Conformational variation between allelic variants of cell-surface ovine prion protein Available to Purchase

The distribution of prion infectivity and PrP^Sc between peripheral lymphoid tissues suggests their possible haematogenic spread during the progression of natural scrapie in susceptible sheep. Since ovine PBMCs (peripheral blood mononuclear cells) express PrP^C, they have the potential to carry or harbour disease-associated forms of PrP. To detect the possible presence of disease-associated PrP on the surface of blood cells, an understanding is required of the conformations that normal ovine cell-surface PrP^C may adopt. In the present study, we have used monoclonal antibodies that recognize epitopes in either the N- or C-terminal portions of PrP to probe the conformations of PrP^C on ovine PBMCs by flow cytometry. Although PBMCs from scrapie-susceptible and -resistant genotypes of sheep expressed similar levels of cell-surface PrP^C, as judged by their reactivity with N-terminal-specific anti-PrP monoclonal antibodies, there was considerable genotypic heterogeneity in the region between helix-1 and residue 171. Cells from PrP-VRQ (V¹³⁶R¹⁵⁴Q¹⁷¹) sheep showed uniform reactivity with monoclonal antibodies that bound to epitopes around helix-1, whereas cells from PrP-ARQ (A¹³⁶R¹⁵⁴Q¹⁷¹) and PrP-ARR (A¹³⁶R¹⁵⁴R¹⁷¹) sheep showed variable binding. The region between β-strand-2 and residue 171, which includes a YYR motif, was buried or obscured in cell-surface PrP^C on PBMCs from scrapie-susceptible and -resistant sheep. However, an epitope of PrP^C that is influenced by residue 171 was more exposed on PBMCs from PrP-VRQ sheep than on PBMCs from the PrP-ARQ genotype. Our results highlight conformational variation between scrapie-susceptible and -resistant forms of cell-surface PrP^C and also between allelic variants of susceptible genotypes.