Abstract Rationale Non-tuberculous Mycobacterial Lung-Disease (NTM-LD) affects subjects with underlying pulmonary conditions, thus implicating the host immune response. Protracted treatments have necessitated the discovery of host-directed adjunctive therapies. Using a bronchiectasis cohort and a murine model, we studied the meta-transcriptome and host transcriptome signatures that can potentially be targeted in NTM+ bronchiectasis. Methods BALF samples were collected from 200 subjects undergoing clinically indicated bronchoscopies (46% NTM+). All samples underwent metatranscriptome and bulk host transcriptome sequencing. EdgeR and Ingenuity Pathway Analysis (IPA) were used for comparative analyses. Disease severity for 182/200 subjects was determined with the Bronchiectasis Severity Index (BSI). Given lower airway enrichment with oral commensals in our human cohort, we developed a murine NTM infection (MAC101) + micro-aspiration model (Fig. 1E) to study the murine host transcriptome. Results 60 subjects had low BSI score, 81 had moderate score and 41 had severe score. Analysis of the host transcriptome identified 1500 differentially enriched genes (DEGs) in the severe/high BSI group, regardless of NTM status (Fig. 1A). IPA showed up-regulation of PI3K/AKT, neutrophil degranulation, neutrophil extracellular trap (NET), IL-17, IL-1 and MAP kinases in the severe/high BSI groups, both in the full cohort and in NTM+ subjects (Fig 1B-C). Subjects with a high BSI score had significantly lower alpha diversity and higher bacterial burden. EdgeR analysis of metatranscriptome sequencing showed enrichment with Streptococcus, Staphylococcus, Achromobacter, Enterobacter, Bacteroides, Porphyromonas and Influenza A virus in the high group (Fig. 1D). Analysis of the host transcriptome in the murine NTM/micro-aspiration model showed a progressive increase in DEGs with time (1600 upregulated with NTM at 6w and 2200 with NTM+MOC at 6w, Fig. 1F-G). IPA showed significant up-regulation of NET, Th1, M1 macrophages, NK cell and IFNγ at 6w in both NTM and NTM+MOC murine groups (Fig 1H). A heat map of relative gene expression (Z-score-normalized log-fold-change) showed significant up-regulation of several genes involved in NET formation (Txnip, Tigit, Lag3, Ctla4, Havcr2, Cd274, Itgam, Tlr7, Tlr2, Itgb2, Cybb), tryptophan metabolism (Ido, Kmo, Kynu, Ahr) and AKT/mTOR/HIF-1α pathways (Hif1a, Rps6kb1) in both NTM and NTM+MOC murine groups at 6w, compared to 2w (Fig. 1I). Conclusions Lower airway differential gene expression in human and murine NTM-LD is driven by both disease severity and disease duration. Up-regulation of several canonical pathways that can be targeted for adjunctive intervention was noted for NET, IL-17, IL-1 and MAP kinases in the lower airways of both our human cohort and mouse model. This abstract is funded by: American Thoracic Society, NIH
Singh et al. (Fri,) studied this question.