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Antibodies to group B streptococci in neonates and infants
1Department of Paediatrics, Mölndal Hospital, Sweden. stefan.berg@digit.se
Insights
Maternal antibodies against group B streptococcal (GBS) capsular polysaccharides (CPS) do not explain the low incidence of GBS infections after the neonatal period. Antibody levels decrease in infants, and early acquisition of protective antibodies was not observed.
Area of Science:
- Neonatal immunology
- Infectious disease epidemiology
- Bacterial pathogenesis
Background:
- Invasive group B streptococcal (GBS) infections are a leading cause of neonatal morbidity and mortality.
- The incidence of invasive GBS infections significantly declines after the first month of life, a pattern distinct from other encapsulated bacterial pathogens.
- The immunological mechanisms underlying this age-specific protection against GBS remain largely unknown.
Purpose of the Study:
- To investigate whether the acquisition of serum antibodies against GBS capsular polysaccharides (CPS) during early infancy contributes to the reduced incidence of invasive GBS disease after the neonatal period.
- To determine the levels and trends of IgG and IgM antibodies against common GBS serotypes (Ia, II, and III) in newborns and infants up to six months of age.
Main Methods:
- Serum samples were collected from 321 healthy term newborns (cord blood) and at multiple time points up to 26 weeks of age.
- Enzyme-linked immunosorbent assay (ELISA) was employed to quantify IgG and IgM antibody levels against GBS serotypes Ia, II, and III CPS.
- Longitudinal analysis tracked antibody dynamics from birth through the first six months of life.
Main Results:
- Virtually all neonates possessed high levels of IgG antibodies against GBS serotypes Ia, II, and III CPS at birth (98%-100%).
- These maternal IgG antibody levels showed a consistent decline throughout the first six months of life.
- IgM antibodies against GBS serotype III CPS were absent in cord sera and were acquired by only a small proportion (16%-17%) of infants by 3-6 months of age.
Conclusions:
- The early acquisition of significant levels of IgG or IgM antibodies against the most common GBS serotypes was not observed in infants.
- The presence of maternal antibodies at birth wanes, and insufficient active antibody acquisition occurs in early infancy to explain the rarity of invasive GBS infections after the neonatal period.
- The findings do not support the hypothesis that antibody acquisition against GBS CPS explains the age-dependent decrease in invasive GBS disease incidence.
Unlabelled:
Invasive group B streptococcal (GBS) infections are common in neonates but are rare after the 1st month of life. It is not known why GBS infections have this age distribution which differs from that of invasive infections caused by other encapsulated bacteria. The aim of this study was to test the possibility that serum antibodies against the GBS capsular polysaccharides (CPS) are acquired during the first months of life thereby preventing infections after the neonatal period. Cord sera were collected from 321 healthy term newborns. A second blood sample was collected at 2, 4, 8, 13 or 26 weeks of age. IgG CPS antibodies (measured by ELISA) against serotypes Ia, II and III were present in 98%-100% of all cord sera and decreased continuously during the first 6 months of life. No IgM antibodies against serotype III CPS were present in cord sera. Only 16%-17% of the children acquired IgM antibodies against serotype III CPS at 3 and 6 months of age.
Conclusion:
Early acquisition of IgG or IgM antibodies against CPS of the most common GBS serotypes was not demonstrated and cannot explain the rare occurrence of invasive GBS infections in children after the 1st month of life.