Researchers have developed a candidate vaccine against Ebola, one of the world's deadliest viruses. The vaccine, reported in January's Nature Medicine, has so far been tested only in mice and guinea pigs. But if it proves successful in humans, it could prevent feared outbreaks of the disease, which causes hemorrhagic fever and kills most of its victims within days.
Ebola gripped public attention in 1995 as it rampaged through Zaire killing 244 people. Like other viruses, Ebola doesn't elicit much of an immune response upon infection. By the time the immune system tries to send its fiercest immune warriors--antibodies and T cells--against the invaders, the virus has already blitzkrieged its way through the body.
Gary Nabel, a molecular virologist with the University of Michigan Medical Center in Ann Arbor, and Anthony Sanchez, a virologist at the U.S. Centers for Disease Control and Prevention (CDC) in Atlanta, created their candidate vaccine from snippets of the Ebola virus's DNA. In recent years, numerous research teams have shown that animals injected with a gene from a pathogen can incorporate the DNA into their cells and express its protein, triggering the immune system to create a standing army of antibodies and T cells specific to that protein.
Nabel's team selected a bit of Ebola DNA that codes for one of the virus's outer coat proteins, which allows the virus to wedge its way into host cells. The researchers stitched this DNA fragment into a circular piece of bacterial DNA called a plasmid, and injected these doctored plasmids into the muscles of guinea pigs. Guinea pig cells produced the Ebola protein, which then stimulated antibodies and T cells against it. When Sanchez later injected the vaccinated guinea pigs with lethal amounts of live Ebola, none of the effectively immunized animals became sick or died. "The result was really black and white," said Nabel.
Although Ebola outbreaks are relatively rare--fewer than 1000 cases have been reported worldwide--the virus poses a widespread threat, as Thomas Folks of the CDC points out in a commentary accompanying the paper in Nature Medicine. But before it can begin to combat that threat, this new vaccine will face careful scrutiny from health officials to ensure that it doesn't trigger cancer-causing genetic mutations when it incorporates into a cell's DNA. If it passes that test, Ebola may finally meet its match.