There is nothing new (relatively speaking) in using tobacco plants to develop vaccines. Such plants have been displayed for at least a couple of years in the Wired Nextfest, the traveling circus of technology. What’s new now is the fact that scientists from the Biodesign Institute at Arizona State University have successfully used tobacco plants to develop a vaccine to combat the plague. The vaccine has been shown to elicit a protective immune response in guinea pigs:
“This current work represents a new direction in our research because we’ve come to the realization that plants also have the potential for the production of antigens that can be purified and delivered by typical intramuscular or subcutaneous injections – the way most vaccines are normally given,” said Mason, an associate professor in the School of Life Sciences. “This new system produces really high levels of antigens in relatively short periods of time.”
The researchers modified tobacco plants to make high levels of the plague antigens F1, V and a combination of the two, a so-called F1-V fusion antigen. All are known to be important for the plague bacteria to produce its toxic effects.
The antigens were purified from the plants and injected into guinea pigs. Testing using an aerosolized form of plague was performed by Chad Roy and Robert Webb at the U.S. Army Medical Research Institute of Infectious Disease at Fort Detrick, Maryland. This project was also the first comparison study designed to test more than one kind of antigen during the same challenge.
“The idea with any recombinant subunit vaccine is that you can pick and choose selective antigens that can confer protection and limit the potential for adverse reaction,” said Mason.
More than half the vaccinated animals survived the challenge with all forms of the antigen, and guinea pigs vaccinated with V antigen alone had the highest survival rates.
“This study provided validation of our plant expression system, that it can produce the bacterial antigens in a native form that will allow for an appropriate immune response against a bacterial pathogen.” Mason.
Critical to the success of the study was a collaboration set up with Anatoli Giritch, Victor Klimyuk and Yuri Gleba, who originally developed the plant expression system at Icon Genetics, located in Halle, Germany.
The group’s results are the first to use Icon’s viral expression system that adapts the tobacco mosaic virus (TMV) to produce a plant-based vaccine against plague. TMV, a common scourge of the plant world, causes widespread plant disease and can damage and mottle the leaves, flowers and fruits of whole crops. In the system, TMV is simply injected into the leaves of the tobacco plants.
Like most crops, producing vaccines in tobacco plants primarily revolved around issues of speed, low cost and high yield. “The major advantage of the vaccine is the rapidity of the system,” said Santi. “In a matter of 10 days, we can go from infecting the plants to harvesting the plants. From there, we purify the antigens in an additional one to two weeks to create the vaccine.”
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