The POM Monoclonals: A Comprehensive Set of Antibodies to Non-Overlapping Prion Protein Epitopes

PrP(Sc), a misfolded and aggregated form of the cellular prion protein PrP(C), is the only defined constituent of the transmissible agent causing prion diseases. Expression of PrP(C) in the host organism is necessary for prion replication and for prion neurotoxicity. Understanding prion diseases necessitates detailed structural insights into PrP(C) and PrP(Sc). Towards this goal, we have developed a comprehensive collection of monoclonal antibodies denoted POM1 to POM19 and directed against many different epitopes of mouse PrP(C). Three epitopes are located within the N-terminal octarepeat region, one is situated within the central unstructured region, and four epitopes are discontinuous within the globular C-proximal domain of PrP(C). Some of these antibodies recognize epitopes that are resilient to protease digestion in PrP(Sc). Other antibodies immunoprecipitate PrP(C), but not PrP(Sc). A third group was found to immunoprecipitate both PrP isoforms. Some of the latter antibodies could be blocked with epitope-mimicking peptides, and incubation with an excess of these peptides allowed for immunochromatography of PrP(C) and PrP(Sc). Amino-proximal antibodies were found to react with repetitive PrP(C) epitopes, thereby vastly increasing their avidity. We have also created functional single-chain miniantibodies from selected POMs, which retained the binding characteristics despite their low molecular mass. The POM collection, thus, represents a unique set of reagents allowing for studies with a variety of techniques, including western blotting, ELISA, immunoprecipitation, conformation-dependent immunoassays, and plasmon surface plasmon resonance-based assays.