Involvement of protein in scrapie agent infectivity

The nature of the causative agent of scrapie is not known. Previous work has demonstrated that nuclease digestion does not inactivate scrapie infectivity, but there are conflicting reports about the effects of proteases. It is shown here that the broad range protease, proteinase K, reduces scrapie infectivity under all conditions tested. Control experiments demonstrated that the loss of infectivity is not artefactual and results from protein breakdown. Proteolytic digestion in the presence of detergent greatly increases proteolysis, but does not lead to a further loss of infectivity. This suggests that the protein involved may be a surface component, but whether the component is an integral or secondary part of the agent is not known.