Abstract: The present invention provides antibodies that specifically bind with a high degree of binding affinity to a native ungulate PrPC and/or a denatured ungulate PrPSc, but not to a native ungulate PrPSc. Preferred antibodies find native bovine PrPC and treated PrPSc but not native bovine PrPSc and can be used in an assay to determine if a sample is infected with infectious prions, i.e. PrPSc.

Abstract: Antibodies are disclosed which specifically bind to native PrPSc in situ. Preferred antibodies bind only to the native PrPSc of a particular species e.g., human, cow, sheep, pig, etc. Particularly preferred antibodies bind specifically to a particular isoform of human PrPSc. Preferred antibodies of the invention are (1) produced by phage display methodology, (2) bind specifically to native PrPSc, (3) neutralizes the infectivity of prions, (4) bind to PrPSc in situ and (5) bind 50% or more of PrPSc in a liquid flowable sample. Antibodies of the invention can be bound to a substrate and used to assay a sample (which has any PrPSc denatured via proteinase K) for the presence of PrPSc of a specific species which PrPSc is associated with disease. Antibodies which specifically bind to human PrPSc can be labeled and injected carrying out an in vivo diagnostic test to determine if the human is infected with prions associated with disease.

Abstract: Methods are disclosed whereby formulations of molecules are administered rendering cells resistant to infection with infectious proteins such as prions. The formulation preferably comprises a plurality of Fab fragments which (1) recognize and selectively bind to a range of epitopes on the protein of interest, (e.g. epitopes on PrPC) and (2) bind to epitopes which interrupt the chain of events resulting in a change of the protein's conformation to an infectious disease conformation of the protein. The molecules and formulation are also useful in clearing infectious proteins from cells.