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

ABSTRACT

To assess scrapie infectivity associated with caprine-origin tissues, bioassay can be performed using kids, lambs or transgenic mice expressing caprine or ovine prion (PRNP) alleles, but the incubation periods are fairly long. Although several classical ovine scrapie prion permissive cell lines with the ability to detect brain-derived scrapie prion have been available, no classical caprine scrapie permissive cell line is currently available. Therefore, the aims of this study were to generate a rabbit kidney epithelial cell line (RK13) stably expressing caprine wild-type PRNP (cpRK13) and then to assess permissiveness of cpRK13 cells to classical caprine scrapie prion propagation. The cpRK13 and plasmid control RK13 (pcRK13) cells were incubated with brain-derived classical caprine scrapie inocula prepared from goats or ovinized transgenic mice (Tg338, express ovine VRQ allele) infected with caprine scrapie. Significant PrP^Sc accumulation, which is indicative of scrapie prion propagation, was detected by TSE ELISA and immunohistochemistry in cpRK13 cells inoculated with classical caprine scrapie inocula. Western blot analysis revealed the typical proteinase K-resistant 3 PrP^res isoforms in the caprine scrapie prion inoculated cpRK13 cell lysate. Importantly, PrP^Sc accumulation was not detected in similarly inoculated pcRK13 cells, whether by TSE ELISA, immunohistochemistry, or western blot. These findings suggest that caprine scrapie prions can be propagated in cpRK13 cells, thus this cell line may be a useful tool for the assessment of classical caprine prions in the brain tissues of goats.

KEYWORDS:

• Caprine
• Cell culture
• Classical scrapie
• Prions
• Propagation
• RK13 cells

DISCLOSURE OF POTENTIAL CONFLICTS OF INTEREST

Authors declare that no potential conflicts of interest exist.

ACKNOWLEDGMENTS

We thank Donald P. Knowles for critical reading of the manuscript. The authors would also like to thank Linda Hamburg, Lori Fuller, Laetisha O'Rourke, Deborah Wolheter, Jan Luft and Emma Karel for technical assistance. Mention of trade names or commercial products in this article is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture.

Funding

This work was supported by funds from the USDA Agricultural Research Service (CRIS 2090-32000-030-00D).