Protective antigens of Bordetella pertussis mouse-protection test against intracerebral and aerosol challenge of B. pertussis.

Pertussis toxin (PT) and filamentous hemagglutinin (FHA) which are the main components of pertussis vaccine in Japan, were investigated concerning their role as protective antigens. Four different experiments were carried out to investigate the ability of the antigens or antibodies to protect mice from pertussis infection: 1) Mice immunized with formalinized PT (PTd) and/or FHA (f-FHA) were tested by the intracerebral challenge system; 2) suckling mice immunized through the placenta or the milk of a mother immunized with PTd or f-FHA were tested in the aerosol challenge system; 3) suckling mice immunized by intraperitoneal injection of anti-PT and/or anti-FHA mouse antibody were tested by the aerosol challenge system; and 4) suckling mice immunized by intraperitoneal injection of monoclonal antibody against the largest subunit protein (S1) of PT were tested in the aerosol challenge system. It was concluded in all experiments performed that PTd or anti-PT antibody was a more potent protective antigen or antibody than f-FHA or its antibody, but the coexistence of both antigens or antibodies was much more potent. The synergistic effect caused by the different roles of the two antigens or antibodies was presented and discussed.