Abstract
Having asthma increases the chance of hospitalisation following influenza infection. Inhaled steroids reduce asthma symptoms but could impair anti-viral responses.
Our aim was to compare the effects of ex vivo influenza infection in bronchial tissues of asthmatic individuals and healthy subjects.
Bronchial explants obtained by bronchoscopy from 10 healthy subjects and 10 mild/moderate asthmatics on chronic inhaled steroids (ICS) were infected with influenza virus in the absence/presence of exogenous steroid (fluticasone propionate, FP). Epithelial infection, viral shedding and inflammatory mediator production (IFN-γ, IL-6, IL-8, MCP-1, MIP-1β, TNF-α and IL-1β) by the biopsies were compared. Statistical comparisons were by unpaired or paired tests as appropriate.
Influenza infection rates were unchanged in the primary comparison of FP-treated biopsies from asthmatics compared to healthy subjects (mean % infection 32.6±4.2 vs.31.5±3.6 respectively, p=NS), but viral shedding (Log10 pfu/ml 5.06±0.141 vs. 5.62±0.113 , p<0.01) and all inflammatory mediators (p<0.05) were reduced in asthmatics.
Exogenous FP increased infection in the biopsies (mean % infection 31.5±3.6 vs. 40.4±3.7, p<0.05), and reduced all of the inflammatory mediators (p<0.05), but had no effect on viral shedding in healthy subjects (mean Log10 pfu/ml 5.62±0.11 vs. 5.63±0.13, p=NS).
Bronchial tissue of asthmatic subjects on ICS is not more susceptible to influenza infection than that from healthy individuals, but demonstrates reduced inflammatory mediator production and viral shedding. This could delay the cellular and humoral antiviral response thereby prolonging infections and contributing to exacerbations.
- Copyright ©ERS 2015