Impact of allergen sensitization on phenotypes of T2-low asthma: a post-hoc analysis of a nationwide cohort study, NHOM Asthma.

Background: In the treatment of asthma, the presence or absence of type 2 (T2) inflammation is considered, namely T2-high, T2-low asthma. While treatment options for T2-high asthma are remarkably increasing, phenotype of T2-low asthma have not yet been fully identified and optimal therapeutic targets remain unclear. Objective: The present study aimed to identify the clinical indices that contribute to asthma exacerbations in T2-low asthma, and phenotypes of patients with T2-low asthma. Methods: This study used data from a nationwide asthma cohort study in Japan, NHOM Asthma Study (N = 1925). T2-low asthma was defined as a blood eosinophils count < 150 /µL and fractional exhaled nitric oxide level < 25 ppb, and clinical characteristics involved in asthma exacerbations were identified using univariate and multivariate analysis. Furthermore, T2-low asthma was phenotyped via hierarchical cluster analysis using Ward's method. Results: Multivariate analysis revealed that the contributing factors to asthma exacerbations were allergic disease comorbidity and ACQ-6 failure. There were four phenotypes among patients with T2-low asthma: Cluster 1 (mild ACO), Cluster 2 (severe ACO), Cluster 3 (elderly, female-dominant, late-onset), and Cluster 4 (younger, female-dominant, complicated with allergic disease), and the number of asthma exacerbations was higher in the order of Cluster 2 and 4. The diversification of sensitizing allergens was observed in Cluster 2 and 4. Conclusion: The present study suggested that comorbidity of allergic diseases and allergen sensitization may be involved in the severity of asthma in T2-low asthma.

There are two major pathological phenotypes of asthma, type 2 (T2)-high and T2-low asthma, which are important in determining treatment strategies. However, the characteristics and phenotypes of T2-high asthma have not yet been fully identified. This study aimed to identify the clinical characteristics and phenotypes of patients with T2-high asthma. This study used data from a nationwide asthma cohort study in Japan, NHOM Asthma Study. T2-high asthma was defined as a blood eosinophils count ≥ 300 /μL and/or fractional exhaled nitric oxide level ≥ 25 ppb, and the clinical characteristics and biomarkers were compared between T2-high and T2-low asthma. Furthermore, T2-high asthma was phenotyped via hierarchical cluster analysis using Ward's method. Patients with T2-high asthma were older, less likely to be female, had longer asthma duration, had lower pulmonary function, and had more comorbidities, including sinusitis and SAS. Patients with T2-high asthma showed higher serum thymus and activation-regulated chemokine and urinary leukotriene E4 levels and lower serum ST2 levels than those with T2-low asthma. There were four phenotypes among patients with T2-high asthma: Cluster 1 (youngest, early-onset, and atopic), Cluster 2 (long duration, eosinophilic, and low lung function), Cluster 3 (elderly, female-dominant, and late-onset), and Cluster 4 (elderly, late-onset, and asthma-COPD overlap-dominant). Patients with T2-high asthma have distinct characteristics and four distinct phenotypes, in which eosinophil-dominant Cluster 2 is the most severe phenotype. The present findings may be useful in precision medicine for asthma treatment in the future.

Diagnosis and Treatment Options for T2-Low Asthma.

<b>Introduction:</b>&nbsp;Inhaled corticosteroids (ICS) reduce exacerbations in asthma. However, the different mechanisms underlying the effect of these drugs in T2-high and T2-low phenotypes are largely unknown. <b>Aim:</b>&nbsp;To evaluate the effect of ICS treatment on bronchial epithelial response to TLR3 stimulation in T2-high and T2-low asthma patients. <b>Methods:</b>&nbsp;Bronchial epithelial cells (BECs) from patients with T2-high (FeNO&gt;25ppb; N=8) and T2-low (N=9) asthma, before and after inhaled budesonide (6 weeks; 1600mg/day), were used. Poly(I:C) (TLR3 agonist) was used as viral mimic. Proteomic (LC-MS/MS) and RTqPCR analyses were performed in BECs homogenates, and ELISA in BECs supernatants. <b>Results:</b>&nbsp;171 proteins were upregulated in poly(I:C)-stimulated BECs from T2-high/atopic vs. T2-low/non-atopic patients (p&lt;0.05/FC&gt;1.5), including proteins from biological process categories related to immune system (e.g., GO:0045087, GO:0016032, or GO:0034097). ICS treatment reduced this exaggerated BECs response in T2-high patients (4 proteins up, 220 down; p&lt;0.05/FC&gt;1.5), whereas the opposite effect was found in T2-low asthma (34 up; 7 down; p&lt;0.05/FC&gt;1.5). Moreover, an increased IFN-β release in response to poly (I:C) was found in BECs from T2-low patients after ICS treatment (p&lt;0.05), and the same was shown for TNF-α both at gene (p=0.05) and protein (p&lt;0.05) level. <b>Conclusion:</b> Budesonide treatment had differing but beneficial effects on the airway epithelial response to a viral mimic in both T2-high and T2 low asthma.

The Association Between Fractional Exhaled Nitric Oxide (FeNO) and Allergic Diseases and Asthma at Age Six Years in a High Risk Birth Cohort

Asthma represents a heterogeneous chronic respiratory condition. Type 2 (T2) inflammation is the most crucial pathological event in asthma. In terms of whether T2 inflammation is dominant or not, asthma can be classified into T2-high and T2-low asthma. Currently, there exists a significant gap in our understanding of the heterogeneity of treatment-naive T2-high asthma patients. Moreover, no studies have examined the impacts of inhaled corticosteroids (ICS) on the airway microenvironment and metabolism of T2-high asthma during the early stage of treatment. This study, by employing multi-omic techniques, investigated the pathophysiological features and heterogeneity of untreated T2-high asthma, as well as the effects of ICS treatment. This study provided more in-depth insights into the pathophysiological mechanisms underlying T2-high asthma heterogeneity. Thirty-one treatment-naive T2-high asthma patients and fourteen healthy individuals were enrolled in this study. On the basis of hierarchical clustering analysis of T2 inflammation markers, fractional exhaled nitric oxide (FeNO) level and blood eosinophil count (BEC), the T2-high asthma patients were divided into three subgroups in terms of FeNO levels (≤ 25 ppb, 26-50 ppb, and > 50 ppb). All asthma patients underwent asthma control scoring, pulmonary function tests, and FeNO measurement at baseline and during a regular 3-month follow-up. Induced sputum and plasma were collected. Other tests included 16S rRNA microbiome profiling of the induced sputum, Luminex xMAP immunoassays of cytokines, and plasma metabolomic analysis using Q-Exactive liquid chromatography-mass spectrometry (LC-MS/MS). Meanwhile, data from the healthy population were also harvested. T2-high asthma patients differed significantly from healthy controls in terms of airway inflammatory cytokines, airway microbial community structure, and plasma metabolic profiles. At baseline, T2-high asthma patients with different FeNO levels exhibited remarkable similarities in clinical symptoms, pulmonary function indices, airway cytokines, airway microbial diversity, and metabolites. After treatment with ICS, symptoms improved in T2-high asthma patients. The levels of FeNO, blood eosinophils, and total immunoglobulin E (tIgE) decreased significantly, while pulmonary function did not show substantial improvement. Some indices of airway cytokines underwent changes. No differences were found in airway microbial diversity; however, the abundance of Actinomyces increased. Moreover, the levels of glycerophospholipids and arachidonic acid metabolites decreased. Differentially expressed metabolites were enriched in arachidonic acid metabolism. The effect of ICS treatment varied among different T2-high asthma subgroups. The airway local microenvironment and systemic metabolic profiles of treatment-naive T2-high asthma patients were distinctly different from those of healthy individuals. Limited heterogeneity was observed among patients stratified in terms of T2-inflammatory burden. ICS altered the airway microenvironment and rectified the lipid/arachidonic acid metabolic dysregulation. However, ICS effects varied across various T2-high subgroups.

Fractional exhaled nitric oxide (FENO) level is directly correlated with airway inflammation in asthma patients. The objective of this study was to define normal FENO levels in healthy Thai volunteers. This prospective cohort study was conducted in healthy Thai volunteers aged ≥5 years. Demographic and clinical data were recorded and pulmonary function test (PFT) was performed. FENO was measured using a chemiluminescence nitric oxide analyzer. Seventy-nine healthy Thai volunteers with normal lung function test were included. Mean age of participants was 13 (6-47) years and 58.2% were female. All subjects had no history of allergic respiratory diseases. Mean FENO level increased with age, and the differences between age groups were statistically significant (p=0.001). The highest mean FENO level was 13.6 ppb in the 11-15 year age group, and then the FENO level gradually declined with age. The highest mean FENO level was found in the 18-24.9 body mass index (BMI) group. Significant differences were observed for FENO levels between different height groups (p=0.005) but not between different BMI groups (p=0.46). Fair correlations between FENO levels and body weight, height, FEV1, and FVC were observed. A fair correlation between FENO level and age, FENO level and FEF25%-75% was found only in volunteers ≤15 years of age. FENO level in healthy Thais increased with age until reaching maximum level (mean FENO 13.6 ppb) in the 11-15 year age group. Significant differences were observed for FENO levels between different age groups and different height groups.

We investigated the stability of T2 low status, based on low levels of T2 biomarkers, and exacerbation rates in T2 low and non-T2 low asthma from clinical retrospective data of severe uncontrolled asthma patients. Knowledge of the T2 low biomarker profile is sparse and biomarker stability is uncharted. Secondary care patients with severe uncontrolled asthma and at least two blood eosinophil counts (BEC) and fractional exhaled nitric oxide (FeNO) measured for determination of type 2 inflammation status were evaluated from a follow-up period of 4 years. Patients were stratified into four groups: T2 low150 (n = 31; BEC < 150 cells/µL and FeNO < 25 ppb), non-T2 low150 (n = 138; BEC > 150 cells/µL and/or FeNO > 25 ppb), T2 low300 (n = 66; BEC < 300 cells/µL and FeNO < 25 ppb), and non-T2 low300 (n = 103; BEC > 300 cells/µL and/or FeNO > 25 ppb). Exacerbation rates requiring hospital care, stability of biomarker status, and cumulative OCS and ICS doses were assessed during follow-up. Among patients with severe uncontrolled asthma, 18% (n = 31) were identified as T2 low150, and 39% (n = 66) as T2 low300. In these groups, the low biomarker profile was stable in 55% (n = 11) and 72% (n = 33) of patients with follow-up measures. Exacerbation rates were different between the T2 low and non-T2 low groups: 19.7 [95% CI: 4.3-45.6] in T2 low150 vs. 8.4 [4.7-13.0] in non-T2 low150 per 100 patient-years. BEC and FeNO are useful biomarkers in identifying T2 low severe uncontrolled asthma, showing a stable follow-up biomarker profile in up to 72% of patients. Repeated monitoring of these biomarkers is essential in identifying and treating patients with T2 low asthma.

Asthma is a heterogeneous and complex condition characterized by chronic airway inflammation, which may be clinically stratified into three main phenotypes: type 2 (T2) low, T2-high allergic, and T2-high non-allergic asthma. This real-world study investigated whether phenotyping patients with asthma using non-invasive parameters could be feasible to characterize the T2-low and T2-high asthma phenotypes in clinical practice. This cross-sectional observational study involved asthmatic outpatients (n = 503) referring to the Severe Asthma Centre of the San Luigi Gonzaga University Hospital. Participants were stratified according to the patterns of T2 inflammation and atopic sensitization. Among outpatients, 98 (19.5%) patients had T2-low asthma, 127 (25.2%) T2-high non-allergic, and 278 (55.3%) had T2-high allergic phenotype. In comparison to T2-low, allergic patients were younger (OR 0.945, p < 0.001) and thinner (OR 0.913, p < 0.001), had lower smoke exposure (OR 0.975, p < 0.001) and RV/TLC% (OR 0.950, p < 0.001), higher prevalence of asthma severity grade 5 (OR 2.236, p < 0.05), more frequent rhinitis (OR 3.491, p < 0.001) and chronic rhinosinusitis with (OR 2.650, p < 0.001) or without (OR 1.919, p < 0.05) nasal polyps, but less common arterial hypertension (OR 0.331, p < 0.001). T2-high non-allergic patients had intermediate characteristics. Non-invasive phenotyping of asthmatic patients is possible in clinical practice. Identifying characteristics in the three main asthma phenotypes could pave the way for further investigations on useful biomarkers for precision medicine.

RATIONALE: Considering that nitric oxide is a significant pathophysiological mediator of pulmonary hypertension for maintaining vascular health, the aim of this study was to investigate the relationship between fractional exhaled nitric oxide (FENO) level and respiratory muscle strength, pulmonary function, exercise capacity, sleep quality, functional status, and health-related quality of life (HRQoL) in patients with pulmonary arterial hypertension (PAH). METHODS: Clinically and hemodynamically stable 48 PAH patients (idiopathic n=22, associated with congenital heart disease n=26) under PAH-specific therapy for a minimum of 3 months, between the ages 20-74 (mean [SD] age: 48.4 [12.1] years) and with the World Health Organization (WHO) functional class I to III participated in the study. Online measurement of FENO was performed using a portable electrochemical analyzer, with a constant expiratory flow rate of 0.05 L/second. Respiratory muscle strength was assessed by measuring maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) through a mouth pressure meter. Forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), FEV1/FVC ratio, and peak expiratory flow (PEF) values were measured with a spirometer. Exercise capacity was evaluated by measuring 6-minute walk distance (6MWD) with 6-minute walk test. Sleep quality was assessed with Pittsburgh Sleep Quality Index (PSQI). Functional status was determined by using WHO functional classification. HRQoL was assessed with emPHasis-10, a disease-specific questionnaire. Spearman correlation analysis was used for statistical data analyses. RESULTS: Mean FENO level of the patients was 12,4±3,3 parts per billion. There was a statistically significant positive correlation between FENO and MIP (r=,399, p=0,005), MEP (r=,494, p=0,000), FEV1 (r=,407, p=0,004), FVC (r=,435, p=0,002), PEF (r=,322, p=0,026), 6MWD (r=,691, p=0,000). Higher FENO values were also statistically associated with improved WHO functional class (r=-,648, p=0,000), PSQI global score (r=-,703, p=0,000) and emPHasis-10 score (r=-,407, p=0,004). However, no significant correlation was found between FENO level and FEV1/FVC ratio (r=0.121, p=0.411). CONCLUSION: This study, conducted on PAH patients, demonstrated that FENO level was strongly associated with exercise capacity, functional classification, sleep quality and that there was a moderate correlation between FENO level and respiratory muscle strength, HRQoL, and pulmonary function except FEV1/FVC ratio. Therefore, monitoring FENO levels for the evaluation and management of pulmonary hypertension in clinical practice may be useful.

Association between allergic sensitization and exhaled nitric oxide in children in the School Inner-City Asthma Study

The evaluation of patients with asthma uses clinical tools such as the Asthma Control Test (ACT), pulmonary function tests, and biomarkers. Among these, an elevated fractional exhaled nitric oxide (FeNO) level can predict a higher risk of exacerbations and response to corticosteroids and/or biological therapies, although it does not always reflect poor clinical control. Our objective was to determine the relationship between asthma severity and FeNO levels in patients attending our service. A cross-sectional study was conducted in patients over 12 years of age with controlled asthma assessed by ACT. FeNO was measured using the NIOX-VERO® device. Descriptive analysis and Spearmans correlation coefficient were applied. Thirty-six patients (66.7% women) with a mean age of 36.3 years (SD ± 14.4) were included. According to GINA, 63.9% had mild asthma and 36.1% had moderate asthma. 22.2% had low FeNO levels (<25 ppb) and 52.8% had high levels (>50 ppb). The mean FeNO level in mild asthma was 62.7 ppb (SD ± 62.7) and in moderate asthma, 54.8 ppb (SD ± 36.2). No significant correlation was found between asthma severity and FeNO levels (rs = 0.150, p = 0.306). Although more than half of the patients had elevated FeNO levels, no significant association was observed with asthma severity. This finding is consistent with previous studies and suggests that FeNO, although useful as a biomarker of type 2 inflammation, should not be used in isolation to assess clinical severity.

Type 2-low (T2-low) asthma represents a heterogeneous chronic respiratory condition typified by airway inflammation that is not driven by eosinophils and inferior response to conventional therapies. With India facing a burden of approximately 34.3 million asthma cases, constituting 13.09% of the global burden, understanding T2-low endotypes is crucial for effective management. This review synthesizes current knowledge on T2-low asthma, encompassing neutrophilic, mixed granulocytic, and paucigranulocytic phenotypes. The pathophysiology involves complex mechanisms including neutrophil activation, NLRP3 inflammasome signaling, epithelial dysfunction, and cytokine pathways mediated by IL-17, IL-33, IL-1β, and IL-6. T2-low asthma patients demonstrate corticosteroid resistance, frequent exacerbations, and airway remodeling. Emerging biomarkers show promise for precise endotyping, including YKL-40, S100A9, serum amyloid A1 (SAA1), and neutrophil extracellular trap (NET) components. Novel therapeutic approaches targeting specific inflammatory pathways, like IL-33/ST2 inhibitors, IL-1β modulators, and TGF-β antagonists, offer hope for personalized treatment. This comprehensive overview highlights recent developments in biomarker identification and targeted therapies that may transform T2-low asthma management, moving toward precision medicine for this challenging patient population.

<b>Introduction:</b> Asthmatics with BHR to mannitol demonstrate clinical benefit with regular ICS. It has been demonstrated FeNO should be &gt;47ppb for clinical benefits to ICS. However, it has been observed that many with BHR to mannitol have ‘normal’ (0-24ppb) or ‘borderline’ (25-47ppb) FeNO levels, suggesting no benefit with ICS. <b>Aim:</b> To determine if a clinical benefit is observed with ICS in uncontrolled asthmatics with BHR to mannitol that have FeNO levels ≤47ppb. <b>Methods:</b> Adult asthmatics (n=20) who were referred to a pulmonary function laboratory for an assessment of BHR to inhaled mannitol also performed FeNO and the Asthma Control Questionnaire (ACQ). All participants entered the study with an ACQ score &gt;0.75, indicating uncontrolled asthma. Following regular ICS for 6 weeks, FeNO and ACQ scores were reassessed. <b>Results:</b> Patients (n=20, median age 36yrs (range:18-71), 7F;13M) had moderate BHR to mannitol (GeoMean PD₁₅ 81mg, 95% CI 52-126), mean FeNO of 32ppb and an ACQ score of 1.75. The majority (85%) had FeNO &lt;47ppb (8 normal; 9 borderline). ICS for 6 weeks afforded a clinically significant decrease in ACQ score to 0.86 (Δ0.89, p&lt;0.001), associated with a reduction in mean FeNO to 18 ppb (p=0.007). Clinical benefit was also seen when the normal/borderline (&lt;47ppb) group were analysed separately with a decrease in ACQ score to 0.95 (Δ0.81, p&lt;0.001). <b>Conclusion:</b> Clinically significant benefit to ICS was observed in patients with uncontrolled asthma and BHR to mannitol with borderline to normal FeNO levels. This suggests there is a low FeNO phenotype in asthma that is ICS sensitive.

Objective Fractional exhaled nitric oxide (FeNO) is a well-established measure of allergic airway inflammation and possible useful adjunct disease management tool. We investigated the association of baseline and follow-up FeNO measurements with disease burden in minority children with persistent asthma. Methods A retrospective chart review was conducted on 352 African American and Hispanic children seen at an urban Asthma Center in Bronx, NY. Demographic, clinical characteristics, and pulmonary function tests (PFTs) were compared between children with low, intermediate, and high baseline FeNO levels. Among 95 children with subsequent follow up visits, associations of change in FeNO with demographics, clinical characteristics, and PFTs were examined using mixed effects linear regression models. Results A higher proportion of children with intermediate (54%) and high FeNO (58%) levels had lower airways obstruction compared to those with low FeNO levels (33%). Children with intermediate FeNO levels had more annual hospitalizations (2.8 ± 6.2) compared to those with low and high FeNO levels (1.3 ± 2.8 and 1.3 ± 2.5). These associations did not differ between ethnicities. An increase in FeNO over time was associated with higher BMI z-scores (β = 6.2, 95% CI: 1.0 to 11.4) and two or more hospitalizations in the past year (β = 16.1, 95% CI: 1.5 to 30.8). Conclusions Intermediate and high FeNO levels are associated with lower airways obstruction and hospitalizations. Initial and serial FeNO measurements can be a useful adjunctive tool in identifying asthma-related morbidity in urban African American and Hispanic children.