Elsevier

Virus Research

Volume 285, August 2020, 198018
Virus Research

Review
Gut microbiota and Covid-19- possible link and implications

https://doi.org/10.1016/j.virusres.2020.198018Get rights and content

Highlights

  • Covid-19 disease show gastrointestinal symptoms in some patients hinting at a role of gut-lung axis.

  • Gut microbiota diversity and its role in immunity highlighted.

  • Possible role of gut microbiota in Covid-19 discussed.

  • Implications of gut dysbiosis in Covid-19 analysed.

  • Role of diet in strengthening the gut microbiota and in the context of Covid-19 discussed.

  • Suggestions on therapy and prophylaxis based on gut microbiota in Covid-19.

Abstract

Covid-19 is a major pandemic facing the world today caused by SARS-CoV-2 which has implications on our understanding of infectious diseases. Although, SARS-Cov-2 primarily causes lung infection through binding of ACE2 receptors present on the alveolar epithelial cells, yet it was recently reported that SARS-CoV-2 RNA was found in the faeces of infected patients. Interestingly, the intestinal epithelial cells particularly the enterocytes of the small intestine also express ACE2 receptors. Role of the gut microbiota in influencing lung diseases has been well articulated. It is also known that respiratory virus infection causes perturbations in the gut microbiota. Diet, environmental factors and genetics play an important role in shaping gut microbiota which can influence immunity. Gut microbiota diversity is decreased in old age and Covid-19 has been mainly fatal in elderly patients which again points to the role the gut microbiota may play in this disease. Improving gut microbiota profile by personalized nutrition and supplementation known to improve immunity can be one of the prophylactic ways by which the impact of this disease can be minimized in old people and immune-compromised patients. More trials may be initiated to see the effect of co-supplementation of personalized functional food including prebiotics/probiotics along with current therapies.

Introduction

Coronavirus disease 2019 or Covid-19 is a new public health crisis threatening the humanity. Although, it originated in the Hubei province of China in late 2019 yet it has spread to many countries in the world (Wang et al., 2020). This pandemic disease is caused by the novel betacoronavirus, now named SARS-Cov-2(Lake, 2020). Covid-19 has very important clinical features such as high rates of transmission, mild to moderate clinical manifestation with more serious radiological abnormalities seen in the elderly (Yuen et al., 2020).

Coronaviruses are positive sense RNA viruses with spike like projections on its enveloped surface giving it a crown like appearance hence the term Coronavirus (Singhal, 2020). Phylogenetic diversity studies have highlighted that SARS-Cov-2 shares 79% nucleotide sequence identity with another virus of the same family SARS-Cov which caused major epidemic in 2002–2003 that resulted in 8000 cases in 26 countries (De Wit et al., 2016). Additionally, SARS-Cov-2 also displays sequence identities of 96% and 89.6%, for the envelope and nucleocapsid proteins respectively with SARS-Cov (Zhou et al., 2020b). Middle East respiratory syndrome or MERS disease in 2012 was also caused by another coronavirus called MERS-CoV. All these viruses utilize the ACE-2 receptor for their cellular entry (Zhou et al., 2020a). Interestingly, ACE-2 receptors are also reported to be expressed in the kidney and gastrointestinal tract, tissues known to harbour SARS-CoV (Harmer et al., 2002; Leung et al., 2003). Earlier evidence suggested that SARS coronavirus viral RNA was detectable in the respiratory secretions and stool of some patients after onset of illness for more than one month but live virus could not be cultured after third week (Chan et al., 2004). Now, recent report also suggests that SARS-Cov2 RNA can be detected in stool of some patients of Covid-19 (Wu et al., 2020). This along with the fact that some patients of this disease have diarrhoea points out towards a distinct possibility of involvement of gut-lung axis and may be the gut microbiota (Chan et al., 2020).

Section snippets

Gut microbiota and the gut-lung axis

The human gut microbiota consists of 1014 resident microorganisms which include bacteria, archae, viruses and fungi (Gill et al., 2006). Primarily, the gut bacteria in healthy individuals is dominated by four phyla Actinobacteria, Firmicutes, Proteobacteria, and Bacteroidetes (Villanueva-Millán et al., 2015). The colon harbours an extremely high density of bacteria in the families Bacteroidaceae, Prevotellaceae, Rikenellaceae, Lachnospiraceae and Ruminococcaceae (Hall et al., 2017). The gut

Nutrition and gut microbiota – strengthening the reservoir

Diet plays an important role in shaping the composition of the gut microbiota thereby influencing the host’s health status. Various diet forms are found to influence the specific compositional patterns of the gut microbiota like, for e.g., the different composition of the microbiota with animal fat and protein-based diets versus vegetable-based diets has been reported (De Filippis et al., 2016). It is interesting to note that the gut microbiota of animals fed with a high fat or high sugar diet

Conclusion and future perspective

Covid-19 has pushed the world to the brink. The faster we understand this disease the better we will be prepared the next time. Research in gut microbiota has propelled our knowledge in the field of chronic and infectious diseases. The presence of SARS Cov2 RNA in the stool of some patients and diarrhoea in few suggest a subtle link between the lung and the intestine. Although, no faecal-oral transmission is reported, yet it can be assumed that many asymptomatic children and adults may shed

Declaration of Competing Interest

Debojyoti Dhar is the Director of Leucine Rich Bio Pvt Ltd.; There is no financial disclosure

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

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