Gut microbes protect against neurologic damage from viral infections

July 16, 2019

Gut microbes produce compounds that prime immune cells to destroy harmful viruses in the brain and nervous system, according to a mouse study published today in eLife.

The findings suggest that having a healthy and diverse microbiota is essential for quickly clearing viruses in the nervous system to prevent paralysis and other risks associated with diseases such as multiple sclerosis.

A condition that causes progressive damage to nerve cells, multiple sclerosis has become more common over the past several decades. Viral infections in the brain or spinal cord are thought to trigger this disease. Some scientists believe that changes in the way we eat, increased sanitation or growing antibiotic use may be causing detrimental changes in the helpful bacteria that live within the human body, potentially increasing the risk of multiple sclerosis and other related diseases.

"We wanted to investigate whether gut microbes could alter the immune response to a virus in the central nervous system and whether this affects the amount of damage the virus causes," says one of the lead authors David Garrett Brown, a graduate research assistant in the Department of Pathology at University of Utah Health, Salt Lake City, US.

To do this, Garrett Brown and co-lead author Ray Soto looked at the effect of Mouse Hepatitis Virus, a virus that infects cells in the mouse nervous system and causes multiple-sclerosis type symptoms, on two groups of mice: some with normal gut microbes and some that were bacteria-free. They found that bacteria-free mice had a weak immune response, were unable to eliminate the virus and developed worsening paralysis, while those with normal gut bacteria were better able to fight off the virus.

Mice treated with antibiotics before the onset of disease were unable to defend themselves. They also had fewer immune cells called microglia, which help flag viruses for destruction by other immune cells.

Next, the team identified compounds produced by gut bacteria that might help the microglia. When they administered these helpful compounds to the bacteria-free mice, they saw that the animals were protected from neurologic damage caused by the virus.

"We've shown that gut microbes protect infected mice from paralysis by turning on a specific pathway in central nervous system cells," explains June Round, Associate Professor in the Department of Pathology at University of Utah Health, and a senior author of the study. "This suggests that signals from microbes are essential to quickly clear viruses in the nervous system and prevent damage from multiple sclerosis-like diseases. Our results emphasise the importance of maintaining a diverse community of bacteria in the gut, and that interventions to restore this community after taking antibiotics may be necessary."
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Reference

The paper 'The gut microbiota protects from viral-induced neurologic damage through microglia-intrinsic TLR signaling' can be freely accessed online at https://doi.org/10.7554/eLife.47117. Contents, including text, figures and data, are free to reuse under a CC BY 4.0 license.

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Julie Kiefer, Associate Director, Science Communications
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About eLife

eLife is a non-profit organisation inspired by research funders and led by scientists. Our mission is to help scientists accelerate discovery by operating a platform for research communication that encourages and recognises the most responsible behaviours in science. We publish important research in all areas of the life and biomedical sciences, including Microbiology and Infectious Disease, which is selected and evaluated by working scientists and made freely available online without delay. eLife also invests in innovation through open-source tool development to accelerate research communication and discovery. Our work is guided by the communities we serve. eLife is supported by the Howard Hughes Medical Institute, the Max Planck Society, the Wellcome Trust and the Knut and Alice Wallenberg Foundation. Learn more at https://elifesciences.org/about.

To read the latest Microbiology and Infectious Disease research published in eLife, visit https://elifesciences.org/subjects/microbiology-infectious-disease.

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