Faculty Bibliography

Prion diseases are transmissible and invariably fatal neurodegenerative disorders associated with a conformational transformation of the cellular prion protein (PrP(C)) into a self-replicating and proteinase K (PK)-resistant conformer, scrapie PrP (PrP(Sc)). Humoral immunity may significantly prolong the incubation period and even prevent disease in murine models of prionoses. However, the mechanism(s) of action of anti-PrP monoclonal antibodies (Mabs) remain(s) obscure. The murine neuroblastoma N2a cell line, infected with the 22L mouse-adapted scrapie strain, was used to screen a large library of Mabs with similar binding affinities to PrP, to identify those antibodies which could clear established infection and/or prevent infection de novo. Three Mabs were found capable of complete and persistent clearing of already-infected N2a cells of PrP(Sc). These antibodies were 6D11 (generated to PK-resistant PrP(Sc) and detecting PrP residues 93-109), and 7H6 and 7A12, which were raised against recombinant PrP and react with neighbouring epitopes of PrP residues 130-140 and 143-155, respectively. Mabs were found to interact with PrP(Sc) formation both on the cell surface and after internalization in the cytosol. Treatment with Mabs was not associated with toxicity nor did it result in decreased expression of PrP(C). Both preincubation of N2a cells with Mabs prior to exposure to 22L inoculum and preincubation of the inoculum with Mabs prior to infecting N2a cells resulted in a significant reduction in PrP(Sc) levels. Information provided in these studies is important for the rational design of humoral immune therapy for prion infection in animals and eventually in humans

The conversion of the normal cellular prion protein, PrP(C), into the protease-resistant, scrapie PrP(Sc) aggregate is the cause of prion diseases. We developed a novel enzyme-linked immunosorbent assay (ELISA) that is specific for PrP aggregate by screening 30 anti-PrP monoclonal antibodies (MAbs) for their ability to react with recombinant mouse, ovine, bovine, or human PrP dimers. One MAb that reacts with all four recombinant PrP dimers also reacts with PrP(Sc) aggregates in ME7-, 139A-, or 22L-infected mouse brains. The PrP(Sc) aggregate is proteinase K resistant, has a mass of 2,000 kDa or more, and is present at a time when no protease-resistant PrP is detectable. This simple and sensitive assay provides the basis for the development of a diagnostic test for prion diseases in other species. Finally, the principle of the aggregate-specific ELISA we have developed may be applicable to other diseases caused by abnormal protein aggregation, such as Alzheimer's disease or Parkinson's disease

Prion diseases are of considerable importance because of the threat of a variant form of Creutzfeldt Jakob disease that has emerged in recent years. Pre-clinical diagnosis of prion diseases still remains poor and effective therapies also do not exist at present. This review examines research on possible therapeutic strategies that might have potential benefits if applied before neurodegeneration has occurred.