PARAINFLUENZA VIRUS TYPE-3 INFECTION ATTENUATES THE RESPIRATORY EFFECTS OF ANTIGEN CHALLENGE IN SENSITIZED GUINEA-PIGS

Respiratory viral infections not only exacerbate asthma symptoms but m ay also be important in the pathogenesis of the disease. We therefore explored the effects of respiratory viral infection on the respiratory response of sensitized guinea pigs to antigen challenge. Lung tissue obtained from uninfected guinea pigs sensitized to ovalbumin aerosol r eleased histamine upon incubation with the antigen in vitro. After ant igen challenge in vivo, sensitized animals had significantly greater n umbers of eosinophils in their bronchoalveolar lavage fluid than did n onsensitized animals and exhibited airway hyperresponsiveness to metha choline aerosol. When ovalbumin sensitization was initiated 7 days aft er inoculation with parainfluenza virus type-3 (PI-3), antigen challen ge elicited little histamine release from infected lung tissue in vitr o. Likewise, subsequent to antigen challenge in vivo, animals failed t o exhibit airway hyperresponsiveness or an increased eosinophil popula tion in bronchoalveolar lavage fluid. Similar effects were observed wh en sensitization was begun 19 days after PI-3 virus inoculation. The m echanism(s) responsible for the attenuated responses to antigen in PI- 3 infected animals are unknown but may involve virus-induced effects o n immune cells.