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Mixtures of prion substrains in natural scrapie cases revealed by ovinised murine models
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Edité par CCSD ; Nature Publishing Group -
International audience. Phenotypic variability in prion diseases, such as scrapie, is associated to the existence of prion strains, which are different pathogenic prion protein (PrP Sc ) conformations with distinct pathobiological properties. To faithfully study scrapie strain variability in natural sheep isolates, transgenic mice expressing sheep cellular prion protein (PrP C ) are used. In this study, we used two of such models to bioassay 20 scrapie isolates from the Spain-France-Andorra transboundary territory. Animals were intracerebrally inoculated and survival periods, proteinase K-resistant PrP (PrP res ) banding patterns, lesion profiles and PrP Sc distribution were studied. Inocula showed a remarkable homogeneity on banding patterns, all of them but one showing 19-kDa PrP res . However, a number of isolates caused accumulation of 21-kDa PrP res in TgShp XI. A different subgroup of isolates caused long survival periods and presence of 21-kDa PrP res in Tg338 mice. It seemed that one major 19-kDa prion isoform and two distinct 21-kDa variants coexisted in source inocula, and that they could be separated by bioassay in each transgenic model. The reason why each model favours a specific component of the mixture is unknown, although PrP C expression level may play a role. Our results indicate that coinfection with more than one substrain is more frequent than infection with a single component.
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