Potato to prevent cervical cancer

US researchers hope to engineer a potato that carries a vaccine against the human papilloma virus (HPV).

In theory, this should provide an easy way to spread immunity at the dinner table.

Potatoes produced and tested by scientists at the University of Rochester, Cornell University and Tulane University provoked an immune response in mice that munched on the transgenic spuds.

And when enhanced with a substance derived from E.coli to boost their effectiveness, the potatoes provoked the immune system in the same way thought to be necessary to protect humans from the virus.

Researcher Dr Robert Rose said: "The beauty of an oral vaccine is that you don't need a needle.

"In most cases you don't even need a doctor."

Developing countries

Dr Rose said the potato vaccine could prove to be a highly effective way of protecting women in developing countries - where 80% of deaths from cervical cancer occur.

Currently, there is no HPV vaccine available. The only effective way to limit the spread of the virus is by practising safe sex.

The US researchers are also examining the possibility of using bananas as a vector for vaccines.

Potentially, they may be a better bet because, unlike potatoes, they are usually eaten raw, so there is no risk that the vaccine will be destroyed by the cooking process.

However, Dr Rose warned that the use of food-based vaccines would have to be tightly controlled.

"Any vaccine has to be prepared and administered in a controlled manner. The crop would be grown, evaluated, processed, and prepared into measured doses."

'Novel idea'

Dr Nigel Higson, chairman of the UK Primary Care Virology Group, said it would be nice to give a vaccine in something that could be eaten.

However, he said there were potential problems in regulating the dose, and in ensuring that the food did not start to rot.

He said the best solution to improve vaccine coverage was to invest in distribution, and education.

Professor Freda Stevenson, who is working on cancer vaccines at Southampton University, said the potato vaccine was just one of several approaches being develop for protecting against HPV.

She said it might prove difficult to protect a food-based vaccine from the digestion process.

But the concept of different types of vaccines for different diseases was a promising one.

"We need to change the way we think of a vaccine as something that comes out of a bottle and is taken by everybody.

"A vaccine for HPV would be extremely welcome, but the question is who do you vaccinate?

"It is not right to vaccinate everybody against everything. We should save vaccines for those people who are at risk."

HPV is a term used to describe a group of more than 80 different types of virus.

It is estimated that up to 15% of women aged 20 to 30 women and up to 6% of women over 40 carry the virus.

Not all types of HPV cause pre-cancerous changes, but certain strains stimulate the abnormal cell division associated with cancer.