Can probiotics help us treat viral respiratory diseases?

By now, we have probably all heard that there is a significant connection between our gut and our cognitive functioning. If you have ever experienced nausea or “butterflies in your stomach” during an anxious moment, you know this to be true. However, the connection might be more complicated than we previously thought. Recently, research groups have published more studies about how your gut microbiota might influence immunity, possibly even in the context of COVID-19. 

The vagus nerve innervates our visceral organs and controls or modulates such diverse processes as peristalsis, heart rate, sweating, speech, and more. However, we are starting to realize that the microbiota living in our digestive tract can communicate with our central nervous system to confer immunity. The mechanism by which probiotics could help immunity is by restoring balance in an imbalanced gut microbiome. According to one article I read, 70% of the immune system resides in the gut at the level of the intestinal epithelial barrier (Shahbazi et al. 2020). Other studies have found concrete evidence that mammalian gut microbiomes contribute to the development and maintenance of the immune system by enhancing the production of antibodies and IgA-producing B cells in the gut (Nishio and Honda 2012). 

Another aspect of our gut microbiota is that immune cells can travel from our intestines to our lungs because they share a common mucosal immune system (Shahbazi et al. 2020). This means that any potential imbalances in the intestines could cause issues in the lungs as well. One of the mechanisms that microbiota influence immunity to viral respiratory infection is because gut bacteria can regulate interferon signaling and inflammasome response which are essential for response to viral infection (Abt et al. 2012). Some research has shown that probiotics can reduce the incidence of viral respiratory infection through these mechanisms (Forsythe 2014). In the context of COVID-19, some researchers are wondering if probiotics may be an effective way to reduce negative gastrointestinal outcomes of the disease, and possibly help to boost the immune response to infection (Baud et al. 2020). Although we are not yet entirely sure if this is a plausible way to affect the pandemic, it is a fascinating connection between immunology and microbiology. 

Abt, M. C., Osborne, L. C., Monticelli, L. A., Doering, T. A., Alenghat, T., Sonnenberg, G. F., Paley, M. A., Antenus, M., Williams, K. L., Erikson, J., Wherry, E. J., & Artis, D. (2012). Commensal Bacteria Calibrate the Activation Threshold of Innate Antiviral Immunity. Immunity, 37(1), 158–170. https://doi.org/10.1016/j.immuni.2012.04.011 

Baud, D., Dimopoulou Agri, V., Gibson, G. R., Reid, G., & Giannoni, E. (2020). Using Probiotics to Flatten the Curve of Coronavirus Disease COVID-2019 Pandemic. Frontiers in Public Health, 8. https://doi.org/10.3389/fpubh.2020.00186 

Forsythe, P. (2014). Probiotics and lung immune responses. Annals of the American Thoracic Society, 11 Suppl 1, S33-37. https://doi.org/10.1513/AnnalsATS.201306-156MG 

Nishio, J., & Honda, K. (2012). Immunoregulation by the gut microbiota. Cellular and Molecular Life Sciences: CMLS, 69(21), 3635–3650. https://doi.org/10.1007/s00018-012-0993-6 

Shahbazi, R., Yasavoli-Sharahi, H., Alsadi, N., Ismail, N., & Matar, C. (2020). Probiotics in Treatment of Viral Respiratory Infections and Neuroinflammatory Disorders. Molecules, 25(21). https://doi.org/10.3390/molecules25214891