Class antibody responses to pertussis toxin (PT), filamentous hemagglutinin (FHA), and agglutinogens 2 and 3 (Agg 2/3) were studied in 114 patients with pertussis, 49 family contacts of patients with pertussis, and 139 infants attending vaccination clinics. IgG responses to FHA and PT were similar in patients with pertussis and in infants immunized three times with whole-cell pertussis vaccine. IgA responses to FHA and PT were greater in patients with pertussis than in vaccinees, and a serum logi0 titer of IgA to PT >1.9 was a useful discriminant of Bordetella pertussis infection. When compared with patients with pertussis, vaccinees had a greater IgG response to Agg 2/3 and an equivalent IgA response to Agg 2/3. Serologic responses to FHA, PT, and Agg 2/3 were common in family contacts but were smaller than the responses in patients with pertussis. Initial titers of IgG to FHA and IgA to FHA were significantly higher (P <.005 and P <.05, respectively) in family contacts aged 3-10 y than in patients with pertussis in an identical age group.
Bibliographical noteFunding Information:
This work was supported in part by a grant from the Department of Health and Social Security (to M. G. T.).
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