Discrimination of intact mycobacteria at the strain level: a combined MALDI-TOF MS and biostatistical analysis

New methodologies for surveillance and identification of Mycobacterium tuberculosis are required to stem the spread of disease worldwide. In addition, the ability to discriminate mycobacteria at the strain level may be important to contact or source case investigations. To this end, we are developing MALDI-TOF MS methods for the identification of M. tuberculosis in culture. In this report, we describe the application of MALDI-TOF MS, as well as statistical analysis including linear discriminant and random forest analysis, to 16 medically relevant strains from four species of mycobacteria, M. tuberculosis, M. avium, M. intracellulare, and M. kansasii. Although species discrimination can be accomplished on the basis of unique m/z values observed in the MS fingerprint spectrum, discrimination at the strain level is predicted on the relative abundance of shared m/z values among strains within a species. For the 16 mycobacterial strains investigated in the present study, it is possible to unambiguously identify strains within a species on the basis of MALDI-TOF MS data. The error rate for classification of individual strains using linear discriminant analysis was 0.053 using 37 m/z variables, whereas the error rate for classification of individual strains using random forest analysis was 0.023 using only 18 m/z variables. In addition, using random forest analysis of MALDI-TOF MS data, it was possible to correctly classify bacterial strains as either M. tuberculosis or non-tuberculous with 100% accuracy.

Mycobacterial Lipomannan Induces Granuloma Macrophage Fusion via a TLR2-Dependent, ADAM9- and β1Integrin-Mediated Pathway

Tuberculous granulomas are the sites of interaction between the host response and the tubercle bacilli within infected individuals. They mainly consist of organized aggregations of lymphocytes and macrophages (Mf). A predominant role of mycobacterial envelope glycolipids in granulomas formation has been recently emphasized, yet the signaling events interfering with granuloma cell differentiation remain elusive. To decipher this molecular machinery, we have recently developed an in vitro human model of mycobacterial granulomas. In this study, we provide evidence that the mycobacterial proinflammatory phosphatidyl-myo-inositol mannosides and lipomannans (LM), as well as the anti-inflammatory lipoarabinomannan induce granuloma formation, yet only the proinflammatory glycolipids induce the fusion of granuloma Mf into multinucleated giant cells (MGC). We also demonstrate that LM induces large MGC resembling those found in vivo within the granulomas of tuberculosis patients, and that this process is mediated by TLR2 and is dependent on the beta(1) integrin/ADAM9 cell fusion machinery. Our results demonstrate for the first time that the Mf differentiation stage specifically occurring within granulomatous structures (i.e., MGC formation) is triggered by mycobacterial envelope glycolipids, which are capable of inducing the cell fusion machinery. This provides the first characterization of the ontogeny of human granuloma MGC, thus resulting in a direct modulation by a particular mycobacterial envelope glycolipid of the differentiation process of granuloma Mf.

MS/MS approach for characterization of the fatty acid distribution on mycobacterial phosphatidyl-myo-inositol mannosides

Phosphatidyl-myo-inositol mannosides (PIM) are not only important structural components of the mycobacterial envelope but also are major non-peptidic antigens of the host innate and acquired immune responses. Indeed, they are ligands of TLR-2 and they activate CD1-restricted T lymphocytes. In addition, PIM constitute the basic structure of the lipidic anchor of two lipoglycans, lipomannans and lipoarabinomannans, which are important immunomodulators in the course of tuberculosis. The fatty acyl substituents present on PIM molecules play a crucial role for both their physical properties and biological activities. PIM contain four acylation sites, two on the glycerol, one on a mannose, and one on the myo-inositol units. We propose here an analytical procedure, based on mass spectrometry, to determine the structure of the fatty acids present on each of these different acylation sites. We show that the nature of the fatty acids located on both positions of glycerol can be deduced from IRMPD analysis of negative precursor ions from native PIM species, while the fatty acids located on myo-inositol and mannose units can be identified by MALDI-TOF CID MS of protonated and cationized molecular ions. Thus, the combination of MS/MS data obtained from positive and negative pseudomolecular ions generated by ESI or MALDI appears as a powerful approach for the structural characterization of the PIM acyl form structure.

Mycobacterium kumamotonense Sp. Nov. recovered from clinical specimen and the first isolation report of Mycobacterium arupense in Japan: Novel slowly growing, nonchromogenic clinical isolates related to Mycobacterium terrae complex

Three mycobacterium strains isolated from clinical specimens in Japan were provisionally assigned to the genus Mycobacterium based on their phenotypical characteristics. These isolates were further investigated to determine their specific taxonomic statuses. Mycolic acid analysis and 16S rRNA gene, rpoB, and hsp65 sequence data for the isolates showed that they are most similar to M. terrae complex. DNA-DNA hybridization studies indicated that the three strains were of two species and were distinguishable from M. terrae, M. nonchromogenicum, and M. hiberniae. Therefore, these strains represent two novel species within the genus Mycobacterium. However, one potential new species should have been considered as M. arupense with the 16S rRNA gene and hsp65 sequences similarities of 99.8% and 100% respectively; it was isolated from human specimens in the United States and was proposed in June 2006 as a new species. This report describes the first isolation of M. arupense in Japan, suggesting that the organism is clinically relevant. In addition, we propose the novel species designation Mycobacterium kumamotonense sp. nov. The type strain is CST 7247(T) (=GTC 2729(T), =JCM 13453(T), =CCUG 51961(T)).

Breaking down the wall: Fractionation of mycobacteria

Mycobacterium spp. possess a complex cell envelope that consists of a plasma membrane, a peptidoglycan-arabinogalactan complex which in turn is esterified by mycolic acids that form with other non-bound lipids an asymmetric permeability barrier and an outer layer, also called a capsule in the case of pathogenic species. In order to investigate the functional roles of the cell envelope components, especially those of the major pathogens Mycobacterium tuberculosis and Mycobacterium leprae, it is necessary to fractionate the envelope by breaking the unusual wall that covers these bacteria. To this aim we first compared the efficiency of high pressure (cell disrupter/French press) with those of pathogen-compatible breakage methods such as sonication, bead beater and lysozyme treatment using the non-pathogenic Mycobacterium smegmatis. When the distribution of various specific markers of the cell envelope compartments, which include mycolic acids, arabinose, NADH oxidase activity, cell wall and cytosolic proteins, were determined sonication combined with lysozyme treatment was found to be the best option. The protocol of subcellular fractionation was then validated for pathogenic species by applying the method to Mycobacterium bovis BCG cells, an attenuated strain of the M. tuberculosis complex.

Bacterial capsular antigens. Structural patterns of capsular antigens

Structural patterns of bacterial capsular antigens including capsular polysaccharides and exoglycans are given in this review. In addition, the immunological activity of capsular antigens and their role in type specificity of bacteria are discussed.

Conformational analyses of mycothiol, a critical intracellular glycothiol in Mycobacteria

Intracellular thiols are essential biomolecules, which play several critical roles in living organisms including controlling intracellular redox potential and acting as cofactors for several vital detoxification enzymes including S-transferases and formaldehyde dehydrogenases. The tripeptide gamma-L-glutamyl-L-cysteinylglycine, more commonly known as glutathione, is well known as the major intracellular thiol in eukaryotes and in some bacteria. However, glutathione is absent in the Actinomycetales bacteria such as Mycobacteria and Streptomyces and is believed to be replaced by 1-D-myo-inosityl-2-(N-acetyl-L-cysteinyl)amido-2-deoxy-alpha-D-glucopyranoside, mycothiol, in these organisms. Although much is known about the chemistry and biochemistry of glutathione, currently much less is known concerning mycothiol and its properties. The structure of mycothiol is composed of a glycoside linkage between myo-inositol and D-glucosamine with an N-acetyl-L-cysteine linked to the 2'-amino group of the d-glucosamine moiety. Mycothiol is currently of intense interest due to its essential role in the cellular physiology of Mycobacteria, such as Mycobacterium tuberculosis, and its possible role in antimycobacterial drug resistance. A detailed investigation of its chemistry is therefore essential in ameliorating our knowledge of this key glycothiol, and in shedding additional light on its biochemical role in these pathogenic organisms. This report presents a detailed conformational analysis of mycothiol utilizing a variety of force fields and stochastic search protocols. Cluster analyses of energetically low lying conformations have indicated the presence of several key conformations that are populated in the gas phase and with implicit water solvation. These conformations are compared to recent NMR studies on a derivative of mycothiol. This information should be an important contribution to our basic understanding of the chemistry of this glycothiol and critical in the design of novel inhibitors of pathogen enzymes that require it.

Comparative analysis of iron regulated genes in mycobacteria

Iron dependent regulator, IdeR, regulates the expression of genes in response to intracellular iron levels in M. tuberculosis. Orthologs of IdeR are present in all the sequenced genomes of mycobacteria. We have used a computational approach to identify conserved IdeR regulated genes across the mycobacteria and the genes that are specific to each of the mycobacteria. Novel iron regulated genes that code for a predicted 4-hydroxy benzoyl coA hydrolase (Rv1847) and a protease dependent antibiotic regulatory system (Rv1846c, Rv0185c) are conserved across the mycobacteria. Although Mycobacterium natural-resistance-associated macrophage protein (Mramp) is present in all mycobacteria, it is, as predicted, an iron-regulated gene in only one species, M. avium subsp. paratuberculosis. We also observed an additional iron-regulated exochelin biosynthetic operon, which is present only in non-pathogenic Mycobacterium, M. smegmatis.

Improved efficacy of DNA vaccination against breast cancer by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65

Studies have demonstrated that active-specific immunotherapy has potential for controlling mammary tumor progression. Human chorionic gonadotropin (hCG) is expressed and extremely sensitive, easily detectable and highly correlated with breast cancer. We developed a gene vaccine using a plasmid vector to deliver the six copies of 10-amino acid residues of beta-hCG 109-118 and beta hCG C-terminal 37-amino acid (CTP37). BALB/c female mice were immunized with a combination of pCR-HBc-X6-betahCGCTP37 DNA vaccine and HSP-X6-betahCGCTP37 protein vaccine. pCR-HBc-X6-betahCGCTP37 DNA vaccine were injected intramuscularly three times, on days -46,-25 and -11 and HSP-X6-betahCGCTP37 protein were applied two times, 21 and 14 days before tumor cell challenge. We assessed a combined DNA and protein vaccine for its effect of against murine EMT6 mammary tumor cells. In this study, animals vaccinated DNA vaccination boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65 induced higher avidity antibodies and effectively inhibited the growth of tumor, compared with treatment using DNA alone or BCG priming HSP-X6-betahCGCTP37 protein boosting. The data presented demonstrate that improve immunogenicity of DNA vaccination by boosting with the repeat beta-hCG C-terminal peptide carried by mycobacterial heat-shock protein HSP65, which should prove useful in the development of new DNA vaccine against growth factors for cancer immunotherapy.

rpoB gene sequence-based characterization of emerging non-tuberculous mycobacteria with descriptions of Mycobacterium bolletii sp. nov., Mycobacterium phocaicum sp. nov. and Mycobacterium aubagnense sp. nov

Over the past 10 years, 16S rRNA gene sequencing has contributed to the establishment of more than 45 novel species of non-tuberculous mycobacteria and to the description of emerging mycobacterial infections. Cumulative experience has indicated that this molecular tool underestimates the diversity of this group and does not distinguish between all recognized mycobacterial taxa. In order to improve the recognition of emerging rapidly growing mycobacteria (RGM), rpoB gene sequencing has been developed. Our previous studies have shown that an RGM isolate is a member of a novel species if it exhibits >3 % sequence divergence in the rpoB gene from the type strains of established species. When applied to a collection of 59 clinical RGM isolates, rpoB gene sequencing revealed nine novel isolates (15.3 %) whereas only two isolates (3.4 %) were deemed to be novel by conventional 16S rRNA gene sequence analysis. A polyphasic approach, including biochemical tests, antimicrobial susceptibility analyses, hsp65, sodA and recA gene sequence analysis, DNA G+C content determination and cell-wall fatty acid composition analysis, supported the evidence that these nine isolates represent three novel species. Whereas Mycobacterium phocaicum sp. nov. (type strain N4T = CIP 108542T = CCUG 50185T) and Mycobacterium aubagnense sp. nov. (type strain U8T = CIP 108543T = CCUG 50186T; Mycobacterium mucogenicum group) were susceptible to most antibiotics, Mycobacterium bolletii sp. nov. (type strain BD(T) = CIP 108541T = CCUG 50184T; Mycobacterium chelonae-abscessus group) was resistant to the quinolones, tetracycline, macrolides and imipenem. Only M. bolletii was resistant to clarithromycin. These data illustrate that rpoB gene sequence-based identification is a powerful tool to characterize emerging RGM and mycobacterial infections and provides valuable help in differentiating RGM at both the intra- and interspecies level, thus contributing to a faster and more efficient diagnosis and epidemiological follow-up.

Intact molecular characterization of cord factor (trehalose 6,6'-dimycolate) from nine species of mycobacteria by MALDI-TOF mass spectrometry

Cord factor (trehalose 6,6'-dimycolate, TDM) is an unique glycolipid with a trehalose and two molecules of mycolic acids in the mycobacterial cell envelope. Since TDM consists of two molecules of very long branched-chain 3-hydroxy fatty acids, the molecular mass ranges widely and in a complex manner. To characterize the molecular structure of TDM precisely and simply, an attempt was made to determine the mycolic acid subclasses of TDM and the molecular species composition of intact TDM by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry for the first time. The results showed that less than 1 microg mycolic acid methyl ester of TDM from nine representative species of mycobacteria and TDM from the same species was sufficient to obtain well-resolved mass spectra composed of pseudomolecular ions [M+Na]+. Although the mass ion distribution was extremely diverse, the molecular species of each TDM was identified clearly by constructing a molecular ion matrix consisting of the combination of two molecules of mycolic acids. The results showed a marked difference in the molecular structure of TDM among mycobacterial species and subspecies. TDM from Mycobacterium tuberculosis (H37Rv and Aoyama B) showed a distinctive mass pattern and consisted of over 60 molecular ions with alpha-, methoxy- and ketomycolate. TDM from Mycobacterium bovis BCG Tokyo 172 similarly showed over 35 molecular ions, but that from M. bovis BCG Connaught showed simpler molecular ion clusters consisting of less than 35 molecular species due to a complete lack of methoxymycolate. Mass ions due to TDM from M. bovis BCG Connaught and Mycobacterium kansasii showed a biphasic distribution, but the two major peaks of TDM from M. kansasii were shifted up two or three carbon units higher compared with M. bovis BCG Connaught. Within the rapid grower group, in TDM consisting of alpha-, keto- and wax ester mycolate from Mycobacterium phlei and Mycobacterium flavescens, the mass ion distribution due to polar mycolates was shifted lower than that from the Mycobacterium avium-intracellulare group. Since the physico-chemical properties and antigenic structure of mycolic acid of TDM affect the host immune responses profoundly, the molecular characterization of TDM by MALDI-TOF mass analysis may give very useful information on the relationship of glycolipid structure to its biological activity.

The binding of mycolic acids to galectin-3: a novel interaction between a host soluble lectin and trafficking mycobacterial lipids?

Understanding the molecular mechanism of host-pathogen interactions is the basis for drug design and vaccine development. The fine composition of mycolic acids (MA), the major constituents of Mycobacterium tuberculosis (Mtb) cell envelope, as well as other cell wall-associated lipids, contribute to determine the virulence of a given strain. However, endogenous receptors for mycolic acids on susceptible cells exposed to mycobacterial infections have not been fully identified. Here, we show that galectin-3, a multifunctional beta-galactoside binding lectin present mainly in the cytoplasm of inflammatory cells and also present on the cell surface, can recognize mycobacterial mycolic acids. MA can inhibit the lectin self-association but not its carbohydrate-binding abilities and can selectively interfere in the interaction of the lectin with its receptors on temperature-sensitive dendritic cell line, suggesting that galectin-3 could be involved in the recognition of trafficking mycolic acids and participate in their interaction with host cells.

Altered expression profile of mycobacterial surface glycopeptidolipids following treatment with the antifungal azole inhibitors econazole and clotrimazole

The azole antifungal drugs econazole and clotrimazole are known cytochrome P450 enzyme inhibitors. This study shows that these drugs are potent inhibitors of mycobacterial growth and are more effective against Mycobacterium smegmatis than isoniazid and ethionamide, two established anti-mycobacterial drugs. Several non-tuberculous mycobacteria, including the pathogenic members of the Mycobacterium avium-intracellulare complex (MAC) and the fast-growing saprophytic organism M. smegmatis, produce an array of serovar-specific (ss) and non-serovar-specific (ns) glycopeptidolipids (GPLs). GPL biosynthesis has been investigated for several years but has still not been fully elucidated. The authors demonstrate here that econazole and clotrimazole inhibit GPL biosynthesis in M. smegmatis. In particular, clotrimazole inhibits all four types of nsGPLs found in M. smegmatis, suggesting an early and common target within their biosynthetic pathway. Altogether, the data suggest that an azole-specific target, most likely a cytochrome P450, may be involved in the hydroxylation of the N-acyl chain in GPL biosynthesis. Azole antifungal drugs and potential derivatives could represent an interesting new range of anti-mycobacterial drugs, especially against opportunistic human pathogens including MAC, M. scrofulaceum, M. peregrinum, M. chelonae and M. abscessus.

A comparison of mycolic acid analysis for nontuberculous mycobacteria identification by thin-layer chromatography and molecular methods

The development of fast, inexpensive, and reliable tests to identify nontuberculous mycobacteria (NTM) is needed. Studies have indicated that the conventional identification procedures, including biochemical assays, are imprecise. This study evaluated a proposed alternative identification method in which 83 NTM isolates, previously identified by conventional biochemical testing and in-house M. avium IS1245-PCR amplification, were submitted to the following tests: thin-layer chromatography (TLC) of mycolic acids and PCR-restriction enzyme analysis of hsp65(PRA). High-performance liquid chromatography (HPLC) analysis of mycolic acids and Southern blot analysis for M. avium IS1245 were performed on the strains that evidenced discrepancies on either of the above tests. Sixty-eight out of 83 (82%) isolates were concordantly identified by the presence of IS1245 and PRA and by TLC mycolic acid analysis. Discrepant results were found between the phenotypic and molecular tests in 12/83 (14.4%) isolates. Most of these strains were isolated from non-sterile body sites and were most probably colonizing in the host tissue. While TLC patterns suggested the presence of polymycobacterial infection in 3/83 (3.6%) cultures, this was the case in only one HPLC-tested culture and in none of those tested by PRA. The results of this study indicated that, as a phenotypic identification procedure, TLC mycolic acid determination could be considered a relatively simple and cost-effective method for routine screening of NTM isolates in mycobacteriology laboratory practice with a potential for use in developing countries. Further positive evidence was that this method demonstrated general agreement on MAC and M. simiae identification, including in the mixed cultures that predominated in the isolates of the disseminated infections in the AIDS patients under study. In view of the fact that the same treatment regimen is recommended for infections caused by these two species, TLC mycolic acid analysis may be a useful identification tool wherever molecular methods are unaffordable.

Structural biology of mycobacterial proteins: The Bangalore effort

As part of an international effort and a national programme, structural analysis of mycobacterial proteins involved in recombination and repair, stringent response and protein synthesis has been undertaken, and work on proteins in a couple of metabolic pathways has been initiated. Already X-ray analysed are Mycobacterium tuberculosis and Mycobacterium smegmatis RecA and their nucleotide complexes, and different crystal forms of M. tuberculosis single-stranded DNA binding protein, M. smegmatis DNA binding protein from stationary phase cells and M. tuberculosis ribosome recycling factor. A comparative study involving these structures and those of similar proteins from other sources brings out the special features of the mycobacterial proteins, which are likely to be useful in selective inhibitor design. The structures provide insights into the plasticity of the molecules and its biological implications, and yield valuable information on their assembly and quaternary structure. They also provide leads for further structural investigations.

Mycobacterial lipid II is composed of a complex mixture of modified muramyl and peptide moieties linked to decaprenyl phosphate

Structural analysis of compounds identified as lipid I and II from Mycobacterium smegmatis demonstrated that the lipid moiety is decaprenyl phosphate; thus, M. smegmatis is the first bacterium reported to utilize a prenyl phosphate other than undecaprenyl phosphate as the lipid carrier involved in peptidoglycan synthesis. In addition, mass spectrometry showed that the muropeptides from lipid I are predominantly N-acetylmuramyl-L-alanine-D-glutamate-meso-diaminopimelic acid-D-alanyl-D-alanine, whereas those isolated from lipid II form an unexpectedly complex mixture in which the muramyl residue and the pentapeptide are modified singly and in combination. The muramyl residue is present as N-acetylmuramic acid, N-glycolylmuramic acid, and muramic acid. The carboxylic functions of the peptide side-chains of lipid II showed three types of modification, with the dominant one being amidation. The preferred site for amidation is the free carboxyl group of the meso-diaminopimelic acid residue. Diamidated species were also observed. The carboxylic function of the terminal D-alanine of some molecules is methylated, as are all three carboxylic acid functions of other molecules. This study represents the first structural analysis of mycobacterial lipid I and II and the first report of extensive modifications of these molecules. The observation that lipid I was unmodified strongly suggests that the lipid II intermediates of M. smegmatis are substrates for a variety of enzymes that introduce modifications to the sugar and amino acid residues prior to the synthesis of peptidoglycan.

Acceptor-Dependent Stereoselective Glycosylation: 2‘-CB Glycoside-Mediated Direct β-d-Arabinofuranosylation and Efficient Synthesis of the Octaarabinofuranoside in Mycobacterial Cell Wall

[reaction: see text]. A reliable and generally applicable direct method for the stereoselective beta-arabinofuranosylation employing a 2'-carboxybenzyl arabinofuranoside as the glycosyl donor has been established. The acyl-protective group on glycosyl acceptors is essential for the beta-stereoselectivity. The power of the present acceptor-dependent glycosylation method was demonstrated by the efficient synthesis of the octaarabinofuranoside in arabinogalactan and lipoarabinomannan found in mycobacterial cell wall.

Direct molecular mass determination of trehalose monomycolate from 11 species of mycobacteria by MALDI-TOF mass spectrometry

Direct estimation of the molecular mass of single molecular species of trehalose 6-monomycolate (TMM), a ubiquitous cell-wall component of mycobacteria, was performed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. When less than 1 μg TMM was analysed by MALDI-TOF mass spectrometry, quasimolecular ions [M+Na]+of each molecular species were demonstrated and the numbers of carbons and double bonds (or cyclopropane rings) were determined. Since the introduction of oxygen atoms such as carbonyl, methoxy and ester groups yielded the appropriate shift of mass ions, the major subclasses of mycolic acid (α, methoxy, keto and wax ester) were identified without resorting to hydrolytic procedures. The results showed a marked difference in the molecular species composition of TMM among mycobacterial species. Unexpectedly, differing from other mycoloyl glycolipids, TMM fromMycobacterium tuberculosisshowed a distinctive mass pattern, with abundant odd-carbon-numbered monocyclopropanoic (or monoenoic)α-mycolates besides dicyclopropanoic mycolate, ranging from C75to C85, odd- and even-carbon-numbered methoxymycolates ranging from C83to C94and even- and odd-carbon-numbered ketomycolates ranging from C83to C90. In contrast, TMM fromMycobacterium bovis(wild strain and BCG substrains) possessed even-carbon-numbered dicyclopropanoicα-mycolates. BCG Connaught strain lacked methoxymycolates almost completely. These results were confirmed by MALDI-TOF mass analysis of mycolic acid methyl esters liberated by alkaline hydrolysis and methylation of the original TMM. Wax ester-mycoloyl TMM molecular species were demonstrated for the first time as an intact form in theMycobacterium avium–intracellularegroup,M. phleiandM. flavescens. TheM. avium–intracellularegroup possessed predominantly C85and C87wax ester-mycoloyl TMM, whileM. phleiand the rapid growers tested contained C80, C81, C82and C83wax ester-mycoloyl TMM. This technique has marked advantages in the rapid analysis of not only intact glycolipid TMM, but also the mycolic acid composition of each mycobacterial species, since it does not require any degradation process.

The antituberculosis, antitumor, multibranched dodecafuranoarabinan of Mycobacterium species has been assembled from a single n-pentenylfuranoside source

An n-pentenyl furanosyl-1,2-orthoester can function as a donor or be rearranged leading to an n-pentenyl furanoside acceptor which is glycosylated by its progenitor, regioselectively or doubly, thereby enabling rapid fabrication of a multibranched dodecasaccharide, known to possess a wide variety of biological interactions.

Measurement of Immunoglobulin G against Mycobacterial Antigen A60 in Patients with Cystic Fibrosis and Lung Infection Due to Mycobacterium abscessus

BACKGROUND

The diagnosis and prognosis of lung infections due to the emerging nontuberculous mycobacterium (NTM) Mycobacterium abscessus are difficult to establish in children with cystic fibrosis.

METHODS

We evaluated the usefulness of an enzyme-linked immunosorbent assay for detecting serum IgG antibodies against the ubiquitous mycobacterial antigen A60.

RESULTS

A total of 186 patients with cystic fibrosis (mean age+/-SD, 12.0+/-5.0 years) were studied, including 15 M. abscessus-positive patients who fulfilled American Thoracic Society (ATS) criteria for NTM infection (M. abscessus-infected patients), 7 M. abscessus-positive patients who did not fulfill ATS criteria, 20 patients positive for various other NTM who did not fulfill ATS criteria, and 144 NTM-negative control patients; mean IgG titers (+/-SD) for these 4 groups were 718+/-342 U, 193+/-113 U, 129+/-49 U, and 121+/-53 U, respectively (M. abscessus-infected patients vs. each of the other groups, P<.005). The A60 IgG test was both sensitive (approximately 87%) and specific (approximately 95%) if adapted cutoff values were used (150 U and 250 U for patients aged <or=10 years and patients aged >10 years, respectively) and correlated well with results of acid-fast bacilli smears.

CONCLUSION

Measurement of anti-A60 IgG may be useful for both the diagnosis and assessment of activity of M. abscessus lung infection in persons with cystic fibrosis.

Mycobacterial lipoarabinomannans modulate cytokine production in human T helper cells by interfering with raft/microdomain signalling

Lipoarabinomannans (LAMs) are major lipoglycans of the mycobacterial envelope and constitute immunodominant epitopes of mycobacteria. In this paper, we show that mannose-capped (ManLAM) and non-mannose-capped (PILAM) mycobacterial lipoglycans insert into T helper cell rafts without apparent binding to known receptors. T helper cells modified by the insertion of PILAM responded to CD3 cross-linking by decreasing type 1 (IL-2 and IFN-gamma) and increasing type 2 (IL-4 and IL-5) cytokine production. Modification by the mannose-capped ManLAMs had similar, but more limited effects on T helper cell cytokine production. When incorporated into isolated rafts, PILAMs modulated membrane-associated kinases in a dose-dependent manner, inducing increased phosphorylation of Src kinases and Cbp/PAG in Th1 rafts, while decreasing phosphorylation of the same proteins in Th2 rafts. Mycobacterial lipoglycans thus modify the signalling machineries of rafts/microdomains in T helper cells, a modification of the membrane organization that eventually leads to an overall enhancement of type 2 and inhibition of type 1 cytokine production.

Structure elucidation of a novel family of mycolactone toxins from the frog pathogen Mycobacterium sp. MU128FXT by mass spectrometry

Structures are proposed, based on LC-ion trap MSn analysis and high-resolution FTICR MS/MS analysis, for a novel family of mycolactone toxins isolated from the frog pathogen MU128FXT and differing from those produced by the human pathogen M. ulcerans MUAgy99 in having an altered polyketide side chain.

Highly Ordered Supra-Molecular Organization of the Mycobacterial Lipoarabinomannans in Solution. Evidence of a Relationship Between Supra-Molecular Organization and Biological Activity

The complex mycobacterial mannosylated lipoarabinomannans (ManLAMs) are currently considered to be the major virulence factors of the pathogenic Mycobacterium tuberculosis. The recognition and the interaction of ManLAMs with immune system receptors have been shown to promote M.tuberculosis phagocytosis but also to down-regulate the bactericidal immune response of the host in favor of the survival of the pathogenic bacilli. To date these original biological activities were mainly associated to the presence of mannose residues capping the non-reducing ends of the ramified polysaccharide moiety of these complex lipoglycans. However, we demonstrated recently that the molecular recognition of ManLAM terminal mannose units by human pulmonary surfactant protein A (hSP-A) carbohydrate recognition domains depends on the presence of the lipid moiety of the ManLAMs as proposed by Sidobre et al. in 2002. Thus, we investigated the putative role of the ManLAM aglycon moiety. The data presented here, indicate that the hydrophobic aglycon part of ManLAM is associated to a characteristic concentration-dependent supra-molecular organization of these complex molecules. Furthermore, we observed that the deacylated ManLAMs or the lipid-free mannosylated arabinomannans, which do not exhibit characteristic ManLAM activities, do not display this supra-molecular organization. These observations strongly suggest that the ManLAMs immunomodulatory activities might be associated to their particular organization. Finally, the determination of the critical micellar concentration of ManLAMs obviously supports the notion that this supra-molecular organization may be responsible for the specific biological activities of these complex molecules.

Evidence for the existence of PAH-quinone reductase and catechol-O-methyltransferase in Mycobacterium vanbaalenii PYR-1

Polycyclic aromatic hydrocarbon (PAH) quinone reductase (PQR) and catechol-O-methyltransferase (COMT), from the PAH-degrading Mycobacterium vanbaalenii PYR-1, were demonstrated to be constitutive enzymes located in the soluble fraction of cell extracts. PQR activities for the reduction of 9,10-phenanthrenequinone and 4,5-pyrene- quinone were 1.40+/-0.13 and 0.12+/-0.01 micromol min(-1) mg-protein(-1), respectively. The exogenous catechols alizarin, anthrarobin, 2,3-dihydroxynaphthalene and esculetin inhibited PQR activity. Anthrarobin (100 microM) and esculetin (100 microM) inhibited 4,5-pyrenequinone reduction by 64-92%. COMT was involved in the O-methylation of 1,2-dihydroxyphenanthrene to form 1-methoxy-2-hydroxyphenanthrene and 1,2-dimethoxyphenanthrene. Both pyrene and 1-hydroxypyrene were metabolized by M. vanbaalenii PYR-1 to form 1-methoxypyrene, 1-methoxy-2-hydroxypyrene, 1-hydroxy-2-methoxypyrene and 1,2-dimethoxypyrene. Among the catechols tested, anthrarobin showed the highest COMT activity (1.06+/-0.04 nmol/30 min(-1) mg-protein(-1)). These results suggest that the PQR and COMT activities of M. vanbaalenii PYR-1 may play an important role in the detoxification of PAH catechols.

Discovery of (E)-9,10-dehydroepothilones through chemical synthesis: on the emergence of 26-trifluoro-(E)-9,10-dehydro-12,13-desoxyepothilone B as a promising anticancer drug candidate

We provide a full account of the discovery of the (E)-9,10-dehydro derivatives of 12,13-desoxyepothilone B (dEpoB), a new class of antitumor agents with promising in vivo preclinical properties. The compounds, which are to date not available by modification of any of the naturally occurring epothilones, were discovered through total chemical synthesis. We describe how our investigations of ring-closing metathesis reactions in epothilone settings led to the first and second generation syntheses of (E)-9,10-dehydro-12,13-desoxyepothilone congener 6. With further modifications, the synthesis was applied to reach a 26-trifluoro derivative compound (see compound 7). To conduct such studies and in anticipation of future development needs, the total synthesis which led to the initial discovery of compound 7 was simplified significantly. The total synthesis methodology used to reach compound 7 was then applied to reach more readily formulated compounds, bearing hydroxy and amino functionality on the 21-position (see compounds 45, 62, and 63). Following extensive in vitro evaluations of these new congeners, compound 7 was nominated for in vivo evaluations in xenograft models. The data provided herein demonstrate a promising therapeutic efficacy, activity against large tumors, nonrelapseability, and oral activity. These results have identified compound 7 as a particularly promising compound for clinical development. The excellent, totally synthetic, route to 7 makes such a program quite feasible.