The successful immunisation of transgenic mice against the prion disease scrapie has raised the prospect of vaccines to combat vCJD and BSE.
Work by Adriano Aguzzi, a researcher at the Institute of Neuropathology, University Hospital of Zurich, Switzerland, will add to growing optimism that science might yet devise a way to tackle the neurodegenerative illnesses.
Professor Aguzzi said: "The bad news is nothing has been demonstrated in patients yet. The good news is the leads are promising."
This week, the Medical Research Council was asked to carry out clinical trials of an unrelated vCJD therapy - the anti-malarial drug quinacrine.
A British sufferer has already received the treatment in San Francisco after laboratory work suggested that it might be effective. But many scientists remain sceptical.
Vaccines have previously been discounted. Prion diseases such as vCJD, BSE and scrapie do not usually trigger an immune response. This may be because the prion protein is not recognised by the body as foreign. The diseases are believed to be caused by rogue proteins "corrupting" harmless versions produced in the body.
Professor Aguzzi's team created "knock-out" mice that did not possess the prion protein gene. When these animals were exposed to infective material, there was a strong immune response. This enabled the scientists to identify genes responsible for producing the antibodies.
They then created transgenic mice that had extra copies of the main scrapie antibody gene. When these animals were subsequently exposed to corrupted prions, they resisted infection.
Professor Aguzzi said the research, to be published in Science, was a proof of principle. His team is exploring strategies to develop this further.
"The ultimate goal is to develop a conventional vaccine where you give a shot to someone so they produce antibodies that neutralise the prions," he said.
The researchers will also look at whether this approach could be used to treat people already carrying abnormal prions. Epidemiologists estimate more than 100,000 Britons could be in this category.