology called real-time quaking-induced conversion (RT-QuIC), which rapidly shakes samples mixed with a synthesized protein substrate. If a sample contains the infectious prion, the quaking will cause the prion to multiply and, over a relatively brief period of time, display its replication in the form of colorful ink blots.

Funding from the state of Minnesota, including from the Environment and Natural Resources Trust Fund through the Legislative-Citizen Commission on Minnesota Resources, has given MNPRO researchers the opportunity to test all sorts of deer-tissue and environmental samples via RT-QuIC. The results have been promising. In the past year they’ve published a number of papers detailing their findings and showing RT-QuIC is equal to or more sensitive and accurate when testing deer tissues than current federally approved tests.

Drs. Tiffany Wolf and Qi Yuan log soil samples in the field.
Drs. Tiffany Wolf and Qi Yuan log soil samples
in the field.

Their findings in deer include the detection of the disease-causing prions in multiple lymphoid and nervous tissues, in feces and blood, and in consumable muscle tissue like tenderloin and backstrap. (CWD has not been found to jump species to humans, but the U.S. Food and Drug Administration and the Department of Agriculture (USDA) recommend against consuming venison from known CWD-infected deer.) The researchers are discovering the infectious prions can transfer directly from deer saliva or snot to surfaces like steel and glass, which they’ve confirmed via RT-QuIC.

The group has created 3D-printed deer heads that teach hunters and others how to remove medial retropharyngeal lymph nodes and brainstem, approved tissues for official testing. They’ve created animated videos and developed presentations designed to convey their research in plain language so stakeholders can easily understand the nuances of CWD.

And the MNPRO team has developed an RT-QuIC-like assay in close collaboration with Oh, which uses nanoparticles to identify CWD prions in tissue samples and generates a color change of red for positive and blue for negative. They’ve called it MN-QuIC™, and in March 2021 successfully deployed it at a field station for the first time. The test is less expensive to run than federally approved CWD tests, and it generates results in less than 24 hours.

MNPRO’s collaboration has expanded beyond the state’s borders. In fact, the group is playing a key role in helping to usher along the federal validation process for RT-QuIC. In response to a need identified by partners in the national CWD Research Consortium, MNPRO leveraged its unique resources to create and manufacture at broad scale an ideal substrate required by RT-QuIC for CWD testing. The USDA is now using the substrate, a recombinant protein called MNPROtein, in an effort to determine whether it will validate RT-QuIC as an approved diagnostic tool.

“To move RT-QuIC into a diagnostic setting, having all of the (research groups) using the same source of recombinant protein was identified as critical, since standardization of this reagent can allow for more consistent results between research groups,” Bartz said. “I think this will accelerate the use of RT-QuIC as a validated diagnostic test.

“I think that MNPRO adds a tremendous amount to CWD research. They are a multidisciplinary team of talented scientists all working towards a common goal. They are bringing new ideas to the field and have improved existing technologies.”

Ultimately, what hunters, deer farmers, wildlife managers, and epidemiologists want is control of the disease. That will require spotting and tracking it in real time via field, and in some cases live-animal, testing. MNPRO’s research, and that from a handful of other labs actively researching CWD and RT-QuIC, shows RT-QuIC technology could be a game-changer that ushers in a new era of CWD diagnostics and surveillance.

Dr. Jason Bartz, of Creighton University, retrieves a soil sample
Dr. Jason Bartz, of Creighton University, retrieves
a soil sample to test for the presence of prions,
the agent causing chronic wasting disease.

“We’re leveraging robust, cutting-edge technology to test samples that aren’t routinely surveyed for CWD, and confirming our findings with a widely-accepted test that’s been used to diagnose CWD for decades,” Larsen said. “We hope our research will ultimately help bolster the state’s CWD management efforts.”

On the way back from the woods, Schwabenlander and Bartz discussed the challenges CWD poses from both a detection and public-understanding standpoint. “It’s a scary thing for people who care about deer to not know much about this disease, which is devastating,” Schwabenlander said. “We do our best to convey what we know—something that is ever changing—and hope it has an impact.”

They were headed to a local high school to facilitate, along with State of Minnesota partners, a town hall forum in furtherance of their outreach mission—and their commitment to getting ahead of the disease. Many in the audience were hunters.

“How do we test the deer we kill?” one asked. A state official detailed the process—which includes driving the carcass to a test site, where a state employee would remove lymph nodes and later send them to one of the two approved testing facilities in Minnesota. Results would come back in a week or more.

With MNPRO’s help, a week or more can become a couple of days—and maybe hours.

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