Microbiome and mycobiome interaction in house dust mites and impact on airway cells

Background: Major allergen sources Dermatophagoides farinae, Dermatophagoides pteronyssinus and Tyrophagus putrescentiae have been reported to have distinct microbiomes. The purpose of this study was to investigate the effect of each mite on airway epithelial cells as a model of airway allergic disease. Methods: Transcriptomic analysis (RNA-seq) of an airway epithelial cell line (BEAS-2B) was performed to compare gene expression patterns after treatment with extracts of three mite species (D. farinae, D. pteronyssinus and T. putrescentiae). In addition, mycobiome deep sequencing of mites was employed to identify fungal species that interact with the microbiomes of the mites. Results: Immune responses to bacteria were enriched only in the D. farinae-treated group as this species harboured larger numbers of bacteria than the other mites, and the high level of LPS in D. farinae caused proinflammatory cytokine production in airway epithelial cells. In addition, antibiotic metabolism pathways were enriched in D. pteronyssinus-treated cells but not in D. farinae -treated cells. Subsequent experiments revealed that D. pteronyssinus had a high fungal load that inhibited bacterial survival in this mite species. Conclusion: The large amount of bacteria in D. farinae causes airway epithelial cells to produce more allergy-related cytokines than D. pteronyssinus, since fungi present in D. pteronyssinus suppress the abundance of mite-associated bacteria.