Measles Erases Immune System’s Memory, Study Finds
Scientists say measles selectively and exclusively infects humans. Why isn’t known.
Now it turns out that the measles virus erases much of the immune system’s memory of prior infections. Scientists have dubbed the startling findings “immune amnesia.”
Any immunity you build up from childhood illnesses is wiped out because measles suppresses the immune system, according to scientists here at the Wellcome Sanger Institute, and they say this can last for several years.
Today their conclusions are published in Science Immunology.
The results of a separate study, also out today, from Harvard University in America are published in the journal Science.
The Harvard team analyzed blood samples taken from 77 children before and after a measles outbreak in an unvaccinated community in the Netherlands.
They looked for antibodies, which remember viruses and bacteria they encounter and guard against a repeat infection.
After recovering from measles, the youngsters were left with measles antibodies, but any protection against other bugs had plummeted.
The scientists for the Wellcome Sanger specialise in genetics.
They used the Dutch blood samples to genetically test antibody-producing cells, and concluded measles is eliminating them to re-set the immune system to a baby-like state.
The Sanger’s lead author Velislava Petrova explains how they began the process by separating out the white blood or B-cells:
“We separated the B cells from different individuals and now we are putting here their genome to try to separate the DNA from the RNA. So the RNA is where the products of the different antibody genes were generated and we would want to read them in order to understand what is the code that they have and to try to track them before and after infection.”
The RNA stores genetic information, like the antibodies a person has built up to fight viral and bacterial illnesses.
Petrova says: “For the first time we could use a technique that allows us to read the genes that the immune system uses to produce antibodies and be able to track specific immune cells before and after infection. In order to find out what happens to them after measles.”
The result she says was worse than expected, the effects were longer term:
“After measles, up to five years people are, have increased rate of other infections with other pathogens, which shows that there is an effect that we can observe from a population level. But whether every single one of us would be affected in exactly the same way. It really depends on how, what’s the status of our immune system when we get infected,” says Petrova.
Dr. Chris Smith is a consultant virologist at University of Cambridge and Addenbrookes Hospital as well as presenting a radio programme which aims to bring a better understanding of new science to people.
He says: “These two studies answer a question that’s been foremost in scientists minds for a really long time which is why is it that when you catch measles, afterwards there appears to be what some dub an immune amnesia. For a period of perhaps five years after infection, individuals who catch measles, not have the vaccine, but catch natural measles develop this state where they’re much more susceptible to infection and they even seem to be able to catch things that they’d previously become immune to.”
Unproven fears about the combined MMR vaccine in the 1990s led to fewer vaccinations across Europe and America.
This in turn has lowered the resistance many populations previously had to the virus.
Earlier this year the US Centers for Disease Control announced measles infections were at a 25 year high and in Europe cases tripled.
Before a vaccine was developed in 1963, measles caused between three and four million cases each year in America alone.
Now scientists hope people will begin to understand measles is not to be underestimated and seek vaccination for their children.
Petrova explains how the vaccine works: “For vaccines like the vaccine against measles we have live attenuated virus, which means that we present to the immune system an entire, various components of a virus, but the virus can not infect cells. So we just give it a sample of what a virus would look like without this virus being able to infect us. So in this case, we can build immune memory, but we don’t cause immune suppression because the virus does not infect cells, does not kill cells.”
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