Killing gut bacteria with drugs weakens immune response
From the WashU Newsroom…
People infected with West Nile virus can show a wide range of disease. Some develop life-threatening brain infections. Others show no signs of infection at all. One reason for the different outcomes may lie in the community of microbes that populate their intestinal tracts.
A study from Washington University School of Medicine in St. Louis shows that mice are more susceptible to severe West Nile disease if they have recently taken antibiotics that change the makeup of their gut bacterial community.
“The immune system is activated differently if the gut does not have a healthy microbiome,” said senior author Michael S. Diamond, MD, PhD, the Herbert S. Gasser Professor of Medicine. “If someone is sick with a bacterial infection, they absolutely should take antibiotics. But it is important to remember that there may be collateral effects. You might be affecting your immune response to certain viral infections.”
The study is published March 27 in Cell Reports.
West Nile virus is not unusual in its ability to cause disease ranging from mild to severe. Many viral infections cause no symptoms in the majority of people, mild to moderate disease in some, and severe disease in an unlucky few.
But why people respond so differently to the same organism has never been entirely clear. Human genetics doesn’t explain everything, and neither does the genetic makeup of the microbe itself, although both play a role.
Diamond, first author Larissa Thackray, assistant professor of medicine, and colleagues from Washington University set out to determine whether antibiotic use could help explain why some people get very sick and others do not. Antibiotics kill off members of the normal bacterial community and allow some potentially harmful ones to overgrow. Since a healthy immune system depends on a healthy gut microbiome, they reasoned, antibiotics may be hobbling the immune system, leaving the body unprepared to fight off a subsequent viral infection.