Getting measles 'resets' the body's immune system

Chalkboard eraser

HealthHow measles infections can wipe away immunity to other diseases By Helen Branswell @HelenBranswell

Once infected, the amnesic immune system no longer recognizes the harmful pathogens that it has fought off in the past.

For people vaccinated decades ago, the amount of measles antibodies in the blood might be too low for VirScan to spot.

These new studies "underscore the clear and present danger the re-emergence of measles around the world represents and the incalculable value of the measles vaccine", Adalja added. Using data from a group of unvaccinated children in the Netherlands, both studies revealed what scientists have long suspected: that the measles virus cripples the immune system in a profound and lasting way. "This shows that measles could reverse the effects of vaccination against other infectious diseases". The findings also serve as a reminder that this year's record-breaking measles outbreaks in the USA will have lingering effects, Schaffner added.

Measles infections eliminate the immune system's memory of infectious diseases, resetting the human immune system to a baby-like state and increasing vulnerability to other unsafe infectious diseases like diphtheria, tuberculosis, and the flu, according to two new studies published today.

However, lack of access to vaccination and refusal to get vaccinated means measles still infects more than 7 million people and kills more than 100,000 each year worldwide, reports the WHO-and cases are on the rise, tripling in early 2019.

The results of a separate study, also out today, from Harvard University in America are published in the journal Science.

This gave nearly two-thirds of the participants the immune system of a young baby which has never encountered pneumonia bacteria or other risky bugs, so has no protection.

In fact, before the measles vaccine was introduced in the 1960s, an estimated 50% of childhood deaths may have been associated with infections that kids caught after surviving a bout of measles, according to a 2015 study published in Science. After recovering from measles, the youngsters were left with plenty of antibodies against that virus - but ones they'd previously harbored against other germs had plummeted.

'When people get an infection, their immune system creates antibodies to fight it off'. Researchers took blood samples from 26 unvaccinated children in a Dutch Orthodox Protestant community in the Netherlands before and after those children contracted measles; it analyzed the children's cells before and having had the disease. But no one had rigorously tested the idea, Elledge says.

Rather than taking stock of B-cells, authors of the Science study went straight to the front lines of immune defense: the antibodies themselves. They can directly destroy invaders by glomming on in huge numbers, but they also attract other immune cells to the pathogen, spurring an even larger response. "But would they have gotten it if they hadn't gotten measles?"

But the measles virus erased much of that history.

However researchers have now discovered measles "resets" the immune system, wiping out the immunity children have developed to other illnesses, effectively leaving them with the same scant protection they had as newborns. "But kids on the edge-such as those with severe measles infection or immune deficiencies or those who are malnourished-will be in serious trouble".

'This finding emphasizes how the MMR vaccine protects against more than just measles, ' says Velislava Petrova, an immunologist at the Wellcome Sanger Institute in Hinxton, UK, who led the Science Immunology study.

The study "quite convincingly showed that this immune damage is likely the actual antibodies disappearing", Wesemann told Live Science. "And that generates a situation which is 'immune amnesia'". "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". The researchers found that all these kids either lived together or in the same neighborhoods, which expedited the pathogens' spread. "Ultimately, the conclusions that can be drawn are very similar: Infection really skews the naive repertoire, and you could expect that that would have long-term, downstream consequences on immune memory", Mina says.

The researchers say their studies show how crucial it is to be vaccinated for the measles as a child because the vaccine gives the body a ton of antibodies against the measles, without harming the antibodies used to protect the body against other illnesses.

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