Measles virus wipes part of the immune system's memory

  • Measles virus wipes part of the immune system's memory

Measles virus wipes part of the immune system's memory

A pair of related studies published inScience andScience Immunology, however, busts the myth that measles isn't risky.

To what extent this "immune amnesia" increases illness and deaths from other infections isn't clear.

And with measles on the rise, "it should be a scary phenomenon", said Dr. Michael Mina of Harvard's school of public health, lead author of research published Thursday in the journal Science.

That's because measles virus attacks the cells that serve as the immune system's memory, wiping out established resistance to disease, a pair of new studies report.

'Whether measles infection causes long-term damage to immune memory has been unclear. They have never come into contact with a pathogen. "Even after the ferrets had been successfully vaccinated against flu, the measles-like virus reduced levels of flu antibodies resulting in the animals becoming susceptible to flu infection again and experiencing more severe flu-like symptoms".

"But the other side of the coin was that maybe actually the vaccine was unmasking a much worse immunological detriment or problem associated with measles", he says.

Previous epidemiological research into immune amnesia suggests that death rates attributed to measles could be even higher-accounting for as much as 50 percent of all childhood mortality-if researchers factored in deaths caused by infections resulting from measles' ravaging effects on immunity. Or, as Mina puts it, "measles seems to be punching holes in the immune memory". The average time between sample collections was 10 weeks. During a measles epidemic that hit the country in 2013, five of the children managed to avoid infection but most caught the virus.

When Kula examined an initial set of these samples, he found a striking drop in antibodies from other pathogens in the measles-infected children that "clearly suggested a direct effect on the immune system", the authors said. All children lost a large part of their so-called memory cells - the immune cells that the body created after an infection and that are ready to fight the same infection if it strikes again. At the point when the body gets another pathogen, B-cells assemble proteins that grasp the germ and hand it to another protein for decimation. Basically, the measles virus doesn't just delete immune memory-it makes it harder for the immune system to respond to new pathogens in the future. Instead of looking at how the antibody repertoire changed over time, the team looked instead at how the B cells themselves changed before and after infection.

In Science, Mina and colleagues used a tool called VirScan to analyze the responses of antibodies in the unvaccinated children before and after measles infection. Even the US, where most children are immunized, has seen a resurgence fueled by outbreaks in unvaccinated communities that in turn threaten people too young or sick to be immunized. Researchers found that measles virus destroyed between 11% and 73% of antibodies that people had built up against diseases to which they'd become immune.

Measles is one of the world's most contagious viruses, able to spread through coughs and sneezes for four days before someone develops the characteristic rash. An accompanying editorial in Science Immunology, written by Duane Wesemann, Harvard Medical School assistant professor of medicine at Brigham and Women's Hospital, contextualizes that study.

Previous studies have hinted that the disease's effects stretch long beyond the infection. The researchers found that all these kids either lived together or in the same neighborhoods, which expedited the pathogens' spread.

Much of the immune system's power comes from its flexibility. Although the relatively healthy Dutch children withstood these secondary infections, malnourished or immunocompromised children might not fare so well after measles, he added. "They went away very quickly", Elledge said.

In addition, the 20% of children most affected by measles lost over half of their pathogen-specific antibodies to most pathogens, and in some children, up to 70% antibody loss against specific pathogens was detected, the researchers noted.

"I think the main takeaway is that it underscores the importance of immunization", said Dempsey.

"If we slow or reverse public health gains when it comes to measles, this will have catastrophic consequences", he said.

Dr Charlie Weller, Head of Vaccines at Wellcome, said: "These findings further strengthen the vital role the MMR vaccine plays in public health and protecting us from deadly disease".

"Measles should not be underestimated", Schaffner said.