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Roux AL, Viljoen A, Bah A, Simeone R, Bernut A, Laencina L, Deramaudt T, Rottman M, Gaillard JL, Majlessi L, Brosch R, Girard-Misguich F, Vergne I, de Chastellier C, Kremer L, Herrmann JL. The distinct fate of smooth and rough Mycobacterium abscessus variants inside macrophages. Open Biol 2017; 6:rsob.160185. [PMID: 27906132 PMCID: PMC5133439 DOI: 10.1098/rsob.160185] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2016] [Accepted: 10/31/2016] [Indexed: 02/07/2023] Open
Abstract
Mycobacterium abscessus is a pathogenic, rapidly growing mycobacterium responsible for pulmonary and cutaneous infections in immunocompetent patients and in patients with Mendelian disorders, such as cystic fibrosis (CF). Mycobacterium abscessus is known to transition from a smooth (S) morphotype with cell surface-associated glycopeptidolipids (GPL) to a rough (R) morphotype lacking GPL. Herein, we show that M. abscessus S and R variants are able to grow inside macrophages and are present in morphologically distinct phagosomes. The S forms are found mostly as single bacteria within phagosomes characterized by a tightly apposed phagosomal membrane and the presence of an electron translucent zone (ETZ) surrounding the bacilli. By contrast, infection with the R form leads to phagosomes often containing more than two bacilli, surrounded by a loose phagosomal membrane and lacking the ETZ. In contrast to the R variant, the S variant is capable of restricting intraphagosomal acidification and induces less apoptosis and autophagy. Importantly, the membrane of phagosomes enclosing the S forms showed signs of alteration, such as breaks or partial degradation. Although not frequently encountered, these events suggest that the S form is capable of provoking phagosome-cytosol communication. In conclusion, M. abscessus S exhibits traits inside macrophages that are reminiscent of slow-growing mycobacterial species.
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Affiliation(s)
- Anne-Laure Roux
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Albertus Viljoen
- Centre National de la Recherche Scientifique FRE 3689, Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé, Université de Montpellier, 1919, Route de Mende, 34293, Montpellier, France.,Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université UM 2, Inserm, U1104, CNRS UMR7280, 13288, Marseille, France
| | - Aïcha Bah
- CNRS, Institut de Pharmacologie et de Biologie Structurale (IPBS), UMR 5089 CNRS/Université Paul Sabatier, 205 route de Narbonne, BP 64182, 31077 Toulouse Cedex 4, France
| | - Roxane Simeone
- Unité de Pathogénomique mycobactérienne, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, Paris, France
| | - Audrey Bernut
- Centre National de la Recherche Scientifique FRE 3689, Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé, Université de Montpellier, 1919, Route de Mende, 34293, Montpellier, France
| | - Laura Laencina
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Therese Deramaudt
- UMR1179, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Martin Rottman
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Jean-Louis Gaillard
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Laleh Majlessi
- Unité de Pathogénomique mycobactérienne, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, Paris, France
| | - Roland Brosch
- Unité de Pathogénomique mycobactérienne, Institut Pasteur, 25 rue du Dr Roux, 75724 Paris Cedex 15, Paris, France
| | - Fabienne Girard-Misguich
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
| | - Isabelle Vergne
- CNRS, Institut de Pharmacologie et de Biologie Structurale (IPBS), UMR 5089 CNRS/Université Paul Sabatier, 205 route de Narbonne, BP 64182, 31077 Toulouse Cedex 4, France
| | - Chantal de Chastellier
- Centre d'Immunologie de Marseille-Luminy, Aix-Marseille Université UM 2, Inserm, U1104, CNRS UMR7280, 13288, Marseille, France
| | - Laurent Kremer
- Centre National de la Recherche Scientifique FRE 3689, Centre d'études d'agents Pathogènes et Biotechnologies pour la Santé, Université de Montpellier, 1919, Route de Mende, 34293, Montpellier, France .,INSERM, CPBS, 34293 Montpellier, France
| | - Jean-Louis Herrmann
- UMR1173, Inserm and UFR Des Sciences de la Santé Simone Veil, Université de Versailles Saint Quentin, Montigny, France
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Lemmer Y, Kalombo L, Pietersen RD, Jones AT, Semete-Makokotlela B, Van Wyngaardt S, Ramalapa B, Stoltz AC, Baker B, Verschoor JA, Swai HS, de Chastellier C. Mycolic acids, a promising mycobacterial ligand for targeting of nanoencapsulated drugs in tuberculosis. J Control Release 2015; 211:94-104. [PMID: 26055640 DOI: 10.1016/j.jconrel.2015.06.005] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2015] [Revised: 06/02/2015] [Accepted: 06/04/2015] [Indexed: 12/23/2022]
Abstract
The appearance of drug-resistant strains of Mycobacterium tuberculosis (Mtb) poses a great challenge to the development of novel treatment programmes to combat tuberculosis. Since innovative nanotechnologies might alleviate the limitations of current therapies, we have designed a new nanoformulation for use as an anti-TB drug delivery system. It consists of incorporating mycobacterial cell wall mycolic acids (MA) as targeting ligands into a drug-encapsulating Poly dl-lactic-co-glycolic acid polymer (PLGA), via a double emulsion solvent evaporation technique. Bone marrow-derived mouse macrophages, either uninfected or infected with different mycobacterial strains (Mycobacterium avium, Mycobacterium bovis BCG or Mtb), were exposed to encapsulated isoniazid-PLGA nanoparticles (NPs) using MA as a targeting ligand. The fate of the NPs was monitored by electron microscopy. Our study showed that i) the inclusion of MA in the nanoformulations resulted in their expression on the outer surface and a significant increase in phagocytic uptake of the NPs; ii) nanoparticle-containing phagosomes were rapidly processed into phagolysosomes, whether MA had been included or not; and iii) nanoparticle-containing phagolysosomes did not fuse with non-matured mycobacterium-containing phagosomes, but fusion events with mycobacterium-containing phagolysosomes were clearly observed.
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Affiliation(s)
- Yolandy Lemmer
- Polymers and Composites, Council for Scientific and Industrial Research, Pretoria, South Africa.
| | - Lonji Kalombo
- Polymers and Composites, Council for Scientific and Industrial Research, Pretoria, South Africa
| | - Ray-Dean Pietersen
- DST-CBTBR Department Molecular Biology and Human Genetics, Stellenbosch University, Cape Town, South Africa
| | - Arwyn T Jones
- Cardiff School of Pharmacy and Pharmaceutical Sciences, Cardiff University, Wales, UK
| | | | | | - Bathabile Ramalapa
- Polymers and Composites, Council for Scientific and Industrial Research, Pretoria, South Africa
| | - Anton C Stoltz
- Department of Infectious Diseases, University of Pretoria, Pretoria, South Africa
| | - Bienyameen Baker
- DST-CBTBR Department Molecular Biology and Human Genetics, Stellenbosch University, Cape Town, South Africa
| | - Jan A Verschoor
- Department of Biochemistry, University of Pretoria, Pretoria, South Africa
| | - Hulda S Swai
- Polymers and Composites, Council for Scientific and Industrial Research, Pretoria, South Africa
| | - Chantal de Chastellier
- Centre d'Immunologie de Marseille-Luminy (CIML), Aix Marseille University, UM 2, INSERM UMR 1104, CNRS UMR 7280, 163 avenue de Luminy, 13288 Marseille Cedex 09, France
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Reversible lipid accumulation and associated division arrest of Mycobacterium avium in lipoprotein-induced foamy macrophages may resemble key events during latency and reactivation of tuberculosis. Infect Immun 2013; 82:476-90. [PMID: 24478064 DOI: 10.1128/iai.01196-13] [Citation(s) in RCA: 80] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
During the dormant phase of tuberculosis, Mycobacterium tuberculosis persists in lung granulomas by residing in foamy macrophages (FM) that contain abundant lipid bodies (LB) in their cytoplasm, allowing bacilli to accumulate lipids as intracytoplasmic lipid inclusions (ILI). An experimental model of FM is presented where bone marrow-derived mouse macrophages are infected with M. avium and exposed to very-low-density lipoprotein (VLDL) as a lipid source. Quantitative analysis of detailed electron microscope observations showed the following results. (i) Macrophages became foamy, and mycobacteria formed ILI, for which host triacylglycerides, rather than cholesterol, was essential. (ii) Lipid transfer occurred via mycobacterium-induced fusion between LB and phagosomes. (iii) Mycobacteria showed a thinned cell wall and became elongated but did not divide. (iv) Upon removal of VLDL, LB and ILI declined within hours, and simultaneous resumption of mycobacterial division restored the number of mycobacteria to the same level as that found in untreated control macrophages. This showed that the presence of ILI resulted in a reversible block of division without causing a change in the mycobacterial replication rate. Fluctuation between ILI either partially or fully extending throughout the mycobacterial cytoplasm was suggestive of bacterial cell cycle events. We propose that VLDL-driven FM constitute a well-defined cellular system in which to study changed metabolic states of intracellular mycobacteria that may relate to persistence and reactivation of tuberculosis.
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Podinovskaia M, Lee W, Caldwell S, Russell DG. Infection of macrophages with Mycobacterium tuberculosis induces global modifications to phagosomal function. Cell Microbiol 2013; 15:843-59. [PMID: 23253353 DOI: 10.1111/cmi.12092] [Citation(s) in RCA: 119] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2012] [Revised: 12/05/2012] [Accepted: 12/11/2012] [Indexed: 01/01/2023]
Abstract
The phagosome is a central mediator of both the homeostatic and microbicidal functions of a macrophage. Following phagocytosis, Mycobacterium tuberculosis (Mtb) is able to establish infection through arresting phagosome maturation and avoiding the consequences of delivery to the lysosome. The infection of a macrophage by Mtb leads to marked changes in the behaviour of both the macrophage and the surrounding tissue as the bacterium modulates its environment to promote its survival. In this study, we use functional physiological assays to probe the biology of the phagosomal network in Mtb-infected macrophages. The resulting data demonstrate that Mtb modifies phagosomal function in a TLR2/TLR4-dependent manner, and that most of these modifications are consistent with an increase in the activation status of the cell. Specifically, superoxide burst is enhanced and lipolytic activity is decreased upon infection. There are some species- or cell type-specific differences between human and murine macrophages in the rates of acidification and the degree of proteolysis. However, the most significant modification is the marked reduction in intra-phagosomal lipolysis because this correlates with the marked increase in the retention of host lipids in the infected macrophage, which provides a potential source of nutrients that can be accessed by Mtb.
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Affiliation(s)
- Maria Podinovskaia
- Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, NY 14853, USA
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Ignatov D, Kondratieva E, Azhikina T, Apt A. Mycobacterium avium-triggered diseases: pathogenomics. Cell Microbiol 2012; 14:808-18. [DOI: 10.1111/j.1462-5822.2012.01776.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Inside or outside the phagosome? The controversy of the intracellular localization of Mycobacterium tuberculosis. Tuberculosis (Edinb) 2011; 92:113-20. [PMID: 22033468 DOI: 10.1016/j.tube.2011.09.009] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2011] [Revised: 09/12/2011] [Accepted: 09/21/2011] [Indexed: 01/09/2023]
Abstract
The localization of Mycobacterium tuberculosis (Mtb) inside the macrophage has been a matter of debate in recent years. Upon inhalation, the bacterium is taken up into macrophage phagosomes, which are manipulated by the bacterium. Subsequent translocation of the bacilli into the cytosol has been observed by several groups, while others fail to observe this phenomenon. Here, we review the available literature in favour of and against this idea, and scrutinize the existing data on how human macrophages control Mtb infection, relating this to the robustness of the host cell. We conclude that both phagosomal maturation inhibition and escape from the phagosome are part of the greater infection strategy of Mtb. The balance between the host cell and the infecting bacterium is an important factor in determining the outcome of infection as well as whether phagosomal escape occurs and can be captured.
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de Chastellier C, Forquet F, Gordon A, Thilo L. Mycobacterium requires an all-around closely apposing phagosome membrane to maintain the maturation block and this apposition is re-established when it rescues itself from phagolysosomes. Cell Microbiol 2009; 11:1190-207. [DOI: 10.1111/j.1462-5822.2009.01324.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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de Chastellier C. The many niches and strategies used by pathogenic mycobacteria for survival within host macrophages. Immunobiology 2009; 214:526-42. [PMID: 19261352 DOI: 10.1016/j.imbio.2008.12.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2008] [Accepted: 12/08/2008] [Indexed: 11/16/2022]
Abstract
A major virulence factor of pathogenic mycobacteria is their ability to parasitize the host's scavenger cells and more particularly macrophages. The present overview discusses the known cellular and molecular mechanisms of intracellular survival of Mtb and other pathogenic mycobacteria within different intracellular niches, i.e. the macrophage in which they replicate and the granuloma in which they persist in a non-replicating state. After phagocytic uptake by macrophages, mycobacteria reside in phagosomes which they prevent from maturing and, as a result, from fusing with acidic and hydrolase-rich lysosomes. Two major points are highlighted: (i) the requirement for a close apposition between the phagosome membrane and the mycobacterial surface all around, and (ii) the ability for mycobacteria targeted to phagolysosomes to avoid degradation and to be rescued from this cytolytic environment to again reside in non-maturing phagosomes with a closely apposed membrane in which they can replicate. Concerning Mtb in granulomatous lesions, this review discusses the occurence of mycobacteria in lipid-rich foamy macrophages in which they persist in a non-replicating state. This overview highlights the major contribution of host cholesterol and/or fatty acids (triacylglycerol) in both prevention of phagosome maturation and persistence in granulomatous lesions.
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Affiliation(s)
- Chantal de Chastellier
- Aix-Marseille Université, Faculté des Sciences de Luminy, Centre d'Immunologie de Marseille-Luminy (CIML), Parc scientifique de Luminy, case 906, F-13288 Marseille Cédex 09, France.
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Milanés-Virelles MT, García-García I, Santos-Herrera Y, Valdés-Quintana M, Valenzuela-Silva CM, Jiménez-Madrigal G, Ramos-Gómez TI, Bello-Rivero I, Fernández-Olivera N, Sánchez-de la Osa RB, Rodríguez-Acosta C, González-Méndez L, Martínez-Sánchez G, López-Saura PA. Adjuvant interferon gamma in patients with pulmonary atypical Mycobacteriosis: a randomized, double-blind, placebo-controlled study. BMC Infect Dis 2008; 8:17. [PMID: 18267006 PMCID: PMC2275277 DOI: 10.1186/1471-2334-8-17] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Accepted: 02/11/2008] [Indexed: 01/15/2023] Open
Abstract
BACKGROUND High antibiotic resistance is described in atypical Mycobacteriosis, mainly by Mycobacterium avium complex (MAC). METHODS A randomized, double-blind, placebo-controlled clinical trial was carried out in two hospitals to evaluate the effect of interferon (IFN) gamma as immunoadjuvant to chemotherapy on patients with atypical mycobacteria lung disease. Patients received placebo or 1 x 106 IU recombinant human IFN gamma intramuscularly, daily for one month and then three times per week up to 6 months as adjuvant to daily oral azithromycin, ciprofloxacin, ethambutol and rifampin. Sputum samples collection for direct smear observation and culture as well as clinical and thorax radiography assessments were done during treatment and one year after. Cytokines and oxidative stress determinations were carried out in peripheral blood before and after treatment. RESULTS Eighteen patients were included in the IFN group and 14 received placebo. Groups were homogeneous at entry; average age was 60 years, 75% men, 84% white; MAC infection prevailed (94%). At the end of treatment, 72% of patients treated with IFN gamma were evaluated as complete responders, but only 36% in the placebo group. The difference was maintained during follow-up. A more rapid complete response was obtained in the IFN group (5 months before), with a significantly earlier improvement in respiratory symptoms and pulmonary lesions reduction. Disease-related deaths were 35.7% of the patients in the placebo group and only 11.1% in the IFN group. Three patients in the IFN group normalized their globular sedimentation rate values. Although differences in bacteriology were not significant during the treatment period, some patients in the placebo group converted again to positive during follow-up. Significant increments in serum TGF-beta and advanced oxidation protein products were observed in the placebo group but not among IFN receiving patients. Treatments were well tolerated. Flu-like symptoms predominated in the IFN gamma group. No severe events were recorded. CONCLUSION These data suggest that IFN gamma is useful and well tolerated as adjuvant therapy in patients with pulmonary atypical Mycobacteriosis, predominantly MAC. Further wider clinical trials are encouraged. TRIAL REGISTRATION Current Controlled Trials ISRCTN70900209.
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Vancini RG, Benchimol M. Entry and intracellular location of Mycoplasma hominis in Trichomonas vaginalis. Arch Microbiol 2007; 189:7-18. [PMID: 17710384 DOI: 10.1007/s00203-007-0288-8] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2007] [Revised: 06/20/2007] [Accepted: 07/04/2007] [Indexed: 10/22/2022]
Abstract
The parasite Trichomonas vaginalis causes one of the most common non-viral sexually transmitted infections in humans. The coexistence of different sexually transmitted diseases in the same individual is very common, such as vaginal infections by T. vaginalis in association with Mycoplasma fermentans or Mycoplasma hominis. However, the consequences and behavior of mycoplasma during trichomonad infections are virtually unknown. This study was undertaken to elucidate whether mycoplasmas enter and leave trichomonad cells and if so how. M. hominis was analyzed in different trichomonad isolates and the process of internalization and the pathway within the parasite was studied. Parasites naturally and experimentally infected with mycoplasmas were used and transmission electron microscopy, cytochemistry and PCR analyses were performed. The results show that: (1) M. hominis enters T. vaginalis cells by endocytosis; (2) some mycoplasmas use a terminal polar tip as anchor to the trichomonad plasma membrane; (3) some trichomonad isolates are able to digest mycoplasmas, mainly when the trichomonads are experimentally infected; (4) some fresh virulent isolates are able to maintain mycoplasmas as cohabitants in the cell's interior; (5) some mycoplasmas are able to escape from the vacuole to the trichomonad cytosol, and trichomonad plasma membrane budding suggested that mycoplasmas could leave the parasite cell.
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de Chastellier C, Thilo L. Cholesterol depletion in Mycobacterium avium-infected macrophages overcomes the block in phagosome maturation and leads to the reversible sequestration of viable mycobacteria in phagolysosome-derived autophagic vacuoles. Cell Microbiol 2006; 8:242-56. [PMID: 16441435 DOI: 10.1111/j.1462-5822.2005.00617.x] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phagocytic entry of mycobacteria into macrophages requires the presence of cholesterol in the plasma membrane. This suggests that pathogenic mycobacteria may require cholesterol for their subsequent intra-cellular survival in non-maturing phagosomes. Here we report on the effect of cholesterol depletion on pre-existing phagosomes in mouse bone marrow-derived macrophages infected with Mycobacterium avium. Cholesterol depletion with methyl-beta-cyclodextrin resulted in a loosening of the close apposition between the phagosome membrane and the mycobacterial surface, followed by fusion with lysosomes. The resulting phagolysosomes then autonomously executed autophagy, which did not involve the endoplasmic reticulum. After 5 h of depletion, intact mycobacteria had accumulated in large auto-phagolysosomes. Autophagy was specific for phagolysosomes that contained mycobacteria, as it did not involve latex bead-containing phagosomes in infected cells. Upon replenishment of cholesterol, mycobacteria became increasingly aligned to the lysosomal membrane, from where they were individually sequestered in phagosomes with an all-around closely apposed phagosome membrane and which no longer fused with lysosomes. These observations indicate that, cholesterol depletion (i) resulted in phagosome maturation and fusion with lysosomes and (ii) caused mycobacterium-containing phagolysosomes to autonomously undergo autophagy. Furthermore, (iii) mycobacteria were not killed in auto-phagolysosomes, and (iv) cholesterol replenishment enabled mycobacterium to rescue itself from autophagic phagolysosomes to again reside individually in phagosomes which no longer fused with lysosomes.
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Affiliation(s)
- Chantal de Chastellier
- Centre d'Immunologie de Marseille-Luminy, INSERM-CNRS-Université de la Méditerranée, Marseille, France.
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12
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Nepal RM, Mampe S, Shaffer B, Erickson AH, Bryant P. Cathepsin L maturation and activity is impaired in macrophages harboring M. avium and M. tuberculosis. Int Immunol 2006; 18:931-9. [PMID: 16636015 DOI: 10.1093/intimm/dxl029] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Mycobacterium tuberculosis-infected macrophages demonstrate diminished capacity to present antigens via class II MHC molecules. Since successful class II MHC-restricted antigen presentation relies on the actions of endocytic proteases, we asked whether the activities of cathepsins (Cat) B, S and L-three major lysosomal cysteine proteases-are modulated in macrophages infected with pathogenic Mycobacterium spp. Infection of murine bone marrow-derived macrophages with either Mycobacterium avium or M. tuberculosis had no obvious effect on Cat B or Cat S activity. In contrast, the activity of Cat L was altered in infected cells. Specifically, whereas the 24-kDa two-chain mature form of active Cat L predominated in uninfected cells, we observed an increase in the steady-state activity of the precursor single-chain (30 kDa) and 25-kDa two-chain forms of the enzyme in cells infected with either M. avium or M. tuberculosis. Pulse-chase analyses revealed that maturation of nascent, single-chain Cat L into the 25-kDa two-chain form was impaired in infected macrophages, and that maturation into the 24-kDa two-chain form did not occur. Consistent with these data, M. avium infection inhibited the IFNgamma-induced secretion of active two-chain Cat L by macrophages. Viable bacilli were not required to disrupt Cat L maturation, suggesting that a constitutively expressed mycobacterial component was responsible. The absence of the major active form of lysosomal Cat L in M. avium- and M. tuberculosis-infected macrophages may influence the types of T cell epitopes generated in these antigen-presenting cells, and/or the rate of class II MHC peptide loading.
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Affiliation(s)
- Rajeev M Nepal
- Department of Microbiology, Ohio State University, 484 West 12th Avenue, Columbus, OH 43210, USA
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