Human study supports theory on why dengue can be worse the next time around
Amount of antibodies left over from first infection may boost chances of severe reaction the second time
Et tu, antibody? In humans, dengue can be more severe the second time around. Now, a study implicates an immune system treachery as the culprit.
The study suggests that the amount of anti-dengue antibodies a person has matters. In a 12-year study of Nicaraguan children, low levels of dengue antibodies left over in the blood from a prior infection increased the risk of getting a life-threatening form of the disease the next time around, researchers report online November 2 in Science.
Four related viruses cause dengue. The theory that antibodies protective against one type of dengue can collude with a different type of the virus to make a second infection worse was proposed in the 1960s. Such antibody-dependent enhancement has been shown in cells and lab animals. But “there’s been this controversy for five decades about, does this antibody-dependent enhancement really happen in dengue” in humans, says coauthor Eva Harris, a viral immunologist at the University of California, Berkeley’s School of Public Health. “And this says, yes, it does.”
About 2.5 billion people live where there is a risk of dengue infection. The virus infects 50 million to 100 million people every year, the World Health Organization estimates, but many cases go unreported. Infection with the mosquito-transmitted virus often leads to no symptoms, but can cause fever, joint and muscle pain and other flulike symptoms. The most severe form, which affects about half a million people annually, can include internal bleeding, respiratory distress or organ failure, and may be fatal.