Geogenic PM10 exposure exacerbates responses to influenza infection

Particulate matter (PM) exposure has been linked epidemiologically to exacerbations of lung disease, including respiratory infections. We investigated the effects of geogenic (earth-derived) PM₁₀ (PM < 10 μm diameter) on the response to a respiratory viral infection.

Geogenic dust was sampled from four communities in arid environments in Western Australia. Adult female BALB/c mice were intranasally exposed to chronic doses of PM₁₀ (10 μg/day for 10 days), and/or infected with influenza (A/Mem/1/71) virus. Inflammation (cells, IL-6, IFN-γ) was measured in bronchoalveolar lavage. Lung mechanics were measured using the forced oscillation technique.

Geogenic PM₁₀ induced lung inflammation (neutrophils, macrophages) with additive effects in mice also infected with influenza. PM₁₀ also modified the influenza-induced IL-6 and IFN-γ responses. Geogenic PM₁₀ increased airway resistance, and increased hysteresivity in those exposed to both insults. Viral titres were significantly higher after PM₁₀ exposure. Iron concentration was inversely associated with IFN-γ and positively associated with viral titre and hysteresivity.

Geogenic PM₁₀ exposure increases inflammation, impairs lung function and increases viral load, exacerbating the response to respiratory viral infection. Iron in the particles may be a driver of these responses. This has important implications for respiratory health in communities exposed to high geogenic PM₁₀, such as those in arid environments.