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Role of Probiotics in Respiratory Immune Response

- 6 min read
written by Shield Connect

Probiotics are live bacteria that, when given in sufficient proportions, have a favourable physiological effect on the host.

Probiotics
Probiotics are live bacteria that, when given in sufficient proportions, have a favourable physiological effect on the host. Owing to their health benefits in different aspect, some lactic acid bacteria found in fermented foods such as yoghurt, cheese, and pickles are generally accepted as healthy and classed as probiotics1.

Probiotics in immunomodulatory action
Probiotics have been found to provide a variety of immunological and physiological benefits. They are engaged in managing the bacterial environment and module immune cells, as well as enhancing the bioavailability of nutrients and maintaining reasonable health. In a healthy gut, dendritic cells (DC) play an important role in immunological homeostasis. DCs are important antigen-presenting cells that absorb antigens. In an immature DC, T cells can be deleted, or regulatory T cells can be stimulated. DC can be induced to prime these cells by the gut microbiome2. L. reuteri and L. casei, in fact, increase the production of IFN-gamma and activate pro-inflammatory Th1 cells. Monocytes are the first cells to come into touch with bacteria and viruses and are found in the peripheral circulation3.They differentiate into tissue macrophages, which interact with the gut microbiota or ingested probiotics to release a variety of cytokines. Herein, macrophages release the pro-inflammatory cytokine IL-12, which stimulates natural killer cells and CD4+ Th1 cells to secrete IFN-gamma, which is essential for virus eradication4.
Role of Probiotics in Respiratory Immune Response
Fig 1:Probiotics for immune homeostasis (Martens K et al., Allergy. 2018; 73:1954–1963)
NK cells play a critical role in the early immune response to viral infections, especially in the clearance of virus-infected cells. Lactobacillus probiotic strains stimulate DCs to secrete IL-12, which activates NK cells to secrete IFN-gamma, a key cytokine for bacterial (S. aureus) and viral elimination in the lungs 5.

Probiotics in respiratory tract infection
Vaccines, antibiotics, and antiviral drugs have long been used to prevent and cure bacterial and viral illnesses, but most infections remain uncontrolled. Because of their ineffectiveness against viruses and disruption of the normal human microbiome, antibiotics are not advised for treating viral infections. As a result, new techniques to the treatment and prevention of bacterial or viral respiratory tract infections have been developed and probiotics are one of them. In the past two decades, probiotics have been proposed as antimicrobial agents against viruses causing respiratory tract infections. Probiotics’ acts by modifying the innate immune system and amplification of acquired immunological responses1. Based on prior research of various viral illnesses, increasing and stimulating human immunological function by the intake of healthy, balanced diets and the use of dietary supplements like as vitamins, minerals, fibre, and probiotics can help avoid infectious diseases6.Oral probiotic strains have been used to prevent or treat influenza A, influenza H1N1, and respiratory syncytial viruses’ infection by reducing symptoms and viralload in the lungs or nasal passage thereby promoting immune activity and improving health. In a person who get colds more than four times a year, probiotic supplements comprising Lactobacillus paracasei, Lactobacillus casei, and Lactobacillus fermentum dramatically reduced the prevalence of influenza-like symptoms and upper respiratory infection. Intranasal administration using nasal sprays and aerosolized formulations, in addition to oral probiotic administration, is considered an effective and non-invasive approach for distributing probiotics into cells in the lungs to modulate the microbiota and treat or prevent a variety of viral infections 7. Several probiotic species have been administered intranasally or orally, including B. breve, L. pentosus, L. casei, L. plantarum, L. rhamnosus, L. gasseri, L. reuteri, L. lactis, and L. brevis etc. Further research study finds that intranasal administration of L.rhamnosus probiotics in mice infected with influenza H1N1 virus resulted insignificantly diminished symptoms and higher survival rates than observed in control mice.
Role of Probiotics in COVID-19 associated respiratory syndrome
The beneficial effect of probiotics on ACE enzymes, whether directly or indirectly, has been thoroughly documented. Probiotics create bioactive peptides that can inhibit ACE enzymes by inhibiting their active sites. Furthermore, the deceased probiotic cells’ detritus acted as ACE inhibitors8. These findings imply that probiotics could function as a blocker for the ACE receptor, which allows SARS-CoV-2 to infect lung and GI cells.

Conclusions
Probiotics are live microorganisms that confer health benefits when consumed in adequate amounts, including enhanced immune activity and the clearance of respiratory tract infections. It is evident that probiotics can reduce the incidence and severity of diseases, suggesting their promise for treating or preventingCOVID-19 disease as well apart from other respiratory infections. Probiotics could help prevent COVID-19 by maintaining the human GI or lung microbiota because dysbiosis plays a major role in the susceptibility of people to infectious diseases.

References:
1. FAO/WHO. Guidelines for the Evaluation of Probiotics in Food. https://www.who.int/foodsafety/fs_management/en/probiotic_guidelines.pdf (2002).
2. Foligne, B. et al. A key role of dendritic cells in probiotic functionality. PLoS ONE
2, e313, https://doi.org/10.1371/journal.pone.0000313 (2007).
3. De Roock, S. et al. Gut derived lactic acid bacteria induce strain specific CD4 + Tcell responses in human PBMC. Clin. Nutr. 30, 845–851 (2011).
4. Kitazawa, H. et al. Expression of mRNA encoding IFNα in macrophages stimulated with Lactobacillus gasseri. FEMS Microbiol. Lett. 120, 315–321 (1994).
5. Kudva, A. et al. Influenza A inhibits Th17-mediated host defense against bacterial pneumonia in mice. J. Immunol. 186, 1666–1674 (2011).
6. Khan, R., Petersen, F. C. & Shekhar, S. Commensal bacteria: an emerging player
in defense against respiratory pathogens. Front. Immunol. 10, 1–9 (2019).
7. Jung, Y. J. et al. Heat-killed Lactobacillus casei confers broad protection against influenza A virus primary infection and develops heterosubtypic immunityagainst future secondary infection. Sci. Rep. 7, 1–12 (2017).
8. Miremadi, F., Ayyash, M., Sherkat, F. & Stojanovska, L. Cholesterol reduction mechanisms and fatty acid composition of cellular membranes of probioticLactobacilli and Bifidobacteria. J. Funct. Foods 9, 295–305 (2014).

Pic Credit By Magazine – Revital

Prof. Dr. N. Sankaran Prof. Dr. N. Sankaran [MD., DNB, DTCD]
Sr Con Physician & Specialist in Respiratory Medicine
Ex- Indian Navy & JIPMER Pondicherry.
Ex-Professor of Thoracic Medicine in Tamilnadu Medical Service.
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