Impact of maternal pertussis antibodies on the infants' cellular immune responses.

INTRODUCTION Maternal antibody interference of the infant's humoral immune responses raises some concern to the strategy of maternal Tdap (tetanus, diphtheria, acellular pertussis [aP]) vaccination. This study assessed the impact of maternal Tdap antibodies on the infant's pertussis-specific T lymphocyte responses following infant vaccination with an aP containing vaccine, in a term and preterm born cohort. METHODS Heparin samples (±0.5mL) were conveniently drawn from infants of a Belgian prospective cohort study (N=79, NCT02511327), including Tdap vaccinated (Boostrix®) and non-vaccinated women (no Tdap vaccine in the last 5 years) that delivered at term or prematurely. Sampling was performed before and one month after primary (8-12-16 weeks) and booster vaccination (13 or 15 months) with DTaP-IPV-HB-PRP~T vaccine (Hexyon®). Pertussis toxin (PT)-specific CD3 +, CD3 +CD4 + and CD3 +CD8 + lymphoblasts and their cytokine secretions were measured using a flow cytometric assay on whole blood (FASCIA) and multiplex technology (Meso Scale Discovery), respectively. RESULTS 57% of all infants were considered PT-specific CD3 +CD4 + lymphoblasts responders after primary and booster vaccination, whereas 17% were CD3 +CD8 + lymphoblast responders. IFN-γ, IL-13, IL-17A and IL-5 cytokine secretions after primary and booster vaccination were indicative of a mixed T helper (Th) 1/Th2/Th17 cell profile. Lymphoblast and cytokine levels were comparable between term and preterm infants. Non-responders for IL-13 after booster vaccination had higher maternal PT IgG levels at birth when compared to responders. CONCLUSIONS Term and preterm born infants are capable of inducing Th1, Th2 and Th17 responses after aP vaccination, yet maternal vaccination modulate these responses. Evaluation of this effect in larger trials is needed.