B cell priming in utero to influenza vaccination

Abstract

Rationale Influenza vaccination is recommended for women who are pregnant during the influenza season. Nonetheless, the development of B cell priming to influenza antigens in utero is controversial. We hypothesized that neonatal B cells will exhibit antigen specific immune responses following influenza vaccination of the pregnant mother. Methods Thirty pregnant women were recruited and vaccinated (mean gestation 25.80 ± 0.82 weeks) during the influenza season. Fluzone and Matrix Protein (MP)-antigen specific IgM and IgG titers were measured by ELISA in mothers pre- and postpartum and newborns postpartum. Results 18/30 (60%) mothers showed a positive Fluzone antigens-IgM response (mean Optical Density (OD) ratio 5.57 ± SE 1.11)[Positive response defined as OD post vaccine/OD pre vaccine >2]. 14/30 (46.7%) had a positive response to MP antigens (mean OD ratio 6.93 ± 2.25). In comparison, 9/17 (53%) newborns demonstrated a Fluzone-specific IgM response [OD 2 fold >OD measured in the cohort born to nonvaccinated mothers]. Their mean Fluzone IgM averaged 0.041 ± 0.013 ( p<0.05, Mann-Whitney U, compared to the nonvaccinated cohort). 8/17 newborns (47%) had a positive MP IgM. Their mean MP IgM averaged 0.024 ± 0.008 ( p<0.05, Mann-Whitney U, compared to the nonvaccinated cohort). In addition, 9/30 (30%) mothers showed a positive Fluzone-IgG response (average OD ratio 4.89 ± 2.31), whereas 13/30 (43%) responded to MP (average OD ratio 4.11 ± 1.32). Fluzone IgG levels among the newborns of vaccinated mothers (mean 2.17 ± 0.29) were greater than those from the nonvaccinated cohort (mean 0.65 ± 0.10) ( p<0.05, Mann-Whitney U). Conclusions The increased Fluzone, MP-specific IgM levels suggest that in utero B cell priming to influenza antigens occurs following vaccination of the mother during pregnancy.