An article revealed in Critical Reviews in Food Science and Nutrition journal gives an summary of the function of intestine microbiota in shaping the host immune response to extreme acute respiratory syndrome coronavirus 2 (SARS-CoV-2).
Study: Gut microbiome and anti-viral immunity in COVID-19. Image Credit: Design_Cells / Shutterstock
Background
SARS-CoV-2, the causative pathogen of the coronavirus illness 2019 (COVID-19) pandemic, is an RNA virus that primarily impacts the higher and decrease respiratory tract. The virus can also be recognized to probably goal the gastrointestinal (GI) tract and impair the composition and variety of intestine microbiota.
The intestine microbiota is a set of microbes that naturally reside within the GI tract. The GI tract accommodates trillions of microbes that work together with each other to control varied physiological processes, together with the immune system. Alteration in intestine microbiota composition and variety known as dysbiosis, which impairs immune response and irritation.
Gut microbiota and COVID-19
GI signs, together with nausea, vomiting, and diarrhea, have been noticed in 60% of COVID-19 sufferers. An impaired intestine microbiota has been noticed in COVID-19 sufferers, regardless of the presence of GI signs. Importantly, it has been noticed that dysbiosis persists for as much as 6 months after the scientific clearance of SARS-CoV-2 from the respiratory tract.
Gut microbiota alterations generally noticed in COVID-19 sufferers embody diminished commensal bacterial populations with immunomodulatory features that assist keep the integrity of GI barrier and immune homeostasis.
A big proportion of COVID-19 sufferers develop long-term signs, which is medically termed as long-COVID. Studies have proven that individuals with long-COVID have diminished commensal bacterial inhabitants and altered total intestine microbiota. In addition, the diminished bacterial inhabitants correlates with elevated serum focus of proinflammatory mediators in these sufferers.
A discount in commensal bacterial inhabitants is accompanied by enrichment of pathogenic bacterial inhabitants and discount of intestine microbiota range. Studies have prompt that these adjustments in intestine microbiota composition and variety is likely to be related to elevated intestine permeability, microbial translocation, hyperinflammation, and poor COVID-19 prognosis.
Besides bacterial inhabitants, SARS-CoV-2 an infection is understood to change the intestine fungal inhabitants. An enrichment in opportunistic fungal pathogens has been noticed in COVID-19 sufferers. Pathogens resembling these are related to pneumonia and respiratory signs and have an effect on the meeting of intestine micro organism.
Gut microbiome and SARS-CoV-2 host cell entry
The spike glycoprotein of SARS-CoV-2 interacts with host cell membrane receptor angiotensin-converting enzyme 2 (ACE2) to provoke the viral entry course of. Besides respiratory epithelial cells, ACE2 is expressed at a excessive degree within the abdomen, ileum, and colon, highlighting the potential of direct viral entry into the GI tract.
The abundance of sure bacterial species that downregulate ACE2 expression are recognized to correlate negatively with COVID-19 severity. Patients with diabetes or weight problems exhibit a low abundance of those micro organism and are on the highest danger of COVID-19-related mortality.
Gut microbiome and immune response to SARS-CoV-2 an infection
The intestine microbiota is understood to stimulate host antiviral immune response by modulating kind 1 interferon signaling. In extreme COVID-19 sufferers, an impaired interferon response and a suppressed adaptive immune response are recognized to trigger lung injury. SARS-CoV-2-induced alteration in intestine microbiota is likely to be related to these pathologies.
Inflammasome, a cytosolic multiprotein advanced, is understood to affiliate with COVID-19 pathogenesis. Recent proof has prompt that inflammasomes induce the discharge of neutrophil extracellular traps by neutrophils in extreme COVID-19 sufferers, which in flip is related to impaired lung perform.
An altered intestine microbiota would possibly contribute to COVID-19 pathogenesis by triggering inflammasome activation. For instance, in COVID-19 sufferers with cardiac issues, elevated activation of inflammasomes and elevated markers of a leaky intestine, resembling lipopolysaccharide-binding protein, have been noticed.
The intestine microbiota is important for the regulation of the adaptive immune system. For instance, in response to viral an infection, the intestine microbiota induces activation of B cells and T cells, thus taking part in antibody manufacturing and virus-specific reminiscence immune cell manufacturing.
The administration of particular commensal micro organism has been discovered to extend neutralizing antibody ranges within the blood in response to viral vaccination. Similar results have been noticed in COVID-19 sufferers.
Gut–lung immune axis
The intestine microbiota performs a vital function in regulating lung well being. Immune cells are migrated from the intestine to the respiratory tract to destroy invading pathogens. This known as the intestine–lung immune axis.
Alteration in intestine microbiota composition will increase the danger of respiratory illnesses, resembling bronchial asthma. In COVID-19 sufferers, opportunistic higher respiratory tract micro organism have been recognized within the intestine microbiota. Similarly, an imbalance in lung microbiota has been noticed in COVID-19 sufferers with dysbiosis. These observations spotlight the prevalence of bidirectional translocation of microbes between the intestine and lung.
Modulation of intestine microbiota as a therapeutic intervention for COVID-19
Given the numerous affiliation between dysbiosis and anti-SARS-CoV-2 immune response, modulation of intestine microbiota has been thought of a possible therapeutic intervention for COVID-19.
Transplantation of fecal microbiota, which represents the entire intestine microbiota, from a wholesome donor into the GI tract of a recipient is taken into account a possible technique to deal with bacterial an infection. This technique is at the moment underneath scientific investigation in COVID-19 sufferers.
Dietary prebiotics are non-digestible fibers used to extend the proportion of commensal micro organism and cut back the proportion of pathogenic micro organism. There is proof suggesting the well being advantages of prebiotics in COVID-19 sufferers.
Probiotics are reside organisms with immunomodulatory results. In addition, peptides produced by probiotics have proven ACE2 inhibitory results. Thus, probiotics are thought of a possible adjuvant technique in treating COVID-19 sufferers.