Figure 6.

Effect of heterologous mother–pup vaccination on protection against Bordetella pertussis challenge. (A) Schematic representation of vaccination and challenge protocols. Female mice were immunized with three doses of commercial aP vaccine on days 0 and 14; mated with male mice; and when the vaginal plug was detected, a third aP dose was administered. Four weeks after birth, the offspring received either no vaccine (n = 8) or one dose of the aP, OMV, or wP vaccine (n = 8 in each group), as indicated below the abscissas of panels (B,C). Two weeks later, the pups were challenged with B. pertussis and the bacterial burden in the lungs measured 7 days after challenge. Pups born to vaccinated or non-vaccinated mothers and receiving no postnatal vaccine served as controls. The pups (n = 5 for each group) were bled and the anti-pertussis toxin (a-PTxA) IgG titers determined 1 day before the challenge as designated by the dotted vertical arrow. (B) The titers, plotted on the ordinate, are expressed as the geometric mean of the data from each group specified on the abscissa. *p < 0.05 pups born to immunized mother versus others groups, and the nd signifies not detected. (C) In the figure, the number of bacteria recovered from the mouse lungs, expressed as the log₁₀(mean CFUs ± SD per lung), is plotted on the ordinate for each group indicated on the abscissa. *p < 0.05 for negative control versus other groups, and aP-immunized pups born to non-immunized mother versus others groups. The dotted horizontal line marks the lower limit of detection. Of the three independent experiments that were performed, the results from a single representative one is presented.