Kinetics of antibodies against major pneumococcal proteins in mother and child (HUM8P.348)

Abstract Invasive pneumococcal diseases (IPD) are responsible for almost 1 million deaths per year among children under five years. Streptococcus pneumoniae has over 90 serotypes yet the current conjugate vaccine only includes 13 serotypes. Pneumococcal proteins are conserved across all serotypes and therefore hold potential as vaccine candidates. Study aimed to investigate the transfer of antibodies against major pneumococcal antigens from pregnant mothers to their infants, and to correlate antibody concentrations with nasopharyngeal carriage (NPC).We analysed plasma from mother’s (3 months post-birth) and infants(cord blood) to determine antibody concentrations and avidity to recombinant pneumolysin (rPly), Pneumococcal surface protein A (PspA) and choline-binding protein A (CbpA) using an in-house IgG ELISA. Antibody transfer was antigen-dependent with significantly higher levels of antibodies against PspA and CbpA in mothers compared to cord blood but similar levels for rPly. PspA and CbpA were better transferred than rPly from mother to child (p=0.0001 and p=0.0024 respectively). Antibodies to PspA and CbpA but not rPly were retained up to 3 months in mothers with no significant difference in the avidity index at any time-point. Our data shows that transfer of antibodies against major pneumococcal proteins from mother to child is antigen-dependent. Further work will explore the relationship with NPC.