The measles virus is highly contagious and can lead to life-threatening complications like pneumonia or swelling of the brain. Now, two papers published in Science and Science Immunology on 31 October report that the dangerous measles virus can compromise the immune system — for months, if not years, post-infection — by erasing its ‘memory’. Thus, highlighting the importance of the measles vaccination.
After an infection or vaccination, immune cells create a ‘memory’ of the pathogen and develop specialised antibodies that can be called upon quickly to fight off any future attack. Previous studies have suggested the so-called ‘immunosuppressive effects’ of the measles virus, which can cause the immune system to ‘forget’. But the latest papers are the first to provide concrete evidence that the virus does indeed destroy the memory of the immune system.
In the Science study, researchers analysed blood samples from 77 unvaccinated children in the Netherlands collected before and after a measles outbreak in 2013. All the children were healthy before the infection but the scientists found that the virus had erased 11–73 per cent of the children’s antibodies against other bacteria and viruses. Another 33 children who did receive the measle’s vaccination were also tested but in the uninfected group, the researchers found no decrease in their antibodies.
To collect further evidence, they also infected monkeys with the measles virus and found that similarly, the macaques lost 40–60 per cent of their antibodies against other previously encountered pathogens.
In another independent published in Science Immunology, the scientists analysed blood samples from the same group of unvaccinated children. This time, they discovered that immune cells (B cells) that held memories of other previously-encountered pathogens were destroyed and replaced with measles-specific B cells. And they also observed less diverse populations of nonspecific naïve B cells that fight unfamiliar infections, making it more difficult for the immune system to respond to new infections in the future.
The new findings come at a time when the number of measles cases has recently escalated. Incidence of the disease increased by more than 30 per cent globally from 2017 to 2018, with a large number of cases reported in China and the Congo. And during the first 6 months of 2019, there were more measles cases than in any other year since 2016, according to the world health organization (WHO).
Despite aggressive vaccination campaigns, measles is proving difficult to fully eradicate due to poor immunisation rates and a lack of infrastructure in some countries. For example, measles vaccinations remain high in sub-Saharan Africa. However, the findings highlight the importance of the MMR vaccination, and not just against measles, but other common infections.
Clearly, more effective vaccination policies are needed – children are only contracting the measles virus because they are not vaccinated. And clinicians could also consider administering boosters of other vaccinations they may have previously received after a measles infection, says co-author of the Science paper and immunology researcher at Harvard Dr Michael Mina, which could help prevent life-threatening diseases later in life as a result of the measles.
(1) Petrova, V.N. et al. Incomplete genetic reconstitution of B cell pools contributes to prolonged immunosuppression after measles. Science Immunology (2019). DOI: 10.1126/sciimmunol.aay6125
(2) Mina, M.J. et al. Measles virus infection diminishes preexisting antibodies that offer protection from other pathogens. Science (2019). DOI: 10.1126/science.aay6485