Mad cow disease and other brain disorders stemming from prion proteins have long resisted cure. Now, in a test in mice, a prion disease caught early has been reversed.
Prions—misfolded versions of a natural protein called PrP—trigger normal PrP to misfold in the same way. Over time, prion infection kills so many neurons that the brain becomes riddled with holes.
In the new study, neurologist Giovanna R. Mallucci of the Institute of Neurology in London and her colleagues tested whether shutting off the prions' supply of PrP could alter the course of disease. They worked with genetically engineered mice that make PrP only for the first 9 weeks of life and normal mice that make PrP indefinitely.
The researchers infected both groups, shortly after birth, with prions that cause scrapie in sheep.
At 8 weeks of age, mice in both groups showed cognitive deficits. For example, mice normally spend more time exploring unfamiliar sets of objects than known o