Probiotics in Treatment of Viral Respiratory Infections and Neuroinflammatory Disorders

Abstract

Inflammation is a biological response to the activation of the immune system by various infectious or non-infectious agents, which may lead to tissue damage and various diseases. Gut commensal bacteria maintain a symbiotic relationship with the host and display a critical function in the homeostasis of the host immune system. Disturbance to the gut microbiota leads to immune dysfunction both locally and at distant sites, which causes inflammatory conditions not only in the intestine but also in the other organs such as lungs and brain, and may induce a disease state. Probiotics are well known to reinforce immunity and counteract inflammation by restoring symbiosis within the gut microbiota. As a result, probiotics protect against various diseases, including respiratory infections and neuroinflammatory disorders. A growing body of research supports the beneficial role of probiotics in lung and mental health through modulating the gut-lung and gut-brain axes. In the current paper, we discuss the potential role of probiotics in the treatment of viral respiratory infections, including the COVID-19 disease, as major public health crisis in 2020, and influenza virus infection, as well as treatment of neurological disorders like multiple sclerosis and other mental illnesses.

Keywords: COVID-19; gut microbiota; gut-brain axis; gut-lung axis; immunomodulation; influenza virus infection; multiple sclerosis; neuroinflammation; probiotics; viral respiratory infections.

Figure 1

Role of gut microbiota in the prevention of viral respiratory infections. Commensals-derived fragments and metabolites travel to the lung via systemic circulation and can act as signaling molecules and induce immune responses. Furthermore, activated immune cells travel to the lung via the lymphatic system. Besides, gut bacteria regulate the activation of STAT1 and IFNs signaling, which are involved in antiviral defense genes induction prior to infection and immune-mediated resistance to viral infection. INFs: interferons; STAT1: signal transducer and activator of transcription-1; LPS: Lipopolysaccharide; SCFAs: Short-chain fatty acids. Created with BioRender.com.

Figure 2

Role of gut microbiota in the prevention of neuroinflammation. Microbial products and metabolites can induce brain immunity indirectly by activating signaling pathways or directly through passing BBB. Gut microbiota regulates gut immunity hemostasis and modulates systemic immunity and brain immunity as well. Finally, gut commensal and their metabolites modulate microglia maturation and function, maintain BBB integrity, and prevent neuroinflammation. SCFAs: Short-chain fatty acids; Tregs; t regulatory cells; Th17: T-helper 17. Created with BioRender.com.