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Over the past few decades, the incidence of Crohn’s disease and other forms of inflammatory bowel disease (IBD) have been rising throughout the world. But what is the reason for this increase? Given that the exact cause of Crohn’s disease is unknown, it can be difficult to identify what factors could contribute. However, a recent study suggests that a fairly common norovirus infection could trigger Crohn’s disease. 

According to Medical News Today, prior research suggested that norovirus infection (murine norovirus, or MNV) killed paneth cells (specialized cells in the small intestine epithelium) in mice. When paneth cells are properly functioning, they protect against intestinal inflammation. But these mice models had Atg16l1, leading to fewer functioning cells. 

Exploring the Research

So in this more recent study, researchers wanted to better understand how MNV affected protective T cells in the gut. To begin, the research team examined two separate groups of mice, one group which had the mutation and one which did not. Findings from the study, which are published in Nature, include:

• Mice with the genetic mutations had immune molecules that secreted apoptosis inhibitor 5 (API5), a type of protein. In these mice models, API5 helped to increase the amount of functioning paneth cells. 
• After MNV exposure, mice with Atg16l1 mutations became unable to secrete API5. This ultimately caused intestinal damage. 
• Researchers treated the mice models by increasing API5. 50% of mice who were not treated died. 100% of treated mice survived. 
• After analyzing samples of human intestinal tissue, the research team found that Crohn’s disease caused there to be lower levels of API5 within the immune system. When treating these samples with API5, immune protection increased.

Ultimately, more research is needed to better understand the relationship between Crohn’s disease and norovirus infection. While the study found a potential correlation, they did not find definitive evidence of norovirus triggering Crohn’s disease. Therefore, it can only be considered a possible trigger. 

Additionally, there needs to be more research into API5 and Crohn’s disease. Is API5 only important for people with this specific gene variant, or could it benefit those with Crohn’s disease without this variant? Would using API5 in some way help to develop novel therapies for Crohn’s disease? While the answers are still uncertain, it will be interesting to see what further research uncovers. 

What is Crohn’s Disease?

Crohn’s disease, which exists under the umbrella of inflammatory bowel disease, causes chronic inflammation of the digestive tract. It is most common in the colon and ileum, though it can impact other areas of the digestive tract. Crohn’s disease most often affects those ages 30 or younger. It is more prevalent in those who are Caucasian or who are of Ashkenazi Jewish descent. While Crohn’s disease can be managed, its complications can be serious and life-threatening. Therefore, if you have Crohn’s disease and are experiencing issues like bowel obstructions, ulcers, severe pain, or malnutrition, it is extremely important to seek help from your care team as soon as possible. 

Symptoms of Crohn’s disease vary in presentation and severity. Some may experience periods of symptoms and periods of remissions, while others experience less or no remission. Symptoms can (but do not always) include:

• Fever
• Fatigue
• Appetite loss
• Unintentional weight loss
• Diarrhea
• Bloody stool
• Abdominal pain and cramping
• Rectal/anal pain and drainage
• Mouth sores
• Anemia (low red blood cell count) 
• Slowed growth
• Excessive bloating or flatulence