One of the most useful tools that doctors have when it comes to fighting infectious diseases is, without a doubt, vaccination. But it is still of limited efficacy in protecting a specific group of patients: newborns, who come into the world with new immune systems that still cannot tell the difference between benign and harmful microbes. Therefore, they depend on the antibodies transmitted to them by their mothers through the placenta.
An investigation carried out by the Ragon Institute at Massachusetts General Hospital, MIT and Harvard – published in the journal ‘Cell’ – has just determined how exactly the transfer of immunity induced by vaccines from a mother’s body occurs to your baby. This research could be helpful in developing more effective maternal vaccines.
“To help the newborn’s immune system learn to discriminate between friend and foe, mothers transfer antibodies to their babies through the placenta,” explains Galit Alter, a doctor at the Massachusetts General Hospital (MGH) Department of Medicine and co-author. “We did not know the rules by which the placenta performs this absolutely essential function, but if decoded, they could be the key to generating more powerful vaccines.”
While maternal antibodies to some diseases, such as measles, can be transferred from mother to child and provide some protection until the child is old enough for individual vaccination, antibodies to other serious diseases, such as polio, are transferred from less efficient way.
NK cells, keys
To investigate the mechanisms by which antibodies are transferred from mother to child, Alter and her team – including lead author Laura Riley, president of Obstetrics and Gynecology at Weill Cornell Medicine School – used a novel tool called system serology to to compare the quantity and quality of pertussis antibodies in blood samples from mothers and umbilical cords that carry blood, nutrients and immune factors from the placenta to the baby.
Their research revealed that the placenta gives preference to infant antibodies that activate natural killer (NK) cells, key elements of the innate immune system. While several important immune cells are too immature in newborns to provide effective protection, NK cells are among the most abundant and functional immune cells during the first days of life.
The team found a similar preference for placental transfer of NK-activating antibodies against influenza and respiratory syncytial virus – a common childhood disease – and also identified antibody characteristics that appear to regulate placental selection, characteristics that could possibly be incorporated to next-generation vaccines for better mother-to-child antibody transfer.
“Now we will have the opportunity to create better maternal vaccines and to deliver them at the ideal time during pregnancy to best protect newborns when they are most vulnerable,” concludes Riley.
