Molecular characterisation of atypical BSE prions by mass spectrometry and changes following transmission to sheep and transgenic mouse models.

Adriana Gielbert,Jane M Plater,Marion M Simmons,Leigh Thorne,Jemma K Thorne,Claire A Cassar,Peter C Griffiths,Human Rezaei

doi:10.1371/journal.pone.0206505

Adriana Gielbert, Jane M Plater + Show 6 more

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https://doi.org/10.1371/journal.pone.0206505

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Journal: PloS one	Publication Date: Nov 8, 2018
Citations: 2	License type: CC BY 4.0

Affiliation: Animal and Plant Health Agency

Abstract

The prion hypothesis proposes a causal relationship between the misfolded prion protein (PrPSc) molecular entity and the disease transmissible spongiform encephalopathy (TSE). Variations in the conformation of PrPSc are associated with different forms of TSE and different risks to animal and human health. Since the discovery of atypical forms of bovine spongiform encephalopathy (BSE) in 2003, scientists have progressed the molecular characterisation of the associated PrPSc in order to better understand these risks, both in cattle as the natural host and following experimental transmission to other species. Here we report the development of a mass spectrometry based assay for molecular characterisation of bovine proteinase K (PK) treated PrPSc (PrPres) by quantitative identification of its N-terminal amino acid profiles (N-TAAPs) and tryptic peptides. We have applied the assay to classical, H-type and L-type BSE prions purified from cattle, transgenic (Tg) mice expressing the bovine (Tg110 and Tg1896) or ovine (TgEM16) prion protein gene, and sheep brain. We determined that, for classical BSE in cattle, the G96 N-terminal cleavage site dominated, while the range of cleavage sites was wider following transmission to Tg mice and sheep. For L-BSE in cattle and Tg bovinised mice, a C-terminal shift was identified in the N-TAAP distribution compared to classical BSE, consistent with observations by Western blot (WB). For L-BSE transmitted to sheep, both N-TAAP and tryptic peptide profiles were found to be changed compared to cattle, but less so following transmission to Tg ovinised mice. Relative abundances of aglycosyl peptides were found to be significantly different between the atypical BSE forms in cattle as well as in other hosts. The enhanced resolution provided by molecular analysis of PrPres using mass spectrometry has improved insight into the molecular changes following transmission of atypical BSE to other species.

Highlights

Classical bovine spongiform encephalopathy (C-BSE) is a prion disease of cattle, first described in 1986 [1, 2], and identified by subsequent epidemiological studies as an extended common source epidemic linked to meat and bone meal in cattle feed following changes to rendering practices [3]
When we first applied the mass spectrometry (MS)-based assay to quantify bovine proteinase K (PK) treated PrPSc (PrPres) peptides prepared from C-BSE infected brain stem, we found that the absolute peptide abundances obtained from bovine tissue were much lower compared to equivalent amounts of ovine tissue [35]
The aims of the present study were (1) to establish the N-terminal amino acid and tryptic peptide profiles of classical and atypical BSE in cattle and identify any differences between them, and (2) to determine any changes in these profiles following transmission of each of the BSE types into the bovine (Tg bov) (Tg110 and Tg1896), and Tg ov (TgEM16) mice, and into sheep, as homologous and heterologous hosts used to determine the stability of these transmissible spongiform encephalopathy (TSE)

Summary

Introduction

Classical bovine spongiform encephalopathy (C-BSE) is a prion disease of cattle, first described in 1986 [1, 2], and identified by subsequent epidemiological studies as an extended common source epidemic linked to meat and bone meal in cattle feed following changes to rendering practices [3]. Systematic active surveillance for transmissible spongiform encephalopathy (TSE) in cattle and small ruminants was introduced across the EU. This intensive scrutiny led to atypical forms of BSE being identified in cattle. Under experimental circumstances, both atypical BSE types (H-BSE and L-BSE) are transmissible to a range of species, a hypothetical risk to the food and feed chains remains. While the zoonotic potential of this novel TSE phenotype has not been established, the precautionary principle entails that the current measures to protect the food chain from TSEs need to be maintained indefinitely [23]

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