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Liu Y, Zhang Y, Zhao X, Lu W, Zhong Y, Fu YV. Antifungal Peptide SP1 Damages Polysaccharide Capsule of Cryptococcus neoformans and Enhances Phagocytosis of Macrophages. Microbiol Spectr 2023; 11:e0456222. [PMID: 36916981 PMCID: PMC10100895 DOI: 10.1128/spectrum.04562-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2022] [Accepted: 02/22/2023] [Indexed: 03/16/2023] Open
Abstract
Cryptococcus neoformans is a fungal pathogen which causes nearly half a million deaths worldwide each year. Under host-relevant conditions, it produces a characteristic polysaccharide capsule. The polysaccharide capsule is one of the main virulence factors of C. neoformans, which involves antiphagocytosis and immune responses of the host to cause a lack of an immune. Meanwhile, the polysaccharide capsule is a promising drug target because of the absence of analogs in the host. Here, we demonstrate that antifungal peptide SP1, which is derived from the N terminus of Saccharomyces cerevisiae GAPDH (glyceraldehyde-3-phosphate dehydrogenase), disrupts the polysaccharide capsule of C. neoformans H99. The mechanism is possibly due to the interaction of SP1 with glucuronoxylomannan (GXM). Disruption of the polysaccharide capsule enhances the adhesion and phagocytosis of C. neoformans H99 by macrophages and reduces the replication of C. neoformans H99 within macrophages. Additionally, SP1 exhibits antifungal activity against cryptococcal biofilms associated with the capsular polysaccharides. These findings suggest the potential of SP1 as a drug candidate for the treatment of cryptococcosis. IMPORTANCE C. neoformans is an opportunistic pathogen that causes invasive infections with a high mortality rate. Currently, the clinical drugs available for the treatment of cryptococcosis are limited to amphotericin B, azoles, and flucytosine. Amphotericin is nephrotoxic, and the widespread use of azoles and 5-flucytosine has led to a rapid development of drug resistance in C. neoformans. There is an urgent need to develop new and effective anticryptococcal drugs. Targeting virulence factors is a novel strategy for developing antifungal drugs. The antifungal peptide SP1 is capable of disrupting the polysaccharide capsule, which is a principal virulence factor of C. neoformans. Studying the mechanism by which SP1 damages the polysaccharide capsule and investigating the potential benefits of SP1 in removing C. neoformans from the host provides baseline data to develop a therapeutic strategy against refractory cryptococcal infections. This strategy would involve both inhibiting virulence factors and directly killing C. neoformans cells.
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Affiliation(s)
- Yan Liu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Yang Zhang
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
- School of Life Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China
| | - Xi Zhao
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Weilai Lu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
| | - Yuxin Zhong
- Department of Pancreatic and Gastric Surgery, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China
| | - Yu V. Fu
- State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, China
- Savaid Medical School, University of Chinese Academy of Sciences, Beijing, China
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Last A, Maurer M, Mosig AS, Gresnigt MS, Hube B. In vitro infection models to study fungal-host interactions. FEMS Microbiol Rev 2021; 45:6125970. [PMID: 33524102 PMCID: PMC8498566 DOI: 10.1093/femsre/fuab005] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 01/14/2021] [Indexed: 12/14/2022] Open
Abstract
Fungal infections (mycoses) affect over a billion people per year. Approximately, two million of these infections are life-threatening, especially for patients with a compromised immune system. Fungi of the genera Aspergillus, Candida, Histoplasma and Cryptococcus are opportunistic pathogens that contribute to a substantial number of mycoses. To optimize the diagnosis and treatment of mycoses, we need to understand the complex fungal–host interplay during pathogenesis, the fungal attributes causing virulence and how the host resists infection via immunological defenses. In vitro models can be used to mimic fungal infections of various tissues and organs and the corresponding immune responses at near-physiological conditions. Furthermore, models can include fungal interactions with the host–microbiota to mimic the in vivo situation on skin and mucosal surfaces. This article reviews currently used in vitro models of fungal infections ranging from cell monolayers to microfluidic 3D organ-on-chip (OOC) platforms. We also discuss how OOC models can expand the toolbox for investigating interactions of fungi and their human hosts in the future.
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Affiliation(s)
- Antonia Last
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knoell-Institute, Jena, Germany
| | - Michelle Maurer
- Center for Sepsis Control and Care (CSCC), University Hospital Jena, Jena, Germany.,Institute of Biochemistry II, Jena University Hospital, Jena, Germany
| | - Alexander S Mosig
- Center for Sepsis Control and Care (CSCC), University Hospital Jena, Jena, Germany.,Institute of Biochemistry II, Jena University Hospital, Jena, Germany
| | - Mark S Gresnigt
- Junior Research Group Adaptive Pathogenicity Strategies, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knoell-Institute, Jena, Germany
| | - Bernhard Hube
- Department of Microbial Pathogenicity Mechanisms, Leibniz Institute for Natural Product Research and Infection Biology - Hans-Knoell-Institute, Jena, Germany.,Institute of Microbiology, Friedrich Schiller University, Jena, Germany
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Cryptococcus neoformans Chitin Synthase 3 Plays a Critical Role in Dampening Host Inflammatory Responses. mBio 2020; 11:mBio.03373-19. [PMID: 32071275 PMCID: PMC7029146 DOI: 10.1128/mbio.03373-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Cryptococcus neoformans infections are significant causes of morbidity and mortality among AIDS patients and the third most common invasive fungal infection in organ transplant recipients. One of the main interfaces between the fungus and the host is the fungal cell wall. The cryptococcal cell wall is unusual among human-pathogenic fungi in that the chitin is predominantly deacetylated to chitosan. Chitosan-deficient strains of C. neoformans were found to be avirulent and rapidly cleared from the murine lung. Moreover, infection with a chitosan-deficient C. neoformans strain lacking three chitin deacetylases (cda1Δcda2Δcda3Δ) was found to confer protective immunity to a subsequent challenge with a virulent wild-type counterpart. In addition to the chitin deacetylases, it was previously shown that chitin synthase 3 (Chs3) is also essential for chitin deacetylase-mediated formation of chitosan. Mice inoculated with the chs3Δ strain at a dose previously shown to induce protection with the cda1Δcda2Δcda3Δ strain die within 36 h after installation of the organism. Mortality was not dependent on viable fungi, as mice inoculated with a heat-killed preparation of the chs3Δ strain died at the same rate as mice inoculated with a live chs3Δ strain, suggesting that the rapid onset of death was host mediated, likely caused by an overexuberant immune response. Histology, cytokine profiling, and flow cytometry indicate a massive neutrophil influx in the mice inoculated with the chs3Δ strain. Mice depleted of neutrophils survived chs3Δ inoculation, indicating that death was neutrophil mediated. Altogether, these studies lead us to conclude that Chs3, along with chitosan, plays critical roles in dampening cryptococcus-induced host inflammatory responses.IMPORTANCE Cryptococcus neoformans is the most common disseminated fungal pathogen in AIDS patients, resulting in ∼200,000 deaths each year. There is a pressing need for new treatments for this infection, as current antifungal therapy is hampered by toxicity and/or the inability of the host's immune system to aid in resolution of the disease. An ideal target for new therapies is the fungal cell wall. The cryptococcal cell wall is different from the cell walls of many other pathogenic fungi in that it contains chitosan. Strains that have decreased chitosan are less pathogenic and strains that are deficient in chitosan are avirulent and can induce protective responses. In this study, we investigated the host responses to a chs3Δ strain, a chitosan-deficient strain, and found that mice inoculated with the chs3Δ strain all died within 36 h and that death was associated with an aberrant hyperinflammatory immune response driven by neutrophils, indicating that chitosan is critical in modulating the immune response to Cryptococcus.
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Characterization of the 6-O-acetylated lipoglucuronomannogalactan a novel Cryptococcus neoformans cell wall polysaccharide. Carbohydr Res 2019; 475:1-10. [PMID: 30742969 DOI: 10.1016/j.carres.2019.01.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Revised: 01/25/2019] [Accepted: 01/28/2019] [Indexed: 12/15/2022]
Abstract
Glucuronoxylomannogalactans (GXMGals) are characteristic capsular polysaccharides produced by the opportunistic fungus C. neoformans, which are implicated in cryptococcal virulence, via impairment of the host immune response. We determined for the first time the structure of a lipoglucuronomannogalactan (LGMGal), isolated from the surface of a mutant C. neoformans carrying a deletion in the UDP-GlcA decarboxylase gene. Monosaccharide composition and methylation analyses, as well as nuclear magnetic resonance spectroscopy were employed in discerning the structure. Our results show that the polysaccharide structure of the LGMGal differs from GXMGal by the absence of xylose and 2-O-acetylated mannose residues. LGMGal consists of a galactan main chain -[-6-α-Gal-]-, where every second Gal residue is substituted at O-3 with an oligosaccharide α-Man6OAc-3-α-Man-4-(β-GlcA-3)-β-Gal-; components in italic being non-stoichiometric. The substitution rate of β-Galp units by GlcpA is 35%. Additionally, we determined that the glycolipid anchor of the LGMGal is based on an myo-inositol phosphoceramide composed of C18-phytosphingosine and monohydroxylated lignoceric acid (2OHC24:0 fatty acid).
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Caballero Van Dyke MC, Wormley FL. A Call to Arms: Quest for a Cryptococcal Vaccine. Trends Microbiol 2018; 26:436-446. [PMID: 29103990 PMCID: PMC5910246 DOI: 10.1016/j.tim.2017.10.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2017] [Revised: 09/18/2017] [Accepted: 10/13/2017] [Indexed: 12/16/2022]
Abstract
Cryptococcosis remains a significant cause of morbidity and mortality world-wide, particularly among AIDS patients. Yet, to date, there are no licensed vaccines clinically available to treat or prevent cryptococcosis. In this review, we provide a rationale to support continued investment in Cryptococcus vaccine research, potential challenges that must be overcome along the way, and a literature review of the current progress underway towards developing a vaccine to prevent cryptococcosis.
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Affiliation(s)
- Marley C Caballero Van Dyke
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX, USA
| | - Floyd L Wormley
- Department of Biology, The University of Texas at San Antonio, San Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, TX, USA.
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Mukaremera L, Lee KK, Wagener J, Wiesner DL, Gow NA, Nielsen K. Titan cell production in Cryptococcus neoformans reshapes the cell wall and capsule composition during infection. Cell Surf 2018; 1:15-24. [PMID: 30123851 PMCID: PMC6095662 DOI: 10.1016/j.tcsw.2017.12.001] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2017] [Revised: 12/05/2017] [Accepted: 12/31/2017] [Indexed: 12/21/2022] Open
Abstract
Cryptococcus neoformans is a human fungal pathogen that often causes infections in immunocompromised individuals. Upon inhalation into the lungs C. neoformans differentiates into cells with altered size and morphology, including production of large titan cells. Titan cells possess thickened cell wall and dense, cross-linked capsule when compared to in vitro grown cells. In addition, titan cells have increased cell wall chitin that is associated with a detrimental anti-inflammatory immune response. Here we examined the cell wall and capsule composition of in vitro, in vivo typical-sized and in vivo titan cells using High Performance Liquid Chromatography (HPLC). The monomer composition of cell wall polysaccharides showed that in vivo C. neoformans cells contained more glucosamine and less glucose than in vitro cells, suggesting alteration in abundance of both chitin and glucans, respectively. Low levels of galactosamine were also detected in carbohydrates from both in vivo and vitro cells. Within the in vivo cell population, differences in the proportions of cell wall and capsule monomers between typical and titan cells were also observed. Taken together, these results demonstrate that C. neoformans reshapes its cell wall and capsule composition during infection. These cell wall and capsule alterations likely help C. neoformans escape recognition by, and allow modulation of, the host immune system.
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Affiliation(s)
- Liliane Mukaremera
- Department of Microbiology and Immunology, Medical School, University of Minnesota, Minneapolis, USA
| | - Keunsook K. Lee
- MRC Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Jeanette Wagener
- MRC Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Darin L. Wiesner
- Department of Microbiology and Immunology, Medical School, University of Minnesota, Minneapolis, USA
| | - Neil A.R. Gow
- MRC Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Aberdeen, UK
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, Medical School, University of Minnesota, Minneapolis, USA
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Innate host defenses against Cryptococcus neoformans. J Microbiol 2016; 54:202-11. [PMID: 26920880 DOI: 10.1007/s12275-016-5625-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Revised: 01/11/2016] [Accepted: 01/11/2016] [Indexed: 12/21/2022]
Abstract
Cryptococcus neoformans, the predominant etiological agent of cryptococcosis, can cause life-threatening infections of the central nervous system in immunocompromised and immunocompetent individuals. Cryptococcal meningoencephalitis is the most common disseminated fungal infection in AIDS patients, and remains the third most common invasive fungal infection among organ transplant recipients. The administration of highly active antiretroviral therapy (HAART) has resulted in a decrease in the number of cases of AIDS-related cryptococcosis in developed countries, but in developing countries where HAART is not readily available, Cryptococcus is still a major concern. Therefore, there is an urgent need for the development of novel therapies and/or vaccines to combat cryptococcosis. Understanding the protective immune responses against Cryptococcus is critical for development of vaccines and immunotherapies to combat cryptococcosis. Consequently, this review focuses on our current knowledge of protective immune responses to C. neoformans, with an emphasis on innate immune responses.
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Leopold Wager CM, Hole CR, Wozniak KL, Wormley FL. Cryptococcus and Phagocytes: Complex Interactions that Influence Disease Outcome. Front Microbiol 2016; 7:105. [PMID: 26903984 PMCID: PMC4746234 DOI: 10.3389/fmicb.2016.00105] [Citation(s) in RCA: 66] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 01/19/2016] [Indexed: 12/18/2022] Open
Abstract
Cryptococcus neoformans and C. gattii are fungal pathogens that cause life-threatening disease. These fungi commonly enter their host via inhalation into the lungs where they encounter resident phagocytes, including macrophages and dendritic cells, whose response has a pronounced impact on the outcome of disease. Cryptococcus has complex interactions with the resident and infiltrating innate immune cells that, ideally, result in destruction of the yeast. These phagocytic cells have pattern recognition receptors that allow recognition of specific cryptococcal cell wall and capsule components. However, Cryptococcus possesses several virulence factors including a polysaccharide capsule, melanin production and secretion of various enzymes that aid in evasion of the immune system or enhance its ability to thrive within the phagocyte. This review focuses on the intricate interactions between the cryptococci and innate phagocytic cells including discussion of manipulation and evasion strategies used by Cryptococcus, anti-cryptococcal responses by the phagocytes and approaches for targeting phagocytes for the development of novel immunotherapeutics.
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Affiliation(s)
- Chrissy M Leopold Wager
- Department of Biology, The University of Texas at San AntonioSan Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San AntonioSan Antonio, TX, USA
| | - Camaron R Hole
- Department of Biology, The University of Texas at San AntonioSan Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San AntonioSan Antonio, TX, USA
| | - Karen L Wozniak
- Department of Biology, The University of Texas at San AntonioSan Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San AntonioSan Antonio, TX, USA
| | - Floyd L Wormley
- Department of Biology, The University of Texas at San AntonioSan Antonio, TX, USA; The South Texas Center for Emerging Infectious Diseases, The University of Texas at San AntonioSan Antonio, TX, USA
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Analysis of the Protein Kinase A-Regulated Proteome of Cryptococcus neoformans Identifies a Role for the Ubiquitin-Proteasome Pathway in Capsule Formation. mBio 2016; 7:e01862-15. [PMID: 26758180 PMCID: PMC4725006 DOI: 10.1128/mbio.01862-15] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The opportunistic fungal pathogen Cryptococcus neoformans causes life-threatening meningitis in immunocompromised individuals. The expression of virulence factors, including capsule and melanin, is in part regulated by the cyclic-AMP/protein kinase A (cAMP/PKA) signal transduction pathway. In this study, we investigated the influence of PKA on the composition of the intracellular proteome to obtain a comprehensive understanding of the regulation that underpins virulence. Through quantitative proteomics, enrichment and bioinformatic analyses, and an interactome study, we uncovered a pattern of PKA regulation for proteins associated with translation, the proteasome, metabolism, amino acid biosynthesis, and virulence-related functions. PKA regulation of the ubiquitin-proteasome pathway in C. neoformans showed a striking parallel with connections between PKA and protein degradation in chronic neurodegenerative disorders and other human diseases. Further investigation of proteasome function with the inhibitor bortezomib revealed an impact on capsule production as well as hypersusceptibility for strains with altered expression or activity of PKA. Parallel studies with tunicamycin also linked endoplasmic reticulum stress with capsule production and PKA. Taken together, the data suggest a model whereby expression of PKA regulatory and catalytic subunits and the activation of PKA influence proteostasis and the function of the endoplasmic reticulum to control the elaboration of the polysaccharide capsule. Overall, this study revealed both broad and conserved influences of the cAMP/PKA pathway on the proteome and identified proteostasis as a potential therapeutic target for the treatment of cryptococcosis. Fungi cause life-threatening diseases, but very few drugs are available to effectively treat fungal infections. The pathogenic fungus Cryptococcus neoformans causes a substantial global burden of life-threatening meningitis in patients suffering from HIV/AIDS. An understanding of the mechanisms by which fungi deploy virulence factors to cause disease is critical for developing new therapeutic approaches. We employed a quantitative proteomic approach to define the changes in the protein complement that occur upon modulating the cAMP signaling pathway that regulates virulence in C. neoformans. This approach identified a conserved role for cAMP signaling in the regulation of the ubiquitin-proteasome pathway and revealed a link between this pathway and elaboration of a major virulence determinant, the polysaccharide capsule. Targeting the ubiquitin-proteasome pathway opens new therapeutic options for the treatment of cryptococcosis.
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Real-Time Imaging of Interactions of Neutrophils with Cryptococcus neoformans Demonstrates a Crucial Role of Complement C5a-C5aR Signaling. Infect Immun 2015; 84:216-29. [PMID: 26502909 DOI: 10.1128/iai.01197-15] [Citation(s) in RCA: 32] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2015] [Accepted: 10/20/2015] [Indexed: 12/29/2022] Open
Abstract
Neutrophils have been shown to efficiently kill Cryptococcus neoformans, a causative agent of meningoencephalitis. Here, using live-cell imaging, we characterize the dynamic interactions of neutrophils with C. neoformans and the underlying mechanisms in real time. Neutrophils were directly seen to chase C. neoformans cells and then rapidly internalize them. Complement C5a-C5aR signaling guided neutrophils to migrate to the yeast cells, resulting in optimal phagocytosis and subsequent killing of the organisms. The addition of recombinant complement C5a enhanced neutrophil movement but did not induce chemotaxis, suggesting that the C5a gradient is crucial. Incubation with C. neoformans resulted in enhanced activation of Erk and p38 mitogen-activated protein (MAP) kinases (MAPKs) in neutrophils. Inhibition of the p38 MAPK pathway, but not the Erk pathway, significantly impaired neutrophil migration and its subsequent killing of C. neoformans. Deficiency of CD11b or blocking of CD11b did not affect the migration of neutrophils toward C. neoformans but almost completely abolished phagocytosis and killing of the organisms by neutrophils. C5a-C5aR signaling induced enhanced surface expression of CD11b. Interestingly, the original surface expression of CD11b was essential and sufficient for neutrophils to attach to C. neoformans but was unable to mediate phagocytosis. In contrast, the enhanced surface expression of CD11b induced by C5a-C5aR signaling was essential for neutrophil phagocytosis and subsequent killing of yeast cells. Collectively, this is the first report of the dynamic interactions of neutrophils with C. neoformans, demonstrating a crucial role of C5a-C5aR signaling in neutrophil killing of C. neoformans in real time.
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Chaturvedi AK, Wormley FL. Cryptococcus antigens and immune responses: implications for a vaccine. Expert Rev Vaccines 2014; 12:1261-72. [PMID: 24156284 DOI: 10.1586/14760584.2013.840094] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Cryptococcosis is a fungal disease primarily occurring in immunocompromised individuals, such as AIDS patients, and is associated with high morbidity and mortality. However, cryptococcosis can occur within immunocompetent populations as observed during an outbreak in Vancouver Island, British Columbia, Canada, the Pacific Northwest and other regions of the USA and in Mediterranean Europe. Mortality rates due to cryptococcosis have significantly declined in economically developed countries since the widespread implementation of highly active antiretroviral therapy. However, the incidence and mortality of this disease remains high in economically undeveloped areas in Africa and Asia where HIV infections are high and availability of HAART is limited. The continuing AIDS epidemic coupled with the increased usage of immunosuppressive drugs to prevent organ transplant rejection or to treat autoimmune diseases has resulted in an increase in individuals at risk for developing cryptococcosis. The purpose of this review is to discuss the need, challenges and potential for developing vaccines against cryptococcosis.
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Affiliation(s)
- Ashok K Chaturvedi
- Department of Biology and The South Texas Center for Emerging Infectious Diseases, The University of Texas, San Antonio, TX, USA
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Vecchiarelli A, Monari C. Capsular Material of Cryptococcus neoformans: Virulence and Much More. Mycopathologia 2012; 173:375-386. [PMID: 22314939 DOI: 10.1007/s11046-011-9513-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2011] [Accepted: 11/28/2011] [Indexed: 01/08/2023]
Abstract
The capsule is generally considered one of the more powerful virulence factors of microorganisms, driving research in the field of microbial pathogenesis and in the development of vaccines. Cryptococcus neoformans is unique among the most common human fungal pathogens in that it possesses a complex polysaccharide capsule. This review focuses on the Cryptococcus neoformans capsule from the viewpoint of fungal pathogenesis, and the effective immune response target of the capsule's main component, glucuronoxylomannan.
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Affiliation(s)
- A Vecchiarelli
- Department of Experimental Medicine and Biochemical Sciences, Microbiology Section, University of Perugia, Via del Giochetto, 06126, Perugia, Italy,
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Mitchell TG, Verweij P, Hoepelman AI. Opportunistic and systemic fungi. Infect Dis (Lond) 2010. [DOI: 10.1016/b978-0-323-04579-7.00178-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022] Open
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Phagocytosis inhibits F-actin-enriched membrane protrusions stimulated by fractalkine (CX3CL1) and colony-stimulating factor 1. Infect Immun 2009; 77:4487-95. [PMID: 19620351 DOI: 10.1128/iai.00530-09] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Cryptococcus neoformans is the only encapsulated human-pathogenic fungus and a facultative intracellular pathogen that can reside in macrophages without host cell lysis. In the present study, we investigated how phagocytosis of C. neoformans affected the macrophage response to chemoattractants such as fractalkine (FKN) (CX3CL1) and colony-stimulating factor 1 (CSF-1). Phagocytosis of immunoglobulin G (IgG)-opsonized C. neoformans and IgG- or C3bi-opsonized sheep erythrocytes was performed using a RAW 264.7 subline (LR5 cells) and bone marrow-derived macrophages (BMM). The chemotactic response to FKN or CSF-1 was quantitated by measurement of the formation of F-actin-enriched membrane protrusions (ruffles), which showed that FKN or CSF-1 stimulated strong transient ruffling in both LR5 cells and BMM. This stimulated cell ruffling was inhibited by phagocytosis in an intracellular-pathogen-number-dependent manner. The inhibition of ruffling was not simply a result of reduced membrane availability since membrane sequestration by sucrose treatment did not inhibit the ruffling response. The phagocytosis process was required to inhibit ruffling as BMM from Fc gamma (-/-) mice that bound C. neoformans but did not ingest it retained the ability to ruffle in response to chemoattractants. These results imply that the inhibition of FKN- or CSF-1-stimulated cell ruffling was a direct consequence of the phagocytosis process. Since cell ruffling is a prelude to chemotaxis, this observation links two functions of macrophages that are critical to host defense, chemotaxis and phagocytosis. Phagocytosis-induced chemotactic suppression may enhance host defense by keeping these antimicrobial effector cells at infected sites and reduce the likelihood of microbial spread by wandering macrophages containing infectious cargo.
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Production of extracellular polysaccharides by CAP mutants of Cryptococcus neoformans. EUKARYOTIC CELL 2009; 8:1165-73. [PMID: 19542308 DOI: 10.1128/ec.00013-09] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The human pathogen Cryptococcus neoformans causes meningoencephalitis. The polysaccharide capsule is one of the main virulence factors and consists of two distinct polysaccharides, glucuronoxylomannan (GXM) and galactoxylomannan (GalXM). How capsular polysaccharides are synthesized, transported, and assembled is largely unknown. Previously, it was shown that mutations in the CAP10, CAP59, CAP60, and CAP64 genes result in an acapsular phenotype. Here, it is shown that these acapsular mutants do secrete GalXM and GXM-like polymers. GXM and GalXM antibodies specifically reacted with whole cells and the growth medium of the wild type and CAP mutants, indicating that the capsule polysaccharides adhere to the cell wall and are shed into the environment. These polysaccharides were purified from the medium, either with or without anion-exchange chromatography. Monosaccharide analysis of polysaccharide fractions by gas-liquid chromatography/mass spectrometry showed that wild-type cells secrete both GalXM and GXM. The CAP mutants, on the other hand, were shown to secrete GalXM and GXM-like polymers. Notably, the GalXM polymers were shown to contain glucuronic acid. One-dimensional (1)H nuclear magnetic resonance confirmed that the CAP mutants secrete GalXM and also showed the presence of O-acetylated polymers. This is the first time it is shown that CAP mutants secrete GXM-like polymers in addition to GalXM. The small amount of this GXM-like polymer, 1 to 5% of the total amount of secreted polysaccharides, may explain the acapsular phenotype.
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Wozniak KL, Levitz SM. Isolation and purification of antigenic components of Cryptococcus. Methods Mol Biol 2009; 470:71-83. [PMID: 19089377 DOI: 10.1007/978-1-59745-204-5_7] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The encapsulated fungal pathogens Cryptococcus neoformans and Cryptococcus gattii are significant agents of life-threatening infections, particularly in persons with suppressed cell-mediated immunity. This chapter provides detailed methodology for the purification of two of the major antigen fractions of C. neoformans: glucuronoxylomannan (GXM) and mannoprotein (MP). GXM is the primary component of the polysaccharide capsule, which is the major cryptococcal virulence factor. In contrast, MPs have been identified as key antigens that stimulate T-cell responses. Purification of GXM and MP should assist investigators studying the antigenic, biochemical, and virulence properties of Cryptococcus species.
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Affiliation(s)
- Karen L Wozniak
- Department of Medicine and Microbiology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
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17
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Jongerius I, Köhl J, Pandey MK, Ruyken M, van Kessel KPM, van Strijp JAG, Rooijakkers SHM. Staphylococcal complement evasion by various convertase-blocking molecules. ACTA ACUST UNITED AC 2007; 204:2461-71. [PMID: 17893203 PMCID: PMC2118443 DOI: 10.1084/jem.20070818] [Citation(s) in RCA: 176] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
To combat the human immune response, bacteria should be able to divert the effectiveness of the complement system. We identify four potent complement inhibitors in Staphylococcus aureus that are part of a new immune evasion cluster. Two are homologues of the C3 convertase modulator staphylococcal complement inhibitor (SCIN) and function in a similar way as SCIN. Extracellular fibrinogen-binding protein (Efb) and its homologue extracellular complement-binding protein (Ecb) are identified as potent complement evasion molecules, and their inhibitory mechanism was pinpointed to blocking C3b-containing convertases: the alternative pathway C3 convertase C3bBb and the C5 convertases C4b2aC3b and C3b2Bb. The potency of Efb and Ecb to block C5 convertase activity was demonstrated by their ability to block C5a generation and C5a-mediated neutrophil activation in vitro. Further, Ecb blocks C5a-dependent neutrophil recruitment into the peritoneal cavity in a mouse model of immune complex peritonitis. The strong antiinflammatory properties of these novel S. aureus–derived convertase inhibitors make these compounds interesting drug candidates for complement-mediated diseases.
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Affiliation(s)
- Ilse Jongerius
- Medical Microbiology, University Medical Center Utrecht, 3584 CX Utrecht, Netherlands.
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18
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Chavakis T, Preissner KT, Herrmann M. The anti-inflammatory activities of Staphylococcus aureus. Trends Immunol 2007; 28:408-18. [PMID: 17681885 DOI: 10.1016/j.it.2007.07.002] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2007] [Revised: 05/29/2007] [Accepted: 07/17/2007] [Indexed: 11/30/2022]
Abstract
Staphylococcus aureus is a versatile and harmful pathogen in both hospital- and community-associated infections that range from superficial to systemic infections. S. aureus engages a multitude of mechanisms to subvert the innate immune response of the host, including inhibition of complement activation and neutralization of anti-microbial peptides. In addition, inflammatory cell and phagocyte recruitment is an integral part of the innate defense to staphylococcal infection and comprises a well-coordinated multi-step cascade of adhesive events. Recent and rapidly growing experimental evidence indicates the existence of a machinery of anti-adhesive and anti-chemotactic moieties of S. aureus that allow the bacterium to interfere with specific adhesive steps of the homing mechanism of leukocytes. Understanding the functions of these S. aureus-derived anti-inflammatory agents could also provide the platform for designing new therapies in several inflammatory and autoimmune diseases.
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Affiliation(s)
- Triantafyllos Chavakis
- Experimental Immunology Branch, National Cancer Institute, NIH, Bethesda, MD 20892, USA.
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19
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The Neutrophil. IMMUNOLOGY OF FUNGAL INFECTIONS 2007. [PMCID: PMC7122062 DOI: 10.1007/1-4020-5492-0_3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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20
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Abstract
Many microbial pathogens evolved to circumvent the attack of neutrophils, which are essential effector cells of the innate immune system. Here we review six major strategies that pathogenic bacteria and fungi use to evade neutrophil defences: (i) turning on survival and stress responses, (ii) avoiding contact, (iii) preventing phagocytosis, (iv) surviving intracellularly, (v) inducing cell death and (vi) evading killing by neutrophil extracellular traps. For each category we give examples and further focus on one particular pathogenic microbe in more detail. Pathogens include Candida albicans, Cryptococcus neoformans, Yersinia ssp., Helicobacter pylori, Staphylococcus aureus, Streptococcus pyogenes and Streptococcus pneumoniae.
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Affiliation(s)
- Constantin F Urban
- Department of Cellular Microbiology, Max Planck Institute for Infection Biology, Charitéplatz 1, 10117 Berlin, Germany
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21
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Levitz SM, Specht CA. The molecular basis for the immunogenicity of Cryptococcus neoformans mannoproteins. FEMS Yeast Res 2006; 6:513-24. [PMID: 16696647 DOI: 10.1111/j.1567-1364.2006.00071.x] [Citation(s) in RCA: 110] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
T-cell-mediated immunity is necessary for effective host defenses against infections caused by Cryptococcus neoformans. Clinical and experimental studies have identified a heterogeneous family of mannoproteins as critical cryptococcal antigens responsible for stimulating T-cell responses. The archetypal mannoprotein has a signal sequence, a functional domain, a serine/threonine-rich region and a site for attachment of a glycosylphosphatidylinositol anchor. Extensive O-mannosylation, which occurs at the serine/threonine region, facilitates recognition by mannose receptors on antigen-presenting cells, particularly dendritic cells. This results in efficient antigen uptake, processing and presentation to T cells. Inhibition of mannose receptors or deglycosylation of mannoproteins profoundly inhibits T-cell responses, demonstrating the crucial contribution of mannosylation to immunogenicity.
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Affiliation(s)
- Stuart M Levitz
- Department of Medicine, Boston Medical Center and Boston University School of Medicine, Boston, MA 02118, USA.
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22
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Lortholary O, Sitbon K, Dromer F. Evidence for human immunodeficiency virus and Cryptococcus neoformans interactions in the pro-inflammatory and anti-inflammatory responses in blood during AIDS-associated cryptococcosis. Clin Microbiol Infect 2005; 11:296-300. [PMID: 15760426 DOI: 10.1111/j.1469-0691.2005.01074.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Tumour necrosis factor-alpha (TNF-alpha), interleukin (IL)-6, -8 and-10 and soluble TNF receptor II (sTNFR II) levels were measured at baseline, and after antifungal therapy for 2 weeks and 3 months, in plasma from 75 human immunodeficiency virus (HIV)-positive and 14 HIV-negative patients with cryptococcosis, and in plasma from 14 HIV-positive controls. At baseline, TNF-alpha, IL-6 and sTNFR II levels, and cryptococcal antigen titres, were increased in patients with fungaemia compared to controls (p < 0.02). The mediator levels were not influenced by the severity of the disease or subsequent death, but sTNFR II and IL-10 levels were reduced, together with virus load, in patients receiving anti-retroviral agents (p < 0.01). During antifungal therapy, sTNFR II levels decreased (p 0.003) in parallel with the virus load and with an increase in CD4 T-cell numbers.
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Affiliation(s)
- O Lortholary
- Unité de Mycologie Moléculaire, Centre National de Référence Mycologie et Antifongiques, Institut Pasteur, Paris, France.
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23
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Pietrella D, Corbucci C, Perito S, Bistoni G, Vecchiarelli A. Mannoproteins from Cryptococcus neoformans promote dendritic cell maturation and activation. Infect Immun 2005; 73:820-7. [PMID: 15664921 PMCID: PMC547028 DOI: 10.1128/iai.73.2.820-827.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Our previous data show that mannoproteins (MPs) from Cryptococcus neoformans are able to induce protective responses against both C. neoformans and Candida albicans. Here we provide evidence that MPs foster maturation and activation of human dendritic cells (DCs). Maturation was evaluated by the ability of MPs to facilitate expression of costimulatory molecules such as CD40, CD86, CD83, and major histocompatibility complex classes I and II and to inhibit receptors such as CD14, CD16, and CD32. Activation of DCs was measured by the capacity of MPs to promote interleukin-12 and tumor necrosis factor alpha secretion. DC-induced maturation and interleukin-12 induction are largely mediated by engagement of mannose receptors and presume MP internalization and degradation. DC activation leads to IkappaBalpha phosphorylation, which is necessary for nuclear factor kappaB transmigration into the nucleus. MP-loaded DCs are efficient stimulators of T cells and show a remarkable capacity to promote CD4 and CD8 proliferation. In conclusion, we have evidenced a novel regulatory role of MPs that promotes their candidacy as a vaccine against fungi.
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Affiliation(s)
- Donatella Pietrella
- Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Via del Giochetto, 06122 Perugia, Italy
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24
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Ellerbroek PM, Lefeber DJ, van Veghel R, Scharringa J, Brouwer E, Gerwig GJ, Janbon G, Hoepelman AIM, Coenjaerts FEJ. O-acetylation of cryptococcal capsular glucuronoxylomannan is essential for interference with neutrophil migration. THE JOURNAL OF IMMUNOLOGY 2005; 173:7513-20. [PMID: 15585878 DOI: 10.4049/jimmunol.173.12.7513] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The capsular polysaccharide glucuronoxylomannan (GXM) of Cryptococcus neoformans has been shown to interfere with neutrophil migration. Although several receptors have been implied to mediate this process, the structural perspectives are unknown. Here, we assess the contribution of 6-O-acetylation and xylose substitution of the (1-->3)-alpha-d-mannan backbone of GXM, the variable structural features of GXM, to the interference with neutrophil migration. We compare chemically deacetylated GXM and acetyl- or xylose-deficient GXM from genetically modified strains with wild-type GXM in their ability to inhibit the different phases of neutrophil migration. Additionally, we verify the effects of de-O-acetylation on neutrophil migration in vivo. De-O-acetylation caused a dramatic reduction of the inhibitory capacity of GXM in the in vitro assays for neutrophil chemokinesis, rolling on E-selectin and firm adhesion to endothelium. Genetic removal of xylose only marginally reduced the ability of GXM to reduce firm adhesion. In vivo, chemical deacetylation of GXM significantly reduced its ability to interfere with neutrophil recruitment in a model of myocardial ischemia (65% reduction vs a nonsignificant reduction in tissue myeloperoxidase, respectively). Our findings indicate that 6-O-acetylated mannose of GXM is a crucial motive for the inhibition of neutrophil recruitment.
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Affiliation(s)
- Pauline M Ellerbroek
- Department of Infectious Diseases, Division of Internal Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
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25
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Pietrella D, Lupo P, Bistoni F, Vecchiarelli A. An early imbalance of interleukin 12 influences the adjuvant effect of mannoproteins of Cryptococcus neoformans. Cell Microbiol 2005; 6:883-91. [PMID: 15272868 DOI: 10.1111/j.1462-5822.2004.00411.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Mannoprotein from Cryptococcus neoformans induces protective response against a lethal challenge with this fungus or with Candida albicans. This phenomenon is largely related to early production of interleukin 12 (IL-12) and induction of T helper 1 response. Our study assesses whether the early absence of this critical cytokine could account for the incomplete activation of cellular response and whether the immune system compensates this imbalance. The results show that the neutralization of early IL-12 enhanced IL-18 production but decreased IFN-gamma secretion and IL-12R expression by splenic CD4 T cells. In contrast, IL-18R was not augmented despite an increase in IL-18 production. The co-stimulatory pathway was partially dysregulated because splenic macrophages showed unmodified B7-2, and a decrease of B7-1 expression. This dysregulation led to incomplete proliferative response of T cells in response to Cryptococcus neoformans and to increased fungal load in the brain 21 days post infection. The inability to dispose early IL-12, forced the immune system to compensate the imbalance and produced a series of long-lasting dysregulations involving the co-stimulatory pathway and T cell activation.
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Affiliation(s)
- Donatella Pietrella
- Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
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26
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Rodrigues ARTS, Heise N, Previato JO, Mendonça-Previato L, Peçanha LMT. B cell response during infection with the MAT a and MAT alpha mating types of Cryptococcus neoformans. Microbes Infect 2005; 7:118-25. [PMID: 15716070 DOI: 10.1016/j.micinf.2004.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Revised: 08/23/2004] [Accepted: 09/15/2004] [Indexed: 10/26/2022]
Abstract
In the present study, we compared the B cell response of BALB/c and C57Bl/6 mice during Cryptococcus neoformans infection. This response was investigated using virulent serotype D forms of mating types alpha and a (MAT alpha and MAT a). C57Bl/6 mice showed massive (mainly cerebral) infection by both types, while BALB/c were resistant to infection. Some resistance of C57Bl/6 mice was induced by previous immunization with the capsular polysaccharide from MAT alpha. Passive immunization of C57Bl/6 mice with purified antibody (Ab) obtained from capsular polysaccharide-immunized mice also increased resistance to infection. Both mouse strains showed comparable low IgM response to the capsular polysaccharide from MAT alpha, and only C57Bl/6 mice produced IgM to the polysaccharide of MAT a. Comparable levels of different immunoglobulin (Ig) isotypes against capsular components of MAT alpha and MAT a were detected, and the response of C57Bl/6 mice was higher when compared to that of BALB/c mice. FACS analysis indicated an increase in the percentage of a high-granulosity (side-scatter) splenic subpopulation and in the percentage of splenic Gr-1+ cells in infected C57Bl/6 mice. In addition, the percentage of follicular splenic B cells was decreased after C. neoformans infection of C57Bl/6 mice. This response was more pronounced when we investigated infection induced by the MAT a mating type. Taken together, our results indicate that capsular polysaccharide derived from MAT alpha and MAT a types of C. neoformans have a stimulatory effect upon B cells but that there is no correlation between resistance of BALB/c mice and Ab production. However, the increase in resistance of C57Bl/6 mice parallels the production of Abs and a major change in splenic cell populations.
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Affiliation(s)
- Adila Regina T Santos Rodrigues
- Instituto de Microbiologia Professor Paulo de Góes, CCS, Bloco I, Universidade Federal do Rio de Janeiro, Cidade Universitária, Ilha do Fundão, Rio de Janeiro, RJ 21944-570, Brazil
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27
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Ellerbroek PM, Schoemaker RG, van Veghel R, Hoepelman AIM, Coenjaerts FEJ. Cryptococcal capsular glucuronoxylomannan reduces ischaemia-related neutrophil influx. Eur J Clin Invest 2004; 34:631-40. [PMID: 15379763 DOI: 10.1111/j.1365-2362.2004.01393.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND The capsular polysaccharide glucuronoxylomannan (GXM) of Cryptococcus neoformans interferes with the chemotaxis and transendothelial migration of neutrophils. Intravenous administration of purified GXM has been shown to reduce the influx of inflammatory cells in an animal model of bacterial infection. Here we show that isolated GXM can also interfere with neutrophil migration in a model of inflammation not related to infection. We assessed the effects of intravenous GXM on neutrophil infiltration in a rat model of myocardial ischaemia, where neutrophil infiltration has been shown to contribute to postischaemic reperfusion injury. MATERIALS AND METHODS Rats were subjected to coronary artery ligation followed by a 3-h reperfusion period. Myeloperoxidase-activity was measured in the ischaemic tissues as a marker of neutrophil infiltration. RESULTS Intravenous administration of GXM markedly reduced the influx of neutrophils in the ischaemic myocardium as measured by a 65% reduction of tissue MPO activity. This reduction of MPO activity was clearly correlated to the serum concentration of GXM. As complement activation by GXM was minimal at the doses applied in vivo, it is unlikely that generation of chemotactic C5a in the circulation by GXM caused the observed reduction in leucocyte migration. CONCLUSION Purified cryptococcal GXM has the ability to reduce neutrophil influx even outside the scope of infection.
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Affiliation(s)
- P M Ellerbroek
- University Medical Centre Utrecht, Utrecht, the Netherlands.
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28
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Postma B, Poppelier MJ, van Galen JC, Prossnitz ER, van Strijp JAG, de Haas CJC, van Kessel KPM. Chemotaxis inhibitory protein of Staphylococcus aureus binds specifically to the C5a and formylated peptide receptor. THE JOURNAL OF IMMUNOLOGY 2004; 172:6994-7001. [PMID: 15153520 DOI: 10.4049/jimmunol.172.11.6994] [Citation(s) in RCA: 165] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Chemotaxis inhibitory protein of Staphylococcus aureus (CHIPS) is an exoprotein produced by several strains of S. aureus, and a potent inhibitor of neutrophil and monocyte chemotaxis toward C5a and formylated peptides like fMLP. These chemoattractants act on their target cells by binding and activating the C5aR and formylated peptide receptor (FPR), respectively. In the present report, we examined the mechanism by which CHIPS affects both of these receptors. We showed that CHIPS blocked binding of anti-C5aR mAb and formylated peptide to human neutrophils as efficiently at temperatures of 0 and 37 degrees C, implying that it is independent of signal transducing systems. This was confirmed by showing that CHIPS acts completely independently of ATP. Additionally, CHIPS was not internalized upon binding to neutrophils. Furthermore, we showed that CHIPS binds specifically to the C5aR and FPR expressed on U937 cells. This binding was functional in blocking C5a- and fMLP-induced calcium mobilization in these cell lines. These results suggest that CHIPS binds directly to the C5aR and FPR, thereby preventing the natural ligands from activating these receptors. The apparent K(d) values of CHIPS for the C5aR and FPR were 1.1 +/- 0.2 nM and 35.4 +/- 7.7 nM, respectively. Moreover, after screening a wide variety of other G protein-coupled receptors, CHIPS was found to affect exclusively the C5aR and FPR. This selectivity and high-affinity binding with potent antagonistic effects makes CHIPS a promising lead for the development of new anti-inflammatory compounds for diseases in which damage by neutrophils plays a key role.
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Affiliation(s)
- Bent Postma
- Eijkman-Winkler Institute, University Medical Center Utrecht, Utrecht, The Netherlands
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29
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Ellerbroek PM, Ulfman LH, Hoepelman AI, Coenjaerts FEJ. Cryptococcal glucuronoxylomannan interferes with neutrophil rolling on the endothelium. Cell Microbiol 2004; 6:581-92. [PMID: 15104598 DOI: 10.1111/j.1462-5822.2004.00384.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The major capsular polysaccharide glucuronoxylomannan (GXM) of the pathogenic fungus Cryptococcus neoformans has been associated with depression of a variety of immunological host responses. For one, GXM has been shown to interfere with the migration of phagocytes to sites of inflammation by interference with both chemokinesis and leucocyte adhesion to the endothelium. We reported previously that GXM blocks the firm adhesion of neutrophils (PMNs) to endothelium in a static adhesion model, most probably by interfering with E-selectin binding pathways. Using a flow model, we now demonstrate that GXM also interferes with the initial rolling phase of PMN adhesion to endothelium (40% decrease) as well as to E-selectin-transfected CHO cells (43% inhibition). Furthermore, we show that CD14 and TLR4, which are known receptors for GXM, mediate this interference with PMN rolling. However, thus far, we are not able to identify the ligand of E-selectin on the surface of PMNs that is specifically affected by GXM. In conclusion, cryptococcal GXM interferes with both rolling and fixed binding of neutrophils on the endothelium, providing a novel means of contributing to the absence of neutrophil infiltration observed in cryptococcal infections.
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Affiliation(s)
- Pauline M Ellerbroek
- Division of Acute Internal Medicine and Infectious Diseases, University Medical Centre Utrecht, Heidelberglaan 100, 3508 GA, Utrecht, The Netherlands.
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30
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Mansour MK, Yauch LE, Rottman JB, Levitz SM. Protective efficacy of antigenic fractions in mouse models of cryptococcosis. Infect Immun 2004; 72:1746-54. [PMID: 14977983 PMCID: PMC356047 DOI: 10.1128/iai.72.3.1746-1754.2004] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Infections due to the encapsulated fungus Cryptococcus neoformans are a significant cause of morbidity and mortality in patients with impaired T-cell function, particularly those with AIDS. Presumably then, T-cell responses to cryptococcal antigens are critical for protection against this ubiquitous fungus. To test the protective efficacy of these antigens as vaccine candidates, secreted cryptococcal antigens were separated by concanavalin A affinity chromatography into adherent (mannoprotein [MP]) and nonadherent (flowthrough [FT]) fractions, and the fractions were tested in murine models of disseminated cryptococcosis. Compared with adjuvant alone, C57BL/6 mice that received two inoculations of MP and FT exhibited prolonged survival and reduced brain and kidney fungal loads following intravenous challenge with C. neoformans strain B3501. MP-immunized animals had increased brain levels of tumor necrosis factor alpha, gamma interferon, and interleukin-2. Histopathologic examination revealed that compared with organs from mice that received only adjuvant, MP-immunized mice were able to recruit a stronger cellular infiltrate in brain, kidney, and liver in response to cryptococcal infection. Conjugated O-linked glycans were necessary for optimal MP-mediated protection, because chemical O deglycosylation reduced the protective efficacy of MP immunization. FT and MP immunization protected B-cell-deficient, but not T-cell-deficient mice, suggesting that protection was T-cell mediated. CBA/J mice also benefited from immunization with FT and MP, although the benefits were more modest than those seen with C57BL/6 mice. Thus, both MP and FT fractions of C. neoformans contain components that protect mice from disseminated cryptococcosis, and this protection appears to be T-cell mediated.
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Affiliation(s)
- Michael K Mansour
- Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA
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31
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Walenkamp AME, Ellerbroek P, Scharringa J, Rijkers E, Hoepelman AIM, Coenjaerts FEJ. Interference of Cryptococcus neoformans with human neutrophil migration. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2003; 531:315-39. [PMID: 12916803 DOI: 10.1007/978-1-4615-0059-9_27] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 03/02/2023]
Affiliation(s)
- Annemiek M E Walenkamp
- Department of Medicine, Division Acute Medicine and Infectious Diseases, and Eijkman-Winkler Center for Microbiology, Infectious diseases and Inflammation, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands
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32
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Bose I, Reese AJ, Ory JJ, Janbon G, Doering TL. A yeast under cover: the capsule of Cryptococcus neoformans. EUKARYOTIC CELL 2003; 2:655-63. [PMID: 12912884 PMCID: PMC178345 DOI: 10.1128/ec.2.4.655-663.2003] [Citation(s) in RCA: 164] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Indrani Bose
- Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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Wright L, Bubb W, Davidson J, Santangelo R, Krockenberger M, Himmelreich U, Sorrell T. Metabolites released by Cryptococcus neoformans var. neoformans and var. gattii differentially affect human neutrophil function. Microbes Infect 2002; 4:1427-38. [PMID: 12475633 DOI: 10.1016/s1286-4579(02)00024-2] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
Differences in the ability of Cryptococcus neoformans var. neoformans (CNVN) and var. gattii (CNVG) to establish localized lesions in the lungs of healthy humans remain unexplained. In this study, CNVG infection in a rat model was characterized by early neutrophil invasion into lung tissue, but phagocytosis of cryptococci was not observed. The chemical composition of non-enzymic components secreted by one strain of each variety (heat-inactivated supernatants from CNVN and CNVG, termed vns and vgs, respectively) were compared, using magnetic resonance spectroscopy. Effects on human neutrophil viability and functions at both pH 5.5 and 7.0 were investigated, as the pH of cryptococcomas was found to be 5.4-5.6 in vivo. The supernatants were similar in composition, although metabolites in vns were generally present in higher concentrations. In addition, vgs contained two novel metabolites-acetoin and dihydroxyacetone. Polyphosphate was observed in cells from both varieties and may be a source of extracellular inorganic phosphate. Superoxide production in the presence of phorbol ester was enhanced by treatment with vns and decreased by vgs. At pH 5.5, vns caused high levels of necrosis in neutrophils, as well as increased adhesion/migration through A549 lung epithelial cell monolayers. Individual supernatant components such as polyols, acetoin, dihydroxyacetone, and gamma-aminobutyric acid exhibited both pro- and anti-inflammatory properties. Overall, we found that vgs was potentially less pro-inflammatory than vns. Inhibition of neutrophil function by products of CNVG may promote survival of extracellular organisms, and local multiplication to form cryptococcomas.
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Affiliation(s)
- Lesley Wright
- Department of Infectious Diseases, Center for Infectious Diseases and Microbiology, Level 3, ICPMR Building, University of Sydney, Westmead Hospital, Westmead, NSW 2145, Australia.
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34
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Ellerbroek PM, Hoepelman AIM, Wolbers F, Zwaginga JJ, Coenjaerts FEJ. Cryptococcal glucuronoxylomannan inhibits adhesion of neutrophils to stimulated endothelium in vitro by affecting both neutrophils and endothelial cells. Infect Immun 2002; 70:4762-71. [PMID: 12183517 PMCID: PMC128235 DOI: 10.1128/iai.70.9.4762-4771.2002] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cryptococcal infections are often characterized by a paucity of leukocytes in the infected tissues. Previous research has shown that the capsular polysaccharide glucuronoxylomannan (GXM) inhibits leukocyte migration. In this study we investigated whether the capsular polysaccharide GXM affects the migration of neutrophils (polymorphonuclear leukocytes [PMN]) through the endothelium by interfering with adhesion in a static adhesion model. Pretreatment of PMN with GXM inhibited PMN adhesion to tumor necrosis factor alpha (TNF-alpha)-stimulated endothelium up to 44%. Treatment of TNF-alpha-stimulated endothelium with GXM led to a 27% decrease in PMN adhesion. GXM treatment of both PMN and endothelium did not have an additive inhibitory effect. We demonstrated that GXM-induced L-selectin shedding does not play an important role in the detected inhibition of adhesion. L-selectin was still present on PMN in sufficient amounts after GXM treatment, since it could be further inhibited by blocking antibodies. Furthermore, blocking of GXM-related L-selectin shedding did not abolish the GXM-related inhibition of adhesion. GXM most likely exerts its effect on PMN by interfering with E-selectin-mediated binding. The use of blocking monoclonal antibodies against E-selectin, which was shown to decrease adhesion in the absence of GXM, did not cause additive inhibition of PMN adhesion after GXM pretreatment. The use of blocking antibodies also demonstrated that the inhibiting effect found after GXM treatment of endothelium probably involves interference with both intercellular adhesion molecule-1 and E-selectin binding.
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Affiliation(s)
- Pauline M Ellerbroek
- Division of Acute Medicine and Infectious Diseases, Eijkman Winkler Institute for Microbiology, University Medical Centre Utrecht, The Netherlands.
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35
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Abstract
Recent advances have broadened our knowledge of the unique role that dendritic cells, macrophages and neutrophils play in protecting the host against fungal infections and the mechanisms by which fungal pathogens attempt to subvert phagocytic defenses. In this article, the interplay between phagocytes and fungi is reviewed.
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Affiliation(s)
- Michael K Mansour
- The Department of Microbiology and the Immunology Training Program, Boston University School of Medicine, Room X626, 650 Albany Street, Boston, Massachusetts 02118, USA.
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36
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Abstract
In inflammation, neutrophils roll along the endothelial wall of postcapillary venules and sample inflammatory signals. Neutrophil activation is required to generate beta(2) integrin bonds with the endothelium that are strong enough to withstand the flow forces and thus achieve arrest from the rolling state. Unlike naïve T cells, neutrophils are not only activated by ligation of G-protein coupled receptors with chemokines and other chemoattractants but also receive signals from engagement of adhesion molecules including the selectins and beta(2) integrins. Rolling neutrophils integrate the sum total of inputs received while scanning the inflamed endothelium. In this process, the velocity of rolling neutrophils systematically decreases as a function of their contact time with the inflamed endothelium. If an activation threshold is reached, beta(2) integrins switch to the high-affinity conformation, redistribute on the cell surface, and trigger arrest and adhesion. Rolling cells that do not reach the activation threshold detach from the endothelium and are released back into the circulation. The role of chemokines, adhesion molecules, and other activating inputs involved in this response as well as signaling pathways are the subjects of ongoing investigations. This review provides a conceptual framework for neutrophil recruitment from the flowing blood.
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Affiliation(s)
- Klaus Ley
- Cardiovascular Research Center, University of Virginia Health System, Cardiovascular Research Center, Charlottesville, VA 22908-1394, USA.
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