Tests of gut tissue collected from people who died from coronavirus infection showed a strong effect of SARS-CoV-2 on the gut's immune system. The results of the study, authored by researchers at London's King's College, appeared in the journal Frontiers in Immunology.
Scientists examined samples of digestive tract tissues collected from people who died due to COVID-19 during the first wave of the pandemic.
The researchers explain that under normal conditions, the intestinal lymphoid tissue (GALT) is an essential element in maintaining the he alth of the body's immune system.
The so-called Peyer's patches - clusters of lymph nodes filled with immune cells that are located in the mucosa of the small intestine. Peyer's patches are responsible for maintaining the correct population of microorganisms living in the intestines, necessary for the proper functioning of the body. However, it has been observed that during the severe course of COVID-19, the Peyer's patch system is severely disrupted and this effect is unrelated to the detection - or not - of virus particles in the intestines.
The study authors recall that in severe COVID-19, the most common symptoms experienced are high fever and respiratory problems, but some patients may also experience gut symptoms, including diarrhea, nausea, and vomiting, suggesting that the virus attacked the digestive system.
“Our study shows that in severe COVID-19, a key component of the gut immune system, Peyer's patches, is disrupted. And this regardless of whether the intestine itself is affected by SARS-CoV-2 or not "- says the lead author of the work, Prof. Jo Spencer of King's College London. "This is probably what contributes to the imbalance in the gut microbial populations that sometimes occurs in COVID-19," he adds.
Observations of patient samples showed that the structure and cellular composition of Peyer's patches changed during COVID-19 - regardless of local virus levels. These changes mainly included a reduction in the number of multiplication centers that normally propagate antibody-producing cells.
According to the researchers, the resulting weak local immunity may in effectlead to dysbiosis, i.e. the depletion of the composition of the intestinal microbiota. This, in turn, can lead to ailments such as diarrhea, nausea and vomiting, abdominal pain, flatulence, loss of appetite and weight, as well as serious diseases: atopic dermatitis, irritable bowel syndrome, allergies, depression, inflammatory bowel disease, obesity and cancer.