Palmitate oxidation by in vivo and in vitro grown Mycobacterium lepraemurium.

Oxidation of palmitate by Mycobacterium lepraemurium isolated from C3H mice lepromata (in vivo) and also grown on Ogawa egg-yolk medium (in vitro) was investigated. Palmitate was found to be oxidized, after a lag period of about 8 h, by both the in vivo and in vitro grown bacilli. Cell-free extracts prepared from in vivo and in vitro grown cells catalysed an active oxidation of palmitate after a lag period of 3-4 h. The amount of ATP increased, with the increase in time during oxidation of palmitate by the cell-free extracts. The generation of ATP was strongly inhibited by the inhibitors rotenone, antimycin A and cyanide as well as by the uncouplers 2,4-dinitrophenol and 2,6-dibromophenol. These results indicated that oxidation of palmitate by the in vivo and in vitro grown M. lepraemurium is mediated through the respiratory chain using oxygen as the terminal electron acceptor.     

Regulatory interactions between macrophages and T cells in Mycobacterium lepraemurium-specific T-cell activation

The antigen-specific proliferative response of draining lymph node cells was found to follow a similar pattern in both C57BL and BALB/c mice following subcutaneous infection with Mycobacterium lepraemurium (MLM), although the two strains differed in their ability to control bacterial growth at the site of infection. The proliferative response, which was maximal 1-2 weeks postinfection, was T-cell dependent as it was abrogated with anti-Thy 1.2 + C treatment. The response was also abrogated by pretreatment with anti-Lyt 1.2 + C and slightly reduced by treatment with anti-Lyt 2.2 + C. The decline in T-cell responsiveness, at least from 4 to 8 weeks postinfection, may have been associated with prostaglandin production by inflammatory macrophages, as it was partially restored by addition of indomethacin. Also highly purified T lymphocytes from lymph nodes taken 6-8 weeks postinfection gave a strong antigen-specific proliferative response when reconstituted with optimal numbers of syngeneic antigen-presenting cells from uninfected mice. Proliferation was inhibited by peritoneal macrophages from Corynebacterium parvum-pretreated mice and macrophages from C57BL but not BALB/c mice infected with M. lepraemurium which had been elicited with heat-killed (HK) MLM and thioglycollate. Resident peritoneal macrophages from both C57BL and BALB/c mice infected subcutaneously with M. lepraemurium were slightly more inhibitory than normal macrophages but not as inhibitory as macrophages from C. parvum-pretreated mice. Macrophage-dependent inhibition of T-cell proliferation was partially reversed by addition of indomethacin, suggesting these cells were not defective in processing and presentation of HK-MLM antigens, and that the inhibitory effects were associated with prostaglandin production. Resident peritoneal macrophages from both C57BL and BALB/c mice infected subcutaneously with M. lepraemurium produced comparable or slightly elevated levels of IL-1 on stimulation with LPS or HK-MLM.     

Mycobacterium lepraemurium activates macrophages but fails to trigger release of superoxide anion

Mycobacterium lepraemurium failed to stimulate a normal respiratory burst when presented to mouse peritoneal or bone marrow macrophages. By comparison, Mycobacterium bovis (strain Bacillus Calmette-Guerin) or Saccharomyces cerevisiae, as expected, stimulated macrophages to release a large amount of superoxide anion (O2-). M. lepraemurium did not interfere with the response to yeast when both microbes were added together to macrophages. The low release of O2- induced by M. lepraemurium was not due to failure of M. lepraemurium to activate or prime macrophages, because exposure of macrophages to M. lepraemurium caused the expected enhancement of O2- release when the macrophages were stimulated by PMA. Similarly, macrophages taken from mice infected with M. lepraemurium were activated, as indicated by high PMA-stimulated O2- release. Macrophages primed in vitro by exposure to Escherichia coli LPS for 24 h did show a moderate O2- response when stimulated by M. lepraemurium, but macrophages primed by exposure to IFN-gamma muramyl dipeptide, or M. lepraemurium showed a weak response when subsequently challenged with M. lepraemurium. The priming effect of M. lepraemurium or LPS decreased substantially after macrophages were cultured in fresh medium for 24 h. Heat killing or opsonization of M. lepraemurium caused the M. lepraemurium to stimulate a high amount of O2- release from LPS-primed macrophages, but heat killing or opsonization of M. lepraemurium had no effect on release of O2- from unprimed macrophages. The results suggest that M. lepraemurium is taken into macrophages by a mechanism that bypasses the FcR and other receptors that are capable of triggering the production of O2-.     

Cord factor (trehalose-6-6'-dimycolate) of in vivo-derived Mycobacterium lepraemurium.

Harvests of Mycobacterium lepraemurium obtained from livers of moribund infected mice yielded M. lepraemurium cell walls that were extracted with solvent to provide crude M. lepraemurium cell wall lipids. By solvent fractionation and chromatography on DEAE cellulose and cellulose, a cord factor-like glycolipids contaminated with mycoside C was obtained. Additional solvent treatment provided the purified glycolipid, which was identified as 6,6'-trehalose dimycolate, by infrared and chromatographic comparison with authentic samples from M. tuberculosis, by identification of trehalose and specific mycolates of M. lepraemurium, and by permethylation analysis. This constitutes the first unequivocal identification of cord factor as a product of in vivo-derived mycobacteria.     

The evolution of immunosuppressive cell populations in experimental mycobacterial infection.

Immunosuppressor activity of considerable potency and complexity was generated during the course of chronic, progressive infection of C3H/Anf mice by Mycobacterium lepraemurium. From the 5th through 10th week after inoculation, spleen cells from infected mice mildly but reproducibly suppressed the direct plaque-forming cell response of normal spleen cell cultures to sheep erythrocytes. Suppression at this stage of infection was mediated by cells with macrophage-like characteristics. A marked increase in splenic suppressor activity at 10 to 11 weeks was associated with the appearance of a second suppressor cell subpopulation composed of T lymphocytes. The appearance of these cells was closely related in time to the onset of rapid splenic enlargement and a loss of cutaneous delayed type hypersensitivity to antigens of M. lepraemurium in mice at 10 to 11 weeks of infection. Suppressor cells were not present in peripheral lymph nodes until terminal infection at 22 to 25 weeks. Suppressor spleen cells depressed the T-dependent antibody response most severely, but there was also a direct effect upon B cells as shown by moderate suppression of responses to TNP-LPS and DNP-Ficoll. Spleen cells from 14-week-infected mice generated a soluble suppressor factor(s) that induces depression of moderate severity, however, the immunosuppression by intact cells was far greater.     

Studies on the interaction of Mycobacterium microti and Mycobacterium lepraemurium with mouse polymorphonuclear leucocytes.

When polymorphonuclear leucocytes (PMN) elicited in mice were infected with Mycobacterium microti or Mycobacterium lepraemurium, phagosome-lysosome fusion occurred with both species. This contrasts with the situation in macrophages where phagosome-lysosome fusion is inhibited by M. microti but not M. lepraemurium. No evidence was found for killing of M. microti or M. lepraemurium when the bacteria were isolated from PMN and their viability tested in cell-free medium or macrophages.     

Oxidation of various substrates by host grown Mycobacteria leprae and M. lepraemurium.

Oxidation of various substrates by whole cell suspensions of M. Lepraemurium and M. leprae was investigated using manometric techniques. Yeast extract, L-cysteine, dithioerythritol, and DL-penicillamine were oxidized by both M. lepraemurium as well as by M. leprae. Although tween 80 was oxidized by M. lepraemurium cell suspensions, it was not by M. leprae. Succinate was readily oxidized by whole cells of M. leprae (without being frozen) whereas it was oxidized only by M. lepraemurium cells frozen at -40 degrees C for one minute. The results indicate that M. leprae and M. lepraemurium are capable of oxidizing some substrates without requiring any cofactor and are not dependent upon host cells for respiration.     

Radiometric Measurement of Metabolic Activity of Mycobacterium lepraemurium

A sensitive and nondestructive radiometric method has been applied to the detection of metabolism of Mycobacterium lepraemurium, as a model for the study of the metabolism and substrate requirements of M. leprae. The method is based on the measurement of the (14)CO(2) produced through the bacterial conversion of [U-(14)C]acetate or [U-(14)C]glycerol by 7 x 10(9) bacteria suspended in 10 ml of either a simple buffer system (K-36) or a complex medium (NC-5). Metabolism of the bacilli was easily detected within 3 days after inoculation and was measured daily. NC-5 medium supported metabolism of M. lepraemurium for several weeks longer than the simple K-36 buffer. The radiometric technique shows promise as a rapid and efficient system for evaluating the metabolism of mycobacteria without introducing any changes in the physiologic state of the organisms, studying their metabolic pathways, determining conditions potentially favorable for multiplication of these organisms in vitro, and studying their susceptibility to inhibition by drugs.     

Growth of Mycobacterium lepraemurium in Cultures of Mouse Peritoneal Macrophages

Successful growth of Mycobacterium lepraemurium was observed in cultures of mouse peritoneal macrophages. The optimal host cell maintenance medium was composed of 40% horse serum, 50% of the chemically defined medium NCTC 109, and 10% of a 1:5 dilution of beef embryo extract, supplemented with both liver extract and ferric nitrate. Multiplication of the bacilli was observed in 1 week and maximal growth in 6 to 7 weeks. All macrophages were filled with tens to hundreds of the organisms in cultures showing maximal growth. Glycerol caused an increase in the normal length of M. lepraemurium, without a corresponding increase in the number of the bacilli. Elongation of M. lepraemurium was observed 3 or 4 days after infection. Rapid and uniform growth of M. lepraemurium was achieved in serially transferred cultures (subcultures). The cumulative increase of the number of intracellular bacilli was 1.4 x 10(20)-fold in 14 transfers over a period of 68 weeks in one series, and 10(17)-fold in 12 transfers over a period of 56 weeks in another series. The generation time of M. lepraemurium was 7 days, a growth rate which approximates the fastest growth of the organisms in vivo. Organisms harvested from cultures at various stages of growth produced murine leprosy in mice, but showed no growth in bacteriological media. The present model offers an opportunity for studies on the host-parasite relationship without the complication of extracellular growth of the parasites.     

Study of DTH and resistance in Mycobacterium lepraemurium infection using a T-cell line isolated from mice infected with Mycobacterium bovis (BCG)

A T-cell line of mixed phenotype (60% L3T4+, 40% Lyt-2+) was isolated from mice infected with Mycobacterium bovis (BCG). This line responded to M. lepraemurium and BCG but not to M. leprae and produced TCGF spontaneously. It also produced factors which stimulated macrophages to secrete hydrogen peroxide and superoxide anion. In vivo studies showed that only L3T4+ cells were required to transfer DTH responses and that Lyt-2+ cells suppressed this response. Both L3T4+ and Lyt-2+ cells were required to inhibit M. lepraemurium multiplication in vivo.     

The measurement of adenylate energy charge (AEC) in mycobacteria, including Mycobacterium leprae

Abstract The adenylate energy charge (AEC) of Mycobacterium leprae, Mycobacterium lepraemurium and the cultivable Mycobacterium smegmatis were determined following incubation in a variety of culture conditions. The AEC values for M. smegmatis were similar to those reported for other cultivable bacteria. The AEC values for M. leprae and M. lepraemurium purified from host tissue were lower than those of in vitro-grown organisms. The possible use of the AEC in in vitro studies with M. leprae is discussed.     

T-cell responsiveness in Mycobacterium lepraemurium infections in a "resistant" (CBA) and a "susceptible" (BALB/c) mouse strain

Antigen-specific and mitogen-nonspecific T-lymphocyte proliferation and lymphokine release (interleukin 2 and macrophage activation factor) were studied in BALB/c and CBA mice infected intravenously with 10(8) Mycobacterium lepraemurium organisms. The responsiveness of spleen cells from infected animals to Con A and specific MLM antigen declined as the infection progressed. Thus, the decreased responsiveness appeared earlier and was more profound in the relatively susceptible BALB/c strain than in the relatively resistant CBA strain. Nylon-wool-purified, T-cell-enriched spleen cells from both strains, however, responded to both M. lepraemurium antigen and Con A until the later stages of infection (17 weeks postinfection). The relevance of nonspecific immunodepression mediated by nylon-wool-adherent spleen cells to the progressive nature of this infection is discussed.     

Bacillary growth, interleukin 2 production defect, and specific antibody secretion governed by different genetical factors in mice infected subcutaneously with Mycobacterium lepraemurium

Different mouse strains were infected subcutaneously in the footpad with 10(7) Mycobacterium lepraemurium (MLM). At various stages of the infection, the number of acid-fast bacilli (AFB) in different organs, spleen cell interleukin 2 production, and specific IgM and IgG serum antibodies to MLM sonicate were assessed. Strains were separable into two distinct groups depending on the number of AFB recovered from the different organs, without any obvious influence of the Bcg gene. Thus C57BL/6, DBA/2, (C57BL/6 X DBA/2)F1 and C3H/Pas mice belonged to the high resistance group and DBA/1, BALB/c, and CBA strains to the low resistance group. Interleukin 2 production was depressed only in C57BL/6 and C3H/Pas mice. Anti-MLM antibody response also markedly varied according to strains, in terms of antibody titers, Ig class distribution, and species specificity, but with a different genetic pattern from that observed for MLM growth control.     

Phagosome-lysosome fusion and cyclic adenosine 3':5'-monophosphate in macrophages infected with Mycobacterium microti, Mycobacterium bovis BCG or Mycobacterium lepraemurium.

When ingested by mouse peritoneal macrophage monolayers, live Mycobacterium microti caused a sustained increase in monolayer cyclic AMP content and fusion of lysosomes with the bacterium-containing phagosomes was impaired. Ingested live M. bovis BCG caused a transient increase in cyclic AMP and the defect in phagolysosome formation was less pronounced. Dead mycobacteria and live M. lepraemurium neither enhanced monolayer cyclic AMP content nor inhibited phagolysosome formation. Mycobacterium microti and BCG exceeded M. lepraemurium in cyclic AMP-synthesizing activity in vitro but the question of whether bacterial cyclic AMP contributed substantially to the increments in infected macrophages was not resolved. Antibody-coated BCG retained the ability to synthesize cyclic AMP and to enhance monolayer cyclic AMP but lost the ability to inhibit phagolysosome formation in macrophages, The observations are discussed in terms of possible control of phagolysosome formation by cyclic nucleotides.     

Systemic changes in hydrolytic enzyme activities in mice affected with murine leprosy

In order to investigate the behavior of hydrolytic enzymes in chronic infections, the activities of 17 hydrolytic enzymes were tested in limb muscles, heart muscle, spleen, liver, and kidney of lepromatous mice infected with Mycobacterium lepraemurium (M. lepraemurium) and their controls. Typical increases in those enzymatic activities were seen in spleen and liver, where pathological changes were the most pronounced, especially at the 11th week after the inoculation of the bacilli. At the 16th week, the enzymatic changes became less remarkable probably because of the decreased viability of tissues in these organs. The enzymatic changes observed could not be explained as due to bacterial enzymes. These findings are compatible with the notion that the increases in hydrolytic enzyme activities are related to tissue damage caused by murine leprosy.     

Mouse chromosome 1 Ity locus regulates microbicidal activity of isolated peritoneal macrophages against a diverse group of intracellular and extracellular bacteria

The genotype of a mouse influences whether or not it will survive infection with the agent of murine typhoid, Salmonella typhimurium. The best-characterized murine salmonella response gene is a Chromosome 1 locus designated Ity. Inbred strains of mice that express the Itys allele are unable to contain the net growth of Salmonella typhimurium within their spleens and livers, and usually die early in the infection. By contrast, mice homozygous or heterozygous for the Ityr allele are able to control the net multiplication of Salmonella typhimurium within these organs. The Ity gene also appears to regulate the extent of replication within murine reticuloendothelial cell tissues of the obligate intracellular parasite Leishmania donovani, as well as the facultative intracellular bacteria Mycobacterium bovis and Mycobacterium lepraemurium. Previous studies from our laboratory strongly suggested that Ityr mice are more resistant to S. typhimurium infection than are Itys mice, because resident Ityr macrophages kill salmonellae more efficiently than do Itys macrophages. In this study, we used an in vitro macrophage assay to assess the specificity of the enhanced killing capacity of Ityr macrophages. We found that Ityr macrophages were better able than Itys macrophages to kill both intracellular bacteria (Salmonella typhi) and extracellular bacteria (Escherichia coli, Staphylococcus aureus, Corynebacterium diphtheriae). Thus, the diversity of organisms affected by Ity expression suggests that the product of this gene may play a key regulatory role in the initial interaction of mice with a variety of microbial agents.     

Morphological Changes of Mycobacterium lepraemurium Grown in Cultures of Mouse Peritoneal Macrophages

Studies were made on morphological changes of Mycobacterium lepraemurium grown in cultures of mouse peritoneal macrophages. Two types of nonsolid or irregularly stained M. lepraemurium were observed. One type occurred in the growth phase of the organisms during the stage of preparation for bacillary multiplication. The nonsolid bacilli appeared as elongated organisms having pointed ends, isolated acid-fast dots, or faintly stained areas at the ends of the bacilli. It is possible that this irregularity in staining is due to a very gradual, versus an instantaneous, acquisition of acid-fast material during bacillary multiplication and maturation. Solid forms were again observed upon maturation. Nonsolid bacilli were also observed in macrophage cultures infected with autoclave-killed M. lepraemurium. Under these conditions there was an emergence of organisms which showed irregularly stained areas and various forms of deformity unaccompanied by elongation or multiplication. These irregularities were most probably due to the destructive process of digestion of bacillary protoplasm. The present study does not support the current hypothesis that all nonsolid acid-fast organisms are nonviable.     

Comparative ultrastructure of Mycobacterium leprae and Mycobacterium lepraemurium cell envelopes.

The structural properties of the cell envelopes of Mycobacterium leprae and Mycobacterium lepraemurium were investigated by freeze-fracture, freeze-etching, and negative-staining techniques. Freeze-fracture split the cell wall and exposed the internal features of the peptidoglycolipid mycosidic filamentous network. The cell membrane was also split into two asymmetric faces. The external fracture face was characterized by linear arrays of intramembranous particles, whereas the protoplasmic fracture face showed randomly distributed clusters of particulate entities. Comparative analysis of the ultrastructural features observed in M. leprae and M. lepraemurium indicated that the organization of the cell envelope in these two species differed particularly with respect to the amount and complexity of the superficial peptidoglycolipid and mycosidic integument, which is poorly developed in the mycobacterium responsible for human disease.     

Effect of heat-staining procedure on the gram staining properties of mycobacteria]

Since the establishment of Gram stain by H.C.Y. Gram in 1884, it has been widely and routinely used as an aid for differentiation of bacteria. The bacteria are divided into three categories by the staining properties; Gram-positive, -negative, and -indefinite. All the text books in the world describe that mycobacteria such as M. tuberculosis are Gram-positive. By the merest chance, however, it was found that M. lepraemurium grown in tissues was not stained by the routinely used Gram staining method. Therefore, we tried to stain some of the mycobacteria by the Gram staining procedure which is widely used at present. The results obtained indicated that the mycobacteria tested were divided into three groups; the unstainable group such as M. leprae and M. lepraemurium, the Gram-positive and difficult-to-stain group which involves such slow growing mycobacteria as M. tuberculosis, M. avium, and M. intracellulare, and the Gram-indefinite group which contains such rapid growing mycobacteria as M. phlei, M. smegmatis, and M. chelonae. However, if Gram stain is carried out by the heating procedure at the first staining step, all the mycobacteria would become Gram-positive. Therefore, we emphasize that Gram staining of mycobacteria should be performed by the heating procedure.     

Detection of trehalose monomycolate in Mycobacterium leprae grown in armadillo tissues

Trehalose-6-monomycolate (TMM) was isolated from the lipids of armadillo-derived Mycobacterium leprae. Only meagre amounts of this glycolipid were recovered, but its structure was unequivocally established. Only alpha-mycolates were detected in the TMM by 252Cf plasma desorption mass spectrometry. Electron impact mass spectrometry showed the alpha branch to be principally C20. Trehalose dimycolate (cord factor) was not detectable. Since we have also found TMM in M. lepraemurium and in every Mycobacterium species so far examined, we suggest that this glycolipid is truly ubiquitous amongst mycobacteria.