Different effects of whole-cell and acellular vaccines on Bordetella transmission

Background. Vaccine development has largely focused on the ability of vaccines to reduce disease in individual hosts, with less attention to assessing the vaccine's effects on transmission between hosts. Current acellular vaccines against Bordetella pertussis are effective in preventing severe disease but have little effect on less severe coughing illness that can mediate transmission. Methods. Using mice that are natural host's of Bordetella bronchiseptica, we determined the effects of vaccination on shedding and transmission of this pathogen. Results. Vaccination with heat-killed whole-cell B. bronchiseptica or B. pertussis inhibited shedding of B. bronchiseptica. Differences in neutrophil and B-cell recruitment distinguished sham-vaccine from whole-cell-vaccine responses and correlated with shedding output. Both B and T cells were essential for vaccine-induced control of shedding. Adoptive transfer of antibodies was able to limit shedding, while depletion of CD4⁺ T cells led to increased shedding in vaccinated mice. Finally, whole-cell vaccination was able to prevent transmission, but an acellular vaccine that effectively controls disease failed to control shedding and transmission. Conclusions. Our results highlight discrepancies between whole-cell and acellular vaccination that could contribute to the increased incidence of B. pertussis infection since the transition to the use of acellular vaccination.