Scientists have found that just one greenhouse can produce a million doses of virus-blocking chemical, giving new hope that one day an anti-HIV protein may be derived from plants.
A research article on this finding suggests that a protein produced in Nicotiana benthamiana, a member of the tobacco family, could be the basis of a new HIV microbicide.
While scientist have already used plants to make large amounts of a protein that could help prevent the transmission of HIV, the latest finding brings the prospect of a commercial protein-based microbicide for HIV a step closer, says the article.
The researchers in America and Britain used a modified form of the tobacco mosaic virus, and introduced genes into N. benthamiana so that it would produce the protein made by red algae called griffithsin (GRFT).
They point out that lab studies on human cells have previously shown that GRFT is effective against HIV, suggesting that the protein binds to the virus' surface and stops it from infecting healthy cells.
"Proteins have been shown to provide some of the most effective protection against HIV, and GRFT is perhaps one of the most potent inhibitors yet described," Nature magazine quoted Kenneth Palmer, a virologist at the University of Louisville, Kentucky, who led one of the teams, as saying.
Giving yet another reason why the new findings attain significance, the researchers say that scientists have tried modifying plants before to express the desired proteins in an attempt to bring down costs, but the plants have to date failed to make enough of the proteins.
"The best candidates for microbicides are either protein-based or made from small molecule drugs. But recently, the appetite for protein microbicides has waned because people could not see a way of producing them at quantity or (low) cost," says Julian Ma, a molecular immunologist at St George's Hospital, at the University of London, UK.
"This is a landmark study because it shows for the first time that proteins can be produced in large quantities, so it brings back the possibility of producing protein microbicides," adds Ma, who also researches the production of protein drugs in plants.
Palmer has revealed that the research team harvested over 60 grams of GRFT from N. benthamiana plants in a greenhouse with an area of 460 square meters.
He reckons that this amount of GRFT could produce roughly one million doses of microbicide, administered as a gel.
"This is the first realistic manufacturing process for producing proteins in plants," he says.
The researcher adds that the researchers chose N. benthamiana because it is very susceptible to viral genetic modification, and because it can be grown at high densities in greenhouses.
The findings of the study have been reported in the Proceedings of the National Academy of Sciences USA.