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USGS Mendenhall Postdoctoral  Research Fellowship Program

14-36. A broad-spectrum in vitro assay for the detection and characterization of prion diseases

Transmissible spongiform encephalopathies (TSEs; prion diseases) are a family of invariably fatal neurodegenerative diseases which are caused by a misfolded protein, referred to as a prion [1]. Notable TSEs include bovine spongiform encephalopathy (BSE), chronic wasting disease (CWD) of deer, elk and moose (cervids), sheep scrapie, and Creutzfeldt-Jakob disease (CJD) in humans [2]. Animal TSEs have been a major concern to food safety since recognition in the 1990s that BSE can transmit to humans, presumably through consumption of BSE-infected meat. Of present concern to public health and food safety is CWD, the only TSE known to affect free-ranging species (wildlife). In recent years, the known distribution of CWD has spread from a central focus in the Rocky Mountain States to distant locations in 20 U.S. states, two Canadian provinces, and South Korea [3]. The detection of infected animals is central to managing CWD, understanding its epidemiology, and performing effective disease surveillance. Unfortunately, efficient techniques for ante mortem detection of CWD or methods for detection of disease in easily obtained samples (saliva, urine, feces) are lacking.

Recently, we have been investigating the transmission of CWD to meadow and red-backed voles, two native North American rodent species of interest for CWD cross-species transmission studies due to their 1) natural abundance and 2) voracious carcass scavenging behavior [4]. We have found that both vole species are highly susceptible to CWD [4]. In fact, voles are as susceptible to CWD as transgenic mice engineered to express the cervid prion protein [5]. Our findings contribute to a growing body of research demonstrating that vole species are uniquely susceptible to a wide range of TSEs, including CWD, CJD, scrapie, and rodent-adapted TSEs in vivo [6.,7.,8] Voles are hypothesized to be “universal TSE acceptors” and a recent study demonstrated the in vitro misfolding of bank vole prion protein by mouse-, hamster- and vole-adapted scrapie, as well as CWD, BSE, scrapie and CJD [9]. Taken together, these results suggest that voles could be exploited for the development of a multi-species TSE detection assay.

Protein misfolding cyclic amplification (PMCA) is a method that can detect sub-nanogram amounts of infectious prion protein within 48-72 hours by recapitulating prion misfolding in vitro [10]. In previous studies, we used PMCA to detect prions following degradation or to aid in understanding CWD transmission to voles [11., 12.,13]. In preliminary experiments related to this Research Opportunity, we have been using vole tissues and PMCA to detect CWD and CJD.

For this Research Opportunity, we seek a highly-qualified and motivated postdoctoral fellow to establish and utilize PMCA to detect and characterize CWD and other TSEs. Within this broad goal, the Mendenhall Fellow will have wide latitude in determining the specific research questions that best suit their expertise, interests, and long-term goals to which they wish to apply this technology. Some potential directions include, but are not limited to:

  1. Early detection of TSEs in infected hosts: The in vitro assay developed as part of the Fellow’s research should be sensitive enough to detect TSEs in animals prior to the clinical stage of infection with utility for CWD or CJD surveillance. The postdoctoral fellow will also be able to utilize our animal research facility for in vivo infection studies.
  2. Characterizing disease progression of CWD (and other TSEs) in infected hosts: The pathogenesis of CWD and many other TSEs remains poorly elucidated, due in part to lack of assays sensitive enough to detect the low levels of prion protein found in tissues outside the central nervous system. With development of appropriate PMCA procedures, the Mendenhall Fellow will be able to a) determine a more accurate identification of the extent of infectious CWD prion tissue distribution and, b) follow the progression of CWD prions throughout the peripheral tissues of infected hosts toward an improved understanding of CWD pathogenesis.
  3. Detection of CWD in tissue or environmental samples for improved CWD surveillance: The exquisite sensitivity of the proposed assay provides the Mendenhall scientist with opportunities to develop TSE detection tests for bodily fluids easily acquired from infected hosts, but not previously used in diagnostics due to the low levels of infectious prion protein found within them (i.e. urine, saliva, blood). Additional detection tests could be developed for environmental samples, such as soil, water, etc. Such a test would serve an “early-warning” function for prions in a manner similar to eDNA for genome-based organisms.
  4. Characterizing the nature of CWD prions: PMCA is based on conversion of normal prion protein to an abnormal state. As a result, PMCA can be used to investigate the nature of TSEs, including asking questions about prion strains, species barriers, adaptation in new hosts, and determinants of pathogenesis, among others.


1. Colby DW, Prusiner SB (2011) Prions. Cold Spring Harbor perspectives in biology 3: 10.1101/cshperspect.a006833.

2. Watts JC, Balachandran A, Westaway D (2006) The expanding universe of prion diseases. PLoS pathogens 2: e26.

3. Sigurdson CJ (2008) A prion disease of cervids: chronic wasting disease. Veterinary research 39: 41.

4. Heisey DM, Mickelsen NA, Schneider JR, Johnson CJ, Langenberg J, et al. (2010) Chronic wasting disease susceptibility of four North American rodents. Journal of Virology 84: 210-215.

5. Seelig DM, Mason GL, Telling GC, Hoover EA (2010) Pathogenesis of chronic wasting disease in cervidized transgenic mice. Am J Pathol 176: 2785-2797.

6. Agrimi U, Nonno R, Dell'Omo G, Di Bari MA, Conte M, et al. (2008) Prion protein amino acid determinants of differential susceptibility and molecular feature of prion strains in mice and voles. PLoS Pathog 4: e1000113.

7. Di Bari MA, Chianini F, Vaccari G, Esposito E, Conte M, et al. (2008) The bank vole (Myodes glareolus) as a sensitive bioassay for sheep scrapie. J Gen Virol 89: 2975-2985.

8. Nonno R, Di Bari MA, Cardone F, Vaccari G, Fazzi P, et al. (2006) Efficient transmission and characterization of Creutzfeldt-Jakob disease strains in bank voles. PLoS Pathog 2: e12.

9. Cosseddu GM, Nonno R, Vaccari G, Bucalossi C, Fernandez-Borges N, et al. (2011) Ultra-efficient PrP(Sc) amplification highlights potentialities and pitfalls of PMCA technology. PLoS Pathog 7: e1002370.

10. Saa P, Castilla J, Soto C (2006) Ultra-efficient replication of infectious prions by automated protein misfolding cyclic amplification. Journal of biological chemistry 281: 35245-35252.

11. Kurt TD, Seelig DM, Schneider JR, Johnson CJ, Telling GC, et al. (2011) Alteration of the chronic wasting disease species barrier by in vitro prion amplification. Journal of virology 85: 8528-8537.

12. Johnson CJ, Bennett JP, Biro SM, Duque-Velasquez JC, Rodriguez CM, et al. (2011) Degradation of the disease-associated prion protein by a serine protease from lichens. PloS one 6: e19836.

13. Russo F, Johnson CJ, McKenzie D, Aiken JM, Pedersen JA (2009) Pathogenic prion protein is degraded by a manganese oxide mineral found in soils. The Journal of general virology 90: 275-280.

Proposed Duty Station: Madison, WI

Areas of Ph.D.: Molecular Biology, Microbiology, Biochemistry, Virology, Veterinary Sciences, Infectious Diseases (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet one of the following qualifications - Research Biologist, Research Microbiologist.

(This type of research is performed by those who have backgrounds for the occupations stated above. However, other titles may be applicable depending on the applicant's background, education, and research proposal. The final classification of theposition will be made by the Human Resources specialist).

Research Advisor(s): Christopher Johnson, (608) 270-2442,; Dennis Heisey, (608) 270-2478,; Luisa Gregori (U.S. Food and Drug Administration), (301) 827-2852,

Human Resources Office Contact: Junell Norris, (303) 236-9557,

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Last modified: 18:57:12 Tue 23 Jul 2013
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