Exacerbation of influenza infection by low doses of geogenic dust

Aim: To determine the effects of geogenic (earth-derived) PM10 (particulate matter <10 μm diameter) on pulmonary infl ammation and lung mechanics, and how this contributes to the exacerbation of a respiratory viral infection. Methods: Geogenic dust was directly sampled from the community of Karratha in the north of Western Australia, and the PM10 fraction was extracted. Adult female BALB/c mice were exposed to low doses of PM10 (10 μg per day for 10 days) by intranasal instillation (in 50 μL of saline + 0.05% Tween-80), while control mice received vehicle alone. Mice were infected with infl uenza (A/Mem/1/71) virus (or control VP-SFM media alone) at day 6, with lung function measured on day 11. Lung volume and mechanics were measured using plethysmography and a modifi cation of the forced oscillation technique (FOT). Mice were euthanased and bronchoalveolar lavage fl uid was collected for assessment of infl ammation (total and differential cell counts). Results: Infl uenza infection induced an infl ammatory response in the lung (infl ux of total infl ammatory cells p < 0.001; neutrophils p < 0.001). Geogenic PM10 from Karratha produced an additive effect on the infl ammatory response to infl uenza, with mice exposed to both having signifi cantly higher neutrophilia compared to those exposed to either insult alone (p = 0.003). Particle exposure signifi cantly impaired lung mechanics, with an increase in airway resistance (Raw, p < 0.001). Furthermore, exposure to PM10 synergistically impaired lung function during infl uenza infection (Raw, p < 0.001). Conclusion: Geogenic dust particles impair lung function and exacerbate the response to respiratory viral infection. This has important implications for respiratory health in communities exposed to high particulate loads of geogenic origin, such as those in the remote, arid regions of Australia.