Measles virus 'wipes out immunity to other infections'

Measles Wipes Your Immune System's Memory, Increasing Vulnerability To Other Dangerous Diseases

'They found that measles infection can greatly diminish previously acquired immune memory, potentially leaving individuals at risk for infection by other pathogens. The discoveries additionally fill in as an update that the current year's record-breaking measles flare-ups in the USA will have waiting impacts, Schaffner included. Researchers show that measles virus eliminates 11 to 73% of the different antibodies that protect against viral and bacterial strains that a person with a complete immune system, from influenza to herpes viruses and bacteria that cause pneumonia and infections of the skin.

Michael Mina, a Harvard virologist who also worked on the population study, teamed up with Elledge to analyze blood samples from 77 of the children before and after they became infected during a 2013 measles outbreak in the Netherlands.

None of the children in the study contracted measles case severe enough for them to be hospitalized.

"The threat measles poses to people is much greater than we previously imagined", says senior author Stephen Elledge.

Rewers said rebuilding immune memory is not easy; it could require getting re-vaccinated, or getting sick all over again.

Peter Hotez, MD, PhD, of Baylor College of Medicine in Houston, who was not involved with the research, noted a 2015 paper on this subject, which showed that measles has a prolonged effect on host resistance that can last 2-3 years, and even can drive an increase in non-measles deaths in children.

The worldwide team, which includes the Wellcome Sanger Institute, the University of Amsterdam and Imperial College London, revealed that the measles virus deletes part of the immune system's memory, removing previously existing immunity to other infections, in both humans and ferrets.

To see what measles does to the immune system, researchers looked at a group of unvaccinated people in the Netherlands.

Those antibodies are the blood proteins that "remember" past encounters with viruses and help the body avoid repeat infections.

The researchers confirmed that finding by infecting flu-vaccinated ferrets with a measles-like illness.

Some families choosing not to vaccinate argue that measles is just a pesky childhood illness to be endured. The researchers sequenced the genes of immune memory cells and found that after recovering from measles, the children's immune system had a different landscape of certain types of cells. "If you don't vaccinate your kid against measles, not only the kid may get infected - and it's not a pleasant or mild infection, it has a number of potential consequences in the brain and heart and other organs - but also the infection lowers the immunity to all of the previous viruses and bacteria that this kid has been exposed to".

But the rise of anti-vaccination campaigns, non-vaccinating religious communities and other factors have led to outbreaks causing tens of thousands infections in Congo, Madagascar, the Philippines, Sudan, Thailand and Ukraine, among other countries, according to WHO.

The study explains why children often catch other infectious diseases after measles and highlights the importance of vaccination against measles.

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

"Every time we see a pathogen, our immune system recognizes this pathogen, builds immunity to it and then stores it in the form of immune memory", explains Velislava Petrova, a postdoctoral fellow in immunogenetics at the Wellcome Sanger Institute in the United Kingdom and first author of the report published in Science Immunology.

For years there have been questions about why measles vaccinations decreased childhood deaths overall, with some people arguing that the vaccine might actually be boosting existing immunity to other pathogens, even though it is created to protect only against measles. The findings also serve as a reminder that this year's record-breaking measles outbreaks in the USA will have lingering effects, Schaffner added.

'Vaccination protects you against more than just measles, ' he said. "But we had a very hard time detecting measles", he says. "It's like taking somebody's immune system and rewinding time, putting them at a more naïve state", Mina says. The vaccine equips the body with an arsenal of anti-measles antibodies, just as the virus itself would, he said.

Examining the diversity of the antibody repertoire, the team found that measles infections were linked with a reduction of about 20% in the overall diversity of the antibody repertoire as measured by VirScan.

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