Cross-talk between immune system and microbiota in COVID-19

ABSTRACT

Introduction

Human gut microbiota plays a crucial role in providing protective responses against pathogens, particularly by regulating immune system homeostasis. There is a reciprocal interaction between the gut and lung microbiota, called the gut-lung axis (GLA). Any alteration in the gut microbiota or their metabolites can cause immune dysregulation, which can impair the antiviral activity of the immune system against respiratory viruses such as severe acute respiratory syndrome coronavirus (SARS-CoV) and SARS-CoV-2.

Areas covered

This narrative review mainly outlines emerging data on the mechanisms underlying the interactions between the immune system and intestinal microbial dysbiosis, which is caused by an imbalance in the levels of essential metabolites. The authors will also discuss the role of probiotics in restoring the balance of the gut microbiota and modulation of cytokine storm.

Expert opinion

Microbiota-derived signals regulate the immune system and protect different tissues during severe viral respiratory infections. The GLA’s equilibration could help manage the mortality and morbidity rates associated with SARS-CoV-2 infection.

KEYWORDS:

• Gut microbiota
• gut microbial-host-immune axis
• gut-lung axis
• coronavirus
• Covid-19
• respiratory complications

Article highlights

• Gut microbiota is essential for host immune system’s induction, education, function, development of immune responses, and regulates the integrity of the mucosal barrier, provides bacterial metabolites, and regulates the immunoregulatory functions of intestinal epithelial cells by modulating the expression of antimicrobial factors.

• Dysbiosis is linked to dysimmunity, commonly described as a T-helper 2 (Th2)-overactive, and Treg-deficient state.

• Cross-talk between the healthy gut microbiota and lungs can significantly prevent respiratory tract infection in both influenza A virus and COVID-19 through reciprocal interaction, quorum-sensing molecules, and synthesis of antimicrobial agents.

• In COVID-19 patients, probiotic treatment could result in an eight-fold lower rate of respiratory failure.

• It seems that fecal microbiota transplantation could be used as a therapeutic and rehabilitative intervention in the COVID-19 patients.

Declaration of interests

The authors have no other relevant affiliations or financial involvement with any organization or entity with a financial interest in or conflict with the subject matter or materials discussed in this manuscript apart from those disclosed.

Additional information

Funding

This paper was not funded.