Scrapie infectivity, fibrils and low molecular weight protein

The development of a short incubation model of scrapie (strain 263K), in golden hamsters 1,2 , has added impetus to the purification of the infectious agent. Our own attempts 3 have been based on methods pioneered by Millson 4,5 and developed by Prusiner 6,7 . We present here results indicating that a purification factor of up to 10 4 with respect to protein may now be possible. Fractions from brain with high infectivity had a sedimentation range of 70–300S and contained an abundance of fibrils closely similar to the scrapie-associated fibrils (SAF) discovered by Merz et al. 8,9 . Material of molecular weight ( M r ) 26,000, which is probably protein, appears to be a major constituent of the fibrils. The association between infectivity and fibrils raises two possibilities: the fibrils are an infectious form of the scrapie agent or they are a pathological response to scrapie infection.