IL-12 and IL-27 regulate the phagolysosomal pathway in mycobacteria-infected human macrophages
© Jung and Robinson; licensee BioMed Central Ltd. 2014
Received: 30 January 2014
Accepted: 7 March 2014
Published: 11 March 2014
The cytokine environment at the site of infection is important to the control of mycobacteria by host macrophages. During chronic infection immunosuppressive cytokines are likely to favor mycobacterial growth, persistence, and an avoidance of proper antigen processing and presentation. The activity of interleukin (IL)-27 toward macrophages is anti-inflammatory and this compromises control of mycobacteria. Modulation of the cytokine environment may enhance both protective and vaccine-induced responses.
In this study we showed that supplying IL-12 and neutralizing IL-27 enhanced acidification and fusion of mycobacterial-containing phagosomes with lysosomes. This was achieved by phagosomal acquisition of vacuolar ATPase (V-ATPase) and CD63. Both V-ATPase and CD63 protein levels were increased by the addition of IL-12 and neutralization of IL-27. In addition, cathepsin D associated with the bacteria and matured to the active form when IL-12 was supplied and IL-27 was neutralized. Lysosomal acidification and cathepsin D activity were associated with control of mycobacteria. The acidification of lysosomes, association with mycobacteria, and maturation of cathepsin D required macrophage production of IFN-γ and signaling through signal transducer and activator of transcription (STAT)-1. In contrast, STAT-3 signaling opposed these events.
Our results have identified novel influences of IL-12, IL-27, and STAT-3 on lysosomal activity and further demonstrate that modulating the cytokine environment promotes enhanced trafficking of mycobacteria to lysosomes in human macrophages. This has important implications in approaches to control infection and improve vaccination. Overcoming bacterial resistance to lysosomal fusion may expand the repertoire of antigens presented to the adaptive arm of the immune response.
KeywordsBCG V-ATPase CD63 Cathepsin D Phagolysosome Human macrophages
Mycobacterium tuberculosis (MTB) is an intracellular human pathogen responsible for an enormous burden of human disease. In 2011, there were approximately 8.7 million incident cases of tuberculosis (TB) globally and nearly a third of the world population has been infected . The only currently available vaccine for TB is Mycobacterium bovis bacille Calmette-Guerin (BCG). BCG effectively protects against disseminated tuberculosis, such as miliary TB and tuberculous meningitis in children [2, 3]. However, the BCG vaccine has not been consistently effective at preventing pulmonary tuberculosis, and thus the effects of BCG on combating the global burden of tuberculosis have been limited.
Several hypotheses have been proposed to explain the limitations of BCG vaccination. These include interference by environmental mycobacteria, genetic differences in the human population, and differences between BCG substrains . Recently, it has been proposed that mycobacterial antioxidants, such as iron-cofactored superoxide mutase , and secA2 secretion suppress host immunity , resulting in reduction of vaccine efficacy. Suppression of host immunity could be mediated by anti-inflammatory cytokines. BCG-infected mice express high levels of the Th2 cytokines interleukin (IL)-5 and IL-13 . Similarly, IL-4 and TGF-β are known to be increased in tuberculosis patients . Thus, another possible explanation for limited effectiveness of BCG may be inhibition of host immunity through the action of immune suppressive cytokines.
IL-27 is produced by antigen presenting cells in response to a variety of activation stimuli, notably microbial-derived products . IL-27 activates Janus kinases (JAK) and signal transducer and activator of transcription (STAT)-1 and STAT-3 through its receptor composed of WSX-1 and gp130 . IL-27 was originally described as a soluble factor that promotes Th1 activity . STAT-1 and STAT-3 modulate the T-cell specific transcription factors such as T-bet (Th1) or GATA-3 (Th2) . However, IL-27 also negatively regulates Th1 cells, highlighting its paradoxical nature . Similarly, IL-27 inhibits differentiation of Th17 cells and production of IL-17 by inducing IL-10 producing Tr-1 cells through STAT-1 and STAT-3 . Immunosuppressive activity of IL-27 has been described toward a number of immune cell types involved in innate immune responses . IL-27 induces an immunosuppressive phenotype in murine DCs by increasing expression of B7-H1 in a STAT-3-dependent manner [15, 16]. Proinflammatory cytokine production is inhibited in both human and murine macrophages by IL-27 [17, 18].
IL-27 produced by human macrophages during MTB infection opposes inflammatory responses [17, 19–21]. Treatment with IL-12 in conjunction with neutralization of IL-27 restricts the growth of MTB and requires the proinflammatory mediators IFN-γ, TNF-α, and IL-18 [17, 19]. This immunomodulation promotes more effective macrophage-mediated immunity. Even though immunological parameters involved with the treatment of IL-12 and sIL-27R that improve mycobacterial control have been revealed , the intracellular mechanisms involved have not been elucidated.
MTB arrest phagosomes at an early stage of endosomes by blocking phagosomal maturation . This prevents fusion with late endosomes and lysosomes. Beyond the implications in host-mediated control of mycobacteria, this limits antigen presenting cell processing of mycobacterial antigen. Mycobacterium bovis BCG also avoid phagosomal fusion with lysosomes as efficiently as MTB [23, 24]. In doing so, BCG may limit the range of antigens that are processed for presentation by major histocompatibility complex (MHC) class II. The phagosomal/lysosomal trafficking pathway involves a variety of host molecules including proteins and phospholipids. Phagosomal maturation occurs through the acquisition of several lysosomal markers, such as lysosome associated membrane protein LAMP-1, LAMP-2, and CD63. In the final stage of maturation, the phagosome acquires V-ATPase and cathepsins in a syntaxin6-dependent manner .
The proinflammatory cytokine IFN-γ promotes phagosomal maturation by inducing acidification of phagosomes . IFN-γ treatment in murine macrophages leads to acidification of mycobacterial-containing phagosomes . Additionally, IFN-γ treatment of monocyte-derived macrophages increased lysosomal fusion with endosomes . However, there is some evidence that anti-inflammatory cytokines can inhibit the phagosomal/lysosomal pathway [21, 23, 26]. MTB-infected macrophages from IL-10 knock-out mice exhibit an increased level of acidification . IL-10 decreased fusion of horse radish peroxidase (HRP) containing phagosomes with lysosomes . Recently we have demonstrated that IL-27 decreases phagosomal acidification through inhibition of V-ATPases .
Based on these reports, treatment of infected macrophages with IL-12 and sIL-27R could promote an environment that is unfavorable for mycobacterial growth by enhancing phagosomal maturation and fusion with lysosomes. The objective of this work was to evaluate the influence of IL-12 and IL-27 on the phagosomal/lysosomal pathway during infection by BCG. Promoting enhanced delivery of BCG to lysosomes may enhance the magnitude and diversity of antigen presentation. Treatment of IL-12 combined with neutralization of IL-27 increased the expression of CD63 and V-ATPase. The consequence was enhanced phagosomal acidification and localization of cathepsinD at the BCG-containing phagosome. This immunomodulatory approach that overcomes phagolysosomal resistance may not only be important for controlling bacterial growth but also increasing the repertoire of BCG antigens that are presented during vaccination and improve the efficacy of BCG.
BCG infection of human macrophages increases the production of IL-27
Supplying IL-12 and neutralizing IL-27 induced lysosomal acidification
Supplying IL-12 and neutralizing IL-27 induced the expression of CD63 and enhanced association with BCG
Supplying IL-12 and neutralizing IL-27 induced the expression of vacuolar ATPases
Supplying IL-12 and neutralizing IL-27 induced the formation of mature cathepsin D and enhanced association with BCG
Enhanced fusion of mycobacterial phagosomes with lysosomes restricts BCG growth
IFN-γ is important for the enhancement of phagosomal acidification when IL-12 is supplied and IL-27 is neutralized
STAT-1 is an important regulator of lysosomal changes mediated by supplying IL-12 and neutralizing IL-27
Effective innate immunity involves the activation of macrophages. Activated macrophages utilize a variety of molecules and intracellular pathways to combat microbial pathogens. Among these is the maturation of phagosomes to lysosomes that is accompanied by a decrease in pH. Mycobacteria evolved to avoid this pathway by excluding the effector proteins involved in phagosomal acidification and lysosomal fusion (CD63, V-ATPase, and cathepsin D) from their vacuoles . BCG has been safely used for nearly a century, but the protective efficacy against TB is highly variable . BCG is highly similar to MTB in antigenic composition [39, 40] and equally efficient at avoiding phagosomal maturation and lysosomal fusion [23, 24]. Consequently, only a limited repertoire of BCG antigens may be presented in the initiation of an adaptive response. This may contribute to the limited vaccine efficacy against tuberculosis. Although delayed clearance of BCG may promote immunity by providing continual antigenic stimulation, expanding the nature of the response through enhanced processing and presentation may be a more effective strategy for host protection. It is clear that a strong immune response is initiated during tuberculosis. However, the nature of the response may be equally as important as the magnitude of response. Our data provide new information to be considered on this front.
The cytokine environment at the site of infection is likely to influence the phagosomal/lysosomal pathway. IFN-γ promotes lysosomal fusion with endosomes and acidification . Via et al. showed that IFN-γ treatment increases the acidification of BCG-containing phagosomes in murine macrophages . In this report, bone marrow-derived BCG-infected macrophages from IL-10 deficient mice exhibited increased acidification of BCG phagosomes suggesting that IL-10 has negative influences on the phagosomal/lysosomal pathway . Recently, we have demonstrated that exogenous treatment of IL-27 decreases phagosomal acidification by inhibiting the protein expression of V-ATPases in latex bead-treated human macrophages . IL-27 is expressed by MTB [17, 20] and BCG-infected macrophages (Figure 1A). In addition, treatment with IL-12 and sIL-27R restricted growth of both species in human macrophages (Figure 1B, 17, 19, 20). This suggests that IL-27 may create a favorable intracellular environment for the bacteria. Alternatively, blocking IL-27 promotes host protection.
The major finding in this study is that altering the cytokine environment by supplying IL-12 and neutralizing IL-27 resolves the mycobacterial arrest of phagosome maturation. This involves several steps. V-ATPase reduces the pH to 5.0 in mycobacterial phagosomes (Figure 2 and 4) . Eventually BCG-containing phagosomes become phagolysosomes by acquiring CD63 (Figure 3), most likely through fusion with established acidic lysosomes or acquisition from other vesicles through the golgi or ER. Along with the phagosomal acidification, cathepsin D was processed to the mature form (Figure 5) indicating that this enzyme may be actively involved in mycobacterial degradation in an acidic milieu of phagolysosomes. Mature cathepsin D was associated with BCG phagosomes when macrophages were treated with IL-12 and sIL-27R. Cathepsin D may be recruited to phagosomes as a preform and subsequent acidification through acquisition of V-ATPase leads to generation of mature cathepsin D. Enhanced phagosomal acidification and cathepsin D activity during treatment with IL-12 and neutralization of IL-27 was important for limiting intracellular bacterial growth (Figure 6). Inhibition of V-ATPase by bafilomycin and cathepsin D by pepstatin reversed the inhibition of bacterial growth to the level of untreated macrophages (Figure 6C). This data indicates that supplying IL-12 and neutralizing IL-27 specifically influences the phagosomal/lysosomal pathway. IFN-γ was shown to be an important immunological mediator. Neutralizing IFN-γ reversed the enhancement of phagosomal acidification and cathepsin D activity that were responsible for control of mycobacterial growth (Figure 7). This was consistent with reduced V-ATPase and CD63 expression levels along with prevention of cathepsin D maturation (Figure 7). IFN-γ is known to enhance phagosomal acidification and lysosomal fusion . IFN-γ treatment enhanced the fusion of MTB-containing phagosomes with lysosomes in THP-1 cells, and these lysosomes originated from autophagy-stimulated autophagosomes . Since IFN-γ plays a major role in mediating phagosomal acidification during treatment with IL-12 and sIL-27R, an autophagic mechanism may be involved. This is currently under investigation. IFN-γ activates STAT-1 activity to induce anti-microbial mechanisms in macrophages . We found that STAT-1 inhibition reverses lysosomal acidification and association with BCG during treatment with IL-12 and sIL-27R (Figure 8). It is important to point out that although our experiments suggest that STAT-1 associated with IFN-γ signaling promotes lysosomal acidification and association with BCG, our approach using chemical inhibitors does not distinguish STAT-1 induced by signaling through the IFN-γ receptor from that through the IL-27 receptor. In contrast to the positive action of IFN-γ and STAT-1, IL-27 signals through STAT-3 to oppose lysosomal acidification and fusion with BCG. This was demonstrated by the observation that STAT-3 inhibition in the absence of additional influences on the cytokine environment allowed for lysosomal acidification and association with BCG.
Anti-inflammatory cytokines may strongly influence the intracellular fate of mycobacteria in human macrophages. Previous reports show that anti-inflammatory cytokines, IL-4 and TGF-β are increased in MTB-infected individuals . Another anti-inflammatory cytokine, IL-10 is also involved in preventing acidification of mycobacteria-containing phagosomes . Consistent with this observation, blocking IL-10 signaling following BCG vaccination enhanced protective Th1 and Th17 responses . Since IL-10 also signals through STAT-3, IL-27 and IL-10 may operate similarly to oppose lysosomal acidification and protective immunity. Thus, regulating the cytokine environment to establish an antibacterial state in macrophages will not only be beneficial during infection but may also enhance vaccine-induced responses.
Bacterial strains and growth conditions
Mycobacterium bovis Calmette Guérin (BCG) was purchased from ATCC (Manassas, VA). Bacteria were maintained in Middlebrook 7H9 broth supplemented with ADC enrichment media (Albumin, Dextrose, Catalase) at 37°C with 5% CO2.
Staining of Mycobacterium bovis BCG
BCG were pre-stained with SYTO-9® or SYTO-61® (100 μM, Molecular Probes, Life Technologies) according to the manufacturer’s instructions. Briefly, 5 × 106 CFUs were pelleted at 2,000 × g for 10 min at room temperature. The supernatant was discarded and the pellet was suspended in SYTO probes at a final volume of 1 mL and passed through a 27-guage needle to disperse the bacteria completely. Following 30 min incubation in the dark, the stained bacteria were centrifuged at 2000 × g for 10 min. The bacterial pellet was suspended in 1 ml of infection medium (DMEM supplemented with 1% human serum, 2 mM glutamine, 25 mM HEPES) and passed through a 27-gauge needle several times. Stained BCG were diluted to a MOI of 10 with infection medium.
Human buffy coats were purchased from the New York Blood Center (New York, NY). Eligible donors were 16 years of age or older, at least 110 pounds, and in good physical health. The donor samples were anonymous and deidentifed. Peripheral blood mononuclear cells (PBMCs) were isolated from buffy coats by Ficoll gradient centrifugation. Monocytes were then isolated from PBMCs by Optiprep (Sigma-Aldrich) gradient centrifugation as described previously . Monocytes were adhered to plastic 60 mm culture dishes in serum-free DMEM. The media was then replaced with DMEM supplemented with 2 mM glutamine, 25 mM HEPES, 20% fetal bovine serum (FBS), and 10% human serum and incubated at 37°C with 5% CO2 for 7 days. Macrophages were removed from the culture dish with PBS that contained 5 mM EDTA and 4 mg/ml lidocaine. The cells were washed with PBS and plated onto new culture dishes in DMEM supplemented with infection medium. These cells are routinely >95% CD14 positive.
Macrophage infection and enumeration of BCG
Human macrophages were cultivated in 24-well plates (2 × 105/well) and treated with medium alone, IL-12 (5 ng/ml), sIL-27R (10 μg/ml), or their combination for 6 h prior to infection with SYTO-stained BCG (~MOI 10). Infected cultures were incubated 48 h at 37°C with 5% CO2. Culture supernatants were removed and macrophages were permeabilized with 1% saponin to release bacteria. Tenfold serial dilutions were plated on Middlebrook 7H10 agar and incubated 10 days at 37°C with 5% CO2.
Analysis of lysosomal acidification and immunolabeling
Human macrophages cultured in 24-well plates were treated as indicated above. In the last hour of infection, culture supernatants were replaced with medium that contained Lysotracker DND-99 Red (Life technologies) (100 nM). The slides were examined using a Zeiss Meta 510 laser confocal microscope with a plan-Apochromat 63× objective lens. A total of 10 fields containing 5–10 macrophages per field were examined in each experiment. The mean fluorescent intensity (MFI) for each macrophage was calculated using Image J software. Each cell from the image was selected and histogram analysis was performed. For immunostaining, mouse monoclonal antibodies for CD63 (sc-5275, Santa Cruz Biotechnology) and V1-ATPase H (sc-166227, santa Cruz Biotechnology) were visualized with anti-mouse-Alexafluor 588-conjugated secondary antibody. Goat polycolonal antibodies for active cathepsin D (sc-6486, Santa cruz) were visualized with anti-goat-Alexafluor 488-conjugated secondary antibody (Life technologies).
Quantitative bacterial association analysis
To quantify bacterial association with lysosomes, CD63, V-ATPase, or cathepsin D, we employed Pearson’s correlation coefficient analyses. The analyses were performed as follows. During imaging, the microscope pinhole size was set to acquire the same amount of signal for each channel. To minimize the bleed-through effect, the image was scanned sequentially. To avoid saturation, a range indicator for identification of excessive bright and excessive high contrast images was established. This allowed for adjustment using an offset function. Each image was analyzed by image J software. This software produces a number of coefficients for estimating the degree of association. Pearson’s correlation was employed to analyze association between green (BCG) and red (Lysotracker, CD63, V-ATPase) or red (BCG) and green (cathepsin D)) since this analysis considers similarity between shapes .
Quantitative real time PCR
Human macrophages (2×105/well) cultivated in 24-well dishes were treated as indicated. At appropriate time points, media was removed from cultures, the cells were lysed with PureZol® (Bio-Rad), and RNA was isolated according to commercial product protocol. First strand cDNA synthesis was performed using iScript™ cDNA synthesis reagents (Bio-Rad) according to protocol. For IL-27 p28 and EBI3 gene expression analysis, real time cycling of reactions that included cDNA diluted 20-fold from above, gene-specific primer probe sets (Applied Biosystems), iQ™ Supermix (Bio-Rad) was performed in triplicate using iQ5™ cycler (Bio-Rad). GAPDH was used as an internal reference gene.
Human macrophages (2 × 105 cells/well) cultivated in 24-well plates were left untreated or treated with the combination of IL-12 (5 ng/ml) and sIL-27R (10 μg/ml) for 6 h prior to infection with BCG (~MOI 10). Infected cultures were incubated for 48 h at 37°C with 5% CO2. Briefly, after infection with BCG, 40 μl of PBS supplemented with 1% Tx-100 was applied to each sample and lysates collected by scraping. They were subsequently sonicated and then stored at 4°C. Equal amounts of cell lysates were separated on SDS-PAGE gels and transferred to nitrocellulose by standard technique. Primary antibodies used in this study were mouse monoclonal anti-CD63, V-ATPase H, Cathepsin D antibodies that recognize all forms (sc-374381, Santa Cruz Biotechnology), and rabbit polyclonal anti-actin (Sigma) antibodies. Primary antibodies were revealed with horse radish peroxidase-conjugated anti-mouse or anti-rabbit secondary antibodies. ECL substrate (Amersham Biosciences) was applied to visualize proteins.
Bafilomycin and pepstatin titration
Bafilomycin and pepstatin were purchased from Sigma. Bafilomycin titration was performed as follows. Macrophages were treated with varying concentrations of bafilomycin (0–1000 nM) for 6 h and then treated with fluorescent-conjugated latex beads for an additional 48 h. The macrophages were examined by confocal microscopy as described earlier in this section. Pepstatin titration was performed as follows. Macrophages were either untreated or treated with varying concentrations (0–100 μM) of pepstatin for 6 h, and then subsequently infected with BCG (MOI 10) for 48 h. Auramine O staining was performed as described previously  and fluorescence (λex = 420 and λem = 508 nm) was measured with a Synergy HT Multi-Mode Microplate reader (Biotek, VT).
This work was supported by NIH grant HL093300.
- Global tuberculosis report 2012. [http://www.who.int/tb/publications/global_report/en/]
- Rook GAW, Dheda K, Zumla A: Immune responses to tuberculosis in developing countries: implications for new vaccines. Nat Rev Immunol. 2005, 5: 661-667. 10.1038/nri1666.PubMedView ArticleGoogle Scholar
- Hart PD, Sutherland I: BCG and vole bacillus vaccines in the prevention of tuberculosis in adolescence and early adult life: final report to the Medical Research Council. BMJ. 1977, 2: 293-295. 10.1136/bmj.2.6082.293.PubMedPubMed CentralView ArticleGoogle Scholar
- Fine PEM, Carneiro IAM, Milstien JB, Clements JD: Issues relating to the Use of BCG in Immunization Programs: a Discussion Document. Document WHO/V&B/99.23. 1999, Geneva, Switzerland: World Health Organization Department of Vaccines and BiologicalsGoogle Scholar
- Edwards KM, Cynamon MH, Voladri RK, Hager CC, Destefano MS, Tham KT, Lakey DL, Bochan MR, Kernodle DS: Iron-cofactored superoxide dismutase inhibits host response to Mycobacterium tuberculosis. Am J Respir Crit Care Med. 2001, 164: 2213-2219. 10.1164/ajrccm.164.12.2106093.PubMedView ArticleGoogle Scholar
- Kurtz S, McKinnon KP, Runge MS, Ting JP, Braunstein M: The SecA2 secretion factor of Mycobacterium tuberculosis promotes growth in macrophages and inhibits host immune response. Infect Immun. 2006, 74: 6855-6864. 10.1128/IAI.01022-06.PubMedPubMed CentralView ArticleGoogle Scholar
- Biet F, Kremer L, Wolowczuk I, Declacre M, Locht C: Mycobacterium bovis BCG producing interleukin-18 increases antigen-specific gamma interferon production in mice. Infect Immun. 2002, 70: 6549-6557. 10.1128/IAI.70.12.6549-6557.2002.PubMedPubMed CentralView ArticleGoogle Scholar
- Rook GAW, Lowrie DB, Hernandez-Pando R: Immunotherapeutics for tuberculosis in experimental animals: is there a common pathway activated by effective protocols?. J Infect Dis. 2007, 196: 191-198. 10.1086/518937.PubMedView ArticleGoogle Scholar
- Beadling C, Slifka MK: Regulation of innate and adaptive immune responses by the related cytokines IL-12, IL-23, and IL-27. Arch Immunol Ther Exp. 2006, 54: 15-24. 10.1007/s00005-006-0002-6.View ArticleGoogle Scholar
- Yoshida H, Nakaya M, Miyazaki Y: Interleukin 27: a double-edged sword for offense and defense. J Leukoc Biol. 2009, 86: 1295-1303. 10.1189/jlb.0609445.PubMedView ArticleGoogle Scholar
- Pflanz S, Timans JC, Cheung J, Rosales R, Kanzler H, Gilbert J, Hibbert L, Churakova T, Travis M, Vaisberg E, Blumenschein WM, Mattson JD, Wagner JL, To W, Zurawski S, McClanahan TK, Gorman DM, Bazan JF, de Waal Malefyt R, Rennick D, Kastelein RA: IL-27, a heterodimeric cytokine composed of EBI3 and P28 protein, induces proliferation of naïve CD4+ T cells. Immun. 2002, 16: 779-790. 10.1016/S1074-7613(02)00324-2.View ArticleGoogle Scholar
- Rauch I, Műller M, Decker T: The regulation of inflammation by interferons and their STATs. JAK-STAT. 2013, 2: e23820-10.4161/jkst.23820.PubMedPubMed CentralView ArticleGoogle Scholar
- Stumhofer JS, Hunter CA: Advances in understanding the anti-inflammatory properties of IL-27. Immunol Lett. 2008, 117: 123-130. 10.1016/j.imlet.2008.01.011.PubMedPubMed CentralView ArticleGoogle Scholar
- Pot C, Apetoch L, Awasthi A, Kuchroo VK: Induction of regulatory Tr1 cells and inhibition of TH 17cells by IL-27. Semin Immunol. 2011, 23: 438-445. 10.1016/j.smim.2011.08.003.PubMedPubMed CentralView ArticleGoogle Scholar
- Karakhanova S, Bedke T, Enk AH, Mahneke K: IL-27 renders DC immunosuppressive by induction of B7-H1. J Leukoc Biol. 2011, 89: 837-845. 10.1189/jlb.1209788.PubMedView ArticleGoogle Scholar
- Matta BM, Raimondi G, Rosborough BR, Sumpter TL, Thomson AW: IL-27 production and STAT-3 dependent upregulation of B7-H1 mediate immune regulatory functions of liver plasmacytoid dendritic cells. J Immunol. 2012, 188: 5227-5237. 10.4049/jimmunol.1103382.PubMedPubMed CentralView ArticleGoogle Scholar
- Robinson CM, Nau GJ: Interleukin-12 and interleukin-27 regulate macrophage control of Mycobacterium tuberculosis. J Infect Dis. 2008, 198: 359-366. 10.1086/589774.PubMedPubMed CentralView ArticleGoogle Scholar
- Holscher C, HÖlscher A, Rückerl D, Yoshimoto T, Yoshida H, Mak T, Saris C, Ehlers S: The IL-27 receptor chain WSX-1 differentially regulates antibacterial immunity and survival during experimental tuberculosis. J Immunol. 2005, 174: 3534-3544.PubMedView ArticleGoogle Scholar
- Robinson CM, Jung JY, Nau GJ: Interferon-γ, tumornecrosis factor, and interleukin-18 cooperate to control growth of Mycobacterium tuberculosis in human macrophages. Cytokine. 2012, 60: 233-241. 10.1016/j.cyto.2012.06.012.PubMedPubMed CentralView ArticleGoogle Scholar
- Robinson CM, O’Dee D, Hamilton T, Nau GJ: Cytokines involved in interferon-γ production by human macrophages. J Innate Immun. 2010, 2: 56-65. 10.1159/000247156.PubMedView ArticleGoogle Scholar
- Jung JY, Robinson CM: Interleukin-27 inhibits phagosomal acidification by blocking vacuolar ATPases. Cytokine. 2013, 62: 202-205. 10.1016/j.cyto.2013.03.010.PubMedPubMed CentralView ArticleGoogle Scholar
- Vergne I, Chua J, Singh SB, Deretic V: Cell biology of Mycobacterium tuberculosis phagosome. Annu Rev Cell Dev Biol. 2004, 20: 367-394. 10.1146/annurev.cellbio.20.010403.114015.PubMedView ArticleGoogle Scholar
- Via LE, Fratti RA, McFalone M, Pagan-Ramos E, Deretic D, Deretic V: Effects of cytokines on mycobacterial phagosome maturation. J Cell Sci. 1998, 111: 897-905.PubMedGoogle Scholar
- Fratti RA, Chua J, Deretic V: Induction of p38 mitogen-activated protein kinase reduces early endosome autoantigen 1 (EEA1) recruitment to phagosomal membranes. J Biol Chem. 2003, 278: 46961-46967. 10.1074/jbc.M305225200.PubMedView ArticleGoogle Scholar
- Fratti RA, Chua J, Vergne I, Deretic V: Mycobacterium tuberculosis glycosylated phosphatidylinositol causes phagosome maturation arrest. Proc Natl Acad Sci USA. 2003, 100: 5437-5442. 10.1073/pnas.0737613100.PubMedPubMed CentralView ArticleGoogle Scholar
- Montaner LJ, da Silva RP, Sun J, Sutterwala S, Hollinshead M, Vaux D, Gordon S: Type1 and type2 cytokine regulation of macrophage endocytosis: differential activation by IL-4/IL-13 as opposed to IFN-γ or IL-10. J Immunol. 1999, 162: 4606-4613.PubMedGoogle Scholar
- Clemens DL, Horwitz MA: Characterization of the Mycobacterium tuberculosis phagosome and evidence that phagosomal maturation is inhibited. J Exp Med. 1995, 181: 257-270. 10.1084/jem.181.1.257.PubMedView ArticleGoogle Scholar
- Forgac M: Vacuolar ATPases: rotary proton pumps in physiology and pathophysiology. Nat Rev Mol Cell Biol. 2007, 8: 917-929. 10.1038/nrm2272.PubMedView ArticleGoogle Scholar
- Benes P, Vetvicka V, Fusek M: Cathepsin D-Many functions of one aspartic protease. Crit Rev Oncol Hematol. 2008, 68: 12-28. 10.1016/j.critrevonc.2008.02.008.PubMedPubMed CentralView ArticleGoogle Scholar
- Sturgill-Koszycki S, Schlesinger PH, Chakraborty P, Haddix PL, Collins HL, Fok AK, Allen RD, Gluck SL, Heuser J, Russell DG: Lack of acidification in Mycobacterium phagosomes produced by exclusion of the vesicular proton-ATPase. Science. 1994, 263: 678-681. 10.1126/science.8303277.PubMedView ArticleGoogle Scholar
- Wong D, Bach H, Sun J, Hmama Z, Av-Gay Y: Mycobacterium tuberculosis protein tyrosine phosphatase (PtpA) excludes host vacuolar-H+-ATPase to inhibit phagosome acidification. Proc Natl Acad Sci USA. 2011, 108: 19371-19376. 10.1073/pnas.1109201108.PubMedPubMed CentralView ArticleGoogle Scholar
- Nakagawa TY, Rudensky AY: The role of lysosomal proteinases in MHC class II-mediated antigen processing and presentation. Immunol Rev. 1999, 172: 121-129. 10.1111/j.1600-065X.1999.tb01361.x.PubMedView ArticleGoogle Scholar
- Sturgill-Koszycki S, Schaible UE, Russell DG: Mycobacterium-containing phagosomes are accessible to early endosomes and reflect a transitional state in normal phagosome biogenesis. EMBO J. 1996, 15: 6960-6968.PubMedPubMed CentralGoogle Scholar
- Werner G, Hagenmaier H, Drautz H, Baumgatner A, Zähner H: Metabolic products of microorganisms.224. Bafilomycins, a new group of macrolide antibiotics. Production, isolation, chemical structure and biological activity. J Antibiot. 1984, 37: 110-117. 10.7164/antibiotics.37.110.PubMedView ArticleGoogle Scholar
- Bowman EJ, Siebers A, Altendorf K: Bafilomycins: a class of inhibitors of membrane ATPases from microorganisms, animal cells, and plant cells. Proc Natl Acad Sci USA. 1988, 85: 7972-7976. 10.1073/pnas.85.21.7972.PubMedPubMed CentralView ArticleGoogle Scholar
- Rich DH, Bernatowicz MS, Agarwal NS, Kawai M, Salituro FG, Schmidt PG: Inhibition of aspartic proteases by pepstatin and 3-methylstatine derivatives of pepstatin. Evidence for collected-substrate enzyme inhibition. Biochemistry. 1985, 24: 3165-3173. 10.1021/bi00334a014.PubMedView ArticleGoogle Scholar
- Frank DA, Mahaian S, Ritz J: Fludarabine-induced immunosuppression is associated with inhibition of STAT-1 signaling. Nat Med. 1999, 5: 444-447. 10.1038/7445.PubMedView ArticleGoogle Scholar
- Li R, You S, Hu Z, Chen ZG, Sica GL, Khuri FR, Curran WJ, Shin DM, Deng X: Inhibition of STAT3 by niclosamide synergizes with erlotinib against head and neck cancer. PLoS One. 2013, 8: e74670-10.1371/journal.pone.0074670.PubMedPubMed CentralView ArticleGoogle Scholar
- Content J, de la Cuvellerie A, De Wit L, Vincent-Levy-Frebault V, Ooms J, De Bruyn J: The genes coding for the antigen 85 complexes of Mycobacterium tuberculosis and Mycobacterium bovis BCG are members of a gene family: cloning, sequence determination, and genomic organization of the gene coding for antigen 85-C of M. tuberculosis. Infect Immun. 1991, 59: 3205-3212.PubMedPubMed CentralGoogle Scholar
- Harth G, Lee BY, Wang J, Clemens DL, Horwitz MA: Novel insights into the genetics, biochemistry, and immunocytochemistry of the 30-kilodalton major extracellular protein of Mycobacterium tuberculosis. Infect Immun. 1996, 64: 3038-3047.PubMedPubMed CentralGoogle Scholar
- Mindell JA: Lysosomal acidification mechanisms. Annu Rev Physiol. 2012, 74: 69-86. 10.1146/annurev-physiol-012110-142317.PubMedView ArticleGoogle Scholar
- Dutta RK, Kathania M, Raje M, Majumdar S: IL-6 inhibits IFN-γ induced autophagy in Mycobacterium tuberculosis H37Rv infected macrophages. Int J Biochem Cell Biol. 2012, 44: 942-954. 10.1016/j.biocel.2012.02.021.PubMedView ArticleGoogle Scholar
- Pitt JM, Stavropoulos E, Redford PS, Beebe AM, Bancroft GJ, Young DB, O’garra A: Blockade of IL-10 signaling during bacillus Calmette-Guérin vaccination enhances and sustains Th1, Th17, and innate lymphoid IFN-γ and IL-17 responses and increases protection to Mycobacterium tuberculosis infection. J Immunol. 2012, 189: 4079-4087. 10.4049/jimmunol.1201061.PubMedPubMed CentralView ArticleGoogle Scholar
- Carlson PE, Carroll JA, O’Dee DM, Nau GJ: Modulation of virulence factors in Francisella tularensis determines human macrophage responses. Microb Pathog. 2007, 42: 204-214. 10.1016/j.micpath.2007.02.001.PubMedPubMed CentralView ArticleGoogle Scholar
- Zinchk V, Zinchuk O, Okada T: Quantitative colocalization analysis of multicolor confocal immunofluorescence microscopy images: pushing pixels to explore biological phenomena. Acta Histochemica Et Cytochemica. 2007, 40: 101-111. 10.1267/ahc.07002.View ArticleGoogle Scholar
- Jung JY, Madan-Lala R, Georgieva M, Rengarajan J, Sohaskey CD, Bange F-C, Robinson CM: The intracellular environment of human macrophages that produce nitric oxide promotes growth of mycobacteria. Infect Immun. 2013, 81: 3198-3209. 10.1128/IAI.00611-13.PubMedPubMed CentralView ArticleGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly credited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.