HIGHLY INFECTIOUS PURIFIED PREPARATIONS OF DISEASE-SPECIFIC AMYLOID OF TRANSMISSIBLE SPONGIFORM ENCEPHALOPATHIES ARE NOT DEVOID OF NUCLEIC-ACIDS OF VIRAL SIZE

An efficient purification protocol for infectivity causing a transmiss ible spongiform encephalopathy (TSE) is described. From fractions puri fied by this protocol about 3 x 10(8) LD50 but only 3 ng of nucleic ac ids per gram of brain material can be isolated from all TSE-affected b rains (hamster, human, sheep: cattle). By PAGE such fractions from bra ins of infected and control hamsters contained only one distinct nucle ic acid band of 1.5 kb together with some broader smear of nucleic aci d material. Although distilled water was used fbr such purifications, quite often a similar nucleic acid band was isolated from blanks conta ining no brain material. In all instances this material proved to be D NA. The result challenges the potentially important claim that purifie d infectious preparations of TSE-specific amyloid are ii-ee of nucleic acids of viral size. Nucleic acids isolated by other groups from dise ased brain were not detected in preparations isolated by the new proto col. The application of this purification protocol in future studies w ill be helpful to decide whether TSEs an caused by agents containing n ucleic acid or by protein only.