Viral respiratory infections can predispose to the development of asthma by mechanisms that are presently undetermined. Using a murine model of respiratory syncytial virus (RSV) infection, acute infection is associated with airway hyperresponsiveness as well as enhanced responses to subsequent sensitization to allergen. We demonstrate that acute viral infection results in increased airway responsiveness to inhaled methacholine and pulmonary neutrophilic and eosinophilic inflammation. This response is associated with predominant production of Th-1-type cytokines in peribronchial lymph node cells in vitro. Mice sensitized to ovalbumin via the airways after RSV infection developed increased airway responsiveness to methacholine and pulmonary eosinophilic and neutrophilic inflammation, associated with the predominant production of Th-2-type cytokines.

In a proportion of atopic asthmatics, exposure to a relevant antigen is followed by chronic inflammation in the airways leading to altered airway responsiveness (AR). However, the mechanisms underlying the development of airway hyperresponsiveness still remain unclear. To elucidate the relationship between IgE-mediated reactions and airway hyperresponsiveness, a murine model of passive sensitization and airway challenge with ovalbumin (

The ferric uptake regulation (fur) gene Mn2+-Fur had a significantly higher affinity for the promoter fragment of sodB compared with that of random DNA sequences but significantly lower than for the promoter fragment of sodA. These observations suggest that the apparent positive regulation of sodB does not result exclusively from a direct interaction of holo (metallated) Fur itself with the sodB promoter. Nevertheless, the sodB gene also appears to be part of the iron uptake regulon but not in the classical manner of Fe-dependent repression.

We have examined the effects of repeated exposure to antigen on airway responses to cholinergic stimulation in two inbred strains of mice that are similar in underlying cholinergic airway responsiveness, yet differ in their ability to produce IgE. Both BALB/c and SJL/J mice were repeatedly exposed to ovalbumin by inhalation for a 10-d period. While the BALB/c mice developed IgE antibody to this allergen, the SJL/J strain failed to mount an appreciable IgE response. In vitro assessments of the response of tracheal smooth muscle from saline exposed mice (controls) of both strains demonstrated responses to both methacholine and electrical field stimulation that were not significantly different between the strains. Following exposure to ovalbumin, the BALB/c strain developed a significant increase in their response to electrical field stimulation, while their response to methacholine was unaltered. In contrast, the in vitro responsiveness to these stimuli did not increase in SJL/J mice following similar exposure to inhaled nebulized ovalbumin. The passive transfer of cells from the peribronchial lymph nodes of ovalbumin-sensitized BALB/c mice into syngeneic nonimmune mice also led to increases in responsiveness of tracheal smooth muscle to electrical field stimulation. In contrast, transfer of cells from nonsensitized mice did not alter responsiveness. These results suggest that murine species capable of developing an IgE response to allergen also develop alterations in the neural control of their airways. Further, this alteration appears to be lymphocyte dependent, in that cells found within peribronchial lymph nodes following allergen exposure are capable of transferring this increase in responsiveness to nonimmune mice. (J. Clin. Invest. 1992. 89:747-752.)

No abstract