title: Vitamin D and allergic airway disease shape the murine lung microbiome in a sex-specific manner.
abstract: BACKGROUND
  Vitamin D is under scrutiny as a potential regulator of the development of respiratory diseases characterised by chronic lung inflammation, including asthma and chronic obstructive pulmonary disease. It has anti-inflammatory effects; however, knowledge around the relationship between dietary vitamin D, inflammation and the microbiome in the lungs is limited. In our previous studies, we observed more inflammatory cells in the bronchoalveolar lavage fluid and increased bacterial load in the lungs of vitamin D-deficient male mice with allergic airway disease, suggesting that vitamin D might modulate the lung microbiome. In the current study, we examined in more depth the effects of vitamin D deficiency initiated early in life, and subsequent supplementation with dietary vitamin D on the composition of the lung microbiome and the extent of respiratory inflammation.
  
  
  METHODS
  BALB/c dams were fed a vitamin D-supplemented or -deficient diet throughout gestation and lactation, with offspring continued on this diet post-natally. Some initially deficient offspring were fed a supplemented diet from 8 weeks of age. The lungs of naïve adult male and female offspring were compared prior to the induction of allergic airway disease. In further experiments, offspring were sensitised and boosted with the experimental allergen, ovalbumin (OVA), and T helper type 2-skewing adjuvant, aluminium hydroxide, followed by a single respiratory challenge with OVA.
  
  
  RESULTS
  In mice fed a vitamin D-containing diet throughout life, a sex difference in the lung microbial community was observed, with increased levels of an Acinetobacter operational taxonomic unit (OTU) in female lungs compared to male lungs. This effect was not observed in vitamin D-deficient mice or initially deficient mice supplemented with vitamin D from early adulthood. In addition, serum 25-hydroxyvitamin D levels inversely correlated with total bacterial OTUs, and Pseudomonas OTUs in the lungs. Increased levels of the antimicrobial murine ß-defensin-2 were detected in the bronchoalveolar lavage fluid of male and female mice fed a vitamin D-containing diet. The induction of OVA-induced allergic airway disease itself had a profound affect on the OTUs identified in the lung microbiome, which was accompanied by substantially more respiratory inflammation than that induced by vitamin D deficiency alone.
  
  
  CONCLUSIONS
  These data support the notion that maintaining sufficient vitamin D is necessary for optimal lung health, and that vitamin D may modulate the lung microbiome in a sex-specific fashion. Furthermore, our data suggest that the magnitude of the pro-inflammatory and microbiome-modifying effects of vitamin D deficiency were substantially less than that of allergic airway disease, and that there is an important interplay between respiratory inflammation and the lung microbiome.
authors.affiliation: Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Roggenbuck
authors.affiliation: Telethon Kids Institute, University of Western Australia, 100 Roberts Rd, Subiaco, WA, 6008, Australia.
authors.forename: Denise
authors.initials: D
authors.lastname: Anderson
authors.affiliation: The National Research Centre for the Working Environment, Copenhagen, Denmark.
authors.forename: Kenneth Klingenberg
authors.initials: KK
authors.lastname: Barfod
authors.affiliation: Clinical and Experimental Sciences, Faculty of Medicine, University of Southampton, Southampton General Hospital, Southampton, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Feelisch
authors.affiliation: Telethon Kids Institute, University of Western Australia, 100 Roberts Rd, Subiaco, WA, 6008, Australia.
authors.forename: Sian
authors.initials: S
authors.lastname: Geldenhuys
authors.affiliation: Section of Microbiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Søren J
authors.initials: SJ
authors.lastname: Sørensen
authors.affiliation: Telethon Kids Institute, University of Western Australia, 100 Roberts Rd, Subiaco, WA, 6008, Australia.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Weeden
authors.affiliation: Telethon Kids Institute, University of Western Australia, 100 Roberts Rd, Subiaco, WA, 6008, Australia.
authors.forename: Prue H
authors.initials: PH
authors.lastname: Hart
authors.affiliation: Telethon Kids Institute, University of Western Australia, 100 Roberts Rd, Subiaco, WA, 6008, Australia. shelley.gorman@telethonkids.org.au.
authors.forename: Shelley
authors.initials: S
authors.lastname: Gorman
keywords: Acinetobacter; Allergic airway disease; Inflammation; Lung; Microbiome; Sex differences; Vitamin D