Cell walls of Mycobacteria and related organisms; chemistry and immunostimulant properties

Trehalose 6,6'-dimycolate (cord factor) of Mycobacterium tuberculosis induces corneal angiogenesis in rats

Neovascularization or angiogenesis is required for the progression of chronic inflammation. The mechanism of inflammatory neovascularization in tuberculosis remains unknown. Trehalose 6, 6'-dimycolate (TDM) purified from Mycobacterium tuberculosis was injected into rat corneas. TDM challenge provoked a local granulomatous response in association with neovascularization. Neovascularization was seen within a few days after the challenge, with the extent of neovascularization being dose dependent, although granulomatous lesions developed 14 days after the challenge. Cytokines, including tumor necrosis factor alpha (TNF-alpha), interleukin-8 (IL-8), IL-1beta, and vascular endothelial growth factor (VEGF), were found in lesions at the early stage (within a few days after the challenge) and were detectable until day 21. Neovascularization was inhibited substantially by neutralizing antibodies to VEGF and IL-8 but not IL-1beta. Treatment with anti-TNF-alpha antibodies resulted in partial inhibition. TDM possesses pleiotropic activities, and the cytokine network plays an important role in the process of neovascularization.

Molecular mechanics of the mycobacterial cell wall: from horizontal layers to vertical scaffolds

Current models depicting the structural organization of the mycobacterial cell wall assume peptidoglycan and galactan strands to run in parallel to the cytoplasmic membrane forming several horizontal layers beneath perpendicularly oriented mycolic acids. Following a thorough re-evaluation of the currently available chemical, biochemical and electron microscopical data, we propose a fundamentally distinct principle of the physical organization and biosynthesis of the mycobacterial cell wall skeleton. According to this new concept, the solid and elastic matrix that makes the mycobacterial cell wall a formidably impermeable barrier is the direct consequence of cross-linked glycan strands which all run in a direction perpendicular to the cytoplasmic membrane.

Prostaglandin E2 affects differently the release of inflammatory mediators from resident macrophages by LPS and muramyl tripeptides

LPS and MTP-PE (liposome-encapsulated N-acetyl-muramyl-L-alanyl-D-isoglutaminyl-L-alanine-2-:[1',2'dipalmitoyl -sni-glycero-3-(hydroxy-phosphoryl-oxyl)] etylamide) induce in liver macrophages a synthesis and release of TNF-alpha, nitric oxide and prostanoids. Both agents induce an expression of mRNA's encoding TNF-alpha, inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2, and of corresponding proteins. LPS and MTP-PE induce a rapid activation of the extracellular regulated kinase (ERK) isoenzymes-1 and -2. Inhibition of map kinase isoenzymes leads to a decreased release of TNF-alpha, nitric oxide and prostaglandin (PG) E2 after both agents. The transcription factors NF-kappaB and AP-1 are strongly activated by LPS within 30 minutes. MTP-PE induces a weak activation of both transcription factors only after 5 hours. Inhibition of NF-kappaB inhibits the LPS- but not the MTP-PE-induced release of TNF-alpha, nitric oxide and PGE2. PGE2 release after LPS is higher than after MTP-PE. Exogenously added PGE2 inhibits the activation of map kinase and TNF-alpha release by LPS, but not by MTP-PE. Release of nitric oxide after LPS and MTP-PE is enhanced after prior addition of PGE2. PGD2 is without any effect. MTP-PE, but not LPS, induces a cytotoxicity of Kupffer cells against P815 tumor target cells. The MTP-PE-induced cytotoxicity is reduced by TNF-alpha neutralizing antibodies, indicating the involvement of TNF-alpha. Thus our results suggest that the different potencies of LPS and MTP-PE as immunomodulators probably result from different actions on Kupffer cells, resulting in differences in the amounts and kinetics of released TNF-alpha and PGE2, and that PGE2 plays an important regulatory role in the action of LPS, but not in the actions of MTP-PE.

Immunological relatedness of the protective mechanisms against tuberculosis and cancer

BACKGROUND

Bacille Calmette-Guérin (BCG), an attenuated strain of tuberculous bacillus, is the source of vaccines providing unclear and variable protection against tuberculosis (TB) and cancer. Thermostable macromolecular antigens (TMAs) are major mycobacterial complexes immunodominant in disease. A60 (TMA complex of BCG) protects mice against TB development, via T lymphocyte (TL)-mediated macrophage (Mphi) activation, halting intracellular mycobacterial replication. In most A60-primed mice, cytolytic TLs and Mphi infiltrate cancer tissue, resulting in 80-100% rejection. Adoptive TL transfer is indispensable for Mphi-dependent tumour cell inactivation via oxygen and nitrogen radicals. Neoplasm development induces immune anergy with depletion ofA60-specific TL and activated Mphi. A60 protects mice against TB and cancer by inducing the synthesis of three lymphokines: interleukin 2 (IL-2), interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha). Tumour cells prevent A60-dependent synthesis of these lymphokines in vivo and in vitro.

CONCLUSION

These data provide some clues to immune surveillance and tumour escape mechanisms, as well as to the antituberculous and antineoplastic BCG action.

The mycobacterial cell wall: structure, biosynthesis and sites of drug action

Structural analysis has been successfully implemented recently to obtain valuable information on the mycobacterial cell wall components, many of which have formed the basis for biosynthesis and functional studies towards developing better drugs and possible vaccines. The highly complex and well organized structure unique to mycobacteria, represents the best target for novel antimycobacterial agents. Until recently, our knowledge of the enzymes responsible for the biogenesis of the cell wall components was almost negligible. The pathways are now being elucidated in several laboratories. Highlights of this review include significant advances in the structure and biochemistry of the major cell wall components and potential targets for generation of new drugs.

Strategies used by pathogenic and nonpathogenic mycobacteria to synthesize rRNA

One rRNA operon of all mycobacteria studied so far is located downstream from a gene thought to code for the enzyme UDP-N-acetylglucosamine carboxyvinyl transferase (UNAcGCT), which is important to cell wall synthesis. This operon has been designated rrnAf for fast-growing mycobacteria and rrnAs for slow growers. We have investigated the upstream sequences and promoter activities of rrnA operons of typical fast growers which also possess a second rrn (rrnBf) operon and of the rrnA operons of the fast growers Mycobacterium abscessus and Mycobacterium chelonae, which each have a single rrn operon per genome. These fast growers have a common strategy for increasing the efficiency of transcription of their rrnA operons, thereby increasing the cells' potential for ribosome synthesis. This strategy involves the use of multiple (three to five) promoters which may have arisen through successive duplication events. Thus we have identified a hypervariable multiple promoter region (HMPR) located between the UNAcGCT gene and the 16S rRNA coding region. Two promoters, P1 and PCL1, appear to play pivotal roles in mycobacterial rRNA synthesis; they are present in all of the species examined and are the only promoters used for rRNA synthesis by the pathogenic slow growers. P1 is located within the coding region of the UNAcGCT gene, and PCL1 has a characteristic sequence that is related to but distinct from that of the additional promoters. In fast-growing species, P1 and PCL1 produce less than 10% of rRNA transcripts, so the additional promoters found in the HMPR are important in increasing the potential for rRNA synthesis during rapid growth. In contrast, rrnB operons appear to be regulated by a single promoter; because less divergence has taken place, rrnB appears to be younger than rrnA.

A novel method for the isolation of mycobacterial DNA

DNA was isolated from mycobacteria by a simplified procedure. Cells were suspended in 6 M guanidinium chloride, the suspension was cooled to -70 degrees C, then incubated at 65 degrees C for 10 min, cooled in ice, deproteinized by chloroform and DNA was recovered from the supernatant. The procedure was used to obtain DNA from several mycobacteria (1 x 10(9) or more cells) including Mycobacterium neoaurum, M. fortuitum, M. phlei and M. smegmatis. Each of the species was shown to have two ribosomal RNA operons per genome, and preliminary evidence was obtained which suggests that one of these operons is homologous with one of the operons of M. smegmatis.

Composition and immunoreactivity of the A60 complex and other cell fractions from Mycobacterium bovis BCG

Surface static cultures of Mycobacterium bovis BCG contained cells embedded in an extracellular matrix, whose mechanical removal yielded free cells that were pressure disrupted and fractionated into cytoplasm and walls. Cell envelopes were either mechanically disrupted or extracted with detergents. Intracellular and extracellular fractions were analysed for proteins, polysaccharides, and antigen 6O (A60), a major complex immunodominant in tuberculosis. A60 was present in extracellular matrix, cytoplasm and walls: it represented a substantial portion of the proteins and polysaccharides of these fractions. While the protein/polysaccharide ratio varied according to the origin of A60 preparations, the electrophoretic patterns of A60 proteins (which accounted for the immunogenicity of the complex) remained unchanged. Western blots pointed to the proteins present within the 29-45 kDa range as the A60 components endowed with the highest immunogenicity level. Since the most heavily stained protein bands in SDS-PAGE patterns were located outside the region best recognized by antisera, a striking discordance was found between concentration and immunogenicity patterns of A60 proteins. The electrophoretic patterns of A60- and non-A60-proteins from cytoplasm were also different. A60 complexes in dot blots and some electrophoresed A60 proteins reacted with monoclonal antibodies directed against lipoarabinomannan (LAM), a highly immunogenic polymer of cell envelope. This contaminating compound was removed from A60 with organic solvents and detergents. SDS-PAGE and Western blot patterns of proteins from delipidated A60 were similar to those of native A60 proteins.

Depression of cytochrome P-450 in mouse liver induced by fractions from Nocardia opaca

We measured the liver cytochrome P-450 content of mice 24 h after they had been injected with the following immunoadjuvants: Nocardia opaca derivatives and peptidoglycans from several bacterial strains. The cell wall fraction was not active, the others diminished liver cytochrome P-450 levels. The dose-response activity varied with the bacterial origin of the peptidoglycans. These findings indicate that the toxicity and efficiency of immunochemotherapeutic protocols can be modified by altering drug metabolism.

Pharmacokinetics and immunomodulatory effects on monocytes during prolonged therapy with liposomal muramyltripeptide

The macrophage activator muramyl tripeptide-phosphatidyl ethanolamine (MTP-PE) was infused in liposomal form in 14 metastatic cancer patients (4 mg i.v. during 30 min twice weekly for 12 weeks). Clinical, pharmacokinetic and immunological parameters were studied before and 0.5, 2, 4, 24 and 72h after start of drug infusion in week 1, 4, 8 and 12. No tumor regressions were seen. Tumors progressed in 11 patients, in 4 of them within 2 months; 3 patients had stable disease. The intensity and frequency of side effects (fever and nausea) diminished from week 1 to 12. The rate of disappearance of total and free MTP-PE from blood was rapid and mean serum concentration-time curves remained unchanged throughout 12 study weeks. MTP-PE caused a marked increase of serum TNFa, IL-1 receptor antagonist (IL-1ra) and IL-6 in week 1, but not thereafter. In contrast, MTP-PE caused a persistent, 2-fold increase in serum neopterin and young forms of granulocytes (bands) during week 1 to 12. Before therapy, monocyte tumor cytotoxicity and in-vitro monocyte derived TNFa, IL-1 beta and IL-6 production were low in 9 patients (group L, < 15%) and high in 5 patients (group H, > 40%). Monocyte cytotoxicity and in-vitro cytokine production was transiently enhanced in week 1 in group L, it declined under therapy in group H. In conclusion, MTP-PE induced marked initial immunomodulation; the extent of the ex vivo monocyte cytokine and tumor cytotoxic response was dependent on pre-therapy cell activity. A decrease of the cytokine and IL-1ra response during prolonged therapy contrasted with a persistent increase of neopterin and juvenile blood granulocytes. The long lasting biologic effects may be relevant to direct future clinical studies with liposomal MTP-PE in an adjuvant setting.

Composition and immunogenicity of the polysaccharide components of the thermostable macromolecular antigen group of mycobacterial antigens

The thermostable macromolecular antigen (TMA) group includes major components of the mycobacterial cell envelope and cytoplasm, which elicit humoral and cellular immune reactions, and seems to play important roles in infectious diseases. The best known member of this group, antigen A60 of Mycobacterium bovis BCG, was previously shown to contain three moieties of polysaccharides, free lipids, and polypeptides. In this work, the TMA polysaccharides of three pathogenic mycobacteria (M. avium, M. bovis and M. paratuberculosis) have been analyzed by coupled gas chromatography-mass spectrometry. In all cases the cores of the TMA complexes were represented by branched glucans of high molecular mass (about 10(6) daltons), for which structural models have been proposed. The immunogenicity of the polysaccharide components from the three TMA was verified with several immunological procedures (immunodiffusion and immunoelectrophoresis of the antigen, and immunoblotting of the corresponding electrofocused immunoglobulins). All tests tallied in showing a negligible immunogenicity of the glucans examined (inability to produce, upon injection, the synthesis of specific immunoglobulins), thus pointing to the protein moiety of TMA as the one responsible for the high immunoreactivity of the complexes.

Enhancement of natural killer cell activity by Nocardia opaca fractions

Three molecules derived from Nocardia opaca bacteria, NDCM, NWSMP, and PG, have been shown to express immunomodulating properties. The present study was aimed at assessing the effects of these derivatives on natural killer (NK) activity. Two experimental protocols were adopted, consisting of incubating whole or Percoll fractionated NK cells in vitro with those substances, and the other in which the derivatives were administered in vivo to mice and the activity assessed later. Incubation of spleen cells in vitro with NWSMP or its precursor NDCM promoted NK activity. This effect could be observed after only 2 h of incubation and continued until day 2. Percoll fractions 1-3, which contain most of the NK activity, were enhanced to a similar extent. Band 4, which is usually devoid of such activity, remained unresponsive even after contact with the N. opaca derivatives. PG was practically ineffective upon all the subsets. The results of experiments in vivo correlated with those obtained in vitro in that NWSMP and NDCM, but not PG, promoted NK activity. Bands 1-3 were similarly enhanced, the effect was observed after short treatment times, and could be partially cancelled by the concomitant administration of anti-interferon antibodies (anti-IFN Ab). All these findings suggest that the promoting effects of N. opaca derivatives are mediated through alpha/beta IFN. In contrast to the results observed on spleen NK cells, NK cells from the peritoneum displayed susceptibility mainly to PG, and much less to NWSMP or NDCM. The administration of PG to mice in vivo had a particularly marked promoting effect upon the cytotoxic activity of peritoneal cells. One logical explanation for the difference observed between PG and NWSMP or NDCM may be related to the specific IFN inducing properties of these compounds as well as to the different responsiveness of the NK cells present in the spleen and peritoneal cavity.

Molecular species of mycolic acid subclasses in eight strains of Mycobacterium smegmatis

Thin layer chromatographic and gas chromatographic separation and mass spectrometric identification of mycolic acid subclasses and molecular species from eight strains of Mycobacterium smegmatis were established. Two major adjacent spots and a lower minor one were detected on silica gel thin layer chromatograms of methyl esters. The most abundant subclass showing the highest Rf value on TLC was that of alpha-mycolic acids (M1), the second was that of alpha-mycolic acids (M1), a shorter homologue than alpha-mycolates, and the third was the hydroxy mycolic acids (M4) derived from epoxy mycolic acids. They were identified by gas chromatography-mass spectrometry as their trimethylsilylether derivatives. alpha'-Mycolic acids were monoenoic acids ranging from C60 to C66 and possessing an alpha-unit of C24:0. Such profiles of alpha'-mycolic acids were common in eight strains. alpha-Mycolates were dienoic acids ranging from C75 to C79 and possessing an alpha-unit of C24:0. In most strains, the major molecular species of alpha-mycolates were odd-carbon-numbered, centering at C77 and C79, possessing a methyl branch in the even-carbon-numbered straight chain. The average carbon number of alpha-mycolates, from seven strains examined, was about 78, but that of the Takeo strain was 76.3. The profiles of epoxy mycolic acid molecular species composition from eight strains ranging from C75 to C81 were very similar to their M1 subclass profiles.

Metabolism of the TMA group of antigens during the growth cycle of mycobacteria

The TMA (thermostable macromolecular antigens) group includes A60 of Mycobacterium tuberculosis and A7 of M. leprae, active components of tuberculin and lepromin. We have previously described the purification and composition of A60, and its ability to elicit immune reactions of humoral and cellular type. In the present work, the intracellular and extracellular distribution and composition of A60 have been traced, as a function of the replication cycle, in static surface cultures of M. bovis. In exponentially-growing mycobacteria, most A60 was present in the cytoplasm and had a high protein/polysaccharide ratio: this ratio, as well as the level of cytoplasmic A60, decreased after cessation of cell proliferation. The A60 fraction located within the cell wall increased during the stationary phase, but its protein/polysaccharide ratio underwent minor changes. A release of cellular polypeptides and polysaccharides into the extracellular fluid occurred during the declining and lysing phases: a fraction of it was represented by A60. This explains the practice of old tuberculin preparation by autoclaving filtrates of autolysed mycobacterial cultures. The pattern of an A60-like antigen in shaken homogeneous cultures of M. smegmatis was similar (most antigen present in cytoplasm during growth, increase of the wall fraction in stationary phase, and extracellular release during the declining phase).

Leprosy

Leprosy affects over 10 million people in the world. The disease is a model of graded cell-mediated immunity, in this case to the causative organism, Mycobacterium leprae. The clinical manifestations are due to (i) bacterial progression, (ii) immunologic responses of the host, (iii) peripheral nerve damage due to either or both bacterial progression and immunologic responses of the host, and (iv) preventable secondary deformities following nerve damage, which account for most of the stigma of the disease. Treatment modalities are now available to control or minimize the effects of bacterial progression, harmful immunologic responses of the host, peripheral nerve damage, and secondary deformities. Unique biochemical characteristics of M. leprae reside in the cell wall and associated macromolecules. Some of these molecules are potent immunogens in humans, while others constitute the structural integrity of the bacillus. Proteins of M. leprae are currently under intensive investigation as a result of deoxyribonucleic acid cloning of M. leprae genes. Structure-function and antigenic relationships of M. leprae proteins should become available by using recombinant deoxyribonucleic acid procedures coupled with T- and B-cell cloning to advance our understanding of the immunologic reactions encountered in Hansen's disease. Until recently, the study of the immunology of leprosy has been stymied by the lack of immunologically specific M. leprae antigens. The definition of specific antigens and production of recombinant and synthetic immunologic reagents have fostered state-of-the-art research efforts into new immunodiagnostic procedures and development of a leprosy vaccine. Also discussed is progress in understanding of the mechanism(s) underlying the M. leprae-specific immunodeficiency associated with lepromatous leprosy, including the role of suppressor T cells and defective macrophage function. Metabolic studies of M. leprae suggest intact catabolic pathways and energy generation with purine bases and catalase as possible growth factors. Special attention may also need to be given to biophysical parameters for eventual in vitro cultivation. Rapid in vitro systems, using quantitation of bacillary metabolic activity, may soon replace the lengthy mouse footpad test for determining the viability and drug susceptibility of the leprosy bacillus.

Subcellular localisation and sedimentation behaviour of antigen 60 from Mycobacterium bovis BCG

Preparation, composition and immunological properties of A60 of Mycobacterium bovis BCG were previously described (Cocito and Vanlinden 1986). The present study focused on the intracellular distribution of this antigen. Fractionation of mycobacterial homogenates by ultracentrifugation indicated that most of A60 was present within the cytoplasm. Some of the antigen was located within the cell wall, from which it was released by extraction with alkali. Submission of cytoplasm to high speed centrifugation caused A60 to cosediment with ribosomes; however, dissociation of ribosomes in low-Mg buffer did not alter the sedimentation pattern of A60. Labelled A60, after ultracentrifugation in sucrose density gradients without Mg2+, was distributed throughout the entire gradient: treatment of (125I)A60 with urea or detergents produced a peak of radioactivity located in the upper part of the gradient. It is concluded that A60 is represented by a heterogeneous family of molecules of increasing sizes: polymerization being enhanced by Mg2+ and reversibly prevented by urea. Some or all of the biological properties hitherto attributed to ribosomal particles may, in fact, be due to their contamination with cosedimented A60.

Demonstration that the galactosyl and arabinosyl residues in the cell-wall arabinogalactan of Mycobacterium leprae and Mycobacterium tuberculosis are furanoid

By a complex process involving methylation, partial hydrolysis with acid, reduction with sodium borodeuteride, ethylation, further hydrolysis and reduction, and subsequent capillary gas-liquid chromatography-mass spectrometry of the derived alditol acetates, it was established that the arabinogalactans of Mycobacterium leprae and Mycobacterium tuberculosis contain arabinofuranyosyl and galactofuranosyl residues exclusively. Thus, the covalently bound, highly immunogenic arabinogalactan of mycobacteria, and presumably of other actinomycetes, is highly unusual, in that all of the glycosyl residues are in the furanoid form. Furthermore, by establishing that the galactofuranosyl residues are either 5-, 6-, or 5,6-linked, their linkage pattern was established, and the literature is corrected on this point.

Immunological properties of antigen 60 of BCG. Induction of humoral and cellular immune reactions

Antigen 60 (A60), a member of the thermostable macromolecular antigen family (TMA) and main component of old tuberculin and purified protein derivative (PPD), has been purified from the cytoplasm of Mycobacterium bovis BCG; its structure and metabolism have already been described. In the present paper, the action of A60 on humoral immunity has been analysed by an ELISA type immunoassay, and that on cellular immunity by the mouse footpad swelling test. Injection of very low A60 doses into unprimed mice produced an undetectable level of anti-A60 antibodies; the effect of a booster inoculation was not appreciable in the absence of incomplete Freund's adjuvant, but was evident when the latter was added. Higher doses of the antigen produced an appreciable primary response, and a sharp and long-lasting secondary response, which had a 10-fold higher intensity in the presence of incomplete adjuvant. No detectable delayed hypersensitivity reactions were observed in unprimed mice after footpad injection of A60, whereas clear responses were elicited in primed mice. This effect was more pronounced when the footpad was injected after a secondary response than after a primary response, and it was invariably magnified by incomplete adjuvant. It is concluded that A60 is a powerful immunogen, which is able to induce primary and secondary responses and delayed hypersensitivity reactions, effects that are adjuvant-modulated and develop concurrently.

Determination of molecular species composition of C80 or longer-chain alpha-mycolic acids in Mycobacterium spp. by gas chromatography-mass spectrometry and mass chromatography

The molecular species composition of alpha-mycolic acids ranging from C68 to C86 in 13 rapidly growing and 12 slowly growing mycobacterial species was determined by gas chromatography, gas chromatography-mass spectrometry, and mass chromatography. In gas chromatographic analysis, the molecular species of alpha-mycolic acids were well separated as trimethylsilyl ether derivatives of the methyl esters, according to their total carbon numbers. The total carbon and double-bond numbers of mycolic acids at each peak on gas chromatograms were determined from the [M]+, [M - 15]+, and [M - 90]+ ions on the mass spectrum, and straight and branched chain structures were identified by the mass fragment ions [A]+, due to C2--C3 cleavage [R-CH-O-Si(CH3)3]+, and [B]+, due to C3--C4 cleavage [(CH3)3-Si-O-CH-CH(R')-COOCH3]+. The concentration of odd- and even-carbon-numbered mycolic acids, which often overlap each other on gas chromatograms, and the composition of three homologous mycolic acids with different alpha units (C22:0, C24:0, and C26:0) were clearly determined by mass chromatography monitoring [M - 15]+ ions and [B - 29]+ ions, respectively. The molecular species composition of alpha-mycolic acids and their average carbon numbers (av. cn.) as a simple expression of the composition were calculated from the mass chromatograms. Each mycobacterial species examined was demonstrated to possess a characteristic profile of alpha-mycolic acid composition, and based on this the species were classified approximately into eight groups: C68 to C76 (av. cn. 72), dienoic, possessing a C20 alkyl branch at the 2 position (C22 alpha-unit) for Mycobacterium diernhoferi and Mycobacterium sp. strain 3707, a chromogenic rapid grower; C72 to C78 (av. cn. 75), dienoic with both C22 and C24 alpha units, containing a small or a large amount of odd-carbon-numbered molecules, for M. vaccae, M. rhodesiae, and M. phlei (chromogenic rapid growers); C72 to C80 (av. cn. 75 to 77), dienoic with C24 alpha-unit, containing a moderate or a large amount of odd-carbon-numbered molecules, for M. smegmatis, M. chitae, M. chelonae (M. chelonei), and M. fortuitum (nonchromogenic rapid growers); C78 to C82 (av. cn. 80), even-carbon-numbered dienoic with C24 alpha unit for M. agri and M. thermoresistible (rapid growers); C75 to C81 (av. cn. 77 to 79), odd-carbon-numbered dienoic with C24 alpha unit for M. nonchromogenicum complex (M. nonchromogenicum, M. terrae, and "M. novum") (slow growers); (vi) C76 to C84 (av. cn. 79 to 81), even-carbon-numbered dienoic with C24 alpha unit for MAIS complex including M. scrofulaceum, M. avium, and M. intracellulare (slow growers); (vii) C72 to C80 (av. cn. 77 to 79), even-carbon-numbered dienoic with C24 alpha unit for M. szulgai, M. gordonae, and M. kansasii (chromogenic slow growers); and (viii) C76 to C86 (av. cn. 79 to 81), even-carbon-numbered dienoic with C26 alpha unit M. bovis Ravenol and BCG and M. tuberculosis H37Rv. This study demonstrated that gas chromatography-mass spectrometric analysis of the molecular species composition of alpha-mycolic acid can give rapid, important, and very precise information for the identification of pathogenic and nonpathogenic mycobacterial species.

Nocardia water soluble mitogen (NWSM), a human B-lymphocyte mitogen

Nocardia water soluble mitogen (NWSM), which is a peptidoglycan, was prepared from Nocardia opaca. Its effect on human B-lymphocyte proliferation, the number of immunoglobulin secreting B-cells, and bone marrow stem cell growth was studied in vitro. NWSM stimulated the proliferation of B-lymphocytes of all ten healthy subjects studied very effectively (P less than 0.0005). No T-cell activation occurred. NWSM did not increase the amount of antibody producing cells. The growth of bone marrow stem cells was enhanced only in one patient out of the eight studied. Thus NWSM is a B-lymphocyte mitogen with a potential effect on hematopoietic stem cells. However, production of NWSM was faced with difficulties because not all lots prepared had B-cell stimulating activity.

Bio-surfactants

Interest in microbially produced biosurfactants has increased recently, due mainly to their potential as agents in enhanced oil recovery. A variety of microbes and their products have been assessed for their surface-active properties, and it has been suggested that biosurfactants may prove useful in a broad spectrum of potential applications which presently utilise synthetic surfactants. The most commonly produced biosurfactants tend to be glycolipids, usually a mono- or di-saccharide attached to a fatty acid, but more complex molecules such as lipopeptides, lipoproteins, and lipo-heteropoly-saccharides have been isolated and studied. Biosurfactant production by microbes is often but not invariably enhanced by the addition of hydrocarbon to the growth medium, and needs to be optimised by controlling such factors as carbon source, nitrogen source and concentrations, aeration and metal ions. Biosurfactants have been shown to be as effective, if not more so, than many conventional synthetic surfactants and their future utilisation may depend utilimately upon the prevailing economics for their production.

Comparison of the cytoplasmic antigens of leprosy-derived corynebacteria and some mycobacteria

The immunological relationship between leprosy-derived corynebacteria (LDC) and reference mycobacteria was analysed by crossed immunoelectrophoresis with intermediate gel. For this purpose, three reference systems (LDC15/anti-LDC15, LDC18/anti-LDC8, and LDC8/anti-LDC8) were developed. They showed 15 to 20 distinct antigenic components in LDC cytoplasm. Extensive cross-reactivity was observed among different LDC isolates, affecting 3 to 17 components. Moreover, several components were shown to cross-react with mycobacteria when anti-bacillus Calmette-Guérin (BCG), anti-Mycobacterium leprae, other antisera and lepromatous leprosy sera were incorporated in the intermediate gel. The major cross-reactive component, antigen M, was present in all LDC isolates and cross-reacted with antigen 7 of M. leprae and antigen 60 of M. bovis BCG. The thermostability of these antigens and the specificity of the cross-reacting antigens were assessed. The data underline the degree of immunochemical homogeneity within the LDC group of micro-organisms and relatedness with M. leprae and other mycobacteria.

Amyloidosis and the serum amyloid A protein response to muramyl dipeptide analogs and different mycobacterial species

Serum amyloid A protein (SAA) elevation accompanies induction of secondary amyloidosis in mice given Mycobacterium butyricum in Freund adjuvant. The synthesis of SAA by cultured hepatocytes is induced by a macrophage-derived mediator, which has been identified as interleukin 1. In these studies, SAA synthesis has been used as an index of macrophage activation to examine the in vivo response of mice to challenge with seven different mycobacteria and with synthetic analogs of the immunoadjuvant N-acetylmuramyl-L-alanyl-D-isoglutamine [MDP(L-D)]. SAA synthesis was stimulated by administration (by the intraperitoneal route) of the mycobacteria dissolved in saline, with Mycobacterium vaccae being the most active and Mycobacterium leprae being the least stimulatory. MDP(L-D), which is the minimal structure (molecular weight, 492) able to substitute for mycobacteria in Freund adjuvant, stimulated SAA synthesis, whereas the MDP(D-D) isomer was inactive. The butyl ester of MDP, which induces no detectable pyrogenicity but retains adjuvanticity, required a 100-fold greater dosage than MDP(L-D) in stimulating SAA synthesis. Amyloidosis was detected histologically only when active SAA inducers MDP(L-D), M. vaccae, and M. butyricum, were administered in incomplete Freund adjuvant, with amyloid-enhancing factor. These studies demonstrated that SAA elevation was a sensitive in vivo marker of the capacity of antigens to stimulate macrophages to produce interleukin 1. A point of considerable relevance to the human use of MDP was the observation that repeated injections of the adjuvant MDP in saline did not induce secondary amyloidosis.

Analysis of mycolic acids from a group of corynebacteria by capillary gas chromatography and mass spectrometry

The cell wall of leprosy-derived corynebacteria (a group of 'diphtheroids' isolated from human leprosy lesions and patients' blood) was previously shown to contain, in addition to peptidoglycan and arabinogalactan, mycolic acids. These alpha-branched beta-hydroxy fatty acids were attributed to the corynomycolic group, according to their RF in monodimensional thin-layer chromatography. In the present work, mycolic acids from leprosy-derived and reference corynebacteria have been fractionated by monodimensional and bidimensional thin-layer chromatography and by gas chromatography. Pyrolyzed mycolic acids have been analyzed on conventional packed columns, whereas intact methyl esters of mycolic acids with free and silylated beta-hydroxyl group have been analyzed on capillary columns, and their structure has been established by mass spectrometry. In all leprosy-derived corynebacteria, some 20 components containing 24-36 carbon atoms and 0-4 double bonds were obtained. The three major groups had 32, 34 and 36 carbons, and the frequency of unsaturated versus saturated chains increased proportionally to the molecular weight. For comparison, the main components of a reference corynebacterium. Corynebacterium diphtheriae PW8, had 30 and 32 carbons, and their hydrocarbon chains were essentially saturated. This work confirms the relative chemical homogeneity of different leprosy-derived corynebacteria and describes some peculiar traits in the chemical structure of this group of organisms. In addition, it shows the complexity of the mycolic acid fraction of corynebacterial cell wall and suggests that the mycolic acid pattern is a sort of fingerprint of each bacterial strain grown under standard conditions. Finally, the fractionation of intact corynomycolic acid methyl esters with free or silylated beta-hydroxyl group by capillary gas chromatography proved to be the best analytical procedure at present available for resolving this complex mixture of corynomycolate isomers. Structural determination of silylated samples by mass spectrometry is preferred because they have more diagnostic fragments.

Primary structure of the wall peptidoglycan of leprosy-derived corynebacteria

The cell walls isolated from axenically grown leprosy-derived corynebacteria were submitted to various chemical and enzymatic degradations. The glycan strands of the wall peptidoglycan are essentially composed of N-acetylglycosaminyl-N-acetylmuramic acid disaccharide units. Small amounts of N-acetylglycosaminyl-N-glycolylmuramic acid (less than 10%) were also detected. The muramic acid residues of adjacent glycan strands are substituted by amidated tetrapeptide units which, in turn, are cross-linked through direct linkages extending between the C-terminal D-alanine residue of one tetrapeptide and the mesodiaminopimelic acid residue of another tetrapeptide. Such a structure is very similar to that of the wall peptidoglycan found in the taxonomically related microorganisms of the Corynebacterium, Mycobacterium, and Nocardia groups.

Fate of the synthetic immunoadjuvant, muramyl dipeptide (14C-labelled) in the mouse

Synthetic N-acetylmuramyl-L-alanyl-D-isoglutamine (muramyl dipeptide or MDP) represents the smallest unit that can substitute for whole Mycobacteria in Freund's complete adjuvant. In this paper the fate of 14C-labelled (on the muramyl moiety) MDP is reported. Following intravenous or subcutaneous injection into mice, more than 50% of 14C-MDP was recovered in the urine after 30 min and more than 90% after 2 h. The labelled compound was found unchanged in the urine, as shown by detailed analyses. However, MDP was sequestered for a longer time at the site of injection when administered as a water-in-oil emulsion. Considering the relatively rapid elimination observed, it is suggested that the biological effects of MDP and related compounds, when administered in an aqueous medium, may be due to their activity at minute concentrations and/or an immediate action at the cellular level.

DD-Carboxypeptidase activity of membrane fragments of Mycobacterium smegmatis. Enzymatic properties and sensitivity to beta-lactam antibiotics

A DD-carboxypeptidase activity is present in membrane fragments of Mycobacterium smegmatis. Kinetic parameters of the enzymatic activity have been studied using UDP-N-glycolylmuramyl-L-alanyl-gamma-D-glutamyl-meso-2,2'-diaminopimelyl-D-[14C]alanyl-D-[14C]alanine as substrate. The DD-carboxypeptidase can be solubilized by Triton X-100 and Genapol X-100. It is inhibited by beta-lactam antibiotics although intact cells of M. smegmatis are insensitive to that kind of antibiotics. Inhibition by penicillin G is slowly reversible. By storage, at -20degrees C, kinetic parameters and sensitivity to penicillin G vary non-concomittantly, suggesting a penicillin binding site different from the substrate binding site.