NIH scientists investigating how prion diseases destroy the brain have observed a new form of the disease in mice that does not cause the hole-filled, sponge-like brain deterioration typically seen in prion diseases. Instead, the disease resembles a form of human Alzheimer's disease, cerebral amyloid angiopathy, that damages brain arteries. The study results, reported by NIH scientists at the National Institute of Allergy and Infectious Diseases (NIAID), are similar to findings from two newly reported human cases of the prion disease Gerstmann-Straussler-Scheinker syndrome (GSS). The mouse findings represent a new mechanism of prion disease brain damage, according to study lead author Dr. Bruce Chesebro, chief of the Laboratory of Persistent Viral Diseases at the NIAID’s Rocky Mountain Laboratories in Montana. The role of a specific cell anchor for prion protein is at the crux of the NIAID study. Normal prion protein uses a specific molecule, glycophosphoinositol (GPI), to fasten to host cells in the brain and other organs. In their study, the NIAID scientists genetically removed the GPI anchor from study mice, preventing the prion protein from fastening to cells and thereby enabling it to diffuse freely in the fluid outside the cells. The scientists then exposed those mice to infectious scrapie and observed the mice for up to 500 days to see if they became sick. The researchers documented signs typical of prion disease including weight loss, lack of grooming, gait abnormalities, and inactivity. But when they examined the brain tissue, they did not observe the sponge-like holes in and around nerve cells typical of prion disease.
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