Deadly measles infection destroys immune system in children leaving them vulnerable to host of other infections
1,250 individual cases of measles have been confirmed in 31 US states, from January 1 to October 3, 2019, according to CDC.
After a brush with measles, children become more vulnerable to other infectious diseases, finds a new study. The virus destroys the immune system: it wipes out antibodies that fight against infections, they explain.
For example, before contracting measles, a child may have developed 100 different antibodies to fight the chickenpox virus. A measles infection, says the research team, may reduce the number of these antibodies by half. These children show signs of low immunity for up to five years although they appear healthy, says the team from Princeton University, US; Emory University, Atlanta, US; Fogarty International Center, National Institutes of Health, US; and Erasmus University Medical Center, Netherlands, among others.
"Our study has huge implications for vaccination and public health as we show that not only does measles vaccination protect people from measles, but also protects from other infectious diseases," says Professor Colin Russell, senior author of the study from the University of Amsterdam, Netherlands.
According to the Centers for Disease Control and Prevention (CDC), 1,250 individual cases of measles have been confirmed in 31 US states, from January 1 to October 3, 2019. The measles virus causes coughing, rashes, and fever, and can lead to potentially fatal complications, which include pneumonia and encephalitis — inflammation of the brain.
"The threat measles poses to people is much greater than we previously imagined," says senior author Stephen Elledge, the Gregor Mendel Professor of Genetics and of Medicine in the Blavatnik Institute at Harvard Medical School and Brigham and Women's Hospital. He adds that the study demonstrates the need for measles vaccine to prevent damage to the immune system.
The declining rates of vaccination is cause for concern, say experts. According to experts, though vaccination has shown promises by saving an estimated 21.1 million lives between 2000 and 2017, measles has managed to bounce back. Reduced vaccination alone has led to a nearly 300% increase in measles infections since 2018 due to a combination of anti-vaccination campaigns, non-vaccinating religious communities, and limited access to the vaccine, says the study. Measles now leads to more than 100,000 deaths per year worldwide in unvaccinated communities.
The virus and the antibodies
To get a sense of the damage the virus unleashes on the immune system, the scientists relied on a technology that detects virus from a single drop of blood albeit indirectly — by hunting for antibodies against various viruses, including HIV and influenza. So, their first step was to check whether the technology worked against measles.
The team zeroed in on the Netherlands for the study, where they investigated how unvaccinated children in an orthodox Protestant community responded to measles. They collected blood samples before and 40-50 days after the measles infection.
When they compared the two samples, the scientists saw something unusual: they found a drop in the collection of antibodies that children had built up over the years. The virus was resetting the immune system to an immature child-like state, they explained.
The loss in antibodies was drastic in some children, the authors said. Depending on the severity, children lost 33% to 40% of their total antibody collection. These antibodies could have defended them against other infections.
"We were trying to figure out how VirScan [the virus detecting technology] worked with measles. And then we made this discovery. When measles hits, antibodies just go away," Elledge said.
To test the long-term effects of measles infection, the researchers repeated the experiment in four macaque monkeys but made one change: they delayed collecting blood samples by five months after infection.
As a result, they saw a dramatic drop in the antibodies. The monkeys lost, on average, 40 to 60% of the antibodies that protect them against infections.
Monkeys showed a more severe response because the scientists delayed collecting the blood samples. It takes time for antibodies to fade from the blood. His team may have seen similar numbers in the kids, had the team tested them again later, says Elledge.
The way forward, according to Elledge, is to vaccinate children. Children who skip the measles vaccine, known as MMR, and become infected with measles, may actually need to be revaccinated for previous diseases, he says.
The study has been published in Science.