May 18, 2009 A research team at Örebro University in Sweden has succeeded in changing the genes in plants so they can function as a vaccine against HIV. Through gene modification the plants have acquired the capacity to produce a protein that is part of the virus, and the project has taken a giant step forward in that mice that have been fed the plants have reacted and formed antibodies against the protein.
The findings are presented in a new academic dissertation at the university.
To produce drugs with the help of plants is a rapidly growing research field that offers new potential to combat diseases. At Örebro University researchers have the goal of developing inexpensive and safe protection against HIV, in the form of plants that contain a vaccine against the virus and can be cultivated all over the world. If they succeed, it will be difficult to exaggerate the significance of this for millions of people around the world, not least in the poorest countries.
“A major problem with the HIV virus is that it mutates rapidly and therefore exists in several different variants. In other words, it’s not possible to create an effective vaccine that is based on the entire virus. Moreover, this would be far too risky. Instead, we have selected a protein, p24, that exists in all HIV viruses and looks roughly the same in the various virus lines,” says Ingrid Lindh, author of the dissertation.
To get plants to produce the p24 protein, the gene that underlies the process must be a part of their own genetic make-up, but since it’s impossible to transfer the gene directly from the virus to the plant, the researchers had to take a detour. This was done by first placing the gene into a bacterium that could then transmit it to the plants. The attempt succeeded; the plants produced p24 and also passed on this ability to their offspring.
In the next phase, mice were fed with the p24 plants, and these trials also proved to be successful. The mice’s immune defense reacted just as the researchers had hoped, producing antibodies against the protein. In other words, this functioned as a vaccine. This raises hopes that a similar reaction in humans would make them immune to HIV.
“It is highly probable that the human immune system will respond in the same manner, but this is not to say that this would be sufficient to provide complete protection.”
To increase the potency of the vaccine, these scientists are therefore going to add more HIV proteins together with other compounds that reinforce the body’s reaction to HIV-specific proteins. In parallel with this, they will work to select a suitable vegetable that is easy to cultivate in different climates and is readily accepted in different cultures. Thus far, thale cress (Arabidopsis thaliana) has been used as an experimental plant, a common wild plant that is related to mustard and cabbage and has the great advantage of being well mapped genetically.
“The carrot is a good candidate for producing an edible vaccine, not least because it can be eaten raw, which reduces the risk of the proteins being destroyed by heating. What’s more, it’s a biennial, which means that it doesn’t go to seed the first year, making it easier to ensure that it doesn’t spread its genes to other plants close by,” explains Ingrid Lindh.
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