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M.tb adaptation to human alveolar lining fluid (ALF)

ABSTRACT: Superbugs such as drug-resistant Mycobacterium tuberculosis (DR-M.tb) poses a serious global health threat. Upon infection, M.tb reaches the alveolar space and comes in close contact with soluble components of the human alveolar lining fluid (ALF) for an uncertain period of time prior to and following its encounter with alveolar compartment cells. Homeostatic ALF hydrolases, which main function is maintaining lung health, modify the M.tb cell envelope, driving M.tb-host cell interactions. Still, the contribution of human ALF to M.tb adaptation to the host during infection is poorly understood. Here, we exposed 4 M.tb strains (H37Rv, HN878, CDC1551, W-7642) with different levels of virulence, transmissibility, and drug resistance to human ALF for shorter (15 min) and longer (12 h) periods of time. RNA sequencing was performed to determine the strains’ transcriptional profiles in response to ALF exposure. Gene expression analysis showed a clear temporal and strain-specific adaptation to human ALF. When comparing ALF-exposed vs. unexposed bacteria for each M.tb strain, differential expression (DE) analysis revealed a total of 397 DE genes associated with lipid metabolism, cell envelope and processes, intermediary metabolism and respiration, and regulatory proteins, among others. Most DE was detected at 12 h post-ALF exposure, with DR-M.tb strain W-7642 having the highest number of DE genes. Interestingly, genes from the KstR2 regulon, which controls the degradation of cholesterol C and D rings, were significantly upregulated early in all strains post-ALF exposure. These results indicate that M.tb-ALF contact (15 min to 12 h prior to M.tb recognition by host cells in the alveolar space) drives global metabolic and physiologic changes in M.tb during the initial stages of the infection, with potential implications in infection outcome.

ORGANISM(S): Mycobacterium tuberculosis

PROVIDER: GSE228998 | GEO | 2024/02/20

REPOSITORIES: GEO

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Project description:Human alveolar macrophages (HAM) are primary bacterial niche and immune response cells during Mycobacterium tuberculosis (M.tb) infection, and human blood monocyte-derived macrophages (MDM) are a model for investigating M.tb-macrophage interactions. Here, we use a targeted RNA-Seq method to measure transcriptome-wide changes in RNA expression patterns of freshly obtained HAM (used within 6 h) and 6 day cultured MDM upon M.tb infection over time (2, 24 and 72 h), in both uninfected and infected cells from three donors each. The Ion AmpliSeq™ Transcriptome Human Gene Expression Kit (AmpliSeq) uses primers targeting 18,574 mRNAs and 2,228 non-coding RNAs (ncRNAs) for a total of 20,802 transcripts. AmpliSeqTM yields highly precise and reproducible gene expression profiles (R2 >0.99). Taking advantage of AmpliSeq’s reproducibility, we establish well-defined quantitative RNA expression patterns of HAM versus MDM, including significant M.tb-inducible genes, in networks and pathways that differ in part between MDM and HAM. A similar number of expressed genes are detected at all time-points between uninfected MDM and HAM, in common pathways including inflammatory and immune functions, but canonical pathway differences also exist. In particular, at 2 h, multiple genes relevant to the immune response are preferentially expressed in either uninfected HAM or MDM, while the HAM RNA profiles approximate MDM profiles over time in culture, highlighting the unique RNA expression profile of freshly obtained HAM. MDM demonstrate a greater transcriptional response than HAM upon M.tb infection, with 2 to >10 times more genes up- or down-regulated. The results identify key genes involved in cellular responses to M.tb in two different human macrophage types. Follow-up bioinformatics analysis indicates that approximately 30% of response genes have expression quantitative trait loci (eQTLs in GTEx), common DNA variants that can influence host gene expression susceptibility or resistance to M.tb, illustrated with the TREM1 gene cluster and IL-10.

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M.tb adaptation to human alveolar lining fluid (ALF)

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