TLR3, TLR4 and TLRs7-9 Induced Interferons Are Not Impaired in Airway and Blood Cells in Well Controlled Asthma.

Annemarie Sykes,Onn Min Kon,Mark Mchale,Vera Gielen,Jennifer Haas,Jonathan Macintyre,Michael R Edwards,Ajerico Del Rosario,Sebastian L Johnston

doi:10.1371/journal.pone.0065921

Abstract

Defective Rhinovirus induced interferon-β and interferon-λ production has been reported in bronchial epithelial cells from asthmatics but the mechanisms of defective interferon induction in asthma are unknown. Virus infection can induce interferon through Toll like Receptors (TLR)3, TLR7 and TLR8. The role of these TLRs in interferon induction in asthma is unclear. This objective of this study was to measure the type I and III interferon response to TLR in bronchial epithelial cells and peripheral blood cells from atopic asthmatics and non-atopic non-asthmatics. Bronchial epithelial cells and peripheral blood mononuclear cells from atopic asthmatic and non-atopic non-asthmatic subjects were stimulated with agonists to TLR3, TLR4 & TLRs7–9 and type I and III interferon and pro-inflammatory cytokine, interleukin(IL)-6 and IL-8, responses assessed. mRNA expression was analysed by qPCR. Interferon proteins were analysed by ELISA. Pro-inflammatory cytokines were induced by each TLR ligand in both cell types. Ligands to TLR3 and TLR7/8, but not other TLRs, induced interferon-β and interferon-λ in bronchial epithelial cells. The ligand to TLR7/8, but not those to other TLRs, induced only type I interferons in peripheral blood mononuclear cells. No difference was observed in TLR induced interferon or pro-inflammatory cytokine production between asthmatic and non-asthmatic subjects from either cell type. TLR3 and TLR7/8,, stimulation induced interferon in bronchial epithelial cells and peripheral blood mononuclear cells. Interferon induction to TLR agonists was not observed to be different in asthmatics and non-asthmatics.

Highlights

Asthma exacerbations are an important cause of morbidity, mortality and health care costs [1]
We have previously reported RIG-I, MDA5 and TLR3 mediate rhinovirus induction of IFNs in primary human bronchial epithelial cells (BECs) from healthy subjects [14] and that in bronchoalveolar lavage (BAL) cells from asthmatics demonstrating deficient rhinovirus induced type I IFN production, TLR3, RIG-I and MDA5 expression was not different from non-asthmatics [8]
To assess which Toll like Receptors (TLR) were important in IFN induction in bronchial epithelial cells, BECs were stimulated with agonists to TLR3, TLR4 (LPS), TLR7/8 (R848), TLR8 (RNA40 complexed with DOTAP) and TLR9 (CpG-B-ODN and CPG-C-ODN) and supernatants and cells were harvested after 8 and 24 hrs

Summary

Introduction

Asthma exacerbations are an important cause of morbidity, mortality and health care costs [1]. Virus infection results in induction of antiviral interferons (IFNs), including type I: IFN-a and IFN-b and type III: IFN-l1 and IFN-l2/3, from airway cells [4] and defective rhinovirus induced IFN production has been identified in bronchial epithelial cells (BECs) [5,6,7], bronchoalveolar lavage (BAL) cells [5,8] and peripheral blood mononuclear cells (PBMCs) [9] from asthmatic subjects. The mechanisms causing this impaired IFN induction in cells from asthmatic subjects are unknown. TLR3, TLR7 and TLR8 have been implicated in responses to virus infection in animal models [16], TLR3 through recognition of dsRNA [12] and TLR7 and TLR8 through recognition of ssRNA and small nucleoside analogues [17]

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Results

Conclusion