51
|
Fu C, Davy A, Holmes S, Sun S, Yadav V, Gusa A, Coelho MA, Heitman J. Dynamic genome plasticity during unisexual reproduction in the human fungal pathogen Cryptococcus deneoformans. PLoS Genet 2021; 17:e1009935. [PMID: 34843473 PMCID: PMC8670703 DOI: 10.1371/journal.pgen.1009935] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2021] [Revised: 12/14/2021] [Accepted: 11/08/2021] [Indexed: 12/30/2022] Open
Abstract
Genome copy number variation occurs during each mitotic and meiotic cycle and it is crucial for organisms to maintain their natural ploidy. Defects in ploidy transitions can lead to chromosome instability, which is a hallmark of cancer. Ploidy in the haploid human fungal pathogen Cryptococcus neoformans is exquisitely orchestrated and ranges from haploid to polyploid during sexual development and under various environmental and host conditions. However, the mechanisms controlling these ploidy transitions are largely unknown. During C. deneoformans (formerly C. neoformans var. neoformans, serotype D) unisexual reproduction, ploidy increases prior to the onset of meiosis, can be independent from cell-cell fusion and nuclear fusion, and likely occurs through an endoreplication pathway. To elucidate the molecular mechanisms underlying this ploidy transition, we identified twenty cell cycle-regulating genes encoding cyclins, cyclin-dependent kinases (CDK), and CDK regulators. We characterized four cyclin genes and two CDK regulator genes that were differentially expressed during unisexual reproduction and contributed to diploidization. To detect ploidy transition events, we generated a ploidy reporter, called NURAT, which can detect copy number increases via double selection for nourseothricin-resistant, uracil-prototrophic cells. Utilizing this ploidy reporter, we showed that ploidy transition from haploid to diploid can be detected during the early phases of unisexual reproduction. Interestingly, selection for the NURAT reporter revealed several instances of segmental aneuploidy of multiple chromosomes, which conferred azole resistance in some isolates. These findings provide further evidence of ploidy plasticity in fungi with significant biological and public health implications. Ploidy is an intrinsic fundamental feature of all eukaryotic organisms, and ploidy variation and maintenance are critical to the organism survival and evolution. Fungi exhibit exquisite plasticity in ploidy variation in adaptation to various environmental stresses. For example, the haploid opportunistic human fungal pathogen C. deneoformans can generate diploid blastospores during unisexual reproduction and also forms polyploid titan cells during host infection; however, the mechanisms underlying these ploidy transitions are largely unknown. In this study, we elucidated the genetic regulatory circuitry governing ploidy duplication during C. deneoformans unisexual reproduction through the identification and characterization of cell cycle regulators that are differentially expressed during unisexual reproduction. We showed that four cyclin and two cyclin-dependent kinase regulator genes function in concert to orchestrate ploidy transition during unisexual reproduction. To trace and track ploidy transition events, we also generated a ploidy reporter and revealed the formation of segmental aneuploidy in addition to diploidization, illustrating the diverse mechanisms of genome plasticity in C. deneoformans.
Collapse
Affiliation(s)
- Ci Fu
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Aaliyah Davy
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Simeon Holmes
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Vikas Yadav
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Asiya Gusa
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Marco A. Coelho
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
52
|
The Cyclin Cln1 Controls Polyploid Titan Cell Formation following a Stress-Induced G 2 Arrest in Cryptococcus. mBio 2021; 12:e0250921. [PMID: 34634930 PMCID: PMC8510536 DOI: 10.1128/mbio.02509-21] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
The pathogenic yeast Cryptococcus neoformans produces polyploid titan cells in response to the host lung environment that are critical for host adaptation and subsequent disease. We analyzed the in vivo and in vitro cell cycles to identify key aspects of the C. neoformans cell cycle that are important for the formation of titan cells. We identified unbudded 2C cells, referred to as a G2 arrest, produced both in vivo and in vitro in response to various stresses. Deletion of the nonessential cyclin Cln1 resulted in overproduction of titan cells in vivo and transient morphology defects upon release from stationary phase in vitro. Using a copper-repressible promoter PCTR4-CLN1 strain and a two-step in vitro titan cell formation assay, our in vitro studies revealed Cln1 functions after the G2 arrest. These studies highlight unique cell cycle alterations in C. neoformans that ultimately promote genomic diversity and virulence in this important fungal pathogen.
Collapse
|
53
|
Adenylyl Cyclase and Protein Kinase A Play Redundant and Distinct Roles in Growth, Differentiation, Antifungal Drug Resistance, and Pathogenicity of Candida auris. mBio 2021; 12:e0272921. [PMID: 34663094 PMCID: PMC8524339 DOI: 10.1128/mbio.02729-21] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Candida auris is a globally emerging multidrug-resistant fungal pathogen. Its pathogenicity-related signaling networks are largely unknown. Here, we characterized the pathobiological functions of the cyclic AMP (cAMP)/protein kinase A (PKA) signaling pathway in C. auris. We focused on adenylyl cyclase (CYR1), the PKA regulatory subunit (BCY1), and the PKA catalytic subunits (TPK1 and TPK2). We concluded that PKA acts both dependently and independently of Cyr1 in C. auris. Tpk1 and Tpk2 have major and minor roles, respectively, in PKA activity and functions. Both Cyr1 and PKA promote growth, thermotolerance, filamentous growth, and resistance to stress and antifungal drugs by regulating expression of multiple effector genes. In addition, Cyr1 and PKA subunits were involved in disinfectant resistance of C. auris. However, deletion of both TPK1 and TPK2 generally resulted in more severe defects than CYR1 deletion, indicating that Cyr1 and PKA play redundant and distinct roles. Notably, Tpk1 and Tpk2 have redundant but Cyr1-independent roles in haploid-to-diploid cell transition, which increases virulence of C. auris. However, Tpk1 and Tpk2 often play opposing roles in formation of biofilms and the cell wall components chitin and chitosan. Surprisingly, deletion of CYR1 or TPK1/TPK2, which resulted in severe in vitro growth defects at 37°C, did not attenuate virulence, and BCY1 deletion reduced virulence of C. auris in a systemic murine infection model. In conclusion, this study provides comprehensive insights into the role of the cAMP/PKA pathway in drug resistance and pathogenicity of C. auris and suggests a potential therapeutic option for treatment of C. auris-mediated candidemia.
Collapse
|
54
|
Cell Wall Integrity Pathway Involved in Morphogenesis, Virulence and Antifungal Susceptibility in Cryptococcus neoformans. J Fungi (Basel) 2021; 7:jof7100831. [PMID: 34682253 PMCID: PMC8540506 DOI: 10.3390/jof7100831] [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: 09/01/2021] [Revised: 09/28/2021] [Accepted: 09/30/2021] [Indexed: 11/17/2022] Open
Abstract
Due to its location, the fungal cell wall is the compartment that allows the interaction with the environment and/or the host, playing an important role during infection as well as in different biological functions such as cell morphology, cell permeability and protection against stress. All these processes involve the activation of signaling pathways within the cell. The cell wall integrity (CWI) pathway is the main route responsible for maintaining the functionality and proper structure of the cell wall. This pathway is highly conserved in the fungal kingdom and has been extensively characterized in Saccharomyces cerevisiae. However, there are still many unknown aspects of this pathway in the pathogenic fungi, such as Cryptococcus neoformans. This yeast is of particular interest because it is found in the environment, but can also behave as pathogen in multiple organisms, including vertebrates and invertebrates, so it has to adapt to multiple factors to survive in multiple niches. In this review, we summarize the components of the CWI pathway in C. neoformans as well as its involvement in different aspects such as virulence factors, morphological changes, and its role as target for antifungal therapies among others.
Collapse
|
55
|
Reis FCG, Gimenez B, Jozefowicz LJ, Castelli RF, Martins ST, Alves LR, de Oliveira HC, Rodrigues ML. Analysis of Cryptococcal Extracellular Vesicles: Experimental Approaches for Studying Their Diversity Among Multiple Isolates, Kinetics of Production, Methods of Separation, and Detection in Cultures of Titan Cells. Microbiol Spectr 2021; 9:e0012521. [PMID: 34346749 PMCID: PMC8552642 DOI: 10.1128/spectrum.00125-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2021] [Accepted: 07/12/2021] [Indexed: 11/20/2022] Open
Abstract
Extracellular vesicles (EVs) produced by members of the Cryptococcus genus are associated with fundamental processes of fungal physiology and virulence. However, several questions about the properties of cryptococcal EVs remain unanswered, mostly because of technical limitations. We recently described a fast and efficient protocol of high-yield EV isolation from solid medium. In this study, we aimed at using the solid medium protocol to address some of the open questions about EVs, including the kinetics of EV production, the diversity of EVs produced by multiple isolates under different culture conditions, the separation of vesicles in a density gradient followed by the recovery of functional EVs, the direct detection of EVs in culture supernatants, and the production of vesicles in solid cultures of Titan cells. Our results indicate that the production of EVs is directly impacted by the culture medium and time of growth, resulting in variable detection of EVs per cell and a peak of EV detection at 24 h of growth. Nanoparticle tracking analysis (NTA) of EV samples revealed that multiple isolates produce vesicles with variable properties, including particles of diverging dimensions. EVs were produced in the solid medium in amounts that were separated on a centrifugation density gradient, resulting in the recovery of functional EVs containing the major cryptococcal capsular antigen. We also optimized the solid medium protocol for induction of the formation of Titan cells, and analyzed the production of EVs by NTA and transmission electron microscopy. This analysis confirmed that EVs were isolated from solid cultures of cryptococcal enlarged cells. With these approaches, we expect to implement simple methods that will facilitate the analysis of EVs produced by fungal cells. IMPORTANCE Fungal extracellular vesicles (EVs) are considered to be important players in the biology of fungal pathogens. However, the limitations in the methodological approaches to studying fungal EVs impair the expansion of knowledge in this field. In the present study, we used the Cryptococcus genus as a model for the study of EVs. We explored the simplification of protocols for EV analysis, which helped us to address some important, but still unanswered, questions about fungal EVs.
Collapse
Affiliation(s)
- Flavia C. G. Reis
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
- Centro de Desenvolvimento Tecnológico em Saúde (CDTS), Fiocruz, Rio de Janeiro, Brazil
| | - Bianca Gimenez
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
| | | | - Rafael F. Castelli
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
| | - Sharon T. Martins
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
| | - Lysangela R. Alves
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
| | | | - Marcio L. Rodrigues
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (Fiocruz), Curitiba, Brazil
- Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
| |
Collapse
|
56
|
Abstract
Members of the Cryptococcus species complex stand out by unique virulence factors that allowed evolutionary transition to pathogenesis. Among the factors contributing to cryptococcosis is a morphological transformation into giant (Titan) cells. It remains unclear whether species outside of the C. neoformans/C. gattii species complex are capable of titanization. We utilized two recently developed protocols that allow obtaining Titan cells in vitro to test if titanization occurs in non-C. neoformans/C. gattii species. We find that none of the tested strains, representing 10 species of basidiomycetous yeasts and the ascomycetous yeast Saccharomyces cerevisiae, undergo significant titanization under conditions that promote robust Titan cell formation in C. neoformans/C. gattii species complex. C. terreus formed occasional enlarged cells through a mechanism potentially similar to that of titanization. Our findings suggest that titanization is a rare phenomenon among basidiomycetous yeasts that occurs mostly in members of the C. neoformans/C. gattii species complex.
Collapse
Affiliation(s)
- Mariusz Dyląg
- Department of Genetics and Biochemistry, Eukaryotic Pathogens Innovation Center, Clemson University , Clemson, SC, USA
| | - Rodney J Colon-Reyes
- Department of Genetics and Biochemistry, Eukaryotic Pathogens Innovation Center, Clemson University , Clemson, SC, USA
| | - Lukasz Kozubowski
- Department of Genetics and Biochemistry, Eukaryotic Pathogens Innovation Center, Clemson University , Clemson, SC, USA
| |
Collapse
|
57
|
Maufrais C, de Oliveira L, Bastos RW, Moyrand F, Reis FCG, Valero C, Gimenez B, Josefowicz LJ, Goldman GH, Rodrigues ML, Janbon G. Population genomic analysis of Cryptococcus Brazilian isolates reveals an African type subclade distribution. G3 (BETHESDA, MD.) 2021; 11:jkab107. [PMID: 33822048 PMCID: PMC8495746 DOI: 10.1093/g3journal/jkab107] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/10/2021] [Accepted: 03/29/2021] [Indexed: 12/22/2022]
Abstract
The genomes of a large number of Cryptococcus neoformans isolates have been sequenced and analyzed in recent years. These genomes have been used to understand the global population structure of this opportunistic pathogen. However, only a small number of South American isolates have been considered in these studies, and the population structure of C. neoformans in this part of the world remains elusive. Here, we analyzed the genomic sequences of 53 Brazilian Cryptococcus isolates and deciphered the C. neoformans population structure in this country. Our data reveal an African-like structure that suggested repeated intercontinental transports from Africa to South America. We also identified a mutator phenotype in one VNBII Brazilian isolate, exemplifying how fast-evolving isolates can shape the Cryptococcus population structure. Finally, phenotypic analyses revealed wide diversity but not lineage specificity in the expression of classical virulence traits within the set of isolates.
Collapse
Affiliation(s)
- Corinne Maufrais
- Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Institut Pasteur, F-75015 Paris, France
- Institut Pasteur, HUB Bioinformatique et Biostatistique, C3BI, USR 3756 IP CNRS, F-75015 Paris, France
| | - Luciana de Oliveira
- Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Institut Pasteur, F-75015 Paris, France
| | - Rafael W Bastos
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903 Ribeirão Preto, Brazil
| | - Frédérique Moyrand
- Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Institut Pasteur, F-75015 Paris, France
| | - Flavia C G Reis
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (FIOCRUZ), 81310-020 Curitiba, Brazil
- Centro de Desenvolvimento Tecnologico em Saude (CDTS-Fiocruz), 21040-361 Rio de Janeiro, Brazil
| | - Clara Valero
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903 Ribeirão Preto, Brazil
| | - Bianca Gimenez
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (FIOCRUZ), 81310-020 Curitiba, Brazil
| | - Luisa J Josefowicz
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (FIOCRUZ), 81310-020 Curitiba, Brazil
| | - Gustavo H Goldman
- Departamento de Ciências Farmacêuticas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, Universidade de São Paulo, 14040-903 Ribeirão Preto, Brazil
| | - Marcio L Rodrigues
- Instituto Carlos Chagas, Fundação Oswaldo Cruz (FIOCRUZ), 81310-020 Curitiba, Brazil
- Instituto de Microbiologia Paulo de Góes (IMPG), Universidade Federal do Rio de Janeiro, 21941-902 Rio de Janeiro, Brazil
| | - Guilhem Janbon
- Unité Biologie des ARN des Pathogènes Fongiques, Département de Mycologie, Institut Pasteur, F-75015 Paris, France
| |
Collapse
|
58
|
Ballou ER, Cook AG, Wallace EWJ. Repeated Evolution of Inactive Pseudonucleases in a Fungal Branch of the Dis3/RNase II Family of Nucleases. Mol Biol Evol 2021; 38:1837-1846. [PMID: 33313834 PMCID: PMC8097288 DOI: 10.1093/molbev/msaa324] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The RNase II family of 3'-5' exoribonucleases is present in all domains of life, and eukaryotic family members Dis3 and Dis3L2 play essential roles in RNA degradation. Ascomycete yeasts contain both Dis3 and inactive RNase II-like "pseudonucleases." The latter function as RNA-binding proteins that affect cell growth, cytokinesis, and fungal pathogenicity. However, the evolutionary origins of these pseudonucleases are unknown: What sequence of events led to their novel function, and when did these events occur? Here, we show how RNase II pseudonuclease homologs, including Saccharomyces cerevisiae Ssd1, are descended from active Dis3L2 enzymes. During fungal evolution, active site mutations in Dis3L2 homologs have arisen at least four times, in some cases following gene duplication. In contrast, N-terminal cold-shock domains and regulatory features are conserved across diverse dikarya and mucoromycota, suggesting that the nonnuclease function requires these regions. In the basidiomycete pathogenic yeast Cryptococcus neoformans, the single Ssd1/Dis3L2 homolog is required for cytokinesis from polyploid "titan" growth stages. This phenotype of C. neoformans Ssd1/Dis3L2 deletion is consistent with those of inactive fungal pseudonucleases, yet the protein retains an active site sequence signature. We propose that a nuclease-independent function for Dis3L2 arose in an ancestral hyphae-forming fungus. This second function has been conserved across hundreds of millions of years, whereas the RNase activity was lost repeatedly in independent lineages.
Collapse
Affiliation(s)
- Elizabeth R Ballou
- Institute for Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| | - Atlanta G Cook
- Wellcome Centre for Cell Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| | - Edward W J Wallace
- Institute for Cell Biology and SynthSys, School of Biological Sciences, University of Edinburgh, Edinburgh, United Kingdom
| |
Collapse
|
59
|
Pradhan A, Ma Q, de Assis LJ, Leaves I, Larcombe DE, Rodriguez Rondon AV, Nev OA, Brown AJP. Anticipatory Stress Responses and Immune Evasion in Fungal Pathogens. Trends Microbiol 2021; 29:416-427. [PMID: 33059975 DOI: 10.1016/j.tim.2020.09.010] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 09/10/2020] [Accepted: 09/22/2020] [Indexed: 12/17/2022]
Abstract
In certain niches, microbes encounter environmental challenges that are temporally linked. In such cases, microbial fitness is enhanced by the evolution of anticipatory responses where the initial challenge simultaneously activates pre-emptive protection against the second impending challenge. The accumulation of anticipatory responses in domesticated yeasts, which have been termed 'adaptive prediction', has led to the emergence of 'core stress responses' that provide stress cross-protection. Protective anticipatory responses also seem to be common in fungal pathogens of humans. These responses reflect the selective pressures that these fungi have faced relatively recently in their evolutionary history. Consequently, some pathogens have evolved 'core environmental responses' which exploit host signals to trigger immune evasion strategies that protect them against imminent immune attack.
Collapse
Affiliation(s)
- Arnab Pradhan
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Qinxi Ma
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Leandro J de Assis
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Ian Leaves
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Daniel E Larcombe
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Alejandra V Rodriguez Rondon
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Olga A Nev
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK
| | - Alistair J P Brown
- Medical Research Council Centre for Medical Mycology, University of Exeter, Geoffrey Pope Building, Stocker Road, Exeter EX4 4QD, UK.
| |
Collapse
|
60
|
Bain JM, Alonso MF, Childers DS, Walls CA, Mackenzie K, Pradhan A, Lewis LE, Louw J, Avelar GM, Larcombe DE, Netea MG, Gow NAR, Brown GD, Erwig LP, Brown AJP. Immune cells fold and damage fungal hyphae. Proc Natl Acad Sci U S A 2021; 118:e2020484118. [PMID: 33876755 PMCID: PMC8053999 DOI: 10.1073/pnas.2020484118] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
Innate immunity provides essential protection against life-threatening fungal infections. However, the outcomes of individual skirmishes between immune cells and fungal pathogens are not a foregone conclusion because some pathogens have evolved mechanisms to evade phagocytic recognition, engulfment, and killing. For example, Candida albicans can escape phagocytosis by activating cellular morphogenesis to form lengthy hyphae that are challenging to engulf. Through live imaging of C. albicans-macrophage interactions, we discovered that macrophages can counteract this by folding fungal hyphae. The folding of fungal hyphae is promoted by Dectin-1, β2-integrin, VASP, actin-myosin polymerization, and cell motility. Folding facilitates the complete engulfment of long hyphae in some cases and it inhibits hyphal growth, presumably tipping the balance toward successful fungal clearance.
Collapse
Affiliation(s)
- Judith M Bain
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - M Fernanda Alonso
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Delma S Childers
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Catriona A Walls
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Kevin Mackenzie
- Microscopy and Histology Facility, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Arnab Pradhan
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
- Medical Research Council Centre for Medical Mycology, University of Exeter, EX4 4QD Exeter, United Kingdom
| | - Leanne E Lewis
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Johanna Louw
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Gabriela M Avelar
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
| | - Daniel E Larcombe
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
- Medical Research Council Centre for Medical Mycology, University of Exeter, EX4 4QD Exeter, United Kingdom
| | - Mihai G Netea
- Department of Internal Medicine and Radboud Center for Infectious Diseases, Radboud University Medical Center, 6500HB Nijmegen, The Netherlands
- Department for Immunology and Metabolism, Life and Medical Sciences Institute, University of Bonn, 53115 Bonn, Germany
| | - Neil A R Gow
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
- Medical Research Council Centre for Medical Mycology, University of Exeter, EX4 4QD Exeter, United Kingdom
| | - Gordon D Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
- Medical Research Council Centre for Medical Mycology, University of Exeter, EX4 4QD Exeter, United Kingdom
| | - Lars P Erwig
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom
- Johnson-Johnson Innovation, Europe, Middle East and Africa Innovation Centre, London W1G 0BG, United Kingdom
| | - Alistair J P Brown
- Aberdeen Fungal Group, Institute of Medical Sciences, Foresterhill, AB25 2ZD Aberdeen, United Kingdom;
- Medical Research Council Centre for Medical Mycology, University of Exeter, EX4 4QD Exeter, United Kingdom
| |
Collapse
|
61
|
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: 24] [Impact Index Per Article: 8.0] [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.
Collapse
|
62
|
The Transcription Factor Pdr802 Regulates Titan Cell Formation and Pathogenicity of Cryptococcus neoformans. mBio 2021; 12:mBio.03457-20. [PMID: 33688010 PMCID: PMC8092302 DOI: 10.1128/mbio.03457-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The pathogenic yeast Cryptococcus neoformans presents a worldwide threat to human health, especially in the context of immunocompromise, and current antifungal therapy is hindered by cost, limited availability, and inadequate efficacy. After the infectious particle is inhaled, C. neoformans initiates a complex transcriptional program that integrates cellular responses and enables adaptation to the host lung environment. Cryptococcus neoformans is a ubiquitous, opportunistic fungal pathogen that kills almost 200,000 people worldwide each year. It is acquired when mammalian hosts inhale the infectious propagules; these are deposited in the lung and, in the context of immunocompromise, may disseminate to the brain and cause lethal meningoencephalitis. Once inside the host, C. neoformans undergoes a variety of adaptive processes, including secretion of virulence factors, expansion of a polysaccharide capsule that impedes phagocytosis, and the production of giant (Titan) cells. The transcription factor Pdr802 is one regulator of these responses to the host environment. Expression of the corresponding gene is highly induced under host-like conditions in vitro and is critical for C. neoformans dissemination and virulence in a mouse model of infection. Direct targets of Pdr802 include the quorum sensing proteins Pqp1, Opt1, and Liv3; the transcription factors Stb4, Zfc3, and Bzp4, which regulate cryptococcal brain infectivity and capsule thickness; the calcineurin targets Had1 and Crz1, important for cell wall remodeling and C. neoformans virulence; and additional genes related to resistance to host temperature and oxidative stress, and to urease activity. Notably, cryptococci engineered to lack Pdr802 showed a dramatic increase in Titan cells, which are not phagocytosed and have diminished ability to directly cross biological barriers. This explains the limited dissemination of pdr802 mutant cells to the central nervous system and the consequently reduced virulence of this strain. The role of Pdr802 as a negative regulator of Titan cell formation is thus critical for cryptococcal pathogenicity.
Collapse
|
63
|
|
64
|
Gerstein AC, Sharp NP. The population genetics of ploidy change in unicellular fungi. FEMS Microbiol Rev 2021; 45:6121427. [PMID: 33503232 DOI: 10.1093/femsre/fuab006] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 01/14/2021] [Indexed: 12/23/2022] Open
Abstract
Changes in ploidy are a significant type of genetic variation, describing the number of chromosome sets per cell. Ploidy evolves in natural populations, clinical populations, and lab experiments, particularly in fungi. Despite a long history of theoretical work on this topic, predicting how ploidy will evolve has proven difficult, as it is often unclear why one ploidy state outperforms another. Here, we review what is known about contemporary ploidy evolution in diverse fungal species through the lens of population genetics. As with typical genetic variants, ploidy evolution depends on the rate that new ploidy states arise by mutation, natural selection on alternative ploidy states, and random genetic drift. However, ploidy variation also has unique impacts on evolution, with the potential to alter chromosomal stability, the rate and patterns of point mutation, and the nature of selection on all loci in the genome. We discuss how ploidy evolution depends on these general and unique factors and highlight areas where additional experimental evidence is required to comprehensively explain the ploidy transitions observed in the field and the lab.
Collapse
Affiliation(s)
- Aleeza C Gerstein
- Dept. of Microbiology, Dept. of Statistics, University of Manitoba Canada
| | | |
Collapse
|
65
|
da Silva-Junior EB, Firmino-Cruz L, Guimarães-de-Oliveira JC, De-Medeiros JVR, de Oliveira Nascimento D, Freire-de-Lima M, de Brito-Gitirana L, Morrot A, Previato JO, Mendonça-Previato L, Decote-Ricardo D, de Matos Guedes HL, Freire-de-Lima CG. The role of Toll-like receptor 9 in a murine model of Cryptococcus gattii infection. Sci Rep 2021; 11:1407. [PMID: 33446850 PMCID: PMC7809259 DOI: 10.1038/s41598-021-80959-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Accepted: 12/31/2020] [Indexed: 02/07/2023] Open
Abstract
Toll-like receptor 9 (TLR9) is crucial to the host immune response against fungi, such as Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, but its importance in Cryptococcus gattii infection is unknown. Our study aimed to understand the role of TLR9 during the course of experimental C. gattii infection in vivo, considering that the cryptococcal DNA interaction with the receptor could contribute to host immunity even in an extremely susceptible model. We inoculated C57BL/6 (WT) and TLR9 knock-out (TLR9−/−) mice intratracheally with 104C. gattii yeast cells. TLR9−/− mice had a higher mortality rate compared to WT mice and more yeast cells that had abnormal size, known as titan cells, in the lungs. TLR9−/− mice also had a greater number of CFUs in the spleen and brain than WT mice, in addition to having lower levels of IFN-γ and IL-17 in the lung. With these markers of aggressive cryptococcosis, we can state that TLR9−/− mice are more susceptible to C. gattii, probably due to a mechanism associated with the decrease of a Th1 and Th17-type immune response that promotes the formation of titan cells in the lungs. Therefore, our results indicate the participation of TLR9 in murine resistance to C. gattii infection.
Collapse
Affiliation(s)
- Elias Barbosa da Silva-Junior
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Luan Firmino-Cruz
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil.,Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, 21045-900, Brazil
| | | | - Juliana Valente Rodrigues De-Medeiros
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil.,Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, 21045-900, Brazil
| | | | - Matheus Freire-de-Lima
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Lycia de Brito-Gitirana
- Instituto de Ciências Biomédicas, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Alexandre Morrot
- Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, 21045-900, Brazil.,Faculdade de Medicina, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Jose Osvaldo Previato
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Lucia Mendonça-Previato
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil
| | - Debora Decote-Ricardo
- Instituto de Veterinária, Universidade Federal Rural do Rio de Janeiro, Seropédica, 23890-000, Brazil.
| | - Herbert Leonel de Matos Guedes
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil. .,Instituto Oswaldo Cruz, FIOCRUZ, Rio de Janeiro, 21045-900, Brazil.
| | - Celio Geraldo Freire-de-Lima
- Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro, 21941-900, Brazil.
| |
Collapse
|
66
|
Treatment strategies for cryptococcal infection: challenges, advances and future outlook. Nat Rev Microbiol 2021; 19:454-466. [PMID: 33558691 PMCID: PMC7868659 DOI: 10.1038/s41579-021-00511-0] [Citation(s) in RCA: 135] [Impact Index Per Article: 45.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/07/2021] [Indexed: 01/31/2023]
Abstract
Cryptococcus spp., in particular Cryptococcus neoformans and Cryptococcus gattii, have an enormous impact on human health worldwide. The global burden of cryptococcal meningitis is almost a quarter of a million cases and 181,000 deaths annually, with mortality rates of 100% if infections remain untreated. Despite these alarming statistics, treatment options for cryptococcosis remain limited, with only three major classes of drugs approved for clinical use. Exacerbating the public health burden is the fact that the only new class of antifungal drugs developed in decades, the echinocandins, displays negligible antifungal activity against Cryptococcus spp., and the efficacy of the remaining therapeutics is hampered by host toxicity and pathogen resistance. Here, we describe the current arsenal of antifungal agents and the treatment strategies employed to manage cryptococcal disease. We further elaborate on the recent advances in our understanding of the intrinsic and adaptive resistance mechanisms that are utilized by Cryptococcus spp. to evade therapeutic treatments. Finally, we review potential therapeutic strategies, including combination therapy, the targeting of virulence traits, impairing stress response pathways and modulating host immunity, to effectively treat infections caused by Cryptococcus spp. Overall, understanding of the mechanisms that regulate anti-cryptococcal drug resistance, coupled with advances in genomics technologies and high-throughput screening methodologies, will catalyse innovation and accelerate antifungal drug discovery.
Collapse
|
67
|
Zhao J, Yang Y, Fan Y, Yi J, Zhang C, Gu Z, Pan W, Gu J, Liao W, Fang W. Ribosomal Protein L40e Fused With a Ubiquitin Moiety Is Essential for the Vegetative Growth, Morphological Homeostasis, Cell Cycle Progression, and Pathogenicity of Cryptococcus neoformans. Front Microbiol 2020; 11:570269. [PMID: 33224112 PMCID: PMC7674629 DOI: 10.3389/fmicb.2020.570269] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2020] [Accepted: 08/20/2020] [Indexed: 11/13/2022] Open
Abstract
Ubiquitin is a highly conserved protein required for various fundamental cellular processes in eukaryotes. Herein, we first report the contribution of the ubiquitin fusion protein Ubi1 (a ubiquitin monomer fused with the ribosome protein L40e, Rpl40e) in the growth and pathogenicity of Cryptococcus neoformans. UBI1 deletion resulted in severe growth restriction of C. neoformans, whose growth rate was positively correlated with UBI1 expression level. The growth defect of the ubi1Δ strain could be closely associated with its morphological abnormalities, such as its reduced ribosome particles. In addition, the ubi1Δ mutant also displayed increased cell ploidy, cell cycle arrest, and decreased intracellular survival inside macrophages. All these phenotypes were reversed by the reconstitution of the full-length UBI1 gene or RPL40a domain. Mouse survival and fungal burden assays further revealed a severely attenuated pathogenicity for the ubi1Δ mutant, which is probably associated with its reduced stress tolerance and the induction of T-helper 1-type immune response. Taken together, Ubi1 is required for maintaining the vegetative growth, morphological homeostasis, cell cycle progression, and pathogenicity in vivo of C. neoformans. The pleiotropic roles of Ubi1 are dependent on the presence of Rpl40e and associated with its regulation of cryptococcal ribosome biogenesis.
Collapse
Affiliation(s)
- Jingyu Zhao
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China.,Department of Dermatology, Shanghai Eastern Hepatobiliary Surgery Hospital, Shanghai, China
| | - Yali Yang
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China.,Department of Dermatology, Shanghai Ninth People's Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China
| | - Yibin Fan
- Department of Dermatology, Zhejiang Provincial People's Hospital, People's Hospital of Hangzhou Medical College, Hangzhou, China
| | - Jiu Yi
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Chao Zhang
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Zhongkai Gu
- The Institute of Biomedical Sciences, Fudan University, Shanghai, China
| | - Weihua Pan
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Julin Gu
- Department of Dermatology, Shanghai Eastern Hepatobiliary Surgery Hospital, Shanghai, China
| | - Wanqing Liao
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| | - Wei Fang
- Shanghai Key Laboratory of Molecular Medical Mycology, Department of Dermatology, Changzheng Hospital, Second Military Medical University, Shanghai, China
| |
Collapse
|
68
|
Gaylord EA, Choy HL, Doering TL. Dangerous Liaisons: Interactions of Cryptococcus neoformans with Host Phagocytes. Pathogens 2020; 9:E891. [PMID: 33121050 PMCID: PMC7692806 DOI: 10.3390/pathogens9110891] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 10/22/2020] [Accepted: 10/25/2020] [Indexed: 02/07/2023] Open
Abstract
Cryptococcus neoformans is an opportunistic fungal pathogen and a leading cause of death in immunocompromised individuals. The interactions of this yeast with host phagocytes are critical to disease outcome, and C. neoformans is equipped with an array of factors to modulate these processes. Cryptococcal infection begins with the deposition of infectious particles into the lungs, where the fungal cells deploy various antiphagocytic factors to resist internalization by host cells. If the cryptococci are still engulfed, they can survive and proliferate within host cells by modulating the phagolysosome environment in which they reside. Lastly, cryptococcal cells may escape from phagocytes by host cell lysis, nonlytic exocytosis, or lateral cell-to-cell transfer. The interactions between C. neoformans and host phagocytes also influence the dissemination of this pathogen to the brain, where it may cross the blood-brain barrier and cause an often-fatal meningoencephalitis. In this review, we highlight key cryptococcal factors involved in various stages of cryptococcal-host interaction and pathogenesis.
Collapse
Affiliation(s)
| | | | - Tamara L. Doering
- Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO 63110, USA; (E.A.G.); (H.L.C.)
| |
Collapse
|
69
|
Abstract
Diversity within the fungal kingdom is evident from the wide range of morphologies fungi display as well as the various ecological roles and industrial purposes they serve. Technological advances, particularly in long-read sequencing, coupled with the increasing efficiency and decreasing costs across sequencing platforms have enabled robust characterization of fungal genomes. These sequencing efforts continue to reveal the rampant diversity in fungi at the genome level. Here, we discuss studies that have furthered our understanding of fungal genetic diversity and genomic evolution. These studies revealed the presence of both small-scale and large-scale genomic changes. In fungi, research has recently focused on many small-scale changes, such as how hypermutation and allelic transmission impact genome evolution as well as how and why a few specific genomic regions are more susceptible to rapid evolution than others. High-throughput sequencing of a diverse set of fungal genomes has also illuminated the frequency, mechanisms, and impacts of large-scale changes, which include chromosome structural variation and changes in chromosome number, such as aneuploidy, polyploidy, and the presence of supernumerary chromosomes. The studies discussed herein have provided great insight into how the architecture of the fungal genome varies within species and across the kingdom and how modern fungi may have evolved from the last common fungal ancestor and might also pave the way for understanding how genomic diversity has evolved in all domains of life.
Collapse
Affiliation(s)
- Shelby J. Priest
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
| | - Vikas Yadav
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Centre, Durham, NC, USA
| |
Collapse
|
70
|
Evaluation of antifungal activity of cinnamaldehyde against Cryptococcus neoformans var. grubii. Folia Microbiol (Praha) 2020; 65:973-987. [PMID: 32617865 DOI: 10.1007/s12223-020-00806-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Accepted: 06/18/2020] [Indexed: 12/21/2022]
Abstract
Cryptococcosis is a potentially fatal fungal disease which has aggrandized with the emergence of AIDS and antifungal resistance. The currently used antifungals lack the broad-spectrum activity and result in several toxicities during long treatment regimens. Thus, the present study aims to evaluate the antifungal activity of cinnamaldehyde against Cryptococcus neoformans var. grubii, the etiological agent of the disease. Quantitative and qualitative in vitro fungal susceptibilities were carried out by minimum inhibitory concentration assay, flow cytometric analysis, and confocal microscopy. Micromorphological alterations were studied through scanning electron and light microscopies. "In vivo" antifungal efficacy of cinnamaldehyde was assessed. Cinnamaldehyde showed antifungal activity against C. neoformans in a dose-dependent manner. A concentration of 1.37 mg/mL of cinnamaldehyde was found to be inhibitory and fungicidal while the low concentration (0.68 mg/mL) was found to induce micromorphological changes and formation of giant/titan-like cells in this pathogen. The reparative activity of cinnamaldehyde and its ability to prolong the life even after the advent of cryptococcal meningitis in mice was also noticed. This study suggests potent anti-cryptococcal activity of cinnamaldehyde. Though, it has a couple of limitations like allergy and low bioavailability. However, these problems can be circumvented by developing suitable analogs of the compound. It, therefore, could be used as a therapeutic option against cryptococcosis and cryptococcal meningitis. Moreover, the evaluation of its pharmacokinetic and pharmacodynamic properties is desirable.
Collapse
|
71
|
Human IgM Inhibits the Formation of Titan-Like Cells in Cryptococcus neoformans. Infect Immun 2020; 88:IAI.00046-20. [PMID: 31988178 DOI: 10.1128/iai.00046-20] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2020] [Accepted: 01/22/2020] [Indexed: 02/07/2023] Open
Abstract
Human studies have shown associations between cryptococcal meningitis and reduced IgM memory B cell levels, and studies in IgM- and/or B cell-deficient mice have demonstrated increased Cryptococcus neoformans dissemination from lungs to brain. Since immunoglobulins are part of the immune milieu that C. neoformans confronts in a human host, and its ability to form titan cells is an important virulence mechanism, we determined the effect of human immunoglobulins on C. neoformans titan cell formation in vitro (i) Fluorescence microscopy showed normal human IgG and IgM bind C. neoformans (ii) C. neoformans grown in titan cell-inducing medium with IgM, not IgG, inhibited titan-like cell formation. (iii) Absorption of IgM with laminarin or curdlan (branched and linear 1-3-beta-d-glucans, respectively) decreased this effect. (iv) Transmission electron microscopy revealed that cells grown with IgM had small capsules and unique features not seen with cells grown with IgG. (v) Comparative transcriptional analysis of cell wall, capsule, and stress response genes showed that C. neoformans grown with IgM, not IgG or phosphate-buffered saline (PBS), had decreased expression of chitin synthetase, CHS1, CHS2, and CHS8, and genes encoding cell wall carbohydrate synthetases α-1-3-glucan (AGS1) and β-1,3-glucan (FKS1). IgM also decreased expression of RIM101 and HOG1, genes encoding central regulators of C. neoformans stress response pathways and cell morphogenesis. Our data show human IgM affects C. neoformans morphology in vitro and suggest that the hypothesis that human immunoglobulins may affect C. neoformans virulence in vivo warrants further investigation.
Collapse
|
72
|
Pseudohyphal Growth of the Emerging Pathogen Candida auris Is Triggered by Genotoxic Stress through the S Phase Checkpoint. mSphere 2020; 5:5/2/e00151-20. [PMID: 32161147 PMCID: PMC7067593 DOI: 10.1128/msphere.00151-20] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Candida auris is a newly emerged fungal pathogen of humans. This species was first reported in 2009 when it was identified in an ear infection of a patient in Japan. However, despite intense interest in this organism as an often multidrug-resistant fungus, there is little knowledge about its cellular biology. During infection of human patients, fungi are able to change cell shape from ellipsoidal yeast cells to elongated filaments to adapt to various conditions within the host organism. There are different types of filaments, which are triggered by reactions to different cues. Candida auris fails to form filaments when exposed to triggers that stimulate yeast filament morphogenesis in other fungi. Here, we show that it does form filaments when its DNA is damaged. These conditions might arise when Candida auris cells interact with host immune cells or during growth in certain host tissues (kidney or bladder) or during treatment with antifungal drugs. The morphogenetic switching between yeast cells and filaments (true hyphae and pseudohyphae) is a key cellular feature required for full virulence in many polymorphic fungal pathogens, such as Candida albicans. In the recently emerged yeast pathogen Candida auris, occasional elongation of cells has been reported. However, environmental conditions and genetic triggers for filament formation have remained elusive. Here, we report that induction of DNA damage and perturbation of replication forks by treatment with genotoxins, such as hydroxyurea, methyl methanesulfonate, and the clinically relevant fungistatic 5-fluorocytosine, cause filamentation in C. auris. The filaments formed were characteristic of pseudohyphae and not parallel-sided true hyphae. Pseudohyphal growth is apparently signaled through the S phase checkpoint and, interestingly, is Tup1 independent in C. auris. Intriguingly, the morphogenetic switching capability is strain specific in C. auris, highlighting the heterogenous nature of the species as a whole. IMPORTANCECandida auris is a newly emerged fungal pathogen of humans. This species was first reported in 2009 when it was identified in an ear infection of a patient in Japan. However, despite intense interest in this organism as an often multidrug-resistant fungus, there is little knowledge about its cellular biology. During infection of human patients, fungi are able to change cell shape from ellipsoidal yeast cells to elongated filaments to adapt to various conditions within the host organism. There are different types of filaments, which are triggered by reactions to different cues. Candida auris fails to form filaments when exposed to triggers that stimulate yeast filament morphogenesis in other fungi. Here, we show that it does form filaments when its DNA is damaged. These conditions might arise when Candida auris cells interact with host immune cells or during growth in certain host tissues (kidney or bladder) or during treatment with antifungal drugs.
Collapse
|
73
|
Abstract
Among fungal pathogens, Cryptococcus neoformans has gained great importance among the scientific community of several reasons. This fungus is the causative agent of cryptococcosis, a disease mainly associated to HIV immunosuppression and characterized by the appearance of meningoencephalitis. Cryptococcal meningitis is responsible for hundreds of thousands of deaths every year. Research of the pathogenesis and virulence mechanisms of this pathogen has focused on three main different areas: Adaptation to the host environment (nutrients, pH, and free radicals), mechanism of immune evasion (which include phenotypic variations and the ability to behave as a facultative intracellular pathogen), and production of virulence factors. Cryptococcus neoformans has two phenotypic characteristics, the capsule and synthesis of melanin that have a profound effect in the virulence of the yeast because they both have protective effects and induce host damage as virulence factors. Finally, the mechanisms that result in dissemination and brain invasion are also of key importance to understand cryptococcal disease. In this review, I will provide a brief overview of the main mechanisms that makes C. neoformans a pathogen in susceptible patients. Abbreviations: RNS: reactive nitrogen species; BBB: brain blood barrier; GXM: glucuronoxylomannan; GXMGal: glucuronoxylomannogalactan
Collapse
Affiliation(s)
- Oscar Zaragoza
- a Mycology Reference Laboratory National Centre for Microbiology , Instituto de Salud Carlos III Carretera Majadahonda-Pozuelo , Madrid , Spain
| |
Collapse
|
74
|
Zhao Y, Wang Y, Upadhyay S, Xue C, Lin X. Activation of Meiotic Genes Mediates Ploidy Reduction during Cryptococcal Infection. Curr Biol 2020; 30:1387-1396.e5. [PMID: 32109388 DOI: 10.1016/j.cub.2020.01.081] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 12/04/2019] [Accepted: 01/28/2020] [Indexed: 12/23/2022]
Abstract
Cryptococcus neoformans is a global human fungal pathogen that causes fatal meningoencephalitis in mostly immunocompromised individuals. During pulmonary infection, cryptococcal cells form large polyploid cells that exhibit increased resistance to host immune attack and are proposed to contribute to the latency of cryptococcal infection. These polyploid titan cells can generate haploid and aneuploid progeny that may result in systemic infection. What triggers cryptococcal polyploidization and how ploidy reduction is achieved remain open questions. Here, we discovered that Cryptococcus cells polyploidize in response to genotoxic stresses that cause DNA double-strand breaks. Intriguingly, meiosis-specific genes are activated in C. neoformans and contribute to ploidy reduction, both in vitro and during infection in mice. Cryptococcal cells that activated their meiotic genes in mice were resistant to specific genotoxic stress compared to sister cells recovered from the same host tissue but without activation of meiotic genes. Our findings support the idea that meiotic genes, in addition to their conventional roles in classic sexual reproduction, contribute to adaptation of eukaryotic cells that undergo dramatic genome changes in response to genotoxic stress. The discovery has additional implications for evolution of sexual reproduction and the paradox of the presence of meiotic machinery in asexual species. Finally, our findings in this eukaryotic microbe mirror the revolutionary discoveries of the polyploidization and meiosis-like ploidy reduction process in cancer cells, suggesting that the reversible ploidy change itself could provide a general mechanism for rejuvenation to promote individual survival in response to stress.
Collapse
Affiliation(s)
- Youbao Zhao
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA
| | - Yina Wang
- Public Health Research Institute Center, New Jersey Medical School - Rutgers, The State University of New Jersey, Newark, NJ 07103, USA
| | - Srijana Upadhyay
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA
| | - Chaoyang Xue
- Public Health Research Institute Center, New Jersey Medical School - Rutgers, The State University of New Jersey, Newark, NJ 07103, USA.
| | - Xiaorong Lin
- Department of Microbiology, University of Georgia, Athens, GA 30602, USA; Department of Plant Biology, University of Georgia, Athens, GA 30602, USA.
| |
Collapse
|
75
|
Scanning electron microscopy and machine learning reveal heterogeneity in capsular morphotypes of the human pathogen Cryptococcus spp. Sci Rep 2020; 10:2362. [PMID: 32047210 PMCID: PMC7012869 DOI: 10.1038/s41598-020-59276-w] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 01/16/2020] [Indexed: 01/09/2023] Open
Abstract
Phenotypic heterogeneity is an important trait for the development and survival of many microorganisms including the yeast Cryptococcus spp., a deadly pathogen spread worldwide. Here, we have applied scanning electron microscopy (SEM) to define four Cryptococcus spp. capsule morphotypes, namely Regular, Spiky, Bald, and Phantom. These morphotypes were persistently observed in varying proportions among yeast isolates. To assess the distribution of such morphotypes we implemented an automated pipeline capable of (1) identifying potentially cell-associated objects in the SEM-derived images; (2) computing object-level features; and (3) classifying these objects into their corresponding classes. The machine learning approach used a Random Forest (RF) classifier whose overall accuracy reached 85% on the test dataset, with per-class specificity above 90%, and sensitivity between 66 and 94%. Additionally, the RF model indicates that structural and texture features, e.g., object area, eccentricity, and contrast, are most relevant for classification. The RF results agree with the observed variation in these features, consistently also with visual inspection of SEM images. Finally, our work introduces morphological variants of Cryptococcus spp. capsule. These can be promptly identified and characterized using computational models so that future work may unveil morphological associations with yeast virulence.
Collapse
|
76
|
Maliehe M, Ntoi MA, Lahiri S, Folorunso OS, Ogundeji AO, Pohl CH, Sebolai OM. Environmental Factors That Contribute to the Maintenance of Cryptococcus neoformans Pathogenesis. Microorganisms 2020; 8:microorganisms8020180. [PMID: 32012843 PMCID: PMC7074686 DOI: 10.3390/microorganisms8020180] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2019] [Revised: 12/04/2019] [Accepted: 12/11/2019] [Indexed: 02/07/2023] Open
Abstract
The ability of microorganisms to colonise and display an intracellular lifestyle within a host body increases their fitness to survive and avoid extinction. This host–pathogen association drives microbial evolution, as such organisms are under selective pressure and can become more pathogenic. Some of these microorganisms can quickly spread through the environment via transmission. The non-transmittable fungal pathogens, such as Cryptococcus, probably return into the environment upon decomposition of the infected host. This review analyses whether re-entry of the pathogen into the environment causes restoration of its non-pathogenic state or whether environmental factors and parameters assist them in maintaining pathogenesis. Cryptococcus (C.) neoformans is therefore used as a model organism to evaluate the impact of environmental stress factors that aid the survival and pathogenesis of C. neoformans intracellularly and extracellularly.
Collapse
|
77
|
Chung KY, Brown JCS. Biology and function of exo-polysaccharides from human fungal pathogens. CURRENT CLINICAL MICROBIOLOGY REPORTS 2020; 7:1-11. [PMID: 33042730 DOI: 10.1007/s40588-020-00137-5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Purpose of review Environmental fungi such as Cryptococcus neoformans and Aspergillus fumigatus must survive many different and changing environments as they transition from their environmental niches to human lungs and other organs. Fungi alter their cell surfaces and secreted macromolecules to respond to and manipulate their surroundings. Recent findings This review focuses on exo-polysaccharides, chains of sugars that transported out of the cell and spread to the local environment. Major exo-polysaccharides for C. neoformans and A. fumigatus are glucuronylxylomannan (GXM) and galactosaminogalactan (GAG), respectively, which accumulate at high concentrations in growth medium and infected patients. Summary Here we discuss GXM and GAG synthesis and export, their immunomodulatory properties, and their roles in biofilm formation. We also propose areas of future research to address outstanding questions in the field that could facilitate development of new disease treatments.
Collapse
Affiliation(s)
- Krystal Y Chung
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| | - Jessica C S Brown
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Salt Lake City, UT 84112, USA
| |
Collapse
|
78
|
Ballou ER. mSphere of Influence: Positive Research Culture Enables Excellence and Innovation. mSphere 2020; 5:5/1/e00948-19. [PMID: 31941817 PMCID: PMC6968658 DOI: 10.1128/msphere.00948-19] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Elizabeth Ballou works in the field of medical mycology. In this mSphere of Influence article, she reflects on how two papers by Okagaki et al. (PLoS Pathog 6:e1000953, 2010, https://doi.org/10.1371/journal.ppat.1000953) and Zaragoza et al. (PLoS Pathog 6:e1000945, 2010, https://doi.org/10.1371/journal.ppat.1000945) made an impact on her career by demonstrating an alternative to destructive publication practices.
Collapse
Affiliation(s)
- Elizabeth R Ballou
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, United Kingdom
| |
Collapse
|
79
|
Garcia-Rubio R, de Oliveira HC, Rivera J, Trevijano-Contador N. The Fungal Cell Wall: Candida, Cryptococcus, and Aspergillus Species. Front Microbiol 2020; 10:2993. [PMID: 31993032 PMCID: PMC6962315 DOI: 10.3389/fmicb.2019.02993] [Citation(s) in RCA: 351] [Impact Index Per Article: 87.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 12/10/2019] [Indexed: 01/23/2023] Open
Abstract
The fungal cell wall is located outside the plasma membrane and is the cell compartment that mediates all the relationships of the cell with the environment. It protects the contents of the cell, gives rigidity and defines the cellular structure. The cell wall is a skeleton with high plasticity that protects the cell from different stresses, among which osmotic changes stand out. The cell wall allows interaction with the external environment since some of its proteins are adhesins and receptors. Since, some components have a high immunogenic capacity, certain wall components can drive the host's immune response to promote fungus growth and dissemination. The cell wall is a characteristic structure of fungi and is composed mainly of glucans, chitin and glycoproteins. As the components of the fungal cell wall are not present in humans, this structure is an excellent target for antifungal therapy. In this article, we review recent data on the composition and synthesis, influence of the components of the cell wall in fungi-host interaction and the role as a target for the next generation of antifungal drugs in yeasts (Candida and Cryptococcus) and filamentous fungi (Aspergillus).
Collapse
Affiliation(s)
- Rocio Garcia-Rubio
- Center for Discovery and Innovation, Hackensack Meridian Health, Nutley, NJ, United States
| | | | - Johanna Rivera
- Division of Infectious Diseases, Department of Medicine, Albert Einstein College of Medicine, New York, NY, United States
| | - Nuria Trevijano-Contador
- Division of Infectious Diseases, Department of Medicine, Albert Einstein College of Medicine, New York, NY, United States
| |
Collapse
|
80
|
Campuzano A, Castro-Lopez N, Martinez AJ, Olszewski MA, Ganguly A, Leopold Wager C, Hung CY, Wormley FL. CARD9 Is Required for Classical Macrophage Activation and the Induction of Protective Immunity against Pulmonary Cryptococcosis. mBio 2020; 11:e03005-19. [PMID: 31911495 PMCID: PMC6946806 DOI: 10.1128/mbio.03005-19] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2019] [Accepted: 11/20/2019] [Indexed: 01/08/2023] Open
Abstract
Caspase recruitment domain-containing protein 9 (CARD9) is a critical adaptor molecule triggered by the interaction of C-type lectin receptors (CLRs) with carbohydrate motifs found in fungi. Consequently, clinical and animal studies indicate that CARD9 is an important regulator of protective immunity against fungal pathogens. Previous studies suggest that CARD9 is important for the induction of protection against Cryptococcus neoformans, an opportunistic fungal pathogen that causes life-threatening infections of the central nervous system in immunocompromised patients. However, the effect of CARD9 deficiency on the induction of protective immune responses against C. neoformans is unknown. Immunization with a C. neoformans mutant that overexpresses the transcription factor zinc finger 2, denoted LW10, results in protection against an otherwise lethal challenge with wild-type (WT) C. neoformans Our results showed that CARD9 is essential for the induction of vaccine-mediated immunity against C. neoformans infection. We observed significant decreases in interleukin-17 (IL-17) production and significant increases in Th2-type cytokine (IL-4, IL-5, and IL-13) production in CARD9-deficient mice after inoculation with strain LW10. While leukocyte infiltration to the lungs of CARD9-deficient mice was similar in LW10 and WT C. neoformans-infected mice, macrophages derived from CARD9-deficient mice inherently skewed toward an M2 activation phenotype, were unable to contain the growth of LW10, and failed to produce nitric oxide in response to infection with LW10 or stimulation with lipopolysaccharide. These results suggest that CARD9-mediated signaling is required for M1 macrophage activation and fungicidal activity necessary for the induction of vaccine-mediated immunity against C. neoformansIMPORTANCECryptococcus neoformans is a fungal pathogen that is found throughout the environment and can cause life-threatening infections of the lung and central nervous system in severely immunocompromised individuals. Caspase recruitment domain-containing protein 9 (CARD9) is a critical molecule that is activated after interactions of C-type lectin receptors (CLRs) found on the surfaces of specific immune cells, with carbohydrate structures associated with fungi. Patients with defects in CARD9 are significantly more susceptible to a multitude of fungal infections. C. neoformans contains several carbohydrate structures that interact with CLRs on immune cells and activate CARD9. Consequently, these studies evaluated the necessity of CARD9 for the induction of protective immunity against C. neoformans infection. These results are important, as they advance our understanding of cryptococcal pathogenesis and host factors necessary for the induction of protective immunity against C. neoformans.
Collapse
Affiliation(s)
- Althea Campuzano
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Natalia Castro-Lopez
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Amanda J Martinez
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Michal A Olszewski
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Michigan Medicine University, Ann Arbor, Michigan, USA
- VA Ann Arbor Healthcare System, Research Service, Ann Arbor, Michigan, USA
| | - Anutosh Ganguly
- VA Ann Arbor Healthcare System, Research Service, Ann Arbor, Michigan, USA
- Division of Hepatobiliary Surgery, Department of Surgery, Michigan Medicine, University of Michigan, Ann Arbor, Michigan, USA
| | - Chrissy Leopold Wager
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Chiung-Yu Hung
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| | - Floyd L Wormley
- Department of Biology, South Texas Center for Emerging Infectious Diseases, The University of Texas at San Antonio, San Antonio, Texas, USA
| |
Collapse
|
81
|
T Cell Antifungal Immunity and the Role of C-Type Lectin Receptors. Trends Immunol 2019; 41:61-76. [PMID: 31813764 PMCID: PMC7427322 DOI: 10.1016/j.it.2019.11.007] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2019] [Revised: 10/28/2019] [Accepted: 11/11/2019] [Indexed: 02/06/2023]
Abstract
Fungi can cause disease in humans, from mucocutaneous to life-threatening systemic infections. Initiation of antifungal immunity involves fungal recognition by pattern recognition receptors such as C-type lectin receptors (CLRs). These germline-encoded receptors trigger a multitude of innate responses including phagocytosis, fungal killing, and antigen presentation which can also shape the development of adaptive immunity. Recently, studies have shed light on how CLRs directly or indirectly modulate lymphocyte function. Moreover, CLR-mediated recognition of commensal fungi maintains homeostasis and prevents invasion from opportunistic commensals. We present an overview of current knowledge of antifungal T cell immune responses, with emphasis on the role of C-type lectins, and discuss how these receptors modulate these responses at different levels. CLRs are essential pattern recognition receptors involved in fungal recognition and initiation of protective antifungal immunity. CLRs promote the differentiation of mammalian T helper cell subsets essential for the control of systemic (Th1) and mucosal (Th17) fungal infections. CLRs are involved in antigen presentation, the expression of co-stimulatory molecules, and cytokine secretion; therefore, they can regulate lymphocyte function and adaptive immune responses at different levels. Fungal morphological changes, such as the transition from yeast to hyphae in Candida albicans during tissue invasion, affects recognition by CLRs and impacts on adaptive immune responses. CLRs recognize the fungal component of the microbiome that can influence T cell responses during infection at intestinal and peripheral sites.
Collapse
|
82
|
Sun S, Coelho MA, David-Palma M, Priest SJ, Heitman J. The Evolution of Sexual Reproduction and the Mating-Type Locus: Links to Pathogenesis of Cryptococcus Human Pathogenic Fungi. Annu Rev Genet 2019; 53:417-444. [PMID: 31537103 PMCID: PMC7025156 DOI: 10.1146/annurev-genet-120116-024755] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Cryptococcus species utilize a variety of sexual reproduction mechanisms, which generate genetic diversity, purge deleterious mutations, and contribute to their ability to occupy myriad environmental niches and exhibit a range of pathogenic potential. The bisexual and unisexual cycles of pathogenic Cryptococcus species are stimulated by properties associated with their environmental niches and proceed through well-characterized signaling pathways and corresponding morphological changes. Genes governing mating are encoded by the mating-type (MAT) loci and influence pathogenesis, population dynamics, and lineage divergence in Cryptococcus. MAT has undergone significant evolutionary changes within the Cryptococcus genus, including transition from the ancestral tetrapolar state in nonpathogenic species to a bipolar mating system in pathogenic species, as well as several internal reconfigurations. Owing to the variety of established sexual reproduction mechanisms and the robust characterization of the evolution of mating and MAT in this genus, Cryptococcus species provide key insights into the evolution of sexual reproduction.
Collapse
Affiliation(s)
- Sheng Sun
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Marco A Coelho
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Márcia David-Palma
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Shelby J Priest
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| | - Joseph Heitman
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina 27710, USA;
| |
Collapse
|
83
|
Zafar H, Altamirano S, Ballou ER, Nielsen K. A titanic drug resistance threat in Cryptococcus neoformans. Curr Opin Microbiol 2019; 52:158-164. [PMID: 31765991 DOI: 10.1016/j.mib.2019.11.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 10/01/2019] [Accepted: 11/01/2019] [Indexed: 10/25/2022]
Abstract
Increasing resistance to frontline antifungals is a growing threat to global health. In the face of high rates of relapse for patients with cryptococcal meningitis and frequent drug resistance in clinical isolates, recent insights into Cryptococcus neoformans morphogenesis and genome plasticity take on new and urgent meaning. Here we review the state of the understanding of mechanisms of drug resistance in the context of host-relevant changes in Cryptococcus morphology and cell ploidy.
Collapse
Affiliation(s)
- Hanna Zafar
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - Sophie Altamirano
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455 USA
| | - Elizabeth R Ballou
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK.
| | - Kirsten Nielsen
- Department of Microbiology and Immunology, University of Minnesota, Minneapolis, MN, 55455 USA.
| |
Collapse
|
84
|
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.
Collapse
|
85
|
Buscaino A. Chromatin-Mediated Regulation of Genome Plasticity in Human Fungal Pathogens. Genes (Basel) 2019; 10:E855. [PMID: 31661931 PMCID: PMC6896017 DOI: 10.3390/genes10110855] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/18/2019] [Accepted: 10/25/2019] [Indexed: 12/20/2022] Open
Abstract
Human fungal pathogens, such as Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans, are a public health problem, causing millions of infections and killing almost half a million people annually. The ability of these pathogens to colonise almost every organ in the human body and cause life-threating infections relies on their capacity to adapt and thrive in diverse hostile host-niche environments. Stress-induced genome instability is a key adaptive strategy used by human fungal pathogens as it increases genetic diversity, thereby allowing selection of genotype(s) better adapted to a new environment. Heterochromatin represses gene expression and deleterious recombination and could play a key role in modulating genome stability in response to environmental changes. However, very little is known about heterochromatin structure and function in human fungal pathogens. In this review, I use our knowledge of heterochromatin structure and function in fungal model systems as a road map to review the role of heterochromatin in regulating genome plasticity in the most common human fungal pathogens: Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans.
Collapse
Affiliation(s)
- Alessia Buscaino
- University of Kent, School of Biosciences, Kent Fungal Group, Canterbury Kent CT2 7NJ, UK.
| |
Collapse
|
86
|
Coelho C, Camacho E, Salas A, Alanio A, Casadevall A. Intranasal Inoculation of Cryptococcus neoformans in Mice Produces Nasal Infection with Rapid Brain Dissemination. mSphere 2019; 4:e00483-19. [PMID: 31391283 PMCID: PMC6686232 DOI: 10.1128/msphere.00483-19] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2019] [Accepted: 07/22/2019] [Indexed: 12/12/2022] Open
Abstract
Cryptococcus neoformans is an important fungal pathogen, causing life-threatening pneumonia and meningoencephalitis. Brain dissemination of C. neoformans is thought to be a consequence of an active infection in the lung which then extravasates to other sites. Brain invasion results from dissemination via either transport by free yeast cells in the bloodstream or Trojan horse transport within mononuclear phagocytes. We assessed brain dissemination in three mouse models of infection: intravenous, intratracheal, and intranasal models. All three modes of infection resulted in dissemination of C. neoformans to the brain in less than 3 h. Further, C. neoformans was detected in the entirety of the upper respiratory tract and the ear canals of mice. In recent years, intranasal infection has become a popular mechanism to induce pulmonary infection because it avoids surgery, but our findings show that instillation of C. neoformans produces cryptococcal nasal infection. These findings imply that immunological studies using intranasal infection should assume that the initial sites of infection of infection are brain, lung, and upper respiratory tract, including the nasal airways.IMPORTANCECryptococcus neoformans causes an estimated 181, 000 deaths each year, mostly associated with untreated HIV/AIDS. C. neoformans has a ubiquitous worldwide distribution. Humans become infected from exposure to environmental sources, after which the fungus lays dormant within the human body. Upon AIDS-induced immunosuppression or therapy-induced immunosuppression (required for organ transplant recipients or those suffering from autoimmune disorders), cryptococcal disease reactivates and causes life-threatening meningitis and pneumonia. This study showed that upon contact with the host, C. neoformans can quickly (a few hours) reach the host brain and also colonizes the nose of infected animals. Therefore, this work paves the way to better knowledge of how C. neoformans travels through the host body. Understanding how C. neoformans infects, disseminates, and survives within the host is critically required so that we can prevent infections and the disease caused by this deadly fungus.
Collapse
Affiliation(s)
- Carolina Coelho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
- Medical Research Council Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Aberdeen, United Kingdom
- Department of Biosciences, College of Life and Environmental Sciences, University of Exeter, Exeter, United Kingdom
| | - Emma Camacho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Antonio Salas
- Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Alexandre Alanio
- Institut Pasteur, Molecular Mycology Unit, CNRS UMR2000, Université Paris Diderot, Sorbonne Paris Cité, 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
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore, Maryland, USA
| |
Collapse
|
87
|
Denham ST, Wambaugh MA, Brown JCS. How Environmental Fungi Cause a Range of Clinical Outcomes in Susceptible Hosts. J Mol Biol 2019; 431:2982-3009. [PMID: 31078554 PMCID: PMC6646061 DOI: 10.1016/j.jmb.2019.05.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2019] [Revised: 04/18/2019] [Accepted: 05/01/2019] [Indexed: 12/11/2022]
Abstract
Environmental fungi are globally ubiquitous and human exposure is near universal. However, relatively few fungal species are capable of infecting humans, and among fungi, few exposure events lead to severe systemic infections. Systemic infections have mortality rates of up to 90%, cost the US healthcare system $7.2 billion annually, and are typically associated with immunocompromised patients. Despite this reputation, exposure to environmental fungi results in a range of outcomes, from asymptomatic latent infections to severe systemic infection. Here we discuss different exposure outcomes for five major fungal pathogens: Aspergillus, Blastomyces, Coccidioides, Cryptococcus, and Histoplasma species. These fungi include a mold, a budding yeast, and thermal dimorphic fungi. All of these species must adapt to dramatically changing environments over the course of disease. These dynamic environments include the human lung, which is the first exposure site for these organisms. Fungi must defend themselves against host immune cells while germinating and growing, which risks further exposing microbe-associated molecular patterns to the host. We discuss immune evasion strategies during early infection, from disruption of host immune cells to major changes in fungal cell morphology.
Collapse
Affiliation(s)
- Steven T Denham
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Morgan A Wambaugh
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Salt Lake City, UT 84132, USA
| | - Jessica C S Brown
- Division of Microbiology and Immunology, Pathology Department, University of Utah School of Medicine, Salt Lake City, UT 84132, USA.
| |
Collapse
|
88
|
Role of Amino Acid Metabolism in the Virulence of Human Pathogenic Fungi. CURRENT CLINICAL MICROBIOLOGY REPORTS 2019. [DOI: 10.1007/s40588-019-00124-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
|
89
|
Studying fungal pathogens of humans and fungal infections: fungal diversity and diversity of approaches. Microbes Infect 2019; 21:237-245. [PMID: 31255676 DOI: 10.1016/j.micinf.2019.06.011] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/26/2022]
Abstract
Seminal work by Louis Pasteur revealed the contribution of fungi - yeasts and microsporidia to agroindustry and disease in animals, respectively. More than 150 years later, the impact of fungi on human health and beyond is an ever-increasing issue, although often underestimated. Recent studies estimate that fungal infections, especially those caused by Candida, Cryptococcus and Aspergillus species, kill more than one million people annually. Indeed, these neglected infections are in general very difficult to cure and the associated mortality remains very high even when antifungal treatments exist. The development of new antifungals and diagnostic tools that are both necessary to fight fungal diseases efficiently, requires greater insights in the biology of the fungal pathogens of humans in the context of the infection, on their epidemiology, and on their role in the human mycobiota. We also need a better understanding of the host immune responses to fungal pathogens as well as the genetic basis for the increased sensitivity of some individuals to fungal infections. Here, we highlight some recent progress made in these different areas of research, in particular based on work conducted in our own laboratories. These progresses should lay the ground for better management of fungal infections, as they provide opportunities for better diagnostic, vaccination, the development of classical antifungals but also strategies for targeting virulence factors or the host.
Collapse
|
90
|
Caza M, Kronstad JW. The cAMP/Protein Kinase a Pathway Regulates Virulence and Adaptation to Host Conditions in Cryptococcus neoformans. Front Cell Infect Microbiol 2019; 9:212. [PMID: 31275865 PMCID: PMC6592070 DOI: 10.3389/fcimb.2019.00212] [Citation(s) in RCA: 43] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2019] [Accepted: 05/31/2019] [Indexed: 12/28/2022] Open
Abstract
Nutrient sensing is critical for adaptation of fungi to environmental and host conditions. The conserved cAMP/PKA signaling pathway contributes to adaptation by sensing the availability of key nutrients such as glucose and directing changes in gene expression and metabolism. Interestingly, the cAMP/PKA pathway in fungal pathogens also influences the expression of virulence determinants in response to nutritional and host signals. For instance, protein kinase A (PKA) in the human pathogen Cryptococcus neoformans plays a central role in orchestrating phenotypic changes, such as capsule elaboration and melanin production, that directly impact disease development. In this review, we focus first on insights into the role of the cAMP/PKA pathway in nutrient sensing for the model yeast Saccharomyces cerevisiae to provide a foundation for understanding the pathway in C. neoformans. We then discuss key features of cAMP/PKA signaling in C. neoformans including new insights emerging from the analysis of transcriptional and proteomic changes in strains with altered PKA activity and expression. Finally, we highlight recent studies that connect the cAMP/PKA pathway to cell surface remodeling and the formation of titan cells.
Collapse
Affiliation(s)
- Mélissa Caza
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| | - James W Kronstad
- Michael Smith Laboratories, Department of Microbiology and Immunology, University of British Columbia, Vancouver, BC, Canada
| |
Collapse
|
91
|
Maryam M, Fu MS, Alanio A, Camacho E, Goncalves DS, Faneuff EE, Grossman NT, Casadevall A, Coelho C. The enigmatic role of fungal annexins: the case of Cryptococcus neoformans. MICROBIOLOGY-SGM 2019; 165:852-862. [PMID: 31140968 DOI: 10.1099/mic.0.000815] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Annexins are multifunctional proteins that bind to phospholipid membranes in a calcium-dependent manner. Annexins play a myriad of critical and well-characterized roles in mammals, ranging from membrane repair to vesicular secretion. The role of annexins in the kingdoms of bacteria, protozoa and fungi have been largely overlooked. The fact that there is no known homologue of annexins in the yeast model organism Saccharomyces cerevisiae may contribute to this gap in knowledge. However, annexins are found in most medically important fungal pathogens, with the notable exception of Candida albicans. In this study we evaluated the function of the one annexin gene in Cryptococcus neoformans, a causative agent of cryptococcosis. This gene CNAG_02415, is annotated in the C. neoformans genome as a target of calcineurin through its transcription factor Crz1, and we propose to update its name to cryptococcal annexin, AnnexinC1. C. neoformans strains deleted for AnnexinC1 revealed no difference in survival after exposure to various chemical stressors relative to wild-type strain, as well as no major alteration in virulence or mating. The only alteration observed in strains deleted for AnnexinC1 was a small increase in the titan cells' formation in vitro. The preservation of annexins in many different fungal species suggests an important function, and therefore the lack of a strong phenotype for annexin-deficient C. neoformans indicates either the presence of redundant genes that can compensate for the absence of AnnexinC1 function or novel functions not revealed by standard assays of cell function and pathogenicity.
Collapse
Affiliation(s)
- Maria Maryam
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Man Shun Fu
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Alexandre Alanio
- Institut Pasteur, Molecular Mycology Unit, CNRS UMR2000, Université Paris Diderot, Sorbonne Paris Cité ; Laboratoire de Parasitologie-Mycologie, Hôpital Saint-Louis, Groupe Hospitalier Lariboisière, Saint-Louis, Fernand Widal, Assistance Publique-Hôpitaux de Paris (AP-HP), Paris, France.,W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Emma Camacho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Diego S Goncalves
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,Universidade Federal Fluminense, Rio Janeiro, Brazil
| | - Eden E Faneuff
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,Department of Biological Sciences, California State Polytechnic University, Pomona CA, USA
| | - Nina T Grossman
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Arturo Casadevall
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA
| | - Carolina Coelho
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins University Bloomberg School of Public Health, Baltimore MD, USA.,College of Life and Environmental Sciences, University of Exeter, Stocker Road, Exeter EX4 4QD, UK.,Medical Research Council Centre for Medical Mycology, Institute of Medical Sciences, University of Aberdeen, Ashgrove Road West, Aberdeen AB252ZD, UK
| |
Collapse
|
92
|
de Oliveira HC, Trevijano-Contador N, Garcia-Rodas R. Cryptococcal Pathogenicity and Morphogenesis. CURRENT FUNGAL INFECTION REPORTS 2019. [DOI: 10.1007/s12281-019-00340-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
|
93
|
Studying fungal pathogens of humans and fungal infections: fungal diversity and diversity of approaches. Genes Immun 2019; 20:403-414. [PMID: 31019254 DOI: 10.1038/s41435-019-0071-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Accepted: 04/15/2019] [Indexed: 12/24/2022]
Abstract
Seminal work by Louis Pasteur revealed the contribution of fungi-yeasts and microsporidia to agroindustry and disease in animals, respectively. More than 150 years later, the impact of fungi on human health and beyond is an ever-increasing issue, although often underestimated. Recent studies estimate that fungal infections, especially those caused by Candida, Cryptococcus and Aspergillus species, kill more than one million people annually. Indeed, these neglected infections are in general very difficult to cure and the associated mortality remains very high even when antifungal treatments exist. The development of new antifungals and diagnostic tools that are both necessary to fight fungal diseases efficiently, requires greater insights in the biology of the fungal pathogens of humans in the context of the infection, on their epidemiology, and on their role in the human mycobiota. We also need a better understanding of the host immune responses to fungal pathogens as well as the genetic basis for the increased sensitivity of some individuals to fungal infections. Here, we highlight some recent progress made in these different areas of research, in particular based on work conducted in our own laboratories. These progress should lay the ground for better management of fungal infections, as they provide opportunities for better diagnostic, vaccination, the development of classical antifungals but also strategies for targeting virulence factors or the host.
Collapse
|
94
|
The Mouse Inhalation Model of Cryptococcus neoformans Infection Recapitulates Strain Virulence in Humans and Shows that Closely Related Strains Can Possess Differential Virulence. Infect Immun 2019; 87:IAI.00046-19. [PMID: 30833336 DOI: 10.1128/iai.00046-19] [Citation(s) in RCA: 34] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 02/22/2019] [Indexed: 12/30/2022] Open
Abstract
Cryptococcal meningitis (CM) causes high rates of HIV-related mortality, yet the Cryptococcus factors influencing patient outcome are not well understood. Pathogen-specific traits, such as the strain genotype and degree of antigen shedding, are associated with the clinical outcome, but the underlying biology remains elusive. In this study, we examined factors determining disease outcome in HIV-infected cryptococcal meningitis patients infected with Cryptococcus neoformans strains with the same multilocus sequence type (MLST). Both patient mortality and survival were observed during infections with the same sequence type. Disease outcome was not associated with the patient CD4 count. Patient mortality was associated with higher cryptococcal antigen levels, the cerebrospinal fluid (CSF) fungal burden by quantitative culture, and low CSF fungal clearance. The virulence of a subset of clinical strains with the same sequence type was analyzed using a mouse inhalation model of cryptococcosis. We showed a strong association between human and mouse mortality rates, demonstrating that the mouse inhalation model recapitulates human infection. Similar to human infection, the ability to multiply in vivo, demonstrated by a high fungal burden in lung and brain tissues, was associated with mouse mortality. Mouse survival time was not associated with single C. neoformans virulence factors in vitro or in vivo; rather, a trend in survival time correlated with a suite of traits. These observations show that MLST-derived genotype similarities between C. neoformans strains do not necessarily translate into similar virulence either in the mouse model or in human patients. In addition, our results show that in vitro assays do not fully reproduce in vivo conditions that influence C. neoformans virulence.
Collapse
|
95
|
The Spectrum of Interactions between Cryptococcus neoformans and Bacteria. J Fungi (Basel) 2019; 5:jof5020031. [PMID: 31013706 PMCID: PMC6617360 DOI: 10.3390/jof5020031] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2019] [Revised: 04/08/2019] [Accepted: 04/11/2019] [Indexed: 01/08/2023] Open
Abstract
Cryptococcus neoformans is a major fungal pathogen that infects immunocompromised people and causes life-threatening meningoencephalitis. C. neoformans does not occur in isolation either in the environment or in the human host, but is surrounded by other microorganisms. Bacteria are ubiquitously distributed in nature, including soil, and make up the dominant part of the human microbiota. Pioneering studies in the 1950s demonstrated antifungal activity of environmental bacteria against C. neoformans. However, the mechanisms and implications of these interactions remain largely unknown. Recently, interest in polymicrobial interaction studies has been reignited by the development of improved sequencing methodologies, and by the realization that such interactions may have a huge impact on ecology and human health. In this review, we summarize our current understanding of the interaction of bacteria with C. neoformans.
Collapse
|
96
|
Chapuis AF, Ballou ER, MacCallum DM. A Bright Future for Fluorescence Imaging of Fungi in Living Hosts. J Fungi (Basel) 2019; 5:jof5020029. [PMID: 30987114 PMCID: PMC6616859 DOI: 10.3390/jof5020029] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Revised: 03/27/2019] [Accepted: 03/29/2019] [Indexed: 12/24/2022] Open
Abstract
Traditional in vivo investigation of fungal infection and new antifungal therapies in mouse models is usually carried out using post mortem methodologies. However, biomedical imaging techniques focusing on non-invasive techniques using bioluminescent and fluorescent proteins have become valuable tools. These new techniques address ethical concerns as they allow reduction in the number of animals required to evaluate new antifungal therapies. They also allow better understanding of the growth and spread of the pathogen during infection. In this review, we concentrate on imaging technologies using different fungal reporter proteins. We discuss the advantages and limitations of these different reporters and compare the efficacy of bioluminescent and fluorescent proteins for fungal research.
Collapse
Affiliation(s)
- Ambre F Chapuis
- MRC Centre for Medical Mycology at the University of Aberdeen, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
| | - Elizabeth R Ballou
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham B15 2TT, UK.
| | - Donna M MacCallum
- MRC Centre for Medical Mycology at the University of Aberdeen, Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, UK.
| |
Collapse
|
97
|
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: 11] [Impact Index Per Article: 2.2] [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.
Collapse
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
| |
Collapse
|
98
|
Brown AJ, Gow NA, Warris A, Brown GD. Memory in Fungal Pathogens Promotes Immune Evasion, Colonisation, and Infection. Trends Microbiol 2019; 27:219-230. [DOI: 10.1016/j.tim.2018.11.001] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2018] [Revised: 10/19/2018] [Accepted: 11/01/2018] [Indexed: 12/20/2022]
|
99
|
Phenotypic Variability Correlates with Clinical Outcome in Cryptococcus Isolates Obtained from Botswanan HIV/AIDS Patients. mBio 2018; 9:mBio.02016-18. [PMID: 30352938 PMCID: PMC6199498 DOI: 10.1128/mbio.02016-18] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Pathogenic species of Cryptococcus cause hundreds of thousands of deaths annually. Considerable phenotypic variation is exhibited during infection, including increased capsule size, capsule shedding, giant cells (≥15 μm), and micro cells (≤1 μm). We examined 70 clinical isolates of Cryptococcus neoformans and Cryptococcus tetragattii from HIV/AIDS patients in Botswana to determine whether the capacity to produce morphological variants was associated with clinical parameters. Isolates were cultured under conditions designed to simulate in vivo stresses. Substantial variation was seen across morphological and clinical data. Giant cells were more common in C. tetragattii, while micro cells and shed capsule occurred in C. neoformans only. Phenotypic variables fell into two groups associated with differing symptoms. The production of "large" phenotypes (greater cell and capsule size and giant cells) was associated with higher CD4 count and was negatively correlated with intracranial pressure indicators, suggesting that these are induced in early stage infection. "Small" phenotypes (micro cells and shed capsule) were associated with lower CD4 counts, negatively correlated with meningeal inflammation indicators, and positively correlated with intracranial pressure indicators, suggesting that they are produced later during infection and may contribute to immune suppression and promote proliferation and dissemination. These trends persisted at the species level, indicating that they were not driven by association with particular Cryptococcus species. Isolates possessing giant cells, micro cells, and shed capsule were rare, but strikingly, they were associated with patient death (P = 0.0165). Our data indicate that pleomorphism is an important driver in Cryptococcus infection.IMPORTANCE Cryptococcosis results in hundreds of thousands of deaths annually, predominantly in sub-Saharan Africa. Cryptococcus is an encapsulated yeast, and during infection, cells have the capacity for substantial morphological changes, including capsule enlargement and shedding and variations in cell shape and size. In this study, we examined 70 Cryptococcus isolates causing meningitis in HIV/AIDS patients in Botswana in order to look for associations between phenotypic variation and clinical symptoms. Four variant phenotypes were seen across strains: giant cells of ≥15 µm, micro cells of ≤1 µm, shed extracellular capsule, and irregularly shaped cells. We found that "large" and "small" phenotypes were associated with differing disease symptoms, indicating that their production may be important during the disease process. Overall, our study indicates that Cryptococcus strains that can switch on cell types under different situations may be more able to sustain infection and resist the host response.
Collapse
|
100
|
Zhou X, Ballou ER. The Cryptococcus neoformans Titan Cell: From In Vivo Phenomenon to In Vitro Model. CURRENT CLINICAL MICROBIOLOGY REPORTS 2018. [DOI: 10.1007/s40588-018-0107-9] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
|