Scrapie - Associated Protein

The 263K strain of scrapie in hamsters (1,2) has become the most important system for experimental research aimed at discovering the slow unconventional agent which natural ly causes the chronic subacute spongiform encephalopathy 'scrapie' in sheep (3). Other unidenti f ied but similar agents cause similar diseases in man (#), mink (3), and captive mule deer (5). In 1981 P. Merz et al. for the f i rs t t ime reported the consistant correlat ion of scrapie and a new morphologic ent i ty, 'scrapie-associated f ibr i ls ' (SAF), in brain materials from mice and hamsters (6). SAF subsequently were found by two other groups, which intended to puri fy the scrapie agent (798). Although described as f lattened rods by Prusiner et al. (7)9 the morphologic appearance of these structures i den t i f i e s them as SAF. A unique protein discovered in scrapie hamster brain (9) and discussed to be the infect ive scrapie agent ( i 0 ) has been shown to copuri fy with in fec t iv i ty and SAF to a high degree and thus seems to be the major consti tuent of SAF ( l l ) rather than the i n fec t i ous un i t i tself (12). This f inding and even more the elaborate and consequent electron microscopic studies by P. Merz et ah (16) s t rong ly suggest tha t SAF and scrapie agent may be synonymous. SAF and SAF-pro te in are the f i rst detectable morphologic and biochemical tissue changes caused by unconventional slow virus. Thus we have developed a rapid and ef f ic ient method to enrich SAF-protein.