Neutralizing antibodies to pertussis toxin in whooping cough.

The development and duration of neutralizing antibodies (antitoxin) to pertussis toxin were studied in 38 patients with culture-verified infections due to Bordetella pertussis and one patient with infection due to Bordetella parapertussis. An in vitro neutralization test in microplate culture of Chinese hamster ovary cells was used. An antitoxin response was recorded in 36 patients, the exceptions being two patients treated early with erythromycin (one of whom developed clinical pertussis two years later) and the patient with infection due to B. parapertussis. A long-term follow-up for several months to several years after disease showed maintenance of high antitoxin levels. These results are in accordance with the hypothesis that antibodies to pertussis toxin mediate long-term immunity to whooping cough.