Influenza A virus infection increases IgE production and airway responsiveness in aerosolized antigen-exposed mice.

BACKGROUND

Respiratory viral infection is known clinically to promote sensitization to antigen inhalation and the development of asthma.

OBJECTIVE

The purpose of this investigation was to determine whether influenza type A virus infection enhances inhalation sensitization and increases airway responsiveness in mice.

METHODS

Mice were infected by intranasal inoculation with influenza A viruses (strains: H1N1 and H3N2) or PBS. Animals were exposed to aerosols of ovalbumin on day 3. Two weeks after ovalbumin sensitization, mice were challenged with ovalbumin aerosols; 24 hours later, airway responsiveness (AR) to inhaled methacholine, levels of ovalbumin-specific IgE, and bronchoalveolar lavage fluid (BALF) were examined.

RESULTS

Neither influenza A virus (H1N1 nor H3N2) alone nor ovalbumin sensitization alone caused changes in AR or IgE. However, ovalbumin sensitization after inoculation with either influenza A virus increased AR and levels of ovalbumin-specific IgE. On BALF-cell analysis, ovalbumin sensitization after inoculation with influenza virus A increased the number of lymphocytes but not the number of eosinophils. No difference in AR or IgE levels was observed between the 2 strains of influenza A viruses. Immmunostaining of BALF cells showed an increase in T cells, especially CD8(+) cells, with ovalbumin sensitization after inoculation with influenza virus A.

CONCLUSION

Infection by influenza A virus enhances sensitization to inhaled antigens and airway responsiveness in mice by means of mechanisms including CD8(+) cells and antigen-specific IgE.