Segmented Filamentous Bacteria in Gut Microbiota Protect Against Rotavirus

Gut microbiota could play a key role in the prevention or cure of rotavirus (RV) infection, according to a new study from investigators at Georgia State University.

The study, published in the journal Cell, offers a possible explanation for the wide variances in the presence and severity of the disease and could lead to new strategies to prevent and treat it.

“The whole thing was a surprise. We simply observed that a colony of mice was resistant to this virus,” senior author Andrew Gewirtz, PhD, a professor in the Institute for Biomedical Sciences at Georgia State University, told Contagion^®. “The resistance proved attributable to one bacterial species called SFB or segmented filamentous bacteria.”

Investigators noticed that mice bred at Georgia State University didn’t shed RV antigens while those purchased from the Jackson Laboratory did.

Using fecal transplant, the investigators were able to transfer rotavirus resistance. Co-housing also transferred the resistance. They also isolated two strains of bacteria—SFB-G and SFB-P—finding that RV resistance associated with SFB-G was much stronger. The presence of a microbiota in the mice administered SFB-G affected the extent of the RV protection, suggesting that other microbes play a role in resistance, possibly by supporting SFB colonization.

“SFB administration reduced RV shedding and decreased the incidence of RV-induced diarrhea in conventionally raised immunocompetent neonatal mice,” the study noted. “This observation provides a foundation for the development of new approaches to prevent and treat RV infection. However, because SFB promote development of Th17 cells, which is associated with, and may exacerbate, chronic inflammatory diseases, such approaches should be considered with caution.”

The study also noted that SFB are commonly found among the gut bacteria of children in China, where RV infection is relatively less severe.

Investigators also explored mechanisms that allow SFB to inhibit RV infection, with possibilities including that the bacteria act on RV directly or on the intestinal epithelial cells that RV bind to. The study found that SFB increased epithelial cell turnover, impeding RV.

The study was funded by the National Institutes of Health’s National Institute of Diabetes and Digestive and Kidney Diseases, and National Institute of Allergy and Infectious Diseases. Investigators have begun human studies in collaboration with the US Centers for Disease Control and Prevention.

Rotavirus is a highly contagious cause of diarrhea worldwide, causing severe, life-threatening disease in some people and mild disease in others. Rotavirus infections kills an estimated 215,000 children younger than 5 each year.

A recent study found that the virus can be transmitted in clusters inside vesicles in stool, which can travel through the gastrointestinal tract intact and are more infectious than individual viruses.

A vaccine is available for prevention of rotavirus infection, but there currently are no treatments for the disease. Another recent study found the vaccine to be effective, conferring a 94% lower rate of hospitalization for rotavirus infections and 31% lower rate of hospitalization for any reason in the first 2 months after vaccination. The vaccine also has been linked to a lower risk of type 1 diabetes.