M. tuberculosis curli pili (MTP) facilitates a reduction of microbicidal activity of infected THP-1 macrophages during early stages of infection.

Mycobacterium tuberculosis (M. tuberculosis) curli pili (MTP) is a surface located adhesin, which is involved in the initial point-of-contact between the pathogen and the host. Host-pathogen interaction is essential for establishing infection. M. tuberculosis has the ability to infect various host lung cell types, which includes both the epithelial cells and macrophages, and subsequent differences in their cellular function will be evident in their metabolic profiles. Understanding the differences between these cell types and their individual metabolic response to M. tuberculosis infection, with and without the presence of the MTP, will aid to better elucidate the role of this adhesin in modulating metabolic pathways during infection. This may further contribute to the development of improved diagnostic and therapeutic interventions, much needed at present in order to improve control the global tuberculosis (TB) epidemic. This study used a two-dimensional gas chromatography coupled with time-of-flight mass spectrometry (GC×GC-TOFMS) metabolomics approach to compare the metabolite profiles of A549 epithelial cells to that of THP-1 macrophages, infected with M. tuberculosis, in the presence and absence of MTP. Significant metabolites were identified using various univariate and multivariate statistical analysis. A total of 44, 40, 50 and 34 metabolites were differentially detected when comparing the (a) uninfected A549 epithelial cells to uninfected THP-1 macrophages, (b) wild-type infected A549 epithelial cells to wild-type infected THP-1 macrophages, (c) ∆mtp-infected A549 epithelial cells to ∆mtp-infected THP-1 macrophages (d) complement-infected A549 epithelial cells to complement-infected THP-1 macrophages, respectively. These included metabolites that were involved in amino acid metabolism, fatty acid metabolism, general central carbon metabolism, and nucleic acid metabolism. In the absence of the M. tuberculosis MTP adhesin, the THP-1 macrophages predominantly displayed higher concentrations of amino acids and their metabolic intermediates, than the A549 epithelial cells. The deletion of MTP from M. tuberculosis in the host infection models potentially elicited a pro-inflammatory phenotype, particularly in the macrophage model. In the presence of MTP, the metabolite profile changes indicate potential regulation of host defence mechanisms, accompanied by a reduction in microbicidal abilities of host cells. Hence MTP can be considered a virulence factor of M. tuberculosis. Therefore, blocking MTP interaction with the host may facilitate a faster pathogen clearance during the initial stages of infection, and potentially enhance current therapeutic interventions.

M. tuberculosis curli pili (MTP) is associated with alterations in carbon, fatty acid and amino acid metabolism in a THP-1 macrophage infection model.

The initial host-pathogen interaction is crucial for the establishment of infection. An improved understanding of the pathophysiology of Mycobacterium tuberculosis (M. tuberculosis) during macrophage infection can aid the development of intervention therapeutics against tuberculosis. M. tuberculosis curli pili (MTP) is a surface located adhesin, involved in the first point-of-contact between pathogen and host. This study aimed to better understand the role of MTP in modulating the intertwined metabolic pathways of M. tuberculosis and its THP-1 macrophage host. Metabolites were extracted from pelleted wet cell mass of THP-1 macrophages infected with M. tuberculosis wild-type V9124 (WT), Δmtp-deletion mutant and the mtp-complemented strains, respectively, via a whole metabolome extraction method using a 1:3:1 ratio of chloroform:methanol:water. Metabolites were detected by two-dimensional gas chromatography time-of-flight mass spectrometry. Significant metabolites were determined through univariate and multivariate statistical tests and online pathway databases. Relative to the WT, a total of nine and ten metabolites were significantly different in the Δmtp and complement strains, respectively. All nine significant metabolites were found in elevated levels in the Δmtp relative to the WT. Additionally, of the ten significant metabolites, eight were detected in lower levels and two were detected in higher levels in the complement relative to the WT. The absence of the MTP adhesin resulted in reduced virulence of M. tuberculosis leading to alterations in metabolites involved in carbon, fatty acid and amino acid metabolism during macrophage infection, suggesting that MTP plays an important role in the modulation of host metabolic activity. These findings support the prominent role of the MTP adhesin as a virulence factor as well as a promising biomarker for possible diagnostic and therapeutic intervention.