H influenzae & M catarrhalis in sputum of severe asthma with
inflammasome and neutrophil activation
Abstract
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.