Measles Virus Can Cause Immune Amnesia and Increase Risk of Other Infections: Studies

Measles is one among the most contagious diseases and can be dangerous sometimes with fatal complications like pneumonia and brain inflammation. But measles is not just an annoying childhood disease. It can actually destroy the immune defense of the body for other kinds of infections, two new studies published in Science revealed.

There is a global increase in measles—by more than 30% during 2017-2018, main reason being under-vaccination or misguided vaccine safety concern. In US alone, this year witnessed largest measles outbreak since 1994 and 1,250 cases have been reported till October 3. Majority of these cases can be ascribed to the families choosing not to vaccinate the children.

The two detailed studies were done on blood samples collected from unvaccinated Dutch children that contracted measles and showed that infection can compromise the immune system for months or even years afterwards by erasing the immune memory the body developed to other pathogens in the past. Scientists name this as immune amnesia and to what extent it increases illness and deaths from other diseases is not clear. The results provide good reasons to immunise children against the virus, which the authors of the studies and other infectious disease experts believe. “If we allow [measles] outbreaks to happen, we are knowingly creating pockets of people who are susceptible to other diseases as well,” says Velislava Petrova at the Wellcome Sanger Institute in Hinxton, UK, lead scientist of one study.

The findings were based on population data showing that mortality from other pathogens increases after a measles outbreak. Both the teams chose a well known cohort of children belonging to an orthodox community of Netherlands whose parents chose to opt out of vaccination of their children. Blood samples were collected from 77 children before and after infection during a 2013 measles outbreak in the area. Before contracting measles, the children’s blood contained antibodies to many common pathogens. And after the disease, the children were found to have lost, on an average, 20% of their antibody repertoire. In some cases it was even worse—70% loss of their immunity to viral pathogens. The researchers found no such loss of immunity in their control—those who did not contract measles over the course of their study. Also, they found that there was no loss of antibodies in the children who received vaccination against measles.

The diminished antibody indicated that after a case of measles, unvaccinated children once again become vulnerable to viruses they had been exposed to in the past. For example, if a child had mumps prior to measles, then that child becomes susceptible to mumps again.

The measles virus is known to infect the B cells, the kind of cell of the immune system that creates an “immune memory” in the body after exposure to pathogens. Subsequent attacks by those pathogens would activate the memory and the immune system can easily destroy the pathogens. Measles infection was found to reduce the diversity of memory B cells, the virus kills off B cells specific to other pathogens and allows new measles specific memory B cells to replace them.

Measles also decreases the diversity of another type of B cells, the non-specific naïve B cells in the bone marrow. These cells stand ready to fight unfamiliar infections. A measles infection leaves this kind of cell immature similar to that of a fetus.

These findings show the importance of preventing measles and by means of the most effective way, that is vaccination.