An accidental discovery in mice may lead to a cure for one of the world’s most deadly infections.

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Researchers have identified a bacterial species in the gut microbiota that protects against highly contagious rotavirus (pictured).

The World Health Organization (WHO) estimate that each year, 215,000 children worldwide under the age of 5 years die from dehydration due to severe diarrhea.

An untreatable rotavirus infection is responsible for these cases.

Now, researchers at the Institute for Biomedical Sciences at Georgia State University (GSU) in Atlanta have identified specific intestinal microbiota, or microorganisms, that can prevent and cure rotavirus infections.

Their study findings appear in the journal Cell.

“This study,” says senior author Andrew Gewirtz, “shows that one big determinant of proneness to rotavirus infection is microbiota composition.”

Rotavirus gets its name from “rota” — the Latin word for “wheel” — as the virus has a round shape. It most commonly affects infants and young children, and it spreads easily. People with the virus can transfer it by sneezing and coughing or by using unwashed or improperly washed hands to touch, and thus contaminate, surfaces and objects.

The virus can transfer between people via surfaces such as counters and sinks, as well as on shared toys, tools, and utensils.

Vaccines prevent infection in most cases and reduce the chance of a severe infection. The Centers for Disease Control and Prevention (CDC) estimate that the rotavirus vaccine prevents 40,000 to 50,000 hospitalizations in the United States annually.

According to the CDC, the symptoms of infection include “severe watery diarrhea, vomiting, fever, or abdominal pain,” with diarrhea and vomiting typically lasting for 3 to 8 days.

In areas with an adequate supply of clean water, the administration of fluids prevents life threatening dehydration.

Unfortunately, this is not the case everywhere, and rotavirus infection is particularly deadly in some low income parts of the world.

Rotavirus infections can be mild or severe, and the reasons for this remained unknown until the discovery by the GSU researchers.

As the authors explain in their paper, “[rotavirus] clearance typically requires adaptive immunity,” but in this case, the scientists “unintentionally” created a model of immunodeficient mice that were also resistant to the virus.

So, the scientists hypothesized that this might be due to “select microbes” that offered protection against the virus. To verify their hypothesis, they tested whether the virus “resistance was transferred by co-housing and fecal transplant.”

This discovery was serendipitous. We were breeding mice and realized that some of them were completely resistant to rotavirus, whereas others were highly susceptible. We investigated why and found that the resistant mice carried distinct microbiota. Fecal microbiota transplant transferred rotavirus resistance to new hosts.”

Andrew Gewirtz

The researchers eventually found that a single bacterial species called Segmented Filamentous Bacteria (SFB) was the primary factor in determining an individual’s resistance to rotavirus infection.

SFB also reduces the damage that the rotavirus causes by initiating both the shedding of infected epithelial cells and their replacement with new, healthy ones.

“It’s a new basic discovery that should help understand proneness to rotavirus infection,” notes Gewirtz.

The discovery by the GSU team is just a first step toward combating rotavirus in humans.

First author Zhenda Shi, who works at the CDC’s rotavirus branch, is currently looking into how relevant this discovery in mice is for humans.

As Gewirtz points out, the team’s research “does not yield an immediate treatment for humans but provides a potential mechanism to explain the differential susceptibility of different populations and different people to enteric viral infection.”

“Furthermore, it may lead to new strategies to prevent and treat viral infections,” he concludes.