Transmissibility of caprine scrapie in ovine transgenic mice

Abstract

BackgroundThe United States control program for classical ovine scrapie is based in part on the finding that infection is typically spread through exposure to shed placentas from infected ewes. Transmission from goats to sheep is less well described. A suitable rodent model for examining the effect of caprine scrapie isolates in the ovine host will be useful in the ovine scrapie eradication effort. In this study, we describe the incubation time, brain lesion profile, glycoform pattern and PrPSc distribution patterns in a well characterized transgenic mouse line (Tg338) expressing the ovine VRQ prion allele, following inoculation with brain from scrapie infected goats.ResultsFirst passage incubation times of caprine tissue in Tg338 ovinized mice varied widely but second passage intervals were shorter and consistent. Vacuolation profiles, glycoform patterns and paraffin-embedded tissue blots from terminally ill second passage mice derived from sheep or goat inocula were similar. Proteinase K digestion products of murine tissue were slightly smaller than the original ruminant inocula, a finding consistent with passage of several ovine strains in previous reports.ConclusionsThese findings demonstrate that Tg338 mice propagate prions of caprine origin and provide a suitable baseline for examination of samples identified in the expanded US caprine scrapie surveillance program.

A transfectant RK13 cell line permissive to classical caprine scrapie prion propagation

“…Although the incubation periods in P1 Tg338 mice were prolong and variable for 3 caprine scrapie inocula, incubation periods in P2 mice were short and very similar. 21 Furthermore, brain lesion profiles 21 and PrP Sc accumulation levels in P2 mice were very similar ( Fig. 2A).…”

“…13,24 The ability of RK13 cells to propagate prions upon expression of exogenous PrP C from multiple species 12,13,16,17 clearly confirmed that RK13 cells have the required cellular machinery for efficient prion propagation. Although PRNP haplotype 3 and 4 caprine scrapie inocula were able to produce clinical scrapie in recipient goats 9 and Tg338 mice 21 which was very similar to PRNP haplotype 1 and 2 caprine scrapie inoculated animals, the lack of scrapie prion propagation in cpRK13cells when inoculated with the same PRNP haplotypes 3 and 4 scrapie inocula highlight the possible involvement of other unidentified factors to establish successful infection.…”

“…21 It was an interesting observation that passage 1 (P1) Tg338 mice receiving haplotype 2,3 inoculum succumb to clinical scrapie earlier than Tg338 mice receiving haplotype 1,2 (animal ID: g3538) scrapie inoculum. 21 The same haplotype 3 9 and 4 (unpublished observation) inocula and a haplotype 1 caprine scrapie inoculum produced clinical scrapie in recipient goats with very similar incubation periods. 9 Other research groups have also revealed the lack of propagation of a range of ovine scrapie isolates in ovine RK13 cells (Rov9).…”

“…25 Similarly, Rov9 cells were shown to be highly permissive to mouse-passaged classical ovine scrapie prion isolates. 11,12 A previous study by our group 21 used bioassay in Tg338 mice to characterize classical scrapie from a goat with PRNP haplotype 1,2 (animal ID: g3538), haplotype 2,3 (animal IDs: g30-75) or haplotype 1,4 (animal ID: g3558). Although the incubation periods in P1 Tg338 mice were prolong and variable for 3 caprine scrapie inocula, incubation periods in P2 mice were short and very similar.…”

“…11 Prior to the preparation of brain homogenates, PrP Sc in clinically scrapie affected goats and Tg338 mice used in this study was confirmed by IHC, a commercially available TSE ELISA kit (IDEXX), and western blot assays and scrapie infectivity was confirmed in bioassay studies using goats and Tg338 mice. 9,21,22 For the present study, brain homogenates prepared from all 5 scrapieinfected goats and 3 Tg338 mice were again assessed for PrP Sc by TSE ELISA and protein gel blot. As expected, significant amounts of PrP Sc in both the caprine and the murine scrapie and pcRK13 cells.…”