Gut Bacteria May Shield Against Severe Respiratory Infections

Select gut bacteria can protect against secondary bacterial pneumonia following a viral respiratory infection, such as influenza A, according to a modern study from Georgia State University. The research, published in Science Immunology, highlights the critical role of the gut microbiome in influencing the body’s immune response and potentially mitigating the severity of respiratory illnesses.

The Link Between Gut Health and Lung Immunity

The study focused on segmented filamentous bacteria (SFB), which are commonly found in the intestines of mammals. Researchers investigated whether the presence of SFB impacted susceptibility to secondary bacterial infections – often caused by Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus – after influenza A virus infection in mice. They discovered that SFB provided significant protection against these potentially lethal infections.

Much of the serious illness and death associated with influenza pandemics stems from these subsequent bacterial infections. This suggests that the composition of an individual’s gut microbiota could be a key factor in determining survival during a pandemic. Researchers at Georgia State University found that SFB’s protective effect relies on specialized immune cells called alveolar macrophages.

How SFB Protects the Lungs

Alveolar macrophages are crucial for defending the lungs against pathogens, but their function can be impaired following a viral infection like influenza. Interestingly, SFB, which resides in the intestine, can “epigenetically reprogram” these alveolar macrophages. This reprogramming helps the macrophages resist the dysfunction typically induced by the influenza virus, allowing them to maintain a robust defense against bacterial pathogens.

“The intestine is normally colonized by thousands of different bacterial species but yet, incredibly, adding one more completely changes the way that lung macrophages respond to pathogens,” says Vu Ngo, a research assistant professor in the Institute for Biomedical Sciences at Georgia State University.

Future Implications

The researchers are optimistic that understanding the mechanisms by which SFB reprograms alveolar macrophages could lead to new therapeutic strategies for preventing or mitigating the severity of a wide range of respiratory infections. Andrew T. Gewirtz of the Institute for Biomedical Sciences adds, “We’re very hopeful that we’ll soon be able to harness the mechanism by which SFB reprograms alveolar macrophages, yielding novel pharmacologic approaches to mitigate the severity of a broad assortment of respiratory infections.”

This research builds on existing knowledge of the gut-lung axis, which demonstrates the bidirectional communication between the gut microbiota and the respiratory system. Previous studies have shown that the gut microbial community can influence the body’s immune response to viral infections, including influenza.

The study was funded by the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health.