Exacerbation Of A Respiratory Viral Infection By Low Doses Of Geogenic Dust

Rationale: Environmental particulate matter (PM) exposure has been linked epidemiologically to exacerbations of lung disease. However, most studies have concentrated on the effects of urban PM. The effects of geogenic (earth-derived) PM (PM <10µm in 10 diameter) on the lung are not known. We aimed to determine the specific effects of geogenic dust PM on pulmonary 10 inflammation 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 PM (10µg per day for 10 days) by intranasal 10 instillation (in 50µL of saline + 0.05% Tween-80), while control mice received vehicle alone. Mice were infected with influenza (A/Mem/1/71) virus (or control media alone) at day 6, with lung function measured on day 11. Lung volume and mechanics were measured using plethysmography and a modification of the forced oscillation technique (FOT). Bronchoalveolar lavage fluid was collected for assessment of inflammation.

Results: s Influenza infection induced an inflammatory response in the lung (influx of total inflammatory cells p<0.001; neutrophils p<0.001). Geogenic PM from Karratha produced an additive effect on the inflammatory response to influenza, with mice 10 exposed to both having significantly higher neutrophilia compared to those exposed to either insult alone (p=0.003). Particle exposure significantly impaired lung mechanics, with an increase in airway resistance (R , p<0.001). Furthermore, exposure to aw PM synergistically worsened lung function during influenza infection (R , p<0.001).

Conclusions: Geogenic dust particles impair lung function and exacerbate the response to respiratory viral infection. These effects appear to exceed those induced by urban PM. This has important implications for respiratory health in communities exposed to high particulate loads of geogenic origin, such as those in remote, arid environments.