An isolated protein is provided for use in treatment of a condition selected from the group consisting of Alzheimer's disease, familial Danish dementia and familial British dementia in a mammal, including man. The isolated protein is selected from the group consisting of proteins comprising an amino acid sequence having at least 70% identity to residues 90-236 of Bri2 from human； and proteins comprising an amino acid sequence having at least 70% identity to any one of the Brichos domains of Bri2 from human, chimpanzee, bovine, pig,mouse and rat.
