MADISON – With the help of three grants from the Department of Defense (DOD), researchers from the University of Wisconsin-Madison will delve deeper into a molecular and environmental understanding of chronic wasting disease (CWD).
The research will investigate genetic variations of the disease among deer, the transmission of CWD to other species, the contamination of soil with the infectious agent and the biological markers that occur early in CWD infection, possibly leading to the development of a live animal test.
“There’s so much we don’t know and so much that’s needs to be done,” says Judd Aiken, professor of animal health and biomedical sciences in UW-Madison’s School of Veterinary Medicine and lead investigator on two of the new grants. “Saying we’re excited about the opportunity to do these studies is an understatement.”
The first study, funded by a five-year, $2.3 million grant, builds upon earlier work initiated by UW-Madison researchers to characterize the biology of CWD and an animal’s genetic susceptibility to the disease. Led by Debbie McKenzie, the researchers will work with tissue samples taken from both infected and uninfected deer to identify differences in the prion protein gene. Abnormally folded prion proteins are known to cause CWD and other similar neurological diseases, or transmissible spongiform encephalopathies (TSEs).
“Different forms of the prion protein have different characteristics,” explains McKenzie. These differences, she adds, can alter the disease’s incubation period, its clinical signs and its ability to spread to other animals and even jump the species barrier.
After identifying the different prion proteins implicated in CWD, the team, in collaboration with Glenn Telling at the University of Kentucky, will test people’s potential genetic susceptibility to the disease by working with mice expressing the human prion protein gene.
The second study, funded by a three-year, $541,815 grant, will create a molecular portrait of changes in biological markers, such as protein or RNA levels, as prion infection progresses in animals. Identifying these changes, says primary investigator Aiken, could lead to the development of rapid and sensitive early detection techniques that could be performed safely and easily on live animals.
The third study, funded by a five-year, $2.4 million grant, moves beyond the molecular to the environmental – it turns to the landscape, including both the animals living on it and the soil to understand how the disease could spread.
“We know that wild deer are dying from CWD. Unless they’re removed, other animals come into contact with the infected carcasses,” explains Aiken. “Little is known about whether the disease can be transmitted this way.”
One component of this third study is determining if the animals that share the same territory as deer or feed off their remains can harbor the abnormal prion proteins known to cause CWD. To do this, the researchers will infect raccoons, skunks, opossums, mice and rats with the CWD agent.
Aiken notes that all animals involved in the disease transmission studies are housed in highly monitored and isolated biological containment units provided by the UW-Madison School of Veterinary Medicine.
The second component of this study will focus on understanding the role soil might play in CWD transmission.
Circumstantial evidence suggests that soil may serve as a reservoir for infectious prions, which are difficult to inactivate. But, as UW-Madison environmental chemist Joel Pedersen clarifies, “Very little is actually known about how prions behave in different soil types.”
Pedersen, Aiken and others will study how different soil components and conditions affect the persistence of prion proteins in the landscape, as well as how they travel through it via processes such as leaching.
The UW-Madison research projects are funded by the DOD’s National Prion Research Program (NPRP), which was established last year by Congress to promote research in TSEs. The program arose from concerns over the threat that prion diseases, such as mad cow disease, pose to the national food and blood supply, as well as those supplies serving American military stationed abroad. The program is administered by the U.S. Army Medical Research and Materiel Command’s Office of the Congressionally Directed Medical Research Programs (http://cdmrp.army.mil).
The federal support of these three new UW-Madison studies, Aiken says, will go a long way toward answering fundamental questions about CWD in deer and elk, as well as other species. “Historically, CWD research has not been funded – there’s not a lot of emphasis on studying wildlife diseases,” he explains. “To get three grants like these is really an honor.”