β-PrP form of human prion protein stimulates production of monoclonal antibodies to epitope 91–110 that recognise native PrPSc

Prion diseases are associated with accumulation of strain-dependent biochemically distinct, disease-related isoforms (PrPsc) of host-encoded prion protein (PrPC). PrPsc is characterised by increased 1 -sheet content, detergent insolubility and protease resistance. Recombinant alpha-PrP adopts a PrPC-like conformation, while beta-PrP conformationally resembles PrPsc, to these we raised 81 monoclonal antibodies in Prnp(0/0) mice. The N-terminal residues 91-110 are highly immunogenic in beta-PrP-immunised mice and of (17/41) anti-beta-PrP antibodies that could be epitope-mapped, similar to 70%, recognised this segment. In contrast, only 3/40 anti-alpha-PrP antibodies could be mapped and none interacted with this region, instead recognising residues 131-150, 141-160 and 171-190. Native PrPC was recognised by both antibody groups, but only ami-beta-PrP antibodies directed to 91 -110 residues recognised native PrPsc with high affinity, where in addition, species heterogeneity was also evident. Within the six anti-beta-PrP antibodies studied, they all recognised PK-treated native human and mouse PrPsc, four failed to recognise PK-treated native bovine PrPsc, one of which also did not recognise native PK-treated ovine PrPsc, showing the epitope becomes exposed on unfolding and disaggregation. These results demonstrate strain-dependent variations in chain conformation and packing within the 91-110 region of PrPsc. (c) 2007 Published by Elsevier B.V.