Microbes in Gut Protect Nervous System After Viral Infections, Study Suggests

July 22, 2019

by Jose Marques Lopes, PhD


Microbes in Gut Protect Nervous System After Viral Infections, Study Suggests

Gut microbes prime immune cells called microglia to protect the brain and nervous system from neurological damage due to viral infections, according to new research in mice.

The findings suggest that maintaining a healthy and diverse microbiota — the population of bacteria, fungi, and viruses within the body, especially the gut — is key to efficiently clear viruses in the nervous system, and to prevent the disease-related changes that mark multiple sclerosis (MS) and other disorders, the investigators said.

The study, “The microbiota protects from viral-induced neurologic damage through microglia-intrinsic TLR signaling,” was published in the journal eLife, and conducted by researchers at University of Utah School of Medicine.

Viral infections in the central nervous system (CNS) are considered a potential cause of MS and other diseases. Such infections usually target CNS cells, which makes the work of virus-specific lymphocytes more difficult. These immune cells need to eliminate the virus while limiting possible long-term consequences to the host, like excessive inflammation.

According to the team, a better understanding of antiviral defenses may lead to more effective therapies to prevent or treat neurologic disorders like MS.

Increasing evidence suggests that microbiota in the gut impact microglia, a type of glial cell that acts as a first defender against infectious agents across the brain and spinal cord. Research has also indicated that gut microbes may influence viral infections, though results here are contradictory.

As different viruses can be associated with distinct effects of intestinal microbiota, the scientists focused on the mouse hepatitis virus that rapidly leads to alterations similar to those of MS, including loss of myelin — the insulating layer of nerve fibers.

“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,” David Garrett Brown, a graduate research assistant in the department of pathology at University of Utah Health, and the study’s first author, said in a press release.

Mice with a normal population of gut microbes were compared to germ-free animals, and to mice treated with antibiotics before the onset of disease.

Results showed that animals free of microbes or given antibiotics had a weaker immune response, an inability to clear the virus,  a greater loss of myelin in the spinal cord, and worse paralysis.

These animals also had a lower number of virus-specific immune T-cells in the brain and fewer microglial cells, including the subset responsible for activating antigen-specific T-cells. Levels of CD86 and CD4, two proteins involved in initiating an immune T-cell response to antigens, were also decreased.

Subsequent experiments looked to identify molecules produced by gut microbiota to assist with microbial protection. Among other types of compounds tested, oral administration of toll-like receptor (TLR) ligands eased neurologic damage in germ-free mice, while also increasing the number of T-cells in the brain and helping to clear the viruses. Of note, TLR proteins are well-known for their role in defenses against microbial infection.

Specifically, the investigators found that activating microglia depends on signaling through the TLR4 protein — a member of the TLR family associated with chronic inflammatory conditions — as disrupting this protein within microglia aggravated viral-induced disease.

“We’ve shown that gut microbes protect infected mice from paralysis by turning on a specific pathway in central nervous system cells,” June Round, one of the study’s co-senior authors, said in the release.

“This work demonstrates that gut immune-stimulatory products can influence microglia function to prevent CNS damage following viral infection,” the team wrote.

The findings “emphasize 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,” Round concluded.


  1. Robin says: July 22, 2019 at 10:19 AM I’m so tired of 101 excuses why people are getting sick and especially with brain problems. The FDA and EPA has let our water and food become toxic. 70 million autoimmune illnesses in the US. Cancer rates are soaring. One out of every three child is sick with something. One every four person in the US is on mental medicine. These new rare diseases pots, CFS, fibro, ect. are at a epidemic. One in every nine boy gets autism. The US is sicker than any other country in the world. We have been poisoned. My grandmother’s generation did not get these kind of illnesses. That blows the genetic factor away/does not exist!!! People better start thinking on their own fast. At this rate the population won’t exist.
    • Mike says: July 22, 2019 at 3:35 PM We have been and are being poisoned IN THIS COUNTRY.
      Thank the ‘elected’ government people – doesn’t matter their color or rhetoric, if it did, America and it’s native born would not be in the condition it’s in.
      Save the children.
    • Karen Burmark says: July 22, 2019 at 3:55 PM I do agree with most of what you said, Robin, there is much damage to our environment that has messed us up and will, unfortunately, continue to do so. However, with 4 of us in my family, all on the mother’s side, all living hundreds of miles apart, there is a genetic piece at play, too, in my opinion.
    • Robert says: July 23, 2019 at 6:06 AM Very true, yet, autoimmune and chronic disease conditions also exist in countries with very high quality of life and environment, such as Scandanavia. And, we must not omit the mental health reasons for chronic illness, including MS, breast cancer, etc. Dr. Gabor Mate’s research and writings are fine source of details on this. The mental health/emotional repression aspect doesn’t draw headlines, and nobody wants to admit that their own emotional repression caused their illness.
  2. Judith W. Salsbery says: July 22, 2019 at 1:07 PM An excellent article and what an encouragement to those of us with related health issues. I am a former immunology research scientist and had my gut biome damaged after a series of Cipro treatments. I have been working for years to try to get back to where I once was. I have always thought the answer was in the gut biome and am so encouraged as I read of the research of others. I pray for funding that these studies may continue. Reply
    • Greg Vond says: July 22, 2019 at 2:48 PM Hi Judith. Do you take probiotics? I was taking them for a while but stopped when I didn’t see any benefit
    • Linds says: July 24, 2019 at 1:34 AM Is there a test to see if gut biome has been damaged? I just came off a year of various and very strong antiobiotics. Thanks. Reply
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