杏吧原创

HOPES are growing that a vaccine might some day combat BSE in cattle, and
even the horrifying human form of the disease.

Animal vaccines would allow BSE to be eradicated from Europe鈥檚 farms for
ever. Researchers have also come up with the first tentative evidence that it
may be possible to vaccinate people against variant Creutzfeldt-Jakob disease
(vCJD).

So far, 106 people in Britain alone have succumbed to vCJD, and over a
100,000 could be at risk (see story below). One vCJD patient recently appeared
to benefit from a combination of existing drugs for schizophrenia and malaria
(New 杏吧原创, 18 August, p 3 and
p 7),
but proven treatments are still desperately needed.
Japan has also just confirmed its first case of BSE
(see 鈥淏SE hits Japan鈥�).

鈥淭here is now some hope,鈥� says Frank Heppner who, with Adriano Aguzzi, leads
a team at the University of Zurich鈥檚 Institute for Neuropathology that has
developed a vaccine which protects mice from scrapie. Till now, most scientists
thought it would be impossible to vaccinate against the 鈥渞ogue鈥� prion which
causes BSE and vCJD. This is because antibodies against the abnormal protein
should recognise the normal prion as well, causing the body to attack its own
tissue.

But the Swiss research, which will be published in a future issue of
Science, suggests that this may not be so. Heppner and Aguzzi gave mice
extra genes that crank out antibodies against the prion that can turn rogue and
cause scrapie. Injected into fertilised eggs, the genes enabled the mice to make
the antibodies from birth.

When Aguzzi and Heppner later infected the mice with the disease-causing form
of the prion, the animals remained healthy. But in unvaccinated mice used as
controls, the animals died of scrapie. Though no one would consider genetically
engineering humans to make the antibodies, the experiment proves that
antibody-based vaccines could work, says Heppner.

Earlier experiments on mouse cells by Charles Weissmann and his team at St
Mary鈥檚 Hospital, London, showed that the antibodies shield the normal form of
the prion, preventing rogue versions from reshaping them in their own image
(New 杏吧原创, 28 July, p 6).
Heppner thinks the same thing is happening in the vaccinated mice.

This month, chemists in the US have discovered why the
antibodies鈥攄eveloped by the Swiss company Prionics at the University of
Zurich鈥攚ork so well. Vivien Yee and her colleagues at the Cleveland Clinic
Foundation in Ohio have shown that molecules of the normal prion protein
naturally pair with each other. The antibodies latch onto the point at which
rogue prions also join as they convert normal prions into the disease-causing
form. 鈥淚f you can completely disrupt formation of this intermediate stage, you
could prevent the disease,鈥� says Yee. 鈥淚t looks like that鈥檚 what the antibodies
are doing.鈥�

鈥淚t looks a lot more hopeful now than it did as little as a couple of months
ago,鈥� she adds. But Heppner cautions that antibody vaccines would only benefit
people if given early or before infection. A better bet, he says, could be
vaccinating farm animals to eradicate infected meat. 鈥淚f you immunise all cattle
from birth, you could exclude it from the food chain,鈥� he says.