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Clinical and Vaccine Immunology, January 2007, p. 36-43, Vol. 14, No. 1
1071-412X/07/$08.00+0     doi:10.1128/CVI.00341-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Test for Detection of Disease-Associated Prion Aggregate in the Blood of Infected but Asymptomatic Animals

Institute of Pathology School of Medicine, Case Western Reserve University, Cleveland, Ohio 44107-1712,¹ Department of Pathology and Laboratory Medicine, School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6082,² Modern Virology Research Center, State Key Laboratory of Virology, College of Life Science, Wuhan University, Wuhan 430072, China,³ Wildlife Health Program, Colorado Division of Wildlife, Wildlife Research Center, 317 West Prospect Road, Fort Collins, Colorado 80526-2097,⁴ Department of Neurology, Psychiatry and Pathology, New York University School of Medicine, New York, New York 10016⁵

Received 19 September 2006/ Returned for modification 23 October 2006/ Accepted 25 October 2006

We have developed a sensitive in vitro assay for detecting disease-associated prion aggregates by combining an aggregation-specific enzyme-linked immunosorbent assay (AS-ELISA) with the fluorescent amplification catalyzed by T7 RNA polymerase technique (FACTT). The new assay, named aggregation-specific FACTT (AS-FACTT), is much more sensitive than AS-ELISA and could detect prion aggregates in the brain of mice as early as 7 days after an intraperitoneal inoculation of PrP^Sc. However, AS-FACTT was still unable to detect prion aggregates in blood of infected mice. To further improve the detection limit of AS-FACTT, we added an additional prion amplification step (Am) and developed a third-generation assay, termed Am-A-FACTT. Am-A-FACTT has 100% sensitivity and specificity in detecting disease-associated prion aggregates in blood of infected mice at late but still asymptomatic stages of disease. At a very early stage, Am-A-FACTT had a sensitivity of 50% and a specificity of 100%. Most importantly, Am-A-FACTT also detects prion aggregates in blood of mule deer infected with the agent causing a naturally occurring prion disease, chronic wasting disease. Application of this assay to cattle, sheep, and humans could safeguard food supplies and prevent human contagion.

Published ahead of print on 1 November 2006.

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