Measles virus infection erases the body's immune memory - The360 Healthy

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  • Thursday, November 28, 2019

    Measles virus infection erases the body's immune memory

    Measles virus infection erases the body's immune memory

    New studies have shown that in addition to its direct danger to the patient, the measles virus is able to weaken the body's immune memory, making people vulnerable to infections they were previously immune to. For researchers, the virus is therefore much more harmful than estimated, which means that an adequate vaccination rate is even more important.

    Measles is a highly contagious viral disease that mostly affects children. The virus spreads when patients cough or sneeze, or through direct contact with nasal or laryngeal secretions. The first symptoms, which usually appear 8 to 12 days after exposure to the virus, are high fever, runny nose, red eyes and small whitish spots inside the mouth. A rash appears several days later, usually on the face and upper neck and gradually extends down the body. There is no specific treatment and most people get better in two to three weeks.

    However, the World Health Organization states that measles can lead to serious complications such as blindness, encephalitis, severe diarrhea, ear infection or pneumonia, especially in malnourished and immunocompromised children. Two studies published by researchers at Harvard, Howard Hugues Medical Institute and Erasmus University in the Netherlands show that the disease is even more dangerous than scientists thought, and how useful the vaccine is . Studies show that measles damages the immune system in the long-term, making people vulnerable to other infections.

    Immune amnesia

    Specifically, researchers have revealed that the measles virus clears some of the body's immune system memory, thereby suppressing existing immunity against other infections. The scientific team has shown for the first time that measles "resets" the human immune system to the point of reducing it to a state similar to that of an immature baby, that is to say with a limited ability to respond to new infections. According to her, this discovery explains why children often succumb to other infectious diseases after having measles and stresses the importance of getting vaccinated against this disease.

    According to one of the studies published in Science Immunology, this phenomenon is not without consequences in terms of public health because measles cases are increasing globally because of insufficient vaccination coverage. This could lead to an increase in other dangerous infections such as influenza, diphtheria or tuberculosis. In 2018, nearly 350,000 cases of measles were reported worldwide, more than twice as many as in 2017, according to WHO, which warns of gaps in coverage, sometimes anchored for many years and considers that the vaccination rate needed to prevent outbreaks should be 95%.

    The MMR vaccine: simple and effective

    To reach this conclusion, the researchers performed a blood test of 77 unvaccinated children before and after a measles outbreak. The results revealed that two months after infection, the virus eliminated between 11 and 73% of their different antibodies, the proteins in the blood that "remember" encounters with viruses and help the body avoid infections. recurring. Children in fact lose a large part of their immune defenses and become vulnerable to the viruses they have already encountered and conquered. Thus, if a person had 100 antibodies against chickenpox before contracting measles, it could only have half of it afterwards.

    In addition, in measles-infected macaques, 60% of the antibody repertoire was undetectable for at least five months. Although the reconstitution of the antibody repertoire is possible thanks to new exposures to pathogens, as for infants, the patient must wait several months or even years, which can represent a risk to health. A dangerous phenomenon that researchers have dubbed "global immune amnesia". "Our study shows not only that measles immunization protects against measles, but also other infectious diseases. Says Prof. Colin Russell of the University of Amsterdam.

    As measles cases are strongly resurgent in recent years, particularly in France, we must ensure that its measles-mumps-rubella (MMR) vaccination is updated for anyone born after 1980. With two injections (the first to 12 months and the second between 16 and 18 months, with a period of one month between the two injections), the child is protected against measles, mumps and rubella. Note that measles can occur at any age, in unvaccinated people: the disease is not only related to childhood. The health insurance specifies that in the over 15 years, in one out of two cases of measles, hospitalization is necessary.

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