Scientists say they have proof that it will one day be possible to prevent diseases such as vCJD and BSE.
Prions destroy brain tissue
It is thought that these diseases, and others that also progressively destroy the brain, are caused by rogue particles called prions.
A team from Imperial College in London has discovered the development of prion disease can be prevented in mice using molecules produced by the immune system called monoclonal antibodies.
Prions are proteins that bind to normal proteins in the brain and twist them into abnormal shapes. These then clump together, causing brain damage.
We're making promising advances towards a possible treatment.
Monoclonal antibodies work by binding to both prions and normal proteins, blocking them from binding to each other.
Although the work is in its infancy and clinical studies with patients are some years away, the results raise the real possibility that a similar therapy might work on humans.
The Imperial team carried out a 17-month study on mice who were infected with prions which cause the disease scrapie.
Mice treated with monoclonal antibodies have shown no sign of developing scrapie - a year after the untreated mice succumbed to disease.
The monoclonal antibodies appear to have stopped the conversion of normal prion protein into the abnormal infectious form, preventing it accumulating.
A separate group of mice were given monoclonal antibodies, but only after they had started to develop signs of scrapie.
In this case, the treatment had no effect on slowing the course of the disease.
The next stage of the research will focus on trying to raise concentrations of monoclonal antibodies in the brain so that they have an impact on slowing the disease once it has begun to take hold.
Researchers also hope to genetically modify the monoclonal antibodies to make them more closely resemble human antibodies so they can be used in clinical trials.
Lead researcher Dr Simon Hawke warned that much more work was needed to translate the findings into a possible preventative treatment for humans.
But he said: "The good news is we're making promising advances towards a possible treatment.
"On one hand, if future tests can identify those who are ill before neurological disease sets in, then monoclonal antibodies might form the basis of a useful preventative treatment.
"Of course, the success of this strategy will depend on the availability of a reliable test to diagnose CJD in pre-symptomatic patients, which doesn't yet exist.
"On the other hand, if large enough concentrations of antibodies can be achieved in the brain, then treatment of patients with neurological disease might be possible, but we can't even begin to contemplate this until we've done work to humanise the antibodies."
Professor John Collinge, head of the Medical Research Council Prion Unit, said the results of the work were "extremely encouraging".
However, he said: "It is important not to raise false expectations and to emphasise that a considerable amount of further work - in particular to see whether these or other of our antibodies can block the progression of the disease in the brain when symptoms have developed - is necessary.
"Also, making these mouse antibodies compatible for humans is crucial if we are to use them as the basis of a treatment for people."
The research is published in the journal Nature.