PROJECT 1 – ABSTRACT Immunization during pregnancy is an effective intervention for protection of both mothers and their infants prior to infant’s routine vaccination. Tetanus, B. pertussis and seasonal influenza vaccines are administered to pregnant women and offspring benefit from vaccine-induced antibodies which are transferred during gestation via placenta and postnatally via breast milk. Vaccines given to pregnant women, however, have not been designed for this specific group, but are targeted for and tested in the non-pregnant healthy adults. A profound immune modulation takes place during gestation, which is expected to influence responses to vaccines. Our preliminary data revealed differentially glycosylated vaccine-specific serum IgG subtypes in pregnant women following seasonal flu vaccination with an increase in di-galactosylation indicative of non-inflammatory state. Antibodies produced by pregnant women also diverged in avidity and function. MADI Project 1 will investigate biophysical and functional features of humoral immunity as well antigen-specific B and T cell responses to vaccines [Tetanus, Diphtheria and acellular Pertussis (TdaP) and influenza] administered to pregnant women and non-pregnant controls. Three aims are proposed to: Aim 1 – Investigate the impact of pregnancy on humoral, B and T cell responses to vaccines. We will determine the dynamic profile of Ab glycosylation, and Fab- and Fc-mediated anti-microbial activity during pregnancy and up to 6 months post-delivery applying traditional assays as well as the innovative systems serology platform We will also interrogate kinetics of vaccine-specific B and T cell responses and their association with antibody modifications. Aim 2 – Identify distinct features of vaccine-induced Ab in breast milk. Antibody glycan profile and function will be examined longitudinally in breast milk from Tdap and influenza-vaccinated mothers. Features of Ab in breast milk will be compared with those of with Ab in circulation. Aim 3 – Determine in vivo attributes of vaccine-specific maternal Ab. Mechanistic experiments involving mouse adoptive transfer of differentially glycosylated antibodies will be conducted to ascertain the impact of pregnancy-associated glycan modifications on antibody longevity and protective capacity of antibodies in vivo. Such detailed characterization of humoral and cellular response evolution and mechanistic interrogation of function during and after pregnancy has not been conducted. Understanding the impact of pregnancy on vaccine responses will inform the development of effective vaccines to improve the health of mother and child.