Scientists have found out the mechanism of suppression of immunity by a coronavirus in the human body.
Molecular biologists from Germany have found that the coronavirus blocks the work of genes associated with the function of innate immunity and the production of interferons, antiviral protein molecules when entering intestinal cells, follows from an article in the bioRxiv electronic library.
“Our experiments indicate that the SARS-CoV-2 virus suppresses the immune response in immature enterocytes, the primary cells of the human intestine. That allows the virus to multiply in them and spread throughout the body. It also turns the digestive system into a reservoir of inflammation. We must study it for a full understanding of the pathogenesis of coronavirus infection,” reads the text of the study.
According to the current views of scientists, infection with the SARS-CoV-2 coronavirus leads to the development of severe disorders in the immune system. It also causes massive inflammation and microthrombus formation. Especially these and other problems threaten the patient’s life. Now scientists are trying to understand why they arise and how to prevent their development.
Megan Stanifer, a researcher at the University of Heidelberg (Germany), leads a group of molecular biologists. They uncovered the unexpected effect that coronavirus has on the human innate immune system and intestines, studying how its particles multiplied in a kind of “dummy” intestinal tissue, repeating the structure of the small intestine and ileum.
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First of all, scientists were interested in what types of intestinal cells SARS-CoV-2 infects. They also wanted to know what consequences the penetration of the virus into these bodies leads to. To do this, scientists isolated single cells from a human-made analogue of intestinal tissue. They also deciphered the structure of the RNA molecules contained in them, comparing these data with which chains of a similar kind were present in healthy cells.
Initially, biologists expected to find the dependence of the probability of infection and the number of affected cells should be on the level of activity of the ACE2 gene, which the coronavirus uses to penetrate the lung tissue. Unexpectedly, these expectations did not come true. The probability of infection and the number of infected intestinal cells did not depend in any way on how many ACE2 receptors were present on their surface.
Moreover, subsequent observations indicated that the penetration of the virus led to the opposite. That is, the activity of this gene decreased, the reasons for which are not yet clear. The penetration of the virus led to the shutdown of several genes associated with the reaction of cells to interferons. Those are complex protein molecules that are simultaneously capable of neutralizing viral particles. At the same time, they are activating immunity in already infected and still healthy cells.
A similar feature of SARS-CoV-2 allows this virus to multiply in the intestine for a very long time. It also allows it to penetrate other regions of the body. Moreover, it creates favourable conditions for its existence in the digestive system. Stanifer and her colleagues will continue observations of how the virus replicates in the intestines of animals. They hope it will help scientists understand how this process plays in the development of COVID-19.
Bacillus subtilis is a probiotic bacteria strain to support natural defences. It has immunostimulant properties, improving natural defences, fighting against infections and external aggressions and may boost immunity in older people and protect them from winter infections.