The prevalence of allergic diseases such as
asthma has increased markedly over the past few decades. To evaluate the possible mutual influence of helminth
infection and
allergy, the combined effects of experimental allergic airway
inflammation and
infection with Strongyloides venezuelensis on various parasitological and inflammatory indices were evaluated in the rat. A challenge of immunized rats with aerosolized
ovalbumin (OVA) resulted in eosinophilic
inflammation that peaked 48 h after the challenge and was accompanied by
airway hyperresponsiveness (AHR) to an intravenous
acetylcholine challenge. S. venezuelensis
infection concomitant with an OVA challenge of immunized rats resulted in prolonged
pulmonary inflammation with increased eosinophil infiltration in bronchoalveolar lavage fluid but not in the lung tissue. These rats also showed a significant parasite burden reduction, especially during parasite migration through the lungs. However, the fecundity rates of worms that reached the intestine were similar in allergic and nonallergic animals. Despite airway
inflammation, the increased responsiveness of the airways in the experimental
asthma model was suppressed during parasite migration through the lungs (2 days). In contrast, parasite-induced AHR was unchanged 5 days after
infection in immunized and challenged rats. In conclusion,
infection with S. venezuelensis interfered with the onset of AHR following an
antigen challenge of immunized rats. The ability of parasites to switch off functional airway responses is therapeutically relevant because we may learn from parasites how to modulate lung function and, hence, the AHR characteristic of asthmatic patients.