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Published on: January 26, 2019
Low Cord Blood Titers Are Associated with Prolonged Maternal RSV Antibody Half-Lives in Preterm Infants
Joukje E Willemsen1,2, Emily W E M Phijffer1, Joanne G Wildenbeest1
1Department of Paediatric Infectious Diseases and Immunology, Wilhelmina Children's Hospital, University Medical Center Utrecht, Utrecht, The Netherlands.
Insights
Preterm infants have longer-lasting RSV antibodies, but higher initial antibody levels lead to faster declines. This suggests vaccine protection differences between preterm and term infants might be smaller than expected.
Area of Science:
- Immunology
- Neonatal Research
- Infectious Disease
Background:
- Preterm infants face higher risks of severe Respiratory Syncytial Virus (RSV) infection due to lower maternal antibody transfer.
- This heightened susceptibility to RSV infection continues into the infant's first year of life.
Purpose of the Study:
- To investigate the decay rate (kinetics) of RSV-neutralizing antibodies after birth in both preterm and full-term infants.
- To understand how gestational age and initial antibody levels influence this decay process.
Main Methods:
- Serum samples were collected from infants born to unvaccinated mothers at birth, 1-2 weeks, and 4-8 weeks postpartum.
- Linear mixed-effects models were employed to calculate antibody half-lives, correlating them with gestational age and cord blood antibody titers.
- Total serum IgG1 levels were also analyzed to validate the findings on RSV-neutralizing antibodies.
Main Results:
- Infants born prematurely exhibited a significantly longer half-life for RSV-neutralizing antibodies compared to full-term infants (approx. 79 days for very preterm vs. 30 days for term).
- Higher initial antibody levels at birth were associated with a faster decline; a twofold increase in cord blood titers reduced antibody half-life by approximately 20% for RSV-neutralizing antibodies and 32% for IgG1.
- The observed relationship between gestational age and antibody half-life was primarily explained by the inverse correlation between cord blood antibody levels and antibody half-life.
Conclusions:
- The duration of antibody presence after birth is inversely related to the initial antibody concentration, with higher levels diminishing more rapidly.
- These findings may imply that the disparity in vaccine-induced protection between preterm and term infants could be less pronounced than previously assumed, warranting further investigation.
Background:
Preterm infants are at higher risk of severe RSV infection, partially because of reduced placental transfer of maternal antibodies (Abs). Increased risk of severe infection persists in the first year of life. This study evaluates the postnatal kinetics of RSV neutralizing antibodies in preterm and full-term infants born to unvaccinated mothers.
Methods:
We enrolled infants with a gestational age (GA) of 24-42 weeks born in hospital from RSV-unvaccinated mothers. Serum was collected at birth (cord blood), 1-2 weeks, and 4-8 weeks. Linear mixed-effects models were used to estimate half-lives of RSV-neutralizing Abs in relation to GA and cord blood titer. Analyses were repeated for total serum IgG1 to confirm the robustness of our findings.
Results:
Of 169 infants, 95 were born preterm (<37 weeks GA, including 53 neonates <32 weeks GA). Premature birth was related to prolonged half-life of RSV-neutralizing Abs (∼79 days very preterm to ∼30 days in term infants). The inverse association between gestational age and antibody half-life was largely accounted for by an inverse association between cord blood Ab levels and Ab half-life. A doubling in cord blood titers led to a reduction in half-life of ∼20% for RSV neutralizing Abs and ∼32% for IgG1.
Conclusions:
Postnatal antibody half-life depends on starting levels: higher titers decline faster. If our observation would be replicated for vaccine-induced Abs, the difference in vaccine protection between preterm and term infants may be smaller than anticipated.
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