Bronchial challenge of tropical asthmatics with Ascaris lumbricoides.

Despite the fact that helminthic parasites can stimulate strong immediate hypersensitivity reactions, it is uncertain whether these are relevant to the development of allergic disease in infected patients. In order to examine this possibility, we tested 20 informed chronic asthmatic patients from an Ascaris-endemic area by bronchial challenge with a partially purified extract of this parasite. Sequential measurements were made of both the forced expiratory volume in the first second (FEV1) and the peak expiratory flow rate (PEFR) up to 6 h postchallenge, then of PEFR from 6 to 14 h and at 24 h. These were compared to the effect of control inhalations of saline. Extremely low doses of Ascaris antigen that did not exceed 10 PNU (6 x 10(-7) g of protein) induced significant reductions (> 20%) in FEV1 within 30 min in 3 (15%) patients, and in PEFR in 5 cases (25%). By 6 h postchallenge, 5 (25%) subjects showed significant alterations in FEV1, and 10 (50%) in PEFR. Significant changes in PEFR were recorded between 6 and 24 h in 12 (60%) patients. The challenge of nonasthmatic subjects from the same Ascaris-endemic area did not produce notable changes in pulmonary function, and although asthmatics with no evidence of prior contact with the parasite showed a certain degree of immediate bronchial reactivity to the parasite extract, the late responses were significantly less frequent than in the infected patients. No correlations were detected between the bronchial responses and skin test reactivities to the Ascaris extract, or serum levels of specific IgE or IgG antibody.(ABSTRACT TRUNCATED AT 250 WORDS)