Microbiome composition of airborne particulate matter from livestock farms and their effect on innate immune receptors and cells

Patients with respiratory diseases in rural areas have been reported to have enhanced responsiveness to ambient particulate matter (PM). In addition to the physical and chemical components, ambient PM can contain microorganisms or parts thereof, referred here as BioPM, that can also contribute to the adverse health effects. This study aimed to characterize the microbial composition of BioPM originating from livestock, and to investigate whether these BioPM can trigger the activation of innate receptors and cells. Coarse (PM_2.5–10 μm) and fine (PM_<2.5 μm) BioPM samples were collected from indoor chicken, pig and goat farms using the versatile aerosol concentration enrichment system (VACES) connected to a Biosampler. The fungal and bacterial communities were assessed with an amplicon based approach using Next Generation Sequencing (NGS). In parallel, HEK-Blue cells expressing different pattern recognition receptors (Toll like receptors (TLR) 2, 3, 4, 5, 7, 8, 9 and NOD 1, 2) and a human monocytic cell line (MM6) were exposed to BioPM samples from these sites. Distinct airborne microbiota profiles associated with the corresponding animal farm were observed. Moreover, the various BioPM contained mainly ligands for TLR2 and TLR4 resulting in a concentration-dependent increase of pro-inflammatory cytokine secreted by MM6 cells. In addition, we show for the first time that only the pig-derived BioPM induced TLR5 activation. These findings suggest that animal farm specific BioPM trigger distinct inflammatory responses, which may contribute to airway diseases in humans.