Airway remodelling rather than cellular infiltration characterizes both type2 cytokine biomarker-high and -low severe asthma

Abstract

Background: The most recognizable phenotype of severe asthma comprises people who are blood eosinophil and FeNO-high, driven by type 2 (T2) cytokine biology, which responds to targeted biological therapies. However, in many people with severe asthma, these T2 biomarkers are suppressed but poorly controlled asthma persists. The mechanisms driving asthma in the absence of T2 biology are poorly understood.

Objectives: To explore airway pathology in T2 biomarker-high and -low severe asthma.

Methods: T2 biomarker-high severe asthma (T2-high, n = 17) was compared with biomarker-intermediate (T2-intermediate, n = 21) and biomarker-low (T2-low, n = 20) severe asthma and healthy controls (n = 28). Bronchoscopy samples were processed for immunohistochemistry, and sputum for cytokines, PGD2 and LTE4 measurements.

Results: Tissue eosinophil, neutrophil and mast cell counts were similar across severe asthma phenotypes and not increased when compared to healthy controls. In contrast, the remodelling features of airway smooth muscle mass and MUC5AC expression were increased in all asthma groups compared with health, but similar across asthma subgroups. Submucosal glands were increased in T2-intermediate and T2-low asthma. In spite of similar tissue cellular inflammation, sputum IL-4, IL-5 and CCL26 were increased in T2-high versus T2-low asthma, and several further T2-associated cytokines, PGD2 and LTE4 , were increased in T2-high and T2-intermediate asthma compared with healthy controls.

Conclusions: Eosinophilic tissue inflammation within proximal airways is suppressed in T2 biomarker-high and T2-low severe asthma, but inflammatory and structural cell activation is present, with sputum T2-associated cytokines highest in T2 biomarker-high patients. Airway remodelling persists and may be important for residual disease expression beyond eosinophilic exacerbations. Registered at ClincialTrials.gov: NCT02883530.

Keywords: FeNO; Th2; cytokine; eosinophil; severe asthma.

Conflict of interest statement

SC has received non‐restricted research grants from the NIHR Oxford BRC, Sanofi‐Genzyme and the Quebec Respiratory Health Research Network; he is the holder of the Association Pulmonaire du Québec's Research Chair in Respiratory medicine; he received speaker honoraria from AstraZeneca, GlaxoSmithKline, Sanofi‐Regeneron and Valeo Pharma; he received consultancy fees for FirstThought; he has received sponsorship to attend international scientific meetings by AstraZeneca. He is an advisory board member for Biometry Inc—a company which is developing a FeNO device (myBiometry); the contract will be remunerated by stock options. RC has received lecture fees from GSK, AstraZeneca, Teva, Chiesi and Sanofi; honoraria for Advisory Board Meetings from GSK, AstraZeneca, Teva, Chiesi and Novarti; sponsorship to attend international scientific meetings from Chiesi, Napp, Sanofi, Boehringer, GSK and AstraZeneca and a research grant to her Institute from AstraZeneca for a UK multi‐centre study. AHM has received personal and institutional payment for talks, advisory board meetings, education and research funding from GSK, AstraZeneca, Teva, Chiesi, NAPP, Sanofi, Novartis, PI. TSCH has received grants from Pfizer Inc., the University of Oxford, the Wellcome Trust, The Guardians of the Beit Fellowship, the NIHR Oxford Biomedical Research Centre, Sensyne Health and Kymab during the conduct of the study; and personal fees from AstraZeneca, TEVA and Peer Voice outside the submitted work. IDP, In the last 5 years, IDP has received speaker's honoraria for speaking at sponsored meetings from Astra Zeneca, Boehringer Ingelheim, Aerocrine, Almirall, Novartis, Teva, Chiesi, Sanofi/Regeneron, Menarini and GSK, and payments for organizing educational events from AstraZeneca, GSK, Sanofi/Regeneron and Teva. He has received honoraria for attending advisory panels with Genentech, Sanofi/Regeneron, Astra Zeneca, Boehringer Ingelheim, GSK, Novartis, Teva, Merck, Circassia, Chiesi and Knopp, and payments to support FDA approval meetings from GSK. He has received sponsorship to attend international scientific meetings from Boehringer Ingelheim, GSK, AstraZeneca, Teva and Chiesi. He has received a grant from Chiesi to support a phase 2 clinical trial in Oxford. In 2014–5 and 2019–20, he was an expert witness for a patent dispute involving AstraZeneca and Teva. SJF has received grants from Boehringer Ingelheim and fees from AstraZeneca, Boehringer Ingelheim, Novartis, Teva and Chiesi. LPM declares Research funding from Chiesi and Merck; consultancies for Chiesi, Glaxo Smith Kline, Merck, Sanofi, Genentech and support to attend scientific meetings from Chiesi, Merck and Bayer. LGH reports grants from Genentech/Hoffman la Roche, during the conduct of the study; other from AstraZeneca, Boehringer Ingelheim, Chiesi, GSK and Napp Pharmaceuticals, personal fees from Novartis, Hoffman la Roche/Genentech Inc, Sanofi, Evelo Biosciences, Glaxo Smith Kline, Astra Zeneca, Teva, Theravance, Circassia, grants from Medimmune, Novartis UK, Roche/Genentech Inc and Glaxo Smith Kline, Amgen, Genentech/Hoffman la Roche, Astra Zeneca, Medimmune, Glaxo Smith Kline, Aerocrine and Vitalograph, outside the submitted work. CDA is an employee of Genentech. PHH is an employee of GSK. JRA is an employee of Genentech. DC is an employee of Genentech. PB has received research funding from Genentech via the University Hospitals of Leicester NHS Trust; consultancies for Boehringer Ingelheim, Genentech and Celldex Therapeutics via the University of Leicester. Support to attend scientific meetings from Chiesi, Teva and Sanofi‐Genzyme. BH, LC, FAS, SB, RS, VB no conflict of interest.

© 2022 The Authors. Allergy published by European Academy of Allergy and Clinical Immunology and John Wiley & Sons Ltd.

Figures

FIGURE 1

Eosinophil and neutrophil numbers in asthma subgroups and healthy controls. A) Eosinophil numbers in the airway lamina propria (Kruskal–Wallis p = 0.8444). B) Neutrophil numbers in the airway lamina propria (Kruskal–Wallis p = 0.0119). C) Neutrophil numbers in the airway epithelium (Kruskal–Wallis: p = 0.0197 all groups, p = 0.0105 asthma groups). **p = 0.0043 compared with healthy controls, #p = 0.0120 compared with T2‐intermediate (Dunn's multiple comparison test). Red points represent people taking oral corticosteroids

FIGURE 2

Mast cell numbers in asthma subgroups and healthy controls. A) Tryptase+ mast cell numbers in the airway lamina propria (ANOVA p < 0.0001). B) Chymase+ mast cell numbers in the airway lamina propria (Kruskal–Wallis p < 0.0001). C) Tryptase+ mast cell numbers within the airway smooth muscle (ASM) (Kruskal Wallis p = 0.0923). D) Chymase+ mast cell numbers within the ASM (Kruskal–Wallis p = 0.1346). E) The chymase:tryptase ratio in the lamina propria (Kruskal–Wallis p = 0.0280). F) The chymase:tryptase ratio in the airway epithelium, lamina propria and ASM in people with asthma (Kruskal–Wallis, p = 0.0018) (where chymase+ cells were present but there were no tryptase+ cells, values of 2 were given). For A‐E) *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 compared with healthy controls (Dunnett's or Dunn's multiple comparison tests as appropriate). For F) ##p < 0.01 compared with airway epithelium (Dunn's multiple comparison test). Red points represent people taking oral corticosteroids

FIGURE 3

Remodelling features in asthma subgroups and healthy controls. A) Airway smooth muscle (ASM) mass expressed as a percentage of total biopsy area (Kruskal–Wallis p = 0.0098). B) Mucosal gland mass expressed as a percentage of total biopsy area (Kruskal–Wallis p = 0.0026). C) MUC5AC immunostaining expressed as a percentage of epithelial area (Kruskal–Wallis p < 0.0001). D) Reticular basement membrane (RBM) thickness (ANOVA p = 0.0910). *p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 compared with healthy controls (Dunn's multiple comparison test). For A), #p = 0.0506 compared with healthy (Dunn's multiple comparison test). Red points represent people taking oral corticosteroids

FIGURE 4

T2‐associated cytokine/chemokine, LTE4 and PGD2 concentrations in induced sputum supernatants in asthma subgroups and healthy controls. *p < 0.05, **p < 0.01, compared with healthy controls (Dunn's multiple comparison test). #p < 0.05 compared with T2‐low (Dunn's multiple comparison test). Red points represent people taking oral corticosteroids. Dotted lines represent the lower limit of detection