Overexpression of chimeric murine/ovine PrP (A136H154Q171) in transgenic mice facilitates transmission and differentiation of ruminant prions
Peter C. Griffiths1, Jane M. Plater, Alun Chave, Dhanushka Jayasena, Anna C. Tout, Paul B. Rice, Christopher M. Vickery, John Spiropoulos, Michael J. Stack and Otto Windl + Author Affiliations
Animal Health and Veterinary Laboratories Agency ↵1 E-mail: email@example.com Received 14 January 2013. Accepted 3 June 2013.
Development of transgenic mouse models expressing heterologous prion proteins (PrP) has facilitated and advanced in vivo studies of prion diseases affecting humans and animals. Here, novel transgenic mouse lines expressing a chimeric murine/ovine (Mu/Ov) PrP transgene, including amino acid residues alanine, histidine and glutamine at ovine polymorphic codons 136, 154 and 171 (A136H154Q171), were generated to provide a means of assessing the susceptibility of the OvPrPAHQ allele to ruminant prion diseases in an in vivo model. Transmission studies showed that the highest level of transgene overexpression, in Tg(Mu/OvPrPAHQ)EM16 mice, conferred high susceptibility to ruminant prions. Highly efficient primary transmission of atypical scrapie from sheep was shown, irrespective of donor sheep PrP genotype, with mean incubation periods (IPs) of 154-178 days post-inoculation (dpi), 100% disease penetrance, and early Western blot detection of protease-resistant fragments (PrPres) of the disease-associated isoform, PrPSc, in Tg(Mu/OvPrPAHQ)EM16 brain from 110 dpi onwards. Tg(Mu/OvPrPAHQ)EM16 mice were also highly susceptible to classical scrapie and BSE, with mean IPs 320 and 246 days faster, respectively, than wild-type mice. Primary passage of atypical scrapie, classical scrapie and BSE showed that the PrPres profiles associated with disease in the natural host were faithfully maintained in Tg(Mu/OvPrPAHQ)EM16 mice and were distinguishable based on molecular masses, antibody reactivities and glycoform percentages. Immunohistochemistry was used to confirm PrPSc deposition in brain sections from terminal phase TSE-challenged Tg(Mu/OvPrPAHQ)EM16 mice. The findings indicate that Tg(Mu/OvPrPAHQ)EM16 mice represent a suitable bioassay model for detection of atypical scrapie infectivity and offer the prospect of differentiation of ruminant prions.
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