Anti-PrP antibodies detected at terminal stage of prion-affected mouse

The causative agent of prion diseases is the pathological isoform (PrPSc) of the host-encoded cellular prion protein (PrPC). PrPSc has an identical amino acid sequence to PrPC; thus, it has been assumed that an immune response against PrPSc could not be found in prion-affected animals. In this study, we found the anti-prion protein (PrP) antibody at the terminal stage of mouse scrapie. Several sera from mice in the terminal stage of scrapie reacted to the recombinant mouse PrP (rMPrP) molecules and brain homogenates of mouse prion diseases. These results indicate that mouse could recognize PrPC or PrPSc as antigens by the host immune system. Furthermore, immunization with rMPrP generates high titers of anti-PrP antibodies in wild-type mice. Some anti-PrP antibodies immunized with rMPrP prevent PrPSc replication in vitro. The mouse sera from terminal prion disease have several wide epitopes, although mouse sera immunized with rMPrP possess narrow epitopes.