Routine Newborn Blood Spots Can Measure GBS Antibody Levels

Group B Streptococcus (GBS) can cause serious infections in newborns. Protecting infants remains challenging because immune protection may depend on antibodies transferred from mother to baby before birth. In Denmark, newborns routinely undergo heel-prick blood sampling a few days after delivery to screen for rare congenital diseases. A new study shows that these routinely collected samples can also measure antibodies against GBS.

Aarhus University (Aarhus, Denmark) researchers evaluated heel-prick blood samples, also described as PKU cards, as a practical alternative to standard newborn blood samples for assessing GBS antibody levels. The method measures immunoglobulin G (IgG) antibodies against GBS alpha-like surface proteins (AlpN). The aim was to determine whether antibody concentrations in PKU cards and umbilical cord serum reflect concentrations found in serum from the newborn.

The study was a small proof-of-concept, cross-sectional study. Pregnant women were enrolled at 35–37 weeks of gestation during routine midwife consultations at Kolding Hospital between June 2023 and January 2024. The researchers compared GBS antibody measurements from heel-prick samples and umbilical cord blood with measurements from standard blood samples taken from the same newborns.

The results showed that heel-prick samples closely reflected the level of GBS antibodies found in standard blood samples. Umbilical cord blood also generally provided a good indication of the baby’s antibody level. The findings suggest that existing newborn blood sampling material can be used to study how many maternal antibodies against GBS are transferred before birth.

The main Danish collaborators were Lillebælt Hospital/Kolding and Vejle Hospital, Aarhus University, Aarhus University Hospital, and the University of Southern Denmark. The main international collaborators were MinervaX and the Centre for Neonatal and Paediatric Infection/Vaccine Institute, University of London. The research team has begun investigating the relationship between newborn GBS antibody levels and infection risk, with plans to expand the work using a larger group of blood samples from different populations and countries.

The findings are particularly relevant to researchers and vaccine developers working on GBS vaccines for pregnant women. The team aims to determine what level of antibodies is required to protect newborns. 

“To improve our ability to protect newborns against serious GBS infections, we need to know how effectively mothers can transfer antibodies to their babies before birth. We can now gain that knowledge, having shown that the heel-prick samples already collected from newborns can be used to measure antibody levels,” said May Murra, a postdoc at the Department of Biomedicine at Aarhus University.

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