A new method for studying prion diversity has been developed by noting the molecular features of a specifc type of sheep scrapie, according to an article published on August 28, 2008 in the open access journal PLoS Pathogens.

A prion is an agent of infection that is composed entirely of protein. This makes it unusual in that it contains no DNA, which life-forms such as bacteria and animals need to function properly. Well known examples of prion diseases are Creutzfeldt-Jakob disease (CJD) and bovine spongiform encephalopathy (BSE), which is often called mad cow disease. The presence of this agent causes a buildup of a specific protein, called protease-resistant prion protein (PrPres) in the brain because is is no longer properly degraded.

While the origin of BSE has not yet been determined, scientists believe that it is a variant of CJD that resulted from the recycling of a specific type of BSE, called bovine amyloidotic spongiform encephalopathy (L-type BSE), through an intermediate host like a sheep. One key to elucidating this explanation involves the examination of a similar disease in sheep, known as scrapie.

Thierry Baron, leading a team from the French Food Safety Agency, Lyon, France, examined the specific molecular characteristics of PrPres in cases of scrapie and compared them to PrPres in BSE cases. This was done by infecting transgenic mice with the appropriate prion (either BSE, L-type BSE, or ovine/sheep scrapie) and sampling the resulting accumulated PrPres from their brains. The proteins were analyzed by Western blot as well as for glycosylation status.

Specifically, scrapie cases tended to include rare ‘CH1641-like” portions, which are similar in some ways to both BSE and L-type BSE. The features of this protein more closely resembled those of the L-type BSE in comparison to the classical BSE. However, important differences were found in the C-terminal end of the protein chain, which differentiated the two proteins.

In future studies, protein obtained from sheep who have been infected with the L-type BSE should be examined, as they were not used in this study. However, understanding how these proteins are similar and different could help scientists understand prions as they pass from one species to another.

A C-Terminal Protease-Resistant Prion Fragment Distinguishes Ovine”CH1641-Like” Scrapie from Bovine Classical and L-Type BSE in Ovine Transgenic Mice.
Baron T, Bencsik A, Vulin J, Biacabe A-G, Morignat E, et al.
PLoS Pathog 4(8): e1000137.
doi:10.1371/journal.ppat.1000137
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Written by Anna Sophia McKenney