The longevity of the immune response to filamentous hemagglutinin and pertussis toxin in patients with pertussis in a semiclosed community.

Titers of antibodies to the filamentous hemagglutinin (FHA) and pertussis toxin (PT) of Bordetella pertussis were studied in patients from a semiclosed community after an outbreak of the disease in 1985 and in the general population. In convalescent-phase serum obtained after B. pertussis infection in patients in the semiclosed community, high anti-FHA IgG and anti-PT IgG titers were observed; these titers tended to disappear over the next 5 years. On the other hand, among the medical staff, high anti-FHA and anti-PT IgG titers persisted during the same 5-year period. It seems likely that anti-FHA and anti-PT IgG levels reflect the frequency of exposure to the bacteria and that B. pertussis is widespread in the Japanese population. Although the anti-FHA IgG antibody response decreased in patients from the semiclosed community, the cellular immune response was maintained.