Influenza infection facilitates allergen-specific responses in pre-sensitized mice

Aim: Respiratory viral infections have been shown to exacerbate asthma. We have previously shown, in mice, that influenza infection increases serum IgE to house dust mite (HDM) via disruption of the epithelial barrier in vivo. In this study, we aimed to assess the effects of influenza infection on allergic airways disease development in pre-sensitized individuals, and secondly to assess whether these responses were allergen specific.

Methods: Adult female BALB/c mice were sensitized with OVA/alum on d0 and infected with 104.5pfu of influenza A/Mem/71 (or control) on d7. Mice received a second OVA/alum sensitization on d14 followed by challenge with 1% ovalbumin, 100 μg HDM protein or 1% saline. 24 hours later we assessed responsiveness to methacholine using the forced oscillation technique, serum antibodies and bronchoalveolar inflammation.

Results: Inflammation due to influenza infection had completely resolved by the day of study. Mice previously infected with influenza and challenged with OVA were the most responsive to MCh in terms of airway resistance, followed by mice challenged with HDM (regardless of infection). OVA challenged mice had the greatest BAL eosinophilia (regardless of infection). HDM challenged mice had the greatest total BAL cellular inflammation which was almost entirely neutrophilic.

Conclusion: Influenza induced the greatest increase in airway resistance and BAL eosinophilia in OVA sensitized and challenged mice. Infection with influenza had no additive effect on responsiveness to MCh in mice sensitized with OVA/alum and challenged with HDM protein. These findings supporting the notion that respiratory viral infection can lead to a more severe asthmatic phenotype in pre-sensitized individuals, and that these responses are allergenspecific.