Influence of maternal antibodies on active pertussis toxoid immunization of neonatal mice and piglets.

Whooping cough caused by infection with Bordetella pertussis, is a serious illness in infants and young children. Mortality due to whooping cough is being reported in infants too young to be immunized as well as those who have not completed their series of vaccinations. One of the major factors that interferes with successful active immunization in early life is the presence of maternal antibodies (MatAbs). Using the mouse and pig models, we evaluated the effect of maternal antibodies on active immunization with pertussis toxoid (PTd) and explored strategies to overcome this interference. Our results indicate that passively transferred maternal antibodies interfered with active immunization using pertussis toxoid. The level of passively transferred antibodies directly correlated with the level of interference observed. However, this interference could be overcome by using a second booster immunization or by co-formulating the toxoid with novel adjuvants. These results support the need for novel vaccine formulations that are optimized for the neonate and that can be used not only to modulate the inherently biased neonatal immune system but also to prime the response in the presence of passively transferred maternal antibodies.