Prion diseases: a typical Kuhnian abnormality in a molecular paradigm

As a new class of pathogens with unusual properties, prions have been impli ed in several spongiform encephalopathies mainly affecting farm animals (sc rapie, mad-cow disease) and humans (kuru, Creutzfeldt-Jacob disease, fatal familial insomnia) (1). The term prions underlines the feature that the age nts would merely consist of a protein (2), perhaps a pathological counterpa rt of a cellular constituent with poorly defined functions (3-5). In review ing relevant literature, in order to test the validity of the 'protein-only hypothesis' for coherence and consistency with a molecular paradigm, we ha ve met evident discrepancies, making prion diseases a typical abnormality i n a Kuhnian sense. This paper summarizes and analyses the main features of the protein-only model. (C) 2000 Harcourt Publishers Ltd.