Background: Coronavirus disease 2019 is caused by SARS-coronavirus 2 (SARS-CoV-2). Angiotensin converting enzyme 2 (ACE2) and transmembrane protease serine 2 (TMPRSS2) mediate viral infection of host cells. We reasoned that differences in ACE2 or TMPRSS2 gene expression in sputum cells among asthma patients may identify subgroups at risk for COVID19 morbidity. Methods:We analyzed gene expression for ACE2 and TMPRSS2, and for intercellular adhesion molecule 1 (ICAM-1)(rhinovirus receptor as a comparator), in sputum cells from 330 participants in the Severe Asthma Research Program-3 and 79 healthy controls.Results: Gene expression of ACE2 was lower than TMPRSS2, and expression levels of both genes was similar in asthma and health. Among asthma patients, male gender, African Americans race, and history of diabetes mellitus, was associated with higher expression of ACE2 and TMPRSS2. Use of inhaled corticosteroids (ICS) was associated with lower expression of ACE2 and TMPRSS2, but treatment with triamcinolone acetonide (TA) did not decrease expression of either gene. These findings differed from those for ICAM-1, where gene expression was increased in asthma and less consistent differences were observed related to gender, race, and use of ICS. Conclusion:Higher expression of ACE2 and TMPRSS2 in males, African Americans, and patients with diabetes mellitus provides rationale for monitoring these asthma subgroups for poor COVID19 outcomes. The lower expression of ACE2 and TMPRSS2 with ICS use warrants prospective study of ICS use as a predictor of decreased susceptibility to SARS-CoV-2 infection and decreased COVID19 morbidity. the participant level with restricted maximum likelihood models. P-values <0.05 were considered statistically significant. RESULTS SubjectsThe demographic and clinical features of the asthma patients and healthy controls are shown in Table 1. Gene expression for SARS-Cov-2-and HRV-related genes in induced sputum cells from asthma patients and healthy controlsIn induced sputum cells collected at the baseline visit, the expression levels of ACE2 were lower than the expression levels of TMPRSS2, and some sputum samples had undetectable ACE2 ( Figure 1A). The expression of ACE2 and TMPRSS2 did not differ significantly in health and in asthma ( Figure 1A,B). In contrast to the SARS-Co-V2related genes, gene expression of ICAM1 was higher in asthma than in health ( Figure 1C). The expression of ACE2 was strongly associated with the expression of TMPRSS2 in the healthy control subgroup (Figure 2A) and the asthma subgroup ( Figure 2B), suggesting that these genes are expressed in similar cells(18). Relationship between clinical and demographic variables and expression levels of SARS-Cov-2-and HRV-related genes in asthma patientsHere we analyzed gene expression data in the induced sputum samples collected at the baseline visit 2 and the follow up visits 4 (year 1) and 6 (year 3). The total number was 556 samples from 330 asthma subjects. ACE2 and TMPRSS2 expression levels increased slightly with age, bu...

No abstract

Background Severe asthma is a complex heterogeneous disease associated with older age and obesity. The presence of eosinophilic (type 2) inflammation in some but not all patients with severe asthma predicts responsiveness to current treatments, but new treatment approaches will require better understanding of non-type 2 mechanisms of severe asthma. We considered the possibility that systemic inflammation - which occurs in subgroups of obese and older patients - modifies asthma to make it worse. Interleukin 6 (IL6) is a biomarker of systemic inflammation and metabolic dysfunction, and we aimed to explore the relationship between IL6, metabolic dysfunction, and asthma severity. Methods We generated a reference range in health for plasma IL6 in a cohort of healthy controls (n=93). We compared the clinical characteristics of asthmatics with plasma IL6 levels below and above the upper limit of normal (“IL6 low” and “IL-high” asthma) in two asthma cohorts - predominantly non-severe asthmatics recruited at the University of California San Francisco (UCSF)(n=249) and predominantly severe asthmatics recruited by the Severe Asthma Research Program (SARP)(n=387). Findings The upper 95th centile value for plasma IL6 in the healthy cohort was 3·1pg/mL, and 14% of UCSF cohort and 26% of the SARP cohort had plasma IL6 levels above this upper limit. The “IL6-high” patients in both asthma cohorts had a significantly higher body mass index and a higher prevalence of metabolic disease than the IL6-low patients (all p values < 0.01). IL6-high patients also had significantly lower lung function and more frequent asthma exacerbations than IL6-low patients (all p values < 0·01). Although 75% of IL6-high asthmatics were obese, 63% of obese patients were IL6-low. Among obese patients, the forced expired volume in one second (FEV1) was significantly lower in IL6-high than in IL6-low patients (mean FEV1 70·8 [S.D. 19·5] vs. 78·1 [19·7] % predicted, p = 0·002), and the percentage of patients reporting an asthma exacerbation in the past 1-2 years was higher in IL6-high than in IL6-low patients (66 vs. 48%, p = 0·003). Among non-obese asthmatics, FEV1% and asthma exacerbation outcomes were also significantly worse in IL6-high than in IL6-low patients (mean FEV1 66·4 [SD 23·1] vs. 83·2 [20·4] % predicted, p< 0·01; 59 vs. 34 %, p=0·008). Interpretation Systemic IL6 inflammation and clinical features of metabolic dysfunction - occurring most commonly among a subset of obese asthmatics but also in a small subset of non-obese patients - is associated with more severe asthma. IL6 inhibitors or treatments that improve metabolic dysfunction represent rational clinical trials to pursue for a subset of patients with severe asthma, and plasma IL6 is a biomarker that could guide patient stratification.

No abstract

Rationale: Extracellular DNA (eDNA) and neutrophil extracellular traps (NETs) are implicated in multiple inflammatory diseases. NETs mediate inflammasome activation and IL-1b secretion from monocytes and cause airway epithelial cell injury, but the role of eDNA, NETs, and IL-1b in asthma is uncertain. Objectives: To characterize the role of activated neutrophils in severe asthma through measurement of NETs and inflammasome activation. Methods: We measured sputum eDNA in induced sputum from 399 patients with asthma in the Severe Asthma Research Program-3 and in 94 healthy control subjects. We subdivided subjects with asthma into eDNA-low and-high subgroups to compare outcomes of asthma severity and of neutrophil and inflammasome activation. We also examined if NETs cause airway epithelial cell damage that can be prevented by DNase. Measurements and Main Results: We found that 13% of the Severe Asthma Research Program-3 cohort is "eDNA-high," as defined by sputum eDNA concentrations above the upper 95th percentile value in health. Compared with eDNA-low patients with asthma, eDNAhigh patients had lower Asthma Control Test scores, frequent history of chronic mucus hypersecretion, and frequent use of oral corticosteroids for maintenance of asthma control (all P values ,0.05). Sputum eDNA in asthma was associated with airway neutrophilic inflammation, increases in soluble NET components, and increases in caspase 1 activity and IL-1b (all P values ,0.001). In in vitro studies, NETs caused cytotoxicity in airway epithelial cells that was prevented by disruption of NETs with DNase. Conclusions: High extracellular DNA concentrations in sputum mark a subset of patients with more severe asthma who have NETs and markers of inflammasome activation in their airways.

Asthma is characterized by airway inflammation rich in eosinophils. Airway eosinophilia is associated with exacerbations and has been suggested to play a role in airway remodeling. Recruitment of eosinophils from the circulation requires that blood eosinophils become activated, leading to their arrest on the endothelium and extravasation. Circulating eosinophils can be envisioned as potentially being in different activation states, including non-activated, pre-activated or “primed”, or fully activated. In addition, the circulation can potentially be deficient of pre-activated or activated eosinophils, because such cells have marginated on activated endothelium or extravasated into the tissue. A number of eosinophil-surface proteins, including CD69, L-selectin, intercellular adhesion molecule-1 (ICAM-1, CD54), CD44, P-selectin glycoprotein ligand-1 (PSGL-1, CD162), cytokine receptors, Fc receptors, integrins including αM integrin (CD11b), and activated conformations of Fc receptors and integrins have been proposed to report cell activation. Variation in eosinophil activation states may be associated with asthma activity. Eosinophil-surface proteins proposed to be activation markers, with a particular focus on integrins, and evidence for associations between activation states of blood eosinophils and features of asthma are reviewed here. Partial activation of β1 and β2 integrins on blood eosinophils, reported by monoclonal antibodies (mAb) N29 and KIM-127, is associated with impaired pulmonary function and airway eosinophilia, respectively, in non-severe asthma. The association with lung function does not occur in severe asthma, presumably due to greater eosinophil extravasation, specifically of activated or pre-activated cells, in severe disease.

Eosinophilic inflammation is a characteristic feature of asthma. Integrins are highly versatile cellular receptors that regulate extravasation of eosinophils from the postcapillary segment of the bronchial circulation to the airway wall and airspace. Such movement into the asthmatic lung is described as a sequential, multistep paradigm, whereby integrins on circulating eosinophils become activated, eosinophils tether in flow and roll on bronchial endothelial cells, integrins on rolling eosinophils become further activated as a result of exposure to cytokines, eosinophils arrest firmly to adhesive ligands on activated endothelium, and eosinophils transmigrate to the airway in response to chemoattractants. Eosinophils express seven integrin heterodimeric adhesion molecules: alpha4beta1 (CD49d/29), alpha6beta1 (CD49f/29), alphaMbeta2 (CD11b/18), alphaLbeta2 (CD11a/18), alphaXbeta2 (CD11c/18), alphaDbeta2 (CD11d/18), and alpha4beta7 (CD49d/beta7). The role of these integrins in eosinophil recruitment has been elucidated by major advances in the understanding of integrin structure, integrin function, and modulators of integrins. Such findings have been facilitated by cellular experiments of eosinophils in vitro, studies of allergic asthma in humans and animal models in vivo, and crystal structures of integrins. Here, we elaborate on how integrins cooperate to mediate eosinophil movement to the asthmatic airway. Antagonists that target integrins or the effectors that regulate integrins of eosinophils represent potentially promising therapies in the treatment of asthma.

Periostin is an extracellular matrix protein that is up-regulated by T helper cell type 2 cytokines in the asthmatic airway and implicated in mouse studies as promoting eosinophil recruitment. We asked whether periostin modulates eosinophil adhesion and motility in vitro. Periostin adsorbed to polystyrene supported adhesion of purified human blood eosinophils stimulated by IL-5, IL-3, or granulocyte/macrophage colony-stimulating factor, but did not support adhesion of eosinophils treated with IL-4 or IL-13. The degree of adhesion depended on the concentrations of periostin during coating and activating cytokine during the adhesion assay. Both full-length periostin and alternatively spliced periostin, lacking C-terminal exons 17, 18, 19, and 21, supported adhesion. Adhesion was inhibited by monoclonal antibody to α(M) or β(2) integrin subunits, but not by antibodies to other eosinophil integrin subunits. Adsorbed periostin also supported α(M)β(2)-dependent random motility of IL-5-stimulated eosinophils with optimal movement at an intermediate coating concentration. In the presence of IL-5, eosinophils adherent on periostin formed punctate structures positive for filamentous actin, gelsolin, and phosphotyrosine. These structures fit the criteria for podosomes, highly dynamic adhesive contacts that are distinct from classical focal adhesions. The results establish α(M)β(2) (CD11b/CD18, Mac-1) as an adhesive and promigratory periostin receptor on cytokine-stimulated eosinophils, and suggest that periostin may function as a haptotactic stimulus able to guide eosinophils to areas of high periostin density in the asthmatic airway.