Sexual dimorphism in lung function responses to acute influenza A infection

Background Males are generally more susceptible to respiratory infections; however, there are few data on the physiological responses to such infections in males and females. Objectives To determine whether sexual dimorphism exists in the physiological/inflammatory responses of weanling and adult BALB/c mice to influenza. Methods Weanling and adult mice of both sexes were inoculated with influenza A or appropriate control solution. Respiratory mechanics, responsiveness to methacholine (MCh), viral titre and bronchoalveolar lavage (BAL) cellular inflammation/cytokines were measured 4 (acute) and 21 (resolution) days post-inoculation. Results Acute infection impaired lung function and induced hyperresponsiveness and cellular inflammation in both sexes at both ages. Males and females responded differently with female mice developing greater abnormalities in tissue damping and elastance and greater MCh responsiveness at both ages. BAL inflammation, cytokines and lung viral titres were similar between the sexes. At resolution, all parameters had returned to baseline levels in adults and weanling males; however, female weanlings had persisting hyperresponsiveness. Conclusions We identified significant differences in the physiological responses of male and female mice to infection with influenza A, which occurred in the absence of variation in viral titre and cellular inflammation.