Gut and airway microbiota dysbiosis and their role in COVID-19 and long-COVID

Front Immunol. 2023 Mar 8:14:1080043. doi: 10.3389/fimmu.2023.1080043. eCollection 2023.

Abstract

The gut microbiota plays a crucial role in human health and disease. Gut dysbiosis is known to be associated with increased susceptibility to respiratory diseases and modifications in the immune response and homeostasis of the lungs (the so-called gut-lung axis). Furthermore, recent studies have highlighted the possible role of dysbiosis in neurological disturbances, introducing the notion of the "gut-brain axis." During the last 2 years, several studies have described the presence of gut dysbiosis during coronavirus disease 2019 (COVID-19) and its relationship with disease severity, SARS-CoV-2 gastrointestinal replication, and immune inflammation. Moreover, the possible persistence of gut dysbiosis after disease resolution may be linked to long-COVID syndrome and particularly to its neurological manifestations. We reviewed recent evidence on the association between dysbiosis and COVID-19, investigating the possible epidemiologic confounding factors like age, location, sex, sample size, the severity of disease, comorbidities, therapy, and vaccination status on gut and airway microbial dysbiosis in selected studies on both COVID-19 and long-COVID. Moreover, we analyzed the confounding factors strictly related to microbiota, specifically diet investigation and previous use of antibiotics/probiotics, and the methodology used to study the microbiota (α- and β-diversity parameters and relative abundance tools). Of note, only a few studies focused on longitudinal analyses, especially for long-term observation in long-COVID. Lastly, there is a lack of knowledge regarding the role of microbiota transplantation and other therapeutic approaches and their possible impact on disease progression and severity. Preliminary data seem to suggest that gut and airway dysbiosis might play a role in COVID-19 and in long-COVID neurological symptoms. Indeed, the development and interpretation of these data could have important implications for future preventive and therapeutic strategies.

Keywords: COVID-19; SARS-CoV-2; dysbiosis; gut-brain-axis; gut-lung-axis; long Covid; microbiome; microbiota.

Publication types

  • Review
  • Research Support, Non-U.S. Gov't

MeSH terms

  • COVID-19*
  • Dysbiosis
  • Gastrointestinal Microbiome* / physiology
  • Humans
  • Post-Acute COVID-19 Syndrome
  • SARS-CoV-2

Grants and funding

This study was partially funded by the Italian Ministry of Health—Current Research IRCCS, the Fondazione Cariplo 2021-4236 LLC Network project, the Fondazione Bolton Hope Onlus “PREP-COVID” project, and the Associazione Nazionale per la Lotta contro l’AIDS (ANLAIDS). The funders were not involved in the study design, collection, analysis, interpretation of data, the writing of this article, or the decision to submit it for publication. All authors declare no other competing interests.