Small amounts of brain tissue (2 g) infected with Creutzfeldt-Jakob disease (CJD) can be fractionated by using a simple 1-day method that includes lysis with Nlauroylsarcosine. Unique fibrils have been identified previously in scrapie-and CJD-infected tissue. These fibrils were abundant in final fractions. Preparations from human CJD autopsy material and from experimental hamster and guinea pig CJD all displayed readily identifiable fibrils that were not seen in control preparations. Thus, these methods appear to be of value in biopsy diagnosis of suspected human cases of CJD. Lysis with N-lauroylsarcosine quantitatively solubilized infectivity from membrane-rich fractions. Significant infectivity was recovered in microfractionations. After proteinase K digestion, a diffuse band at 29 kDa was detectable on NaDodSO4/PAGE. This 29-kDa material was not present in uninfected control brain and was similar to that seen in scrapie. Protein blots of human, guinea pig, and hamster CJD fractions were tested with an antibody raised against a 29-kDa band from mouse scrapie; 29-kDa proteins were labeled in all CJD and scrapie fractions but not in controls. These results indicate that specific proteins in both these diseases share common antigenic determinants. Ricin and wheat germ agglutinin, but not concanavalin A, also labeled a portion of the 29-kDa band from hamster CJD and hamster scrapie fractions, but they did not label any. bands in normal hamster fractions at the same gel protein loads. When proteinase K treatment was omitted, specific bands of =35 kDa were detected in CJD samples. These results are consistent with the idea that some CJD-and scrapie-specific proteins are glycoproteins or sialoglycoproteins that can reside in or possibly derive from cell membranes.

It has been suggested that the infectious agents of scrapie and Creutzfeldt-Jakob disease (CJD) are 'prions' constituted by a protease resistant glycopeptide, PrP. To analyze the role of PrP in CJD infectivity we re-evaluated the biochemical characteristics of infectivity. First, when the infectious agent is not aggregated, infectivity is exquisitely sensitive to proteinase K treatment, and therefore a proteinase-K-resistant molecule (e.g. PrP) is unlikely to contain information essential for agent replication. Second, removal of sugar residues from Gp34 (the major precursor of the proteolyzed PrP band) failed to reduce infectivity. Third, one-half of the PrP peptides could be separated from significant infectivity using nondenaturing conditions with practical quantitative recovery of infectivity. These studies suggest that PrP in itself is unlikely to be the replicating component of the infectious agent. We suggest that these as yet undefined agents may consist of core protein and nucleic acid that are incompletely assembled in, and protected by, cell membranes. This hypothesis would (i) explain the absence of conventional viral particles in these diseases, (ii) account for observed membrane pathology including altered behavior of endogenous membrane proteins, and (iii) would be consistent with the replication and transforming properties of CJD that indicate there is an agent specific nucleic acid.

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.

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Inoculation of the buffy coat of blood from guinea pigs infected with Creutzfeldt-Jakob disease resulted in passage of this disease to recipient animals. This demonstrates that there is a viremia in experimental Creutzfeldt-Jakob disease. These findings suggest that the hematogenous route may be implicated in the human infection and that the disease may possibly be transmitted by blood transfusions.