Project Title: Identifying CWD biomarkers that can be used for development of a rapid field CWD diagnostics test in deer; Investigating the microbiome associated with infection of CWD in white-tailed deer feces
Principal Investigator: Dr. Anna Kashina
Description: CWD belongs to a broader class of prion diseases, caused by accumulation of abnormally misfolded prion proteins. Healthy animals are believed to acquire this disease by oral exposure to infected animal by-products containing misfolded prions, including feces, saliva, urine, and animal remains which are accidentally ingested by the deer in the contaminated environment and are then absorbed through the digestive tract into the body. Once acquired, this disease is lethal, and currently there are no effective therapies and very limited means of diagnostics in live animals.
Our research is focused on identifying novel CWD biomarkers that would enable high throughput field diagnostics of the disease in animal by-products and live animals, as well as, longer term, development of therapeutic approaches that would prevent disease propagation in the wild. To achieve these goals, we are pursuing the following research directions:
1. Identification of microbiomics signatures of CWD.
Gastrointestinal tract represents the primary route of CWD infection. Studies of the past decade have uncovered that uptake of orally ingested products in the body is closely regulated by the gut microbiota, a multi-species population of symbiotic and pathogenic microorganisms normally residing in the intestines of every animal. Gut microbiotas interact with the host animal via exchange of metabolites, as well as exchange in the extracellular vesicles (exosomes) originating from both the host and the microbes.
Based on the available evidence, recent papers propose a direct link between the gut microbiome and the pathogenesis and pathology of prion diseases, but this highly promising field is still in its infancy. Gut microbiome and the composition of extracellular vesicles in the digestive tract can be easily analyzed using feces, which contain a representative sample of bacteria from each individual. Feces are commonly found in natural deer habitats and can be collected without disturbing the environment or coming into dangerous contact with infected animals. Thus, identification of potential feces based diagnostic markers of CWD would provide an excellent tool for disease surveillance and control.
Here, we are conducting a proof-of-concept study to investigate CWD-dependent changes in the gut microbiome as a potential diagnostic marker, as well as an expanded study to use advanced proteomics technologies to identify tissue-based CWD biomarkers in the diseased deer muscle.
2. Identification of novel protein biomarkers of CWD.
Like other prion diseases, CWD pathogenesis arises through changes entirely at the protein level, by misfolding and abnormal accumulation of the native prion proteins in different tissues in the body. While this disease primarily targets the brain, its clinical manifestations are commonly seen in muscle, resulting in muscle wasting and behavioral changes that ultimately lead to death. In addition, other tissues in the body are also affected by prions, which are, e.g., secreted through saliva and bodily fluids. Evidence suggests the presence of prion proteins in the muscle and salivary glands of deer with CWD, but very few studies to date address this possibility. Moreover, no one has ever addressed protein-level changes in the muscle and other tissues during CWD, which may arise as a result of prion accumulation in other tissues in the body.
Our project is aimed to address this critical gap by analyzing the proteome (total protein composition) of tissue biopsies from deer with mild and severe CWD, compared to healthy controls. We are currently analyzing the muscle, by performing comparative quantification of different proteins in the diseased and healthy deer muscle and analyzing potential modifications of these proteins that can serve as markers of CWD. Our longer term plans involve adding other tissues to this list, starting with those that carry the highest potential of live animal diagnostics.
Dr. Anna Kashina is a Professor of Biochemistry at the School of Veterinary Medicine, University of Pennsylvania, with a broad research focus on the biology of neurodegeneration through posttranslational protein regulation and cytoskeleton-dependent vesicle transport (including secretion of extracellular vesicles).
