Measles: how it erases immune memory

01 November 2019

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After decades, researchers have discovered how measles erases our immune system’s memory of past infections...

A new study has uncovered how the measles virus erases our body’s “immune memory”. It happens because we lose immune system cells called memory B cells, meaning the body loses its memory of how to defend itself against diseases it has faced before.

In this state of ‘immunological amnesia’, for up to five years after recovering from measles, we are easy targets for every other disease and have limited ability to recover from them. While scientists have known about this for decades, it’s only now that they know how it happens in humans.

Velislava Petrova, one of the lead researchers, said her team discovered that “cells that were there before, that could generate this memory of other pathogens, were lost after measles.”

“In addition, after measles we have only a small amount of those available new immune cells that can respond to a new infection.” These cells are called naive cells, and by reducing the diversity of this type of cell, the measles virus impairs the ability to fight and learn about new pathogens.

The researchers at the Wellcome Sanger Institute in Cambridge, investigated the genes of immune cells in the blood of Dutch Orthodox Protestant children - before and after a measles infection.

They “built a genetic map of their immune cells before and after the infection,” Petrova said. “By reading through these genes we could build a map of each cell before and after measles, and we could track which cells were lost after the infection.”

The effect means that measles destroys the body’s defences gained through vaccinations received before the infection. The complications following a measles infection can be life-threatening, so this virus is nothing to mess about with.

Understanding the measles virus is increasingly important since it has re-emerged in many countries in concert with the “anti-vaxx” movement. In August this year, the UK lost its measles-free status - three years after the disease was originally eliminated from the country.

Petrova recommends “anyone who can get the vaccine that doesn’t have other medical conditions that prevent them from having it, should go and get the vaccine. It’s important to protect not only against measles, but against other diseases as well.”

“Measles is one of the most contagious viruses we know, and any infected person can infect up to 18 others - which means that even a small proportion of people are not vaccinated and get the disease can spread it to anyone else who is susceptible.”

The measles vaccine itself does not have the immuno-suppressive effects of a measles infection, because it is an attenuated live virus vaccine. This means that, although the vaccination does cause infection, it is in a weakened form incapable of causing clinical symptoms. Nevertheless, the body can use the experience to build immunity.

This study highlights the importance of widespread access to vaccinations. Velislava Petrova hopes that the scientific evidence provided by her study can eventually be used to “foster policy changes or strategic movements in order to improve access to vaccinations in these communities”.

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