Isolation of 14-nm virus-like particles from mouse brain infected with scrapie agent

SCRAPIE, a naturally occurring slow virus disease of sheep and goats, has been transmitted experimentally to the mouse, rat, gerbil, mink, hamster, vole and monkey 1 . The agent has shown an unusual resistance to ultraviolet irradiation 2 , nucleases 3 and β-propiolactone 4 . The precise nature of the scrapie agent, however, has yet to be defined. It is not known whether it is a virus, some type of self-replicating cell membrane, or part of a membrane 5 . The viroid hypothesis of the scrapie agent of Diener 6 has been discounted 7,8 . Several different particles have been seen in thin sections of naturally and experimentally infected scrapie tissues 9–11 . As repeated fluorocarbon extractions of mink tissues infected with Aleutian disease virus (ADV), which causes persistent infection of mink, have resulted in isolation of the virus 12,13 , we thought it worthwhile to apply the same physico-chemical techniques in an attempt to isolate virus from mouse brains infected with scrapie agent.