BACKGROUND: 5-10% of patients with asthma have severe disease. Many patients experience persistent symptoms despite being T2-low. Obesity is associated with increased asthma symptoms. Eicosanoids have well-described roles in the pathophysiology of asthma and may contribute to persistent symptoms in T2-low severe asthma. OBJECTIVE: To examine the relationship between urinary eicosanoids, asthma symptoms, obesity and T2-biomarkers in severe asthma. METHODS: Urine samples were collected during a randomized controlled trial assessing corticosteroid optimization using T2-biomarker directed care at scheduled study visits (n=728) and at exacerbation (n=103). Eicosanoid concentrations were quantified from urine samples using mass-spectrometry. Metabolite concentrations were log 2-transformed, z-scored and concentrated by pathway to generate 6 pathway scores. Results were stratified by T2-biomarker status (T2-Low: fractional-exhaled nitric-oxide [FeNO]<20ppb AND blood eosinophil count [BEC]<0.15x10 9cells/L) vs T2-high: (FeNO≥20ppb AND BEC≥0.15x10 9cells/L), symptoms (symptom-low: Asthma control Questionnaire-7 (ACQ-7)<1.5)] vs symptom-high [ACQ-7≥1.5]), and obesity. RESULTS: The cysteinyl-leukotriene (CysLT) pathway score was elevated in T2-high versus T2-low participants (P=0.0007), regardless of symptom burden. The isoprostane pathway score was higher in symptom-high versus symptom-low participants, regardless of T2-status (P=0.01). Higher isoprostane (P=0.02) and thromboxane (P=0.04) pathway scores were associated with increased symptoms in T2-low participants. Corticosteroid exposure, obesity and exacerbations were not associated with raised pathway scores (P≥0.05). CONCLUSION: Thromboxane pathway metabolites were elevated in symptom-high/T2-low participants whereas isoprostane pathway metabolites were associated with increased symptoms, regardless of T2-status. These pathways are not affected by CS exposure. Further research is needed to define the role of eicosanoids in T2-low severe asthma using interventions to perturb these pathways.

Background. Because of altered airway microbiome in asthma, we analysed the bacterial species in sputum of patients with severe asthma. Methods. Whole genome sequencing was performed on induced sputum from non-smoking (SAn) and current or ex-smoker (SAs/ex) severe asthma patients, mild/moderate asthma (MMA) and healthy controls (HC). Data was analysed by asthma severity, inflammatory status and transcriptome-associated clusters (TACs). Results. α-diversity at the species level was lower in SAn and SAs/ex, with an increase in Haemophilus influenzae and Moraxella catarrhalis, and Haemophilus influenzae and Tropheryma whipplei, respectively, compared to HC. In neutrophilic asthma, there was greater abundance of Haemophilus influenzae and Moraxella catarrhalis and in eosinophilic asthma, Tropheryma whipplei was increased. There was a reduction in α-diversity in TAC1 and TAC2 that expressed high levels of Haemophilus influenzae and Tropheryma whipplei, and Haemophilus influenzae and Moraxella catarrhalis, respectively, compared to HC. Sputum neutrophils correlated positively with Moraxella catarrhalis and negatively with Prevotella, Neisseria and Veillonella species and Haemophilus parainfluenzae. Sputum eosinophils correlated positively with Tropheryma whipplei which correlated with pack-years of smoking. α- and β-diversities were stable at one year. Conclusions. Haemophilus influenzae and Moraxella catarrhalis were more abundant in severe neutrophilic asthma and TAC2 linked to inflammasome and neutrophil activation, while Haemophilus influenzae and Tropheryma whipplei were highest in SAs/ex and in TAC1 associated with highest expression of IL-13 Type 2 and ILC2 signatures with the abundance of Tropheryma whipplei correlating positively with sputum eosinophils. Whether these bacterial species drive the inflammatory response in asthma needs evaluation.