Bacterial infection before flu may protect against more severe complications
Studies have shown that individuals infected with the flu are likely to develop a more serious illness or even die if they develop a secondary infection after contracting the flu virus, Science Daily reports.
According to the researchers, however, if the order of infection is reversed, the Streptococcus pneumonia bacteria-or pneumococcs-could protect immune system cells in the lungs.
"Influenza remains a major killer, and there is a preponderance of evidence, both scientific and historical, to show how secondary bacterial infections can be fatal," Jan Erikson, a researcher and professor at The Wistar Institute, said, according to Science Daily. "However, pneumococci often colonize the respiratory tract asymptomatically, particularly in children, leading us to consider how pre-colonization would impact a subsequent influenza infection. Our studies showed that prior colonization offered a protective effect against severe disease in mice, and we were able to point to the bacterial virulence factor pneumolysin in mediating this protection."
Erikson and fellow researchers discovered that mice colonized by pneumococcus 10 days before exposure to the flu were less likely to develop severe illness or pneumonia than mice who were not colonized.
The researchers were able to isolate a single bacterial protein as the protective element. Though the exact mechanisms by which the protein, pneumolysin, reduces the severity of the disease are unknown, the researchers said they were able to demonstrate how macrophages were less likely to draw immune cells to the lungs, thereby reducing the chances of developing pneumonia, Science Daily reports.
"It remains to be seen what lessons we can learn from pneumococcus in lessening flu infections, but I would be interested in seeing if we could get the benefit of pneumococcal colonization without the associated risks," Erikson said, according to Science Daily.