Bat Detectives: Solving the Marburg Mystery

Courtesy Photo | 1968 F. A. Murphy; Cynthia Goldsmith This colorized negative stained transmission electron micrograph (TEM), captured by F.A. Murphy in 1968, depicts a number of Marburg virus virions, which had been grown in an environment of tissue culture cells. Marburg hemorrhagic fever is a rare, severe type of hemorrhagic fever which affects both humans and non-human primates. Caused by a genetically unique zoonotic (that is, animal-borne) RNA virus of the filovirus family, its recognition led to the creation of this virus family. The four species of Ebola virus are the only other known members of the filovirus family. See PHIL 7218 for a black and white version of this image. After an incubation period of 5-10 days, the onset of the disease is sudden and is marked by fever, chills, headache, and myalgia. Around the fifth day after the onset of symptoms, a maculopapular rash, most prominent on the trunk (chest, back, stomach), may occur. Nausea, vomiting, chest pain, a sore throat, abdominal pain, and diarrhea then may appear. Symptoms become increasingly severe and may include jaundice, inflammation of the pancreas, severe weight loss, delirium, shock, liver failure, and multi-organ dysfunction. Because many of the signs and symptoms of Marburg hemorrhagic fever are similar to those of other infectious diseases, such as malaria or typhoid fever, diagnosis of the disease can be difficult, especially if only a single case is involved.  

FORT BELVOIR, VIRGINIA, UNITED STATES

06.27.2018

Courtesy Story

Defense Threat Reduction Agency's Chemical and Biological Technologies Department

In 1967, a mysterious illness spread across Germany, infecting 31 people and resulting in seven deaths. Fifty years later, the virus that caused the illness, now known as Marburg, poses an even greater threat and treatment is largely limited to palliative care. Egyptian fruit bats are the reservoir host for the virus; however unlike humans, they remain asymptomatic. This has prompted scientists to take note in efforts to defend against the deadly disease.

Funded by the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department, researchers Gustavos Palacios, Ph.D., from the U.S. Army Medical Research Institute of Infectious Diseases, and Thomas Kepler, Ph.D., from Boston University, are now exploring the differences in antiviral immune response between humans and bats. Solving that mystery may unlock new ways to protect both civilians and our warfighters.

Previous research indicated that infected bats remain viremic for extended periods of time before clearing the virus. Researchers hypothesized that bats have potent antiviral defenses compared to other mammals, controlling viral replication until they mount an adaptive immune response.

Palacios and Kepler sought to identify these antiviral defense genes through genomic sequencing and compare the bat and human genes responsible. While the researchers did note that some bat immune system genes differ dramatically from their counterparts, they did not find evidence of a robust immune system.

Instead, they observed that some antiviral gene families have expanded in number, diversified and expressed at lower levels than would be expected. For example, humans have one copy of the type I interferon omega (IFN-ω) subtype, while the fruit bat’s genome encodes 22 functional copies of IFN-ω, which differ slightly from one another. The variety of IFN-ω subtypes may provide the Egyptian fruit bats with greater flexibility to exhibit a targeted response to infection.

Palacios and Kepler conclude that instead of having potent antiviral defenses that suppress infection, the Egyptian fruit bat is able to better tolerate infection of the Marburg virus.

The information from the completed genome project is assisting in the development of reagents as well as allowing controlled studies of Marburg virus in its natural host. By deepening our understanding of the increased immune response, DTRA CB is working to ensure effective protections for warfighters from deadly threats. For more information, visit the Cell article, “The Egyptian Rousette Genome Reveals Unexpected Features of Bat Antiviral Immunity.”

DTRA CB POC: Ashley Triplett, Ph.D.; [e-mail] USAMRIID POC: Gustavo Palacios; Ph.D. [e-mail]

• Date Taken: 06.27.2018
• Date Posted: 06.27.2018 09:31
• Story ID: 282431
• Location: FORT BELVOIR, VIRGINIA, US