IT MIGHT one day be possible to slow the progress of prion diseases-by adding yet more prions. Researchers at the University of California, Davis, say their computer model supports the controversial theory that you could treat such diseases with a dose of normal prions from another species.
"It is an elegant mathematical model, one that suggests a route to therapy, and one that is supported by considerable biological evidence," says Mike Scott, a prion researcher at the University of California, San Francisco. "But there are some major hurdles that must be overcome before we know whether this approach will prove to be of use."
Prion diseases are triggered by an abnormal form of the protein PrP, which is found on the surface of brain cells. If a little abnormal PrP gets into the brain, it makes more of itself by converting normal PrP into the abnormal form, which clumps together to form damaging "plaques".
Biophysicist Daniel Cox and his colleagues have now come up with a simplified model of how these plaques grow that predicts how long it takes the disease to develop. They say the model's predictions closely match what is seen in lab experiments.
Such experiments have also revealed a species barrier to prion transmission. For example, abnormal mouse PrP is good at infecting hamsters, but hamster PrP isn't so good at infecting mice. So the team looked to see if adding normal hamster PrP to the brain of a mouse already infected by abnormal mouse PrP would affect incubation time.
According to the model, this would indeed slow the progress of the disease. When the normal hamster PrP comes into contact with developing mouse PrP plaques, it forms a coat of abnormal hamster PrP around them, the researchers say.
However, this is only true if the hamster PrP is converted into the abnormal form faster than mouse PrP. What's more, you'd have to inject large concentrations of normal hamster PrP. And that's a major obstacle, says Sc
Contact: Claire Bowles