title: Intraspecies prion transmission results in selection of sheep scrapie strains.
abstract: BACKGROUND
  Sheep scrapie is caused by multiple prion strains, which have been classified on the basis of their biological characteristics in inbred mice. The heterogeneity of natural scrapie prions in individual sheep and in sheep flocks has not been clearly defined.
  
  
  RESULTS
  In this study, we intravenously injected 2 sheep (Suffolk and Corriedale) with material from a natural case of sheep scrapie (Suffolk breed). These 3 sheep had identical prion protein (PrP) genotypes. The protease-resistant core of PrP (PrPres) in the experimental Suffolk sheep was similar to that in the original Suffolk sheep. In contrast, PrPres in the Corriedale sheep differed from the original PrPres but resembled the unusual scrapie isolate, CH1641. This unusual PrPres was not detected in the original sheep. The PrPres distributions in the brain and peripheral tissues differed between the 2 breeds of challenged sheep. A transmission study in wild-type and TgBoPrP mice, which overexpressing bovine PrP, led to the selection of different prion strains. The pathological features of prion diseases are thought to depend on the dominantly propagated strain.
  
  
  CONCLUSIONS
  Our results indicate that prion strain selection occurs after both inter- and intraspecies transmission. The unusual scrapie prion was a hidden or an unexpressed component in typical sheep scrapie.
authors.affiliation: Prion Disease Research Center, National Institute of Animal Health, Tsukuba, Japan. tyoko@affrc.go.jp
authors.forename: Takashi
authors.initials: T
authors.lastname: Yokoyama
authors.forename: Kentaro
authors.initials: K
authors.lastname: Masujin
authors.forename: Mary Jo
authors.initials: MJ
authors.lastname: Schmerr
authors.forename: Yujing
authors.initials: Y
authors.lastname: Shu
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Okada
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Iwamaru
authors.forename: Morikazu
authors.initials: M
authors.lastname: Imamura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Matsuura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Murayama
authors.forename: Shirou
authors.initials: S
authors.lastname: Mohri
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000378:metabolism* / Q000473:pathology; D002417:Cattle; D007150:Immunohistochemistry; D051379:Mice; D008813:Mice, Inbred ICR; D018620:PrPSc Proteins / Q000235:genetics / Q000378:metabolism; D011328:Prions / Q000235:genetics / Q000378:metabolism*; D012608:Scrapie / Q000235:genetics / Q000378:metabolism* / Q000635:transmission*; D012756:Sheep; D013045:Species Specificity
chemical_list: D018620:PrPSc Proteins; D011328:Prions