IL-25 Inhibits Airway Anti-Viral Immunity and Promotes Virus Exacerbation of Allergic Airways Disease

Rationale We have previously reported blocking the IL-25 receptor (IL-17RB) prevented viral increased allergic airways inflammation and this was associated with reduced lung viral load. To investigate IL-25 regulation of airway anti-viral immunity we hypothesised that IL-25 directly inhibits airway epithelial cell (AEC) type I/III interferon expression and antibody blockade of IL-25 in vivo boosts lung interferon expression and reduces lung viral load in parallel with reduced type 2 airway inflammation. Methods In vitro Immunofluorescence was used to visualise epithelial IL-25 and IL- 17RB proteins in endobronchial biopsies from patients with asthma and healthy subjects and in AEC differentiated at ALI. AEC from n = 14 donors with asthma were differentiated at the air-liquid interface (ALI) and infected with RV-A1, MOI=0.1. A subset of AECs was treated with anti-IL-25 mAb (LNR125) before infecting with RV-A1 or human coronavirus 229E. Differentiated AEC from healthy donors were treated with recombinant IL-25 protein and infected with RV-A1. Nanostring immune transcriptomic data expressed as digital mRNA counts for exact copy number or was expressed as log2 fold change ratio against -log10 Bejamini-Yekutieli-corrected p-values. In vivo 6- 8-week-old, BALB/c mice sensitised and intranasally challenged daily for 3 days with ovalbumin to induced allergic airways disease. A single subcutaneous injection of 250 μg LNR125 was administered during ovalbumin challenge. Mice were then infected i.n. with RV-A1, 6 hours after final allergen challenge. On day 1 and day 7 post-infection, BAL were collected, lung lobe tissue was collected for viral RNA and cytokine expression. Results IL-25 and IL-17RB were constitutively expressed at the apical surface of airway epithelium in biopsies and AEC cultures. RV infection increased IL-25 expression by AEC from asthmatic donors. LNR125 treatment reduced IL-25 mRNA and significantly increased RV induced IFN-β a and IFN-λ protein expression and this was confirmed by Nanostring transcriptomic analyses which also identified down-regulated type-2 immune genes CCL26 (eotaxin 3) and IL1RL1(IL-33 receptor). LN125 treatment also increased IFN-λ expression by 229E-infected differentiated AECs. IL-25 treatment increased viral load associated with 50% reduced expression of IFN-β and CXCL10 and 75% reduced IFN-λ. Allergen challenged, RV-infected mice treated with LNR125 had significantly increased BAL IFN-β protein and 60% reduction in lung viral load associated with reduced IL-25, IL-4, IL-5 and IL-13 BAL proteins compared to controls. Conclusion IL-25-induced inflammation combined with suppression of AEC anti-viral immunity identify IL-25 as a central mediator of viral asthma exacerbations and therefore a target for mAb-based treatment.