Malaria during pregnancy may alter babies’ risk of later infection

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Researchers from the Fred Hutchinson Cancer Research Center (WA, USA) and colleagues have discovered that mothers infected with malaria during pregnancy transfer more of their own cells to their offspring and can alter the infant’s risk of later infection.

The results from this study, recently published in the Journal of Infectious Diseases, suggest that maternal cells can have an impact on the child’s immune system, even after birth.

During pregnancy the placenta allows a unique exchange of cells between the mother and fetus referred to as “microchimerism”. This process usually allows the fetus to acquire a few maternal cells for every 100,000 cells of their own.

To understand how maternal microchimerism and malaria might interact, the team looked at 53 umbilical cord blood samples from pregnant women and their babies from a previous study in Tanzania, from 2002–2006. Approximately half of the samples had placental malaria, half of which was inflammatory placental malaria.

Results demonstrated that that babies born to mothers who had been infected with malaria during pregnancy had on average about 1% of maternal cells. Three of these babies had more than 5% maternal DNA in their blood. These results were surprising to the team.

“It’s really striking,” commented co lead author Whitney Harrington (University of Washington and Seattle Children’s Hospital; WA, USA), who went on to hypothesize that malaria infection caused changes in placental proteins that control cell trafficking and overall allowed more cells to enter the fetus.

The study then went on to demonstrate the lasting and potentially protective effect of these cells. The health records of these babies were studied and the team discovered that those with high levels of maternal microchimerism were twice as likely to be infected with malaria during childhood, but only half as likely to present with disease symptoms of infection.

Harrington explained two possible explanations for these results: “Either mom’s immune cells are directly recognizing and acting on the malaria parasite in her child’s body, or they’re acting indirectly by teaching the child’s immune system how to recognize and react to the pathogen.”

The team plan to conduct further studies to understand the interactions that occur between maternal and infant cells that may affect future malaria risk. In addition to this, they aim to determine how long these maternal cells persist during childhood and how levels of microchimerism may affect an individual’s susceptibility to other childhood infections.

Source: Harrington WE, Kanaan SB, Muehlenbachs A et alMaternal microchimerism predicts increased infection but decreased disease due to P. falciparum during early childhood. I Infect Dis). https://doi.org/10.1093/infdis/jix129 (2017); www.fredhutch.org/en/news/center-news/2017/05/malaria-during-pregnancy-can-alter-babies-immunity.html

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