Vaccines against Marburg and Ebola viruses advance.

Scientists have developed two new vaccines against the killer Ebola and Marburg viruses. In laboratory tests, the vaccines protected monkeys exposed to the viruses, which periodically infect people in Africa and cause hemorrhagic fevers marked by vomiting, diarrhea, shock, and organ shutdown. The report appears in the July Nature Medicine.

Researchers at the National Microbiology Laboratory of the Public Health Agency of Canada in Winnipeg, Manitoba, made the vaccines from a third, much less dangerous, virus that causes the livestock disease vesicular stomatitis. To make the vaccines, the researchers stripped the vesicular stomatitis virus of a particular gene and replaced it either with a gene that encodes a protein on the Marburg virus or with a gene for a protein on the Ebola virus.

The team then vaccinated four cynomolgus macaques with the Marburg vaccine and four others with the Ebola vaccine. Four weeks later, each group of animals received injections of the killer virus corresponding to its vaccine. All of the monkeys survived the normally lethal injections, says study coauthor Heinz Feldmann. Four other macaques given one or the other vaccine were exposed to the opposite virus. All died within 9 days.

Both vaccines elicited a strong antibody response, says Feldmann. The Ebola vaccine protected the monkeys against a viral subtype called Ebola Zaire. When the researchers exposed the four monkeys vaccinated against Ebola Zaire to another subtype of the virus, called Ebola Sudan, three of them died, indicating that separate vaccines may be needed against each Ebola subtype.

The vaccines might someday protect health care workers and other exposed people in sites of hemorrhagic-fever outbreaks, Feldmann says.--N S.