The senile dementias: a new model.

Kuru and Creutzfeldt Jakob disease are fatal neurological disorders in humans that are transmissible to humans and other experimental animals. Largely because of their transmissibility the etiology of these diseases has been ascribed to infectious agents classified as "slow" or unconventional viruses. A related neurological disease in sheep called scrapie has also been ascribed to infection by slow viruses. Despite more than 20 years of intensive research no viruses or other infectious agents have ever been isolated or identified as the causative factors in these transmissible neurological diseases. The model presented below suggests that these "subacute spongiform virus encephalopathies" are not due to any infectious agent. Rather, I propose that they are caused by peptide hormones that may be transmitted from one individual to another in blood or other tissue. These hormones are postulated to activate genes in neurons whose proteins result in the observed pathology. It also is suggested that other non-transmissible human neurological diseases such as Alzheimer's disease may be due to endogenously produced peptide hormones that progressively activate genes responsible for the synthesis of amyloid proteins that are associated with neurological diseases.