Progress made toward a vaccine for Ebola

an additional 284 cases and 151 deaths occurred in nearby Sudan. In Yambuku, the small local hospital was shut down, after eleven of its seventeen staff members died.

The likely reservoir for the disease is bats. Primates including monkeys can become infected from eating bats or from fruit the bats may have dropped.  Infected animals can then spread the disease to humans through bites, or when the primates are consumed for food — a practice prevalent in some regions of Africa.

The course of the disease is pitiless, sometimes producing hemorrhagic fever, which causes severe bleeding from mucous membranes, including the gastroinestinal tract, eyes, nose, vagina, and gingiva. The very high mortality and gruesome symptoms of the disease have riveted public attention and have been the focus of numerous films and books.

Arntzen notes that while no human vaccine against Ebola currently exists, a number of strong candidates have emerged. While some have yielded good results in animal models, in terms of protection against the virus, they have practical shortcomings. “All of these existing vaccine candidates are genetically modified live viruses,” he says. 

Vaccines of this sort require very careful conditions of storage and have a tendency to lose potency over a period of months. “If you’ve got something that you’re going to have to keep at liquid nitrogen temperatures for years at a time, in hopes that there will never be an outbreak, it makes it impractical. “

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.

The release notes that 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