Long Covid is a term used to describe a multisystem condition that presents with a myriad of physical and psychological symptoms that continue or develop after acute COVID-19. Long Covid is a significant public health problem because of the nature of the illness, its negative impfact on everyday functioning, and the healthcare inequalities evident in access and experience, notably in terms of ethnicity and socioeconomic status. Evidence in patients hospitalised with their acute infection suggests exercise-based rehabilitation could be helpful to improve exercise tolerance, respiratory symptoms, fatigue, and cognition; however, research is needed to determine whether exercise-based rehabilitation is effective and acceptable for patients with Long Covid who were not hospitalised. This mixed-methods study comprises a single-centre, randomised controlled trial to determine whether face-to-face rehabilitation increases exercise capacity compared to usual care alone in non-hospitalised patients with Long Covid, with embedded qualitative components to explore intervention acceptability in the context of healthcare inequalities. Usual care is as defined by the National Institute for Clinical Excellence (NICE) Covid-19 guidance. The rehabilitation intervention will take place twice a week for 6 weeks and will combine symptom-titrated exercise with self-management education. The proposed sample size of 56 for the randomised controlled trial is calculated on the primary outcome of Incremental Shuttle Walking Test (ISWT) distance, with a change of 50metres (m) at 90

Rationale Admission to hospital with an acute exacerbation of chronic obstructive pulmonary disease (AECOPD) is associated with a high risk of readmission and death. A proportion of patients with COPD have type 2 inflammation, as indicated by raised blood eosinophil count, for which targeted biologic treatment has been shown to reduce moderate, community-treated exacerbations. Mepolizumab is a monoclonal antibody to interleukin-5 which effectively reduces eosinophilic inflammation, but effects on future hospitalisations and mortality in COPD are uncertain. Methods COPD-HELP was a single-centre, phase IIb, double-blind, placebo-controlled study that randomised patients who were admitted to hospital with an acute exacerbation of COPD to either mepolizumab 100mg or placebo every 4 weeks for 48 weeks. All participants (≥40 years) had a blood eosinophil count of at least 300 cells per microlitre in the 12 months prior to admission, were established on inhaled corticosteroids at time of admission and alternative diagnoses or causes of eosinophilia were excluded. The primary end point was the time to readmission or death due to any cause. Key secondary endpoints included number of hospital readmissions, number of moderate or severe exacerbations, and health related quality of life. Results A total of 238 patients were randomised (119 in each group). The median time to rehospitalisation or death (all cause) was 25.4 weeks in the mepolizumab arm and 26.1 weeks in the placebo arm, with Kaplan-Meier estimates of 33.9% and 31.0% respectively (HR 0.96 (95%CI 0.7 to 1.32, p=0.811). The adjusted mean (95% CI) number of hospital readmissions over 48 weeks was 1.65 (1.25 to 2.05) with mepolizumab and 1.85 (1.42 to 2.29) with placebo (rate ratio [95% CI] 0.89 [0.64 to 1.25]). The adjusted mean (95% CI) number of moderate or severe exacerbations over 48 weeks was 2.80 (2.36 to 3.23) with mepolizumab and 3.45 (2.94 to 3.95) with placebo (rate ratio [95% CI] 0.81 [95% CI 0.66 to 1.00]). Conclusion Patients hospitalised with an acute exacerbation of COPD and evidence of eosinophilic inflammation had no benefit in risk of severe exacerbations or death when given mepolizumab for 48 weeks. A numerical reduction in the number of exacerbations was observed, consistent with previous trials.

Although CD20xCD3 bispecific antibodies (BsAbs) have demonstrated transformational activity in diffuse large B-cell lymphoma (DLBCL), some patients fail to respond and others relapse. To begin to explore possible limitations, we compared the in vitro activity of four CD20xCD3 biosimilar BsAbs against four DLBCL cell lines with CD20 expression ranging over a 100-fold. All four biosimilar BsAbs demonstrated superior in vitro activity to rituximab, with biosimilar glofitamab consistently being the most potent. Moreover, biosimilar glofitamab and odronextamab retained significant activity in the presence of low-level CD20 expression. Finally, one DLBCL cell line exhibited intrinsic resistance to all four CD20xCD3 BsAbs despite inducing marked T-cell and NK-cell activation.

Introduction Sub-optimal inhaler adherence undermines the efficacy of pharmacotherapy in COPD. Digitalised care pathways are increasingly used to improve inhaler-use behaviour remotely. This review investigated the feasibility and impact of remote electronic inhaler adherence monitoring (EIM) and intervention platforms on clinical outcomes in COPD. Methods A literature search was conducted and studies investigating maintenance inhaler use among people with COPD using digital technology were selected. Pairwise and proportional meta-analyses were employed with heterogeneity assessed using I2 statistics. When meta-analysis was not feasible, a narrative synthesis of outcomes was conducted. Results We included 10 studies including 1432 people with COPD whose maintenance inhaler usage was supported by digital inhalers and apps featuring audiovisual reminders and educational content with or without engagement with healthcare providers (HCPs). Inhaler adherence rate (AR) varied with calculation methods, but an overall suboptimal adherence was observed among people with COPD. HCP-led adherence interventions alongside EIM improved mean AR by 18% (95% CI 9–27) versus passive EIM only. Enhanced AR may reduce COPD-related healthcare utilisation with little impact on health-related quality of life and exacerbation rate. Despite encountering technical issues among 14% (95% CI 5–23%) of participants, 85% (95% CI 76–94%) found digital platforms convenient to use, while 91% (95% CI 79–100%) perceived inhaler reminders as helpful. Conclusion Digitalised interventions can enhance maintenance inhaler adherence in COPD but their overall effect on clinical outcomes remains uncertain. Further work is required to tailor interventions to individuals’ adherence behaviour and investigate their longer-term impact.

This study uncovered a reversal of seasonal variation in hospitalised COPD exacerbation events after the COVID-19 pandemic. Investigation of updated seasonal exacerbation patterns and triggers can help initiate preventive strategies effectively. https://bit.ly/3wN71h0.

Acute exacerbations of Chronic Obstructive Pulmonary Disease (AECOPD) are driven through different triggers, including infection such as viruses and bacteria. However, nearly 40% of exacerbations are associated with a blood eosinophilia and related to type 2 inflammation (T2High) [1]. Footnotes This manuscript has recently been accepted for publication in the European Respiratory Journal . It is published here in its accepted form prior to copyediting and typesetting by our production team. After these production processes are complete and the authors have approved the resulting proofs, the article will move to the latest issue of the ERJ online. Please open or download the PDF to view this article. Conflict of Interest: H. Aung, H. McAuley, K. Porter and M.Richardson have nothing to disclose Conflict of Interest: A. Wright's Institute have received grant income from Sanofi. Conflict of Interest: C.Brightling has received grants and consultancy fees from 4D Pharma, AstraZeneca, Chiesi, Genentech, GlaxoSmithKline, Mologic, Novartis, Regeneron Pharmaceuticals, Roche and Sanofi. Conflict of Interest: N.Greening has received honoraria for lectures, conference travel and advisory boards from AstraZeneca, Boehringer Ingelheim, Chiesi, GlaxoSmithKleine and Pulmonx. His institute have received grants and consultation fees from Genentech, Roche and GlaxoSmithKline.

Background: Astegolimab (anti-ST2/IL-33R) shows promise in reducing exacerbations & improving quality of life for a subset of moderate-severe COPD patients (n=81, NCT03615040). Our objective was to determine, concomitantly, the effect of astegolimab on blood leucocytes & proteins to identify IL-33-dependent pathways. Method: Blood was collected at 0 (randomisation), 4 & 12 weeks from a subset of patients (n=30 placebo/n=29 astegolimab) during clinical stability. Non-/T2 cells were measured by cytometry (cells/100μl) & raw data analysed longitudinally by mixed effects model (β, [95%CI], FDR adj. p) & by Kruskal-Wallis for cross-sectional comparisons. Serum proteins (n=1463) were measured by Olink in 79 patients at week -2 (screening), week 4 (n=37/n=42, respectively) and week 24 (n=35/n=40, respectively) & those that passed QC (n=639) were analysed using a linear mixed model (FDR adj. p). Results: Astegolimab, but not placebo, decreased eosinophils at week 4 (β=-0.58, [-0.86 to -0.31], p=0.0001) & week 12 (β=-0.83, [-1.13 to -0.53], p=2.0-7) vs week 0. Eosinophil levels in the astegolimab group were different from placebo at week 4 (p=0.04) & week 12 (p=0.002). Other leucocyte levels were not significantly altered by astegolimab compared to week 0. Of 639 serum proteins, only two were altered by astegolimab at week 4 & 24 vs week -2; soluble (s)ST2 (β=2.24, p=1.8x10-46 & β=2.27, p=2x10-46, respectively) & Charcot-Leiden Crystal (β=-0.49, p=0.01 & β=-0.47, p=0.016). Conclusion: Astegolimab strongly decreased blood eosinophils & an eosinophil-associated protein (CLC) but had negligible effect on other cells or proteins beyond its target, sST2.

Background Chronic obstructive pulmonary disease (COPD) is a heterogeneous inflammatory airway disease. The epithelial-derived IL-33 and its receptor ST2 have been implicated in airway inflammation and infection. We aimed to determine whether astegolimab, a selective ST2 IgG2 monoclonal antibody, reduces exacerbations in COPD. Methods COPD-ST2OP was a single-centre, randomised, double-blinded, placebo-controlled phase 2a trial in moderate-to-very severe COPD. Participants were randomly assigned (1:1) with a web-based system to received 490 mg subcutaneous astegolimab or subcutaneous placebo, every 4 weeks for 44 weeks. The primary endpoint was exacerbation rate assessed for 48 weeks assessed with a negative binomial count model in the intention-to-treat population, with prespecified subgroup analysis by baseline blood eosinophil count. The model was the number of exacerbations over the 48-week treatment period, with treatment group as a covariate. Safety was assessed in the whole study population until week 60. Secondary endpoints induded Saint George's Respiratory Questionnaire for COPD (SGRQ-C), FEV1, and blood and sputum cell counts. The trial was registered with ClinicalTrials.gov, NCT03615040. Findings The exacerbation rate at 48 weeks in the intention-to-treat analysis was not significantly different between the astegolimab group (2.18 [95% CI 1.59 to 2.78]) and the placebo group (2.81 [2.05 to 3.58]; rate ratio 0.78 [95% CI 0.53 to 1.14]; p=0-19]). In the prespecified analysis stratifying patients by blood eosinophil count, patients with 170 or fewer cells per pL had 0.69 exacerbations (0.39 to 1.21), whereas those with more than 170 cells per mu L had 0.83 exacerbations (0.49 to 1-40). For the secondary outcomes, the mean difference between the SGRQ-C in the astegolimab group versus placebo group was -3.3 (95% CI -6.4 to -0.2; p=0.039), and mean difference in FEV1 between the two groups was 40 mL (-10 to 90; 1:0-094). The difference in geometric mean ratios between the two groups for blood eosinophil counts was 0.59 (95% CI 0.51 to 0.69; p<0.001) and 0.25 (0.19 to 0.33; p<0.001) for sputum eosinophil counts. Incidence of treatment-emergent adverse events was similar between groups. Interpretation In patients with moderate-to-very severe COPD, astegolimab did not significantly reduce exacerbation rate, but did improve health status compared with placebo. Copyright Crown Copyright (C) 2022 Published by Elsevier Ltd. All rights reserved.

Background: Chronic obstructive pulmonary disease (COPD) is a heterogeneous inflammatory airways disease. The epithelial-derived ‘alarmin’ IL-33 and its receptor ST2 have been implicated in airway inflammation and infection. We sought to determine whether astegolimab, a selective ST2 IgG2 monoclonal antibody, reduces exacerbations in COPD. Methods: We undertook a single-centre, randomised, double-blinded, placebo-controlled, phase IIa trial in moderate-to-very severe COPD. Participants received astegolimab 490mg (n=42) or placebo (n=39), every 4 weeks over 44 weeks. Primary endpoint was exacerbation rate over 48 weeks with pre-specified subgroup analysis by baseline blood eosinophil count. Secondary endpoints included Saint George’s Respiratory Questionnaire for COPD (SGRQ-C), FEV1, blood and sputum cell counts, and safety and tolerability. Results: The 48-week exacerbation rate in the astegolimab group relative to placebo was 0.78 (0.53 -0 1.14; p=0.195) in the whole group and 0.69 (0.39 - 1.21) and 0.83 (0.49 - 1.40) in subjects below or above the median baseline blood eosinophil count (170 cells/µL). In the astegolimab group versus placebo the mean difference for SGRQ-C and FEV1 was –3.3 (-6.4 to -0.2; p=0.039) and 40ml (-10 to 90; p=0.094), respectively. The differences in geometric mean ratios for blood and sputum eosinophil counts were 0.59 (0.51 - 0.69; p<0.001) and 0.25 (0.19 - 0.33; p<0.001). Incidence of treatment-emergent adverse events was similar between groups. Conclusion: Astegolimab did not reduce 48-week COPD exacerbation rate significantly in the whole group, subgroup analyses suggested more benefit in subjects with lower blood eosinophil counts.

Background: Mepolizumab, a monoclonal antibody targeting IL-5, provides clinical benefit in severe asthmatics with a T2 inflammatory signature. Aims: To determine whether the clinical benefit of mepolizumab therapy in severe asthma was associated with functional changes in immune cells. Method: Peripheral blood mononuclear cells (PBMCs) were isolated from severe asthma patients (GINA 5) at the start of the mepolizumab therapy (visit 1), and 16 weeks (visit 2) into treatment. PBMCs were isolated and treated either with αCD28/CD3 or Lipopolysaccharide (LPS) alone or in the presence of 10-10 -10-6 M dexamethasone before levels of Th2 and Th17 cytokines, GM-CSF and TNFα were assessed by ELISA. Results: αCD28/CD3 significantly stimulated the production of IL-5 (362.3 ± 93.4 pg/ml, n=9), IL-17 (277.3 ± 62.06 pg/ml, n= 19), IL-13 (614.8 ± 106.6 pg/ml, n=20) and IL-10 (666.7 ± 92.6 pg/ml, n=11). Also, LPS was able to significantly induce the production of TNF-α (657.18 ± 90.9 pg/ml, n= 8) and GM-CSF (169.37 ± 38.3 pg/ml, n= 8). Dexamethasone (10-10-10-6M) dose-dependently inhibited of IL-5 (IC50= - 8.31, 76% of inhibition), IL-17 (IC50= -8.07, 63% of inhibition), GM-CSF (IC50= -7.88, 75% of inhibition) but had minimal effect on IL-13 and IL-10 production, respectively. Cytokine production induced by αCD28/CD3 or LPS and sensitivity to corticosteroids were not different in PBMCs between V1 and V2. Conclusions: Mepolizumab therapy for 16 weeks was not associated with changes in PBMCs’ responses to stimulation or sensitivity to dexamethasone. Changes on 52 weeks remain to be assessed.

The acute inflammatory response to active or passive activities that increase body temperature may aid to reduce chronic low-grade inflammation. This study investigates the impact of temperature and extracellular heat shock protein 72 (eHsp72) on the acute intracellular Hsp72 (iHsp72) and interleukin-6 (iIL-6) response in monocytes. Whole blood was incubated for 2 h at 37.0 °C, 38.5 °C and 40.0 °C, in the absence or presence of 0.5 μg/ml eHsp72. Flow cytometry was used to assess iHsp72 and iIL-6 expression in total monocytes and the three monocyte subsets. Incubation at 40.0 °C (p < 0.001) but not 38.5 °C (p = 0.085) increased iHsp72 expression when compared with 37.0 °C, while there was no effect of temperature on iIL-6 expression (p = 0.635). Following incubation with eHsp72, the expression of iHsp72 in classical monocytes was reduced at all temperatures (p < 0.001), while there was no effect of eHsp72 on iIL-6 expression (p = 0.071). Large temperature elevations are needed to induce an acute iHsp72 response in monocytes. In addition, contrary to its suggested role as a danger signal for the innate immune system, eHsp72 reduced iHsp72 and iIL-6 expression in monocytes.

The transient receptor potential cation channel family member ankyrin 1 (TRPA1) is a potential target for several diseases, but detection of human TRPA1 (hTRPA1) protein in cells and tissues is problematic as rigorous antibody validation is lacking. We expressed hTRPA1 in a TRPA1-negative cell line to evaluate 5 commercially available antibodies by western blotting, immunofluorescence, immunocytochemistry and flow cytometry. The three most cited anti-TRPA1 antibodies lacked sensitivity and/or specificity, but two mouse monoclonal anti-TRPA1 antibodies detected hTRPA1 specifically in the above assays. This enabled the development of a flow cytometry assay, which demonstrated strong expression of TRPA1 in human lung myofibroblasts, human airway smooth muscle cells but not lung mast cells. The most cited anti-TRPA1 antibodies lack sensitivity and/or specificity for hTRPA1. We have identified two anti-TRPA1 antibodies which detect hTRPA1 specifically. Previously published data regarding human TRPA1 protein expression may need revisiting.

To the Editor: Mepolizumab (anti-IL-5) depletes blood and airway eosinophils, and, clinically, allows down-titration of oral corticosteroid and a reduction in the frequency of eosinophil-dependent exacerbations.1 Basophils also express IL-5Rα, participate in T2-mediated inflammatory pathways2 and have been associated with exacerbation frequency.3 Whilst basophil progenitors are unlikely to depend on IL-5 for development,4 blood basophil counts measured in routine clinical laboratories suggest they decrease following mepolizumab treatment.5-8 Our primary objective was to determine whether anti-IL-5 monoclonal antibody treatment reduces blood basophil levels as an additional potential efficacy mechanism. To achieve this, we measured blood basophils, eosinophils and other type 2 inflammatory cells, before and after 16 weeks of mepolizumab ("Nucala," GlaxoSmithKline) by flow cytometry. Patient eligibility criteria are in the online supplement and the study schedule in Figure S1. Blood samples were obtained from 26 severe asthma subjects, attending a difficult asthma clinic at a single UK centre, at baseline and following a median (IQR) of 16 (16-17) weeks of mepolizumab, administered as a 100 mg subcutaneous injection every 4 weeks. In 2 cases, it was not possible to obtain post-treatment samples (n = 1, withdrew consent; n = 1, discontinued), totalling 24 (Figure S1 and Table S1). We also recruited 15 nonasthmatic healthy controls (Table S1) to obtain samples at parallel time points but without an intervention (Figure S1). Flow cytometric measurements were compared with data derived through the routine pathology service, which utilizes an ADVIA 2120/2120i analyser (Siemens, UK). A detailed description of the methodology for both approaches is described in the online supplement, and for flow cytometry, the gating strategy is shown in Figure S2. Our criteria for identifying cell subsets were as follows: eosinophils (CD45+CD3-CD193+CD294+SSChiCD123−/+), basophils (CD45+CD3-CD193+CD294+SSCloCD123+), cTH2 and peTH2 (both CD4+CD294+ but CD161− or +, respectively), cTC2 (CD8+CD294+) and ILC2s (Lineage−CD294+CD161+). For methodological comparisons, data from asthma and healthy subjects (n = 39) were pooled. A good correlation was observed between flow cytometry and the ADVIA 2120i for total cells (r2 = 0.24, P = 0.0014) and eosinophils (r2 = 0.75, P < 0.0001), but not basophils (r2 = 0.06, P = 0.13 Figure S3). In addition, the change in cell concentration between baseline and follow-up showed a good correlation between the two analytical methods for eosinophils (r2 = 0.72, P < 0.0001, n = 38) but not basophils (r2 = 0.02, P = 0.39, n = 38). As expected, following 16 weeks of mepolizumab, we observed a significant reduction in blood eosinophil concentration (flow cytometry [mean ± SD] −6442 ± 6852, ADVIA −20 688 ± 19 355 cells/100 µL, Figure 1A) and frequency (flow cytometry [mean ± SD] −1.2 ± 1.2% of total leukocytes, Figure S4A) compared with baseline levels for both methods. This decrease was not observed in our control group (mean ± SD 2475 ± 4148, 285 ± 6977 cells/100 µL and 0.70 ± 1.38%, respectively) (Figure 1A). Notably, the reduction in blood eosinophil levels following mepolizumab was related to baseline eosinophil levels (r2 = 0.69, P < 0.0001, Figure S5). In contrast to eosinophils, basophil concentration and frequency at baseline were similar to that following 16 weeks of mepolizumab, when measured by flow cytometry (pre vs post [mean ± SD] 2232 ± 1309 vs 1873 ± 1647 cells/100 µL, P = 0.23, Figure 1B and 0.40 ± 0.19 vs 0.37 ± 0.27% of total leukocytes, P = 0.076, Figure S4B). Surprisingly, measurements obtained on the ADVIA 2120i suggested a statistically significant reduction in the basophil concentration following 16 weeks of mepolizumab (pre vs post [mean ± SD] 5521 ± 2003 vs 3792 ± 3623 cells/100 µL, P = 0.0009, Figure 1B). The mean ± SD reduction in basophil concentration of −1667 ± 3988 cells/100 µL in asthma was significantly greater compared with the change observed in the control group (vs −571 ± 1222, P = 0.011, Mann-Whitney). In the healthy group, the concentration and frequency of basophils were similar when comparing baseline and follow-up samples, regardless of analytical method (Figures 1B and S4). These data suggest that basophil concentration and frequency, alongside other T2 inflammatory cells (Figure S6), are likely to be IL-5/mepolizumab-independent in severe asthma. However, our real-world study was not sufficiently powered to detect small differences in relation to basophil concentration or frequency. A strength of our flow cytometric approach is that we have measured cell concentration as well as frequency, and also reported recently identified T2 cell subsets (eg peTH2 cells). Our data suggest there were also no indirect effects of mepolizumab on type-2 polarised T cell or group 2 ILC concentration over this 16-week time frame as indicated by others.5 Clinically, we observed a significant change in ACQ6 symptom score from a baseline of 2.9 ± 1.6 to 1.9 ± 1.3 at 16 weeks post-treatment, which is a reduction of −0.92 (97.73% CI of −2 to −0.16, Wilcoxon matched pairs, P = 0.0085), corresponding to an improvement in symptoms above the minimal clinically important difference (MCID) threshold of −0.5. Since baseline eosinophil concentration was associated with basophils (r = 0.53, P = 0.0073), cTH2 (r = 0.59, P = 0.0023), peTH2 (r = 0.45, P = 0.026) and TC2 (r = 0.45, P = 0.026) cells but not total cells (r = 0.2, P = 0.35) or ILC2s (r = 0.2, P = 0.35), we examined their relationship to ACQ6 improvement (ΔACQ6). The baseline cellular parameters described above were not associated with ΔACQ6 (Figure 2, shown for eosinophils, cTH2 and peTH2 cells only). ΔACQ6 was also not associated with the Δ change in eosinophil (r2 = 0.04, P = 0.36) or basophil (r2 = 0.09, P = 0.15) levels post-treatment, limiting the utility of these measurements as symptom response biomarkers. Of further interest was the effect of mepolizumab on eosinophil and basophil cell surface expression of the IL-3 receptor α (CD123), and their relationship to ΔACQ6. IL-3 is upregulated in the serum of poorly controlled asthmatic patients,9 and it can potentiate eosinophil chemotactic and degranulation responses. Recently, mepolizumab treatment, in the context of allergen challenge,8 was associated with reduced levels of IL-3Rα mRNA and protein on circulating blood but not lung eosinophils. Consistent with Kelly et al, we observed a decrease in eosinophil IL-3Rα cell surface expression in response to mepolizumab in asthma (pre [mean ± SD] 415 ± 306 vs post 204 ± 192 GMFI, P < 0.0001, n = 21) and not in our healthy control group (baseline [mean ± SD] 587 ± 626 vs post 558 ± 535 GMFI, P = 0.32, n = 15) (example in Figure S2 and cumulative in S7). This represents a % decrease of −54 ± 25% in asthma compared with +9 ± 55% in the healthy group (mean ± SD, P < 0.0001, Mann-Whitney test). We also noted that eosinophil expression of CRTH2 (CD294) was increased following mepolizumab (Figure S7); however, there was no relationship between the reduction in eosinophil IL-3Rα expression and CRTH2 expression. Importantly, there was no relationship between changes in eosinophil IL-3Ra or CRTH2 expression with ΔACQ6 in these patients. Furthermore, there were no mepolizumab-dependent effects on eosinophil/basophil Siglec-8, CD69 or IL-5Rα expression (not shown), consistent with others8 or basophil IL-3Rα (Figure S7),.and thus, these parameters were not examined for a relationship with ΔACQ6. In summary, our flow cytometric data do not support a direct inhibitory effect of mepolizumab on basophil levels, and therefore, clinical benefit is likely to be independent of basophils. Our data suggest that the specificity and sensitivity of basophil detection on routine clinical analysers should be validated prior to reporting/interpreting basophil data in the context of an intervention. Our data do support others8 that mepolizumab reduces eosinophil, but not basophil, IL-3Rα expression and, importantly, extends the applicability of this phenomenon to the "real-world" scenario. However, neither changes in eosinophil levels nor changes in IL-3Rα expression were associated with clinical efficacy determined by change in asthma control in this study, and thus, biological correlates of response to treatment require further study. This research was funded by Leicester Drug Discovery and Diagnostics (LD3) with financial contributions from MRC grant MC_PC_15045 and supported by the NIHR Leicester Biomedical Research Centre. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Introduction Chronic obstructive pulmonary disease (COPD) is characterized by irreversible airflow obstruction and airway inflammation. Although typically neutrophilic, COPD is eosinophil-predominant in 10%‒40% of cases. Increased airway or blood eosinophil counts are associated with a good response to corticosteroids in stable COPD and during exacerbations. Interleukin-5 (IL-5) binds with high affinity to the IL-5 receptor (R) alpha (IL-5Rα) subunit and plays a pivotal role in the differentiation andmaturation of eosinophils in the bone marrow and their survival in tissue. In a 1-year randomized placebo-controlled trial of benralizumab, a humanized, afucosylated, monoclonal antibody that inhibits IL-5Rα activation and promotes antibody-dependent cellmediated cytotoxicity (leading to near complete eosinophil depletion), improvements in lung function and symptoms and reduction in exacerbations were observed in patients with eosinophilic inflammation. However, in non-eosinophilic COPD patients, exacerbation frequency increased following benralizumab treatment vs placebo. Likewise, in a 6-month trial, the IL-5 neutralizing monoclonal antibody mepolizumab reduced exacerbations vs placebo in COPD patients with an increased blood eosinophil count but resulted in a greater exacerbation frequency in those with a low blood eosinophil count. This finding contrasts with that for asthma for which absence of eosinophilic inflammation is associated with neither benefit nor harm to anti‒IL-5(R). Interestingly, the airway microbiome is distinct between COPD patients with vs those without eosinophilic inflammation. Corticosteroid therapy alters the airway microbiome and consequently might hinder recovery during exacerbations in patients without eosinophilic inflammation. Whether this exacerbation relationship to low eosinophil count is genuine and these effects are partly because of attenuation of Correspondence: Christopher E Brightling University of Leicester, Glenfield General Hospital, Leicester, LE3 9QP, UK Tel +44 116 258 3998 Fax +44 116 25