Scrapie-associated fibrils in Creutzfeldt-Jakob disease.

Scrapie of sheep, and Creutzfeldt-Jakob disease (CJD) of man belong to a group of transmissible encephalopathies which have been successfully transmitted to a variety of hosts. In susceptible hosts, these diseases are characterized by progressive degeneration of the central nervous system leading inevitably to death. The agents responsible for these diseases have not yet been identified, but they exhibit similar physicochemical characteristics. Abnormal fibrils designated 'scrapie associated fibrils' (SAF) have been observed in synaptosomal preparations of scrapie infected brain. They have never been observed in various types of control animals. We report here that SAF are present in CJD brain fractions in the experimentally transmitted disease as well as in a few naturally occurring human cases of CJD. SAF are also present in spleen extracts of animals experimentally infected with scrapie or CJD. This close association of SAF with these two diseases and two different tissues (brain and spleen) known to contain titres of infectivity, suggest that the SAF are: (1) a unique pathological response to the disease or (2) the infectious agent of these diseases.