Plan to grow Aids cream in tobacco plants
Date: 12.8.2006
A team of scientists led by Dr Julian Ma of the University of London is using transgenic tobacco plants to make affordable microbicidal vaginal creams that prevent HIV transmission.
Although condoms are the best defence against sexually transmitted HIV/Aids, women cannot always ensure their partners use protection. An internal application of the new HIV-prevention cream two to three times a week could help women take control of their sexual health.
The product could also renew the prospects of a cash crop now apparently being driven towards extinction in Kenya by anti-tobacco lobbies.
The HIV-fighting ingredient in the cream is Cyanovarin-N, a protein naturally produced by certain waterborne bacteria. To make a global impact, thousands of kilogrammes of the protein would be needed per year. This greatly exceeds any current laboratory capacity and would require significant infrastructure investments to keep up with demand.
Plants are some of the most efficient producers of proteins on the planet. Furthermore, tobacco farming has low production costs and is well-established in many of the areas hardest hit by Aids. This cheap and high-output combination means that Dr Ma's cream may be both affordable and accessible to those who need it most.
In Kenya, roughly 35,000 acres of agricultural land produce an estimated 15 million kg of tobacco leaf each year, according to David Mwambire, chief executive of the Tobacco Farmer's Association. And although Kenya's tobacco industry has burgeoned in the past 20 years, increases in cigarette taxes and the recent moves to ban smoking in public have left tobacco giants British American Tobacco and Mastermind uncertain of the future.
Alternative uses for the well-established cash crop would be welcome, according to researchers and Kenya’s estimated 200,000 tobacco farmers. "This is a very logical area for Africa to move into," said Dr Calestous Juma, a professor of international development at Harvard University, who chaired an African Union panel on biotechnology in Nairobi last week. "Africa has to think strategically and build on its existing expertise and infrastructure."
Cyanovarin-N is made by immersing tobacco leaf cuttings into a solution that contains genetically modified (GM) bacteria. The bacteria invade the plant cells and insert their genetic information into the plant's DNA.
As the cuttings grow into adult plants, the plants’ cellular machinery produces some of the bacteria's proteins, including Cyanovarin-N. When the adult tobacco plants are harvested, the protein is extracted and made into a cream.
When exposed to HIV-infected semen, the vaginally-applied Cyanovarin latches on to the virus, preventing it from attacking the woman’s immune cells.
Cyanovarin-N cream trials with monkeys decreased disease transmission by up to 80 per cent. Only three of the 18 animals using the cream contracted HIV, whereas the eight control animals were infected.
This is good news for women all over the world, but Dr Ma’s cream is still years away from being commercially available.
He hopes to grow enough of the drug in the UK to conduct human trials within the next three years. African governments may be wary of transgenic tobacco because there are several risks associated with growing GM crops, including the contamination of surrounding non-GM crops.
Dr Ma avoids this problem in the United Kingdom by working in a high-security, airtight greenhouse normally used for research on plant viruses. If the GM tobacco was grown in East Africa, the plants would have to be further genetically modified for sterility to prevent their cross-pollinating natural crops.
Even if the drug is approved, mass production is still a long way off. Dr Ma estimates 5,000 kg of Cyanovarin-N would be needed to provide 10 million women with the necessary biweekly dose. At current rates of drug extraction, Kenya's entire tobacco industry would only produce enough cream for about 3.9 million women.
"Source":[ http://www.checkbiotech.org/root/index.cfm?fuseaction=news&doc_id=13261&start=1&control=160&page_start=1&page_nr=101&pg=1]
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