New study shows pre-existing immunity protects against CMV transmission during pregnancy

Researchers at Tulane University have achieved a groundbreaking milestone by demonstrating that mothers have a significantly lower likelihood of transmitting a common virus responsible for miscarriages and birth defects if they are exposed to the virus prior to conception. This study represents a substantial advancement towards the development of a vaccine that could protect both mothers and their unborn children.

Cytomegalovirus (CMV), a prevalent herpesvirus often contracted unknowingly by women before they reach childbearing age, is typically harmless except during pregnancy. When passed on to the developing fetus, it becomes a major cause of miscarriages and birth defects, including conditions such as cerebral palsy and hearing loss.

For a long time, scientists have been aware that the risk of complications is notably higher for women who contract CMV for the first time during pregnancy. However, the reasons why those who already carry the virus are less susceptible have not been fully understood.

The Tulane study has unveiled how pre-existing immunity to CMV effectively restricts its transmission during pregnancy and provides protection against associated birth defects. This research, published in PLOS Pathogens, identifies the specific immune mechanisms responsible for this safeguard.

Researchers at the Tulane National Primate Research Center employed a nonhuman primate model closely resembling human CMV infection and transmission. They observed that when pregnant mothers were initially infected with CMV during the first trimester, all of them transmitted the virus to their offspring, resulting in a high rate of miscarriage.

However, when nonhuman primates previously infected with CMV were reinfected during their pregnancies, their offspring were shielded. The robust immune response observed in mothers upon reinfection led to only one out of five mothers passing the virus through the placenta, with no adverse health outcomes for any of the infants.

Dr. Amitinder Kaur, the principal investigator and professor of microbiology and immunology, emphasized, “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 findings underscore that if a mother possesses CMV immunity before conceiving, her immune system can effectively shield her baby from congenital CMV transmission if she becomes reinfected during pregnancy. This research could have profound implications for the development of a CMV vaccine to prevent infections in pregnant women, particularly in regions with a high prevalence of CMV.

This study was made possible with the contributions of Matilda Moström, Ph.D., the first author and assistant director of the flow cytometry core at Tulane National Primate Research Center.

Source: Tulane University

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