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Title: Classical natural ovine scrapie prions are detected in practical volumes of blood by lamb and transgenic mouse bioassay

item DASSANAYAKE, ROHANA - Washington State University
item Truscott, Thomas
item Zhuang, Dongyue
item Schneider, David
item MADSEN-BOUTERSE, SALLY - Washington State University
item YOUNG, ALAN - South Dakota State University
item STANTON, JAMES - Washington State University
item DAVIS, WILLIAM - Washington State University
item O’ROURKE, KATHERINE - Washington State University

Submitted to: Journal of Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/4/2014
Publication Date: 6/30/2015
Citation: Dassanayake, R.P., Truscott, T.C., Zhuang, D., Schneider, D.A., Madsen-Bouterse, S.A., Young, A.J., Stanton, J.B., Davis, W.C., O’Rourke, K.I. 2015. Classical natural ovine scrapie prions are detected in practical volumes of blood by lamb and transgenic mouse bioassay. Journal of Veterinary Science. 16(2):179-186.

Interpretive Summary: Classical scrapie is a naturally occurring fatal disease of sheep and goats caused by prions, a novel class of infectious agent. Presently, diagnosis in live animals is limited to detecting a disease-associated form of prion protein in lymphoid tissues accessible to biopsy. Recent studies demonstrate that the infectious agent, the scrapie prion, can be detected within the blood of sheep, suggesting the blood may be a suitable sample upon which to develop a new live animal test. Those studies, however, used fairly large volumes of blood. Thus, as a first step toward development, we determined that scrapie prions can be reliably detected in smaller blood-sample volumes commonly used in other diagnostic tests. Further, scrapie prions were reliably detected in these sample volumes even when collected from sheep during early clinical disease. These findings support the goal of developing a reliable live-animal test for scrapie disease in sheep that is based on a practical blood-sample volume.

Technical Abstract: In vitro ligand-based immunoassay studies revealed abnormal isoforms of prion protein (PrP-Sc) are primarily associated with B lymphocytes of scrapie-infected sheep. Our recent study also demonstrated efficient transmission of scrapie to lambs following a transfusion of B lymphocytes isolated from 50 mL of blood from scrapie-infected sheep. The optimal number of B lymphocytes required to detect PrP-Sc in an ELISA platform was 10 million, while the absorbance using less than five million cells was indistinguishable from samples from scrapie-uninfected sheep. Therefore, the objective of this study was to identify whether B lymphocytes isolated from volumes of blood suitable for routine diagnostic assays harbors prion-infectivity. Lambs and Tg338 mice developed evidence of scrapie-infection following a single administration of B lymphocytes (1.5-5 million) isolated from 5-10 mL of blood from scrapie-infected sheep. This study confirms scrapie-infectivity from B lymphocytes isolated from practical volumes of scrapie-infected sheep blood that are suboptimal for the ELISA platform. These findings emphasize the need for precautions when interpreting scrapie negative ELISA results.