Long-lived respiratory immune response to filamentous hemagglutinin following Bordetella pertussis infection.

Systemic and mucosal B-cell-mediated immune responses to purified filamentous hemagglutinin (FHA) in mice were analyzed at different times following a single respiratory infection with Bordetella pertussis. Serum immunoglobulin G (IgG) anti-FHA and respiratory IgG and IgA anti-FHA antibodies were first detected at 3 weeks postinfection, reached high levels by 8 weeks postinfection, and remained at high levels 12 to 32 weeks postinfection. FHA-specific B lymphocytes isolated from the spleens or lungs of uninfected control mice or mice convalescing from B. pertussis respiratory infection were analyzed in limiting-dilution cultures. Analysis of culture supernatants for the production of antibodies to FHA revealed an increased frequency of FHA-specific B cells of both the IgG- and the IgA-secreting classes in the lungs and tracheas of aerosol-challenged mice; these levels remained high as late as 25 weeks postinfection, compared with those in uninfected controls. No corresponding increase in the frequency of FHA-specific B cells in the spleens of aerosol-infected mice was observed. This long-lasting response observed in cultured cells was radiation resistant, a result suggesting that this response was due to B cells already activated in vivo. Polymerase chain reaction analysis revealed low but detectable levels of B. pertussis chromosomal DNA in 75% of mice tested at 8 weeks postinfection and 37.5% of mice tested at 26 weeks postinfection, at which times high levels of anti-FHA antibody were detected. One explanation for these data may be that, in this animal model, a major adhesin of B. pertussis can persist and interact with components of the immune system to stimulate the production of specific antibody in the respiratory tract many weeks after a single B. pertussis infection.