History of whooping cough in nonvaccinated Swedish children, related to serum antibodies to pertussis toxin and filamentous hemagglutinin

Exposure to whooping cough, a serious infectious disease in children, has been difficult to evaluate in the past due to lack of reliable tests. Careful questioning of parents about the symptoms has been used, but occasionally the disease may be atypical and therefore may go unrecognized. Two new tests (using enzyme-linked immunosorbent assays, ELISA) have been developed which determine the presence, in children's blood, of antibodies which recognize two proteins from the whooping cough bacteria (Bordetella pertussis), one of which is shared by other Bordetella bacteria. Parents of 266 Swedish children (who generally are no longer vaccinated against whooping cough) were questioned as to the possible occurrence of the disease in the children, and antibodies against the Bordetella proteins were measured. About one-half of the children had antibodies to either or both proteins, and the prevalence of antibodies increased with age. Antibodies to the nonspecific protein, filamentous hemagglutinin (FHA), were more prevalent. The protein test results were compared to results using another method which measured neutralizing antibodies, and the two methods correlated well. Of the 91 children whose parents reported occurrence of whooping cough, 90 had antibodies to one or both proteins. In contrast, only 14 percent of 175 children without history of whooping cough had detectable antibodies to the specific protein, and 36 percent had antibodies to the nonspecific protein. The results show a good correlation between parental information and serum antibody measurements. Interestingly, the data suggest that 14 percent of the children had atypical cases of whooping cough. Follow-up of children in the study indicated that antibodies to Bordetella pertussis may be protective against the infection. (Consumer Summary produced by Reliance Medical Information, Inc.)