Detection of cattle-derived BSE prions using transgenic mice overexpressing bovine PrP(C)

In interspecies transmissions of transmissible spongiform encephalopathies, the agent has to overcome a species barrier that is largely influenced by the rate of homology between the prion proteins (PrP(C)) of the two involved species. Generating transgenic mice expressing PrP(C) of a foreign species is an approach to develop TSE models that are at least partly devoid of a species barrier. The availability of such animals would enable the detection of low doses of infectivity in tissues or bodily fluids derived from other species. We generated transgenic mice that overexpress bovine PrP(C) (Tgbov XV mice) for the development of an improved detection assay for cattle derived BSE prions. These mice succumbed to the disease 250 days after inoculation with a brain homogenate from BSE diseased cattle. Diagnosis of BSE in transgenic mice was confirmed using Western blot, as well as histological and immunohistochemical methods. In contrast, transgenic mice overexpressing murine PrP(C) (tga20 mice) did not display shorter incubation times than nontransgenic RIII mice infected with the same inoculum. The expression of a chimaeric PrP of murine and bovine sequences rendered such mice partly, if not entirely resistant to an infection with the BSE agent.