Ultraviolet irradiation and the home microbiome in childhood asthma: An exploratory environmental analysis.

Abstract

Background: Ultraviolet (UV) filtration units installed into central heating, ventilation, and air conditioning systems have been shown to modify indoor environmental microbiomes (EM), but it remains unclear whether central UV air filtration systems as a targeted intervention alters the EM sufficiently to modify asthma outcomes. Objective: The objective was to investigate changes in the microbiome from dust samples collected before and after installation of a central UV filtration system in homes of children with mild-moderate persistent asthma. Methods: Enrolled pediatric subjects with asthma were randomized to receive UV filtration or sham devices in their heating, ventilation, and air conditioning units. Dust samples were collected from the furnace filters and each child's bedroom inflow air ducts from the first 20 homes randomized at the two largest recruiting sites at the time of device placement and at study completion (12 months), along with periodic measurements of asthma outcomes markers by using the Composite Asthma Severity Index. Microbial DNA from each paired dust sample underwent shotgun metagenomic sequencing, and taxonomic profiles were generated with MetaPhlAn 4. Associations between changes in bacterial species abundance and changes in asthma severity were assessed with Microbiome Multivariable Associations with Linear Models in R. Results: A total of 14 paired dust samples (7 from the UV homes and 7 from the sham homes) from inflow air ducts with sufficient quantity of dust were included for EM analysis. Within the UV filtration homes, false discovery rate adjusted q-values < 0.05 identified associations between worsening asthma severity and reduced relative abundance of common gastrointestinal commensals, such as Bacteroides and Bifidobacterium, previously linked to a reduced risk of allergic disease and asthma; no associations at this threshold were observed in the sham homes. Conclusion: An exploratory study of UV air filtration units installed in homes of children with asthma identified hypothesis-generating associations between bacterial species changes and asthma severity; because the study was underpowered for between-arm comparisons, these findings do not establish that UV air filtration caused the microbiome changes and should not be interpreted as confirmatory of a UV-specific effect.Clinical trial NCT02715375, www.clinicaltrials.gov.