Structural studies of cord factors from Mycobacterium simiae related to the capacity for tumour necrosis factor alpha (α-TNF) induction

Polysaccharides and glycolipids of Mycobacterium tuberculosis and their induced immune responses

Tuberculosis (TB) is a chronic infectious disease mainly caused by Mycobacterium tuberculosis (M. tuberculosis). The structures of polysaccharides and glycolipids at M. tuberculosis cell wall vary among different strains, which affect the physiology and pathogenesis of mycobacteria by activating or inhibiting innate and acquired immunity. Among them, some components such as lipomannan (LM) and lipoarabinomannan (LAM) activate innate immunity by recognizing some kinds of pattern recognition receptors (PRRs) like Toll-like receptors, while other components like mannose-capped lipoarabinomannan (ManLAM) could prevent innate immune responses by inhibiting the secretion of pro-inflammatory cytokines and maturation of phagosomes. In addition, many glycolipids can activate natural killer T (NKT) cells and CD1-restricted T cells to produce interferon-γ (IFN-γ). Furthermore, humoral immunity against cell wall components, such as antibodies against LAM, plays a role in immunity against M. tuberculosis infection. Cell wall polysaccharides and glycolipids of M. tuberculosis have potential applications as antigens and adjuvants for novel TB subunit vaccines.

Mycobacterium alvei (ω-1)-methoxy mycolic acids: Absolute stereochemistry and synthesis

Cells of Mycobacterium alvei are known to contain a unique set of mycolic acids with a (ω-1)-methoxy group; although the various enzymes in the biosynthesis of other types of mycolic acid have been widely studied, the biosynthetic route to this substituent is unclear. We now define the stereochemistry of the (ω-1)-methoxy fragment as R, and describe the synthesis of a major R-(ω-1)-methoxy-mycolic acid and its sugar esters, and of two natural M. alvei diene mycolic acids.

Lipid metabolism in mycobacteria--Insights using mass spectrometry-based lipidomics

Diseases including tuberculosis and leprosy are caused by species of the Mycobacterium genus and are a huge burden on global health, aggravated by the emergence of drug resistant strains. Mycobacteria have a high lipid content and complex lipid profile including several unique classes of lipid. Recent years have seen a growth in research focused on lipid structures, metabolism and biological functions driven by advances in mass spectrometry techniques and instrumentation, particularly the use of electrospray ionization. Here we review the contributions of lipidomics towards the advancement of our knowledge of lipid metabolism in mycobacterial species.

Cord factors from atypical mycobacteria (Mycobacterium alvei, Mycobacterium brumae) stimulate the secretion of some pro-inflammatory cytokines of relevance in tuberculosis

The ability to induce several cytokines relevant to tuberculosis (TNF-α, IL-1β, IL-6, IL-12p40 and IL-23) by cord factor (trehalose dimycolate) from Mycobacterium alvei CR-21(T) and Mycobacterium brumae CR-270(T) was studied in the cell lines RAW 264.7 and THP-1, and compared to the ability of cord factor from Mycobacterium tuberculosis H37Rv, where this glycolipid appears to be implicated in the pathogenesis of tuberculosis. Details of the fine structure of these molecules were obtained by NMR and MS. The mycoloyl residues were identified as α and (ω-1)-methoxy in M. alvei CR-21(T) and α in M. brumae CR-270(T); in both cases they were di-unsaturated instead of cyclopropanated as found in M. tuberculosis. In RAW 264.7 cells, cord factors from M. alvei CR-21(T), M. brumae CR-270(T) and M. tuberculosis differed in their ability to stimulate IL-6, the higher levels corresponding to the cord factor from M. tuberculosis. In THP-1 cells, a similar overall profile of cytokines was found for M. alvei CR-21(T) and M. brumae CR-270(T), with high proportions of IL-1β and TNF-α, and different from M. tuberculosis, where IL-6 and IL-12p40 prevailed. The data obtained indicate that cord factors from the atypical mycobacteria M. alvei CR-21(T) and M. brumae CR-270(T) stimulated the secretion of several pro-inflammatory cytokines, although there were some differences with those of M. tuberculosis H37Rv. This finding seems to be due to their particular mycoloyl substituents and could be of interest when considering the potential adjuvanticity of these molecules.