Antigenic features of prion proteins of sheep and of other mammalian species

Pathological prion protein (PrPSc) which is a conformational isoform of a host-encoded protein designated (PrPC) serves as a specific marker protein for the immunochemical diagnosis of transmissible spongiform encephalopathies (TSE). The generation of suitable antibodies to PrPSc therefore underlies the specificity and sensitivity of diagnostic assays. However, a most antibodies reported to date are directed to a limited number of epitopes only. PrPC is a highly conserved cell membrane protein in all mammalian species studied to date. In an attempt to generate antibodies to further regions of PrP we raised antisera in rabbits and chicken against sixteen synthetic peptides which represent the complete aminoacid sequence of ovine PrP. By this approach immunotolerance was overcome and immunoblot-reactive antibodies were stimulated to epitopes at almost any site of ovine PrPC and PrPSc. A large number of different antibodies cross-reacted also with affinity-purified PrP(C)s from other mammalian species including cow, goat, pig, man, dog, cat, mink, mouse, hamster and guinea pig. No epitope, however, was recognized exclusively on the pathological or cellular isoform of PrP indicating that both isoforms occur in highly denatured conformations on the immunoblots. Antibodies to the amino-terminus are suitable for immunprecipitation of PrP. The availability of rabbit and chicken anti-peptide antibodies to PrP will greatly improve immunochemical diagnosis and pathogenetic studies on these diseases. (C) 1997 Elsevier Science B.V.