Bile acids help norovirus sneak into cells

A new study led by researchers at Baylor College of Medicine and published in the Proceedings of the National Academy of Sciences reveals that human noroviruses, the leading viral cause of foodborne illness and acute diarrhea around the world, infect cells of the small intestine by piggybacking on a normal cellular process called endocytosis that cells use to acquire materials from their environment.

The study found that two compounds present in bile – bile acids and the fat ceramide – are necessary for successful viral infection of a laboratory model of the human small intestine. In addition, the researchers report for the first time that bile acids also stimulate endocytosis in the small intestine. The findings support further exploration of the possibility of reducing norovirus infection by modulating the levels of bile acids and/or ceramide.

“Human noroviruses invade cells of the small intestine where they replicate and cause gastrointestinal problems,” said co-first author Victoria R. Tenge, graduate student of molecular virology and microbiology in Dr. Mary Estes’s laboratory. “Previous work from our lab showed that certain strains of norovirus required bile, a yellowish fluid produced by the liver that helps digest fats in the small intestine. In the current study, we investigated which bile components were involved in promoting norovirus infection.”

The researchers worked with human enteroids, a laboratory model of human intestinal cells that retains properties of the small intestine and is physiologically active.

“Mini-guts, as we call them, closely represent actual small intestine tissue, and, importantly, they support norovirus growth, allowing researchers to study how this virus causes disease,” said co-first author Dr. Umesh Karandikar, a research scientist in the Estes lab.

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