Metabolic transcriptional profile of virulent Mtb-infected human AM

Mycobacterium tuberculosis (Mtb)-induced shifts in macrophage metabolism are an accepted central infection paradigm. Mtb-infected murine lung tissue exhibits gene expression changes consistent with classic Warburg metabolism and Mtb-infected murine macrophages undergo TCA cycle remodeling. Human macrophages also respond energetically to Mtb infection, however, interestingly the phenotypic nature of this response appears to vary depending on the viability of infection. Despite the overwhelming consensus that metabolic changes are critical to the host response to infection, we have little understanding of the metabolic transcriptional landscape of virulent Mtb-infected human alveolar macrophages (AM), the sentinel pulmonary immune cell during Mtb infection. Further still, whether the human AM undergoes glycolytic reprogramming and TCA cycle remodeling during virulent Mtb infection remains undefined; as is suggested to occur in circulating Mtb-infected human macrophages. Here, we aimed to characterise the metabolic transcriptional profile of virulent Mtb-infected human AM. We hypothesised that infection would induce the transcriptome of Warburg metabolism (characterised by aerobic glycolysis), TCA cycle remodeling, and reduce expression of genes involved in mitochondrial oxidative phosphorylation (OXPHOS). Human alveolar macrophages (AM) were harvested from 6 volunteers (3 never-smokers and 3 ex-smokers), who were undergoing clinically indicated bronchoscopy. AM were infected with live virulent H37Rv Mtb for 24 h using a multiplicity of infection of 1-10 bacilli per cell. AM were then lysed, and total RNA was collected and purified using silica-membrane column centrifugation. MTB-induced changes in gene expression were determined using the NanoString nCounter Platform Metabolic Pathways Panel and data were analysed using the NanoString nSolver Data Analysis software.