Viruses make chronic bowel disease worse

One to two percent of Flemish and Dutch people have chronic inflammatory bowel disease (IBD, after the English acronym). It usually involves Crohn’s disease or ulcerative colitis. They have persistent inflammation in the intestines, which leads to abdominal pain, diarrhoea, fatigue and fever.

There is no single cause of inflammatory bowel disease. It is a complex interaction between genetic predisposition and environmental factors. Previous research has already shown that the microbiome – the bacteria in the gut – plays a role. The immune system goes into overdrive in response to these bacteria. But viruses matter, too, according to new research.

US researchers used intestinal tissue from healthy people and people with inflammatory bowel diseases to make virus-like particles. They then exposed mice and human macrophages to this “virus.” Macrophages are part of the immune system: they remove harmful cells.

target elimination

Results? In healthy mice, the viruses suppressed inflammatory reactions. But in mice in which the researchers developed IBD, the viruses exacerbated symptoms. Human macrophages reacted the same way. When encountered with viruses from IBD tissue, this triggered an inflammatory response. When it comes to viruses from healthy tissues, this has happened much less.

“Our results suggest that viruses present in the healthy gut can help build immunity,” the researchers wrote in their paper in Science Immunology. “So not all viruses are dangerous.” The research could offer hope for new treatments against inflammatory bowel disease, targeting the virus. Virus eradication or replacement is a new strategy for treating intestinal and immunological diseases more broadly.