Bronchial hyperreactivity to histamine induced byHaemophilus influenzae vaccination

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Abstract
Bronchial hyperreactivity to histamine 4 days following vaccination with the human respiratory pathogenHaemophilus influenzae was tested in twoin vivo and onein vitro models. Conscious vaccinated guinea pigs exposed to aerosolized histamine became asphyxial significantly faster than saline-treated controls. Also the bronchoconstriction in anaesthetized guinea pigs as a result of i.v. histamine was significantly potentiated in theH. influenzae pretreated group. Isoprenaline (30μg/kg) partially inhibited the bronchoconstriction. The difference in histamine sensitivity between the two groups however remained. Protection against bronchoconstriction by atropine on the other hand was significantly enhanced in the vaccinated animals. This suggests a hyperreactivity of the parasympathetic, cholinergic pathways as a result ofH. influenzae vaccination.