Characterization of a US Sheep Scrapie Isolate with Short Incubation Time

National Animal Disease Center, ARS, USDA, Ames, IA, USA.
Veterinary Pathology (Impact Factor: 1.87). 08/2009; 46(6):1205-12. DOI: 10.1354/vp.08-VP-0258-H-FL
Source: PubMed


Scrapie is a naturally occurring fatal neurodegenerative disease of sheep and goats. Susceptibility to the disease is partly dependent upon the genetic makeup of the host. In a previous study it was shown that sheep intracerebrally inoculated with US scrapie inoculum (No. 13-7) developed terminal disease within an average of 19 months. We have since produced an inoculum, No. x124 from pooled brains of US-origin sheep scrapie, that results in incubations nearly threefold shorter. The present study documents clinicopathologic findings and the distribution of abnormal prion proteins (PrP(Sc)) by immunohistochemical (IHC) and Western blot (WB) techniques, in tissues of sheep inoculated with No. x124. All inoculated sheep developed clinical disease and were euthanatized within an average of 7.7 months postinoculation (MPI). Sheep that had valine/valine or alamine/valine at codon 136 of prion protein (PRNP) gene developed the disease faster and were euthanatized at an average of 4.3 and 5.6 MPI, respectively. Also, the inoculum was able to induce disease in a short time (7 MPI) in a sheep that was relatively resistant (QR at codon 171) to scrapie. This indicates that inoculum No. x124 appears to induce scrapie in shorter time than inoculum No. 13-7, especially in sheep homozygous or heterozygous for valine at codon 136.

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Article: Characterization of a US Sheep Scrapie Isolate with Short Incubation Time

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    • "abnormally fine , ' ' sprinkled ' ' accumulation of PrP Sc throughout the affected tissues . Therefore , it is possible that the relationship between diffuse aggregation , low PrP Sc stability , and short incubation times observed in mice [ 34 ] also applies to strains of classical scrapie in the natural host . However , we note that in contrast , Hamir et al . ( 2009 ) did not observe differences in IHC PrP Sc labeling of x124 - infected brain sections of different genotypes ."
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    ABSTRACT: Transmissible spongiform encephalopathies (TSEs), including scrapie in sheep (Ovis aries), are fatal neurodegenerative diseases caused by the misfolding of the cellular prion protein (PrP C) into a â-rich conformer (PrP Sc) that accumulates into higher-order structures in the brain and other tissues. Distinct strains of TSEs exist, characterized by different pathologic profiles upon passage into rodents and representing distinct conformations of PrP Sc . One biochemical method of distinguishing strains is the stability of PrP Sc as determined by unfolding in guanidine hydrochloride (GdnHCl), which is tightly and positively correlated with the incubation time of disease upon passage into mice. Here, we utilize a rapid, protease-free version of the stability assay to characterize naturally occurring scrapie samples, including a fast-acting scrapie inoculum for which incubation time is highly dependent on the amino acid at codon 136 of the prion protein. We utilize the stability methodology to identify the presence of two distinct isolates in the inoculum, and compare isolate properties to those of a host-stabilized reference scrapie isolate (NADC 13-7) in order to assess the stability/incubation time correlation in a natural host system. We demonstrate the utility of the stability methodology in characterizing TSE isolates throughout serial passage in livestock, which is applicable to a range of natural host systems, including strains of bovine spongiform encephalopathy and chronic wasting disease. This is an open-access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.
    PLoS ONE 08/2012; 7(8):e43060. DOI:10.1371/journal.pone.0043060 · 3.23 Impact Factor
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    • "strains such as the SSBP/1 strain reported by Hunter and the X124 ('Caine') strain characterized by Hamir et al. (2009) have much shorter incubation times in VRQ/VRQ and ARQ/VRQ sheep, while showing more traditional incubation times in sheep with ARQ/ARQ genotypes. "
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    ABSTRACT: A scrapie-positive ewe was found in a flock that had been scrapie-free for 13 years, but housed adjacent to scrapie-positive animals, separated by a wire fence. Live animal testing of the entire flock of 24 animals revealed seven more subclinical scrapie-positive ewes. We hypothesized that they may have contracted the disease from scrapie-positive rams used for breeding 4 months prior, possibly through the semen. The genotypes of the ewe flock were highly scrapie-susceptible and the rams were infected with the 'Caine' scrapie strain having a short incubation time of 4.3-14.6 months in sheep with 136/171 VQ/VQ and AQ/VQ genotypes. PrP(Sc) accumulates in a variety of tissues in addition to the central nervous system. Although transmission of prion diseases, or transmissible spongiform encephalopathies, has been achieved via peripheral organ or tissue homogenates as well as by blood transfusion, neither infectivity nor PrP(Sc) have been found in semen from scrapie-infected animals. Using serial protein misfolding cyclic amplification followed by a surround optical fibre immunoassay, we demonstrate that semen from rams infected with a short-incubation-time scrapie strain contains prion disease-associated-seeding activity that generated PrP(Sc) in sPMCA (serial protein misfolding cyclic amplification). Injection of the ovinized transgenic mouse line TgSShpPrP with semen from scrapie-infected sheep resulted in PrP(Sc)-seeding activity in clinical and, probably as a result of the low titre, non-clinical mouse brain. These results suggest that the transmissible agent, or at least the seeding activity, for sheep scrapie is present in semen. This may be a strain-specific phenomenon.
    Journal of General Virology 02/2012; 93(Pt 6):1375-83. DOI:10.1099/vir.0.038802-0 · 3.18 Impact Factor
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    • "One possible explanation of the differences between the two groups would be a certain degree of interference of the methionine polymorphism on the ability of PrPd to accumulate in lymphoid tissues. Thus, it has been shown that sheep homozygous for the VRQ allele have a more extensive and earlier LRS involvement than ARR/VRQ sheep [1, 5, 7, 9, 11, 13, 26], and to a lesser extent than those of the ARQ/VRQ genotype [9, 11, 15, 26]1. "
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    ABSTRACT: After detection of a high prevalence of scrapie in a large dairy goat herd, 72 infected animals were examined by immunohistochemistry with prion protein (PrP) antibody Bar224 to study the pathogenesis of the infection. Tissues examined included the brain and thoracic spinal cord (TSC), a wide selection of lymphoreticular system (LRS) tissues, the distal ileum and its enteric nervous system (ENS), and other organs, including the mammary gland. The whole open reading frame of the PRNP gene was sequenced and antibodies to caprine arthritis-encephalitis virus (CAEV) infection were determined. Unexpectedly, accumulation of disease-associated PrP (PrPd) in the brain was more frequent in methionine carriers at codon 142 (24/32, 75.0%) than amongst isoleucine homozygotes (14/40, 35.0%). The latter, however, showed significantly greater amounts of brain PrPd than the former (average scores of 9.3 and 3.0, respectively). A significant proportion of the 38 goats that were positive in brain were negative in the ENS (44.7%) or in the TSC (39.5%). These results, together with the early and consistent involvement of the circumventricular organs and the hypothalamus, point towards a significant contribution of the haematogenous route in the process of neuroinvasion. Chronic enteritis was observed in 98 of the 200 goats examined, with no association with either scrapie infection or presence of PrPd in the gut. Lymphoproliferative interstitial mastitis was observed in 13/31 CAEV-positive and scrapie-infected goats; PrPd in the mammary gland was detected in five of those 13 goats, suggesting a possible contribution of CAEV infection in scrapie transmission via milk.
    Veterinary Research 04/2010; 41(4):48. DOI:10.1051/vetres/2010020 · 2.82 Impact Factor
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