Placental Histopathology and Transplacental Transfer of RSV-specific Neutralizing Antibodies The Silver Study.

BACKGROUND: Maternally acquired passive immunity via transplacental antibody transport is crucial for the protection of infants against infectious diseases in early life. We examined whether placental histological characteristics impact the transplacental transfer of natural respiratory syncytial virus (RSV)-specific neutralizing antibodies. METHODS: We performed a prospective, observational, cross-sectional study. Pregnant women were enrolled with a 1:1:1 inclusion ratio of extremely preterm-born infants (24-32 weeks), moderately preterm-born infants (33-36 weeks) and term-born infants (37-42 weeks). Cord-maternal ratios (CMRs) for serum neutralizing RSV-A and -B antibodies were analyzed in relation to 16 placental histologic characteristics. RESULTS: In total, 85 mother-infant pairs were available for analysis. Infant gestational age was significantly correlated with CMRs for RSV-A and -B specific antibodies (B = 0.10, P < 0.001). Although a few placental characteristics showed a univariate association with CMR, the multivariate model showed that only gestational age was independently related to CMR (B = 0.11, P < 0.001). CONCLUSIONS: Our study confirms that CMRs increase during gestation. However, variations in placental histology may not affect transplacental RSV-A and RSV-B antibody transfer. We hypothesize that the placental compensatory capacity and active transport mechanism may play a key role in transplacental antibody transfer.