THE INFECTIVITY OF SPONGIFORM ENCEPHALOPATHIES - DOES A MODIFIED MEMBRANE HYPOTHESIS ACCOUNT FOR LACK OF IMMUNE-RESPONSE

Scrapie, the prototype of a group of diseases which have the unique property of being both hereditary and infectious, is also exceptional in that it fails to evoke an immune response. Purification of crude scrapie preparations revealed a strong association of infectivity with a membrane protein ('PrP(sc)'); but a protein with the same amino acid sequence ('PrP(c)') was subsequently also found in normal mammalian nervous tissue. It is postulated by some investigators that 'PrP(sc)' is itself the infectious agent, or the most important part thereof, but in papers making that proposal immunological aspects have not been addressed. Experimental evidence supporting the hypothesis of a membrane fragment as agent has likewise lately not been taken into account. A modified form of the membrane hypothesis could account for immunological as well as genetic aspects of these diseases.