To the editor, Patients with severe eosinophilic asthma have a high risk of exacerbations requiring rescue oral corticosteroid treatment. Monoclonal antibody treatments inhibiting IL-5 directly or via the IL-5Rα or IL13/IL4 via the IL-4Rα reduce exacerbations of severe, eosinophilic asthma with evidence to type-2 inflammation as shown by a raised peripheral blood eosinophil count or fractional exhaled nitric oxide (FeNO) (1) (2). Both of these biomarkers have been associated with an increased risk of exacerbations (3).The key cytokine for the development of eosinophils is IL-5 whereas FENO is regulated by the IL-13 dependant inducible nitric oxide pathway (4) suggesting that their combination might provide additive prognostic and predictive information. We tested this hypothesis in a post-hoc analysis of a placebo controlled trial of anti-IL-5 (mepolizumab) in patients with severe asthma. MethodsWe undertook a post-hoc analysis of a phase 2b study of mepolizumab in patients with severe eosinophilic asthma (DREAM) (1). We selected this study as it was the only mepolizumab study to assess FeNO and blood eosinophils at baseline. DREAM evaluated placebo and 3 doses of mepolizumab (75 mg, 250 mg, 750 mg IV 4 weekly) for 52 weeks. Participants had a history of 2 or more exacerbations requiring oral corticosteroids in the previous year and evidence of eosinophilic inflammation as reflected by one of more of the following: a peripheral blood eosinophil count ≥300 cells/µL; a sputum eosinophil count ≥3%; FeNO ≥50ppb; and prompt deterioration of asthma control after a 25% or less reduction in regular maintenance inhaled or oral corticosteroids. As the DREAM study did not show a dose-related effect of active treatment or evidence of an interaction between dose and predictive value of biomarkers, our analysis is based on the combined effect of the different doses.

Background: Whether blood eosinophil counts and exhaled nitric oxide (FeNO) are associated with important outcomes in mild asthma is unclear. Methods: This question was explored in a pre-specified analysis of a 52week, open-label, randomized, parallel-group trial in patients with mild asthma receiving only reliever inhalers, comparing salbutamol 200µg asneeded, maintenance budesonide 200µg twice-daily with salbutamol as needed, and budesonide/formoterol 200/6µg as-needed. Outcomes were compared between patients with blood eosinophils of <0.15, 0.15-<0.3 and ≥0.3x109/L; FeNO of <20, 20-50 and >50ppb; and a composite score based on both. Results: The proportion of patients randomised to as-needed salbutamol having a severe exacerbation increased progressively with increasing blood eosinophil sub-group (4.1%, 6.5% and 19.5%; p=0.014). There were no significant interactions between either biomarker and the effect of as-needed budesonide/formoterol compared with as-needed salbutamol for either exacerbations or severe exacerbations. However, there were significant interactions between blood eosinophil sub-groups and the effect of maintenance budesonide compared with as needed salbutamol for exacerbations (p<0.001) and severe exacerbations (p<0.001). Maintenance budesonide was more effective than as-needed salbutamol in patients with eosinophils ≥0.3x109/L for exacerbations (odds ratio 0.13; 95% CI 0.05-0.33) and severe exacerbations (0.11; 0.03-0.45). This was not the case for eosinophils <0.15x109/L (odds ratio for exacerbations 1.15; 0.51-1.28 and severe exacerbations 5.72; 0.97-33.6). There was no consistent interaction between treatment response and FeNO or the composite score. Conclusions: In patients with mild asthma the effects of as-needed budesonide/formoterol on exacerbations are independent of biomarker profile, whereas the benefits of maintenance inhaled budesonide are greater in patients with high blood eosinophil counts.

The SARS-CoV-2 can lead to severe illness with COVID-19. Outcomes of patients requiring mechanical ventilation are poor. Awake proning in COVID-19 improves oxygenation, but on data clinical outcomes is limited. This single-centre retrospective study aimed to assess whether successful awake proning of patients with COVID-19, requiring respiratory support (continuous positive airways pressure (CPAP) or high-flow nasal oxygen (HFNO)) on a respiratory high-dependency unit (HDU), is associated with improved outcomes. HDU care included awake proning by respiratory physiotherapists. Of 565 patients admitted with COVID-19, 71 (12.6%) were managed on the respiratory HDU, with 48 of these (67.6%) requiring respiratory support. Patients managed with CPAP alone 22/48 (45.8%) were significantly less likely to die than patients who required transfer onto HFNO 26/48 (54.2%): CPAP mortality 36.4%; HFNO mortality 69.2%, (p=0.023); however, multivariate analysis demonstrated that increasing age and the inability to awake prone were the only independent predictors of COVID-19 mortality. The mortality of patients with COVID-19 requiring respiratory support is considerable. Data from our cohort managed on HDU show that CPAP and awake proning are possible in a selected population of COVID-19, and may be useful. Further prospective studies are required.

While there now exist effective treatments for type 2 high, eosinophilic asthma, there are no specific therapies for 40–50% of people with asthma with other phenotypes, which result from poorly understood underlying pathological mechanisms. One such pathology is neutrophilic inflammation, which has been associated with interleukin (IL)-17 family cytokines. Human genetic studies identified IL-17 polymorphisms associated with asthma; in murine models of allergic airways disease, IL-17A contributes to airway hyperresponsiveness, and in humans, elevated airway IL-17A levels are repeatedly observed in severe asthma. However, the directionality of this association is unknown, and the assumption that IL-17 cytokines drive disease pathology remains speculative. Here, we explore the evidence underlying the relationship between IL-17 and asthma, we review lessons learned from investigating IL-17 in other inflammatory diseases, and discuss the possibility that IL-17 may even be protective in asthma rather than pathogenic. We also critically examine the newly proposed paradigm of a reciprocal relationship between type 2 and type 17 airways inflammation. In summary, we suggest an association between IL-17 and asthma, but research is needed examining the diverse functions of these cytokines, their longitudinal stability, their response to clinical interventions, and for mechanistic studies determining whether they are protective or pathogenic.