Fig 1.
TgRab survival times after inoculation.
Each dot corresponds to a mouse. Dots with a red margin represent TSE positive animals. Green dots are negative controls; grey dots correspond to cattle strains; blue dots to sheep strains; yellow dots to rabbit originating strains; pink dots are murine strains and purple dots to CWD strain.
Table 1.
Comparison of TgRab mice and actual rabbit bioassays.
Table 2.
Attack rates and survival times (±SEM) of the inoculated TgRab mice.
Fig 2.
Biochemical analysis of brain homogenates from TgRab mice inoculated with different prion strains.
Two representative brain homogenates (per group) from TgRab mice inoculated with different prion strains [cattle: BSE-L and BSE-C; mouse: RML and ME7; sheep: SSPB/1, sheep BSE-C and atypical scrapie; deer: CWD; rabbit: de novo–RaPrPres (in vitro sample) and de novo–NZW (in vivo sample)] were digested with 100 μg/ml of proteinase K (PK) and analyzed by western blot using two different monoclonal antibodies (upper blot- 6H4 and lower blot– 12B2). Differential electrophoretic migrations and glycosylation patterns observed are consistent with the origin of the prion strains used for inoculation. Control NZW: Normal rabbit brain homogenate. MW: Molecular weight. Vertical lines separate blots with different exposition times.
Fig 3.
Brain lesion and PrPd deposit distribution of the first passage of several prion strains in TgRab mice.
Brain lesion profiles and PrPd deposition profiles represent the mean semi-quantitative scoring (0–4, vertical axis) of the spongiform lesions (black) and the immunohistochemical labelling of PrPd deposits (red) against 14 brain regions (Pfc: piriform cortex, H: hippocampus, Oc: occipital cortex, Tc: temporal cortex, Pc: parietal cortex, Fc: frontal cortex, S: striatum, T: thalamus, HT: hypothalamus, M: mesencephalon, Mob: medulla oblongata, Cm: cerebellar nuclei, Cv: cerebellar vermis, Cc: cerebellar cortex). Note that classical BSE-originating strains (BSE-C and Sheep BSE) generate very similar shaped brain profiles with low scores in the hypothalamus and strong involvement of the brain stem, clearly distinguishable from BSE-L (which maintains its affinity towards cortices as seen in cattle field cases). Scrapie derived strain show a brain profile with cortical and hypothalamic tropisms. The de novo NZW strain shows a distinct tropism for the diencephalon (particularly hypothalamus) and brainstem while sparing the cortices.
Fig 4.
A: Histopathological characterization of several prion strains in TgRab mice.
Classical BSE-derived strains show a remarkably similar lesion and PrPd deposition patterns. PrPd plaques are readily conspicuous in haematoxylin and eosin (H&E) stained sections (arrowheads). Upon immunohistochemical (IHC) staining with 6H4 antibody against prion protein, the predominant staining pattern consists of intensely stained round-shaped plaques which can coalesce and form large aggregates. Scrapie derived strains, on the other hand, as well as BSE-L and de novo NZW show a rather discreet, plaqueless, punctiform immunolabelling pattern found in the neuropil within and around neuronal bodies. Linear and stellate shaped PrPd immunolabelling patterns are observed occasionally. In the case of RML, ME7 and BSE-L this pattern is also observed in the cortices while in de novo NZW the immunolabelling is restricted to the thalamus and brainstem. All images were taken at the same magnification. Bar 50 μm. B: Brain schematic mapping summary of the distribution of spongiform lesions and PrPd deposits in the brains of TgRab mice. The red dots depict the areas where spongiosis and/or PrPd deposits were mostly found in each group of infected mice. Note that the consistent picture yielded by BSE-C derived strains strongly involved the medulla oblongata, ventral mesencephalon, thalamus and deep parietal cortex while sparing the remaining cortices and the hypothalamus. This is clearly different from BSE-L which shows a remarkable tropism for the cerebral cortices and a lesser involvement of the brainstem structures. Scrapie derived strains, instead, show a clear tropism for the hypothalamus and a strong involvement of the cerebral cortices also. The spontaneous rabbit strain de novo NZW spares the cerebral cortices but shows a clear tropism for the hypothalamus.