Scientists have found that gut bacteria help to fight the flu

© Illustration RIA Novosti . A. Planinata the artist imagines the effects of gut bacteria on the immune system, prevent development of the fluScientists have found that gut bacteria help to fight the flu© Illustration RIA Novosti . A. Polyanina

An international group of scientists from ITMO University, higher education institution participating in the Project of increase of competitiveness of leading Russian universities among leading research and educational centers (Project 5-100) and Washington University in St. Louis demonstrated experimentally that intestinal microbiota influences the formation of the immune response of the organism during infection with influenza virus. Metabolites, which are formed as a result of the activities of intestinal bacteria stimulates the production of interferon, a protein that inhibits the replication of the virus. The results were published in the prestigious scientific journal Science.

Different people respond differently to infection with influenza virus. Previously it was thought that the immune response depends on genetic factors, environmental conditions of residence of the person that influence, in turn, chemical reactions and processes inside the body. However, a study by the international group of scientists from USA and Russia showed that the waste products of bacteria that live in human intestines, also play a role.

The researchers showed that microbiota not only affects the function and health of the digestive system, but also on the immune response in acute infectious disease, damaging the respiratory system. In particular, metabolite desamination (desaminotyrosine – DAT) promotes the production of interferon, a protein that prevents the replication of the virus. Thanks to him, in the infected cell are triggered chemical reactions that are able to stop protein synthesis in General. In addition, interferon activates the processes for the development of viral antigens and other compounds involved in the immune response.

In order to prove the role of microbiota and regulation mechanisms of the immune response to flu through the production of interferon, the researchers conducted a series of experiments on mice. It was known that sterile mice without a microbiota faster and in greater numbers die from the flu. To find out which bacteria help protect against the virus, researchers tested 86 metabolites – products of the bacteria on the ability to stimulate cells for interferon production. The result was found 11 such metabolites, and the most biologically relevant was DAT a degradation product of plant substances flavonoids. Scientists have also identified the types of bacteria responsible for the production of the metabolite.

«For the verification of the results was taken as a conventional mouse and sterile mouse and the mouse is incapable of the production of interferon — says one of the authors of the article, a student of the ITMO University Catherine Esaulova. Had metabolite of drinking water for 7 days prior to infection and 14 days for illness. In accordance with previous results, the sterile mice showed greater mortality compared with normal mice. In both types of mice death from the virus and weight loss was significantly less in mice receiving DAT. In accordance with our hypothesis that the DAT protects against flu virus through increased production of interferon — DAT had no effect in mice, unable to develop it».

Experiments have shown that to benefit from the effect of DAT in the fight against the virus needs to a metabolite already present in the body in sufficient quantity at the beginning of the disease. So, mice that were administered the DAT two days after getting the flu, cope with the disease worse than mice that did not receive or received before infection. Thus, the increase in the number of metabolites during the infection affects the course of the disease. To the metabolite affected the immune system, it is necessary that it was already present in the body at the beginning of a viral infection.

«According to preliminary data, DAT not involved in the induction and amplification of interferon. Also according to preliminary data, in the presence of a pathogen in the body, DAT is involved in strengthening the immune response against the pathogen. The discovery that the colony already present in human microbiota help protect the body from flu, may play a role in the understanding of the heterogeneous response to infection among men. The results indicate that prior colonization of specific bacteria, and a flavonoid-rich diet can be a key component in regulation of the immune response to infection,» said another author, research fellow, Department of pathology and immunology of the University of George. Washington’s Maxim Artyomov.