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Mendoza SR, da Silva Ferreira M, Valente MR, Guimarães AJ. Antibody Isolation in C. neoformans. Methods Mol Biol 2024; 2775:307-328. [PMID: 38758326 DOI: 10.1007/978-1-0716-3722-7_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
The importance of humoral immunity to fungal infections remains to be elucidated. In cryptococcosis, patients that fail to generate antibodies against antigens of the fungus Cryptococcus neoformans are more susceptible to the disease, demonstrating the importance of these molecules to the antifungal immune response. Historically, antibodies against C. neoformans have been applied in diagnosis, therapeutics, and as important research tools to elucidate fungal biology. Throughout the process of generating monoclonal antibodies (mAbs) from a single B-cell clone and targeting a single epitope, several immunization steps might be required for the detection of responsive antibodies to the antigen of interest in the serum. This complex mixture of antibodies comprises the polyclonal antibodies. To obtain mAbs, B-lymphocytes are harvested (from spleen or peripheral blood) and fused with tumor myeloma cells, to generate hybridomas that are individually cloned and specifically screened for mAb production. In this chapter, we describe all the necessary steps, from the immunization to polyclonal antibody harvesting, hybridoma generation, and mAb production and purification. Additionally, we discuss new cutting-edge approaches for generating interspecies mAbs, such as humanized mAbs, or for similar species in distinct host backgrounds.
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Affiliation(s)
- Susana Ruiz Mendoza
- Laboratório de Bioquímica e Imunologia das Micoses, Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil
- Pós-Graduação em Imunologia e Inflamação, Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Marina da Silva Ferreira
- Laboratório de Bioquímica e Imunologia das Micoses, Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil
- Pós-Graduação em Imunologia e Inflamação, Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil
| | - Michele Ramos Valente
- Laboratório de Bioquímica e Imunologia das Micoses, Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil
- Programa de Pós-Graduação em Microbiologia e Parasitologia Aplicadas, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil
| | - Allan Jefferson Guimarães
- Laboratório de Bioquímica e Imunologia das Micoses, Departamento de Microbiologia e Parasitologia, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil.
- Pós-Graduação em Imunologia e Inflamação, Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, RJ, Brazil.
- Programa de Pós-Graduação em Microbiologia e Parasitologia Aplicadas, Instituto Biomédico, Fluminense Federal University, Niterói, RJ, Brazil.
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Involvement of the capsular GalXM-induced IL-17 cytokine in the control of Cryptococcus neoformans infection. Sci Rep 2018; 8:16378. [PMID: 30401972 PMCID: PMC6219535 DOI: 10.1038/s41598-018-34649-4] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2018] [Accepted: 10/22/2018] [Indexed: 12/22/2022] Open
Abstract
Cryptococcus neoformans is an opportunistic fungus that can cause lethal brain infections in immunosuppressed individuals. Infection usually occurs via the inhalation of a spore or desiccated yeast which can then disseminate from the lung to the brain and other tissues. Dissemination and disease is largely influence by the production of copious amounts of cryptococcal polysaccharides, both which are secreted to the extracellular environment or assembled into a thick capsule surrounding the cell body. There are two important polysaccharides: glucuronoxylomannan (GXM) and galactoxylomannan, also called as glucuronoxylomanogalactan (GXMGal or GalXM). Although GXM is more abundant, GalXM has a more potent modulatory effect. In the present study, we show that GalXM is a potent activator of murine dendritic cells, and when co-cultured with T cells, induces a Th17 cytokine response. We also demonstrated that treating mice with GalXM prior to infection with C. neoformans protects from infection, and this phenomenon is dependent on IL-6 and IL-17. These findings help us understand the immune biology of capsular polysaccharides in fungal pathogenesis.
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Motaung TE. Cryptococcus neoformans mutant screening: a genome-scale's worth of function discovery. FUNGAL BIOL REV 2018. [DOI: 10.1016/j.fbr.2018.01.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Previato JO, Vinogradov E, Maes E, Fonseca LM, Guerardel Y, Oliveira PAV, Mendonça-Previato L. Distribution of the O-acetyl groups and β-galactofuranose units in galactoxylomannans of the opportunistic fungus Cryptococcus neoformans. Glycobiology 2018; 27:582-592. [PMID: 27986834 DOI: 10.1093/glycob/cww127] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 12/09/2016] [Indexed: 01/07/2023] Open
Abstract
Galactoxylomannans (GalXMs) are a mixture of neutral and acidic capsular polysaccharides produced by the opportunistic fungus Cryptococcus neoformans that exhibit potent suppressive effects on the host immune system. Previous studies describing the chemical structure of C. neoformans GalXMs have reported species without O-acetyl substituents. Herein we describe that C. neoformans grown in capsule-inducing medium produces highly O-acetylated GalXMs. The location of the O-acetyl groups was determined by nuclear magnetic resonance (NMR) spectroscopy. In the neutral GalXM (NGalXM), 80% of 3-linked mannose (α-Manp) residues present in side chains are acetylated at the O-2 position. In the acidic GalXM also termed glucuronoxylomannogalactan (GXMGal), 85% of the 3-linked α-Manp residues are acetylated either in the O-2 (75%) or in the O-6 (25%) position, but O-acetyl groups are not present at both positions simultaneously. In addition, NMR spectroscopy and methylation analysis showed that β-galactofuranose (β-Galf) units are linked to O-2 and O-3 positions of nonbranched α-galactopyranose (α-Galp) units present in the GalXMs backbone chain. These findings highlight new structural features of C. neoformans GalXMs. Among these features, the high degree of O-acetylation is of particular interest, since O-acetyl group-containing polysaccharides are known to possess a range of immunobiological activities.
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Affiliation(s)
- Jose O Previato
- Laboratório de Glicobiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941902Rio de Janeiro, Brazil
| | | | - Emmanuel Maes
- Université Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle,F 59000Lille, France
| | - Leonardo M Fonseca
- Laboratório de Glicobiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941902Rio de Janeiro, Brazil
| | - Yann Guerardel
- Université Lille, CNRS, UMR 8576, UGSF, Unité de Glycobiologie Structurale et Fonctionnelle,F 59000Lille, France
| | - Priscila A V Oliveira
- Laboratório de Glicobiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941902Rio de Janeiro, Brazil
| | - Lucia Mendonça-Previato
- Laboratório de Glicobiologia, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, 21941902Rio de Janeiro, Brazil
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5
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Bielska E, May RC. What makes Cryptococcus gattii a pathogen? FEMS Yeast Res 2015; 16:fov106. [PMID: 26614308 DOI: 10.1093/femsyr/fov106] [Citation(s) in RCA: 59] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/21/2015] [Indexed: 02/06/2023] Open
Abstract
Cryptococcosis is an invasive fungal infection of humans and other animals, typically caused by the species Cryptococcus neoformans in patients with impaired immunity. However, there is growing recognition of the importance of the related species C. gattii in causing infections in apparently immunocompetent individuals. In particular, an ongoing outbreak of cryptococcal disease in the Pacific Northwest region, which started in 1999, has driven an intense research effort into this previously neglected pathogen. Here, we discuss some of the recent discoveries in this organism from the Pacific Northwest region and highlight areas for future investigation.
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Affiliation(s)
- Ewa Bielska
- Institute of Microbiology and Infection & School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
| | - Robin C May
- Institute of Microbiology and Infection & School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK
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Park YD, Shin S, Panepinto J, Ramos J, Qiu J, Frases S, Albuquerque P, Cordero RJB, Zhang N, Himmelreich U, Beenhouwer D, Bennett JE, Casadevall A, Williamson PR. A role for LHC1 in higher order structure and complement binding of the Cryptococcus neoformans capsule. PLoS Pathog 2014; 10:e1004037. [PMID: 24789368 PMCID: PMC4006888 DOI: 10.1371/journal.ppat.1004037] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2013] [Accepted: 02/15/2014] [Indexed: 12/21/2022] Open
Abstract
Polysaccharide capsules are important virulence factors for many microbial pathogens including the opportunistic fungus Cryptococcus neoformans. In the present study, we demonstrate an unusual role for a secreted lactonohydrolase of C. neoformans, LHC1 in capsular higher order structure. Analysis of extracted capsular polysaccharide from wild-type and lhc1Δ strains by dynamic and static light scattering suggested a role for the LHC1 locus in altering the capsular polysaccharide, both reducing dimensions and altering its branching, density and solvation. These changes in the capsular structure resulted in LHC1-dependent alterations of antibody binding patterns, reductions in human and mouse complement binding and phagocytosis by the macrophage-like cell line J774, as well as increased virulence in mice. These findings identify a unique molecular mechanism for tertiary structural changes in a microbial capsule, facilitating immune evasion and virulence of a fungal pathogen. Polysaccharide capsules are important virulence factors in pathogenic microbes that provide a protective coat against host immunity. Cryptococcus neoformans is a pathogenic encapsulated yeast that is a major opportunistic infection, causing approximately 600,000 cases of meningitis per year in AIDS patients globally, and whose polysaccharide capsule is a major virulence factor. While extensive work has detailed the chemical components forming the cryptococcal capsule, the molecular events leading to the higher order assembly of the capsule, and its consequences on immune subterfuge remain unknown. In the present studies we used a proteomics method to identify a novel hydrolytic enzyme, lactonohydrolase (Lhc1) and used a variety of biophysical methods including dynamic and static light scattering as well as motility studies to show that extracted capsular polysaccharide undergoes remodeling in a LHC1-dependent fashion. This results in a more tightly compacted capsular structure that alters binding of anti-capsular antibodies and reduces binding by both human as well as mouse serum complement. Furthermore, LHC1-dependent capsular alterations serve to increase the virulence of the fungus in a mouse model, suggesting a novel role for this class of enzyme in capsular remodeling and immune evasion in microbial pathogenesis.
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Affiliation(s)
- Yoon-Dong Park
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Soowan Shin
- Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - John Panepinto
- Department of Microbiology and Immunology, University at Buffalo, the State University of New York, Buffalo, New York, United States of America
| | - Jeanie Ramos
- Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
| | - Jin Qiu
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Susana Frases
- Department of Microbiology and Immunology and Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
- Laboratorio de Ultraestrutura Cellular Hertha Meyer, Instituto de Biofisica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Patricia Albuquerque
- Department of Microbiology and Immunology and Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Radames J. B. Cordero
- Department of Microbiology and Immunology and Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Nannan Zhang
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Uwe Himmelreich
- Biomedical NMR Unit, Department of Medical Diagnostic Sciences, Division of Radiology, Katholieke Universiteit Leuven, Leuven, Belgium
| | - David Beenhouwer
- Division of Infectious Diseases, Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, California, United States of America
- Department of Medicine, David Geffen School of Medicine, University of California, Los Angeles, California, United States of America
| | - John E. Bennett
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
| | - Arturo Casadevall
- Department of Microbiology and Immunology and Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, Bronx, New York, New York, United States of America
| | - Peter R. Williamson
- Laboratory of Clinical Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America
- Section of Infectious Diseases, Department of Medicine, University of Illinois at Chicago College of Medicine, Chicago, Illinois, United States of America
- * E-mail:
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Tefsen B, Grijpstra J, Ordonez S, Lammers M, van Die I, de Cock H. Deletion of the CAP10 gene of Cryptococcus neoformans results in a pleiotropic phenotype with changes in expression of virulence factors. Res Microbiol 2014; 165:399-410. [PMID: 24751576 DOI: 10.1016/j.resmic.2014.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Accepted: 03/31/2014] [Indexed: 12/18/2022]
Abstract
The human pathogen Cryptococcus neoformans causes meningo-encephalitis. The polysaccharide capsule is an important virulence factor for this yeast-like fungus. Previously, we had shown that disruption of the CAP10 gene, encoding a putative xylosyltransferase, results in mutant cells that lack most of the capsular polysaccharides on the cell surface, but do not show a typical acapsular phenotype. In contrast to the acapsular cap59 mutant, cap10 did not induce maturation of dendritic cells when exposed to components of the immune system. In order to gain further insight into the causes of this phenotype displayed by the cap10 mutant, we performed a more in-depth phenotypic analysis of the cell wall and surface structures of this mutant compared to the wild type strain and acapsular mutant cap59. Moreover, we analyzed the cap10 mutant and the wild type strain for differential gene expression of, amongst others, enzymes that are involved in biogenesis of cell wall and capsule components. We conclude that a mutation in the CAP10 gene results in a pleiotropic phenotype with effects on different cellular processes affecting, amongst others, cell size, expression of virulence factors and size of extracellular vesicles.
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Affiliation(s)
- Boris Tefsen
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
| | - Jan Grijpstra
- Microbiology, Institute of Biomembranes, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | - Soledad Ordonez
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands; Microbiology, Institute of Biomembranes, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | - Menno Lammers
- Microbiology, Institute of Biomembranes, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
| | - Irma van Die
- Department of Molecular Cell Biology and Immunology, VU University Medical Center, van der Boechorststraat 7, 1081 BT Amsterdam, The Netherlands.
| | - Hans de Cock
- Microbiology, Institute of Biomembranes, Department of Biology, Faculty of Science, Utrecht University, Padualaan 8, 3584 CH Utrecht, The Netherlands.
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Chow SK, Smith C, MacCarthy T, Pohl MA, Bergman A, Casadevall A. Disease-enhancing antibodies improve the efficacy of bacterial toxin-neutralizing antibodies. Cell Host Microbe 2014; 13:417-28. [PMID: 23601104 DOI: 10.1016/j.chom.2013.03.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Revised: 01/14/2013] [Accepted: 02/13/2013] [Indexed: 12/25/2022]
Abstract
During infection, humoral immunity produces a polyclonal response with various immunoglobulins recognizing different epitopes within the microbe or toxin. Despite this diverse response, the biological activity of an antibody (Ab) is usually assessed by the action of a monoclonal population. We demonstrate that a combination of monoclonal antibodies (mAbs) that are individually disease enhancing or neutralizing to Bacillus anthracis protective antigen (PA), a component of anthrax toxin, results in significantly augmented protection against the toxin. This boosted protection is Fc gamma receptor (FcγR) dependent and involves the formation of stoichiometrically defined mAb-PA complexes that requires immunoglobulin bivalence and simultaneous interaction between PA and the two mAbs. The formation of these mAb-PA complexes inhibits PA oligomerization, resulting in protection. These data suggest that functional assessments of single Abs may inaccurately predict how the same Abs will operate in polyclonal preparations and imply that potentially therapeutic mAbs may be overlooked in single Ab screens.
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Affiliation(s)
- Siu-Kei Chow
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, NY 10461, USA
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Pbx proteins in Cryptococcus neoformans cell wall remodeling and capsule assembly. EUKARYOTIC CELL 2014; 13:560-71. [PMID: 24585882 DOI: 10.1128/ec.00290-13] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The cryptococcal capsule is a critical virulence factor of an important pathogen, but little is known about how it is associated with the cell or released into the environment. Two mutants lacking PBX1 and PBX2 were found to shed reduced amounts of the capsule polysaccharide glucuronoxylomannan (GXM). Nuclear magnetic resonance, composition, and physical analyses showed that the shed material was of normal mass but was slightly enriched in xylose. In contrast to previous reports, this material contained no glucose. Notably, the capsule fibers of pbxΔ mutant cells grown under capsule-inducing conditions were present at a lower than usual density and were loosely attached to the cell wall. Mutant cell walls were also defective, as indicated by phenotypes including abnormal cell morphology, reduced mating filamentation, and altered cell integrity. All observed phenotypes were shared between the two mutants and exacerbated in a double mutant. Consistent with a role in surface glycan synthesis, the Pbx proteins localized to detergent-resistant membrane domains. These results, together with the sequence motifs in the Pbx proteins, suggest that Pbx1 and Pbx2 are redundant proteins that act in remodeling the cell wall to maintain normal cell morphology and precursor availability for other glycan synthetic processes. Their absence results in aberrant cell wall growth and metabolic imbalance, which together impact cell wall and capsule synthesis, cell morphology, and capsule association. The surface changes also lead to increased engulfment by host phagocytes, consistent with the lack of virulence of pbx mutants in animal models.
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Martins LMS, de Andrade HM, Vainstein MH, Wanke B, Schrank A, Balaguez CB, dos Santos PR, Santi L, Pires SDF, da Silva AS, de Castro JAF, Brandão RMSDS, do Monte SJH. Immunoproteomics and immunoinformatics analysis of Cryptococcus gattii: novel candidate antigens for diagnosis. Future Microbiol 2013; 8:549-63. [PMID: 23534365 DOI: 10.2217/fmb.13.22] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
AIM To identify immunoreactive proteins of Cryptococcus gattii genotype VGII and their B-cell epitopes. MATERIALS & METHODS We combined 2D gel electrophoresis, immunoblotting and mass spectrometry to identify immunoreactive proteins from four strains of C. gattii genotype VGII (CG01, CG02, CG03 and R265). Next, we screened the identified proteins to map B-cell epitopes. RESULTS Sixty-eight immunoreactive proteins were identified. The strains and the number of proteins we found were: CG01 (12), CG02 (12), CG03 (18) and R265 (26). In addition, we mapped 374 peptides potentially targeted by B cells. CONCLUSION Both immunoreactive proteins and B-cell epitopes of C. gattii genotype VGII that were potentially targeted by a host humoral response were identified. Considering the evolutionary relevance of the identified proteins, we may speculate that they could be used as the initial targets for recombinant protein and peptide synthesis aimed at the development of immunodiagnostic tools for cryptococcosis.
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Affiliation(s)
- Liline Maria Soares Martins
- Laboratório de Imunogenética e Biologia Molecular, Universidade Federal do Piauí, Campus Ministro Petrônio Portella Bloco SG-16, 64049-550, Teresina, Piauí, Brazil.
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Heiss C, Skowyra ML, Liu H, Klutts JS, Wang Z, Williams M, Srikanta D, Beverley SM, Azadi P, Doering TL. Unusual galactofuranose modification of a capsule polysaccharide in the pathogenic yeast Cryptococcus neoformans. J Biol Chem 2013; 288:10994-1003. [PMID: 23408430 DOI: 10.1074/jbc.m112.441998] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Galactofuranose (Galf) is the five-membered ring form of galactose. Although it is absent from mammalian glycans, it occurs as a structural and antigenic component of important cell surface molecules in a variety of microbes, ranging from bacteria to parasites and fungi. One such organism is Cryptococcus neoformans, a pathogenic yeast that causes lethal meningoencephalitis in immunocompromised individuals, particularly AIDS patients. C. neoformans is unique among fungal pathogens in bearing a complex polysaccharide capsule, a critical virulence factor reported to include Galf. Notably, how Galf modification contributes to the structure and function of the cryptococcal capsule is not known. We have determined that Galf is β1,2-linked to an unusual tetrasubstituted galactopyranose of the glucuronoxylomannogalactan (GXMGal) capsule polysaccharide. This discovery fills a longstanding gap in our understanding of a major polymer of the cryptococcal capsule. We also engineered a C. neoformans strain that lacks UDP-galactopyranose mutase; this enzyme forms UDP-Galf, the nucleotide sugar donor required for Galf addition. Mutase activity was required for the incorporation of Galf into glucuronoxylomannogalactan but was dispensable for vegetative growth, cell integrity, and virulence in a mouse model.
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Affiliation(s)
- Christian Heiss
- Complex Carbohydrate Research Center, University of Georgia, Athens, Georgia 30602, USA
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12
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Pericolini E, Alunno A, Gabrielli E, Bartoloni E, Cenci E, Chow SK, Bistoni G, Casadevall A, Gerli R, Vecchiarelli A. The microbial capsular polysaccharide galactoxylomannan inhibits IL-17A production in circulating T cells from rheumatoid arthritis patients. PLoS One 2013; 8:e53336. [PMID: 23308194 PMCID: PMC3540098 DOI: 10.1371/journal.pone.0053336] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 11/29/2012] [Indexed: 12/18/2022] Open
Abstract
The persistence of activated T cells in rheumatoid arthritis (RA) synovium may be attributable to increased homing, increased retention or a possible imbalance between cell proliferation and programmed cell death. Induction of apoptosis may represent a potential therapeutic approach. Galactoxylomannan (GalXM) from the opportunistic fungus Cryptococcus neoformans can interact with T cells and induce T-cell apoptosis through the inhibition of CD45 phosphatase activity. The aim of this study was to determine the effect of GalXM on circulating T cells from patients with RA and the underlying mechanisms. GalXM immunomodulating effect on apoptosis and signal transduction pathway involved in IL-17A production was evaluated on T cells. RA T-cell apoptosis, higher than that of control T cells, was further increased by GalXM through induction of caspase-3 activation. Activated T cells expressing the CD45RO molecule and producing IL-17A were the main target of GalXM-induced apoptosis. GalXM induced consistent impairment of IL-17A production and inhibition of STAT3, which was hyperactivated in RA. In conclusion, GalXM triggered apoptosis of activated memory T cells and interfered with IL-17A production in RA. These data suggest therapeutic targeting of deleterious Th17 cells in RA and other autoimmune diseases.
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Affiliation(s)
- Eva Pericolini
- Microbiology Section, Department of Experimental Medicine and Biochemical Science, University of Perugia, Perugia, Italy
| | - Alessia Alunno
- Rheumatology Unit, Department of Clinical and Experimental Medicine, University of Perugia, Perugia, Italy
| | - Elena Gabrielli
- Microbiology Section, Department of Experimental Medicine and Biochemical Science, University of Perugia, Perugia, Italy
| | - Elena Bartoloni
- Rheumatology Unit, Department of Clinical and Experimental Medicine, University of Perugia, Perugia, Italy
| | - Elio Cenci
- Microbiology Section, Department of Experimental Medicine and Biochemical Science, University of Perugia, Perugia, Italy
| | - Siu-Kei Chow
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Giovanni Bistoni
- Department of Plastic and Reconstructive Surgery, “La Sapienza” Medical School, University of Rome, Rome, Italy
| | - Arturo Casadevall
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Roberto Gerli
- Rheumatology Unit, Department of Clinical and Experimental Medicine, University of Perugia, Perugia, Italy
- * E-mail:
| | - Anna Vecchiarelli
- Microbiology Section, Department of Experimental Medicine and Biochemical Science, University of Perugia, Perugia, Italy
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Abstract
The human fungal pathogen Cryptococcus neoformans is characterized by its ability to induce a distinct polysaccharide capsule in response to a number of host-specific environmental stimuli. The induction of capsule is a complex biological process encompassing regulation at multiple steps, including the biosynthesis, transport, and maintenance of the polysaccharide at the cell surface. By precisely regulating the composition of its cell surface and secreted polysaccharides, C. neoformans has developed intricate ways to establish chronic infection and dormancy in the human host. The plasticity of the capsule structure in response to various host conditions also underscores the complex relationship between host and parasite. Much of this precise regulation of capsule is achieved through the transcriptional responses of multiple conserved signaling pathways that have been coopted to regulate this C. neoformans-specific virulence-associated phenotype. This review focuses on specific host stimuli that trigger the activation of the signal transduction cascades and on the downstream transcriptional responses that are required for robust encapsulation around the cell.
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Dufresne SF, Datta K, Li X, Dadachova E, Staab JF, Patterson TF, Feldmesser M, Marr KA. Detection of urinary excreted fungal galactomannan-like antigens for diagnosis of invasive aspergillosis. PLoS One 2012; 7:e42736. [PMID: 22900046 PMCID: PMC3416763 DOI: 10.1371/journal.pone.0042736] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 07/12/2012] [Indexed: 02/06/2023] Open
Abstract
Mortality associated with invasive aspergillosis (IA) remains high, partly because of delayed diagnosis. Detection of microbial exoantigens, released in serum and other body fluids during infection, may help timely diagnosis. In course of IA, Aspergillus galactomannan (GM), a well established polysaccharide biomarker, is released in body fluids including urine. Urine is an abundant, safely collected specimen, well-suited for point-of-care (POC) testing, which could play an increasing role in screening for early disease. Our main objective was to demonstrate GM antigenuria as a clinically relevant biological phenomenon in IA and establish proof-of-concept that it could be translated to POC diagnosis. Utilizing a novel IgM monoclonal antibody (MAb476) that recognizes GM-like antigens from Aspergillus and other molds, we demonstrated antigenuria in an experimental animal IA model (guinea pig), as well as in human patients. In addition, we investigated the chemical nature of the urinary excreted antigen in human samples, characterized antigen detection in urine by immunoassays, described a putative assay inhibitor in urine, and indicated means of alleviation of the inhibition. We also designed and used a lateral flow immunochromatographic assay to detect urinary excreted antigen in a limited number of IA patient urine samples. In this study, we establish that POC diagnosis of IA based on urinary GM detection is feasible. Prospective studies will be necessary to establish the performance characteristics of an optimized device and define its optimal clinical use.
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Affiliation(s)
- Simon F. Dufresne
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Département de Microbiologie et Immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Kausik Datta
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Xinming Li
- Albert Einstein College of Medicine, Bronx, New York, United States of America
- China Medical University, Shenyang, People's Republic of China
| | - Ekaterina Dadachova
- Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Janet F. Staab
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Thomas F. Patterson
- University of Texas Health Science Center and South Texas Veterans Healthcare System, San Antonio, Texas, United States of America
| | - Marta Feldmesser
- Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Kieren A. Marr
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America
- * E-mail:
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15
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Sabiiti W, May RC. Capsule independent uptake of the fungal pathogen Cryptococcus neoformans into brain microvascular endothelial cells. PLoS One 2012; 7:e35455. [PMID: 22530025 PMCID: PMC3328471 DOI: 10.1371/journal.pone.0035455] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2011] [Accepted: 03/17/2012] [Indexed: 01/11/2023] Open
Abstract
Cryptococcosis is a life-threatening fungal disease with a high rate of mortality among HIV/AIDS patients across the world. The ability to penetrate the blood-brain barrier (BBB) is central to the pathogenesis of cryptococcosis, but the way in which this occurs remains unclear. Here we use both mouse and human brain derived endothelial cells (bEnd3 and hCMEC/D3) to accurately quantify fungal uptake and survival within brain endothelial cells. Our data indicate that the adherence and internalisation of cryptococci by brain microvascular endothelial cells is an infrequent event involving small numbers of cryptococcal yeast cells. Interestingly, this process requires neither active signalling from the fungus nor the presence of the fungal capsule. Thus entry into brain microvascular endothelial cells is most likely a passive event that occurs following ‘trapping’ within capillary beds of the BBB.
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Affiliation(s)
- Wilber Sabiiti
- Institute of Microbiology & Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Robin C. May
- Institute of Microbiology & Infection, School of Biosciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, United Kingdom
- * E-mail:
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16
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Chronological aging is associated with biophysical and chemical changes in the capsule of Cryptococcus neoformans. Infect Immun 2011; 79:4990-5000. [PMID: 21968999 DOI: 10.1128/iai.05789-11] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Does the age of a microbial cell affect its virulence factors? To our knowledge, this question has not been addressed previously, but the answer is of great relevance for chronic infections where microbial cells persist and age in hosts. Cryptococcus neoformans is an encapsulated human-pathogenic fungus notorious for causing chronic infections where cells of variable age persist in tissue. The major virulence factor for C. neoformans is a polysaccharide (PS) capsule. To understand how chronological age could impact the cryptococcal capsule properties, we compared the elastic properties, permeabilities, zeta potentials, and glycosidic compositions of capsules from young and old cells and found significant differences in all parameters measured. Changes in capsular properties were paralleled by changes in PS molecular mass and density, as well as modified antigenic density and antiphagocytic properties. Remarkably, chronological aging under stationary-phase growth conditions was associated with the expression of α-1,3-glucans in the capsule, indicating a new structural capsular component. Our results establish that cryptococcal capsules are highly dynamic structures that change dramatically with chronological aging under prolonged stationary-phase growth conditions. Changes associated with cellular aging in chronic infections could contribute to the remarkable capacity of this fungus to persist in tissues by generating phenotypically and antigenically different capsules.
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17
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Kumar P, Yang M, Haynes BC, Skowyra ML, Doering TL. Emerging themes in cryptococcal capsule synthesis. Curr Opin Struct Biol 2011; 21:597-602. [PMID: 21889889 DOI: 10.1016/j.sbi.2011.08.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2011] [Revised: 08/01/2011] [Accepted: 08/08/2011] [Indexed: 12/21/2022]
Abstract
Cryptococcus neoformans, a basidiomycete yeast and opportunistic pathogen, expends significant biosynthetic effort on construction of a polysaccharide capsule with a radius that may be many times that of the cell. Beyond posing a stimulating challenge in terms of defining biosynthetic pathways, the capsule is required for this yeast to cause fatal disease. This combination has focused the attention of researchers on this system. Here we briefly review two aspects of the rapidly advancing field of capsule synthesis: the extensive variation that occurs in capsule polymers and the regulation of capsule biosynthesis.
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Affiliation(s)
- Pardeep Kumar
- Department of Molecular Microbiology, Washington University Medical School, St. Louis, MO 63110, USA
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18
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Vecchiarelli A, Pericolini E, Gabrielli E, Chow SK, Bistoni F, Cenci E, Casadevall A. Cryptococcus neoformans galactoxylomannan is a potent negative immunomodulator, inspiring new approaches in anti-inflammatory immunotherapy. Immunotherapy 2011; 3:997-1005. [DOI: 10.2217/imt.11.86] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen responsible for life-threatening infections in immunocompromised individuals and occasionally in those with no known immune impairment. The fungus is endowed with several virulence factors, including capsular polysaccharides that play a key role in virulence. The capsule is composed of 90–95% glucuronoxylomannan (GXM), 5–8% galactoxylomannan (GalXM) and <1% mannoproteins. Capsular polysaccharides are shed into tissue where they produce many deleterious effects. Since GalXM has a smaller molecular mass, the molar concentration of GalXM in polysaccharide that is shed could exceed that of GXM in C. neoformans exopolysaccharides. Moreover, GalXM exhibits a number of unusual biologic properties both in vitro and in vivo. Here, we summarize the principal immunomodulatory effects of GalXM described during the last 20 years, particularly the mechanisms leading to induction of apoptosis in T lymphocytes, B lymphocytes and macrophages. Since the capacity of GalXM to induce widespread immune suppression is believed to contribute to the virulence of C. neoformans, this property might be exploited therapeutically to dampen the aberrant activation of immune cells during autoimmune disorders.
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Affiliation(s)
| | - Eva Pericolini
- Microbiology Section, Department of Experimental Medicine & Biochemical Sciences, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
| | - Elena Gabrielli
- Microbiology Section, Department of Experimental Medicine & Biochemical Sciences, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
| | - Siu-Kei Chow
- Department of Microbiology & Immunology of the Albert Einstein College of Medicine, Bronx, NY, USA
| | - Francesco Bistoni
- Microbiology Section, Department of Experimental Medicine & Biochemical Sciences, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
| | - Elio Cenci
- Microbiology Section, Department of Experimental Medicine & Biochemical Sciences, University of Perugia, Via del Giochetto, 06126 Perugia, Italy
| | - Arturo Casadevall
- Department of Microbiology & Immunology of the Albert Einstein College of Medicine, Bronx, NY, USA
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19
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Chow SK, Casadevall A. Evaluation of Cryptococcus neoformans galactoxylomannan-protein conjugate as vaccine candidate against murine cryptococcosis. Vaccine 2011; 29:1891-8. [PMID: 21238568 DOI: 10.1016/j.vaccine.2010.12.134] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2010] [Revised: 12/19/2010] [Accepted: 12/26/2010] [Indexed: 11/28/2022]
Abstract
Galactoxylomannan (GalXM) is a complex polysaccharide produced by the human pathogenic fungus Cryptococcus neoformans that mediates profound immunological derangements in murine models. GalXM is essentially non-immunogenic and produces immune paralysis in mice. Previous studies have attempted to enhance immunogenicity by conjugating GalXM to a protein carrier, but only transient antibody responses were elicited. Here we report the generation of two GalXM conjugates with bovine serum albumin (BSA) and protective antigen (PA) of Bacillus anthracis, respectively, using 1-cyano-4-dimethylaminopyridinium tetrafluoroborate (CDAP) as the cyanylating reagent. Both conjugates induced potent and sustained antibody responses as detected by both cross antigen-based and CovaLink direct ELISAs. We confirmed the specificity of the response to GalXM by inhibition ELISA and immunofluorescence. The isotype composition analysis revealed that IgG and IgM were abundant in the immune sera against GalXM, consistent with the induction of a T cell-dependent response. IgG1 was the predominant IgG subclass against GalXM, while immunization with Quil A as adjuvant elicited a significantly higher production of IgG2a than with Freund's adjuvant. Immune sera were not opsonic for C. neoformans and there was no survival difference between immune and non-immune mice challenged with C. neoformans. These results demonstrated the effectiveness of the GalXM-protein conjugate to induce robust immune responses although no evidence was obtained that such responses contributed to host defense.
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Affiliation(s)
- Siu-Kei Chow
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, 1300 Morris Park Ave., Bronx, NY 10461, USA
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20
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Cordero RJB, Frases S, Guimaräes AJ, Rivera J, Casadevall A. Evidence for branching in cryptococcal capsular polysaccharides and consequences on its biological activity. Mol Microbiol 2011; 79:1101-17. [PMID: 21208301 DOI: 10.1111/j.1365-2958.2010.07511.x] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The encapsulated fungus Cryptococcus neoformans is a common cause of life-threatening disease in immunocompromised individuals. Its major virulence determinant is the polysaccharide (PS) capsule. An unsolved problem in cryptococcal biology is whether the PSs composing the capsule are linear or complex branched polymers, as well as the implications of this structural composition in pathogenesis. In this study we approached the problem by combining static and dynamic light scattering, viscosity analysis, and high-resolution microscopy and correlated the findings with biological properties. Analysis of the dependence of capsular PS molecular mass and the radius of gyration provided strong evidence against a simple linear PS configuration. Shape factors calculated from light scattering measurements in solution revealed values consistent with polymer branching. Furthermore, viscosity measurements provided complementary evidence for structural branching. Electron microscopy showed PS spherical-like structures similar to other branched PS. Finally, we show that the capacity of capsular PS to interfere in complement-mediated phagocytosis, inhibit nitric oxide production by macrophage-like cells, protect against reactive oxygen species, antibody reactivity and half-life in serum were influenced by the degree of branching, providing evidence for the notion that PS branching is an important parameter in determining the biological activity of C. neoformans PS.
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Affiliation(s)
- Radames J B Cordero
- Department of Microbiology and Immunology, Albert Einstein College of Medicine of Yeshiva University, Bronx, NY, USA
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21
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Current awareness on yeast. Yeast 2010. [DOI: 10.1002/yea.1724] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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22
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Jesus MD, Nicola AM, Chow SK, Lee IR, Nong S, Specht CA, Levitz SM, Casadevall A. Glucuronoxylomannan, galactoxylomannan, and mannoprotein occupy spatially separate and discrete regions in the capsule of Cryptococcus neoformans. Virulence 2010; 1:500-8. [PMID: 21178496 DOI: 10.4161/viru.1.6.13451] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The capsular polysaccharides of Cryptococcus neoformans have historically been divided into three components namely, glucuronoxylomannan (GXM), galactoxylomannan (GalXM), and mannoprotein (MP) but their relative spatial-geographical relationship in the capsule is unknown. To explore this problem would require the capacity for visualizing these components in the capsule. Prior studies have reported serological reagents to GXM and GalXM but no antibodies are available against MPs. Consequently, we immunized Balb/c mice with C. neoformans recombinant mannoprotein 98 and recovered twelve monoclonal antibodies (mAbs) of which one, an IgG2a designated 18F2, bound to intact cells by immunofluorescence. mAb 18F2 bound to the cell wall surface in acapsular and encapsulated cells. Using mAb 18F2 and previously generated antibodies to GXM and GalXM we have established the localization of three capsular components GXM, GalXM and one type of mannoprotein, MP98 on the C. neoformans cell. The results show that MP98, like GalXM, is found near the cell wall and this information allows us to begin to discern the geography of the cryptococcal capsule.
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Affiliation(s)
- Magdia De Jesus
- Department of Microbiology & Immunology, Albert Einstein College of Medicine, Bronx, NY, USA
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23
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Pericolini E, Gabrielli E, Bistoni G, Cenci E, Perito S, Chow SK, Riuzzi F, Donato R, Casadevall A, Vecchiarelli A. Role of CD45 signaling pathway in galactoxylomannan-induced T cell damage. PLoS One 2010; 5:e12720. [PMID: 20856869 PMCID: PMC2939064 DOI: 10.1371/journal.pone.0012720] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Accepted: 08/20/2010] [Indexed: 11/19/2022] Open
Abstract
Previously, we reported that Galactoxylomannan (GalXM) activates the extrinsic and intrinsic apoptotic pathways through an interaction with the glycoreceptors on T cells. In this study we establish the role of the glycoreceptor CD45 in GalXM-induced T cell apoptosis, using CD45(+/+) and CD45(-/-) cell lines, derived from BW5147 murine T cell lymphoma. Our results show that whereas CD45 expression is not required for GalXM association by the cells, it is essential for apoptosis induction. In CD45(+/+) cells, CD45 triggering by GalXM reduces the activation of Lck, ZAP70 and Erk1/2. Conversely, in CD45(-/-) cells, Lck was hyperphosphorylated and did not show any modulation after GalXM stimulation. On the whole, our findings provide evidence that the negative regulation of Lck activation occurs via CD45 engagement. This appears to be related to the capacity of GalXM to antagonize T cell activation and induce T cell death. Overall this mechanism may be responsible for the immune paralysis that follows GalXM administration and could explain the powerful immunosuppression that accompanies cryptococcosis.
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Affiliation(s)
- Eva Pericolini
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Elena Gabrielli
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Giovanni Bistoni
- Department of Plastic and Reconstructive Surgery, University of Rome “La Sapienza” Medical School, Rome, Italy
| | - Elio Cenci
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Stefano Perito
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Siu-Kei Chow
- Department of Microbiology and Immunology of the Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Francesca Riuzzi
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Rosario Donato
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
| | - Arturo Casadevall
- Department of Microbiology and Immunology of the Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Anna Vecchiarelli
- Microbiology and Anatomy Sections, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy
- * E-mail:
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24
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Immunomodulatory effects of serotype B glucuronoxylomannan from Cryptococcus gattii correlate with polysaccharide diameter. Infect Immun 2010; 78:3861-70. [PMID: 20547742 DOI: 10.1128/iai.00111-10] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Glucuronoxylomannan (GXM), the major capsular component in the Cryptococcus complex, interacts with the immune system in multiple ways, which include the activation of Toll-like receptors (TLRs) and the modulation of nitric oxide (NO) production by phagocytes. In this study, we analyzed several structural parameters of GXM samples from Cryptococcus neoformans (serotypes A and D) and Cryptococcus gattii (serotypes B and C) and correlated them with the production of NO by phagocytes and the activation of TLRs. GXM fractions were differentially recognized by TLR2/TLR1 (TLR2/1) and TLR2/6 heterodimers expressed on TLR-transfected HEK293A cells. Higher NF-kappaB luciferase reporter activity induced by GXM was observed in cells expressing TLR2/1 than in cells transfected with TLR2/6 constructs. A serotype B GXM from C. gattii was the most effective polysaccharide fraction activating the TLR-mediated response. This serotype B polysaccharide, which was also highly efficient at eliciting the production of NO by macrophages, was similar to the other GXM samples in monosaccharide composition, zeta potential, and electrophoretic mobility. However, immunofluorescence with four different monoclonal antibodies and dynamic light-scattering analysis revealed that the serotype B GXM showed particularities in serological reactivity and had the smallest effective diameter among the GXM samples analyzed in this study. Fractionation of additional serotype B GXMs, followed by exposure of these fractions to macrophages, revealed a correlation between NO production and reduced effective diameters. Our results demonstrate a great functional diversity in GXM samples from different isolates and establish their abilities to differentially activate cellular responses. We propose that serological properties as well as physical chemical parameters, such as the diameter of polysaccharide molecules, may potentially influence the inflammatory response against Cryptococcus spp. and may contribute to the differences in granulomatous inflammation between cryptococcal species.
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