Effects of various respiratory viruses on der f-sensitized mouse model of asthma

Purpose: Respiratory viral infection is the main cause of acute asthma exacerbation in children and can be a confirmed viral infection in 85% of children who visit a hospital because of asthma exacerbation. Viruses related to acute asthma exacerbation are rhinovirus (RV), respiratory syncytial virus (RSV), parainfluenza virus (PIV), human metapneumovirus (hMPV) and influenza virus. Among the viruses, RV is the most well-known frequent cause virus of acute asthma exacerbation for children 2 years or more. Some in vitro studies showed the immunologic responses after RV infection were different from other respiratory viruses. This may refer that the response to RV infection can be different to other respiratory viruses in patients with asthma. In this experiment, we determined cell counts and the level of cytokines in bronchoalveolar lavage fluid (BALF) of asthma mouse model after being infected by RV, RSV, or influenza virus in order to evaluate that there are differences in the kind of virus.

Methods: Asthma mouse model is made by sensitizing BALB/c mouse to house dust allergen Der f. The asthma mouse model is confirmed by measuring the airway resistance caused by methacholin inhalation, the eosinophil counts, interleukin (IL)-4, IL-5 and IL-13 in BALF, and by observing peribronchial eosinophilic inflammation of lung tissue through a microscope. After the prepared asthma mouse model is infected by RV, RSV, and the influenza virus respectively, the RT-PCR is used to confirm the existence of virus genes in lung tissue. We determined the number of eosinophils, neutrophils, lymphocytes and macrophages in BALF and measured RANTES and INF-γ in BALF of the mice infected by the viruses.

Results In the case of the Der f-sensitized mouse model with RV infection, the airway resistance and eosinophil counts in BALF increased, and INF-γ level did not increase by the virus. These findings were different from in the case of RSV or influenza virus infection.

Conclusion: In the case of infecting a respiratory virus to the developed asthma mouse model with the sensitized house dust mite allergen, increased airway resistance and eosinophilic inflammation with no increase in Th1 response were shown only with RV. These findings can be related to the phenomenon that RV is most frequently found to be the cause of acute asthma exacerbation.