Environmental Contamination of Plats with Prions

Non-Technical Summary:<br/>
Prion diseases in animals pose a direct threat to food safety and public health. The bovine spongiform encephalopathy (BSE) epidemic of the 1980s and 1990s, for example, infected an estimated one million cattle in the UK, with an cumulative gross budgetary cost of approximately $5 billion between 1996 and 2000. Zoonosis of BSE caused a new variant of Creutzfeldt-Jakob (vCJD) disease in humans following consumption of BSE-contaminated food products and demonstrated that animal prion diseases are capable of crossing the species barrier to infect humans. As of August 2011, 221 cases of vCJD had been reported. Exclusion of prions from products intended for human consumption is required to safeguard public health and retain confidence in the food supply. As chronic wasting disease (CWD) continues to increase in both distribution and prevalence, humans will increasingly be exposed to CWD prions. Human prion disease has not yet been linked to consumption of CWD-infected animal products, but CWD agent has converted human PrPC to an abnormal form in vitro, suggesting the possibility for human infection by CWD exists. The risk that CWD poses to agriculture and the food supply is currently unknown due to incomplete understanding of disease transmission, lack of knowledge regarding the susceptibility of humans to CWD, and a paucity of information on environmental persistence of prions. The discoveries that CWD prions (1) are released into the environment via infectious saliva, blood, urine, feces, and animal mortalities, and (2) can be horizontally transmitted via environmental reservoirs of infectivity after prolonged periods of time (years to decades), suggests prions pose a significant environmental contamination problem now and in the future. The uptake of prions from the environment and into plants may pose a previously unrecognized food safety risk. CWD-infected free-ranging or captive cervids have been found in 19 states, including Wisconsin where the disease negatively impacts not only cervid farming operations, but also the $1.4 billion per year hunting industry. The increasing prevalence and geographical distribution of CWD across North America, coupled with the infectious agent's extraordinary stability and accumulation in the environment, indicates an urgent need to better understand environmental prion disese transmission. The proposed project will provide information on prion uptake in plants and the potential for plant-associated prions to cause disease in mammalian hosts, providing research basic to the problems of agriculture in its broadest aspects. This information will be useful in evaluating the risks posed to crop and livestock production by environmental contamination by prions, thereby facilitating the effective treatment of, and, where possible, prevent animal diseases in both domesticated and wild animals which, if not controlled, would be disastrous to the US livestock industries and endanger the Nation's food supply and ultimately to protect human health through control of animal diseases transmissible to humans.
<P>
Approach:<br/>
We will assess prion uptake in a diversity of plant species and measure prion replication and infectivity in plant tissues. To accomplish this we will test prion uptake by confocal microscopy using fluorescently tagged prion protein, protein misfolding cyclical amplification, and animal bioassay. We will determine the mechanism(s) of prion uptake into plants and plant cells using common plant cell lines or plant-derived cells and treatments that block specific pathways for biomolecule uptake by cells.
<P>
Progress:<br/>
2012/01 TO 2012/12<br/>
OUTPUTS: This project began in October. We have set up plant exposures to prions. We have adapted our detection method method for prion protein in plant extracts.
<br/>PARTICIPANTS: Joel A. Pedersen (principal investigator) - overall supervision of project; Clarissa Booth (graduate research assistant) - trained prospective (rotating) graduate student on techniques relevant for project; Christina Carlson (graduate research assistant) - initiated plant exposures, optimized detection method; Christopher J. Johnson (collaborator, USGS National Wildlife Health Center) - supervision of activities at his facility related to project; Haeyoon Chang (biological science technician, USGS National Wildlife Health Center) - provided laboratory assistance to Carlson.
<br/>TARGET AUDIENCES: Nothing significant to report during this reporting period.
<br/>PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
<P>
IMPACT: Conditions have been identified to allow successful detection of pathogenic prion protein in plant extracts.