The immunity conferred to pre-term babies by their mothers may be more extensive and protective than previously thought, according to researchers from the Karolinska Institute in Stockholm, Sweden. Their findings could influence infant vaccine development and the treatment of disease in newborns.  

Immunity to diseases develops when the body generates antibodies — proteins that are programmed to find and destroy or neutralise specific diseased cells. Newborn babies have not been exposed long enough to generate antibodies, and so anti-viral and anti-bacterial antibodies called immunoglobin G (IgG) are passed to babies from their mothers during pregnancy. These antibodies provide passive immunity for up to the first three months of life. However, pre-term infants are known to be more susceptible to infection, and scientists previously believed that this was because they did not receive the same levels of IgG from their mothers as those babies born full-term. 

Now, Christian Pou, and co-workers at the Karolinska Institutet have overturned this theory, following the first analysis of the full range of antibodies present in both full-term and pre-term babies and their mothers.

The study involved 78 mothers and their babies, 32 of whom were born before week 30 of pregnancy. The researchers used ground-breaking bacteriophage technology to scan samples taken from all participants. Bacteriophages are viral components that can be designed to display specific proteins on their surfaces. Antibodies related to specific diseases then bind to the phage-displayed proteins, allowing researchers to determine which antibodies are present in each sample. The bacteriophage library used by the team displayed thousands of proteins from 206 viral species; covering every virus known to infect humans, except the relatively new Zika virus.

Pou’s team were surprised to find that pre-term and full-term babies have a very similar range of IgG, regardless of their gestational age at birth. The range of maternal antibodies in babies as premature as 24 weeks mirrored those of their mothers, with immunity conferred for common viruses. 

As the team states in their paper, published in Nature Medicine in 2019; “These findings suggest that the elevated risk of infection in pre-term over full-term newborns is not determined by a lack of maternal antibodies; instead, it might be explained by weaker physical barriers in the skin, intestine, and lung or differences in exposure due to intensive care, intravenous catheters, and breathing tubes.”

The results also highlight the specific parts of viral proteins that the antibodies target, which could prove invaluable for vaccine development.  

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