Mad cow disease has killed more than 200,000 cattle and doomed millions more to preventative slaughter. Its human equivalent, Creutzfeldt-Jakob disease, has claimed more than 100 lives. No effective treatment currently exists for these diseases, which are caused by misfolded prion proteins that wreak havoc in the brain and lead to neurodegeneration. But findings published online this week by the Proceedings of the National Academy of Sciences suggest that the common antibiotic tetracycline renders prions susceptible to digestion by enzymes and helps staves off disease in hamsters.

Previous research had shown that tetracycline drugs alter the properties and neurotoxicity of prion proteins in vitro. Fabrizio Tagliavini of the Carlo Besta National Neurological Institute in Milan, Italy, and his colleagues thus set out to test the antibiotic's prion-stopping power in animals infected with so-called transmissible spongiform encephalopathies. A crucial step in the transmission of these diseases is the formation of protease-resistant forms of the prion protein (PrP), which cannot be broken down by the body and subsequently accumulate in the brain. The researchers extracted PrP from patients with new variant Creutzfeldt-Jakob disease (vCJD) and cattle suffering from BSE and incubated them in tetracycline solutions of varying concentrations. As the dose of the antibiotic increased, the team reports, the proteins became less resistant to degradation by enzymes. Most importantly, hamsters infected with tetracycline-treated prions experienced a slower onset of symptoms and survived longer than did the recipients of untreated prions.

The findings could point the way toward stopping the transmission of these dreaded diseases. Because the drug seems to weaken the prions' protective armor, the authors conclude that "tetracyclines are immediate candidates for prion inactivation in potentially contaminated products and prevention strategies relevant to acquired forms of disease."