Protection from BSE and its human equivalent is possible after all

September 15, 2001 New Scientist by Andy Coghlan
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's 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 Scientist, 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 BSE hits Japan).

"There is now some hope," says Frank Heppner who, with Adriano Aguzzi, leads a team at the University of Zurich's 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 "rogue" 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's Hospital, London, showed that the antibodies shield the normal form of the prion, preventing rogue versions from reshaping them in their own image (New Scientist, 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 - developed by the Swiss company Prionics at the University of Zurich - work 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. "If you can completely disrupt formation of this intermediate stage, you could prevent the disease," says Yee. "It looks like that's what the antibodies are doing."

"It looks a lot more hopeful now than it did as little as a couple of months ago," 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. "If you immunise all cattle from birth, you could exclude it from the food chain," he says. v

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