Human Intestinal Microbiome and the Immune System: The Role of Probiotics in Shaping an Immune System Unsusceptible to COVID-19 Infection

Today, the human gastrointestinal microbiota (HGM) is seen as an organ that orchestrates the activity of all other organs and systems (namely the brain) and one that plays a major role in maintaining homeostasis of the host organism. A remarkable ability of the HGM as a key player in the development of a normal immune system is its ability to recognize stress signals in its environment, e.g., triggers by viruses and other pathogenic microorganisms, and to react accordingly. SARS-CoV-2, the causative agent of COVID-19 disease, represents an unfamiliar type of virus to the human organism due to a lack of regular encounters between them over the course of evolution. This is one possible explanation of the disproportionate response of both innate and acquired immune systems seen in many people. In this review, we analyze certain immunomodulatory aspects of the HGM. We also assess the state of research in the field of next-generation probiotics, such as pharmacbiotics and postbiotics, and their potential use for the prevention and treatment of COVID-19. The range of symptoms typical of COVID-19 infection is presented in a concise form. The impact of COVID-19 infection on various organs and systems will be examined in future studies. Nevertheless, although we are in the early stages of the pandemic, we can still predict that COVID-19 will have a large impact of on the incidence of tuberculosis and depression in various populations around the world. The HGM, depending on whether it is normal or dysfunctional (dysbiosis), can be an important predictor of the efficacy of COVID-19 vaccines. These factors need to be taken into account, and, perhaps, a set of measures for the rehabilitation of certain groups of the population should be adopted. These measures should include the development of next-generation pharmacbiotics (psychobiotics, probiotics exhibiting antioxidant properties, immunobiotics), as well as specialized functional foods.