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From: TSS ()
Subject: Accumulation of prion protein in the brain that is not associated with transmissible disease
Date: March 9, 2007 at 9:13 am PST

Published online before print March 6, 2007
Proc. Natl. Acad. Sci. USA, 10.1073/pnas.0609241104


Accumulation of prion protein in the brain that is not associated with transmissible disease
( amyloid | Gerstmann-Sträussler-Scheinker | transmissible spongiform encephalopathy | neurodegeneration )

Pedro Piccardo *, Jean C. Manson , Declan King , Bernardino Ghetti , and Rona M. Barron
*Center for Biologics Evaluation and Research, Food and Drug Administration, Rockville, MD 20852; Indiana Alzheimer Disease Center and Division of Neuropathology, Indiana University School of Medicine, Indianapolis, IN 46202; and Neuropathogenesis Unit, Institute for Animal Health, Ogston Building, West Mains Road, Edinburgh EH9 3JF, United Kingdom

Edited by Charles Weissmann, The Scripps Research Institute, Jupiter, FL, and approved January 16, 2007 (received for review October 19, 2006)

Prion diseases or transmissible spongiform encephalopathies are characterized histopathologically by the accumulation of prion protein (PrP) ranging from diffuse deposits to amyloid plaques. Moreover, pathologic PrP isoforms (PrPSc) are detected by immunoblot analysis and used both as diagnostic markers of disease and as indicators of the presence of infectivity in tissues. It is not known which forms of PrP are associated with infectivity. To address this question, we performed bioassays using human brain extracts from two cases with phenotypically distinct forms of familial prion disease (Gerstmann-Sträussler-Scheinker P102L). Both cases had PrP accumulations in the brain, but each had different PrPSc isoforms. Only one of the brains had spongiform degeneration. Tissue from this case transmitted disease efficiently to transgenic mice (Tg PrP101LL), resulting in spongiform encephalopathy. In contrast, inoculation of tissue from the case with no spongiform degeneration resulted in almost complete absence of disease transmission but elicited striking PrP-amyloid deposition in several recipient mouse brains. Brains of these mice failed to transmit any neurological disease on passage, but PrP-amyloid deposition was again observed in the brains of recipient mice. These data suggest the possible isolation of an infectious agent that promotes PrP amyloidogenesis in the absence of a spongiform encephalopathy. Alternatively, the infectious agent may be rendered nonpathogenic by sequestration in amyloid plaques, or PrP amyloid can seed amyloid accumulation in the brain, causing a proteinopathy that is unrelated to prion disease. Formation of PrP amyloid may therefore not necessarily be a reliable marker of transmissible spongiform encephalopathy infectivity.


Author contributions: P.P., J.C.M., B.G., and R.M.B. designed research; P.P., D.K., and R.M.B. performed research; P.P., J.C.M., B.G., and R.M.B. analyzed data; and P.P., J.C.M., B.G., and R.M.B. wrote the paper.

The authors declare no conflict of interest.

To whom correspondence should be addressed.

Rona M. Barron, E-mail:


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