Could a normally harmless virus cause a sensitivity to gluten?
A new study has found that a certain type of virus could trigger a person's immune system to overreact to gluten, leading to celiac disease. The findings, published Thursday in Science, provide an explanation for why certain individuals develop celiac disease, while others do not.
"This is the first study to show that a virus can change the way our diet is seen by the immune system," Dr. Bana Jabri of the University of Chicago Celiac Disease Center and senior author of the study, told NBC News. The virus turns off the body's "peacekeeper" response to gluten, tricking the immune system into thinking gluten is a harmful invader that needs to be attacked.
Researchers at the University of Chicago and University of Pittsburgh infected mice with reoviruses -- a harmless type of virus that normally does not make people sick. The mice infected by reoviruses developed a super-charged immune system response when fed gluten, causing them to experience more of the inflammation specific to celiac disease. By comparison, the immune system of mice not infected with these viruses had a much milder response to gluten.
Jabri found these results in human patients as well. People with celiac disease had more antibodies to reoviruses in their blood compared to healthy individuals. Furthermore, these people with more antibodies were found to have more of the celiac disease inflammation.
Whether a person was infected with reoviruses at some point in the past could explain why they develop celiac at a certain age or had worse symptoms compared to others who were not infected, Jabri said.
An estimated 40 percent of the population have the genes that predispose them to celiac disease, but while 95 percent of people eat gluten, only 1 percent end up developing the disorder, said Dr. Paul Green, director of the Celiac Center at Columbia University in New York.
Viruses in the gut
Normally people are able to tolerate gluten without their immune system being put on alert. Celiac disease occurs when the immune system recognizes gluten, commonly found in wheat or other grains, as harmful. This causes the immune system to attack a person's small intestine, limiting their ability to absorb important nutrients. Symptoms include diarrhea, abdominal pain, bloating and anemia.
The reovirus link to an autoimmune response in the gastrointestinal system makes sense, Dr. Gerard Mullin, director of the Celiac Disease Clinic at Johns Hopkins School of Medicine told NBC News.
"We have more viruses in our gut than bacteria and we know very little about what they do at this point," said Mullin.
The University of Chicago team now wants to study children with genetic predisposition to celiac for evidence of reovirus infection. A New England Journal of Medicine study from two years ago showed that 30 percent of children who had the high risk "celiac genes" ultimately developed the disease.
In the future, families at high risk for celiac disease may change when they introduce foods containing gluten into a baby's diet. These same families may also consider vaccinating their children against reoviruses, although experts currently advise against testing for it. In addition, the United States Preventive Services Task Force recently recommended against routine screening for celiac.
Still, the new findings shed light on what some researchers see as a mysterious disorder.
"Now we can starting thinking about preventing celiac in a different way," Jabri said.
According to the Centers for Disease Control and Prevention, at least 3 million Americans have celiac disease, with 97 percent undiagnosed.
So why do some people with the disease-causing genes end up getting the disorder while others remain healthy?
"This study demonstrates the mechanism that a viral infection can cause a switch in the immune system that results in the development of food intolerance," said Green, noting that further study might show that other organisms such as bacteria may do the same.