Protection of mice against respiratory Bordetella pertussis infection by intranasal immunization with P.69 and FHA

Intranasal immunization of adult female Balb/c mice with the Bordetella pertussis antigens FHA or P.69, greatly enhanced their ability to clear B. pertussis from their lungs following aerosol challenge compared with ovalbumin-immunized controls. Low numbers of lymphocytes secreting antibodies (IgG, IgA and IgM) against the immunizing antigens could be isolated from the lungs of immunized mice. Following aerosol challenge with B. pertussis there was a large increase in the numbers of FHA or P.69-specific antibody-secreting cells in the lungs of mice immunized with these antigens. Intranasal immunization, particularly with FHA, also primed mice to develop a systemic serum anti-pertussis antibody response subsequent to challenge. However, pulmonary clearance of B. pertussis correlated most closely with the local antibody response. A strong anti-FHA response was demonstrated in the lungs of mice that received a booster dose of FHA 9 months after their previous exposure to FHA, demonstrating that long immunological memory can develop in the murine respiratory tract following direct application of pertussis antigens to the respiratory tract mucosa.