The O Antigen Is a Critical Antigen for the Development of a Protective Immune Response to Bordetella parapertussis

Abstract

ABSTRACT Despite excellent vaccine coverage in developed countries, whooping cough is a reemerging disease that can be caused by two closely related pathogens, Bordetella pertussis and B. parapertussis . The two are antigenically distinct, and current vaccines, containing only B. pertussis -derived antigens, confer efficient protection against B. pertussis but not against B. parapertussis . B. pertussis does not express the O antigen, while B. parapertussis retains it as a dominant surface antigen. Since the O antigen is a protective antigen for many pathogenic bacteria, we examined whether this factor is a potential protective antigen for B. parapertussis . In a mouse model of infection, immunization with wild-type B. parapertussis elicited a strong antibody response to the O antigen and conferred efficient protection against a subsequent B. parapertussis challenge. However, immunization with an isogenic mutant lacking the O antigen, B. parapertussis Δ wbm , induced antibodies that recognized other antigens but did not efficiently mediate opsonophagocytosis of B. parapertussis . The passive transfer of sera raised against B. parapertussis , but not B. parapertussis Δ wbm , reduced B. parapertussis loads in the lower respiratory tracts of mice. The addition of 10 μg of purified B. parapertussis lipopolysaccharide (LPS), which contains the O antigen, but not B. parapertussis Δ wbm LPS drastically improved the efficacy of the acellular vaccine Adacel against B. parapertussis . These data suggest that the O antigen is a critical protective antigen of B. parapertussis and its inclusion can substantially improve whooping cough vaccine efficacy against this pathogen.