THE prospect of a cheap and effective edible HIV vaccine for humans now looks more likely, thanks to maize that has been genetically modified to produce a key protein from the monkey version of HIV.
The monkey virus protein, known as SIV gp120, is the simian form of a protein that will be used in an HIV vaccine trial on people in Thailand later this year. Researchers will give injections of a canarypox virus modified to contain HIV genes, plus a booster shot of HIV gp120. This protein should trigger the production of antibodies that fight HIV infection if it occurs.
But injected HIV gp120 won鈥檛 provoke a strong enough immune response in the mucosal layers of the body, which are the usual point of entry for the sexually transmitted virus. 鈥淭o have a good mucosal immune response is really important,鈥� says Stuart Shapiro of the National Institute for Allergy and Infectious Diseases in Bethesda, Maryland.
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The hope is that an edible vaccine would spark a strong mucosal immune response when it comes in contact with the stomach and intestines. 鈥淎 mucosal vaccine is safer than an injectable vaccine in the developing world, where needles get reused and are not sterilised properly,鈥� adds Shapiro.
Now the US company ProdiGene in Texas has genetically engineered maize to include the genes for SIV gp120. It has shown that the maize can express the monkey virus protein, and the company will feed it to mice to gauge their immune response. 鈥淲e can then take it and feed it to monkeys in our labs, and see not only if we get a response but if that response protects against SIV,鈥� Shapiro says.
If all goes well, it will be easy to swap the monkey virus genes for the human ones to produce large amounts of HIV gp120 in maize, says Shapiro. 鈥淚t would be very stable, so it could be dried and stored for long periods of time and safely shipped,鈥� he adds.