Experimental Marburg Vaccine Provides Post-exposure Protection
Marburg virus, like its fellow filovirus Ebola, causes hemorrhagic fever and high death rates among humans. Also like Ebola, the virus is considered a potential bioweapon and has no known treatment or cure post-infection.
Developing a vaccine capable of providing protection against diseases like Ebola and Marburg after exposure has become a priority in light of known laboratory accidents and hypothetical first-responder scenarios. In 2009, a Hamburg scientist working with Ebola-Zaire accidentally pricked herself with a contaminated needle, setting off panicked global attempts by researchers to help her. Eventually the woman, a virologist from the Bernard Nocht Institute for Tropical Medicine, was given an experimental Ebola vaccine that had shown promise in preventing infection in monkeys when given post-exposure. She never developed the disease, although it’s not known whether the vaccine protected her from it. Prior to the Hamburg case, the previous known exposure was in 2004, in a U.S. Army researcher at Fort Detrick, Maryland.
These cases, in addition to hypothetical scenarios in which first responders may be exposed to filoviruses–coupled with the fact that no known treatment exists–have prompted efforts to further develop and test post-exposure vaccines.
An experimental Marburg vaccine was shown to provide such post-exposure protection for rhesus monkeys in 2006. Researchers exposed the monkeys to Marburg, then administered the vaccine within 30 minutes’ time. In that study, the vaccine was demonstrated to provide 100% protection against Marburg infection; however, the question of whether vaccination could be further delayed after exposure and still provide protection was left open.
Now, the same researchers have demonstrated that an experimental vaccine can provide some protection against Marburg infection up to 48 hours after exposure. In a study of 15 rhesus monkeys, six monkeys each were placed in two groups given the vaccine 24 hours and 48 hours post-exposure, respectively, and three monkeys were used as controls. Five of the six monkeys vaccinated a day after exposure survived; of the six vaccinated two days after exposure, two survived. The others, including the three controls, died between 10 and 12 days after exposure.
It is worth noting that of the seven vaccinated monkeys that survived, only two (both from the group vaccinated 24 hours after exposure) demonstrated no changes in either behavior or appearance to suggest illness. In five of the seven, blood tests showed changes throughout the course of the study, and signs of illness, including anorexia in one surviving monkey, appeared before eventually subsiding.
Although the protection provided by the vaccine was not absolute, the study is promising in that Marburg infections typically progress faster in monkeys than in humans. This suggests that, were the vaccine used in humans, it might be effective for an even larger post-exposure window than was demonstrated in the rhesus monkeys.
The study’s authors are affiliated with the National Emerging Infectious Diseases Laboratories Institute; the U.S. Army Medical Research Institute of Infectious Diseases; the Public Health Agency of Canada; and the National Institutes of Health. The Defense Threat Reduction Agency, the Division of Intramural Research of the National Institute of Allergy and Infectious Diseases, the National Institutes of Health, and the National Microbiology Laboratory of the Public Health Agency of Canada all provided funding for the research.
Geisbert TW, Hensley LE, Geisbert JB, Leung A, Johnson JC, Grolla A, et al. Postexposure treatment of Marburg virus infection. Emerg Infect Dis. 2010 Jul; [Epub ahead of print]
Link to paper: http://www.cdc.gov/eid/content/16/7/pdfs/10-0159.pdf
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Daddario-DiCaprio JM, Geisbert TW, Stroher U, Geisbert JB, Grolla A, Fritz EA, et al. Postexposure protection against Marburg haemorrhagic fever with recombinant vesicular stomatitis virus vectors in non-human primates: an efficacy assessment. Lancet. 2006;367:1399-404. PubMed DOI: 10.1016/S0140-6736(06)68546-2
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Link to article: http://news.sciencemag.org/scienceinsider/2009/03/researchers-aro.html