Washington: Inflammatory bowel diseases may be associated with an increase in the diversity of viruses in the body, scientists say.
Researchers at Washington University School of Medicine in St Louis found that patients with inflammatory bowel diseases had a greater variety of viruses in their digestive systems than healthy volunteers, suggesting viruses likely play a role in the diseases.
Scientists have only recently started recognising the role of the microbiome - the bacteria in and on the body, and the bacteria's genes - in illness.
Changes in the gut microbiome have been linked to obesity, diabetes, metabolic syndrome and inflammatory bowel diseases.
The new research is the first to associate disease with changes in the virome, or the viruses in the human body and their genes.
According to the researchers, the results raise the possibility that viruses may have unrecognised roles in obesity and diabetes and the two most common inflammatory bowel diseases, Crohn's disease and ulcerative colitis.
"This is the tip of the iceberg. A significant portion of the viral DNA we identified in these patients is unfamiliar to us - it comes from newly identified viruses we don't know much about," said senior author Herbert W Virgin.
"We have a great deal of groundwork to do, including sequencing the genetic material of these viruses and learning how they interact with the gut and gut bacteria, before we can determine if changes in the virome cause these conditions or result from them," Virgin said.
Virgin and his colleagues studied three groups of patients with Crohn's disease or ulcerative colitis living in Chicago, Boston and the UK.
In each group, they compared viral DNA purified from the feces of participants with viral DNA from the feces of healthy people living in the same areas and, in some cases, the same homes.
"Much of the increased viral diversity in participants with inflammatory bowel diseases was in the form of bacteriophages, which are viruses that infect bacteria and can incorporate themselves into the bacteria's genetic material," said Virgin.
Changes in the gut that eliminate bacteria in inflammatory bowel diseases may unleash bacteriophages in the dying bacteria, Virgin speculated.
Or the introduction of a new bacteriophage to the gut, perhaps through the foods in a person's diet, may trigger a reaction in the digestive system or the microbiome that causes the disorders, he said.
It's also possible that a combination of these mechanisms may contribute.
The research appears in the journal Cell.