Scrapie infectivity, fibrils and low molecular weight protein

Abstract

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 attempts³ 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 10⁴ 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.