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United States Department of Agriculture

Agricultural Research Service

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2012 Annual Report

1a. Objectives (from AD-416):
We will develop highly sensitive diagnostic tests to detect transmissible spongiform encephalopathy (TSE) in livestock and wildlife animal species prior to the onset of clinical disease. We will also develop tests to confirm the presence or absence of TSE disease agents in ingredients of animal origin and decontaminated environments.

1b. Approach (from AD-416):
The threat of BSE continues to affect export economics for US meat. Meanwhile scrapie continues to influence sheep profits and herd biosecurity, and CWD is spreading throughout North America. Thus U.S. animal industry stakeholders have identified detection of the TSE infectious agent (prions) as a priority biosecurity research issue essential for prevention of TSE diseases. We will build on our previous successes using mass spectrometry (MS) for high-sensitivity and specificity in detection of PrPsc as a marker for TSE infectivity in blood using a hamster scrapie model. We will also develop a novel PrP-null mouse strain and related myeloma cell culture system for production of monoclonal antibodies (MAb), which may be specific for PrPsc. We will then choose MS or MAb and validate our novel diagnostic for preclinical diagnosis of scrapie in sheep blood. Whereas MS and MAb methods rely on dissolved samples, contamination of agricultural products and environmental surfaces is associated with solid samples. So we will produce a cell culture based assay for TSE infectivity that is surface-adsorbed. After using the relatively convenient hamster model for early development, we will validate this technology for detection of scrapie in sheep brain on meat-and-bone meal and stainless steel. All work with infectious material will take place within our APHIS-approved BL2 biocontainment facilities labs at the Western Regional Research Center (WRRC), while mass spectrometry will be performed on non-infectious material under BL1 containment.

3. Progress Report:
Transmissible spongiform encephalopathies (TSEs) are caused by mis-folded prion proteins that infect animals and contaminate their byproducts. TSEs represent a threat to agricultural livestock populations, global economic trade and human health. Diagnosis of TSE diseases as part of USDA animal surveillance efforts are confounded by the slow accumulation of the prion protein in the brain, late onset of clinical disease symptoms and multiple prion protein conformations. ARS scientist in Albany, California along with multi-institutional academic partners have generated novel anti-prion monoclonal antibodies and developed sensitive prion immunoassays that exploit the biochemical enrichment of prion protein with lipids and amplification of prions by cells in culture. To distinguish the multiple strains of mis-folded prions responsible for a range of TSE diseases ARS scientists in Albany, California along with their European colleagues have developed sample preparation methods that use chemical modification to uniquely tag prion strains. These chemical tags have been used to distinguish prion strain type by immunoassay and mass spectrometry. We have patented, published and transferred this technology to our USDA-APHIS partners and have established relationships with industrial partners for potential commercialization of these prion immunoassays.

4. Accomplishments

Review Publications
Sajnani, G., Silva, C.J., Ramos, A., Pastrana, M.A., Onisko, B.C., Erickson-Beltran, M.L., Antaki, E.M., Sigurdson, C.J., Carter, J.M., Requena, J.R. 2012. PK-sensitive PrPSc is infectious and shares basic structural features with PK-resistant PrPSc. PLoS Pathogens. 8(3):e1002547. doi:10.1371/journal.ppat.1002547.

Silva, C.J. 2012. Using small molecule reagents to selectively modify epitopes based on their conformation. Prion. 6:(2)165-175.

Ching, K.H., Lin, A.V., Mcgarvey, J.A., Stanker, L.H., Hnasko, R.M. 2012. Rapid and selective detection of botulinum neurotoxin serotypes-A and –B with a single immunochromatographic test strip. Journal of Immunological Methods. 380:23-29.

Last Modified: 10/20/2017
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