A newly identified cellular process could lead to safer and more effective vaccines that protect pregnant women and newborns from dangerous infections, researchers say.

A new study in Cell describes a previously unidentified route for antibodies to transfer from the mother to the fetus, illuminating a potential way to capitalize on the process to control when and how certain antibodies are shared.

“It’s always been assumed that the types of maternal antibodies that cross over the placenta to the fetus, all antibodies had the same chance of transferring to fetus,” says senior author Sallie Permar, a professor of pediatrics and member of the Duke University Human Vaccine Institute.

“This meant there was no way we could direct certain antibodies across the placenta and to the baby,” Permar says. “Our study found that there seems to be a code on the antibody that determines which antibodies will more effectively transfer across the placenta.”

Permar and colleagues studied two populations of pregnant women in the United States and Malawi infected with HIV, known to inhibit the transfer of antibodies to the fetus—and not just HIV antibodies. The researchers say this feature provided a unique circumstance to explore a little-understood process with implications for numerous common pathogens, including tetanus, pertussis, influenza, and others.

The researchers identified a sugar molecule that interacts with placental receptors, an interaction that had previously not been known to be involved in the antibody transfer process. The finding was corroborated in healthy women by another research team publishing in the same issue of Cell.

“We have shown that the efficiency of antibody transfer across the placenta is differentially regulated,” Permar says. “This insight could improve the design of vaccines for a variety of infectious diseases to improve the transplacental antibody transfer to the fetus.”

“Our findings provide a roadmap of how antibodies cross the placenta to the baby,” says lead author David Martinez, a PhD student. “We hope our results will be useful for developing antibody therapeutics that protect infants against infectious diseases in early life.”

The National Institute of Child Health and Human Development and the National Institute of Allergy and Infectious Diseases partially funded the work.