1. ¹ Australian Red Cross Blood Service-Endeavour, Sydney, Australia
2. ² Research Unit of Transfusion Medicine and Immunogenetics, Faculty of Medicine, University of Sydney, Sydney, New South Wales, Australia
3. ³ Department of Pathology, University of Melbourne, Melbourne, Australia
4. ⁴ CSIRO Livestock Industries, Australian Animal Health laboratory, Geelong, Victoria, Australia
5. ⁵ Freie Universitaet Berlin, Institut fuer Chemie/Biochemie, Berlin, Germany

Correspondence: Dr Fang F Yuan, ARCBS-Endeavour, 153 Clarence Street, Sydney, NSW 2000, Australia. Email: fyuan@arcbs.redcross.org.au

Received 6 April 2005; Accepted 16 June 2005; Published online 21 October 2005.

Abstract

Amino acid residues 90–120 of the prion protein (PrP) are likely to be critical for the conversion of PrP^c to PrP^sc in the transmissible spongiform encephalopathies. We raised 10 monoclonal antibodies against the 90–120 amino acid region, mapped the epitope specificity of these anti-PrP antibodies, and investigated the expression of epitopes recognized by the antibodies in both PrP^c and PrP^sc. Four out of five of the anti-PrP antibodies raised in a prion knockout mouse immunized with the linear peptide of PrP90–120 could detect PrP^sc in 'native' and denatured forms and PrP^c in normal cells, as well as recognize epitopes within PrP93–112 residues. In contrast, the other six anti-PrP reagents, including five raised from the two knockout mice immunized with conformationally modified PrP90–120 peptide, could detect PrP^c and recognize epitopes within PrP93–107 residues. Four of these reagents could also detect denatured PrP^sc on western blots but not PrP^sc plaques in brain tissue. The results indicate that residues PrP93–102 are exposed in PrP^c but are buried upon conversion to the PrP^sc isoform. Furthermore, PrP103–107 residues are partially buried in PrP^sc while only the PrP107–112 epitope remains exposed, suggesting that the region PrP93–112 undergoes conformational changes during its conversion to PrP^sc.