Haemophilus influenzae Outer membrane vesicles inhalation contributes to steroid-resistant asthma

Asthma is the most common chronic respiratory disease. Asthma that cannot be well controlled by steroid treatment is called steroid-resistant asthma. Steroid-resistant asthma accounts for only 5% of all asthma cases, but it accounts for 80% of asthma healthcare costs. Nontypeable Haemophilus influenzae (NTHi), as a Gram-negative bacterium, can release outer membrane vesicles (OMVs) and transfer biomolecules to host cells and the external environment by carrying lipopolysaccharides, proteins, peptidoglycans, outer membrane proteins, cell wall components, proteins, nucleic acids, ion metabolites, and signaling molecules. Thus, it plays a role in obtaining nutrition, stress, toxin delivery, adhesion, host immune surveillance evasion, and host immune response regulation. It becomes an essential way in bacterial pathogenesis. To further clarify whether NTHi OMVs could be inhaled to induce steroid-resistant asthma, we isolated and purified NTHi OMVs. In vivo experiments showed that NTHi OMVs could be inhaled and enter airway epithelial cells. Cosensitization with OVA induces steroid-resistant asthma in mice. Furthermore, through high-throughput sequencing, we found that the NTHi OMVs and OVA co-sensitized mice had significantly enriched inflammatory and immune-related signaling pathways, and the transcription and secretion of IL-1β were increased was the potential cause of SRA. mice were atomized with NTHi OMVs on day-10 and intraperitoneal injected with 50 μg OVA (Sigma) in 200 μL 0.9% saline on day 0. On days 12-15 of the experiment, mice in the OVA+NTHi OMVs group were given 15ml 2% OVA atomization, while mice in the Control group were given an equal amount of 0.9% saline atomization. Lung tissue was obtained for sequencing