UF researchers discover how to cultivate norovirus in human cells
noroviruses are pernicious intestinal viruses. They cause violent vomiting and diarrhea, and people ill with the virus remain contagious up to three days after they seem to recover. Although a vaccine for these viruses is in clinical trials, there is still no medication to combat them. That’s in part because researchers have not been able to culture human noroviruses so they can test potential treatments — until now, according to a study by University of Florida Health researchers published in the journal Science.
UF Health researcher Stephanie Karst, Ph.D., has found a way to grow a human norovirus by identifying a cell it targets in the intestine.
“The biggest hurdle to doing norovirus research for its entire history — it was discovered in 1972 — has been that we can’t culture the human viruses in a cell culture dish,” said Karst, an associate professor in the department of molecular genetics and microbiology in the UF College of Medicine. “That complicates every aspect of research. We can’t study how it replicates, we can’t test therapeutics and we can’t generate live virus vaccines.”
Previously, researchers speculated that noroviruses primarily target intestinal epithelial cells, which line the intestine and protect it from pathogens, Karst said. However, this new research demonstrates that the virus targets B cells, a type of white blood cell common in the intestine.
“That’s a big surprise,” Karst said. “You would think that any virus that’s going to target the intestine would instead target the intestinal epithelial cells because that’s the first cell the virus is going to encounter.”
Researchers also were surprised to find that bacteria present in the body’s gut flora, also known as commensal bacteria, helped the human norovirus infect B cells. Karst said scientists have long known that noroviruses need a particular kind of carbohydrate to infect cells.
“What we’ve shown is that noroviruses attach to that carbohydrate expressed on commensal bacteria, and that this interaction stimulates viral infection of the B cell,” Karst said. “This is a really exciting, emerging theme. A variety of intestinal viruses seem to exploit the bacteria that are present in our intestines all the time. These viral infections are enhanced by the presence of bacteria in the gut.”
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