SEVERE asthma is a complex and heterogeneous condition, and understanding its underlying mechanisms remains critical for effective management. Recent research has shed light on the airway microbiome’s role in severe asthma, particularly focusing on ‘type-2 low’ neutrophilic asthma, a phenotype that lacks the eosinophilic inflammation typical of other asthma types.
The study employed long-read metagenomic sequencing to analyse sputum and nasal lavage samples from adult asthma cohorts, integrating species-level data with clinical parameters and airway inflammatory mediators.
Findings indicated that while the microbiomes in healthy individuals and those with mild asthma exhibited comparable diversity, 23% of patients with severe asthma had a microbiome dominated by a single pathogenic species. The most common pathogens identified were Haemophilus influenzae, Moraxella catarrhalis, and Streptococcus pneumoniae. In particular, neutrophilic asthma was associated with a higher prevalence of these organisms and elevated levels of type-1 cytokines, indicating a strong immune response. Notably, a correlation was found between H. influenzae load and specific inflammatory markers such as Eosinophil Cationic Protein and IL-10.
Moreover, the microbiomes of the upper and lower airways were distinct, challenging the concept of ‘one airway, one disease’, suggesting that the pathogenic profiles and immune responses in the airways may differ significantly based on the location of the sample. The implications of these findings are profound, as they indicate that a pathogen-dominant airway microbiome is a common treatable trait in severe asthma. It also suggests the potential for targeted therapies, such as long-term macrolide antibiotics, to improve patient outcomes.
The study emphasises the need for personalised approaches in treating severe asthma, considering the unique microbial landscape and immune responses of each patient. Continued research is vital to unravel the complex interactions between the airway microbiome and immune system, ultimately paving the way for more effective management strategies for severe asthma.
Katie Wright, EMJ
Reference
Jabeen MF et al. Species-level, metagenomic and proteomic analysis of microbe-immune interactions in severe asthma. Allergy. 2024;DOI:10.1111/all.16269.
