Dissecting the Mycobacterium bovis BCG Response to Macrophage Infection to Help Prioritize Targets for Anti-Tuberculosis Drug and Vaccine Discovery

Abstract

New strategies are required to reduce the worldwide burden of tuberculosis. Intracellular survival and replication of Mycobacterium tuberculosis after macrophage phagocytosis is a fundamental step in the complex host–pathogen interactions that lead to granuloma formation and disease. Greater understanding of how the bacterium survives and thrives in these environments will inform novel drug and vaccine discovery programs. Here, we use in-depth RNA sequencing of Mycobacterium bovis BCG from human THP-1 macrophages to describe the mycobacterial adaptations to the intracellular environment. We identify 329 significantly differentially regulated genes, highlighting cholesterol catabolism, the methylcitrate cycle and iron homeostasis as important for mycobacteria inside macrophages. Examination of multi-functional gene families revealed that 35 PE/PPE genes and five cytochrome P450 genes were upregulated 24 h after infection, highlighting pathways of potential significance. Comparison of the intracellular transcriptome to gene essentiality and immunogenicity studies identified 15 potential targets that are both required for intracellular survival and induced on infection, and eight upregulated genes that have been demonstrated to be immunogenic in TB patients. Further insight into these new and established targets will support drug and vaccine development efforts.

The functional response of human monocyte-derived macrophages to serum amyloid A and Mycobacterium tuberculosis infection

“…This suggests a clear orientation of Mtb lipid metabolism during early infection of MDMs toward modification of the lipid host-pathogen interface to modulate the host response and promote survival within the phagosome. In previously published analyses of the Mtb transcriptional response to the macrophage environment, the authors suggest rapid remodeling of metabolism to consume lipids, especially cholesterol, and activation of the metylcitrate cycle ameliorating lipid catabolism end-products (90)(91)(92)(93). However, our data show that the early stage of infection is not accompanied by any dramatic changes in central carbon and energy metabolism and shows no transcriptomic signs of lipid consumption/storage or nutrient starvation suggesting that macrophages are still abundant in diverse, readily available carbon sources.…”

Advance in strategies to build efficient vaccines against tuberculosis

“…In this progress, the activation of macrophages is of great importance. Medley et al ( 22 ) discovered potential vaccine and drug targets in the interaction of Mtb and macrophages, such as the enzymes encoded by Cytochrome P450 125 gene and Cytochrome P450 142 gene, which involved in the cholesterol metabolism of Mtb.…”

“…Ganzhu Feng et al developed a recombinant DNA vaccine based on nanoparticles, which contained three T cell epitopes of ESAT-6 and FMS-like tyrosine kinase 3 gene, and was encapsulated by chitosan (CS) nanoparticles. The results showed that the vaccine significantly enhanced T cell immunity and protected against Mtb H37Rv attack ( 22 , 164 ).…”

Long Non-coding RNAs in Tuberculosis: From Immunity to Biomarkers

“…Approximately one-third of the world’s population has a latent TB infection (LTBI), and about 10% can develop active tuberculosis (ATB) with impairment in the immune system ( Pai et al, 2016 ). In the host-pathogen interactions, intracellular survival and replication of Mtb after macrophage phagocytosis leads to an immune response that converges on granuloma formation and/or disease ( McCaffrey et al, 2022 ; Medley et al, 2022 ). The host cells have adopted a series of clearance mechanisms to facilitate intracellular bacterial killing, such as apoptosis, autophagy, inflammation, and macrophage polarization.…”