Brain lesion and PrP^res deposit distribution of the wild-type mice-passaged recombinant PMSA products after secondary transmission in wild-type mice.

Histopathological assessment of spongiform lesions and PrP^res deposits of PMSA preparations stMI-03, btMI-05 and btMI-09 after secondary transmission into C57BL/6 mice(which was unsuccessful already at first passage for stMI-01) shows moderate to intense spongiform changes upon hematoxylin and eosin staining (H&E), as can be seen in the thalamic region of representative animals from each group. PrP^res deposits, labeled with 6C2 mAb (1:1,000), were detectable but very faint, all showing punctate or granular deposits associated with glia or neurons and in the neuropil (see digitally enlarged images on the left). Spongiform lesion profiles and PrP^res deposition profiles, shown on the right, represent the mean semi-quantitative scoring (0–4, vertical axis, ± standard error of the mean -error bars-) of the spongiform lesions (continuous line, black) and the immunohistochemical labelling of PrP^res deposits (dashed line, black) against 14 brain regions. Although there are some differences, mostly in terms of spongiform lesion intensity, stMI-03, btMI-05, and btMI-09-inoculated animals show highly coincident lesions and PrP^res staining, suggesting infection by the same strain or the convergence of the recombinant preparations <i>in vivo</i> to the same strain through selection or adaptation. H&E: Hematoxylin and eosin staining; IHC: Immunohistochemistry. (DOCX)