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Crawford C, Guazzelli L, McConnell SA, McCabe O, d’Errico C, Greengo SD, Wear MP, Jedlicka AE, Casadevall A, Oscarson S. Synthetic Glycans Reveal Determinants of Antibody Functional Efficacy against a Fungal Pathogen. ACS Infect Dis 2024; 10:475-488. [PMID: 37856427 PMCID: PMC10862557 DOI: 10.1021/acsinfecdis.3c00447] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2023] [Indexed: 10/21/2023]
Abstract
Antibodies play a vital role in the immune response to infectious diseases and can be administered passively to protect patients. In the case of Cryptococcus neoformans, a WHO critical priority fungal pathogen, infection results in antibodies targeting capsular glucuronoxylomannan (GXM). These antibodies yield protective, non-protective, and disease-enhancing outcomes when administered passively. However, it was unknown how these distinct antibodies recognized their antigens at the molecular level, leading to the hypothesis that they may target different GXM epitopes. To test this hypothesis, we constructed a microarray containing 26 glycans representative of those found in highly virulent cryptococcal strains and utilized it to study 16 well-characterized monoclonal antibodies. Notably, we found that protective and non-protective antibodies shared conserved reactivity to the M2 motif of GXM, irrespective of the strain used in infection or GXM-isolated to produce a conjugate vaccine. Here, only two antibodies, 12A1 and 18B7, exhibited diverse trivalent GXM motif reactivity. IgG antibodies associated with protective responses showed cross-reactivity to at least two GXM motifs. This molecular understanding of antibody binding epitopes was used to map the antigenic diversity of two Cryptococcus neoformans strains, which revealed the exceptional complexity of fungal capsular polysaccharides. A multi-GXM motif vaccine holds the potential to effectively address this antigenic diversity. Collectively, these findings underscore the context-dependent nature of antibody function and challenge the classification of anti-GXM epitopes as either "protective" or "non-protective".
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Affiliation(s)
- Conor
J. Crawford
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Lorenzo Guazzelli
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Scott A. McConnell
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Orla McCabe
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Clotilde d’Errico
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
| | - Seth D. Greengo
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Maggie P. Wear
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Anne E. Jedlicka
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Arturo Casadevall
- Department
of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, 615 North Wolfe Street, Baltimore, Maryland 21205, United States
| | - Stefan Oscarson
- Centre
for Synthesis and Chemical Biology, University
College Dublin, Belfield D04 V1W8, Dublin 4, Ireland
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2
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Hommel B, Sturny-Leclère A, Alanio A. In Vitro Titan Cell Generation in Cryptococcus neoformans and Automated Cell Size Measurements. Methods Mol Biol 2024; 2775:385-391. [PMID: 38758332 DOI: 10.1007/978-1-0716-3722-7_26] [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
A special feature of the human fungal pathogen Cryptococcus neoformans is its morphological changes triggered by the interaction with the host. During infection, a specific increase in cell size is observed, particularly in lung tissue, from a typical cell size of 5-7 μm cells to cells larger than 10 μm, dubbed titan cells (TCs). However, the study of this specific cell subpopulation was, until now, only possible via recovery of TCs from lungs of mice during experimental infections where stable and reproducible generation of TCs occurs.The protocol described here generates TCs using in vitro conditions and measures cell size using a rapid, automated method. TC generation in vitro is robust and reproducible, generating yeast cells harboring the same characteristics of TCs generated in vivo.
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Affiliation(s)
- Benjamin Hommel
- Translational Mycology Research Group, Institut Pasteur, Université Paris Cité, Centre National de Référence Mycoses Invasives et Antifongiques, Département de Mycologie, Paris, France
| | - Aude Sturny-Leclère
- Institut Pasteur, Université Paris Cité,National Reference Center for Invasive Mycoses and Antifungals, Paris, France
| | - Alexandre Alanio
- Translational Mycology Research Group, Institut Pasteur, Université Paris Cité, Centre National de Référence Mycoses Invasives et Antifongiques, Département de Mycologie, Paris, France.
- Laboratoire de parasitologie-mycologie, AP-HP, Hôpital Saint-Louis, Paris, France.
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3
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Zhao X, Shen L, Zheng J, Zhu H, Li L, Shi H, Chen Z, Li Q. C1q Confers Protection Against Cryptococcal Lung Infection by Alleviating Inflammation and Reducing Cryptococcal Virulence. Open Forum Infect Dis 2023; 10:ofad151. [PMID: 37089772 PMCID: PMC10117377 DOI: 10.1093/ofid/ofad151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Accepted: 03/20/2023] [Indexed: 04/25/2023] Open
Abstract
Background To define the role of C1qa in host defense against Cryptococcus neoformans lung infection, we investigated its susceptibility to cryptococcal lung infection in mice deficient in complement factor C1qa (C1qa-/- ). Methods We established a wild-type (WT) and C1qa-deficient murine inhalation model with C. neoformans. We compared the host survival rate, inflammatory responses, and pathogenicity of C. neoformans during the infection course between WT and C1qa-/- mice. Results The mortality rate of C1qa-deficient mice was significantly higher than that of wild-type mice. The increased formation of Titan cells in the lungs was associated with augmented inflammation in C1qa-deficient mice. The capacity of lung homogenate supernatant from C1qa-deficient mice to induce Titan formation in vitro was greater compared with that of wild-type mice. The C. neoformans isolated from the lungs of infected C1qa-deficient mice was more resistant to macrophage killing in vitro and caused significantly higher mortality after administration to mice compared with that isolated from WT mice. Conclusions These findings reveal a novel role of C1qa in host defense against C. neoformans infection by regulating host inflammation and pathogen virulence and provide new insight into the C1q-mediated lung environment underlying the transition from yeast to Titan cell.
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Affiliation(s)
| | | | | | - Haiyan Zhu
- Department of Biological Medicines & Shanghai Engineering Research Center of ImmunoTherapeutics, School of Pharmacy, Fudan University, Shanghai, China
| | - Li Li
- Laboratory of Mycology, Department of Dermatology, Huashan Hospital, Fudan University, Shanghai, China
| | - Hong Shi
- Department of Anesthesiology, Shanghai Pulmonary Hospital, School of Medicine, Tongji University, Shanghai, China
| | - Zhongqing Chen
- Correspondence: Zhongqing Chen, MD, PhD, Department of Pathology, Huashan Hospital, Fudan University, 12 Wulumuqi Zhong Road, Shanghai, 200040, China (); Qian Li, Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Fudan University, 12 Wulumuqi Zhong Road, Shanghai, 200040, China ()
| | - Qian Li
- Correspondence: Zhongqing Chen, MD, PhD, Department of Pathology, Huashan Hospital, Fudan University, 12 Wulumuqi Zhong Road, Shanghai, 200040, China (); Qian Li, Department of Infectious Diseases, Shanghai Key Laboratory of Infectious Diseases and Biosafety Emergency Response, National Medical Center for Infectious Diseases, Huashan Hospital, Fudan University, 12 Wulumuqi Zhong Road, Shanghai, 200040, China ()
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4
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Jackson KM, Ding M, Nielsen K. Importance of Clinical Isolates in Cryptococcus neoformans Research. J Fungi (Basel) 2023; 9:364. [PMID: 36983532 PMCID: PMC10056780 DOI: 10.3390/jof9030364] [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: 02/20/2023] [Revised: 03/09/2023] [Accepted: 03/13/2023] [Indexed: 03/19/2023] Open
Abstract
The human pathogenic fungus Cryptococcus neoformans is a global health concern. Previous research in the field has focused on studies using reference strains to identify virulence factors, generate mutant libraries, define genomic structures, and perform functional studies. In this review, we discuss the benefits and drawbacks of using reference strains to study C. neoformans, describe how the study of clinical isolates has expanded our understanding of pathogenesis, and highlight how studies using clinical isolates can further develop our understanding of the host-pathogen interaction during C. neoformans infection.
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Affiliation(s)
| | | | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN 55455, USA
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5
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Firacative C, Zuluaga-Puerto N, Guevara J. Cryptococcus neoformans Causing Meningoencephalitis in Adults and a Child from Lima, Peru: Genotypic Diversity and Antifungal Susceptibility. J Fungi (Basel) 2022; 8:jof8121306. [PMID: 36547639 PMCID: PMC9781953 DOI: 10.3390/jof8121306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2022] [Revised: 12/13/2022] [Accepted: 12/13/2022] [Indexed: 12/23/2022] Open
Abstract
Cryptococcosis, caused predominantly by Cryptococcus neoformans, is a potentially fatal, opportunistic infection that commonly affects the central nervous system of immunocompromised patients. Globally, this mycosis is responsible for almost 20% of AIDS-related deaths, and in countries like Peru, its incidence remains high, mostly due to the annual increase in new cases of HIV infection. This study aimed to establish the genotypic diversity and antifungal susceptibility of C. neoformans isolates causing meningoencephalitis in 25 adults and a 9-year-old girl with HIV and other risk factors from Lima, Peru. To identify the genotype of the isolates, multilocus sequence typing was applied, and to establish the susceptibility of the isolates to six antifungals, a YeastOne® broth microdilution was used. From the isolates, 19 were identified as molecular type VNI, and seven as VNII, grouped in eight and three sequence types, respectively, which shows that the studied population was highly diverse. Most isolates were susceptible to all antifungals tested. However, VNI isolates were less susceptible to fluconazole, itraconazole and voriconazole than VNII isolates (p < 0.05). This study contributes data on the molecular epidemiology and the antifungal susceptibility profile of the most common etiological agent of cryptococcosis, highlighting a pediatric case, something which is rare among cryptococcal infection.
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Affiliation(s)
- Carolina Firacative
- Studies in Translational Microbiology and Emerging Diseases (MICROS) Research Group, School of Medicine and Health Sciences, Universidad de Rosario, Bogota 111221, Colombia
- Correspondence:
| | | | - José Guevara
- Facultad de Medicina “San Fernando”, Universidad Nacional Mayor de San Marcos, Lima 15081, Peru
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6
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Liporagi Lopes LC, Korangath P, dos Santos SR, Gabrielson KL, Ivkov R, Casadevall A. Bionized Nanoferrite Particles Alter the Course of Experimental Cryptococcus neoformans Pneumonia. Antimicrob Agents Chemother 2022; 66:e0239921. [PMID: 35293784 PMCID: PMC9017294 DOI: 10.1128/aac.02399-21] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 02/12/2022] [Indexed: 01/09/2023] Open
Abstract
Cryptococcosis is a devastating fungal disease associated with high morbidity and mortality even when treated with antifungal drugs. Bionized nanoferrite (BNF) nanoparticles are powerful immunomodulators, but their efficacy for infectious diseases has not been investigated. Administration of BNF nanoparticles to mice with experimental cryptococcal pneumonia altered the outcome of infection in a dose response manner as measured by CFU and survival. The protective effects were higher at lower doses, with reductions in IL-2, IL-4, and TNF-α, consistent with immune modulation whereby reductions in inflammation translate into reduced host damage, clearance of infection, and longer survival.
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Affiliation(s)
- Livia C. Liporagi Lopes
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Departamento de Análises Clínicas e Toxicológicas, Faculdade de Farmácia, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| | - Preethi Korangath
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Samuel R. dos Santos
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
- Departamento de Microbiologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, São Paulo, Brazil
| | - Kathleen L. Gabrielson
- Department of Molecular and Comparative Pathobiology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Robert Ivkov
- Department of Radiation Oncology and Molecular Radiation Sciences, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Mechanical Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland, USA
- Department of Materials Science and Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland, USA
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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7
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Sun S, Roth C, Floyd Averette A, Magwene PM, Heitman J. Epistatic genetic interactions govern morphogenesis during sexual reproduction and infection in a global human fungal pathogen. Proc Natl Acad Sci U S A 2022; 119:e2122293119. [PMID: 35169080 PMCID: PMC8872808 DOI: 10.1073/pnas.2122293119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 01/11/2022] [Indexed: 12/12/2022] Open
Abstract
Cellular development is orchestrated by evolutionarily conserved signaling pathways, which are often pleiotropic and involve intra- and interpathway epistatic interactions that form intricate, complex regulatory networks. Cryptococcus species are a group of closely related human fungal pathogens that grow as yeasts yet transition to hyphae during sexual reproduction. Additionally, during infection they can form large, polyploid titan cells that evade immunity and develop drug resistance. Multiple known signaling pathways regulate cellular development, yet how these are coordinated and interact with genetic variation is less well understood. Here, we conducted quantitative trait locus (QTL) analyses of a mapping population generated by sexual reproduction of two parents, only one of which is unisexually fertile. We observed transgressive segregation of the unisexual phenotype among progeny, as well as a large-cell phenotype under mating-inducing conditions. These large-cell progeny were found to produce titan cells both in vitro and in infected animals. Two major QTLs and corresponding quantitative trait genes (QTGs) were identified: RIC8 (encoding a guanine-exchange factor) and CNC06490 (encoding a putative Rho-GTPase activator), both involved in G protein signaling. The two QTGs interact epistatically with each other and with the mating-type locus in phenotypic determination. These findings provide insights into the complex genetics of morphogenesis during unisexual reproduction and pathogenic titan cell formation and illustrate how QTL analysis can be applied to identify epistasis between genes. This study shows that phenotypic outcomes are influenced by the genetic background upon which mutations arise, implicating dynamic, complex genotype-to-phenotype landscapes in fungal pathogens and beyond.
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Affiliation(s)
- Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710
| | - Cullen Roth
- Department of Biology, Duke University, Durham, NC 27708
| | - Anna Floyd Averette
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710
| | - Paul M Magwene
- Department of Biology, Duke University, Durham, NC 27708
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710;
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8
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Ding M, Smith KD, Wiesner DL, Nielsen JN, Jackson KM, Nielsen K. Use of Clinical Isolates to Establish Criteria for a Mouse Model of Latent Cryptococcus neoformans Infection. Front Cell Infect Microbiol 2022; 11:804059. [PMID: 35186781 PMCID: PMC8847453 DOI: 10.3389/fcimb.2021.804059] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2021] [Accepted: 12/10/2021] [Indexed: 12/15/2022] Open
Abstract
The mechanisms of latency in the context of C. neoformans infection remain poorly understood. Two reasons for this gap in knowledge are: 1) the lack of standardized criteria for defining latent cryptococcosis in animal models and 2) limited genetic and immunological tools available for studying host parameters against C. neoformans in non-murine models of persistent infection. In this study, we defined criteria required for latency in C. neoformans infection models and used these criteria to develop a murine model of persistent C. neoformans infection using clinical isolates. We analyzed infections with two clinical C. neoformans strains, UgCl223 and UgCl552, isolated from advanced HIV patients with cryptococcal meningitis. Our data show that the majority of C57BL/6 mice infected with the clinical C. neoformans isolates had persistent, stable infections with low fungal burden, survived beyond 90 days-post infection, exhibited weight gain, had no clinical signs of disease, and had yeast cells contained within pulmonary granulomas with no generalized alveolar inflammation. Infected mice exhibited stable relative frequencies of pulmonary immune cells during the course of the infection. Upon CD4+ T-cell depletion, the CD4DTR mice had significantly increased lung and brain fungal burden that resulted in lethal infection, indicating that CD4+ T-cells are important for control of the pulmonary infection and to prevent dissemination. Cells expressing the Tbet transcription factor were the predominant activated CD4 T-cell subset in the lungs during the latent infection. These Tbet-expressing T-cells had decreased IFNγ production, which may have implications in the capacity of the cells to orchestrate the pulmonary immune response. Altogether, these results indicate that clinical C. neoformans isolates can establish a persistent controlled infection that meets most criteria for latency; highlighting the utility of this new mouse model system for studies of host immune responses that control C. neoformans infections.
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Affiliation(s)
- Minna Ding
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, United States
| | - Kyle D. Smith
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, United States
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis, MN, United States
| | - Darin L. Wiesner
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, United States
- Department of Medicine, Center for Immunity and Inflammation, Rutgers New Jersey Medical School, Newark, NJ, United States
| | - Judith N. Nielsen
- Department of Pathology and Laboratory Medicine, University of North Carolina, Chapel Hill, NC, United States
| | - Katrina M. Jackson
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, United States
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, MN, United States
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9
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Reis RS, Bonna ICF, Antonio IMDS, Pereira SA, do Nascimento CRS, Ferraris FK, Brito-Santos F, Ferreira Gremião ID, Trilles L. Cryptococcus neoformans VNII as the Main Cause of Cryptococcosis in Domestic Cats from Rio de Janeiro, Brazil. J Fungi (Basel) 2021; 7:jof7110980. [PMID: 34829267 PMCID: PMC8621350 DOI: 10.3390/jof7110980] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2021] [Revised: 10/25/2021] [Accepted: 10/26/2021] [Indexed: 11/16/2022] Open
Abstract
Cryptococcosis is a systemic fungal disease acquired from contaminated environments with propagules of the basidiomycetous yeasts of the Cryptococcus neoformans and C. gattii species complexes. The C. neoformans species complex classically comprises four major molecular types (VNI, VNII, VNIII, and VNIV), and the C. gattii species complex comprises another four (VGI, VGII, VGIII, and VGIV) and the newly identified molecular type VGV. These major molecular types differ in their epidemiological and ecological features, clinical presentations, and therapeutic outcomes. Generally, the most common isolated types are VNI, VGI, and VGII. The epidemiological profile of cryptococcosis in domestic cats is poorly studied and cats can be the sentinels for human infections. Therefore, the present study aimed to determine the molecular characterization of Cryptococcus spp. isolated from domestic cats and their dwellings in the metropolitan area of Rio de Janeiro, Brazil. A total of 36 Cryptococcus spp. strains, both clinical and environmental, from 19 cats were subtyped using multilocus sequence typing (MLST). The ploidy was identified using flow cytometry and the mating type was determined through amplification with specific pheromone primers. All strains were mating type alpha and 6/36 were diploid (all VNII). Most isolates (63.88%) were identified as VNII, a rare molecular type, leading to the consideration that this genotype is more likely related to skin lesions, since there was a high percentage (68.75%) of cats with skin lesions, which is also considered rare. Further studies regarding the molecular epidemiology of cryptococcosis in felines are still needed to clarify the reason for the large proportion of the rare molecular type VNII causing infections in cats.
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Affiliation(s)
- Rosani Santos Reis
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases (INI), Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro 21040-900, Brazil; (R.S.R.); (I.C.F.B.); (F.B.-S.)
| | - Isabel Cristina Fábregas Bonna
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases (INI), Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro 21040-900, Brazil; (R.S.R.); (I.C.F.B.); (F.B.-S.)
| | - Isabela Maria da Silva Antonio
- Laboratory of Clinical Research on Dermatozoonoses in Domestic Animals (Lapclin-Dermzoo)/INI/Fiocruz, Rio de Janeiro 21040-900, Brazil; (I.M.d.S.A.); (S.A.P.); (I.D.F.G.)
| | - Sandro Antonio Pereira
- Laboratory of Clinical Research on Dermatozoonoses in Domestic Animals (Lapclin-Dermzoo)/INI/Fiocruz, Rio de Janeiro 21040-900, Brazil; (I.M.d.S.A.); (S.A.P.); (I.D.F.G.)
| | | | - Fausto Klabund Ferraris
- Pharmacology Laboratory/INCQS/Fiocruz. Av. Brasil, 4365, Manguinhos, Rio de Janeiro 21040-900, Brazil;
| | - Fábio Brito-Santos
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases (INI), Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro 21040-900, Brazil; (R.S.R.); (I.C.F.B.); (F.B.-S.)
| | - Isabella Dib Ferreira Gremião
- Laboratory of Clinical Research on Dermatozoonoses in Domestic Animals (Lapclin-Dermzoo)/INI/Fiocruz, Rio de Janeiro 21040-900, Brazil; (I.M.d.S.A.); (S.A.P.); (I.D.F.G.)
| | - Luciana Trilles
- Mycology Laboratory, Evandro Chagas National Institute of Infectious Diseases (INI), Oswaldo Cruz Foundation (Fiocruz), Rio de Janeiro 21040-900, Brazil; (R.S.R.); (I.C.F.B.); (F.B.-S.)
- Correspondence:
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10
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Rácz HV, Mukhtar F, Imre A, Rádai Z, Gombert AK, Rátonyi T, Nagy J, Pócsi I, Pfliegler WP. How to characterize a strain? Clonal heterogeneity in industrial Saccharomyces influences both phenotypes and heterogeneity in phenotypes. Yeast 2021; 38:453-470. [PMID: 33844327 DOI: 10.1002/yea.3562] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Revised: 03/15/2021] [Accepted: 04/01/2021] [Indexed: 12/15/2022] Open
Abstract
Populations of microbes are constantly evolving heterogeneity that selection acts upon, yet heterogeneity is nontrivial to assess methodologically. The necessary practice of isolating single-cell colonies and thus subclone lineages for establishing, transferring, and using a strain results in single-cell bottlenecks with a generally neglected effect on the characteristics of the strain itself. Here, we present evidence that various subclone lineages for industrial yeasts sequenced for recent genomic studies show considerable differences, ranging from loss of heterozygosity to aneuploidies. Subsequently, we assessed whether phenotypic heterogeneity is also observable in industrial yeast, by individually testing subclone lineages obtained from products. Phenotyping of industrial yeast samples and their newly isolated subclones showed that single-cell bottlenecks during isolation can indeed considerably influence the observable phenotype. Next, we decoupled fitness distributions on the level of individual cells from clonal interference by plating single-cell colonies and quantifying colony area distributions. We describe and apply an approach using statistical modeling to compare the heterogeneity in phenotypes across samples and subclone lineages. One strain was further used to show how individual subclonal lineages are remarkably different not just in phenotype but also in the level of heterogeneity in phenotype. With these observations, we call attention to the fact that choosing an initial clonal lineage from an industrial yeast strain may vastly influence downstream performances and observations on karyotype, on phenotype, and also on heterogeneity.
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Affiliation(s)
- Hanna Viktória Rácz
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.,Doctoral School of Nutrition and Food Sciences, University of Debrecen, Debrecen, Hungary
| | - Fezan Mukhtar
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Alexandra Imre
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary.,Kálmán Laki Doctoral School of Biomedical and Clinical Sciences, University of Debrecen, Debrecen, Hungary
| | - Zoltán Rádai
- MTA-ÖK Lendület Seed Ecology Research Group, Institute of Ecology and Botany, Centre for Ecological Research, Vácrátót, Hungary
| | | | - Tamás Rátonyi
- Institute of Land Use, Technology and Regional Development, University of Debrecen, Debrecen, Hungary
| | - János Nagy
- Institute of Land Use, Technology and Regional Development, University of Debrecen, Debrecen, Hungary
| | - István Pócsi
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
| | - Walter P Pfliegler
- Department of Molecular Biotechnology and Microbiology, University of Debrecen, Debrecen, Hungary
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11
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The interplay of phenotype and genotype in Cryptococcus neoformans disease. Biosci Rep 2021; 40:226594. [PMID: 33021310 PMCID: PMC7569153 DOI: 10.1042/bsr20190337] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2020] [Revised: 09/23/2020] [Accepted: 10/06/2020] [Indexed: 12/17/2022] Open
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen that causes life-threatening meningitis primarily in immunocompromised individuals. In order to survive and proliferate during infection, C. neoformans must adapt to a variety of stresses it encounters within the host. Patient outcome depends on the interaction between the pathogen and the host. Understanding the mechanisms that C. neoformans uses to facilitate adaptation to the host and promote pathogenesis is necessary to better predict disease severity and establish proper treatment. Several virulence phenotypes have been characterized in C. neoformans, but the field still lacks a complete understanding of how genotype and phenotype contribute to clinical outcome. Furthermore, while it is known that C. neoformans genotype impacts patient outcome, the mechanisms remain unknown. This lack of understanding may be due to the genetic heterogeneity of C. neoformans and the extensive phenotypic variation observed between and within isolates during infection. In this review, we summarize the current understanding of how the various genotypes and phenotypes observed in C. neoformans correlate with human disease progression in the context of patient outcome and recurrence. We also postulate the mechanisms underlying the genetic and phenotypic changes that occur in vivo to promote rapid adaptation in the host.
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12
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Comparative Analysis of Putative Virulence-Associated Factors of Microsporum canis Isolates from Human and Animal Patients. Mycopathologia 2020; 185:665-673. [PMID: 32643011 DOI: 10.1007/s11046-020-00470-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Accepted: 06/23/2020] [Indexed: 10/20/2022]
Abstract
Microsporum canis is a zoophilic dermatophyte and the most common fungus isolated from dogs and cats worldwide. To invade skin, this pathogen uses different enzymes, which may be associated with virulence, that contribute to the fungal pathogenicity. The aim of this study is to compare the expression of enzymes that may be associated with virulence, and thermotolerance of M. canis strains isolated from dogs, cats, and humans. The in vitro expression of the enzymes keratinase, catalase, urease, hemolysin, and aspartic protease was evaluated in 52 M. canis strains recently isolated from 14 human patients, 12 dogs, 15 symptomatic, and 11 asymptomatic cats. In addition, thermotolerance was assessed by comparative analysis of fungal growth at 25 °C and 35 °C. Keratinase activity was low in 34 and moderate in 18 strains. Aspartic-protease activity was low in 7, moderate in 33, and high in 12 strains. Hemolysin activity was low in 44 and moderate in 8 strains. All strains were classified as low producers of catalase. All but three strains produced urease in vitro, with a broad range of activity. The strains presented in vitro growth at the two studied temperatures were classified as presenting low (36.5%), medium (44.3%), or high (19.2%) thermotolerance. There was no statistically significant difference in the new putative virulence-associated factors studied among the different hosts, which suggests that they may have a similar role on human, cat, and dog infection. Also, no difference was observed between strains isolated from symptomatic and asymptomatic cats. This suggests that these factors have a limited impact on the fate of feline dermatophytosis caused by M. canis.
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13
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Nascimento CRSD, Souto ADSS, Galvão RM, Lazéra MDS, Trilles L. Genotypic and Phenotypic Stability of Mixed Primary Isolates of Cryptococcus gattii and Cryptococcus neoformans: A Comparative Analysis of Four Preservation Methods. Biopreserv Biobank 2020; 18:196-203. [PMID: 32213084 DOI: 10.1089/bio.2019.0096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The choice of a suitable preservation method is critical for long-term microorganisms' viability. The strains should be preserved for long periods using reliable and reproducible methods that minimize genotypic and phenotypic variations and viability losses. The methodologies are usually designed for a better performance in isolated microorganisms. However, atypical primary isolates of Cryptococcus neoformans or Cryptococcus gattii, such as mixed species or even different species of a species complex, are a challenge for long-term preservation and taxonomic review studies. The aim of this study was to evaluate which of the four preservation methods tested presented better performance in the preservation of simulated coexistence strains of C. neoformans and C. gattii. Two environmental strains, one C. gattii and one C. neoformans, were mixed in vitro to test four different preservation methods (freezing at -20°C, -80°C, -196°C, and freeze-drying). The colony-forming units from each preservation method were evaluated, and colonies were randomly selected and cultivated in canavanine glycine bromothymol blue (CGB) agar to evaluate the amounts of CGB-positive (C. gattii) and CGB-negative (C. neoformans) colonies resulting from each preservation method after 1 week, 15 days, 1 month, 6 months, and 1 year. According to our results, cryopreservation at -20°C demonstrated was preferable for C. neoformans species, and further studies after long-term storage are necessary. Recovery of yeast cells after freeze-dried preservation in skim milk is better for both species. Ultrafreezing methods evaluated (-80°C and -196°C) also showed better results in the maintenance of C. gattii. Freeze-drying should be preferred for the maintenance of multilineage isolates from the C. neoformans and C. gattii species complexes.
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Affiliation(s)
- Carlos Roberto Sobrinho do Nascimento
- Microbiology Department, National Institute for Quality Control in Health, Fiocruz, Rio de Janeiro, Brazil.,Mycology Laboratory, National Institute of Infectious Diseases Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil
| | | | - Raíssa Maria Galvão
- Microbiology Department, National Institute for Quality Control in Health, Fiocruz, Rio de Janeiro, Brazil
| | - Marcia Dos Santos Lazéra
- Mycology Laboratory, National Institute of Infectious Diseases Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil
| | - Luciana Trilles
- Mycology Laboratory, National Institute of Infectious Diseases Evandro Chagas, Fiocruz, Rio de Janeiro, Brazil
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14
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Boyce KJ, Cao C, Xue C, Idnurm A. A spontaneous mutation in DNA polymerase POL3 during in vitro passaging causes a hypermutator phenotype in Cryptococcus species. DNA Repair (Amst) 2019; 86:102751. [PMID: 31838381 DOI: 10.1016/j.dnarep.2019.102751] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 11/08/2019] [Accepted: 11/19/2019] [Indexed: 10/25/2022]
Abstract
Passaging of microbes in vitro can lead to the selection of microevolved derivatives with differing properties to their original parent strains. One well characterised instance is the phenotypic differences observed between the series of strains derived from the type strain of the human pathogenic fungus Cryptococcus neoformans. A second case was reported in the close relative Cryptococcus deneoformans, in which a well-studied isolate ATCC 24067 (52D) altered its phenotypic characteristics after in vitro passaging in different laboratories. One of these derivatives, ATCC 24067A, has decreased virulence and also exhibits a hypermutator phenotype, in which the mutation rate is increased compared to wild type. In this study, the molecular basis behind the changes in the lineage of ATCC 24067 was determined by next-generation sequencing of the parent and passaged strain genomes. This analysis resulted in the identification of a point mutation that causes a D270G amino acid substitution within the exonuclease proofreading domain of the DNA polymerase delta subunit encoded by POL3. Complementation with POL3 confirmed that this mutation is responsible for the hypermutator phenotype of this strain. Regeneration of the mutation in C. neoformans, to eliminate the additional mutations present in the ATCC 24067A genetic background, demonstrated that the hypermutator phenotype of the pol3D270G mutant causes rapid microevolution in vitro but does not result in decreased virulence. These findings indicate that mutator strains can emerge in these pathogenic fungi without conferring a fitness cost, but the subsequent rapid accumulation of mutations can be deleterious.
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Affiliation(s)
- Kylie J Boyce
- School of Science, Engineering and Health, RMIT University, Victoria, Australia.
| | - Chengjun Cao
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
| | - Chaoyang Xue
- Public Health Research Institute, Rutgers University, Newark, New Jersey, USA
| | - Alexander Idnurm
- School of BioSciences, University of Melbourne, Victoria, Australia.
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15
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Mitotic Recombination and Adaptive Genomic Changes in Human Pathogenic Fungi. Genes (Basel) 2019; 10:genes10110901. [PMID: 31703352 PMCID: PMC6895784 DOI: 10.3390/genes10110901] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2019] [Revised: 11/01/2019] [Accepted: 11/05/2019] [Indexed: 12/11/2022] Open
Abstract
Genome rearrangements and ploidy alterations are important for adaptive change in the pathogenic fungal species Candida and Cryptococcus, which propagate primarily through clonal, asexual reproduction. These changes can occur during mitotic growth and lead to enhanced virulence, drug resistance, and persistence in chronic infections. Examples of microevolution during the course of infection were described in both human infections and mouse models. Recent discoveries defining the role of sexual, parasexual, and unisexual cycles in the evolution of these pathogenic fungi further expanded our understanding of the diversity found in and between species. During mitotic growth, damage to DNA in the form of double-strand breaks (DSBs) is repaired, and genome integrity is restored by the homologous recombination and non-homologous end-joining pathways. In addition to faithful repair, these pathways can introduce minor sequence alterations at the break site or lead to more extensive genetic alterations that include loss of heterozygosity, inversions, duplications, deletions, and translocations. In particular, the prevalence of repetitive sequences in fungal genomes provides opportunities for structural rearrangements to be generated by non-allelic (ectopic) recombination. In this review, we describe DSB repair mechanisms and the types of resulting genome alterations that were documented in the model yeast Saccharomyces cerevisiae. The relevance of similar recombination events to stress- and drug-related adaptations and in generating species diversity are discussed for the human fungal pathogens Candida albicans and Cryptococcus neoformans.
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16
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Firacative C, Torres G, Meyer W, Escandón P. Clonal Dispersal of Cryptococcus gattii VGII in an Endemic Region of Cryptococcosis in Colombia. J Fungi (Basel) 2019; 5:jof5020032. [PMID: 30991682 PMCID: PMC6616963 DOI: 10.3390/jof5020032] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2019] [Revised: 04/04/2019] [Accepted: 04/06/2019] [Indexed: 12/15/2022] Open
Abstract
This study characterized the genotype and phenotype of Cryptococcus gattii VGII isolates from Cucuta, an endemic region of cryptococcal disease in Colombia, and compared these traits with those from representative isolates from the Vancouver Island outbreak (VGIIa and VGIIb). Genetic diversity was assessed by multilocus sequence typing (MLST) analysis. Phenotypic characteristics, including growth capacity under different temperature and humidity conditions, macroscopic and microscopic morphology, phenotypic switching, mating type, and activity of extracellular enzymes were studied. Virulence was studied in vivo in a mouse model. MLST analysis showed that the isolates from Cucuta were highly clonal, with ST25 being the most common genotype. Phenotypically, isolates from Cucuta showed large cell and capsular sizes, and shared phenotypic traits and enzymatic activities among them. The mating type a prevailed among the isolates, which were fertile and of considerable virulence in the animal model. This study highlights the need for a continuous surveillance of C. gattii in Colombia, especially in endemic areas like Cucuta, where the highest number of cryptococcosis cases due to this species is reported. This will allow the early detection of potentially highly virulent strains that spread clonally, and can help prevent the occurrence of outbreaks in Colombia and elsewhere.
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Affiliation(s)
- Carolina Firacative
- Studies in Translational Microbiology and Emerging Diseases (MICROS) Research Group, School of Medicine and Health Sciences, Universidad del Rosario, Bogota 111221, Colombia.
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Clinical School, Faculty of Medicine and Health, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Hospital (Research and Education Network), Westmead Institute for Medical Research, Westmead, NSW 2145, Australia.
| | - Germán Torres
- Microbiology Group, Instituto Nacional de Salud, Bogota 11321, Colombia.
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Westmead Clinical School, Faculty of Medicine and Health, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Hospital (Research and Education Network), Westmead Institute for Medical Research, Westmead, NSW 2145, Australia.
| | - Patricia Escandón
- Microbiology Group, Instituto Nacional de Salud, Bogota 11321, Colombia.
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17
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Probert M, Zhou X, Goodall M, Johnston SA, Bielska E, Ballou ER, May RC. A Glucuronoxylomannan Epitope Exhibits Serotype-Specific Accessibility and Redistributes towards the Capsule Surface during Titanization of the Fungal Pathogen Cryptococcus neoformans. Infect Immun 2019; 87:IAI.00731-18. [PMID: 30670549 PMCID: PMC6434129 DOI: 10.1128/iai.00731-18] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2018] [Accepted: 12/23/2018] [Indexed: 11/20/2022] Open
Abstract
Disseminated infections with the fungal species Cryptococcus neoformans or, less frequently, Cryptococcus gattii are an important cause of mortality in immunocompromised individuals. Central to the virulence of both species is an elaborate polysaccharide capsule that consists predominantly of glucuronoxylomannan (GXM). Due to its abundance, GXM is an ideal target for host antibodies, and several monoclonal antibodies (mAbs) have previously been derived using purified GXM or whole capsular preparations as antigens. In addition to their application in the diagnosis of cryptococcosis, anti-GXM mAbs are invaluable tools for studying capsule structure. In this study, we report the production and characterization of a novel anti-GXM mAb, Crp127, that unexpectedly reveals a role for GXM remodeling during the process of fungal titanization. We show that Crp127 recognizes a GXM epitope in an O-acetylation-dependent, but xylosylation-independent, manner. The epitope is differentially expressed by the four main serotypes of Cryptococcus neoformans and C. gattii, is heterogeneously expressed within clonal populations of C. gattii serotype B strains, and is typically confined to the central region of the enlarged capsule. Uniquely, however, this epitope redistributes to the capsular surface in titan cells, a recently characterized morphotype where haploid 5-μm cells convert to highly polyploid cells of >10 μm with distinct but poorly understood capsular characteristics. Titan cells are produced in the host lung and critical for successful infection. Crp127 therefore advances our understanding of cryptococcal morphological change and may hold significant potential as a tool to differentially identify cryptococcal strains and subtypes.
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Affiliation(s)
- Mark Probert
- Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Xin Zhou
- Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Margaret Goodall
- Institute of Immunology and Immunotherapy, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Simon A Johnston
- Department of Infection, Immunity and Cardiovascular Disease, University of Sheffield, Sheffield, United Kingdom
- Bateson Centre, University of Sheffield, Sheffield, United Kingdom
| | - Ewa Bielska
- Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Elizabeth R Ballou
- Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
| | - Robin C May
- Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, United Kingdom
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham, United Kingdom
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18
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Genotypic Diversity Is Independent of Pathogenicity in Colombian Strains of Cryptococcus neoformans and Cryptococcus gattii in Galleria mellonella. J Fungi (Basel) 2018; 4:jof4030082. [PMID: 29976849 PMCID: PMC6162678 DOI: 10.3390/jof4030082] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 06/29/2018] [Accepted: 06/30/2018] [Indexed: 12/15/2022] Open
Abstract
Cryptococcosis is a potentially fatal opportunistic mycosis that affects the lungs and central nervous system. It has been suggested that certain strains of C. neoformans/C. gattii may have the potential to be more virulent according to the molecular type. This study aims to investigate the association between virulence in the G. mellonella model and genotypic diversity of Colombian clinical and environmental isolates of C. neoformans/C. gattii. A total of 33 clinical and 12 environmental isolates were selected according to their geographical origin and sequence types (STs). Pathogenicity was determined using the G. mellonella model, and the cell and capsular size before and after inoculation was determined. For C. neoformans, virulence in G. mellonella revealed that death occurred on average on day 6 (p < 0.05) and that ST5C, 6C, 25C and 71C were the most virulent. In C. gattii, death occurred at 7.3 days (p < 0.05), and ST47C, 58C, 75A and 106C were the most virulent. Capsular size increased for both species after passage in G. mellonella. In conclusion, the pathogenicity of Cryptococcus strains in the G. mellonella invertebrate model is independent of molecular type or pathogenicity factor, even within the same ST, but it is possible to find variable degrees of pathogenicity.
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19
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Rodrigues J, Ramos CL, Frases S, Godinho RMDC, Fonseca FL, Rodrigues ML. Lack of chitin synthase genes impacts capsular architecture and cellular physiology in Cryptococcus neoformans. Cell Surf 2018; 2:14-23. [PMID: 32743128 PMCID: PMC7389344 DOI: 10.1016/j.tcsw.2018.05.002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 05/21/2018] [Accepted: 05/25/2018] [Indexed: 02/06/2023] Open
Abstract
Cryptococcus neoformans mutants lacking each of the eight putative chitin synthase genes (CHS) have been previously generated. However, it is still unclear how deletion of chitin synthase genes affects the cryptococcal capsule. Since the connections between chitin metabolism and capsular polysaccharides in C. neoformans are numerous, we analyzed the effects of deletion of CHS genes on capsular and capsule-related structures of C. neoformans. CHS deletion affected capsular morphology in multiple ways, as determined by scanning electron microscopy and immunofluorescence analysis. Molecular diameter, serological reactivity and export of capsular polysaccharide were also affected in most of the chsΔ mutants, but the most prominent alterations were observed in the chs3Δ strain. C. neoformans cells lacking CHS genes also had altered formation of extracellular vesicles and variable chitinase activity under stress conditions. These results reveal previously unknown functions of CHS genes that greatly impact the physiology of C. neoformans.
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Affiliation(s)
- Jessica Rodrigues
- Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Caroline L Ramos
- Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Susana Frases
- Instituto de Biofísica Carlos Chagas Filho, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Rodrigo M da C Godinho
- Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil
| | - Fernanda L Fonseca
- Centro de Desenvolvimento Tecnológico em Saúde (CDTS) da Fundação Oswaldo Cruz (Fiocruz), Rio de Janeiro, Brazil
| | - Marcio L Rodrigues
- Instituto de Microbiologia Paulo de Góes, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.,Instituto Carlos Chagas (ICC), Fundação Oswaldo Cruz (Fiocruz), Curitiba, PR, Brazil
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20
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Hommel B, Mukaremera L, Cordero RJB, Coelho C, Desjardins CA, Sturny-Leclère A, Janbon G, Perfect JR, Fraser JA, Casadevall A, Cuomo CA, Dromer F, Nielsen K, Alanio A. Titan cells formation in Cryptococcus neoformans is finely tuned by environmental conditions and modulated by positive and negative genetic regulators. PLoS Pathog 2018; 14:e1006982. [PMID: 29775480 PMCID: PMC5959062 DOI: 10.1371/journal.ppat.1006982] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2017] [Accepted: 03/19/2018] [Indexed: 01/06/2023] Open
Abstract
The pathogenic fungus Cryptococcus neoformans exhibits morphological changes in cell size during lung infection, producing both typical size 5 to 7 μm cells and large titan cells (> 10 μm and up to 100 μm). We found and optimized in vitro conditions that produce titan cells in order to identify the ancestry of titan cells, the environmental determinants, and the key gene regulators of titan cell formation. Titan cells generated in vitro harbor the main characteristics of titan cells produced in vivo including their large cell size (>10 μm), polyploidy with a single nucleus, large vacuole, dense capsule, and thick cell wall. Here we show titan cells derived from the enlargement of progenitor cells in the population independent of yeast growth rate. Change in the incubation medium, hypoxia, nutrient starvation and low pH were the main factors that trigger titan cell formation, while quorum sensing factors like the initial inoculum concentration, pantothenic acid, and the quorum sensing peptide Qsp1p also impacted titan cell formation. Inhibition of ergosterol, protein and nucleic acid biosynthesis altered titan cell formation, as did serum, phospholipids and anti-capsular antibodies in our settings. We explored genetic factors important for titan cell formation using three approaches. Using H99-derivative strains with natural genetic differences, we showed that titan cell formation was dependent on LMP1 and SGF29 genes. By screening a gene deletion collection, we also confirmed that GPR4/5-RIM101, and CAC1 genes were required to generate titan cells and that the PKR1, TSP2, USV101 genes negatively regulated titan cell formation. Furthermore, analysis of spontaneous Pkr1 loss-of-function clinical isolates confirmed the important role of the Pkr1 protein as a negative regulator of titan cell formation. Through development of a standardized and robust in vitro assay, our results provide new insights into titan cell biogenesis with the identification of multiple important factors/pathways.
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Affiliation(s)
- Benjamin Hommel
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
- Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
| | - Liliane Mukaremera
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Radames J. B. Cordero
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | - Carolina Coelho
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | | | - Aude Sturny-Leclère
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
| | - Guilhem Janbon
- Institut Pasteur, Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Paris, France
| | - John R. Perfect
- Division of Infectious Diseases, Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
| | - James A. Fraser
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - Arturo Casadevall
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
| | - Christina A. Cuomo
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Françoise Dromer
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, Minnesota, United States of America
| | - Alexandre Alanio
- Institut Pasteur, Molecular Mycology Unit, Département de Mycologie, Paris, France
- CNRS UMR2000, Paris, France
- Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Paris, France
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD., United States of America
- * E-mail:
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21
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Bouklas T, Masone L, Fries BC. Differences in Sirtuin Regulation in Response to Calorie Restriction in Cryptococcus neoformans. J Fungi (Basel) 2018; 4:E26. [PMID: 29463010 PMCID: PMC5872329 DOI: 10.3390/jof4010026] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2018] [Revised: 02/15/2018] [Accepted: 02/16/2018] [Indexed: 12/17/2022] Open
Abstract
Cryptococcus neoformans successfully replicates in low glucose in infected patients. In the serotype A strain, H99, growth in this condition prolongs lifespan regulated by SIR2, and can be modulated with SIR2-specific drugs. Previous studies show that lifespan modulation of a cryptococcal population affects its sensitivity to antifungals, and survival in an infection model. Sirtuins and their role in longevity are conserved among fungi; however, the effect of glucose starvation is not confirmed even in Saccharomyces cerevisiae. Lifespan analysis of C. neoformans strains in low glucose showed that 37.5% exhibited pro-longevity, and lifespan of a serotype D strain, RC2, was shortened. Transcriptome comparison of H99 and RC2 under calorie restriction demonstrated differences, confirmed by real-time PCR showing that SIR2, TOR1, SCH9, and PKA1 expression correlated with lifespan response to calorie restriction. As expected, RC2-sir2Δ cells exhibited a shortened lifespan, which was reconstituted. However, shortened lifespan from calorie restriction was independent of SIR2. In contrast to H99 but consistent with altered SIR2 regulation, SIR2-specific drugs did not affect outcome of RC2 infection. These data suggest that SIR2 regulation and response to calorie restriction varies in C. neoformans, which should be considered when Sirtuins are investigated as potential therapy targets for fungal infections.
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Affiliation(s)
- Tejas Bouklas
- Department of Biomedical Sciences, Long Island University-Post, Brookville, NY 11548, USA.
| | - Lindsey Masone
- Department of Biomedical Sciences, Long Island University-Post, Brookville, NY 11548, USA.
| | - Bettina C Fries
- Department of Medicine (Division of Infectious Diseases) and Department of Molecular Genetics and Microbiology, Stony Brook University, Stony Brook, NY 11794 USA.
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22
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Arras SDM, Ormerod KL, Erpf PE, Espinosa MI, Carpenter AC, Blundell RD, Stowasser SR, Schulz BL, Tanurdzic M, Fraser JA. Convergent microevolution of Cryptococcus neoformans hypervirulence in the laboratory and the clinic. Sci Rep 2017; 7:17918. [PMID: 29263343 PMCID: PMC5738413 DOI: 10.1038/s41598-017-18106-2] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2017] [Accepted: 12/05/2017] [Indexed: 12/30/2022] Open
Abstract
Reference strains are a key component of laboratory research, providing a common background allowing for comparisons across a community of researchers. However, laboratory passage of these strains has been shown to lead to reduced fitness and the attenuation of virulence in some species. In this study we show the opposite in the fungal pathogen Cryptococcus neoformans, with analysis of a collection of type strain H99 subcultures revealing that the most commonly used laboratory subcultures belong to a mutant lineage of the type strain that is hypervirulent. The pleiotropic mutant phenotypes in this H99L (for “Laboratory”) lineage are the result of a deletion in the gene encoding the SAGA Associated Factor Sgf29, a mutation that is also present in the widely-used H99L-derived KN99a/α congenic pair. At a molecular level, loss of this gene results in a reduction in histone H3K9 acetylation. Remarkably, analysis of clinical isolates identified loss of function SGF29 mutations in C. neoformans strains infecting two of fourteen patients, demonstrating not only the first example of hypervirulence in clinical C. neoformans samples, but also parallels between in vitro and in vivo microevolution for hypervirulence in this important pathogen.
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Affiliation(s)
- Samantha D M Arras
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Kate L Ormerod
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Paige E Erpf
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Monica I Espinosa
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Alex C Carpenter
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Ross D Blundell
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Samantha R Stowasser
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Benjamin L Schulz
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia.,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Milos Tanurdzic
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - James A Fraser
- Australian Infectious Diseases Research Centre, The University of Queensland, Brisbane, Queensland, Australia. .,School of Chemistry & Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia.
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Effects of sub-culturing on genetic and physiological parameters in different Beauveria bassiana isolates. J Invertebr Pathol 2017; 145:62-67. [DOI: 10.1016/j.jip.2017.03.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Revised: 03/09/2017] [Accepted: 03/19/2017] [Indexed: 11/20/2022]
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24
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Arras SDM, Chitty JL, Wizrah MSI, Erpf PE, Schulz BL, Tanurdzic M, Fraser JA. Sirtuins in the phylum Basidiomycota: A role in virulence in Cryptococcus neoformans. Sci Rep 2017; 7:46567. [PMID: 28429797 PMCID: PMC5399365 DOI: 10.1038/srep46567] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 03/17/2017] [Indexed: 02/07/2023] Open
Abstract
Virulence of Cryptococcus neoformans is regulated by a range of transcription factors, and is also influenced by the acquisition of adaptive mutations during infection. Beyond the temporal regulation of virulence factor production by transcription factors and these permanent microevolutionary changes, heritable epigenetic modifications such as histone deacetylation may also play a role during infection. Here we describe the first comprehensive analysis of the sirtuin class of NAD+ dependent histone deacetylases in the phylum Basidiomycota, identifying five sirtuins encoded in the C. neoformans genome. Each sirtuin gene was deleted and a wide range of phenotypic tests performed to gain insight into the potential roles they play. Given the pleiotropic nature of sirtuins in other species, it was surprising that only two of the five deletion strains revealed mutant phenotypes in vitro. However, cryptic consequences of the loss of each sirtuin were identified through whole cell proteomics, and mouse infections revealed a role in virulence for SIR2, HST3 and HST4. The most intriguing phenotype was the repeated inability to complement mutant phenotypes through the reintroduction of the wild-type gene. These data support the model that regulation of sirtuin activity may be employed to enable a drastic alteration of the epigenetic landscape and virulence of C. neoformans.
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Affiliation(s)
- Samantha D M Arras
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Jessica L Chitty
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Maha S I Wizrah
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Paige E Erpf
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Benjamin L Schulz
- School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Milos Tanurdzic
- School of Biological Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - James A Fraser
- Australian Infectious Diseases Research Centre, Queensland, Australia.,School of Chemistry &Molecular Biosciences, The University of Queensland, Brisbane, Queensland, Australia
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First in Vivo Batrachochytrium dendrobatidis Transcriptomes Reveal Mechanisms of Host Exploitation, Host-Specific Gene Expression, and Expressed Genotype Shifts. G3-GENES GENOMES GENETICS 2017; 7:269-278. [PMID: 27856699 PMCID: PMC5217115 DOI: 10.1534/g3.116.035873] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
For generalist pathogens, host species represent distinct selective environments, providing unique challenges for resource acquisition and defense from host immunity, potentially resulting in host-dependent differences in pathogen fitness. Gene expression modulation should be advantageous, responding optimally to a given host and mitigating the costs of generalism. Batrachochytrium dendrobatidis (Bd), a fungal pathogen of amphibians, shows variability in pathogenicity among isolates, and within-strain virulence changes rapidly during serial passages through artificial culture. For the first time, we characterize the transcriptomic profile of Bd in vivo, using laser-capture microdissection. Comparison of Bd transcriptomes (strain JEL423) in culture and in two hosts (Atelopus zeteki and Hylomantis lemur), reveals >2000 differentially expressed genes that likely include key Bd defense and host exploitation mechanisms. Variation in Bd transcriptomes from different amphibian hosts demonstrates shifts in pathogen resource allocation. Furthermore, expressed genotype variant frequencies of Bd populations differ between culture and amphibian skin, and among host species, revealing potential mechanisms underlying rapid changes in virulence and the possibility that amphibian community composition shapes Bd evolutionary trajectories. Our results provide new insights into how changes in gene expression and infecting population genotypes can be key to the success of a generalist fungal pathogen.
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26
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Aminnejad M, Cogliati M, Duan S, Arabatzis M, Tintelnot K, Castañeda E, Lazéra M, Velegraki A, Ellis D, Sorrell TC, Meyer W. Identification and Characterization of VNI/VNII and Novel VNII/VNIV Hybrids and Impact of Hybridization on Virulence and Antifungal Susceptibility Within the C. neoformans/C. gattii Species Complex. PLoS One 2016; 11:e0163955. [PMID: 27764108 PMCID: PMC5072701 DOI: 10.1371/journal.pone.0163955] [Citation(s) in RCA: 11] [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: 03/31/2016] [Accepted: 09/16/2016] [Indexed: 12/14/2022] Open
Abstract
Cryptococcus neoformans and C. gattii are pathogenic basidiomycetous yeasts and the commonest cause of fungal infection of the central nervous system. Cryptococci are typically haploid but several inter-species, inter-varietal and intra-varietal hybrids have been reported. It has a bipolar mating system with sexual reproduction occurring normally between two individuals with opposite mating types, α and a. This study set out to characterize hybrid isolates within the C. neoformans/C. gattii species complex: seven unisexual mating intra-varietal VNI/VNII (αAAα) and six novel inter-varietal VNII/VNIV (aADα). The URA5-RFLP pattern for VNII/VNIV (aADα) differs from the VNIII (αADa) hybrids. Analysis of the allelic patterns of selected genes for AD hybrids showed 79% or more heterozygosis for the studied loci except for CBS132 (VNIII), which showed 50% of heterozygosity. MALDI-TOF MS was applied to hybrids belonging to different sero/mating type allelic patterns. All hybrid isolates were identified as belonging to the same hybrid group with identification scores ranging between 2.101 to 2.634. All hybrids were virulent when tested in the Galleria mellonella (wax moth) model, except for VNII/VNIV (aADα) hybrids. VNI/VGII hybrids were the most virulent hybrids. Hybrids recovered from larvae manifested a significant increase in capsule and total cell size and produced a low proportion (5-10%) of giant cells compared with the haploid control strains. All strains expressed the major virulence factors-capsule, melanin and phospholipase B-and grew well at 37°C. The minimal inhibitory concentration of nine drugs was measured by micro-broth dilution and compared with published data on haploid strains. MICs were similar amongst hybrids and haploid parental strains. This is the first study reporting natural same sex αAAα intra-varietal VNI/VNII hybrids and aADα inter-varietal VNII/VNIV hybrids.
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Affiliation(s)
- Mojgan Aminnejad
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
| | - Massimo Cogliati
- Laboratory Micologia Medica, Dip. Scienze Biomediche per la Salute, Università degli Studi di Milano, Milano, Italy
| | - Shuyao Duan
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
| | - Michael Arabatzis
- Mycology Research Laboratory, Department of Microbiology, Medical School, National Kapodistrian University of Athens, Athens, Greece
| | | | | | - Marcia Lazéra
- Mycology Laboratory, National Institute of Infectious Diseases, Oswaldo Cruz Foundation, Rio de Janeiro, Brazil
| | - Aristea Velegraki
- Mycology Research Laboratory, Department of Microbiology, Medical School, National Kapodistrian University of Athens, Athens, Greece
| | - David Ellis
- School of Molecular & Biomedical Sciences, University of Adelaide, Adelaide, SA 5005, Australia
| | - Tania C. Sorrell
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
| | - Wieland Meyer
- Molecular Mycology Research Laboratory, Centre for Infectious Diseases and Microbiology, Sydney Medical School – Westmead Hospital, Marie Bashir Institute for Infectious Diseases and Biosecurity, The University of Sydney, Westmead Institute for Medical Research, Sydney, Australia
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27
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Heterogeneity among Isolates Reveals that Fitness in Low Oxygen Correlates with Aspergillus fumigatus Virulence. mBio 2016; 7:mBio.01515-16. [PMID: 27651366 PMCID: PMC5040115 DOI: 10.1128/mbio.01515-16] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
UNLABELLED Previous work has shown that environmental and clinical isolates of Aspergillus fumigatus represent a diverse population that occupies a variety of niches, has extensive genetic diversity, and exhibits virulence heterogeneity in a number of animal models of invasive pulmonary aspergillosis (IPA). However, mechanisms explaining differences in virulence among A. fumigatus isolates remain enigmatic. Here, we report a significant difference in virulence of two common lab strains, CEA10 and AF293, in the murine triamcinolone immunosuppression model of IPA, in which we previously identified severe low oxygen microenvironments surrounding fungal lesions. Therefore, we hypothesize that the ability to thrive within these lesions of low oxygen promotes virulence of A. fumigatus in this model. To test this hypothesis, we performed in vitro fitness and in vivo virulence analyses in the triamcinolone murine model of IPA with 14 environmental and clinical isolates of A. fumigatus Among these isolates, we observed a strong correlation between fitness in low oxygen in vitro and virulence. In further support of our hypothesis, experimental evolution of AF293, a strain that exhibits reduced fitness in low oxygen and reduced virulence in the triamcinolone model of IPA, results in a strain (EVOL20) that has increased hypoxia fitness and a corresponding increase in virulence. Thus, the ability to thrive in low oxygen correlates with virulence of A. fumigatus isolates in the context of steroid-mediated murine immunosuppression. IMPORTANCE Aspergillus fumigatus occupies multiple environmental niches, likely contributing to the genotypic and phenotypic heterogeneity among isolates. Despite reports of virulence heterogeneity, pathogenesis studies often utilize a single strain for the identification and characterization of virulence and immunity factors. Here, we describe significant variation between A. fumigatus isolates in hypoxia fitness and virulence, highlighting the advantage of including multiple strains in future studies. We also illustrate that hypoxia fitness correlates strongly with increased virulence exclusively in the nonleukopenic murine triamcinolone immunosuppression model of IPA. Through an experimental evolution experiment, we observe that chronic hypoxia exposure results in increased virulence of A. fumigatus We describe here the first observation of a model-specific virulence phenotype correlative with in vitro fitness in hypoxia and pave the way for identification of hypoxia-mediated mechanisms of virulence in the fungal pathogen A. fumigatus.
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ALL2, a Homologue of ALL1, Has a Distinct Role in Regulating pH Homeostasis in the Pathogen Cryptococcus neoformans. Infect Immun 2015; 84:439-51. [PMID: 26597983 DOI: 10.1128/iai.01046-15] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 11/13/2015] [Indexed: 12/30/2022] Open
Abstract
Cryptococcus neoformans is a facultative intracellular fungal pathogen that has a polysaccharide capsule and causes life-threatening meningoencephalitis. Its capsule, as well as its ability to survive in the acidic environment of the phagolysosome, contributes to the pathogen's resilience in the host environment. Previously, we reported that downregulation of allergen 1 (ALL1) results in the secretion of a shorter, more viscous exopolysaccharide with less branching and structural complexity, as well as altered iron homeostasis. Now, we report on a homologous coregulated gene, allergen 2 (ALL2). ALL2's function was characterized by generating null mutants in C. neoformans. In contrast to ALL1, loss of ALL2 attenuated virulence in the pulmonary infection model. The all2Δ mutant shed a less viscous exopolysaccharide and exhibited higher sensitivity to hydrogen peroxide than the wild type, and as a result, the all2Δ mutant was more resistant to macrophage-mediated killing. Transcriptome analysis further supported the distinct function of these two genes. Unlike ALL1's involvement in iron homeostasis, we now present data on ALL2's unique function in maintaining intracellular pH in low-pH conditions. Thus, our data highlight that C. neoformans, a human-pathogenic basidiomycete, has evolved a unique set of virulence-associated genes that contributes to its resilience in the human niche.
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29
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Refsnider JM, Poorten TJ, Langhammer PF, Burrowes PA, Rosenblum EB. Genomic Correlates of Virulence Attenuation in the Deadly Amphibian Chytrid Fungus, Batrachochytrium dendrobatidis. G3 (BETHESDA, MD.) 2015; 5:2291-8. [PMID: 26333840 PMCID: PMC4632049 DOI: 10.1534/g3.115.021808] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 08/28/2015] [Indexed: 11/18/2022]
Abstract
Emerging infectious diseasespose a significant threat to global health, but predicting disease outcomes for particular species can be complicated when pathogen virulence varies across space, time, or hosts. The pathogenic chytrid fungus Batrachochytrium dendrobatidis (Bd) has caused worldwide declines in frog populations. Not only do Bd isolates from wild populations vary in virulence, but virulence shifts can occur over short timescales when Bd is maintained in the laboratory. We leveraged changes in Bd virulence over multiple generations of passage to better understand mechanisms of pathogen virulence. We conducted whole-genome resequencing of two samples of the same Bd isolate, differing only in passage history, to identify genomic processes associated with virulence attenuation. The isolate with shorter passage history (and greater virulence) had greater chromosome copy numbers than the isolate maintained in culture for longer, suggesting that virulence attenuation may be associated with loss of chromosome copies. Our results suggest that genomic processes proposed as mechanisms for rapid evolution in Bd are correlated with virulence attenuation in laboratory culture within a single lineage of Bd. Moreover, these genomic processes can occur over extremely short timescales. On a practical level, our results underscore the importance of immediately cryo-archiving new Bd isolates and using fresh isolates, rather than samples cultured in the laboratory for long periods, for laboratory infection experiments. Finally, when attempting to predict disease outcomes for this ecologically important pathogen, it is critical to consider existing variation in virulence among isolates and the potential for shifts in virulence over short timescales.
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Affiliation(s)
- Jeanine M Refsnider
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California 94720-3114
| | - Thomas J Poorten
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California 94720-3114
| | | | - Patricia A Burrowes
- Department of Biology, University of Puerto Rico, San Juan, Puerto Rico 00931-3360
| | - Erica Bree Rosenblum
- Department of Environmental Science, Policy, and Management, University of California, Berkeley, Berkeley, California 94720-3114
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30
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Idnurm A, Lin X. Rising to the challenge of multiple Cryptococcus species and the diseases they cause. Fungal Genet Biol 2015; 78:1-6. [PMID: 25983191 DOI: 10.1016/j.fgb.2015.05.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2015] [Revised: 05/05/2015] [Accepted: 05/06/2015] [Indexed: 12/28/2022]
Abstract
Cryptococcus neoformans and Cryptococcus gattii are well-studied basidiomyceteous yeasts that are capable of causing disease in healthy and immunocompromised people. The Conference on Cryptococcus and Cryptococcosis (ICCC) is held every three years: the accompanying Special Issue stems from the 9th ICCC and covers a subset of the topics related to these fungi in detail. This conference started with a revised and reduced estimate of disease burden globally, in part due to improved treatment for HIV(+) people. However, mortality from cryptococcosis remains consistently high for those unfortunate to have limited access to therapies or without underlying immunodeficiencies. As such, there are yet still great distances to be covered to address antifungal drug availability, the need for new antifungal agents and the timing and doses of these agents in conjunction with antiviral therapy, underscoring the importance of continued research. A notable point from the 9th ICCC was the research addressing the variation in the pathogen and host populations. Analysis of cryptococcal strain variability, particularly at the molecular level, has resolved distinct lineages with the consequence of a taxonomic revision that divides C. neoformans and C. gattii into seven Cryptococcus species. Similarly, analysis of host factors in so called "immune-competent" individuals revealed previously unrecognized risk factors. Research on these species has established them as important model organisms to understand gene evolution and function in other fungi and eukaryotes. The stage is set for the refinement of research directions, leading ultimately to better treatment of this monophyletic clade of pathogens in the genus Cryptococcus.
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Affiliation(s)
- Alexander Idnurm
- School of BioSciences, University of Melbourne, VIC 3010, Australia.
| | - Xiaorong Lin
- Department of Biology, Texas A&M University, College Station, TX 77843, USA.
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31
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Springer DJ, Billmyre RB, Filler EE, Voelz K, Pursall R, Mieczkowski PA, Larsen RA, Dietrich FS, May RC, Filler SG, Heitman J. Cryptococcus gattii VGIII isolates causing infections in HIV/AIDS patients in Southern California: identification of the local environmental source as arboreal. PLoS Pathog 2014; 10:e1004285. [PMID: 25144534 PMCID: PMC4140843 DOI: 10.1371/journal.ppat.1004285] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2014] [Accepted: 06/16/2014] [Indexed: 12/30/2022] Open
Abstract
Ongoing Cryptococcus gattii outbreaks in the Western United States and Canada illustrate the impact of environmental reservoirs and both clonal and recombining propagation in driving emergence and expansion of microbial pathogens. C. gattii comprises four distinct molecular types: VGI, VGII, VGIII, and VGIV, with no evidence of nuclear genetic exchange, indicating these represent distinct species. C. gattii VGII isolates are causing the Pacific Northwest outbreak, whereas VGIII isolates frequently infect HIV/AIDS patients in Southern California. VGI, VGII, and VGIII have been isolated from patients and animals in the Western US, suggesting these molecular types occur in the environment. However, only two environmental isolates of C. gattii have ever been reported from California: CBS7750 (VGII) and WM161 (VGIII). The incongruence of frequent clinical presence and uncommon environmental isolation suggests an unknown C. gattii reservoir in California. Here we report frequent isolation of C. gattii VGIII MATα and MATa isolates and infrequent isolation of VGI MATα from environmental sources in Southern California. VGIII isolates were obtained from soil debris associated with tree species not previously reported as hosts from sites near residences of infected patients. These isolates are fertile under laboratory conditions, produce abundant spores, and are part of both locally and more distantly recombining populations. MLST and whole genome sequence analysis provide compelling evidence that these environmental isolates are the source of human infections. Isolates displayed wide-ranging virulence in macrophage and animal models. When clinical and environmental isolates with indistinguishable MLST profiles were compared, environmental isolates were less virulent. Taken together, our studies reveal an environmental source and risk of C. gattii to HIV/AIDS patients with implications for the >1,000,000 cryptococcal infections occurring annually for which the causative isolate is rarely assigned species status. Thus, the C. gattii global health burden could be more substantial than currently appreciated. The environmentally-acquired human pathogen C. gattii is responsible for ongoing and expanding outbreaks in the Western United States and Canada. C. gattii comprises four distinct molecular types: VGI, VGII, VGIII, and VGIV. Molecular types VGI, VGII, and VGIII have been isolated from patients and animals throughout the Western US. The Pacific Northwest and Canadian outbreak is primarily caused by C. gattii VGII. VGIII is responsible for ongoing infections in HIV/AIDS patients in Southern California. However, only two environmental C. gattii isolates have ever been identified from the Californian environment: CBS7750 (VGII) and WM161 (VGIII). We sought to collect environmental samples from areas that had confirmed reports of clinical or veterinary infections. Here we report the isolation of C. gattii VGI and VGIII from environmental soil and tree samples. C. gattii isolates were obtained from three novel tree species: Canary Island pine, American sweetgum, and a Pohutukawa tree. Genetic analysis provides robust evidence that these environmental isolates are the source of human infections.
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Affiliation(s)
- Deborah J. Springer
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail: (DJS); (JH)
| | - R. Blake Billmyre
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Elan E. Filler
- David Geffen School of Medicine at UCLA, Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Los Angeles, California, United States of America
| | - Kerstin Voelz
- Institute of Microbiology & Infection and the School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- National Institute of Health Research Surgical Reconstruction and Microbiology Research Centre, Queen Elizabeth Hospital, Birmingham, United Kingdom
| | - Rhiannon Pursall
- Institute of Microbiology & Infection and the School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Piotr A. Mieczkowski
- Department of Genetics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Robert A. Larsen
- Division of Infectious Diseases, Keck School of Medicine, University of Southern California, Los Angeles, California, United States of America
| | - Fred S. Dietrich
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Robin C. May
- Institute of Microbiology & Infection and the School of Biosciences, University of Birmingham, Birmingham, United Kingdom
- National Institute of Health Research Surgical Reconstruction and Microbiology Research Centre, Queen Elizabeth Hospital, Birmingham, United Kingdom
| | - Scott G. Filler
- David Geffen School of Medicine at UCLA, Division of Infectious Diseases, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Los Angeles, California, United States of America
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Medicine, Duke University Medical Center, Durham, North Carolina, United States of America
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail: (DJS); (JH)
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32
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Janbon G, Ormerod KL, Paulet D, Byrnes EJ, Yadav V, Chatterjee G, Mullapudi N, Hon CC, Billmyre RB, Brunel F, Bahn YS, Chen W, Chen Y, Chow EWL, Coppée JY, Floyd-Averette A, Gaillardin C, Gerik KJ, Goldberg J, Gonzalez-Hilarion S, Gujja S, Hamlin JL, Hsueh YP, Ianiri G, Jones S, Kodira CD, Kozubowski L, Lam W, Marra M, Mesner LD, Mieczkowski PA, Moyrand F, Nielsen K, Proux C, Rossignol T, Schein JE, Sun S, Wollschlaeger C, Wood IA, Zeng Q, Neuvéglise C, Newlon CS, Perfect JR, Lodge JK, Idnurm A, Stajich JE, Kronstad JW, Sanyal K, Heitman J, Fraser JA, Cuomo CA, Dietrich FS. Analysis of the genome and transcriptome of Cryptococcus neoformans var. grubii reveals complex RNA expression and microevolution leading to virulence attenuation. PLoS Genet 2014; 10:e1004261. [PMID: 24743168 PMCID: PMC3990503 DOI: 10.1371/journal.pgen.1004261] [Citation(s) in RCA: 276] [Impact Index Per Article: 27.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2013] [Accepted: 02/07/2014] [Indexed: 02/07/2023] Open
Abstract
Cryptococcus neoformans is a pathogenic basidiomycetous yeast responsible for more than 600,000 deaths each year. It occurs as two serotypes (A and D) representing two varieties (i.e. grubii and neoformans, respectively). Here, we sequenced the genome and performed an RNA-Seq-based analysis of the C. neoformans var. grubii transcriptome structure. We determined the chromosomal locations, analyzed the sequence/structural features of the centromeres, and identified origins of replication. The genome was annotated based on automated and manual curation. More than 40,000 introns populating more than 99% of the expressed genes were identified. Although most of these introns are located in the coding DNA sequences (CDS), over 2,000 introns in the untranslated regions (UTRs) were also identified. Poly(A)-containing reads were employed to locate the polyadenylation sites of more than 80% of the genes. Examination of the sequences around these sites revealed a new poly(A)-site-associated motif (AUGHAH). In addition, 1,197 miscRNAs were identified. These miscRNAs can be spliced and/or polyadenylated, but do not appear to have obvious coding capacities. Finally, this genome sequence enabled a comparative analysis of strain H99 variants obtained after laboratory passage. The spectrum of mutations identified provides insights into the genetics underlying the micro-evolution of a laboratory strain, and identifies mutations involved in stress responses, mating efficiency, and virulence. Cryptococcus neoformans var. grubii is a major human pathogen responsible for deadly meningoencephalitis in immunocompromised patients. Here, we report the sequencing and annotation of its genome. Evidence for extensive intron splicing, antisense transcription, non-coding RNAs, and alternative polyadenylation indicates the potential for highly intricate regulation of gene expression in this opportunistic pathogen. In addition, detailed molecular, genetic, and genomic studies were performed to characterize structural features of the genome, including centromeres and origins of replication. Finally, the phenotypic and genome re-sequencing analysis of a collection of isolates of the reference H99 strain resulting from laboratory passage revealed that microevolutionary processes during in vitro culturing of pathogenic fungi can impact virulence.
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Affiliation(s)
- Guilhem Janbon
- Institut Pasteur, Unité Biologie et Pathogénicité Fongiques, Département Génomes et Génétique, Paris, France
- INRA, USC2019, Paris, France
- * E-mail: (GJ); (JH); (CAC); (FSD)
| | - Kate L. Ormerod
- University of Queensland, School of Chemistry and Molecular Biosciences, Brisbane, Queensland, Australia
| | - Damien Paulet
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et Génétique, Paris, France
| | - Edmond J. Byrnes
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | - Vikas Yadav
- Jawaharlal Nehru Centre for Advanced Scientific Research, Molecular Biology and Genetics Unit, Bangalore, India
| | - Gautam Chatterjee
- Jawaharlal Nehru Centre for Advanced Scientific Research, Molecular Biology and Genetics Unit, Bangalore, India
| | | | - Chung-Chau Hon
- Institut Pasteur, Unité Biologie Cellulaire du Parasitisme, Département Biologie Cellulaire et Infection, Paris, France
| | - R. Blake Billmyre
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | | | - Yong-Sun Bahn
- Yonsei University, Center for Fungal Pathogenesis, Department of Biotechnology, Seoul, Republic of Korea
| | - Weidong Chen
- Rutgers New Jersey Medical School, Department of Microbiology and Molecular Genetics, Newark, New Jersey, United States of America
| | - Yuan Chen
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | - Eve W. L. Chow
- University of Queensland, School of Chemistry and Molecular Biosciences, Brisbane, Queensland, Australia
| | - Jean-Yves Coppée
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et Génétique, Paris, France
| | - Anna Floyd-Averette
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | | | - Kimberly J. Gerik
- Washington University School of Medicine, Department of Molecular Microbiology, St. Louis, Missouri, United States of America
| | - Jonathan Goldberg
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Sara Gonzalez-Hilarion
- Institut Pasteur, Unité Biologie et Pathogénicité Fongiques, Département Génomes et Génétique, Paris, France
- INRA, USC2019, Paris, France
| | - Sharvari Gujja
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Joyce L. Hamlin
- University of Virginia, Department of Biochemistry and Molecular Genetics, Charlottesville, Virginia, United States of America
| | - Yen-Ping Hsueh
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
- California Institute of Technology, Division of Biology, Pasadena, California, United States of America
| | - Giuseppe Ianiri
- University of Missouri-Kansas City, School of Biological Sciences, Division of Cell Biology and Biophysics, Kansas City, Missouri, United States of America
| | - Steven Jones
- Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia, Canada
| | - Chinnappa D. Kodira
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | - Lukasz Kozubowski
- Clemson University, Department of Genetics and Biochemistry, Clemson, South Carolina, United States of America
| | - Woei Lam
- Washington University School of Medicine, Department of Molecular Microbiology, St. Louis, Missouri, United States of America
| | - Marco Marra
- Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia, Canada
| | - Larry D. Mesner
- University of Virginia, Department of Biochemistry and Molecular Genetics, Charlottesville, Virginia, United States of America
| | - Piotr A. Mieczkowski
- University of North Carolina, Department of Genetics, Chapel Hill, North Carolina, United States of America
| | - Frédérique Moyrand
- Institut Pasteur, Unité Biologie et Pathogénicité Fongiques, Département Génomes et Génétique, Paris, France
- INRA, USC2019, Paris, France
| | - Kirsten Nielsen
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
- University of Minnesota, Microbiology Department, Minneapolis, Minnesota, United States of America
| | - Caroline Proux
- Institut Pasteur, Plate-forme Transcriptome et Epigénome, Département Génomes et Génétique, Paris, France
| | | | - Jacqueline E. Schein
- Canada's Michael Smith Genome Sciences Centre, BC Cancer Agency, Vancouver, British Columbia, Canada
| | - Sheng Sun
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | - Carolin Wollschlaeger
- Institut Pasteur, Unité Biologie et Pathogénicité Fongiques, Département Génomes et Génétique, Paris, France
- INRA, USC2019, Paris, France
| | - Ian A. Wood
- University of Queensland, School of Mathematics and Physics, Brisbane, Queensland, Australia
| | - Qiandong Zeng
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
| | | | - Carol S. Newlon
- Rutgers New Jersey Medical School, Department of Microbiology and Molecular Genetics, Newark, New Jersey, United States of America
| | - John R. Perfect
- Duke University Medical Center, Duke Department of Medicine and Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
| | - Jennifer K. Lodge
- Washington University School of Medicine, Department of Molecular Microbiology, St. Louis, Missouri, United States of America
| | - Alexander Idnurm
- University of Missouri-Kansas City, School of Biological Sciences, Division of Cell Biology and Biophysics, Kansas City, Missouri, United States of America
| | - Jason E. Stajich
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
- University of California, Department of Plant Pathology & Microbiology, Riverside, California, United States of America
| | - James W. Kronstad
- Michael Smith Laboratories, Department of Microbiology and Immunology, Vancouver, British Columbia, Canada
| | - Kaustuv Sanyal
- Jawaharlal Nehru Centre for Advanced Scientific Research, Molecular Biology and Genetics Unit, Bangalore, India
| | - Joseph Heitman
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
- * E-mail: (GJ); (JH); (CAC); (FSD)
| | - James A. Fraser
- University of Queensland, School of Chemistry and Molecular Biosciences, Brisbane, Queensland, Australia
| | - Christina A. Cuomo
- Broad Institute of MIT and Harvard, Cambridge, Massachusetts, United States of America
- * E-mail: (GJ); (JH); (CAC); (FSD)
| | - Fred S. Dietrich
- Duke University Medical Center, Department of Molecular Genetics and Microbiology, Durham, North Carolina, United States of America
- * E-mail: (GJ); (JH); (CAC); (FSD)
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Microevolution during serial mouse passage demonstrates FRE3 as a virulence adaptation gene in Cryptococcus neoformans. mBio 2014; 5:e00941-14. [PMID: 24692633 PMCID: PMC3977352 DOI: 10.1128/mbio.00941-14] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Passage in mice of opportunistic pathogens such as Cryptococcus neoformans is known to increase virulence, but little is known about the molecular mechanisms involved in virulence adaptation. Serial mouse passage of nine environmental strains of serotype A C. neoformans identified two highly adapted virulent strains that showed a 4-fold reduction in time to death after four passages. Transcriptome sequencing expression studies demonstrated increased expression of a FRE3-encoded iron reductase in the two strains but not in a control strain that did not demonstrate increased virulence during mouse passage. FRE3 was shown to express an iron reductase activity and to play a role in iron-dependent growth of C. neoformans. Overexpression of FRE3 in the two original environmental strains increased growth in the macrophage cell line J774.16 and increased virulence. These data demonstrate a role for FRE3 in the virulence of C. neoformans and demonstrate how the increased expression of such a "virulence acquisition gene" during the environment-to-mammal transition, can optimize the virulence of environmental strains in mammalian hosts. IMPORTANCE Cryptococcus neoformans is a significant global fungal pathogen that also resides in the environment. Recent studies have suggested that the organism may undergo microevolution in the host. However, little is known about the permitted genetic changes facilitating the adaptation of environmental strains to mammalian hosts. The present studies subjected environmental strains isolated from several metropolitan areas of the United States to serial passages in mice. Transcriptome sequencing expression studies identified the increased expression of an iron reductase gene, FRE3, in two strains that adapted in mice to become highly virulent, and overexpression of FRE3 recapitulated the increased virulence after mouse passage. Iron reductase in yeast is important to iron uptake in a large number of microbial pathogens. These studies demonstrate the capacity of C. neoformans to show reproducible changes in the expression levels of small numbers of genes termed "virulence adaptation genes" to effectively increase pathogenicity during the environment-to-mammal transition.
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Alnuaimi AD, O'Brien-Simpson NM, Reynolds EC, McCullough MJ. Clinical isolates and laboratory referenceCandidaspecies and strains have varying abilities to form biofilms. FEMS Yeast Res 2013; 13:689-99. [DOI: 10.1111/1567-1364.12068] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2013] [Revised: 07/27/2013] [Accepted: 07/28/2013] [Indexed: 11/30/2022] Open
Affiliation(s)
- Ali D. Alnuaimi
- Melbourne Dental School; Oral Health CRC; The University of Melbourne; Melbourne; Vic.; Australia
| | - Neil M. O'Brien-Simpson
- Melbourne Dental School; Oral Health CRC; The University of Melbourne; Melbourne; Vic.; Australia
| | - Eric C. Reynolds
- Melbourne Dental School; Oral Health CRC; The University of Melbourne; Melbourne; Vic.; Australia
| | - Michael J. McCullough
- Melbourne Dental School; Oral Health CRC; The University of Melbourne; Melbourne; Vic.; Australia
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Serial passaging of Candida albicans in systemic murine infection suggests that the wild type strain SC5314 is well adapted to the murine kidney. PLoS One 2013; 8:e64482. [PMID: 23737985 PMCID: PMC3667833 DOI: 10.1371/journal.pone.0064482] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2012] [Accepted: 04/15/2013] [Indexed: 11/29/2022] Open
Abstract
The opportunistic fungal pathogen Candida albicans has a remarkable ability to adapt to unfavorable environments by different mechanisms, including microevolution. For example, a previous study has shown that passaging through the murine spleen can cause new phenotypic characteristics. Since the murine kidney is the main target organ in murine Candida sepsis and infection of the spleen differs from the kidney in several aspects, we tested whether C. albicans SC5314 could evolve to further adapt to infection and persistence within the kidney. Therefore, we performed a long-term serial passage experiment through the murine kidney of using a low infectious dose. We found that the overall virulence of the commonly used wild type strain SC5314 did not change after eight passages and that the isolated pools showed only very moderate changes of phenotypic traits on the population level. Nevertheless, the last passage showed a higher phenotypic variability and a few individual strains exhibited phenotypic alterations suggesting that microevolution has occurred. However, the majority of the tested single strains were phenotypically indistinguishable from SC5314. Thus, our findings indicate that characteristics of SC5314 which are important to establish and maintain kidney infection over a prolonged time are already well developed.
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Magditch DA, Liu TB, Xue C, Idnurm A. DNA mutations mediate microevolution between host-adapted forms of the pathogenic fungus Cryptococcus neoformans. PLoS Pathog 2012; 8:e1002936. [PMID: 23055925 PMCID: PMC3464208 DOI: 10.1371/journal.ppat.1002936] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2012] [Accepted: 08/15/2012] [Indexed: 11/30/2022] Open
Abstract
The disease cryptococcosis, caused by the fungus Cryptococcus neoformans, is acquired directly from environmental exposure rather than transmitted person-to-person. One explanation for the pathogenicity of this species is that interactions with environmental predators select for virulence. However, co-incubation of C. neoformans with amoeba can cause a “switch” from the normal yeast morphology to a pseudohyphal form, enabling fungi to survive exposure to amoeba, yet conversely reducing virulence in mammalian models of cryptococcosis. Like other human pathogenic fungi, C. neoformans is capable of microevolutionary changes that influence the biology of the organism and outcome of the host-pathogen interaction. A yeast-pseudohyphal phenotypic switch also happens under in vitro conditions. Here, we demonstrate that this morphological switch, rather than being under epigenetic control, is controlled by DNA mutation since all pseudohyphal strains bear mutations within genes encoding components of the RAM pathway. High rates of isolation of pseudohyphal strains can be explained by the physical size of RAM pathway genes and a hypermutator phenotype of the strain used in phenotypic switching studies. Reversion to wild type yeast morphology in vitro or within a mammalian host can occur through different mechanisms, with one being counter-acting mutations. Infection of mice with RAM mutants reveals several outcomes: clearance of the infection, asymptomatic maintenance of the strains, or reversion to wild type forms and progression of disease. These findings demonstrate a key role of mutation events in microevolution to modulate the ability of a fungal pathogen to cause disease. Many diseases are contracted from the environment, rather than from sick people. It is unclear why those species are able to cause disease, since the selective pressures in the environment are presumed to be very different from those found within the host. Cryptococcus neoformans is a fungus that causes life-threatening lung and central nervous system disease in approximately one million people each year. The fungus is inhaled from environmental sources. One hypothesis to account for C. neoformans virulence is that amoeba are predators for this fungus, and surviving strains are pre-selected to be virulent in the human host. On the other hand, experiments have found that amoeba eat C. neoformans. A pseudohyphal cell type can survive, and while protecting against amoeba these cells are unable to cause disease in mouse models. We predicted that the pseudohyphal morphology reflected a change in function of a pathway of genes, and found that all pseudohyphal isolates contain mutations within genes for this pathway. The pseudohyphal trait is unstable, with reversion to normal yeast growth by counter-acting mutations. These mutations can occur during the course of mammalian infection. Our results show that mutation events account for a microevolution system currently described as phenotypic switching, and that mutations, at least under experimental conditions, can regulate pathogen adaptation and influence its host range.
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Affiliation(s)
- Denise A. Magditch
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri, United States of America
| | - Tong-Bao Liu
- Public Health Research Institute Center, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
| | - Chaoyang Xue
- Public Health Research Institute Center, University of Medicine and Dentistry of New Jersey, Newark, New Jersey, United States of America
| | - Alexander Idnurm
- Division of Cell Biology and Biophysics, School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri, United States of America
- * E-mail:
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Hu G, Wang J, Choi J, Jung WH, Liu I, Litvintseva AP, Bicanic T, Aurora R, Mitchell TG, Perfect JR, Kronstad JW. Variation in chromosome copy number influences the virulence of Cryptococcus neoformans and occurs in isolates from AIDS patients. BMC Genomics 2011; 12:526. [PMID: 22032296 PMCID: PMC3221739 DOI: 10.1186/1471-2164-12-526] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2011] [Accepted: 10/27/2011] [Indexed: 11/25/2022] Open
Abstract
Background The adaptation of pathogenic fungi to the host environment via large-scale genomic changes is a poorly characterized phenomenon. Cryptococcus neoformans is the leading cause of fungal meningoencephalitis in HIV/AIDS patients, and we recently discovered clinical strains of the fungus that are disomic for chromosome 13. Here, we examined the genome plasticity and phenotypes of monosomic and disomic strains, and compared their virulence in a mouse model of cryptococcosis Results In an initial set of strains, melanin production was correlated with monosomy at chromosome 13, and disomic variants were less melanized and attenuated for virulence in mice. After growth in culture or passage through mice, subsequent strains were identified that varied in melanin formation and exhibited copy number changes for other chromosomes. The correlation between melanin and disomy at chromosome 13 was observed for some but not all strains. A survey of environmental and clinical isolates maintained in culture revealed few occurrences of disomic chromosomes. However, an examination of isolates that were freshly collected from the cerebrospinal fluid of AIDS patients and minimally cultured provided evidence for infections with multiple strains and copy number variation. Conclusions Overall, these results suggest that the genome of C. neoformans exhibits a greater degree of plasticity than previously appreciated. Furthermore, the expression of an essential virulence factor and the severity of disease are associated with genome variation. The occurrence of chromosomal variation in isolates from AIDS patients, combined with the observed influence of disomy on virulence, indicates that genome plasticity may have clinical relevance.
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Affiliation(s)
- Guanggan Hu
- The Michael Smith Laboratories, Department of Microbiology and Immunology, and Faculty of Land and Food Systems, University of British Columbia, Vancouver, B.C. V6T 1Z4, Canada
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Stie J, Fox D. Blood-brain barrier invasion by Cryptococcus neoformans is enhanced by functional interactions with plasmin. MICROBIOLOGY-SGM 2011; 158:240-258. [PMID: 21998162 DOI: 10.1099/mic.0.051524-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Cryptococcus neoformans can invade the central nervous system through diverse mechanisms. We examined a possible role for host plasma proteases in the neurotropic behaviour of this blood-borne fungal pathogen. Plasminogen is a plasma-enriched zymogen that can passively coat the surface of blood-borne pathogens and, upon conversion to the serine protease plasmin, facilitate pathogen dissemination by degrading vascular barriers. In this study, plasminogen-to-plasmin conversion on killed and viable hypoencapsulated strains of C. neoformans required the addition of plasminogen activator (PA), but this conversion occurred in the absence of supplemented PA when viable strains were cultured with brain microvascular endothelial cells (BMEC). Plasmin-coated C. neoformans showed an enhanced invasive ability in Matrigel invasion assays that was significantly augmented in the presence of BMEC. The invasive effect of plasmin required viable pathogen and correlated with rapid declines in BMEC barrier function. Plasmin-enhanced invasion was inhibited by aprotinin, carboxypeptidase B, the lysine analogue epsilon-aminocaproic acid, and by capsule development. C. neoformans caused plasminogen-independent declines in BMEC barrier function that were associated with pathogen-induced host damage; however, such declines were significantly delayed and less extensive than those observed with plasmin-coated pathogen. BMEC adhesion and damage by hypoencapsulated C. neoformans were diminished by capsule induction but unaltered by plasminogen and/or PA. We conclude that hypoencapsulated C. neoformans can invade BMEC by a plasmin-dependent mechanism, in vitro, and that small, or minimal, surface capsule expression during the blood-borne phase of cryptococcosis may promote virulence by means of plasmin(ogen) acquisition.
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Affiliation(s)
- Jamal Stie
- Research Institute for Children, Louisiana State University Health Sciences Center, New Orleans, LA 70118, USA
| | - Deborah Fox
- Department of Pediatrics, Louisiana State University Health Sciences Center, New Orleans, LA 70118, USA.,Research Institute for Children, Louisiana State University Health Sciences Center, New Orleans, LA 70118, USA
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Pedroso RS, Lavrador MA, Ferreira JC, Candido RC, Maffei CM. Cryptococcus neoformans var. grubii - Pathogenicity of environmental isolates correlated to virulence factors, susceptibility to fluconazole and molecular profile. Mem Inst Oswaldo Cruz 2011; 105:993-1000. [PMID: 21225196 DOI: 10.1590/s0074-02762010000800008] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2010] [Accepted: 10/27/2010] [Indexed: 12/14/2022] Open
Abstract
The pathogenicity of Cryptococcus neoformans is heterogeneous and is associated with the expression of virulence factors. This study aimed to correlate the pathogenicity of C. neoformans var. grubii in BALB/c mice with in vitro virulence factors, fluconazole minimal inhibitory concentrations (MICs) and molecular profiles, before and after animal passage. Ten environmental isolates and one ATCC strain of C. neoformans var. grubii mating type α were evaluated. Most isolates (91%) killed 50% or more of the infected animals by day 24 postinfection and were recovered from the lungs and brains of surviving animals on days 7 and 14 postinfection. The burden of yeast in the lungs was more variable than that in the brain. The differences in the expression of virulence factors (growth at 37ºC, presence and size of the capsule and production of melanin, urease, proteinase and phospholipase) by most isolates pre and postpassage in animals were not statistically significant. The fluconazole MICs in postpassaged lines differed by a one-dilution from the MIC of the corresponding prepassaged line for six isolates. Using molecular typing [polymerase chain reaction-fingerprinting with (GACA)4 and M13], eight isolates were identified as VNI and three as VNII. We concluded that different isolates with the same molecular and phenotypic profiles, including isolates that are markedly hypervirulent, span a wide range of virulence and there were no changes in virulence factors in the postpassaged lines when compared with the corresponding nonpassaged lines.
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Affiliation(s)
- Reginaldo S Pedroso
- Escola Técnica de Saúde, Universidade Federal de Uberlândia, Uberlândia, MG, Brasil, 38400-902.
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40
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Acid tolerant mutants of Bifidobacterium animalis subsp. lactis with improved stability in fruit juice. Lebensm Wiss Technol 2011. [DOI: 10.1016/j.lwt.2010.11.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Ngamskulrungroj P, Serena C, Gilgado F, Malik R, Meyer W. Global VGIIa isolates are of comparable virulence to the major fatal Cryptococcus gattii Vancouver Island outbreak genotype. Clin Microbiol Infect 2011; 17:251-8. [PMID: 20331682 DOI: 10.1111/j.1469-0691.2010.03222.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The ongoing cryptococcosis outbreak on Vancouver Island, BC, Canada, is caused by two VGII sub-genotypes of the primary pathogen, Cryptococcus gattii: VGIIa isolates predominate, whereas VGIIb isolates are rare. Although higher virulence of the VGIIa genotype has been proposed, an unresolved key question is whether VGIIa isolates from other regions are also more virulent than VGIIb isolates. We report the relationship between genotype and virulence for a global collection of C. gattii VGIIa and VGIIb isolates (from Australia, Argentina, Brazil, Canada, Thailand and the USA). In vitro and in vivo virulence studies were conducted. At 37°C, growth [at 18 h: 0.2 optical density (OD) difference, p 0.026; at 36 h: 0.6 OD difference, p 0.036) and mean melanin production (OD = 0.25 vs. OD = 0.15, p 0.059] of VGIIa isolates was greater than that of VGIIb isolates. The inhibitory effect of high temperature on melanin production of VGIIa isolates was less than that of VGIIb isolates (OD = 0.36 vs. OD = 0.69; p 0.001). Capsule production at 37°C of VGIIa isolates was less than that of VGIIb isolates. All VGIIa isolates were fertile, whereas only 17% of VGIIb isolates were fertile (p <0.001). In vivo virulence studies using the BALB/c mice nasal inhalation model revealed that VGIIa isolates were more virulent than VGIIb isolates (p <0.001) independent of their clinical (p 0.003) or environmental origin (p <0.001). This study established a clear association between genotype and virulence of the primary fungal pathogen, C. gattii.
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Affiliation(s)
- P Ngamskulrungroj
- Molecular Mycology Research Laboratory, Centre for Infectious Disease and Microbiology, Westmead Millennium Institute, Westmead Hospital, Sydney Medical School - Westmead, The University of Sydney, Westmead, NSW, Australia
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Harun A, Serena C, Gilgado F, Chen SCA, Meyer W. Scedosporium aurantiacum is as virulent as S. prolificans, and shows strain-specific virulence differences, in a mouse model. Med Mycol 2011; 48 Suppl 1:S45-51. [PMID: 21067330 DOI: 10.3109/13693786.2010.517224] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Several Scedosporium species are clinically important emerging pathogens. Scedosporium prolificans is reported to be the most virulent of the species, while the recently described species Scedosporium aurantiacum, which accounts for a substantial proportion of Australian clinical isolates is capable of causing a range of serious infections. In addition, environmental surveys have revealed a high prevalence of S. aurantiacum in the urban Sydney region. This study was conducted to assess the virulence of selected S. aurantiacum strains recovered from patients who are colonized or have invasive disease, as well as those from environmental sources, in comparison with S. prolificans. PCR fingerprinting with the primer M13 revealed high genetic variation among the S. aurantiacum strains. We evaluated the virulence of eight S. aurantiacum and two S. prolificans strains in a murine model using an infectious dose of 2 × 10⁵ conidia. S. aurantiacum was noted to be as virulent as S. prolificans, causing death in 60-100% of mice (P > 0.05). There were significant strain-specific virulence differences (P < 0.005), indicating a possible link between genotype and virulence in S. aurantiacum.
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Affiliation(s)
- Azian Harun
- Centre for Infectious Diseases and Microbiology, Westmead Hospital, Westmead Millennium Institute, The University of Sydney, Australia
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43
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Olszewski MA, Zhang Y, Huffnagle GB. Mechanisms of cryptococcal virulence and persistence. Future Microbiol 2010; 5:1269-88. [PMID: 20722603 DOI: 10.2217/fmb.10.93] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Cryptococcus neoformans is an environmental yeast that is a leading cause of fatal mycosis in AIDS patients and a major cause of meningoencephalitis and CNS-related mortality around the globe. Although C. neoformans infection is mostly a manifestation of immune deficiency, up to 25% of cases reported in the USA occur in patients without recognizable immune defects, indicating that C. neoformans can develop mechanisms that allow it to evade immune defenses and persist in noncompromised hosts. This article discusses mechanisms and routes of infection and the most important elements of host response as well as the mechanisms that promote cryptococcal survival within the host. Metabolic adaptation to physiological host conditions and the mechanisms limiting immune recognition, interfering with phagocytosis and extending intracellular survival of C. neoformans are highlighted. We describe the mechanisms by which C. neoformans can alter adaptive host responses, especially cell-mediated immunity, which is required for clearance of this microbe. We also review cryptococcal strategies of survival in the CNS and briefly discuss adaptations developing in response to medical treatment.
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Affiliation(s)
- Michal A Olszewski
- Ann Arbor Veterans Administration Health System (11R), 2215 Fuller Road, Ann Arbor, MI 48105, USA.
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St'ovíček V, Váchová L, Kuthan M, Palková Z. General factors important for the formation of structured biofilm-like yeast colonies. Fungal Genet Biol 2010; 47:1012-22. [PMID: 20728557 DOI: 10.1016/j.fgb.2010.08.005] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2010] [Revised: 08/06/2010] [Accepted: 08/11/2010] [Indexed: 12/30/2022]
Abstract
The lifestyle of wild and laboratory yeast strains significantly differs. In contrast to the smooth colonies of laboratory strains, wild Saccharomyces cerevisiae strains form biofilm-like, strikingly structured colonies possessing distinctive traits enabling them to better survive in hostile environments in the wild. Here, comparing three sets of strains forming differently structured colonies (fluffy, semi-fluffy and smooth), each derived from ancestors with distinct genetic backgrounds isolated from natural settings (BR-88, BR-99 and BR-103), we specified the factors essential for the formation of structured colonies, i.e. for the lifestyle most likely to be preferred in the wild. The ability to form an abundant extracellular matrix (ECM) is one of the features typical for structured colonies. ECM influences colony architecture and many other physiological properties, such as the capability to retain water in a 2-fold surplus to wet cell biomass. ECM composition, however, differs among distinct strains, depending on their particular genetic background. We further show that the expression of certain genes (AQY1, FLO11) is also strictly related to the particular colony morphology, being highest in the most structured colonies. Flo11p adhesin, important for cell-cell and cell-surface adhesion, is essential for the formation of fluffy colonies and thus significantly contributes to the phenotype variability of wild yeast strains. On the other hand, surprisingly, neither the cell shape nor budding pattern nor the ability to form pseudohyphae directly influences the formation of three-dimensional fluffy colony architecture.
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Affiliation(s)
- Vratislav St'ovíček
- Department of Genetics and Microbiology, Faculty of Science, Charles University in Prague, Viničná 5, Prague 2, Czech Republic
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45
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Gupta G, Fries BC. Variability of phenotypic traits in Cryptococcus varieties and species and the resulting implications for pathogenesis. Future Microbiol 2010; 5:775-87. [PMID: 20441549 DOI: 10.2217/fmb.10.44] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Variability of phenotypic characteristics in Cryptococcus neoformans var. grubii and var. neoformans as well as Cryptococcus gattii can have diverse effects on the virulence of these fungi and are thus important for pathogenesis. This article summarizes the diverse phenotypic changes that these fungi can manifest. We divide changes into those that affect the entire fungal population and are predominantly induced by environmental signals, and those that involve subpopulations of the fungal population and have to be selected. Last, the article summarizes the experimental evidence that epitopes on the polysaccharide capsule also vary, which may have implications for the pathogenesis as these findings would further diversify the fungal population.
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Affiliation(s)
- Gunjan Gupta
- Department of Medicine, Albert Einstein College of Medicine, Bronx, NY, USA
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46
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Mixed infections and In Vivo evolution in the human fungal pathogen Cryptococcus neoformans. mBio 2010; 1. [PMID: 20689742 PMCID: PMC2912664 DOI: 10.1128/mbio.00091-10] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2010] [Accepted: 03/31/2010] [Indexed: 01/05/2023] Open
Abstract
Koch's postulates are criteria establishing a causal relationship between a microbe and a disease that lead to the assumption that diseases are caused by a single strain or its evolved forms. Cryptococcus neoformans is a life-threatening human fungal pathogen responsible for an estimated 1 million cases of cryptococcosis/year, predominantly meningoencephalitis. To assess the molecular diversity of clinical isolates and gain knowledge of C. neoformans biology in the host, we analyzed clinical cultures collected during the prospective CryptoA/D study. Using molecular analysis of unpurified isolates, we demonstrated that mixed infections in humans are more common than previously thought, occurring in almost 20% of patients diagnosed with cryptococcosis. These mixed infections are composed of different mating types, serotypes, and/or genotypes. We also identified genetically related haploid and diploid strains in the same patients. Experimental infections and quantitative PCR show that these ploidy changes can result from endoreplication (duplication of DNA content) and that shuttling between haploid and diploid states can occur, suggesting in vivo evolution. Thus, the concept of one strain/one infection does not hold true for C. neoformans and may apply to other environmentally acquired fungal pathogens. Furthermore, the possibility of mixed and/or evolving infections should be taken into account when developing therapeutic strategies against these pathogens.
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Comparison of genotypes between environmental and clinical isolates of Cryptococcus neoformans var. grubii based on microsatellite patterns. Mycopathologia 2010; 169:47-55. [PMID: 19680781 DOI: 10.1007/s11046-009-9230-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2009] [Accepted: 07/28/2009] [Indexed: 10/20/2022]
Abstract
We applied multilocus microsatellite typing (MLMT) method to investigate the genetic relation between Cryptococcus neoformans var. grubii clinical and environmental isolates in São Paulo, Brazil. This MLMT method includes three functional gene sequences of C. neoformans var. grubii, which are dispersed on three chromosomes. In all, 89 strains (36 clinical and 53 environmental isolates) were analyzed. Of 36 clinical strains, 20 belonged to a major type of MLMT-13 (55.6%). They were mainly isolated from clinical specimens. About 52.8% of strains from the environment belong to a major type of MLMT-36, which are indigenous to environments and which were not isolated from clinical samples. Thus, we recognized two genotypes that distinguish majority of clinical and environmental strains. No differences were found in antifungal susceptibility and capsule size between major environmental and clinical MLMT types.
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Cryptococcus neoformans variants generated by phenotypic switching differ in virulence through effects on macrophage activation. Infect Immun 2010; 78:1049-57. [PMID: 20048044 DOI: 10.1128/iai.01049-09] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Macrophages have a central role in the pathogenesis of cryptococcosis since they are an important line of defense, serve as a site for fungal replication, and also can contribute to tissue damage. The objective of this study was to investigate the interaction of macrophages with cells from smooth-colony variants (SM) and mucoid-colony variants (MC) arising from phenotypic switching of Cryptococcus neoformans. Alveolar macrophages (AMs) isolated from SM- and MC-infected mice exhibited differences in gene and surface expression of PD-L1, PD-L2, and major histocompatibility class II (MHC-II). PD-L1 and PD-L2 are the ligands for PD1 and are differentially regulated in Th1- and Th2-type cells. In addition, macrophage activation in SM- and MC-infected mice was characterized as alternatively activated. Flow cytometric and cytokine analysis demonstrated that MC infection was associated with the emergence of Th17 cells and higher levels of interleukin-17 (IL-17) in lung tissue, which were reduced by AM depletion. In conclusion, our results indicate that macrophages play a significant role in maintaining damage-promoting inflammation in the lung during MC infection, which ultimately results in death.
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Doering TL. How sweet it is! Cell wall biogenesis and polysaccharide capsule formation in Cryptococcus neoformans. Annu Rev Microbiol 2009; 63:223-47. [PMID: 19575556 DOI: 10.1146/annurev.micro.62.081307.162753] [Citation(s) in RCA: 166] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Cryptococcus neoformans is a pathogenic fungus responsible for severe opportunistic infections. The most prominent feature of this yeast is its elaborate polysaccharide capsule, a complex structure that is required for virulence. The capsule is intimately associated with the cell wall, which underlies the capsule and offers the organism strength and flexibility in potentially hostile environments. Both structures are primarily composed of polysaccharides, offering a glimpse of the tremendous variation inherent in natural carbohydrate structures and their multiple biological functions. The steps in cell wall and capsule biosynthesis and assembly pose fascinating questions of metabolism, enzymology, cell biology, and regulation; the answers have potential application to treatment of a deadly infection. This article reviews current knowledge of cryptococcal cell wall and capsule biosynthesis and outstanding questions for the future.
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Affiliation(s)
- Tamara Lea Doering
- Department of Molecular Microbiology, Washington University Medical School, St. Louis, Missouri, USA.
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Isolation and characterization of senescent Cryptococcus neoformans and implications for phenotypic switching and pathogenesis in chronic cryptococcosis. EUKARYOTIC CELL 2009; 8:858-66. [PMID: 19411622 DOI: 10.1128/ec.00017-09] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Although several virulence factors and associated genes have been identified, the mechanisms that allow Cryptococcus neoformans to adapt during chronic infection and to persist in immunocompromised hosts remain poorly understood. Characterization of senescent cells of C. neoformans demonstrated that these cells exhibit a significantly enlarged cell body and capsule but still cross the blood-brain barrier. C. neoformans cells with advanced generational age are also more resistant to phagocytosis and killing by antifungals, which could promote their selection during chronic disease in humans. Senescent cells of RC-2, a C. neoformans strain that undergoes phenotypic switching, manifest switching rates up to 11-fold higher than those of younger cells. Infection experiments with labeled cells suggest that senescent yeast cells can potentially accumulate in vivo. Mathematical modeling incorporating different switching rates demonstrates how increased switching rates promote the emergence of hypervirulent mucoid variants during chronic infection. Our findings introduce the intriguing concept that senescence in eukaryotic pathogens could be a mechanism of microevolution that may promote pathoadaptation and facilitate evasion of an evolving immune response.
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