Preliminary demonstration of human tuberculoimmunity in vitro

Dual RNA Sequencing of Mycobacterium tuberculosis-Infected Human Splenic Macrophages Reveals a Strain-Dependent Host-Pathogen Response to Infection

Tuberculosis (TB) is caused by Mycobacterium tuberculosis (Mtb), leading to pulmonary and extrapulmonary TB, whereby Mtb is disseminated to many other organs and tissues. Dissemination occurs early during the disease, and bacteria can be found first in the lymph nodes adjacent to the lungs and then later in the extrapulmonary organs, including the spleen. The early global gene expression response of human tissue macrophages and intracellular clinical isolates of Mtb has been poorly studied. Using dual RNA-seq, we have explored the mRNA profiles of two closely related clinical strains of the Latin American and Mediterranean (LAM) family of Mtb in infected human splenic macrophages (hSMs). This work shows that these pathogens mediate a distinct host response despite their genetic similarity. Using a genome-scale host–pathogen metabolic reconstruction to analyze the data further, we highlight that the infecting Mtb strain also determines the metabolic response of both the host and pathogen. Thus, macrophage ontogeny and the genetic-derived program of Mtb direct the host–pathogen interaction.

In vitro mycobacterial growth inhibition assays: A tool for the assessment of protective immunity and evaluation of tuberculosis vaccine efficacy

Tuberculosis (TB) continues to pose a serious global health threat, and the current vaccine, BCG, has variable efficacy. However, the development of a more effective vaccine is severely hampered by the lack of an immune correlate of protection. Candidate vaccines are currently evaluated using preclinical animal models, but experiments are long and costly and it is unclear whether the outcomes are predictive of efficacy in humans. Unlike measurements of single immunological parameters, mycobacterial growth inhibition assays (MGIAs) represent an unbiased functional approach which takes into account a range of immune mechanisms and their complex interactions. Such a controlled system offers the potential to evaluate vaccine efficacy and study mediators of protective immunity against Mycobacterium tuberculosis (M.tb). This review discusses the underlying principles and relative merits and limitations of the different published MGIAs, their demonstrated abilities to measure mycobacterial growth inhibition and vaccine efficacy, and what has been learned about the immune mechanisms involved.

Mycobacteria infect different cell types in the human lung and cause species dependent cellular changes in infected cells

Background

Mycobacterial infections remain a significant cause of morbidity and mortality worldwide. Due to limitations of the currently available model systems, there are still comparably large gaps in the knowledge about the pathogenesis of these chronic inflammatory diseases in particular with regard to the human host. Therefore, we aimed to characterize the initial phase of mycobacterial infections utilizing a human ex vivo lung tissue culture model designated STST (Short-Term Stimulation of Tissues).

Methods

Human lung tissues from 65 donors with a size of 0.5–1 cm³ were infected each with two strains of three different mycobacterial species (M. tuberculosis, M. avium, and M. abscessus), respectively. In order to preserve both morphology and nucleic acids, the HOPE® fixation technique was used. The infected tissues were analyzed using histo- and molecular-pathological methods. Immunohistochemistry was applied to identify the infected cell types.

Results

Morphologic comparisons between ex vivo incubated and non-incubated lung specimens revealed no noticeable differences. Viability of ex vivo stimulated tissues demonstrated by TUNEL-assay was acceptable. Serial sections verified sufficient diffusion of the infectious agents deep into the tissues. Infection was confirmed by Ziel Neelsen-staining and PCR to detect mycobacterial DNA. We observed the infection of different cell types, including macrophages, neutrophils, monocytes, and pneumocytes-II, which were critically dependent on the mycobacterial species used. Furthermore, different forms of nuclear alterations (karyopyknosis, karyorrhexis, karyolysis) resulting in cell death were detected in the infected cells, again with characteristic species-dependent differences.

Conclusion

We show the application of a human ex vivo tissue culture model for mycobacterial infections. The immediate primary infection of a set of different cell types and the characteristic morphologic changes observed in these infected human tissues significantly adds to the current understanding of the initial phase of human pulmonary tuberculosis. Further studies are ongoing to elucidate the molecular mechanisms involved in the early onset of mycobacterial infections in the human lung.

Effects of ascent to high altitude on human antimycobacterial immunity

BACKGROUND

Tuberculosis infection, disease and mortality are all less common at high than low altitude and ascent to high altitude was historically recommended for treatment. The immunological and mycobacterial mechanisms underlying the association between altitude and tuberculosis are unclear. We studied the effects of altitude on mycobacteria and antimycobacterial immunity.

METHODS

Antimycobacterial immunity was assayed in 15 healthy adults residing at low altitude before and after they ascended to 3400 meters; and in 47 long-term high-altitude residents. Antimycobacterial immunity was assessed as the extent to which participants' whole blood supported or restricted growth of genetically modified luminescent Bacille Calmette-Guérin (BCG) mycobacteria during 96 hours incubation. We developed a simplified whole blood assay that could be used by a technician in a low-technology setting. We used this to compare mycobacterial growth in participants' whole blood versus positive-control culture broth and versus negative-control plasma.

RESULTS

Measurements of mycobacterial luminescence predicted the number of mycobacterial colonies cultured six weeks later. At low altitude, mycobacteria grew in blood at similar rates to positive-control culture broth whereas ascent to high altitude was associated with restriction (p ≤ 0.002) of mycobacterial growth to be 4-times less than in culture broth. At low altitude, mycobacteria grew in blood 25-times more than negative-control plasma whereas ascent to high altitude was associated with restriction (p ≤ 0.01) of mycobacterial growth to be only 6-times more than in plasma. There was no evidence of differences in antimycobacterial immunity at high altitude between people who had recently ascended to high altitude versus long-term high-altitude residents.

CONCLUSIONS

An assay of luminescent mycobacterial growth in whole blood was adapted and found to be feasible in low-resource settings. This demonstrated that ascent to or residence at high altitude was associated with decreased mycobacterial growth in whole blood relative to controls, consistent with altitude-related augmentation of antimycobacterial cellular immunity.

Interferon-gamma: a historical perspective

This article reviews the main lines of thinking and exploration that have led to our current conception of the role of IFN-gamma in immune defense and autoimmunity. In 1965 the first report appeared describing production of an interferon-like virus inhibitor in cultured human leukocytes following exposure to the mitogen phytohemagglutinin. In the early 1970s the active principle became recognized as being distinct from classical virus-induced interferons, leading to its designation as immune interferon or Type II interferon, and eventually IFN-gamma. Up to that point interest in the factor had come almost exclusively from virologists, in particular those among them who were believers in interferon. Evidence first coming forward in the 1980s that IFN-gamma is indistinguishable from macrophage-activating factor (MAF), then a prototype lymphokine, was the signal for immunologists at large to become interested. Today IFN-gamma ranks among the most important endogenous regulators of immune responses.

Macrophage migration inhibitory factor reduces the growth of virulent Mycobacterium tuberculosis in human macrophages

Macrophage migration inhibitory factor (MIF) is a key mediator of the innate immune system and plays a crucial role in the host response to bacterial infections. Its role in immunity to intracellular pathogens has not been well studied. Here, we show that MIF released by infected human macrophages inhibits the growth of virulent Mycobacterium tuberculosis.

The modelling of mononuclear phagocyte-connective tissue adhesion in vitro: application to disclose a specific inhibitory effect of Leishmania infection

In this work, we have developed an adhesion assay to study interactions between mononuclear phagocytes and connective tissue in vitro and show its potential use to study diseases caused by intracellular microorganisms. The assay reproduces most of the characteristics of macrophage adhesion to connective tissue in vivo, such as: preferential adhesion to inflamed connective tissue, divalent cation and integrin dependence, and up-regulation upon cell activation. The phagocyte adhesion to connective tissue was inhibited by infection with Leishmania (58+/-22%, p < 0.05) and was not affected by infection with Mycobacterium or by endocytosis of latex beads. Manganese partially reverted the loss in adherence produced by Leishmania infection, indicating that the mechanisms regulating the function of integrins are affected by cell infection with Leishmania. This assay might be a useful tool for the study of the mechanisms by which mononuclear phagocytes play a role in the immune-inflammatory response and in the development of lesions.

Virulent Mycobacterium fortuitum restricts NO production by a gamma interferon-activated J774 cell line and phagosome-lysosome fusion

The virulence of different isolates of Mycobacterium has been associated with two morphologically distinguishable colonial variants: opaque (SmOp) and transparent (SmTr). In this report we used an in vitro assay to compare macrophage (Mphi) responses to SmOp and SmTr Mycobacterium fortuitum variants, taking advantage of the fact that these variants were derived from the same isolate. Cells preactivated or not with gamma interferon (IFN-gamma) were infected with SmOp or SmTr M. fortuitum. We showed that SmOp and SmTr induced different levels of nitric oxide (NO) production by IFN-gamma-stimulated Mphi. Indeed, the amount of IFN-gamma-induced NO production by J774 cells was 4.8 to 9.0 times higher by SmOp (23.1 to 37.7 micro M) compared to SmTr infection (3.9 to 4.8 micro M) (P = 0.0332), indicating that virulent SmTr bacilli restricted NO production. In addition, IFN-gamma-induced NO production by Mphi was higher when correlated with reduction of only avirulent SmOp bacillus viability. SNAP (S-nitroso-N-acetyl-DL-penicillamine)-induced NO production did not modify SmTr viability, indicating its resistance to nitrogen radicals. Electron microscopy studies were performed to evaluate the capacity of phagosomes to fuse with lysosomes labeled with bovine serum albumin-colloidal gold particles. By 24 h postinfection, 69% more phagosome-containing SmOp variant had fused with lysosomes compared to the SmTr-induced phagosomes. In conclusion, these data indicate that virulent SmTr bacilli may escape host defense by restricting IFN-gamma-induced NO production, resisting nitrogen toxic radicals, and limiting phagosome fusion with lysosomes.

The receptor-mediated uptake, survival, replication, and drug sensitivity of Mycobacterium tuberculosis within the macrophage-like cell line THP-1: a comparison with human monocyte-derived macrophages

We have compared the interaction of Mycobacterium tuberculosis with the human macrophage-like cell line THP-1 and with human monocyte-derived macrophages (MDM). The association of M. tuberculosis with THP-1 and MDM was comparable in both the presence and the absence of serum. For both cells, serum-mediated binding was much greater than nonopsonic binding and was mediated by a heat-labile serum component. Nonopsonic binding of M. tuberculosis to both cells could be inhibited by antibodies recognizing CD11b and by mannan and glucan. Intracellular M. tuberculosis grew progressively in infected MDM and THP-1 cells. Treatment of the infected MDM and THP-1 cells with the anti-mycobacterial isoniazid resulted in the rapid killing of the intracellular mycobacteria. Differentiated, adherent THP-1 cells bound IgG and complement-coated particles at levels similar to those of MDM. However, binding of zymosan by THP-1 cells was significantly lower than that seen for MDM.

CD4(+) T cell and natural killer cell-dependent killing of Mycobacterium tuberculosis by human monocytes

We established an in vitro model of the phagocytosis of Mycobacterium tuberculosis by human peripheral blood monocytes to evaluate the subsequent inhibition of intracellular replication of the organism. Highly purified T cells (94% CD3(+)/CD16(-)) or natural killer (NK) cells (96% CD16(+)/CD3(-)) isolated by Percoll discontinuous density gradient of peripheral blood mononuclear cells were incubated with M. tuberculosis-infected monocyte monolayers. Monocytes were lysed immediately and at 4, 7, and 10 d after infection for quantification of intracellular replication, which was assessed by quantitative plating techniques as colony-forming units (CFU). Whereas control monocytes permitted intracellular replication, T cells activated monocytes to kill 77% (p < 0.01) of intracellular M. tuberculosis compared with control monocytes by 10 d after infection. NK cells activated monocytes to kill 84% (p < 0.01) of M. tuberculosis in comparison with control monocytes. Lymphokine (IL-2)-activated-killer (LAK) cells were capable of activating monocytes to kill 97% (p < 0.01) of the intracellular organisms compared with control monocytes. In purified protein derivative (PPD)-positive donors, PPD-specific-CD4(+) lymphocytes stimulated monocytes to kill intracellular M. tuberculosis in a Class II major histocompatibility complex-restricted manner. In contrast, in PPD-negative donors, CD4(-) lymphocytes activated monocytes in a genetically unrestricted manner. Both T cell supernatant and NK cell supernatant generated from cocultivation with M. tuberculosis-infected monocytes also activated monocytes to augment mycobactericidal function. In conclusion, T cells, NK cells, LAK cells, and their supernatants activated mycobactericidal function of monocytes, although these pathways of activation differed in terms of antigenic specificity and genetic restriction.

Lymphocyte-Dependent Inhibition of Growth of Virulent Mycobacterium tuberculosis H37Rv Within Human Monocytes: Requirement for CD4+ T Cells in Purified Protein Derivative-Positive, But Not in Purified Protein Derivative-Negative Subjects

Protective human immunity to Mycobacterium tuberculosis(M. tb) has proven difficult to characterize, in part because of technical obstacles to in vitro infection of human cells with virulent M. tb. We established a reproducible method of infecting human monocytes (MN) with the virulent M. tb strain H37Rv that did not reduce MN viability. TNF-α had no effect on replication of H37Rv within MN, and IFN-γ mediated only a 1.9-fold reduction in bacterial growth. In contrast, nonadherent cells (NAC) from purified protein derivative (PPD)-positive and PPD-negative subjects reduced intracellular growth of H37Rv by 6- and 10.6-fold, respectively (p = 0.007 and p = 0.005). CD4+ T cells were essential to growth inhibition mediated by NAC of PPD-positive subjects, whereas containment of M. tb by NAC of PPD-negative subjects did not require CD4+ cells. CD8+ T cells did not contribute to protection mediated by NAC of either group. Supernatants of cocultured H37Rv-infected MN and NAC only partially reduced intracellular growth of M. tb despite containing nanogram concentrations of TNF-α and IFN-γ. Neutralizing antibodies to TNF-α, IFN-γ, and IL-12 failed to affect the NAC-mediated growth limitation. NAC treated with emetine retained approximately 40% of their capacity to contain intracellular H37Rv, however. These studies indicate that protective human recall responses to M. tb are mediated primarily by CD4+ T cells, whereas CD4−CD8− lymphocytes may contribute to innate immunity to M. tb. The ability of NAC to activate M. tb-infected MN is only partly attributable to soluble mediators and may also involve contact-mediated mechanisms.

Expression of virulence of Mycobacterium tuberculosis within human monocytes: virulence correlates with intracellular growth and induction of tumor necrosis factor alpha but not with evasion of lymphocyte-dependent monocyte effector functions

We assessed the applicability of an in vitro model of low-level infection of human monocytes to the characterization of the virulence of strains of the Mycobacterium tuberculosis family. Peripheral blood monocytes were infected at a 1:1 ratio with the virulent M. tuberculosis strain H37Rv, the avirulent M. tuberculosis strain H37Ra, and the attenuated M. bovis strain BCG. Both the percentages of cells infected by the three strains and the initial numbers of intracellular organisms were equivalent, as were levels of monocyte viability up to 7 days following infection. Intracellular growth reflected virulence, as H37Rv replicated in logarithmic fashion throughout the assay, BCG growth reached a plateau at 4 days, and H37Ra did not grow at all. The same patterns of growth were observed following infection of human alveolar macrophages with H37Rv and H37Ra. Monocyte production of tumor necrosis factor alpha was significantly higher following infection with virulent H37Rv than with either BCG or H37Ra. In contrast, there was no clear correlation of interleukin 10 production with virulence. Nonadherent cells of purified-protein-derivative-positive donors mediated equivalent degrees of reduction of the intracellular growth of H37Rv, BCG, and H37Ra. Low-level infection of human monocytes with H37Rv, BCG, and H37Ra thus provides an in vitro model for assessment of the virulence of these M. tuberculosis family strains. Furthermore, it is suggested that the virulence of these strains is expressed primarily by their differing abilities to adapt to the intracellular environment of the mononuclear phagocyte.

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.

Intracellular Antimycobacterial Activity of Ciprofloxacin and Ofloxacin in Mycobacterium Fortuitum Infected Human Polymorphonuclear Leucocytes

The broadspectrum quinolone antibiotics ciprofloxacin and ofloxacin were tested for activity against the atypical mycobacterium M.fortuitum. In vitro minimal inhibitory concentrations (MIC) were done in Brain Heart Infusion broth and intracellular determinations in Medium 199 cell culture medium. The PMNs with intracellular bacteria and controls with or without drugs were incubated for six hours at 37°C. Hourly, 0.1 ml aliquotes were taken for colony forming units (cfu) assays. In vitro and intracellular MIC's for ciprofloxacin were 0.125mg/l and 0.625 mg/l respectively, while for ofloxacin they were 0.2mg/l and 0.4 mg/l, respectively.

Generation of reactive oxygen intermediates in relation to short course chemotherapy in children suffering from pulmonary tuberculosis

Functional status of phagocytes in relation to 6 months' short course chemotherapy of tuberculosis was studied with special reference to antigen-5 (Ag-5) of Mycobacterium tuberculosis. Phagocytic capacity and overall generation of reactive oxygen intermediates (ROI) measured as chemiluminescence (CL) response was studied in peripheral blood monocytes obtained from 20 children with pulmonary tuberculosis (PTb) and was compared with 20, age and sex matched, controls. In untreated children the CL response (mean +/- SD) with latex (0.90 +/- 0.08) and Ag-5 (0.99 +/- 0.11) was found to be severely depressed compared with controls (Latex, 19.2 +/- 5.10; Ag-5, 48.12 +/- 7.10). A significant improvement was seen in response to both the stimulants (Latex, 15.20 +/- 1.50; Ag-5, 28.15 +/- 7.32) after 3 months of therapy and became equal to, or slightly higher than, the values obtained with controls by the end of therapy. This study suggests that newly diagnosed untreated PTb is associated with an in vitro antigen specific compromise of phagocytic capacity and oxidative metabolic burst activity that is gradually and progressively corrected during the course of effective short course chemotherapy. In addition, Ag-5 is a potent stimulator of monocytes/macrophages; its potency being far greater than latex.

Inhibitory and bactericidal activities of levofloxacin against Mycobacterium tuberculosis in vitro and in human macrophages

Levofloxacin exhibited twofold greater inhibitory and bactericidal activities than ofloxacin against either extracellular or intracellular tubercle bacilli. The activities of both drugs against extracellular and intracellular bacteria were about the same, despite the accumulation of the drugs in macrophages at a level four- to fivefold greater than that in the extracellular medium. The activities of both drugs against intracellular bacteria were largely associated with the short, 2-h pulsed exposures of the infected macrophages to the concentrations which correspond to those attainable in blood during the period of the maximum concentration of drug in serum.

Inhibition of intracellular growth of Mycobacterium avium by one pulsed exposure of infected macrophages to clarithromycin

A single 2-h pulsed exposure of either human monocyte-derived macrophages or J774 cells infected with Mycobacterium avium to clarithromycin at 3.0 micrograms/ml completely inhibited the intracellular bacterial growth during the first four days of observation, and then only a slight increase in the number of CFU per milliliter took place between the fourth and seventh days. These data suggest that in vivo the intracellular bacteria can be effectively inhibited after a short period when the concentration of the drug in blood reaches its maximum. On the basis of these data, the assumptions that the elimination of bacteremia observed in clarithromycin clinical trials is a result of the activity of the drug not only against bacteria in blood but in macrophages as well and that the peak concentration attainable in blood is essential for these effects can be made.

Assessment of mycobacterial infection and multiplication in macrophages by polymerase chain reaction

The amplification of mycobacterium-specific DNA sequences from samples obtained from infected patients by the polymerase chain reaction (PCR) has been useful in the clinical diagnosis of mycobacterial diseases. Using 20 bp oligonucleotide primers that recognize a 123 bp repeated sequence present in M. bovis and M. tuberculosis DNA, we describe in detail the conditions of the PCR reaction that allow an assessment of the mycobacterial content of infected macrophages. The results of the highly reproducible, time-efficient PCR technique show good correlation with the widely used colony forming unit (CFU) and [3H]uracil incorporation methods for the detection of Mycobacterium. Our method allows an assessment of the level of M. bovis BCG infection from a variety of sources, including peritoneal macrophages and macrophage lines, within a few hours, making it the assay of choice for rapid determination of the level of mycobacterial growth in infected cells, in experimental models of mycobacterial infection.

Impaired erythropoiesis in the acquired immunodeficiency syndrome with disseminated Mycobacterium avium complex

PURPOSE

Anemia is an important negative predictor for survival with disseminated Mycobacterium avium complex (MAC) infection in the acquired immunodeficiency syndrome (AIDS). We analyzed the differences in AIDS patients with and without MAC infection with regard to anemia, severity of human immunodeficiency virus (HIV) infection, bone marrow morphology, and bone marrow erythroid progenitor colony growth (BFU-E and CFU-E). In addition, we determined the in vitro effect of sera obtained from these patients on normal BFU-E and CFU-E. A possible role of macrophages in the suppression of erythropoiesis was examined by studying in vitro the effect of supernatants from MAC-infected macrophages on cultured BFU-E and CFU-E.

PATIENTS AND METHODS

Hematocrit, serum levels of p24 antigen, erythropoietin, and CD4-positive cell count were determined in 14 AIDS patients with and 24 without MAC infection. Bone marrow erythropoietic and granulocytic progenitor cells from 15 normal individuals, from 12 AIDS patients with MAC infection, and from 10 AIDS patients without MAC infection were cultured on methylcellulose. In addition, progenitor cells from normal individuals were cultured in the presence, and in the absence, of sera obtained from AIDS patients with (14), or without (24), MAC infection. Last, we studied the effect of supernatants (SNs) from MAC and Mycobacterium tuberculosis-infected macrophages on erythropoietic progenitor cell growth.

RESULTS

The anemia in AIDS patients with MAC infection was associated with a selective suppression of erythropoietic progenitors despite bone marrow morphology that was indistinguishable from that in patients without MAC infection. The degree of anemia could not be explained on the basis of severity of HIV infection or a deficiency of erythropoietin production. Bone marrow mononuclear cells from AIDS patients with MAC generated significantly fewer erythroid progenitor colonies (BFU-E and CFU-E) than equivalent cells from AIDS patients without MAC infection (p < 0.05). Sera from MAC-infected AIDS patients were markedly inhibitory to the erythroid progenitors as compared with sera from patients without MAC infection (p < 0.001). SNs from MAC-infected macrophages were markedly inhibitory to the erythroid progenitors (BFU-E and CFU-E) as compared with the myeloid progenitors (CFU-GM).

CONCLUSION

The profound anemia in MAC-infected AIDS patients is due to suppression of erythroid progenitors by a soluble factor(s) in the serum. The data suggest that the soluble factor(s) is probably elaborated by macrophages.

MICs and MBCs of clarithromycin against Mycobacterium avium within human macrophages

The inhibitory and bactericidal activities of clarithromycin were determined quantitatively against the intracellular populations of five Mycobacterium avium strains growing in monocyte-derived human macrophages. The MICs were 1.0 microgram/ml, and the MBCs ranged from 16.0 to 64.0 micrograms/ml; these values were similar to the MICs and MBCs found in broth cultures at pH 7.4 and were substantially lower than those found in broth cultures at pHs 6.8 and 5.0. Since the intracellular environment has a neutral or even an acidic pH, relatively low MICs and MBCs found in macrophage cultures can be associated with the fact that the drug concentrations in macrophages are substantially higher than those in the medium in which these cells are cultivated. Pretreatment of the macrophages 2 days prior to infection decreased the MICs twofold in comparison with results of experiments in which the drug was added to already infected macrophages.

Mycobacterial proliferation in macrophages is prevented by incubation with lymphocytes activated in vitro with a mycobacterial antigen complex

Antigen A60 from Mycobacterium bovis bacillus Calmette Guérin was shown to trigger both humoral and cellular immune reactions. We explored the ability of A60 to block intracellular proliferation of phagocytosed mycobacteria with a model system involving peritoneal murine macrophages infected with Mycobacterium avium. Mixed lymphocytes from lymph nodes of mice inoculated with A60 hindered intracellular proliferation of this mycobacterium, owing to A60-specific cells, proliferation of which was induced in vitro in an antigen concentration-dependent manner. The lymphokines released by A60-stimulated T lymphocytes in vitro were identified as interleukin 2 (IL2) and interferon-gamma (IFN-gamma): their production showed a clear A60 dose dependence. When supernatants of such induced lymphocyte cultures were incubated with anti-IFN-gamma antibodies, macrophage activation was prevented, whereas anti-IL 2 immunoglobulin had little effect. Treatment of infected macrophages with recombinant IFN-gamma reduced intracellular proliferation of mycobacteria, while exogenous IL 2 and tumor necrosis factor were ineffective. Therefore, A60 elicits in vitro proliferation of T lymphocytes responding specifically to this antigen with production of IFN-gamma, which in turn activates macrophages and prevents multiplication of phagocytosed mycobacteria.

Microtiter plate assay for selecting "macrophage virulent" strains of Mycobacterium avium intracellulare mycobacteria in mouse pulmonary alveolar macrophages

Currently used macrophage-mycobacterial in vitro infection models require substantial numbers of macrophages. We developed a miniaturized version of such a model, using microtiter plates, which is comparable to standardly published methods, is reproducible, and requires fewer macrophages. In addition to its ease of handling and its economy in time, number of animals, and supplies, this method is preferable when limited numbers of macrophages are available. We have used this assay as a means of selecting human derived isolates from patients with M. avium intracellulare pulmonary disease for their ability to infect and multiply in cultured mouse pulmonary alveolar macrophages.

1,25 Dihydroxyvitamin D3-dependent inhibition of growth or killing of Mycobacterium avium complex in human macrophages is mediated by TNF and GM-CSF

Vitamin D3 (D3) has been shown to activate several macrophage functions. To determine whether D3 could activate macrophages to kill or inhibit intracellular growth of Mycobacterium avium complex (MAC), human monocyte-derived macrophages were treated with D3 (10(-7), 10(-8), and 10(-9) M) 24 hr before or for 48 hr after MAC infection. All three concentrations were associated with inhibition of growth or killing of MAC in a dose-dependent fashion (28 +/- 4% and 22 +/- 3% of killing and inhibition of growth, respectively, at pharmacological concentrations) when added to the monolayer before injection or 60.4 +/- 6%, 50.4 +/- 3%, and 41.4 +/- 6%, respectively, when added to the monolayers after infection. We found that D3-treated macrophages produced increased concentrations of tumor necrosis factor (TNF) and granulocyte-monocyte colony stimulating factor (GM-CSF). Subsequently, macrophages were activated by D3 in the presence of anti-TNF or anti-GM-CSF antibody: At 10(-9) M of D3 there was no inhibition of D3-dependent macrophage activation by anti-TNF antibody, whereas anti-GM-CSF antibody was associated with 100% inhibition. At 10(-8) M of D3, anti-TNF antibody inhibited 35 +/- 6% of killing, and anti-GM-CSF antibody was associated with 100% inhibition. At 10(-7) M of D3, anti-TNF antibody inhibited 58 +/- 4% and anti-GM-CSF antibody 89 +/- 3% of killing. D3 treatment is associated with anti-MAC activity in human macrophages, and this activity appears to be mediated by both TNF and GM-CSF.

Relative permissiveness of macrophages from black and white people for virulent tubercle bacilli

Epidemiological, clinical, and histopathological evidence suggests that black people are more susceptible to tuberculosis than are white people. The cellular basis of this putative susceptibility was investigated in vitro by comparing responses of blood-derived macrophages from black and white donors to experimental infection with virulent tubercle bacilli. Phagocytes from pairs of black and white donors were infected. The uptake and replication of the tubercle bacilli in these cells were measured by microscopic counts and by CFU counts of bacilli at 0, 4, and 7 days. The effects of donor serum, of 1,25-(OH)2-vitamin D3, and gamma interferon on the infection also were studied. Black-donor phagocytes killed more bacilli during phagocytosis than white-donor phagocytes did. However, the bacilli grew consistently and significantly faster in successfully infected macrophages from black than from white donors, especially in the presence of black-donor serum. 1,25-(OH)2-vitamin D3 gave significantly less protection against tubercle bacilli to macrophages from black donors than to macrophages from white donors. The permissiveness of the macrophages from the two races was affected equally by gamma interferon. These results demonstrate some inherent and environmental liabilities in the monocytic phagocytes and serum of black people compared with white people, which may contribute to their greater susceptibility to tuberculosis.

Pathogenicity of Mycobacterium avium for human monocytes: absence of macrophage-activating factor activity of gamma interferon

Mycobacterium avium is a frequent opportunistic pathogen in the acquired immunodeficiency syndrome (AIDS). We compared 12 strains of M. avium in an in vitro model of pathogenicity. Peripheral blood-derived monocytes from healthy individuals were infected with M. avium in vitro. Bacterial uptake and intracellular replication were assessed by microscopic count of acid-fast bacilli and CFU of bacteria, respectively, in lysed monocytes. The CFU assay showed that among five AIDS-associated strains, only one replicated in monocytes. Two of seven non-AIDS-associated strains replicated intracellularly. In addition, we examined the effect of gamma interferon (IFN-gamma) on M. avium infection. IFN-gamma treatment of monocytes decreased phagocytosis and had no effect on the intracellular replication of M. avium. Thus, most strains of M. avium do not multiply within monocytes from healthy individuals and IFN-gamma does not have macrophage-activating factor activity for M. avium infection of human monocytes.

Growth of Mycobacterium avium in activated macrophages harvested from inbred mice with differing innate susceptibilities to mycobacterial infection

The growth of Mycobacterium avium in macrophages obtained from Mycobacterium bovis BCG-infected mice was compared with that in macrophages from uninfected mice. BCG vaccination resulted in substantial macrophage activation, measured as increased acid phosphatase and superoxide anion production, as well as enhanced leishmanicidal activity. However, the activated macrophages were only able to reduce the rate of intracellular growth by Listeria monocytogenes and M. avium in vivo and did not express detectable levels of mycobactericidal activity in vitro. Exposure of the macrophage monolayers to concanavalin A-stimulated spleen cell supernatant fluid and lipopolysaccharide did not further enhance the ability of the BCG-activated macrophages to control the intracellular replication of the M. avium. Macrophages from BCG-infected C57BL/6 (BCGs) mice were quantitatively better able to control the intracellular replication of the M. avium challenge than were similar phagocytes obtained from BCGr (A/J) mice. These findings have important implications with respect to the expression of acquired resistance to these atypical mycobacterial infections.

Cytokine regulation of the intracellular growth of Mycobacterium paratuberculosis in bovine monocytes

In this study we examined the influence of various crude and recombinant cytokines on the ingestion and intracellular survival of Mycobacterium paratuberculosis within bovine monocytes and monocyte-derived macrophages. Cytokine pretreatment had little effect on the ingestion of M. paratuberculosis by bovine monocytes and macrophages. Monocytes that were continuously incubated with virus-induced crude bovine interferon (100 U) or recombinant bovine alpha interferon (100 U) significantly restricted the subsequent intracellular growth of M. paratuberculosis, as determined by microscopic counts of acid-fast bacilli and by recovery of CFU from lysed monocyte monolayers. In contrast to their effects on freshly adherent monocytes, these cytokines had little effect on the growth of M. paratuberculosis within monocyte-derived macrophages. In two separate experiments, we also observed inhibition of bacillary growth in monocytes treated with unpurified recombinant human granulocyte-macrophage colony-stimulating factor. Conversely, intracellular growth of M. paratuberculosis was enhanced in monocytes that were pretreated with culture supernatants from M. paratuberculosis-stimulated peripheral blood mononuclear cells obtained from an immunized calf. The growth-enhancing activity of these supernatants was labile at pH 2.0, suggesting a role for gamma interferon; however, subsequent experiments indicated that recombinant gamma interferon alone neither enhanced nor restricted intracellular bacillary growth. To determine the possible contributions of monocyte oxidative activity to cytokine-induced bacteriostasis, we compared the release of superoxide anion from cytokine-treated and control monocytes. No obvious relationship was observed between the release of superoxide anion and the subsequent intracellular fate of the bacilli.

Inhibition by 1,25(OH)2-vitamin D3 of the multiplication of virulent tubercle bacilli in cultured human macrophages

Historically, sunlight has seemed to fortify antituberculosis resistance. Evidence is presented here suggesting a role for vitamin D in this effect. The active metabolite of this photosynthesized vitamin, 1,25-dihydroxy-vitamin D3 (1,25D), promotes maturation and activation of human monocytes and macrophages (MPs). Therefore, it was tested for ability to protect MPs against virulent tubercle bacilli. MPs were derived by 7-day culture from blood monocytes, infected with the bacilli, and exposed to 1,25D in several regimens. Their inhibition of bacilli was measured by lysing samples of the cultures at 0, 4, and 7 days after infection and making bacillary CFU counts from serial dilutions of the lysates. 1,25D enabled MPs to slow or stop bacillary replication. Autologous serum supported the 1,25D-induced protection because the vitamin was not effective in medium supplemented with a serum substitute and was less effective in a heterologous AB serum than in autologous serum. The protection developed rapidly and could be induced even when 1,25D was added 3 days after infection. A concentration on the order of 4 micrograms/ml was needed for protection by the regimens used in these experiments. That is considerably higher than normal circulating concentrations of 1,25D but could be reached in infectious granulomas, because MPs can make 1,25D from precursor 25-hydroxyvitamin D3. The precursor circulates at levels 10(3) higher than those of 1,25D and is directly influenced by dietary intake or photosynthetic production of vitamin D. These results identify 1,25D as an immunomodulator which can reproducibly activate human MPs to express tuberculoimmunity. They connect vitamin D, sunlight, and tuberculoimmunity and suggest that vitamin D should be considered a vital factor in the practical control of tuberculosis.

Ingestion and intracellular growth of Mycobacterium paratuberculosis within bovine blood monocytes and monocyte-derived macrophages

Cellular immunity is thought to be of major importance in resistance to infection with Mycobacterium paratuberculosis, the causative agent of Johne's disease of ruminants. The results of this study clarify the influence of bovine mononuclear phagocyte maturation on the ingestion and intracellular survival of M. paratuberculosis in vitro. Optimal phagocytosis of M. paratuberculosis by cultured bovine blood monocytes and monocyte-derived macrophages required the presence of 5 to 20% serum; few bacilli were phagocytized in the absence of serum. Monocyte-derived macrophages consistently demonstrated greater phagocytosis of M. paratuberculosis than did freshly adherent monocytes. Ingested M. paratuberculosis multiplied approximately 200 to 250% over a 7-day incubation period within bovine monocytes and monocyte-derived macrophages, as determined by microscopic counts of acid-fast-stained monocyte monolayers and by plate counts of viable organisms. These findings suggest that resident macrophages and recently emigrated blood monocytes within the intestinal mucosa may have considerable ability to ingest M. paratuberculosis, but they are unlikely to kill or markedly restrict the intracellular growth of the ingested bacilli. The ability of these mononuclear phagocytes to provide an intracellular niche for the growth of M. paratuberculosis and the immune response that eventually develops are likely to be important components in the development of the granulomatous lesions that are characteristic of Johne's disease.

Inhibition of virulent Mycobacterium tuberculosis by murine peritoneal macrophages and human alveolar lavage cells: the effects of lymphokines and recombinant gamma interferon

Both murine peritoneal macrophages and human alveolar lavage cells inhibited growth of M. tuberculosis in a medium containing 10% foetal calf serum. However, whereas addition of recombinant gamma interferon or crude lymphokine reproducibly activated further strong anti-mycobacterial mechanisms in the murine cells, these stimuli had weak and variable effects on human alveolar cells.

Comparison of 15 laboratory and patient-derived strains of Mycobacterium avium for ability to infect and multiply in cultured human macrophages

Mycobacterium avium is a cause of nontuberculous chronic granulomatous infections which is attracting increased attention as a frequent opportunistic pathogen in acquired immunodeficiency syndrome. Some important aspects of its human pathogenicity were investigated by using cultured human macrophages infected with it. The uptake and replication of various strains of M. avium in the macrophages could be measured by CFU counts of the bacteria in samples of lysed, sonicated macrophages. Microscopic counts of acid-fast bacilli were not useful because the bacteria multiplying in the macrophages were usually not acid fast. Electron microscopy showed the intracellular bacilli to multiply by transverse fission, to be surrounded in individual vacuoles by a broad electronlucent zone, and to have thinner cell walls than extracellularly grown M. avium. Fifteen strains, including examples of serovars 1, 2, 4, 8, and 9, were studied for uptake and rate of replication in cultured macrophages from three normal subjects. The strains were isolates from patients with nontuberculous granulomatous infection, acquired immunodeficiency syndrome, or unrelated problems, or they were laboratory reference cultures. There were no differences among them in phagocytosis, but there were differences in intracellular replication. Laboratory strains tended to be avirulent, that is, they did not replicate in the macrophages. Patient isolates usually were virulent and could be compared for virulence by intracellular replication rates. Virulence correlated with flat, transparent bacterial colony morphology on nutrient agar but not with serovar or kind of patient from whom the bacteria were isolated. However, among strains of transparent colony morphology there were wide differences in virulence. A virulent bacilli generally produced domed, opalescent colonies on nutrient agar. A virulent bacilli predominated in populations of M. avium conditioned to growth in bacteriologic culture medium. Bacilli of virulent colony morphology predominated in populations passaged through cultured macrophages. The model described here presents a new approach to the investigation of the pathogenicity of M. avium for human subjects and may be more patient relevant than animal models.

Activation of macrophages to inhibit proliferation of Mycobacterium tuberculosis: comparison of the effects of recombinant gamma-interferon on human monocytes and murine peritoneal macrophages

When cultured in 20% heat-inactivated human serum, human monocytes from seven donors were not on average significantly different from non-activated murine peritoneal cells (cultured simultaneously and in an identical manner) in their ability to inhibit BCG and, when calculated relative to growth of bacilli in the same medium without macrophages, to enhance the growth of Mycobacterium tuberculosis. Recombinant gamma-interferon caused marked inhibition of virulent M. tuberculosis by murine (BALB/c) peritoneal macrophages. This effect was seen, whether the cells were cultured in 10% fetal calf serum or in 20% heat-inactivated normal human serum, with or without the addition of iron supplements. However, unlike murine cells, the addition of crude lymphokine or recombinant gamma-interferon to human monocytes caused only weak inhibition of M. tuberculosis, and in some instances, gamma-interferon caused enhancement of growth of the bacilli. Monocytes were only slightly more effective if precultured for 4-8 days before the addition of the activating stimulus. This relative failure to develop anti-mycobacterial mechanisms occurred in spite of the activation of the cells as shown by a massive increase in reduction of nitro-blue tetrazolium inducible by phorbol myristate acetate.

Gamma interferon activates human macrophages to become tumoricidal and leishmanicidal but enhances replication of macrophage-associated mycobacteria

Recombinant human gamma interferon (rIFN-gamma) was examined for its ability to activate human peripheral blood monocyte-derived macrophages to kill tumor cells and to affect the replication of two phylogenetically distinct intracellular pathogens, Mycobacterium tuberculosis and Leishmania donovani. Macrophages preincubated overnight with doses of rIFN-gamma from 5 to 500 U/ml killed [3H]thymidine-labeled mouse L929 tumor targets, as measured by the release of [3H]thymidine into the supernatant after 48 h. Counts of macrophages initially infected with leishmania promastigotes showed that rIFN-gamma-pretreated macrophages could both inhibit the replication of and kill the resulting intramacrophage amastigotes over a 7-day period. However, rIFN-gamma pretreatment of macrophages actually enhanced mycobacterial replication over a 5- to 7-day period, as assessed by (i) counting acid-fast bacilli or (ii) lysing macrophages to release bacteria and determining the numbers of viable units. Mycobacterial growth was not affected by rIFN-gamma in the absence of macrophages. rIFN-gamma pretreatment had opposite effects on the uptake of mycobacteria and leishmania. As many as 80% fewer activated macrophages ingested mycobacteria compared with controls, whereas 50% more activated macrophages were infected with leishmania. These results suggest that rIFN-gamma may interfere with the immune destruction of intracellular tubercle bacilli and that the mechanisms of immunity against mycobacteria and leishmania may differ.

Biological, chemical, immunological and staining properties of bacteria isolated from tissues of leprosy patients

Two kinds of microorganisms are found in tissue of leprosy patients: Mycobacterium leprae (ML) and leprosy derived corynebacteria (LDC). ML from untreated patients has an alcohol-acid-fastness, which is lost upon treatment with antibiotics and immune response (tuberculoid leprosy). Vulnerable ML thus produced can be reversibly de-stained by organic solvent: in tissue sections from tuberculoid and treated patients, more bacteria are, thus, revealed by the Wade-Fite than by the Ziehl-Neelsen procedure. Organisms of genera Corynebacterium, Mycobacterium and Nocardia (CMN group), have DNA with %GC contents of 50-70, 69-72, and 68-70 respectively. GC values of DNA from ML and LDC are close to 56%. DNA from different LDC strains display high homology among them and low homology with reference corynebacteria. CMN cell wall consists of interconnected peptidoglycan and polysaccharide-mycolate complex. Peptidoglycan of LDC (and known CMN) has the polysaccharide backbone linked to a tetrapeptide of L-Ala, D-Glu, m-DAP (meso-diaminopimelate), D-Ala. In ML, L-Ala is replaced by glycine. Mycobacterial wall polysaccharides (that of ML is unknown) are branched arabinogalactans with end arabinoses linked to C70 to C90 mycolates. LDC peripheral polysaccharides are arabinogalactomannans with arabinose and mannose lateral strands. Mycolic acids of LDC are of corynomycolic type (C32, C34 and C36 with 1-4 double bonds) and those of ML are of mycobacterial type. Components of CMN wall and cytoplasm are immunologically active as antigens (polysaccharides, proteins), haptens (lipids) and adjuvants (peptidoglycans). Strong intrageneric and weak intergenera crossreactions are observed among CMN bacteria: LDC preparations, however, crossreact strongly with ML and mycobacteria, and weakly with reference corynebacteria. LDC in leprosy tissues can, thus, be revealed as well by fluorescent anti-LDC antisera as by anti-ML antisera. The main crossreacting component is antigen M1 of LDC, which corresponds to antigens Ag 7 of ML and Ag60 of BCG, the active components of lepromin and tuberculin (known reagents for cutaneous tests). Antigen M1 has a polysaccharide moiety crossreacting with the wall polysaccharide of LDC.(ABSTRACT TRUNCATED AT 400 WORDS)

Interaction of human leukocytes and Entamoeba histolytica. Killing of virulent amebae by the activated macrophage

Capable effector mechanisms in the human immune response against the cytolytic, protozoan parasite Entamoeba histolytica have not been described. To identify a competent human effector cell, we studied the in vitro interactions of normal human polymorphonuclear neutrophils, peripheral blood mononuclear cells (PBMC), monocytes (MC), and MC-derived macrophages with virulent axenic amebae (strain HMI-IMSS). Amebae killed neutrophils, PBMC, MC, and MC-derived macrophages (P less than 0.001), without loss of parasite viability. The addition of heat-inactivated immune serum did not enable leukocytes to kill amebae, nor did it protect these host cells from amebae. MC-derived macrophages, activated with lymphokine elicited by the mitogens conconavalin A, phytohemagglutinin, or an amebic soluble protein preparation (strain HK9), killed 55% of amebae by 3 h in a trypan blue exclusion assay (P less than 0.001); during this time, 40% of the activated macrophages died. Lysis of amebae was confirmed using 111Indium oxine radiolabeled parasites and was antibody independent. Macrophage death appeared to be due to the deleterious effect of lysed amebae rather than the contact-dependent effector mechanisms of E. histolytica. Adherence between activated macrophages and amebae was greater than that between other leukocytes and amebae (P less than 0.001). Microscopic observations, kinetic analysis of the killing of amebae by activated macrophages, and suspension of amebae with adherent activated macrophages in a 10% dextran solution indicated that contact by activated macrophages was necessary to initiate the killing of amebae. Catalase but not superoxide dismutase inhibited the amebicidal capacity of activated macrophages (P less than 0.001). However, activated macrophages from an individual with chronic granulomatous disease were able to kill amebae, but not as effectively as normal cells (P less than 0.01). In summary, activated MC-derived macrophages killed virulent E. histolytica trophozoites through a contact-dependent, antibody-independent mechanism involving oxidative-dependent and -independent processes.

I-A restricted activation by T cell lines of anti-tuberculosis activity in murine macrophages

Tuberculosis and leprosy remain two of the world's most significant diseases. Immunity involves the activation of macrophages by lymphokines but the details are unknown because there has been no objective assay for the relevant effector function using human pathogens. We previously reported the use of tritiated-uracil uptake by surviving mycobacteria as a measure of the anti-mycobacterial effect of human monocytes. We describe here the use of a modification of this assay to measure control of the proliferation of Mycobacterium tuberculosis in murine peritoneal macrophages. A bacteriostatic effect can be induced in macrophages infected with M. tuberculosis, by adding small numbers of Ly 1 +2- T cells from in vitro lines derived from immunized mice. The phenomenon is dependent on compatibility at the I-A locus of the major histocompatibility complex (MHC) and mediated by soluble factors. Such T cells also recognise and activate macrophages infected with other mycobacterial pathogens. Thus, T cells recognising shared mycobacterial antigens are active. The findings have implications for MHC linked susceptibility to mycobacterioses and the hypothesized ability of cross-reactive environmental mycobacteria to abrogate or pre-empt the protective efficacy of subsequent BCG vaccination.

Mycobacterial antigen-specific human T-cell clones secreting macrophage activating factors

Macrophage activating factor (MAF) is produced by antigen-stimulated lymphocytes and activates macrophages for antimicrobial function. The capacity of individual microbial antigens to evoke and regulate this response has been explored using an affinity purified antigen (TB68) of Mycobacterium tuberculosis in combination with T-cell cloning. Four helper/inducer clones are described which responded strongly to this antigen. Three were specific, proliferating only to TB68 antigen and antigenic preparations containing this antigen. However, one of these clones (68.1) did not proliferate to BCG and PPD which contained the TB68 antigen. In addition, another clone, 68.13, also proliferated to other antigenic preparations which did not contain the TB68 antigen. Taken together, these data indicate the presence of several epitopes in the affinity-purified TB68 antigen. All the clones produced MAF, which enhanced H2O2 production in U937 cell lines and conventional macrophages matured from monocytes. Thus, T-cell clones proliferating to a mycobacterial antigen constitutively secrete lymphokines that activate macrophages to antimicrobial immunity.