Researchers at Georgia State University's Institute for Biomedical Sciences have found that certain gut bacteria can protect mice from deadly secondary bacterial pneumonia following influenza infection. The findings, published in Science Immunology, focus on segmented filamentous bacteria (SFB), which are present in the intestines of some mammals.
The study explored whether SFB influenced susceptibility to secondary infections by common respiratory pathogens such as Streptococcus pneumoniae, Haemophilus influenzae, or Staphylococcus aureus after initial infection with the influenza A virus. The results showed that SFB provided significant protection against these severe infections.
Much of the illness and death during influenza pandemics is due to secondary bacterial infections. The researchers suggest that differences in gut microbiota composition may play a key role in determining who survives such pandemics.
The protective effect of SFB was linked to alveolar macrophages, specialized immune cells in the lungs that often become dysfunctional after influenza infection. Although SFB is located only on the outer surface of the intestine, it was found to epigenetically reprogram these lung macrophages so they could resist dysfunction caused by the virus and maintain their defense against respiratory bacteria.
"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," said lead author Vu Ngo, research assistant professor at Georgia State's Institute for Biomedical Sciences.
"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," added senior author Andrew T. Gewirtz from the same institute.
Other contributors to this research include Carolin M. Lieber, Hirohito Abo, Michal Kuczma, Jun Zou and Richard K. Plemper. Funding for this study came from the National Institute of Allergy and Infectious Diseases (NIAID) at the National Institutes of Health (NIH).
