beta -PrP form of human prion protein stimulates production of monoclonal antibodies to epitope 91-110 that recognise native PrP super(Sc)

Prion diseases are associated with accumulation of strain-dependent biochemically distinct, disease-related isoforms (PrP super(Sc)) of host-encoded prion protein (PrP super(C)). PrP super(Sc) is characterised by increased beta -sheet content, detergent insolubility and protease resistance. Recombinant alpha -PrP adopts a PrP super(C)-like conformation, while beta -PrP conformationally resembles PrP super(Sc), to these we raised 81 monoclonal antibodies in Prnp super(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, [not, vert, similar] 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 PrP super(C) was recognised by both antibody groups, but only anti- beta -PrP antibodies directed to 91-110 residues recognised native PrP super(Sc) 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 PrP super(Sc), four failed to recognise PK-treated native bovine PrP super(Sc), one of which also did not recognise native PK-treated ovine PrP super(Sc), 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 PrP super(Sc).