Gut bacteria affect respiratory viral infection severity

Impact of gut microbiota on severity of respiratory viral infection revealed.

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According to research from Georgia State University, gut bacteria affect how mice catch and suffer from respiratory viruses. In Cell Host & Microbe, the study highlights the protective role of segmented filamentous bacteria against influenza in mice, whether acquired naturally or administered.

Segemented filamentous bacteria, linked to gut microbiota, protected mice from influenza and against RSV and SARS-CoV-2, the virus causing COVID-19. The study highlighted the crucial role of immune cells called basally resident alveolar macrophages in maintaining this protection. Researchers explored how distinct microbial species affect respiratory virus outcomes, studying mice with varying microbiomes and the presence or absence of segmented filamentous bacteria.

Dr. Andrew Gewirtz, co-senior author of the study and Regents’ Professor in the Institute for Biomedical Sciences at Georgia State said, “These findings uncover complex interactions that mechanistically link the intestinal microbiota with the functionality of basally resident alveolar macrophages and severity of respiratory virus infection.”

In mice lacking segmented filamentous bacteria, lung immune cells quickly depleted during respiratory virus infection. Yet, bacteria-colonized mice had altered immune cells resisting infection and inflammation. These alveolar macrophages, influenced by gut bacteria, effectively disabled the influenza virus by activating the complement system.

Dr. Richard Plemper, co-senior author, highlighted the remarkable impact of a single gut bacterial species in reprogramming immune cells, suggesting potential implications for assessing the risk of severe disease in human infections.

Gewirtz said, “We find it highly unlikely that segmented filamentous bacteria is the only gut microbe capable of impacting the phenotype of alveolar macrophages, and consequently, proneness to respiratory virus infection. Rather, we hypothesize that gut microbiota composition broadly influences proneness to respiratory virus infection. Microbiota mediated programming of basally resident alveolar macrophages may not only influence the severity of acute respiratory virus infection but may also be a long-term post-respiratory virus infection health determinant.”

This study shows how important gut bacteria are in determining how severe respiratory viruses can be. The study suggests that a single type of bacteria can change how immune cells work basally resident alveolar macrophages.

This finding could help assess the risk of severe respiratory diseases in people. Overall, the research gives us valuable insights into how gut bacteria and viruses interact, opening the door for more understanding and better management of respiratory illnesses.

Journal reference:

  1. Vu L. Ngo, Carolin M. Lieber et al., Intestinal microbiota programming of alveolar macrophages influences severity of respiratory viral infection. Cell Host & Microbe. DOI: 10.1016/j.chom.2024.01.002.

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