Fighting pathogens with plants
Of the vaccines available to doctors today, some (like influenza) are produced in eggs, some in cultured animal cells, and others in yeast. Arntzen's team has taken a different approach to vaccine production by converting tobacco plants into living pharmaceutical factories. They created a DNA blueprint for their Ebola vaccine, and used a specialized bacterium to infuse it into the leaves of tobacco. "The blueprint converts each leaf cell into a miniature manufacturing unit," Arntzen says.
In the current study, the vaccine blueprint was designed by fusing a key surface protein (known as GP1) from the Ebola virus with a monoclonal antibody customized to bind to GP1. The resulting molecules' opposite ends attract each other, like a group of rod-shaped magnets. When the vaccine molecules bind to each other, they form an aggregate called an Ebola Immune Complex (EIC). "In immunology, that means you've got something that is much easier for our immune system to recognize," Arntzen says. "Because it has many copies of an identical molecule, it's called a repeating array." (See Figure 2)
Within two weeks after the vaccine "blueprint" is delivered to tobacco leaves, enough of the EIC accumulates to allow its purification from other leaf cell components. The researchers then vaccinated mice with the purified sample, and showed that their immune system gave a strong response.
For the ultimate validation of the vaccine however, it was necessary to show that the vaccinated mice could withstand an Ebola virus infection. Because of the dangers in handling the virus, these experiments were conducted by skilled researchers at a high containment facility operated by the US Army Medical Research Institute in Maryland. It was found that the level of
|Contact: Joseph Caspermeyer|
Arizona State University