Defending against a deadly foe: vaccine forestalls fearsome virus.

A single injection of an experimental vaccine prevents infection by the lethal Marburg virus in monkeys, a study finds. The test is the first to show that a vaccine given after exposure to the virus can stop it. People infected with Marburg, a cousin of the Ebola virus, develop high fever, nausea, and internal bleeding and often die.

Scientists had previously demonstrated that the vaccine could avert Marburg virus when administered a month before exposure (SN: 7/16/05, p. 45). The new research comes closer to simulating real-world conditions, in which exposure to Marburg virus arises unpredictably in natural outbreaks or in laboratory accidents.

The virus is named for Marburg, Germany, where it was first identified in 1967 after infected monkeys shipped there from Uganda spread the virus to people. Since then, sporadic outbreaks have occurred in Africa.

Using extreme biosafety precautions, researchers injected eight rhesus macaque monkeys with Marburg virus. Within 30 minutes, they gave five of the animals a single shot of the vaccine. The three others got an inert substance.

The immunized animals survived the 80-day test and showed no sign of the virus in their blood, says Thomas W. Geisbert, a virologist at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick in Frederick, Md. The three unvaccinated monkeys died within 12 days of exposure to Marburg, Geisbert and his colleagues report in the April 29 Lancet.

Scientists made the vaccine by replacing a gene in an innocuous livestock virus with a gene that encodes a glyco-protein on the surface of the Marburg virus. This recombinant virus attracts the attention of a mammal's immune system, which then makes antibodies that foster immunity against the Marburg virus, says study coauthor Heinz Feldmann, a virologist at the National Microbiology Laboratory of Canada in Winnipeg.

"It's incredible that they are able to show that the [vaccinated] monkeys stayed healthy after such a high dose" of Marburg virus, says Luciana Borio, an infectious-disease physician at the Baltimore, Md., office of the Center for Biosecurity of the University of Pittsburgh Medical Center.

Feldmann and Geisbert envision that the vaccine would be given as a precaution to health workers during an outbreak and to family members of infected people. It could also rescue lab workers exposed to the virus by needlesticks or other accidents, Geisbert says.

Pharmaceutical companies might find this vaccine difficult to get approved and ultimately unprofitable because the disease is uncommon, Borio says. She considers distribution of a Marburg vaccine, beyond a cache for lab safety, "a long shot."

However, the former Soviet Union had developed bioterror weapons based on Marburg and other viruses. If there were a bioterror attack using Marburg, previous assumptions about the economics of vaccine production would "go out the window,' Borio says.

STATS

88% Death rate among the 374 people infected by Marburg virus in an outbreak in Angola last year