Prior exposure to virus linked to lower risk of birth defects

Natural immunity shields against congenital cytomegalovirus.

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Researchers at Tulane University have found that mothers have a lower chance of passing on a virus that can cause miscarriages and congenital disabilities if exposed to it before getting pregnant. This virus, called Cytomegalovirus (CMV), is a common herpesvirus that many women get without knowing it before they have children

Usually, it doesn’t cause problems, but during pregnancy, it can lead to miscarriages and severe congenital disabilities like cerebral palsy and hearing loss. This discovery brings us closer to developing a vaccine to protect mothers and their babies from CMV.

Researchers have known that women infected with CMV (Cytomegalovirus) for the first time during pregnancy face a higher risk of complications. However, they didn’t completely understand why women who already have the virus are less likely to have problems during pregnancy.

A study from Tulane University now explains that having pre-existing immunity to CMV helps limit its spread during pregnancy and prevents congenital disabilities. This research, published in PLOS Pathogens, identifies the specific immune mechanisms responsible for this protection.

To understand this better, researchers at the Tulane National Primate Research Center used a model with nonhuman primates, similar to human CMV infection. They found that when pregnant mothers got infected with CMV during the first trimester, they all passed the virus to their babies, leading to a high rate of miscarriages.

In contrast, something remarkable happened when nonhuman primates infected with CMV became infected again during their pregnancies. The mothers mounted a strong immune response upon reinfection. This time, only one out of every five mothers transmitted the virus to their babies through the placenta. Even more importantly, none of the infants suffered health problems due to this transmission.

 Dr. Amitinder Kaur, principal investigator and professor of microbiology and immunology, said, “Understanding how pre-existing immunity can protect against CMV transmission during pregnancy is crucial for developing an effective CMV vaccine that can safeguard all pregnant women and their unborn babies.” 

The results reveal that when a mother possesses immunity to CMV before pregnancy, her immune system can shield her baby from contracting congenital CMV, even if she experiences a reinfection during pregnancy. These findings hold great potential for developing a CMV vaccine to prevent infections in pregnant women, especially in regions where CMV is widespread.

This research offers hope for moms and babies by potentially lowering the chances of CMV-related birth issues and miscarriages, a big step forward in keeping mothers and babies healthy during pregnancy.

Journal reference:

  1. Matilda J. Moström, Shan Yu etal., Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection. PLOS Pathogens. DOI: 10.1371/journal.ppat.1011646.
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