Daily Respiratory Research Analysis
Three papers advance respiratory science and care: a global GWAS identified FOXP4 as a susceptibility locus for long COVID independent of severe disease; single-cell spatial transcriptomics revealed proinflammatory airway ecosystems and targetable interactions in asthma; and a multicohort study showed plasma soluble ST2 predicts 30-day mortality in acute respiratory failure and reflects extrapulmonary organ dysfunction.
Summary
Three papers advance respiratory science and care: a global GWAS identified FOXP4 as a susceptibility locus for long COVID independent of severe disease; single-cell spatial transcriptomics revealed proinflammatory airway ecosystems and targetable interactions in asthma; and a multicohort study showed plasma soluble ST2 predicts 30-day mortality in acute respiratory failure and reflects extrapulmonary organ dysfunction.
Research Themes
- Genetic susceptibility and mechanisms in long COVID (FOXP4)
- Spatially organized inflammatory ecosystems in asthma airways
- Biomarker-based risk stratification in acute respiratory failure (IL-33/ST2 axis)
Selected Articles
1. Genome-wide association study of long COVID.
A global GWAS across 24 cohorts identified FOXP4 as a susceptibility locus for long COVID, independent of previously reported associations with severe COVID-19. The signal replicated in an independent dataset, and FOXP4’s known role in lung biology underscores respiratory mechanisms in long COVID.
Impact: This is the largest genetic analysis of long COVID to date, providing a robust and replicated susceptibility locus and pointing to lung-specific biology.
Clinical Implications: Although not immediately practice-changing, FOXP4 highlights biologic pathways for risk stratification and therapeutic target discovery in long COVID, potentially informing future precision interventions.
Key Findings
- FOXP4 was significantly associated with long COVID across 24 studies (6,450 cases vs 1,093,995 controls).
- The FOXP4 association was replicated in an independent dataset (9,500 cases and 798,835 controls).
- The association was independent of FOXP4’s prior link to severe COVID-19, implicating distinct mechanisms.
- FOXP4’s role in lung physiology/pathology links long COVID susceptibility to respiratory tissue biology.
Methodological Strengths
- Very large sample size across 24 international cohorts with replication
- Rigorous GWAS methodology with cross-study harmonization
Limitations
- Phenotype heterogeneity across cohorts may introduce misclassification
- Observational genetic associations cannot establish causality or effect size in clinical terms
Future Directions: Functional studies to delineate FOXP4-driven pathways in airway epithelium and lung tissue; integration with proteomic/epigenomic datasets and prospective cohorts for risk prediction.
Infections can lead to persistent symptoms and diseases such as shingles after varicella zoster or rheumatic fever after streptococcal infections. Similarly, severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) infection can result in long coronavirus disease (COVID), typically manifesting as fatigue, pulmonary symptoms and cognitive dysfunction. The biological mechanisms behind long COVID remain unclear. We performed a genome-wide association study for long COVID including up to 6,450 long COVID cases and 1,093,995 population controls from 24 studies across 16 countries. We discovered an association of FOXP4 with long COVID, independent of its previously identified association with severe COVID-19. The signal was replicated in 9,500 long COVID cases and 798,835 population controls. Given the transcription factor FOXP4's role in lung physiology and pathology, our findings highlight the importance of lung function in the pathophysiology of long COVID.
2. A single-cell spatial chart of the airway wall reveals proinflammatory cellular ecosystems and their interactions in health and asthma.
Single-cell spatial transcriptomics mapped discrete proinflammatory ecosystems in the airway wall, characterized by chemokine/alarmin-rich hubs with stromal cell constellations. ACKR1-mediated mediator retention and amphiregulin+ mast cells were prominent, and remodeling persisted in asthma despite anti-inflammatory therapy, highlighting spatially-defined targets.
Impact: Provides an unprecedented spatial atlas of the airway wall linking cellular neighborhoods to inflammatory signaling and persistence in asthma.
Clinical Implications: Targets such as ACKR1 and amphiregulin+ mast cells within defined hubs may enable spatially informed precision therapies and biomarkers for disease activity beyond bulk measures.
Key Findings
- Identified discrete proinflammatory cellular ecosystems (chemokine/alarmin-rich hubs) within airway wall spatial niches.
- ACKR1 localized retention of immune mediators and amphiregulin-expressing mast cells were prominent features of inflammatory hubs.
- Asthma mucosa exhibited persistent remodeling with increased proximity among key cell types despite anti-inflammatory treatment.
Methodological Strengths
- State-of-the-art single-cell spatial transcriptomics with cellular neighborhood analysis
- Mechanistic insights linking receptor (ACKR1) function and mast cell amphiregulin to spatial hubs
Limitations
- Sample sizes and cohort heterogeneity are not detailed in the abstract; generalizability may be limited.
- Observational spatial profiling cannot establish causal relationships or treatment effects.
Future Directions: Validate spatial hubs across diverse asthma phenotypes; test therapeutic modulation of ACKR1 and amphiregulin+ mast cells; develop imaging/biopsy-compatible spatial biomarkers.
Determining spatial location of cells within tissues gives vital insight into the interactions between resident and inflammatory cells and is a critical factor for uncoupling the mechanisms driving disease. Here, we apply single-cell spatial transcriptomics to reveal the airway wall landscape in health and during asthma. We identified proinflammatory cellular ecosystems that exist within discrete spatial niches in healthy and asthma samples. These cellular hubs are characterized by a high level of chemokine and alarmin expression, along with unique combinations of stromal cells. Mechanistically, we demonstrated that receptors, such as ACKR1, retain immune mediators locally, while amphiregulin-expressing mast cells are prominent within these proinflammatory hubs. Despite anti-inflammatory treatments, the asthma airway mucosa exhibited a distinct remodeling program within these cellular ecosystems, marked by increased proximity between key cell types. This study provides an unprecedented view of the topography of the airway wall, revealing distinct, specific ecosystems within spatial niches to target for therapeutic intervention.
3. Plasma Levels of Soluble ST2 Reflect Extrapulmonary Organ Dysfunction and Predict Outcomes in Acute Respiratory Failure.
Across five cohorts (n=1,432), plasma sST2 was markedly higher than lower respiratory tract levels and weakly correlated between compartments, indicating a systemic source. Elevated plasma sST2 associated with extrapulmonary organ dysfunction and hyperinflammatory subphenotypes, and independently predicted 30-day mortality in ARF.
Impact: Defines sST2 as a robust, systemic biomarker of ARF prognosis beyond oxygenation metrics and links to the IL-33/ST2 pathway.
Clinical Implications: Plasma sST2 could be integrated into ARF risk stratification and monitoring, and the IL-33/ST2 axis merits evaluation as a therapeutic target to mitigate multiorgan dysfunction.
Key Findings
- Plasma sST2 was >19-fold higher than LRT levels with weak intercompartment correlation, suggesting a systemic source.
- Elevated plasma sST2 associated with extrapulmonary organ dysfunction and a hyperinflammatory ARF subphenotype, not with hypoxemia.
- Plasma sST2 independently predicted 30-day mortality after adjustment; nonsurvivors had persistently elevated sST2 over the first 2 weeks.
Methodological Strengths
- Multicenter design with five cohorts including COVID and non-COVID ARF
- Parallel plasma and lower respiratory tract measurements with adjusted analyses and longitudinal follow-up
Limitations
- Observational design with potential residual confounding and assay heterogeneity across cohorts
- No interventional testing of IL-33/ST2 pathway modulation
Future Directions: Prospective validation of sST2-guided management strategies and interventional trials targeting the IL-33/ST2 axis in ARF.
OBJECTIVES: Soluble ST2 (sST2), a decoy receptor for the alarmin interleukin-33 (IL-33), has been implicated in adverse clinical outcomes in acute respiratory failure (ARF). We evaluated sST2 distribution across diverse cohorts of patients with different etiologies of ARF, compared plasma and lower respiratory tract (LRT) concentrations, and examined associations with individual organ dysfunction, biological subphenotypes, and outcomes. DESIGN: Observational study. SETTING: Multicenter cohorts of ARF patients. PATIENTS: A total of 1432 ARF patients, including 863 non-COVID and 569 COVID-19 cases, from five cohorts. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: sST2 levels were measured in plasma and LRT specimens (when available) and analyzed for associations with ARF etiology, severity, organ dysfunction, systemic host response, subphenotypes, and 30-day mortality. Plasma sST2 levels were higher in non-COVID ARF patients compared with COVID-19 patients ( p < 0.05) and were markedly elevated compared with LRT levels (> 19-fold), with weak intercompartmental correlation. Elevated plasma sST2 levels were associated with extrapulmonary organ dysfunction and a hyperinflammatory ARF subphenotype but not with respiratory indices, including hypoxemia. Plasma sST2 independently predicted 30-day mortality in pooled cohort data, adjusted for age, sex, and illness severity. In longitudinal measurements, nonsurvivors had persistently elevated plasma sST2 levels in the first 2 weeks of critical illness compared with survivors. CONCLUSIONS: Plasma sST2 levels independently predict outcomes in ARF and are strongly associated with extrapulmonary organ dysfunction. The weak correlation between plasma and LRT sST2 levels suggests a predominantly systemic source. These findings highlight the potential of the IL-33/ST2 axis as a therapeutic target and warrant further investigation into its role in multiple organ dysfunction in ARF.