More than 200 cases of variant Creutz­feldt-Jakob disease, the human form of mad cow, have occurred worldwide since the 1990s. No accepted treatment exists for the devastatingly fatal disease or any of the others caused by infection with the malformed, malignant protein particles called prions. Giovanna R. ­Mallucci and her co-workers at the Institute of Neurology in London have performed an experiment in mice that could lay the groundwork for an eventual cure. Researchers genetically engineered mice to produce the protein PrP for only the first nine weeks after birth. PrP misfolds in the presence of prions, which causes it to produce more prions.

When both the altered mice and a normal group were injected with prions causing the illness called scrapie, both groups experienced a cognitive decline at first. The normal subjects continued to deteriorate. But by 12 weeks, the engineered group, without an ongoing supply of PrP, had recovered memory and normal be­hav­ior patterns. The absence of the natural protein did not appear to have an adverse effect on the restored rodents. If this approach proves itself further, it might lead to drugs or gene therapies that diminish PrP.

Until that happens, the possibility of prions infecting people through the blood supply remains an ever present fear. Robert Rohwer of the Veterans Affairs Med­ical Center in Baltimore and his colleagues invented a filter that might be able to purge red blood cells of prions. The team members began by searching through a library of millions of chemicals until they discovered a compound, L13, that readily sticks to prions. Scrapie-containing blood filtered through beads coated with L13 and then injected into hamsters did not cause disease in the animals, unlike tainted, unfiltered blood.
 —Gary Stix