Researchers at Georgia State University's Institute for Biomedical Sciences have published a study indicating that specific gut bacteria protect mice from secondary bacterial pneumonia following influenza virus infection. The findings, published in Science Immunology, suggest that the composition of an individual's gut microbiota could influence survival rates during influenza pandemics, where secondary bacterial infections significantly contribute to morbidity and mortality.
Key Findings
The study focused on segmented filamentous bacteria (SFB), investigating its influence on susceptibility to secondary bacterial infections after influenza A virus infection in mice. The pathogens examined included Streptococcus pneumoniae, Haemophilus influenzae, and Staphylococcus aureus, which are common respiratory bacterial pathogens. SFB was found to demonstrate protection against these infections in the mouse models.
Mechanism of Protection
The protective effect of SFB against post-viral secondary bacterial pneumonia was mediated by alveolar macrophages. These specialized immune cells are known to become dysfunctional after influenza viral infection. Despite SFB residing exclusively on the outer surface of the intestine, it epigenetically reprogrammed these alveolar macrophages. This reprogramming enabled the macrophages to resist influenza virus-induced dysfunction, thereby maintaining their defense capabilities against respiratory bacterial pathogens.
Researcher Perspectives
Vu Ngo, a lead author and research assistant professor at the Institute for Biomedical Sciences, stated that the introduction of one bacterial species significantly altered how lung macrophages responded to pathogens. Senior author Andrew T. Gewirtz expressed that the mechanism by which SFB reprograms alveolar macrophages could potentially lead to new pharmacologic approaches for mitigating various respiratory infections.
Funding
The study received funding from the National Institute of Allergy and Infectious Diseases (NIAID) of the National Institutes of Health (NIH).