Scientists from Johns Hopkins University say drugs manufactured from plants such as soya and corn could help prevent many emerging infectious diseases.

Writing in the January to March issue of Emerging Infectious Diseases, the scientists say drugs made with monoclonal antibodies (MABs) are already being used to treat diseases, but they offer a much greater potential for preventing people getting sick in the first place.

The drugs contain specially modified antibodies which lock onto and disable specific bacteria and viruses.

In the future, scientists predict they could coat the mucosal surfaces of the stomach, sex organs and respiratory tract, preventing infections from entering the body.

"There's finally an understanding of how important mucosal surfaces are," said Kevin Whaley, one of the authors of the report.

"Immunology, of course, has been around for ever and ever, but mucosal immunology is relatively new."

Over the counter

He predicts that the new drugs will be on the market, and possibly sold over the counter without prescription, before many of the much trailed vaccines for emerging infectious diseases.

"Soon, we believe, with the use of monoclonal antibodies, a person could take a small tablet for traveller's diseases in the stomach, a squirt from an inhaler for respiratory protection, and, for general urinary tract infection, put a gel or controlled-release device in the vagina.

Experiments on mice have shown MABs can stop the spread of genital herpes

"New sexual lubricants could also be produced to block transmission of sexually transmitted diseases."

Mr Whaley believes the drugs could be a way of getting around the growing threat of bacterial resistance to antibiotics.

"If we start talking about prevention rather than therapy, we can get these antibodies direectly to mucosal surfaces where they can prevent things from ever getting into the body and replicating," he said.

Mice

More than 80 MABs are currently in clinical trials, although it will take a few years for them to be tested on humans and be approved for use.

Earlier this month, scientists from Johns Hopkins said tests on mice had shown that an antibody manufactured from soy had stopped the spread of genital herpes.

The drugs, made in the lab, currently cost between $200 and $1,000 a gram.