Juma'a R. Al Dulayymi

Molecular structure of the Mycobacterium tuberculosis virulence factor, mycolic acid, determines the elicited inflammatory pattern

Mycolic acids (MAs) occur in the cell wall of Mycobacterium tuberculosis as variable mixtures of different classes and chain lengths. Here, we address the relationship between the structure and its inflammatory function of this virulence factor using single synthetic MA isomers, differing in oxygenation class and cis‐ versus α‐methyl‐trans proximal cyclopropane orientation. Analysis of bronchoalveolar inflammation, lung histopathology and alveolar macrophage transcription revealed a strong dependence on these meromycolic chemistries of mouse pulmonary inflammation in response to intratracheal treatments with MAs. Whereas α‐MA was inert, oxygenated methoxy‐ and keto‐MA with cis‐cyclopropane stereochemistry elicited solid to mild inflammatory responses respectively. In trans‐cyclopropane orientation, methoxy‐MA partially lost its inflammatory activity and keto‐MA exerted anti‐inflammatory alternative activation of alveolar macrophages and counteracted cis‐methoxy‐MA induced airway inflammation. The differential innate immune activities of MAs demonstrated here, dependent on oxygenation class and cis versus α‐methyl‐trans cyclopropane chemistry, identify a novel means for M. tuberculosis to steer host immune responses during infection.

1,2,2-tribromocyclopropanecarboxylic acid and derivatives—Valuable intermediates for four carbon cyclopropane and cyclopropene synthons

Abstract Methyl 1,1,2-tribromocyclopropanecarboxylate is readily available by dibromocyclopropanation of methyl α-bromoacrylate. Reaction with methyllithium at low temperature provides a simple route to methyl 2-bromocyclopropene carboxylate. while modification of the ester group followed by reaction with methyllithium leads to a series of related four-carbon cyclopropenes. The tribromo-ester is also readily converted into 1,1,2,2-tetrabromocyclopropane, a valuable three-carbon cyclopropene synthon.

STRUCTURE BASED INTERFERENCE WITH INSECT BEHAVIOUR - CYCLOPROPENE ANALOGUES OF PHEROMONES CONTAINING Z-ALKENES

Abstract Analogues of the pheromones of three insect species (Musca domestica L., Plutella xylostella L. and Ephestia elutella Hbn.) in which a Z-alkene has been replaced by a 1,2-disubstituted cyclopropene have been synthesised. The analogues interfere with normal mating behaviour for each species.

The synthesis of single enantiomers of a meromycolic acid

Abstract 3-Oxa-2,4-dioxobicyclo[3.1.0]hexane provides a flexible starting material for the preparation of single enantiomers of a meromycolic acid, a long chain fatty acid containing two remote cis-cyclopropanes.

A simple and efficient hydrodehalogenation of 1,1-dihalocyclopropanes***

Abstract 1,1-Dibromo- and 1,1-dichlorocyclopropanes are converted into the corresponding monohalo-cyclopropanes (as mixtures of stereoisomers where appropriate) by reaction with 1.2–1.3 mol. equiv. of ethyl magnesium bromide and a small amount of titanium isopropoxide in ether. In the presence of an excess of ethylmagnesium bromide the product from the dibromide is the non-halogenated cyclopropane.

Generation and trapping of vinylcarbenes at ambient temperature: A route to functionalised vinyl- and allylidene-cyclopropanes

Abstract 1,2-Dehalogenation of tetrachlorocyclopropanes (5, X = Cl, OMe, NPri2, SAllyl) by methyl lithium leads to dichlorocyclopropenes (6, X = Cl, OMe, NPri2, SAllyl); the first two of these react with electron rich and electron poor alkenes at 20°C to give cyclopropanes which are apparently derived by trapping of vinylcarbenes (8) rather than (20). Reaction of the derived vinylcyclopropanes with base leads either to ethyl cyclopropyl ketones or to allylidenecyclopropanes.

Synthesis of putative Δ6-, Δ12- and Δ15-desaturase inhibitors

Cyclopropene fatty acid esters (5) and (6) and (7) have been synthesised as potential structure-based inhibitors of Δ6-, Δ12- and Δ15-desaturases

A direct and a formal trapping of propa-1,2-dienylidene

Abstract 1,2-Dibromocyclopropene ring-opens in solution at 0 – 20 °C to give 1,2-dibromoprop-2-en-1-ylidene, which is trapped by alkenes; the derived cyclopropanes react efficiently with methyl lithium to produce eth-1-en-1-ylidenecyclopropanes. Reaction of the cyclopropene with methyl lithium in ether in the presence of an alkene leads to the same allenes by trapping of the parent allenic carbene, propa-1,2-dienylidene, albeit in low yield

Inflammatory Properties and Adjuvant Potential of Synthetic Glycolipids Homologous to Mycolate Esters of the Cell Wall of Mycobacterium tuberculosis

The cell wall of mycobacteria is characterised by glycolipids composed of different classes of mycolic acids (MAs; alpha-, keto-, and methoxy-) and sugars (trehalose, glucose, and arabinose). Studies using mutant Mtb strains have shown that the structure of MAs influences the inflammatory potential of these glycolipids. As mutant Mtb strains possess a complex mixture of glycolipids, we analysed the inflammatory potential of single classes of mycolate esters of the Mtb cell wall using 38 different synthetic analogues. Our results show that synthetic trehalose dimycolate (TDM) and trehalose, glucose, and arabinose monomycolates (TMM, GMM, and AraMM) activate bone marrow-derived dendritic cells in terms of the production of pro-inflammatory cytokines (IL-6 and TNF-α) and reactive oxygen species, upregulation of costimulatory molecules, and activation of NLRP3 inflammasome by a mechanism dependent on Mincle. These findings demonstrate that Mincle receptor can also recognise pentose esters and seem to contradict the hypothesis that production of GMM is an escape mechanism used by pathogenic mycobacteria to avoid recognition by the innate immune system. Finally, our experiments indicate that TMM and GMM, as well as TDM, can promote Th1 and Th17 responses in mice in an OVA immunisation model, and that further analysis of their potential as novel adjuvants for subunit vaccines is warranted.

CD1b-restricted GEM T cell responses are modulated by Mycobacterium tuberculosis mycolic acid meromycolate chains

Significance Tuberculosis is a major global pandemic responsible for more deaths than any other infectious disease, yet no effective vaccine exists. Here, we demonstrate CD1b expression within human tuberculous granulomas, supporting a role for CD1b lipid antigen presentation in host immunity to infection. CD1b presents mycolates, the dominant Mycobacterium tuberculosis (Mtb) cell wall lipid class and key virulence factors, to αβ T cells. We reveal that mycolate tail moieties, distal to the head group, are antigenic determinants for the conserved human germline-encoded mycolyl lipid-reactive (GEM) T cell receptors (TCRs). Computational simulations suggest a putative mechanism whereby lipid-ligand dynamics within CD1b regulate GEM-TCR activity. This work provides insights for the development of major histocompatibility complex (MHC)-independent Mtb lipid vaccines, including those that target GEM T cells. Tuberculosis (TB), caused by Mycobacterium tuberculosis, remains a major human pandemic. Germline-encoded mycolyl lipid-reactive (GEM) T cells are donor-unrestricted and recognize CD1b-presented mycobacterial mycolates. However, the molecular requirements governing mycolate antigenicity for the GEM T cell receptor (TCR) remain poorly understood. Here, we demonstrate CD1b expression in TB granulomas and reveal a central role for meromycolate chains in influencing GEM-TCR activity. Meromycolate fine structure influences T cell responses in TB-exposed individuals, and meromycolate alterations modulate functional responses by GEM-TCRs. Computational simulations suggest that meromycolate chain dynamics regulate mycolate head group movement, thereby modulating GEM-TCR activity. Our findings have significant implications for the design of future vaccines that target GEM T cells.