WS11.04Unraveling the pathogenicity of mycobacterium abscessus in cystic fibrosis pulmonary epithelial cell and mouse models of respiratory infection

Objectives

Mycobacterium abscessus (Mabs) infections are common in people with cystic fibrosis (PwCF), with outcomes ranging from asymptomatic to pulmonary disease (Mabs-PD). Dominant clones and morphotypes, smooth(S) or rough(R), are associated with severe cases, but their role in CF lung inflammation is unclear. This study aims to elucidate Mabs pathogenic mechanisms in modulating host defence and inflammatory processes during respiratory infections.

Methods

We analysed 11 Mabs isolates from 5 PwCF across asymptomatic and Mabs-PD phases using morphotype and genome sequencing. Host responses were studied in CF epithelial cell line via transcriptomics and cytokine assays. Two clonal and longitudinal S and R Mabs strains were studied in air-liquid interface (ALI) model of CF human primary bronchial epithelial cells (CF-HBEpC) and mouse infection models, utilizing single-cell(sc) RNA sequencing, and flow cytometry and Visium spatial transcriptomics, respectively.

Results

Epithelial cells infected with Mabs strains revealed that the morphotype primarily drives the host response, as evidenced by over 2,000 differentially expressed genes identified via bulk RNA sequencing and increased IL-6 and IL-8 protein release confirmed by ELISA. Using CF-HBEpC in ALI culture and scRNAseq revealed that basal and secretory cells significantly contribute to the immune response following infection with R and S strains. Specifically, R strain infections upregulated pathways related to cytokine and innate immune responses. We observed that mice chronically infected with R strains had higher inflammatory burden (type 1 and type 17 immunity) compared to mice infected with S strains. Spatial transcriptomics confirmed proinflammatory tissue profiles linked to type 1 immune response.

Conclusion

Our findings suggest that morphotype impacts the interaction between the lung epithelium and bacteria, with R strains inducing stronger type 1 proinflammatory immunity during bacterial persistence.