The immune response to influenza virus isn't 'all good'

Complications following infection with the virus that causes flu (influenza virus) are one of the top ten causes of death in the United States. Although infection with influenza virus can directly cause death, many deaths following infection with influenza virus occur because the individual develops pneumonia due to secondary infection with bacteria such as Streptococcus pneumoniae. How influenza makes individuals more sensitive to pneumonia-causing secondary bacterial infections is not well understood. However, Jane Deng and colleagues, at the University of California, Los Angeles, have now determined, through studies in mice, one mechanism by which influenza might sensitize individuals to secondary bacterial pneumonia. In the study, it was found that molecules known as type I IFNs, which are key mediators of the antiviral immune response initiated by infection with influenza virus, impaired the ability of mice to mount an adequate immune response to subsequent pneumonia-causing bacterial infection. In particular, the type I IFNs decreased production of soluble factors that attract neutrophils, immune cells central to the initial antibacterial immune response, to sites of bacterial infection. The authors therefore suggest that the pathway uncovered in their study might provide a new avenue of research for those developing ways to combat pneumonia following infection with influenza virus.

Source: Journal of Clinical Investigation