Phenotype and severity of asthma determines bronchial epithelial immune
responses to a TLR3 agonist
Abstract
Background Asthma is characterized by an aggravated immune
response to respiratory viral infections: This phenomenon is a
clinically well-recognized driver of acute exacerbations, but how
different phenotypes of asthma respond immunologically to virus is
unclear. Objectives To describe the association between
different phenotypes and severity of asthma and bronchial epithelial
immune responses to viral stimulation. Methods In the
Immunoreact study, healthy subjects (n=10) and 50 patients with asthma
were included; 30 (60%) were atopic, and 34 (68%) were eosinophilic;
15 (25%) had severe asthma. All participants underwent bronchoscopy
with collection of bronchial brushings. Bronchial epithelial cells
(BECs) were expanded and stimulated with the viral replication mimic
poly (I:C) (TLR3 agonist) in vitro. The expression of
TLR3-induced pro-inflammatory and anti-viral responses of BECs were
analyzed using RT-qPCR and multiplex ELISA and compared across asthma
phenotypes and severity of disease. Results Patients with
atopic asthma had increased production of IL-4, IFN-β, IL-6, TNF-α, and
IL-1β after poly (I:C) stimulation compared to non-atopic patients,
whereas patients with eosinophilic asthma and non-eosinophilic asthma
did not differ in the response to poly (I:C). Patients with severe
asthma displayed a decreased antiviral IFN-β, and increased expression
of IL-8, most pronounced in atopic and eosinophilic asthmatics.
Interestingly, release of IL-33 and TSLP in response to poly (I:C) was
increased in severe eosinophilic asthma, but not in severe atopic
asthma. Conclusions The bronchial epithelial immune response to
a viral mimic stimulation differs between asthma phenotypes and
severities, which may be important to consider when targeting novel
asthma treatments.