Glucocorticoids impair type I IFN signalling and enhance rhinovirus replication.

Inhaled corticosteroids (ICS) are recommended treatments for all degrees of asthma severity and in combination with bronchodilators are indicated for COPD patients with a history of frequent exacerbations. However, the long-term side effects of glucocorticoids (GCs) may include increased risk of respiratory infections, including viral triggered exacerbations. Rhinovirus (RV) infection is the main trigger of asthma and COPD exacerbations. Thus, we sought to explore the influence of GCs on viral replication. We demonstrate the ICS fluticasone propionate (FP) and two selective non-steroidal (GRT7) and steroidal (GRT10) glucocorticoid receptor (GR) agonists significantly suppress pro-inflammatory (IL-6 and IL-8) and antiviral (IFN-λ1) cytokine production and the expression of the interferon-stimulated genes (ISGs) OAS and viperin in RV-infected bronchial epithelial cells, with a consequent increase of viral replication. We also show that FP, GRT7 and GRT10 inhibit STAT1 Y701 and/or STAT2 Y690 phosphorylation and ISG mRNA induction following cell stimulation with recombinant IFN-ß. In addition, we investigated the effects of the ICS budesonide (BD) and the long-acting ß2 agonist (LABA) formoterol, alone or as an ICS/LABA combination, on RV-induced ISG expression and viral replication. Combination of BD/formoterol increases the suppression of OAS and viperin mRNA observed with both BD and formoterol alone, but an increase in viral RNA was only observed with BD treatment and not with formoterol. Overall, we provide evidence of an impairment of the innate antiviral immune response by GC therapy and the potential for GCs to enhance viral replication. These findings could have important clinical implications.

Corticosteroid suppression of antiviral immunity increases bacterial loads and mucus production in COPD exacerbations.

Inhaled corticosteroids (ICS) have limited efficacy in reducing chronic obstructive pulmonary disease (COPD) exacerbations and increase pneumonia risk, through unknown mechanisms. Rhinoviruses precipitate most exacerbations and increase susceptibility to secondary bacterial infections. Here, we show that the ICS fluticasone propionate (FP) impairs innate and acquired antiviral immune responses leading to delayed virus clearance and previously unrecognised adverse effects of enhanced mucus, impaired antimicrobial peptide secretion and increased pulmonary bacterial load during virus-induced exacerbations. Exogenous interferon-ß reverses these effects. FP suppression of interferon may occur through inhibition of TLR3- and RIG-I virus-sensing pathways. Mice deficient in the type I interferon-α/ß receptor (IFNAR1-/-) have suppressed antimicrobial peptide and enhanced mucin responses to rhinovirus infection. This study identifies type I interferon as a central regulator of antibacterial immunity and mucus production. Suppression of interferon by ICS during virus-induced COPD exacerbations likely mediates pneumonia risk and raises suggestion that inhaled interferon-ß therapy may protect.

Long-term effects of inhaled corticosteroids on sputum bacterial and viral loads in COPD.

Inhaled corticosteroid-containing medications reduce the frequency of COPD exacerbations (mainly infectious in origin) while paradoxically increasing the risk of other respiratory infections. The aim was to determine the effects of inhaled corticosteroids on airway microbial load in COPD patients and evaluate the influence of the underlying inflammatory profile on airway colonisation and microbiome.This is a proof-of-concept prospective, randomised, open-label, blinded endpoint study. Sixty patients with stable moderate COPD were randomised to receive one inhalation twice daily of either a combination of salmeterol 50 µg plus fluticasone propionate 500 µg or salmeterol 50 µg for 12 months. The primary outcome was the change of sputum bacterial loads over the course of treatment.Compared with salmeterol, 1-year treatment with salmeterol plus fluticasone was associated with a significant increase in sputum bacterial load (p=0.005), modification of sputum microbial composition and increased airway load of potentially pathogenic bacteria. The increased bacterial load was observed only in inhaled corticosteroid-treated patients with lower baseline sputum or blood eosinophil (≤2%) levels but not in patients with higher baseline eosinophils.Long-term inhaled corticosteroid treatment affects bacterial load in stable COPD. Lower eosinophil counts are associated with increased airway bacterial load.