A new study may have solved a mystery surrounding the Crohn’s disease, an inflammatory bowel disease in which the immune defenses, destined to attack invading microbes, instead mistakenly target the digestive tract of the body. Norovirus, a common infection that causes vomiting and diarrhea, is one of several viruses and bacteria thought to trigger the onset of the disease in Crohn’s patients, but the field doesn’t know why.
The results of the Research have been published in the scientific journal Nature.
Norovirus and Crohn’s disease: here’s what the new study revealed
A clue emerged when previous studies found that some genetic change (mutation) is present in the majority of patients with this condition. This mutation makes the cells of the gut lining more vulnerable to damage. The mystery deepened again, however, when it was learned that half of all Americans have the same genetic mutation that confers the risk, but fewer than half a million develop Crohn’s.
New applied research in mice and human tissues revealed for the first time that in healthy individuals, immune defenders called T cells secrete a protein called apoptosis inhibitor five (API5), which signals the immune system to stop the attack. to the cells that line the intestine. This protein adds an extra layer of protection against immune damage, so even those with the mutation can have a healthy gut. However, the researchers also found that norovirus infection blocks the secretion of API5 T lymphocytes in mice bred to have a rodent form of Crohn’s disease, killing cells of the intestinal lining in the process.
Led by researchers at NYU Grossman School of Medicine, the work supports the theory that API5 protects most people with the mutation from the disease until a second trigger, such as norovirus infection, pushes some beyond the threshold of the disease. disease.
In experiments that focused on mice genetically engineered to have the Crohn’s disease-linked mutation in humans, the mice that received an API5 injection survived, while half of the untreated group died. This confirmed the idea that the protein protects intestinal cells, the study authors say. In human tissue, the researchers found that those with Crohn’s disease had between five and ten times fewer API5-producing T cells in their gut tissue than those without the disease.
“Our findings offer new insights into the key role that apoptosis inhibitor five plays in Crohn’s disease,” says study lead author and gastroenterologist Yu Matsuzawa-Ishimoto, MD, Ph.D. “This molecule can provide a new target for the treatment of this chronic autoimmune disease, which has proved difficult to manage in the long term ”.
Matsuzawa-Ishimoto, a postdoctoral researcher at NYU Langone Health, notes that current therapies, which work by suppressing the immune system, put patients at high risk of infection and often become less effective after a few years of use. An API5 targeted treatment method, she adds, could avoid these problems.
In another set of experiments, the researchers created organ-like structures from tissues collected from humans that tested positive for the mutation. In particular, these structures were made only of cells from the lining of the intestine. Then, the research team inserted API5 into these ‘mini guts’ and found that this treatment protected the cells of the gut lining. Furthermore, the addition of API5-producing T cells also protected the intestinal lining.
“The results of our investigation help explain why genetic links to Crohn’s are much wider than the actual number of people who have the disease,” says study co-author and biochemist Shohei Koide, Ph.D. Koide. Professor in NYU Langone’s Department of Biochemistry and Molecular Pharmacology and a member of its Perlmutter Cancer Center.
“Our study suggests that when norovirus infects those with a weakened ability to produce apoptosis inhibitor five, it tilts the balance towards full-blown autoimmune disease,” adds the study’s senior co-author and microbiologist Ken Cadwell. Ph.D., the Recanati Professor of Microbiology at NYU Langone.
Cadwell cautions that while the study authors derived the API5 protein from human tissue rather than rodents, it is unclear whether the injection treatment can be safely administered to humans. The research team therefore plans to explore the long-term effects of API5 injections to better understand whether the potential treatment can effectively manage Crohn’s disease, which can flare up repeatedly over a long period.
Norovirus infection can cause severe vomiting and diarrhea that begins suddenly. Noroviruses are highly contagious. They commonly spread through contaminated food or water during preparation or through contaminated surfaces. Noroviruses can also spread through close contact with a person who has a norovirus infection.
Diarrhea, stomach pain, and vomiting typically begin 12 to 48 hours after exposure. Symptoms of Norovirus infection usually last 1 to 3 days. Most people recover completely without treatment. However, for some people, particularly young children, the elderly, and people with other medical conditions, vomiting and diarrhea can be severely dehydrating and require medical attention.
Norovirus infection occurs more frequently in closed, crowded environments. Examples include hospitals, nursing homes, childcare centers, schools, and cruise ships. Signs and symptoms usually begin 12 to 48 hours after first exposure to a norovirus and last 1 to 3 days. You can continue shedding the virus in your stool for several weeks after recovery. This shedding can last for weeks or months if you have another medical condition.
Some people with norovirus infection may not show signs or symptoms. However, they are still contagious and can spread the virus to others.
Noroviruses are highly contagious. This means that norovirus infection can easily spread to others. The virus is lost in stool and vomit. You can spread the virus from the moment you have the first symptoms of the disease up to several days after healing. Noroviruses can stay on surfaces and objects for days or weeks.
You can get norovirus infection:
Eating contaminated food
Touch the mouth with the hand after the hand has been in contact with a contaminated surface or object
Be in close contact with a person who has a norovirus infection
Noroviruses are difficult to kill because they can withstand hot and cold temperatures and many disinfectants.
For most people, norovirus infection usually clears up within days and is not life-threatening. But in some people, especially young children; older adults; and people with weakened immune systems or other medical conditions or who are pregnant: norovirus infection can be serious. Norovirus infection can cause severe dehydration and even death.
Norovirus infection is highly contagious. There are many types of noroviruses. Anyone can get norovirus infection more than once.
To prevent norovirus infection:
Wash your hands thoroughly with soap and water for at least 20 seconds, especially after using the toilet or changing a diaper and before preparing food, food or drink. Alcohol-based hand sanitizers are not as effective against noroviruses as using soap and water.
Avoid contaminated food and water, including food that may have been prepared by someone who was sick.
Wash fruits and vegetables before eating.
Cook the seafood well.
Disinfect surfaces that may have been contaminated. Wear gloves and use a chlorine bleach solution or disinfectant effective against noroviruses.
Be careful when traveling. If you are traveling to areas with a high risk of norovirus infection, consider eating only cooked foods, drinking only hot or carbonated drinks, and avoiding food sold by street vendors
To help prevent the spread of norovirus infection, during illness and for 2 to 3 days after symptoms stop:
Avoid contact with others as much as possible.
Wash your hands thoroughly with soap and water.
Stay at home from work. Children should stay home from school or childcare.
Avoid handling food and objects that are to be used by other people. Disinfect contaminated surfaces with a disinfectant effective against noroviruses.
Carefully dispose of vomit and feces. Wear disposable gloves, soak up material with disposable towels. Disturb dirty material as little as possible to avoid the spread of noroviruses by air. Put dirty items in plastic bags and throw them in the trash. Remove and wash clothing and linens that may be contaminated.
Avoid traveling up to 2 or 3 days after the symptoms disappear.
Claudio Mastroianni, director of Infectious Diseases of the Policlinico Umberto I in Rome and president of Simit (Italian Society of Infectious and Tropical Diseases), explained how to distinguish the symptoms of intestinal flu from those of Sars-CoV-2 infection: ” The symptoms could be similar to Covid, in the vast majority of cases the clinical picture is quite distinct “.
, “Omicron affects the upper respiratory tract and in some cases causes intestinal disorders; in intestinal flu, on the other hand, there is fever, diarrhea and vomiting, without respiratory symptoms. In most cases, symptoms pass spontaneously within 48 hours. It is therefore good to wait a couple of days before checking if it is Covid. Furthermore, hydration is very important, essential for the very young and the elderly. If you have the sensation of vomiting, it is advisable to make them drink in small doses ”.
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