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Cryptococcus neoformans Infection in the Central Nervous System: The Battle between Host and Pathogen. J Fungi (Basel) 2022; 8:jof8101069. [PMID: 36294634 PMCID: PMC9605252 DOI: 10.3390/jof8101069] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/28/2022] [Accepted: 10/07/2022] [Indexed: 11/17/2022] Open
Abstract
Cryptococcus neoformans (C. neoformans) is a pathogenic fungus with a global distribution. Humans become infected by inhaling the fungus from the environment, and the fungus initially colonizes the lungs. If the immune system fails to contain C. neoformans in the lungs, the fungus can disseminate to the blood and invade the central nervous system, resulting in fatal meningoencephalitis particularly in immunocompromised individuals including HIV/AIDS patients. Following brain invasion, C. neoformans will encounter host defenses involving resident as well as recruited immune cells in the brain. To overcome host defenses, C. neoformans possesses multiple virulence factors capable of modulating immune responses. The outcome of the interactions between the host and C. neoformans will determine the disease progression. In this review, we describe the current understanding of how C. neoformans migrates to the brain across the blood–brain barrier, and how the host immune system responds to the invading organism in the brain. We will also discuss the virulence factors that C. neoformans uses to modulate host immune responses.
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Abstract
Invasive fungal infections are emerging diseases that kill over 1.5 million people per year worldwide. With the increase of immunocompromised populations, the incidence of invasive fungal infections is expected to continue to rise. Vaccines for viral and bacterial infectious diseases have had a transformative impact on human health worldwide. However, no fungal vaccines are currently in clinical use. Recently, interest in fungal vaccines has grown significantly. One Candida vaccine has completed phase 2 clinical trials, and research on vaccines against coccidioidomycosis continues to advance. Additionally, multiple groups have discovered various Cryptococcus mutant strains that promote protective responses to subsequent challenge in mouse models. There has also been progress in antibody-mediated fungal vaccines. In this review, we highlight recent fungal vaccine research progress, outline the wealth of data generated, and summarize current research for both fungal biology and immunology studies relevant to fungal vaccine development. We also review technological advancements in vaccine development and highlight the future prospects of a human vaccine against invasive fungal infections.
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Affiliation(s)
- Amariliz Rivera
- Department of Pediatrics and Center for Immunity and Inflammation, Rutgers Biomedical and Health Sciences, Newark, New Jersey, USA;
| | - Jennifer Lodge
- Department of Molecular Microbiology, Washington University in St. Louis, St. Louis, Missouri, USA
- Current affiliation: Department of Molecular Genetics and Microbiology, Duke University, Durham, North Carolina, USA;
| | - Chaoyang Xue
- Public Health Research Institute and Department of Microbiology, Biochemistry and Molecular Genetics, Rutgers Biomedical and Health Sciences, Newark, New Jersey, USA;
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Rudman J, Evans RJ, Johnston SA. Are macrophages the heroes or villains during cryptococcosis? Fungal Genet Biol 2019; 132:103261. [DOI: 10.1016/j.fgb.2019.103261] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 08/06/2019] [Accepted: 08/06/2019] [Indexed: 10/26/2022]
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Pulmonary Iron Limitation Induced by Exogenous Type I IFN Protects Mice from Cryptococcus gattii Independently of T Cells. mBio 2019; 10:mBio.00799-19. [PMID: 31213551 PMCID: PMC6581853 DOI: 10.1128/mbio.00799-19] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Cryptococcus neoformans and Cryptococcus gattii cause fatal infection in immunodeficient and immunocompetent individuals. While these fungi are sibling species, C. gattii infects very few AIDS patients, while C. neoformans infection is an AIDS-defining illness, suggesting that the host response to HIV selects C. neoformans over C. gattii. We used a viral mimic molecule (pICLC) to stimulate the immune response, and pICLC treatment improved mouse outcomes from both species. pICLC-induced action against C. neoformans was due to activation of well-defined immune pathways known to deter C. neoformans, whereas these immune pathways were dispensable for pICLC treatment of C. gattii. Since these immune pathways are eventually destroyed by HIV/AIDS, our data help explain why the antiviral immune response in AIDS patients is unable to control C. neoformans infection but is protective against C. gattii. Furthermore, pICLC induced tighter control of iron in the lungs of mice, which inhibited C. gattii, thus suggesting an entirely new mode of nutritional immunity activated by viral signals. Cryptococcus neoformans causes deadly mycosis primarily in AIDS patients, whereas Cryptococcus gattii infects mostly non-HIV patients, even in regions with high burdens of HIV/AIDS and an established environmental presence of C. gattii. As HIV induces type I IFN (t1IFN), we hypothesized that t1IFN would differentially affect the outcome of C. neoformans and C. gattii infections. Exogenous t1IFN induction using stabilized poly(I·C) (pICLC) improved murine outcomes in either cryptococcal infection. In C. neoformans-infected mice, pICLC activity was associated with C. neoformans containment and classical Th1 immunity. In contrast, pICLC activity against C. gattii did not require any immune factors previously associated with C. neoformans immunity: T, B, and NK cells, IFN-γ, and macrophages were all dispensable. Interestingly, C. gattii pICLC activity depended on β-2-microglobulin, which impacts iron levels among other functions. Iron supplementation reversed pICLC activity, suggesting C. gattii pICLC activity requires iron limitation. Also, pICLC induced a set of iron control proteins, some of which were directly inhibitory to cryptococcus in vitro, suggesting t1IFN regulates iron availability in the pulmonary air space fluids. Thus, exogenous induction of t1IFN significantly improves the outcome of murine infection by C. gattii and C. neoformans but by distinct mechanisms; the C. gattii effect was mediated by iron limitation, while the effect on C. neoformans infection was through induction of classical T-cell-dependent immunity. Together this difference in types of T-cell-dependent t1IFN immunity for different Cryptococcus species suggests a possible mechanism by which HIV infection may select against C. gattii but not C. neoformans.
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Ikeda-Dantsuji Y, Nakamura S, Ohno H, Inukai T, Nagi M, Ueno K, Umeyama T, Kinjo Y, Yamagoe S, Shibuya K, Miyazaki Y. Intraspecies variation in the efficacy of adjunctive recombinant interferon-γ therapy against cryptococcal meningoencephalitis in mice. Med Mycol 2019; 56:382-386. [PMID: 28992282 DOI: 10.1093/mmy/myx063] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 08/09/2017] [Indexed: 12/20/2022] Open
Abstract
The efficacy of recombinant interferon γ (rIFN-γ) for cryptococcal meningoencephalitis has been poorly understood. Compared to Cryptococcus gattii, rIFN-γ significantly improved the survival in experimental meningoencephalitis due to Cryptococcus neoformans. The number of phagocytic macrophages and the levels of inflammatory cytokines production for ex vivo co-incubation with C. neoformans were increased after rIFN-γ stimulation but not C. gattii. Intraspecies differences of phagocytosis by the rIFN-γ-activated macrophages might be associated to the severity of cryptococcal infection.
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Affiliation(s)
- Yurika Ikeda-Dantsuji
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Shigeki Nakamura
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Hideaki Ohno
- Department of Infectious Diseases and Infection Control, Saitama Medical Center, Saitama Medical University, Saitama
| | - Tatsuya Inukai
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Minoru Nagi
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Keigo Ueno
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Takashi Umeyama
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Yuki Kinjo
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Satoshi Yamagoe
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
| | - Kazutoshi Shibuya
- Department of Pathology, Toho University School of Medicine, Tokyo, Japan
| | - Yoshitsugu Miyazaki
- Department of Chemotherapy and Mycoses, National Institute of Infectious Diseases, Tokyo
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Evans RJ, Pline K, Loynes CA, Needs S, Aldrovandi M, Tiefenbach J, Bielska E, Rubino RE, Nicol CJ, May RC, Krause HM, O’Donnell VB, Renshaw SA, Johnston SA. 15-keto-prostaglandin E2 activates host peroxisome proliferator-activated receptor gamma (PPAR-γ) to promote Cryptococcus neoformans growth during infection. PLoS Pathog 2019; 15:e1007597. [PMID: 30921435 PMCID: PMC6438442 DOI: 10.1371/journal.ppat.1007597] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2019] [Accepted: 01/25/2019] [Indexed: 12/19/2022] Open
Abstract
Cryptococcus neoformans is one of the leading causes of invasive fungal infection in humans worldwide. C. neoformans uses macrophages as a proliferative niche to increase infective burden and avoid immune surveillance. However, the specific mechanisms by which C. neoformans manipulates host immunity to promote its growth during infection remain ill-defined. Here we demonstrate that eicosanoid lipid mediators manipulated and/or produced by C. neoformans play a key role in regulating pathogenesis. C. neoformans is known to secrete several eicosanoids that are highly similar to those found in vertebrate hosts. Using eicosanoid deficient cryptococcal mutants Δplb1 and Δlac1, we demonstrate that prostaglandin E2 is required by C. neoformans for proliferation within macrophages and in vivo during infection. Genetic and pharmacological disruption of host PGE2 synthesis is not required for promotion of cryptococcal growth by eicosanoid production. We find that PGE2 must be dehydrogenated into 15-keto-PGE2 to promote fungal growth, a finding that implicated the host nuclear receptor PPAR-γ. C. neoformans infection of macrophages activates host PPAR-γ and its inhibition is sufficient to abrogate the effect of 15-keto-PGE2 in promoting fungal growth during infection. Thus, we describe the first mechanism of reliance on pathogen-derived eicosanoids in fungal pathogenesis and the specific role of 15-keto-PGE2 and host PPAR-γ in cryptococcosis. Cryptococcus neoformans is an opportunistic fungal pathogen that is responsible for significant numbers of deaths in the immunocompromised population worldwide. Here we address whether eicosanoids produced by C. neoformans manipulate host innate immune cells during infection. Cryptococcus neoformans produces several eicosanoids that are notable for their similarity to vertebrate eicosanoids, it is therefore possible that fungal-derived eicosanoids may provoke physiological effects in the host. Using a combination of in vitro and in vivo infection models we identify a specific eicosanoid species—prostaglandin E2 –that is required by C. neoformans for growth during infection. We subsequently show that prostaglandin E2 must be converted to 15-keto-prostaglandin E2 within the host before it has these effects. Furthermore, we find that prostaglandin E2/15-keto-prostaglandin E2 mediated virulence is via activation of host PPAR-γ –an intracellular eicosanoid receptor known to interact with 15-keto-PGE2.
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Affiliation(s)
- Robert J. Evans
- Bateson Centre, Firth Court, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, Medical School, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
| | - Katherine Pline
- Bateson Centre, Firth Court, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, Medical School, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
| | - Catherine A. Loynes
- Bateson Centre, Firth Court, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, Medical School, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
| | - Sarah Needs
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, West Midlands, United Kingdom
| | - Maceler Aldrovandi
- Systems Immunity Research Institute, and Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, South Glamorgan, United Kingdom
| | - Jens Tiefenbach
- Banting and Best Department of Medical Research, The Terrence Donnelly Centre for Cellular and Biomolecular Research (CCBR), University of Toronto, Toronto, Ontario, Canada
- InDanio Bioscience Inc., Toronto, Ontario, Canada
| | - Ewa Bielska
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, West Midlands, United Kingdom
| | - Rachel E. Rubino
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada
| | - Christopher J. Nicol
- Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada
| | - Robin C. May
- Institute of Microbiology and Infection, School of Biosciences, University of Birmingham, Birmingham, West Midlands, United Kingdom
| | - Henry M. Krause
- Banting and Best Department of Medical Research, The Terrence Donnelly Centre for Cellular and Biomolecular Research (CCBR), University of Toronto, Toronto, Ontario, Canada
- InDanio Bioscience Inc., Toronto, Ontario, Canada
| | - Valerie B. O’Donnell
- Systems Immunity Research Institute, and Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, South Glamorgan, United Kingdom
| | - Stephen A. Renshaw
- Bateson Centre, Firth Court, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, Medical School, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
| | - Simon A. Johnston
- Bateson Centre, Firth Court, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- Department of Infection, Immunity and Cardiovascular Disease, Medical School, University of Sheffield, Sheffield, South Yorkshire, United Kingdom
- * E-mail:
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Evans RJ, Sundaramurthy V, Frickel EM. The Interplay of Host Autophagy and Eukaryotic Pathogens. Front Cell Dev Biol 2018; 6:118. [PMID: 30271774 PMCID: PMC6146372 DOI: 10.3389/fcell.2018.00118] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2018] [Accepted: 08/29/2018] [Indexed: 12/11/2022] Open
Abstract
For intracellular pathogens, host cells provide a replicative niche, but are also armed with innate defense mechanisms to combat the intruder. Co-evolution of host and pathogens has produced a complex interplay of host-pathogen interactions during infection, with autophagy emerging as a key player in the recent years. Host autophagy as a degradative process is a significant hindrance to intracellular growth of the pathogens, but also can be subverted by the pathogens to provide support such as nutrients. While the role of host cell autophagy in the pathogenesis mechanisms of several bacterial and viral pathogens have been extensively studied, less is known for eukaryotic pathogens. In this review, we focus on the interplay of host autophagy with the eukaryotic pathogens Plasmodium spp, Toxoplasma, Leishmania spp and the fungal pathogens Candida albicans, Aspergillus fumigatus and Cryptococcus neoformans. The differences between these eukaryotic pathogens in terms of the host cell types they infect, infective strategies and the host responses required to defend against them provide an interesting insight into how they respond to and interact with host cell autophagy. Due to the ability to infect multiple host species and cell types during the course of their usually complex lifestyles, autophagy plays divergent roles even for the same pathogen. The scenario is further compounded since many of the eukaryotic pathogens have their own sets of either complete or partial autophagy machinery. Eukaryotic pathogen-autophagy interplay is thus a complex relationship with many novel insights for the basic understanding of autophagy, and potential for clinical relevance.
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Affiliation(s)
- Robert J. Evans
- Host-Toxoplasma Interaction Laboratory, The Francis Crick Institute, London, United Kingdom
| | | | - Eva-Maria Frickel
- Host-Toxoplasma Interaction Laboratory, The Francis Crick Institute, London, United Kingdom
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Garelnabi M, May RC. Variability in innate host immune responses to cryptococcosis. Mem Inst Oswaldo Cruz 2018; 113:e180060. [PMID: 29668826 PMCID: PMC5909084 DOI: 10.1590/0074-02760180060] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2018] [Accepted: 03/02/2018] [Indexed: 12/22/2022] Open
Abstract
Cryptococcosis is an invasive fungal disease caused by Cryptococcus neoformans and the closely related species C. gattii. The severe form of the disease, cryptococcal meningitis (CM), is rapidly fatal without treatment. Although typically a disease of immunocompromised (especially HIV-positive) individuals, there is growing awareness of cryptococcal disease amongst non-immunocompromised patients. Whilst substantial progress has been made in understanding the pathogenicity of C. neoformans in HIV patients, prospective data on cryptococcosis outside the context of HIV remains lacking. Below we review how innate immune responses vary between hosts depending on immunological status, and discuss risk factors and predictors of disease outcome in different groups.
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Affiliation(s)
- Mariam Garelnabi
- School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, UK
| | - Robin C May
- School of Biosciences, Institute of Microbiology and Infection, University of Birmingham, Edgbaston, Birmingham, UK
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Oliveira LVN, Costa MC, Magalhães TFF, Bastos RW, Santos PC, Carneiro HCS, Ribeiro NQ, Ferreira GF, Ribeiro LS, Gonçalves APF, Fagundes CT, Pascoal-Xavier MA, Djordjevic JT, Sorrell TC, Souza DG, Machado AMV, Santos DA. Influenza A Virus as a Predisposing Factor for Cryptococcosis. Front Cell Infect Microbiol 2017; 7:419. [PMID: 29018774 PMCID: PMC5622999 DOI: 10.3389/fcimb.2017.00419] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2017] [Accepted: 09/11/2017] [Indexed: 12/25/2022] Open
Abstract
Influenza A virus (IAV) infects millions of people annually and predisposes to secondary bacterial infections. Inhalation of fungi within the Cryptococcus complex causes pulmonary disease with secondary meningo-encephalitis. Underlying pulmonary disease is a strong risk factor for development of C. gattii cryptococcosis though the effect of concurrent infection with IAV has not been studied. We developed an in vivo model of Influenza A H1N1 and C. gattii co-infection. Co-infection resulted in a major increase in morbidity and mortality, with severe lung damage and a high brain fungal burden when mice were infected in the acute phase of influenza multiplication. Furthermore, IAV alters the host response to C. gattii, leading to recruitment of significantly more neutrophils and macrophages into the lungs. Moreover, IAV induced the production of type 1 interferons (IFN-α4/β) and the levels of IFN-γ were significantly reduced, which can be associated with impairment of the immune response to Cryptococcus during co-infection. Phagocytosis, killing of cryptococci and production of reactive oxygen species (ROS) by IAV-infected macrophages were reduced, independent of previous IFN-γ stimulation, leading to increased proliferation of the fungus within macrophages. In conclusion, IAV infection is a predisposing factor for severe disease and adverse outcomes in mice co-infected with C. gattii.
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Affiliation(s)
- Lorena V N Oliveira
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Marliete C Costa
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Thaís F F Magalhães
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Rafael W Bastos
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Patrícia C Santos
- Laboratório de Interação Micro-organismo Hospedeiro, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Hellem C S Carneiro
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Noelly Q Ribeiro
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Gabriella F Ferreira
- Departamento de Farmácia, Universidade Federal de Juiz de Fora-Campus Governador Valadares, Centro, Governador Valadares, Brazil
| | - Lucas S Ribeiro
- Laboratório de Interação Micro-organismo Hospedeiro, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Ana P F Gonçalves
- Centro de Pesquisas René Rachou (CPqRR)/Fundação Oswaldo Cruz (Fiocruz Minas), Belo Horizonte, Brazil
| | - Caio T Fagundes
- Laboratório de Interação Micro-organismo Hospedeiro, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil.,Centro de Pesquisa e Desenvolvimento de Fármacos, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Marcelo A Pascoal-Xavier
- Centro de Pesquisas René Rachou (CPqRR)/Fundação Oswaldo Cruz (Fiocruz Minas), Belo Horizonte, Brazil
| | - Julianne T Djordjevic
- Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney and Westmead Institute for Medical Research, Westmead, NSW, Australia
| | - Tania C Sorrell
- Marie Bashir Institute for Infectious Diseases and Biosecurity, University of Sydney and Westmead Institute for Medical Research, Westmead, NSW, Australia
| | - Daniele G Souza
- Laboratório de Interação Micro-organismo Hospedeiro, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
| | - Alexandre M V Machado
- Centro de Pesquisas René Rachou (CPqRR)/Fundação Oswaldo Cruz (Fiocruz Minas), Belo Horizonte, Brazil
| | - Daniel A Santos
- Laboratório de Micologia, Departamento de Microbiologia, Instituto de Ciências Biológicas, Federal University of Minas Gerais, Belo Horizonte, Brazil
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The CSF Immune Response in HIV-1-Associated Cryptococcal Meningitis: Macrophage Activation, Correlates of Disease Severity, and Effect of Antiretroviral Therapy. J Acquir Immune Defic Syndr 2017; 75:299-307. [PMID: 28346317 PMCID: PMC5469563 DOI: 10.1097/qai.0000000000001382] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Supplemental Digital Content is Available in the Text. Background: Immune modulation may improve outcome in HIV-associated cryptococcal meningitis. Animal studies suggest alternatively activated macrophages are detrimental but human studies are limited. We performed a detailed assessment of the cerebrospinal fluid (CSF) immune response and examined immune correlates of disease severity and poor outcome, and the effects of antiretroviral therapy (ART). Methodology: We enrolled persons ≥18 years with first episode of HIV-associated cryptococcal meningitis. CSF immune response was assessed using flow cytometry and multiplex cytokine analysis. Principal component analysis was used to examine relationships between immune response, fungal burden, intracranial pressure and mortality, and the effects of recent ART initiation (<12 weeks). Findings: CSF was available from 57 persons (median CD4 34/μL). CD206 (alternatively activated macrophage marker) was expressed on 54% CD14+ and 35% CD14− monocyte-macrophages. High fungal burden was not associated with CD206 expression but with a paucity of CD4+, CD8+, and CD4−CD8− T cells and lower interleukin-6, G-CSF, and interleukin-5 concentrations. High intracranial pressure (≥30 cm H2O) was associated with fewer T cells, a higher fungal burden, and larger Cryptococcus organisms. Mortality was associated with reduced interferon-gamma concentrations and CD4−CD8− T cells but lost statistical significance when adjusted for multiple comparisons. Recent ART was associated with increased CSF CD4/CD8 ratio and a significantly increased macrophage expression of CD206. Conclusions: Paucity of CSF T cell infiltrate rather than alternative macrophage activation was associated with severe disease in HIV-associated cryptococcosis. ART had a pronounced effect on the immune response at the site of disease.
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Tenforde MW, Scriven JE, Harrison TS, Jarvis JN. Immune correlates of HIV-associated cryptococcal meningitis. PLoS Pathog 2017; 13:e1006207. [PMID: 28334020 PMCID: PMC5363984 DOI: 10.1371/journal.ppat.1006207] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Affiliation(s)
- Mark W. Tenforde
- Division of Allergy and Infectious Diseases, University of Washington School of Medicine, Seattle, Washington, United States of America
- Department of Epidemiology, University of Washington School of Public Health, Seattle, Washington, United States of America
- * E-mail:
| | - James E. Scriven
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Thomas S. Harrison
- Institute for Infection and Immunity, St George’s, University of London, London, United Kingdom
- St George’s University Hospitals NHS Foundation Trust, London, United Kingdom
- Institute of Infectious Diseases and Molecular Medicine, University of Cape Town, Cape Town, South Africa
| | - Joseph N. Jarvis
- Botswana-UPenn Partnership, Gaborone, Botswana
- Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, United States of America
- Department of Clinical Research, Faculty of Infectious Diseases and Tropical Medicine, London School of Hygiene and Tropical Medicine, London, United Kingdom
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Fisher JF, Valencia-Rey PA, Davis WB. Pulmonary Cryptococcosis in the Immunocompetent Patient-Many Questions, Some Answers. Open Forum Infect Dis 2016; 3:ofw167. [PMID: 27704021 PMCID: PMC5047412 DOI: 10.1093/ofid/ofw167] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2016] [Accepted: 07/29/2016] [Indexed: 12/21/2022] Open
Abstract
Background. There are no prospective data regarding the management of pulmonary cryptococcosis in the immunocompetent patient. Clinical guidelines recommend oral fluconazole for patients with mild to moderate symptoms and amphotericin B plus flucytosine followed by fluconazole for severe disease. It is unclear whether patients who have histological evidence of Cryptococcus neoformans but negative cultures will even respond to drug treatment. We evaluated and managed a patient whose presentation and course raised important questions regarding the significance of negative cultures, antifungal choices, duration of therapy, and resolution of clinical, serologic, and radiographic findings. Methods. In addition to our experience, to answer these questions we reviewed available case reports and case series regarding immunocompetent patients with pulmonary cryptococcosis for the last 55 years using the following definitions: Definite - Clinical and/or radiographic findings of pulmonary infection and respiratory tract isolation of C. neoformans without other suspected etiologies; Probable - Clinical and radiographic findings of pulmonary infection, histopathologic evidence of C. neoformans, and negative fungal cultures with or without a positive cryptococcal polysaccharide antigen. Results. Pulmonary cryptococcosis resolves in most patients with or without specific antifungal therapy. Clinical, radiographic, and serologic resolution is slow and may take years. Conclusions. Persistently positive antigen titers are most common in untreated patients and may remain strongly positive despite complete or partial resolution of disease. Respiratory fungal cultures are often negative and may indicate nonviable organisms.
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Grebenciucova E, Reder AT, Bernard JT. Immunologic mechanisms of fingolimod and the role of immunosenescence in the risk of cryptococcal infection: A case report and review of literature. Mult Scler Relat Disord 2016; 9:158-62. [PMID: 27645366 DOI: 10.1016/j.msard.2016.07.015] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2016] [Revised: 07/10/2016] [Accepted: 07/25/2016] [Indexed: 12/31/2022]
Abstract
BACKGROUND Fingolimod is a disease-modifying agent used in the treatment of relapsing/remitting multiple sclerosis. In MS clinical studies, the overall rate of infections in fingolimod group was overall similar to placebo, except for slightly more common lower respiratory tract infections and to a lesser extent HSV. Recently, an increasing number of cryptococcal infections associated with a long-term use of this medication have been reported. METHODS We reviewed literature for cases of cryptococcal infection associated with the use of fingolimod and reported a case at our institution, as well as carefully evaluated the established immune mechanisms of the medication and discussed new insights into its short-term and long-term immunologic effects that may become important in the context of risk of infection. RESULTS Unique characteristics of cryptococcal pathogen, its immune escape mechanisms, its ability to establish a latent infection with a potential for later reactivation, fingolimod's effects on many lines of immune system, both quantitatively and qualitatively, duration of therapy, and long-term effects of fingolimod, not previously described, in conjunction with effects of natural immunosenescence of the patient population, that appears to be most at risk, may be meaningful in further understanding the risk of infection with long-term use of fingolimod in people of older age.
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Affiliation(s)
| | - Anthony T Reder
- University of Chicago, Department of Neurology, Chicago, IL, United States
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DeLeon-Rodriguez CM, Casadevall A. Cryptococcus neoformans: Tripping on Acid in the Phagolysosome. Front Microbiol 2016; 7:164. [PMID: 26925039 PMCID: PMC4756110 DOI: 10.3389/fmicb.2016.00164] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 02/01/2016] [Indexed: 01/10/2023] Open
Abstract
Cryptococcus neoformans (Cn) is a basidiomycetous pathogenic yeast that is a frequent cause of meningoencephalitis in immunocompromised individuals. Cn is a facultative intracellular pathogen in mammals, insects and amoeba. Cn infection occurs after inhalation of spores or desiccated cells from the environment. After inhalation Cn localizes to the lungs where it can be phagocytosed by alveolar macrophages. Cn is surrounded by a polysaccharide capsule that helps the fungus survive in vivo by interfering with phagocytosis, quenching free radical bursts and shedding polysaccharides that negatively modulates the immune system. After phagocytosis, Cn resides within the phagosome that matures to become a phagolysosome, a process that results in the acidification of the phagolysosomal lumen. Cn replicates at a higher rate inside macrophages than in the extracellular environment, possibly as a result that the phagosomal pH is near that optimal for growth. Cn increases the phagolysosomal pH and modulates the dynamics of Rab GTPases interaction with the phagolysosome. Chemical manipulation of the phagolysosomal pH with drugs can result in direct and indirect killing of Cn and reduced non-lytic exocytosis. Phagolysosomal membrane damage after Cn infection occurs both in vivo and in vitro, and is required for Cn growth and survival. Macrophage treatment with IFN-γ reduces the phagolysosomal damage and increases intracellular killing of Cn. Studies on mice and humans show that treatment with IFN-γ can improve host control of the disease. However, the mechanism by which Cn mediates phagolysosomal membrane damage remains unknown but likely candidates are phospholipases and mechanical damage from an enlarging capsule. Here we review Cn intracellular interaction with a particular emphasis on phagosomal interactions and develop the notion that the extent of damage of the phagosomal membrane is a key determinant of the outcome of the Cn-macrophage interaction.
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Affiliation(s)
| | - Arturo Casadevall
- Department of Microbiology and Immunology, Albert Einstein College of Medicine, BronxNY, USA; Department of Molecular Microbiology and Immunology, Johns Hopkins University School of Public Health, BaltimoreMD, USA
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15
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Scriven JE, Graham LM, Schutz C, Scriba TJ, Wilkinson KA, Wilkinson RJ, Boulware DR, Urban BC, Lalloo DG, Meintjes G. A Glucuronoxylomannan-Associated Immune Signature, Characterized by Monocyte Deactivation and an Increased Interleukin 10 Level, Is a Predictor of Death in Cryptococcal Meningitis. J Infect Dis 2016; 213:1725-34. [PMID: 26768248 PMCID: PMC4857465 DOI: 10.1093/infdis/jiw007] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2015] [Accepted: 12/23/2015] [Indexed: 11/14/2022] Open
Abstract
Background. Cryptococcal meningitis remains a significant cause of death among human immunodeficiency virus type 1 (HIV)–infected persons in Africa. We aimed to better understand the pathogenesis and identify immune correlates of mortality, particularly the role of monocyte activation. Methods. A prospective cohort study was conducted in Cape Town, South Africa. Patients with a first episode of cryptococcal meningitis were enrolled, and their immune responses were assessed in unstimulated and stimulated blood specimens, using flow cytometry and cytokine analysis. Results. Sixty participants were enrolled (median CD4+ T-cell count, 34 cells/µL). Mortality was 23% (14 of 60 participants) at 14 days and 39% (22 of 57) at 12 weeks. Nonsurvivors were more likely to have an altered consciousness and higher cerebrospinal fluid fungal burden at presentation. Principal component analysis identified an immune signature associated with early mortality, characterized by monocyte deactivation (reduced HLA-DR expression and tumor necrosis factor α response to lipopolysaccharide); increased serum interleukin 6, CXCL10, and interleukin 10 levels; increased neutrophil counts; and decreased T-helper cell type 1 responses. This immune signature remained an independent predictor of early mortality after adjustment for consciousness level and fungal burden and was associated with higher serum titers of cryptococcal glucuronoxylomannan. Conclusions. Cryptococcal-related mortality is associated with monocyte deactivation and an antiinflammatory blood immune signature, possibly due to Cryptococcus modulation of the host immune response. Validation in other cohorts is required.
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Affiliation(s)
- James E Scriven
- Liverpool School of Tropical Medicine Wellcome Trust Liverpool Glasgow Centre for Global Health Research, Liverpool Clinical Infectious Diseases Research Initiative Department of Medicine, University of Cape Town and Groote Schuur Hospital, South Africa
| | | | - Charlotte Schutz
- Clinical Infectious Diseases Research Initiative Department of Medicine, University of Cape Town and Groote Schuur Hospital, South Africa
| | - Thomas J Scriba
- South African TB Vaccine Initiative, Institute of Infectious Disease and Molecular Medicine Department of Paediatrics and Child Health, University of Cape Town
| | | | - Robert J Wilkinson
- Department of Medicine, Imperial College London Mill Hill Laboratory, Francis Crick Institute, London, United Kingdom Clinical Infectious Diseases Research Initiative
| | | | | | - David G Lalloo
- Liverpool School of Tropical Medicine Wellcome Trust Liverpool Glasgow Centre for Global Health Research, Liverpool
| | - Graeme Meintjes
- Department of Medicine, Imperial College London Clinical Infectious Diseases Research Initiative Department of Medicine, University of Cape Town and Groote Schuur Hospital, South Africa
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16
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Effects of formaldehyde on lymphocyte subsets and cytokines in the peripheral blood of exposed workers. PLoS One 2014; 9:e104069. [PMID: 25157974 PMCID: PMC4144836 DOI: 10.1371/journal.pone.0104069] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Accepted: 07/06/2014] [Indexed: 11/19/2022] Open
Abstract
Formaldehyde (FA) is a well-known irritant, and it is suggested to increase the risk of immune diseases and cancer. The present study aimed to evaluate the distribution of major lymphocyte subsets and cytokine expression profiles in the peripheral blood of FA-exposed workers. A total of 118 FA-exposed workers and 79 controls were enrolled in the study. High performance liquid chromatography, flow cytometry, and cytometric bead array were used to analyze FA in air sample and formic acid in urine, blood lymphocyte subpopulations, and serum cytokines, respectively. The FA-exposed workers were divided into low and high exposure groups according to their exposure levels. The results showed that both the low and high FA-exposed groups had a significant increase of formic acid in urine when compared to the controls. Both the low and high exposure groups had a significant increase in the percentage of B cells (CD19+) compared to the control group (p<0.01). A significant increase in the percentage of the natural killer (NK) cells (CD56+) was observed in the low exposure group compared to the control (p = 0.013). Moreover, the FA-exposed workers in both exposure groups showed a significant higher level of IL-10 but lower level of IL-8 than the control (p<0.01). Subjects in the high exposure group had a higher level of IL-4 but a lower level of IFN-γ than the control (p<0.05). Finally, there is a significant correlation between the levels of IL-10, IL-4, and IL-8 and formic acid (p<0.05). The findings from the present study may explain, at least in part, the association between FA exposure and immune diseases and cancer.
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17
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Jarvis JN, Casazza JP, Stone HH, Meintjes G, Lawn SD, Levitz SM, Harrison TS, Koup RA. The phenotype of the Cryptococcus-specific CD4+ memory T-cell response is associated with disease severity and outcome in HIV-associated cryptococcal meningitis. J Infect Dis 2013; 207:1817-28. [PMID: 23493728 PMCID: PMC3654748 DOI: 10.1093/infdis/jit099] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Background. Correlates of immune protection in
patients with human immunodeficiency virus (HIV)–associated cryptococcal meningitis
are poorly defined. A clearer understanding of these immune responses is essential to
inform rational development of immunotherapies. Methods. Cryptococcal-specific peripheral
CD4+ T-cell responses were measured in 44 patients with HIV-associated
cryptococcal meningitis at baseline and during follow-up. Responses were assessed
following ex vivo cryptococcal mannoprotein stimulation, using 13-color flow-cytometry.
The relationships between cryptococcal-specific CD4+ T-cell responses,
clinical parameters at presentation, and outcome were investigated. Results. Cryptococcal-specific CD4+
T-cell responses were characterized by the production of macrophage inflammatory protein
1α, interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α).
Conversely, minimal interleukin 4 and interleukin 17 production was detected. Patients
surviving to 2 weeks had significantly different functional CD4+ T-cell
responses as compared to those who died. Patients with a response predominantly consisting
of IFN-γ or TNF-α production had a 2-week mortality of 0% (0/20), compared
with 25% (6/24) in those without this response (P = .025).
Such patients also had lower fungal burdens (10 400 vs 390 000 colony-forming units/mL;
P < .001), higher cerebrospinal fluid lymphocyte counts (122 vs 8
cells/μL; P < .001), and a trend toward faster rates of clearance
of infection. Conclusions. The phenotype of the peripheral
CD4+ T-cell response to Cryptococcus was associated
with disease severity and outcome in HIV-associated cryptococcal meningitis.
IFN-γ/TNF-α–predominant responses were associated with survival.
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Affiliation(s)
- Joseph N Jarvis
- Research Centre for Infection and Immunity, Division of Clinical Sciences, St. George's University of London,
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18
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Abstract
Despite appropriate antifungal treatment, the management of cryptococcal disease remains challenging, especially in immunocompromised patients, such as human immunodeficiency virus-infected individuals and solid organ transplant recipients. During the past two decades, our knowledge of host immune responses against Cryptococcus spp. has been greatly advanced, and the role of immunomodulation in augmenting the response to infection has been investigated. In particular, the role of 'protective' Th1 (tumour necrosis factor-α, interferon (IFN)-γ, interleukin (IL)-12, and IL-18) and Th17 (IL-23 and IL-17) and 'non-protective' Th2 (IL-4, IL-10, and IL-13) cytokines has been extensively studied in vitro and in animal models of cryptococcal infection. Immunomodulation with monoclonal antibodies against the capsular polysaccharide glucuronoxylomannan, glucosylceramides, melanin and β-glucan and, lately, with radioimmunotherapy has also yielded promising results in animal models. As a balance between sufficiently protective Th1 responses and excessive inflammation is important for optimal outcome, the effect of immunotherapy may range from beneficial to deleterious, depending on factors related to the host, the infecting organism, and the immunomodulatory regimen. Clinical evidence supporting immunomodulation in patients with cryptococcal infection remains too limited to allow firm recommendations. Limited human data suggest a role for IFN-γ. Identification of surrogate markers characterizing patients' immunological status could possibly suggest candidate patients for immunotherapy and the type of immunomodulation to be administered.
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Affiliation(s)
- C Antachopoulos
- 3rd Department of Paediatrics, Hippokration Hospital, Aristotle University, Thessaloniki, Greece
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19
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Piehler D, Stenzel W, Grahnert A, Held J, Richter L, Köhler G, Richter T, Eschke M, Alber G, Müller U. Eosinophils contribute to IL-4 production and shape the T-helper cytokine profile and inflammatory response in pulmonary cryptococcosis. THE AMERICAN JOURNAL OF PATHOLOGY 2011; 179:733-44. [PMID: 21699881 DOI: 10.1016/j.ajpath.2011.04.025] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/25/2011] [Revised: 03/14/2011] [Accepted: 04/05/2011] [Indexed: 12/15/2022]
Abstract
Susceptibility to infection with Cryptococcus neoformans is tightly determined by production of IL-4. In this study, we investigated the time course of IL-4 production and its innate cellular source in mice infected intranasally with C. neoformans. We show that pulmonary IL-4 production starts surprisingly late after 6 weeks of infection. Interestingly, in the lungs of infected mice, pulmonary T helper (Th) cells and eosinophils produce significant amounts of IL-4. In eosinophil-deficient ΔdblGATA mice, IL-33 receptor-expressing Th2s are significantly reduced, albeit not absent, whereas protective Th1 and Th17 responses are enhanced. In addition, recruitment of pulmonary inflammatory cells during infection with C. neoformans is reduced in the absence of eosinophils. These data expand previous findings emphasizing an exclusively destructive effector function by eosinophilic granulocytes. Moreover, in ΔdblGATA mice, fungal control is slightly enhanced in the lung; however, dissemination of Cryptococcus is not prevented. Therefore, eosinophils play an immunoregulatory role that contributes to Th2-dependent susceptibility in allergic inflammation during bronchopulmonary mycosis.
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Affiliation(s)
- Daniel Piehler
- Institute of Immunology, College of Veterinary Medicine, University of Leipzig, Leipzig, Germany
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20
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Petković L, Arsenijević VA, Skvarc M, Kopitar A, Kotnik V, Simicic S, Wraber B, Matos T, Ihan A. Anticryptococcal cytotoxicity of murine nonadherent cells is perforin and nonperforin mediated. Mycologia 2010; 102:552-9. [PMID: 20524588 DOI: 10.3852/09-039] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The encapsulated fungal pathogen Cryptococcus neoformans is a significant agent of life-threatening infections, particularly in people with suppressed cell-mediated immunity. The cellular cytotoxicity against C. neoformans infection is mainly mediated by NK and T cells, but effector mechanisms are not well understood. The objective of this study was (i) to determine whether prior exposure to the cryptococcal antigens enhances anticryptococcal activity of cytotoxic cells in mice and (ii) the contribution of perforin- and nonperforin-mediated cytotoxicity of NK and T cells in growth inhibition of C. neoformans. Our data showed that in vitro exposure of nonadherent (NA) spleen mononuclear cells from nonimmunized mice to heat-killed C. neoformans strain Cap67 unencapsulated mutant of B3501 (Ag1) or its supernatant (Ag2) demonstrated higher anticryptococcal activity. This effector mechanism can be enhanced further after immunization with either Ag1 or Ag2. There is a synergistic effect of immunization and in vitro incubation of the NA cells with the same antigens. Concanamycin A (CMA) and strontium chloride (SrCl2) inhibition assays were performed to clarify the contribution of perforin- and nonperforin-mediated anticryptococcal cytotoxicity of NA cells in these events. Treatment with these inhibitors demonstrated that anticryptococcal cytotoxicity of nonprimed NA cells was primarily perforin mediated. Anticryptococcal activity of the NA cells obtained from immunized mice after in vitro incubation with cryptococcal antigens was both perforin and nonperforin mediated. Taken together these data demonstrate that in mice a nonperforin-mediated pathway of anticryptococcal cytotoxicity can be induced by immunization. Further research is needed to examine their potential role for human vaccines strategies and/or therapies.
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Affiliation(s)
- Ljubica Petković
- Institute of Microbiology and Immunology, Faculty of Medicine, University of Belgrade, Dr Subotića 1, 11 000 Belgrade, Serbia.
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21
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Guo S, Bao L, Qin ZF, Shi XX. The CFP-10/ESAT-6 complex of Mycobacterium tuberculosis potentiates the activation of murine macrophages involvement of IFN-gamma signaling. Med Microbiol Immunol 2010; 199:129-37. [PMID: 20232079 DOI: 10.1007/s00430-010-0146-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2009] [Indexed: 11/28/2022]
Abstract
Secretory antigen of Mycobacterium tuberculosis, culture filtered protein 10(CFP-10) and early secreted antigenic target 6 kDa protein (ESAT-6) are closely correlated with immunogenicity and virulence of Mycobacterium tuberculosis. But the mechanism of its immunogenicity and virulence is still unclear. In this study, we investigated the influence of the CFP-10/ESAT-6 complex on production of IL-12 and nitric oxide (NO) produced by the ANA-1 macrophage cell line. Preincubation with the complex in a time-dependent manner significantly enhanced production of NO and IL-12 released from ANA-1 cells following IFN-gamma stimulation. In addition, the complex up-modulated expression level of IFN-gammaR1 on surface of the macrophages. Furthermore, the effect of the complex on production of IL-12 and NO in ANA-1 cells was suppressed by AG490, a selective inhibitor of JAK/STAT pathway. These data suggest that in the presence of IFN-gamma, CFP-10/ESAT-6 complex represents a new immunogenicity and protective factor that may be, at least partly, due to up modulation of IFN-gammaR1 expression and activation of JAK/STAT pathway.
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Affiliation(s)
- Si Guo
- Laboratory of West China Centre of Medical Sciences, Sichuan University, 610041, Chengdu, People's Republic of China
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22
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Abstract
Opportunistic pathogens have become of increasing medical importance over the last decade due to the AIDS pandemic. Not only is cryptococcosis the fourth-most-common fatal infectious disease in sub-Saharan Africa, but also Cryptococcus is an emerging pathogen of immunocompetent individuals. The interaction between Cryptococcus and the host's immune system is a major determinant for the outcome of disease. Despite initial infection in early childhood with Cryptococcus neoformans and frequent exposure to C. neoformans within the environment, immunocompetent individuals are generally able to contain the fungus or maintain the yeast in a latent state. However, immune deficiencies lead to disseminating infections that are uniformly fatal without rapid clinical intervention. This review will discuss the innate and adaptive immune responses to Cryptococcus and cryptococcal strategies to evade the host's defense mechanisms. It will also address the importance of these strategies in pathogenesis and the potential of immunotherapy in cryptococcosis treatment.
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23
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Sifri CD, Sun HY, Cacciarelli TV, Wispelwey B, Pruett TL, Singh N. Pretransplant cryptococcosis and outcome after liver transplantation. Liver Transpl 2010; 16:499-502. [PMID: 20373460 DOI: 10.1002/lt.22024] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
The posttransplant outcomes and optimal management of patients with end-stage liver disease who develop cryptococcosis prior to transplantation have not been defined. We discuss these issues in the context of successful liver transplantation and pretransplant cryptococcal disease. Our report suggests that liver transplantation may be cautiously considered under the umbrella of fluconazole therapy in patients with end-stage liver disease and pretransplant cryptococcosis, provided that disease control is achieved with adequate treatment before transplantation.
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Cytokine signaling regulates the outcome of intracellular macrophage parasitism by Cryptococcus neoformans. Infect Immun 2009; 77:3450-7. [PMID: 19487474 DOI: 10.1128/iai.00297-09] [Citation(s) in RCA: 120] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The pathogenic yeast Cryptococcus neoformans and C. gattii commonly cause severe infections of the central nervous system in patients with impaired immunity but also increasingly in immunocompetent individuals. Cryptococcus is phagocytosed by macrophages but can then survive and proliferate within the phagosomes of these infected host cells. Moreover, Cryptococcus is able to escape into the extracellular environment via a recently discovered nonlytic mechanism (termed expulsion or extrusion). Although it is well established that the host's cytokine profile dramatically affects the outcome of cryptococcal disease, the molecular basis for this effect is unclear. Here, we report a systematic analysis of the influence of Th1, Th2, and Th17 cytokines on the outcome of the interaction between macrophages and cryptococci. We show that Th1 and Th17 cytokines activate, whereas Th2 cytokines inhibit, anticryptococcal functions. Intracellular yeast proliferation was significantly lower after treatment with the Th1 cytokines gamma interferon and tumor necrosis factor alpha and the Th17 cytokine interleukin-17 (IL-17). Interestingly, however, the Th2 cytokines IL-4 and IL-13 significantly increased intracellular yeast proliferation while reducing the occurrence of pathogen expulsion. These results help explain the observed poor prognosis associated with the Th2 cytokine profile (e.g., in human immunodeficiency virus-infected patients).
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Abstract
Cryptococcus neoformans and Cryptococcus gattii are the cause of life-threatening meningoencephalitis in immunocompromised and immunocompetent individuals respectively. The increasing incidence of cryptococcal infection as a result of the AIDS epidemic, the recent emergence of a hypervirulent cryptococcal strain in Canada and the fact that mortality from cryptococcal disease remains high have stimulated intensive research into this organism. Here we outline recent advances in our understanding of C. neoformans and C. gattii, including intraspecific complexity, virulence factors, and key signaling pathways. We discuss the molecular basis of cryptococcal virulence and the interaction between these pathogens and the host immune system. Finally, we discuss future challenges in the study and treatment of cryptococcosis.
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Affiliation(s)
- Hansong Ma
- School of Biosciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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26
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Siegemund S, Alber G. Cryptococcus neoformans activates bone marrow-derived conventional dendritic cells rather than plasmacytoid dendritic cells and down-regulates macrophages. ACTA ACUST UNITED AC 2008; 52:417-27. [PMID: 18336384 DOI: 10.1111/j.1574-695x.2008.00391.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Induction of IL-12 and IL-23 is essential for protective immunity against Cryptococcusneoformans. The contribution of dendritic cells vs. macrophages to IL-12/23 production in response to C. neoformans infection is unclear. Activation of conventional bone marrow-derived dendritic cells (BMDC), plasmacytoid BMDC, and bone marrow-derived macrophages (BMMPhi) was assessed by analyzing cytokine responses and the expression of MHC-II, CD86, and CD80 in each cell type. Cryptococcus neoformans induced the release of IL-12/23p40 by BMDC, but not by BMMPhi, in a TLR2- and TLR4-independent but MyD88-dependent manner. Conventional BMDC rather than plasmacytoid BMDC up-regulated MHC-II and CD86, while BMMPhi down-regulated MHC-II and CD86 in response to C. neoformans. The up-regulation of MHC-II and CD86 on BMDC required MyD88. Our data point to conventional DC as critical IL-12/23-producing antigen-presenting cells during cryptococcosis.
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Affiliation(s)
- Sabine Siegemund
- Institute of Immunology, College of Veterinary Medicine, Leipzig, Germany
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Capilla J, Clemons KV, Stevens DA. Animal models: an important tool in mycology. Med Mycol 2007; 45:657-84. [PMID: 18027253 PMCID: PMC7107685 DOI: 10.1080/13693780701644140] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 08/22/2007] [Indexed: 10/29/2022] Open
Abstract
Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.
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Affiliation(s)
- Javier Capilla
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
| | - Karl V. Clemons
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
| | - David A. Stevens
- California Institute for Medical Research, San Jose, USA
- Department of Medicine, Division of Infectious Diseases, Santa Clara Valley Medical Center, San Jose, USA
- Department of Medicine, Division of Infectious Diseases and Geographic Medicine, Stanford University, Stanford, California, USA
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Zhou Q, Murphy WJ. Immune response and immunotherapy to Cryptococcus infections. Immunol Res 2007; 35:191-208. [PMID: 17172646 DOI: 10.1385/ir:35:3:191] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/1999] [Revised: 11/30/1999] [Accepted: 11/30/1999] [Indexed: 11/11/2022]
Abstract
Cryptococcus neoformans is a ubiquitous fungus that can cause lifethreatening infections during immunosuppressive states such as acquired immunodeficiency syndrome (AIDS) and after bone marrow transplantation (BMT). Infected individuals normally succumb to meningitis and meningoencephalitis caused by dissemination of C. neoformans to the brain. In this review, we analyze the current understanding of the interaction between host immune response and C. neoformans as well as the current state of immunotherapeutic strategies for treating cryptococcosis.
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Affiliation(s)
- Qing Zhou
- Department of Microbiology and Immunology, University of Nevada, Reno, NV 89557, USA
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29
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Rivera J, Casadevall A. Mouse genetic background is a major determinant of isotype-related differences for antibody-mediated protective efficacy against Cryptococcus neoformans. THE JOURNAL OF IMMUNOLOGY 2005; 174:8017-26. [PMID: 15944309 DOI: 10.4049/jimmunol.174.12.8017] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The protective efficacy of mAbs to Cryptococcus neoformans glucuronoxylomannan depends on Ab isotype. Previous studies in A/JCr and C57BL/6J mice showed relative protective efficacy of IgG1, IgG2a >> IgG3. However, we now report that in C57BL/6J x 129/Sv mice, IgG3 is protective while IgG1 is not protective, with neither isotype being protective in 129/Sv mice. IgG1, IgG2a, and IgG3 had different effects on IFN-gamma expression in infected C57BL/6J x 129/Sv mice. IgG1-treated C57BL/6J x 129/Sv mice had significantly more pulmonary eosinophilia than IgG2a- and IgG3-treated C57BL/6J x 129/Sv mice. C. neoformans infection and Ab administration had different effects on FcgammaRI, FcgammaRII, and FcgammaRIII expression in C57BL/6J, 129/Sv, and C57BL/6J x 129/Sv mice. Our results indicate that the relative efficacy of Ab isotype function against C. neoformans is a function of the genetic background of the host and that IgG3-mediated protection in C57BL/6J x 129/Sv mice was associated with lower levels of IFN-gamma and fewer pulmonary eosinophils. The dependence of isotype efficacy on host genetics underscores a previously unsuspected complex relationship between the cellular and humoral arms of the adaptive immune response.
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MESH Headings
- Animals
- Antibodies, Fungal/administration & dosage
- Antibodies, Fungal/physiology
- Antibodies, Fungal/therapeutic use
- Antibodies, Monoclonal/administration & dosage
- Antibodies, Monoclonal/physiology
- Antibodies, Monoclonal/therapeutic use
- Cell Movement/genetics
- Cell Movement/immunology
- Crosses, Genetic
- Cryptococcosis/genetics
- Cryptococcosis/immunology
- Cryptococcosis/mortality
- Cryptococcosis/pathology
- Cryptococcus neoformans/immunology
- Female
- Genetic Predisposition to Disease
- Immunoglobulin E/blood
- Immunoglobulin G/administration & dosage
- Immunoglobulin G/physiology
- Immunoglobulin G/therapeutic use
- Immunoglobulin Isotypes/administration & dosage
- Immunoglobulin Isotypes/genetics
- Immunoglobulin Isotypes/physiology
- Lung/immunology
- Lung/microbiology
- Lung/pathology
- Mice
- Mice, Inbred A
- Mice, Inbred C57BL
- Receptors, IgG/biosynthesis
- Survival Analysis
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Affiliation(s)
- Johanna Rivera
- Department of Microbiology and Immunology, Division of Infectious Diseases, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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30
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Singh G, Singh B, Trajkovic V, Sharma P. Mycobacterium tuberculosis 6kDa early secreted antigenic target stimulates activation of J774 macrophages. Immunol Lett 2005; 98:180-8. [PMID: 15860216 DOI: 10.1016/j.imlet.2004.11.011] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2004] [Revised: 11/10/2004] [Accepted: 11/12/2004] [Indexed: 10/26/2022]
Abstract
The influence of the 6 kDa early-secreted antigenic target (ESAT-6) of Mycobacterium tuberculosis on macrophage activation was investigated using J774 macrophage cell line. While without effect if applied alone, ESAT-6 in a dose-dependent manner enhanced nitric oxide (NO) release by IFN-gamma-stimulated J774 cells. However, it completely failed to modulate NO production in J774 cells activated with E. coli lipopolysaccharide. The effect of ESAT-6 on NO synthesis in IFN-gamma-activated J774 cells was accompanied by up-regulated expression of inducible NO synthase (iNOS), an enzyme that catalyzes NO formation. ESAT-6-mediated enhancement of macrophage NO release was markedly suppressed by pharmacological agents that selectively inhibit iNOS enzymatic activity or protein tyrosine kinase and mitogen-activated protein kinase activation. Finally, treatment of J774 macrophages with ESAT-6 also enhanced IFN-gamma-induced expression of the surface molecules B7.1, MHC-II, and ICAM-1. Collectively, these data suggest that ESAT-6 might contribute to macrophage activation in tuberculosis.
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Affiliation(s)
- Gyanesh Singh
- Immunology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India
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31
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Chen GH, McDonald RA, Wells JC, Huffnagle GB, Lukacs NW, Toews GB. The gamma interferon receptor is required for the protective pulmonary inflammatory response to Cryptococcus neoformans. Infect Immun 2005; 73:1788-96. [PMID: 15731080 PMCID: PMC1064966 DOI: 10.1128/iai.73.3.1788-1796.2005] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2004] [Revised: 10/12/2004] [Accepted: 10/30/2004] [Indexed: 11/20/2022] Open
Abstract
Mice with a null deletion mutation in the gamma interferon (IFN-gamma) receptor gene were used to study the role of IFN-gamma responsiveness during experimental pulmonary cryptococcosis. Cryptococcus neoformans was inoculated intratracheally into mice lacking the IFN-gamma receptor gene (IFN-gammaR-/-) and into control mice (IFN-gammaR+/+). The numbers of CFU in lung, spleen, and brain were determined to assess clearance; cytokines produced by lung leukocytes were measured, and survival curves were generated. In the present study, we demonstrate the following points. (i) IFN-gammaR-/- mice are markedly more susceptible to C. neoformans infection than IFN-gammaR+/+ mice. (ii) In the absence of IFN-gamma signaling, pulmonary CFU continue to increase over the course of infection, and the infection disseminates to the brain. (iii) In the absence of IFN-gamma receptor, recruitment of inflammatory cells in response to pulmonary cryptococcal infection is not impaired. (iv) At week 5 postinfection, IFN-gammaR-/- mice have recruited greater numbers of leukocytes into their lungs, with neutrophils, eosinophils, and lymphocytes accounting for this cellular increase. (v) IFN-gamma signaling is required for the development of a T1 over a T2 immune response in the lung following cryptococcal infection. These results indicate that in the absence of IFN- gamma responsiveness, even though the recruitment of pulmonary inflammatory cells is not impaired and the secretion of IFN-gamma is not affected, IFN-gammaR-/- mice do not have the ability to resolve the cryptococcal infection. In conclusion, our data suggest that proper functional IFN-gamma signaling, possibly through a mechanism which inhibits the potentially disease-promoting T2 response, is required for mice to confine the cryptococcal infection.
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Affiliation(s)
- Gwo-Hsiao Chen
- Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, 6301 MSRB III-Box 0642, University of Michigan Medical School, 1150 W. Medical Ctr. Dr., Ann Arbor, MI 48109-0642, USA.
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32
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Vecchiarelli A, Pietrella D, Bistoni F, Kozel TR, Casadevall A. Antibody to Cryptococcus neoformans capsular glucuronoxylomannan promotes expression of interleukin-12Rbeta2 subunit on human T cells in vitro through effects mediated by antigen-presenting cells. Immunology 2002; 106:267-72. [PMID: 12047756 PMCID: PMC1782713 DOI: 10.1046/j.1365-2567.2002.01419.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The results reported herein show that T cells responding to encapsulated Cryptococcus neoformans cells had reduced expression of interleukin-12 receptor beta2 (IL-12Rbeta2) in comparison to those responding to non-encapsulated cells. This suggested that encapsulation with glucuronoxylomannan (GXM), the principal constituent of the C. neoformans polysaccharide antiphagocytic capsule, inhibited expression of the IL-12Rbeta2 subunit on T cells responding to cryptococcal antigens. Addition of GXM-binding monoclonal antibody (mAb) overcame this effect by promoting IL-12Rbeta2 expression and by decreasing IL-1R expression on T cells. This effect may be a consequence of mAb-induced changes on antigen-presenting cells (APC) that are closely related to increased phagocytosis. Blocking of phagocytosis with monoiodacetic acid (MIA) precluded up-regulation of B7 expression on APC and was associated with diminished IL-12Rbeta2 expression on T cells. The observed effects on T cells were interpreted as a consequence of increased APC function due to enhanced phagocytosis. These findings suggest a mechanism by which specific antibody can promote the polarization of the cellular immune response towards a Th1-like response and thus contribute to an enhanced cellular immune response against C. neoformans.
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Affiliation(s)
- Anna Vecchiarelli
- Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, Perugia, Italy.
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33
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Nichols KL, Bauman SK, Schafer FB, Murphy JW. Differences in components at delayed-type hypersensitivity reaction sites in mice immunized with either a protective or a nonprotective immunogen of Cryptococcus neoformans. Infect Immun 2002; 70:591-600. [PMID: 11796587 PMCID: PMC127722 DOI: 10.1128/iai.70.2.591-600.2002] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2001] [Revised: 10/11/2001] [Accepted: 10/30/2001] [Indexed: 11/20/2022] Open
Abstract
Cell-mediated immunity is the major protective mechanism against Cryptococcus neoformans. Delayed swelling reactions, i.e., delayed-type hypersensitivity (DTH), in response to an intradermal injection of specific antigen are used as a means of detecting a cell-mediated immune (CMI) response to the antigen. We have found previously that the presence of an anticryptococcal DTH response in mice is not always indicative of protection against a cryptococcal infection. Using one immunogen that induces a protective anticryptococcal CMI response and one that induces a nonprotective response, we have shown that mice immunized with the protective immunogen undergo a classical DTH response characterized by mononuclear cell and neutrophil infiltrates and the presence of gamma interferon and NO. In contrast, immunization with the nonprotective immunogen results in an influx of primarily neutrophils and production of tumor necrosis factor alpha (TNF-alpha) at the DTH reaction site. Even when the anticryptococcal DTH response was augmented by blocking the down-regulator, CTLA-4 (CD152), on T cells in the mice given the nonprotective immunogen, the main leukocyte population infiltrating the DTH reaction site is the neutrophil. Although TNF-alpha is increased at the DTH reaction site in mice immunized with the nonprotective immunogen, it is unlikely that TNF-alpha activates the neutrophils, because the density of TNF receptors on the neutrophils is reduced below control levels. Uncoupling of DTH reactivity and protection has been demonstrated in other infectious-disease models; however, the mechanisms differ from our model. These findings stress the importance of defining the cascade of events occurring in response to various immunogens and establishing the relationships between protection and DTH reactions.
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MESH Headings
- Animals
- Antigens, CD/metabolism
- Antigens, Fungal/immunology
- Cryptococcosis/prevention & control
- Cryptococcus neoformans/immunology
- Female
- Granulocytes/metabolism
- Hypersensitivity, Delayed/immunology
- Interferon-gamma/genetics
- Mice
- Mice, Inbred CBA
- Nitric Oxide/metabolism
- RNA, Messenger/metabolism
- Receptors, Tumor Necrosis Factor/metabolism
- Receptors, Tumor Necrosis Factor, Type I
- Receptors, Tumor Necrosis Factor, Type II
- Tumor Necrosis Factor-alpha/genetics
- Vaccination
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Affiliation(s)
- Kasie L Nichols
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA
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34
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Retini C, Kozel TR, Pietrella D, Monari C, Bistoni F, Vecchiarelli A. Interdependency of interleukin-10 and interleukin-12 in regulation of T-cell differentiation and effector function of monocytes in response to stimulation with Cryptococcus neoformans. Infect Immun 2001; 69:6064-73. [PMID: 11553544 PMCID: PMC98735 DOI: 10.1128/iai.69.10.6064-6073.2001] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously demonstrated that the principal component of capsular material of Cryptococcus neoformans, glucuronoxylomannan (GXM), induces interleukin-10 (IL-10) secretion from human monocytes. Here we report that encapsulation of the yeast with GXM is able to down-regulate interleukin-12 (IL-12) production by monocytes that would normally occur in the absence of encapsulation. This phenomenon appeared to be the result of inhibition of the phagocytic process by encapsulation with GXM as well as of negative signals such as IL-10 secretion produced by interaction of GXM with leukocytes. Decreased secretion of IL-12 correlated with decreased release of gamma interferon (IFN-gamma) from T cells, suggesting a role for encapsulation with GXM in hindering a T helper type 1 (Th1) response. This is supported by the ability of encapsulation with GXM to limit increased expression of B7-1 costimulatory molecules that otherwise might limit IL-10 secretion. Endogenous IL-10 played a critical role in modulatory activity associated with encapsulation with GXM. Blocking IL-10 with monoclonal antibody to IL-10 resulted in increased (i) IL-12 secretion, (ii) IFN-gamma release from T cells, and (iii) killing of C. neoformans by monocytes. These results suggest that encapsulation with GXM limits development of a protective Th1-type response, an inhibitory process in which IL-10 plays a critical role. Scavengers of GXM and/or IL-10 could be useful in a protective Th1-type response in patients with cryptococcosis.
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Affiliation(s)
- C Retini
- Microbiology Section, Department of Experimental Medicine and Biochemical Sciences, University of Perugia, 06122 Perugia, Italy
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35
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Beenhouwer DO, Shapiro S, Feldmesser M, Casadevall A, Scharff MD. Both Th1 and Th2 cytokines affect the ability of monoclonal antibodies to protect mice against Cryptococcus neoformans. Infect Immun 2001; 69:6445-55. [PMID: 11553589 PMCID: PMC98780 DOI: 10.1128/iai.69.10.6445-6455.2001] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Variable-region-identical mouse immunoglobulin G1 (IgG1), IgG2b, and IgG2a monoclonal antibodies to the capsular polysaccharide of Cryptococcus neoformans prolong the lives of mice infected with this fungus, while IgG3 is either not protective or enhances infection. CD4+ T cells are required for IgG1-mediated protection, and CD8+ T cells are required for IgG3-mediated enhancement. Gamma interferon is required for both effects. These findings revealed that T cells and cytokines play a role in the modulation of cryptococcal infection by antibodies and suggested that it was important to more fully define the cytokine requirements of each of the antibody isotypes. We therefore investigated the efficacy of passively administered variable-region-identical IgG1, IgG2a, IgG2b, and IgG3 monoclonal antibodies against intravenous infection with C. neoformans in mice genetically deficient in interleukin-12 (IL-12), IL-6, IL-4, or IL-10, as well as in the parental C57BL/6J strain. The relative inherent susceptibilities of these mouse strains to C. neoformans were as follows: IL-12(-/-) > IL-6(-/-) > C57BL/6J approximately IL-4(-/-) >> IL-10(-/-). This is consistent with the notion that a Th1 response is necessary for natural immunity against cryptococcal infection. However, none of the IgG isotypes prolonged survival in IL-12(-/-), IL-6(-/-), or IL-4(-/-) mice, and all isotypes significantly enhanced infection in IL-10(-/-) mice. These results indicate that passive antibody-mediated protection against C. neoformans requires both Th1- and Th2-associated cytokines and reveal the complexity of the mechanisms through which antibodies modulate infection with this organism.
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MESH Headings
- Animals
- Antibodies, Fungal/administration & dosage
- Antibodies, Fungal/immunology
- Antibodies, Monoclonal/administration & dosage
- Antibodies, Monoclonal/immunology
- Antigens, Fungal/immunology
- Cells, Cultured
- Cryptococcosis/immunology
- Cryptococcosis/mortality
- Cryptococcosis/pathology
- Cryptococcosis/prevention & control
- Cryptococcus neoformans/growth & development
- Cryptococcus neoformans/immunology
- Disease Models, Animal
- Disease Susceptibility/immunology
- Female
- Immunization, Passive/methods
- Immunoglobulin G/immunology
- Immunoglobulin Isotypes/immunology
- Interleukin-10/genetics
- Interleukin-10/immunology
- Interleukin-12/genetics
- Interleukin-12/immunology
- Interleukin-4/genetics
- Interleukin-4/immunology
- Interleukin-6/genetics
- Interleukin-6/immunology
- Macrophages, Peritoneal/cytology
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/microbiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Phagocytosis/immunology
- Polysaccharides/immunology
- Th1 Cells/immunology
- Th2 Cells/immunology
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Affiliation(s)
- D O Beenhouwer
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, New York 10461, USA
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36
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Abe K, Kadota J, Ishimatsu Y, Iwashita T, Tomono K, Kawakami K, Kohno S. Th1-Th2 cytokine kinetics in the bronchoalveolar lavage fluid of mice infected with Cryptococcus neoformans of different virulences. Microbiol Immunol 2001; 44:849-55. [PMID: 11128069 DOI: 10.1111/j.1348-0421.2000.tb02573.x] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Th1 immune response plays an important role in protection against infection with Cryptococcus neoformans in mice. We investigated the effect of virulence of C. neoformans on cytokine production in the lung of a mouse model of pulmonary cryptococcosis. BALB/c mice were inoculated intratracheally with a high or low virulence strain of C. neoformans, followed by serial measurements of Th1 and Th2 cytokine concentrations in the bronchoalveolar lavage (BAL) fluid using appropriate enzyme-linked immunosorbent assay kits. The number of colony-forming units (CFU) increased with time, and all mice infected with the highly virulent strain were dead at 28 days after inoculation. In contrast, the number of microorganisms diminished with time in the mice infected with the low virulence strain during the 4-week study. The numbers of neutrophils and lymphocytes in the BAL fluid paralleled those of CFU. High neutrophil counts were observed in the BAL fluid of mice infected with the highly virulent strain, while lymphocyte counts were increased only in the later part of the study in mice infected with the high and low virulence strains. The concentrations of Th2 cytokine, interleukin (IL)-4 were significantly higher in mice infected with the highly virulent strain at days 14 and 21 of infection, whereas the level of Th1 cytokine, interferon-gamma, was significantly higher in the latter strain at days 7 and 14. Our results suggest that strain-specific difference in the organism's ability to induce (or evade) the host immune system contributes to the outcome of infection.
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Affiliation(s)
- K Abe
- Second Department of lnternal Medicine, Nagasaki University School of Medicine, Japan
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37
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Bauman SK, Nichols KL, Murphy JW. Dendritic cells in the induction of protective and nonprotective anticryptococcal cell-mediated immune responses. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2000; 165:158-67. [PMID: 10861048 DOI: 10.4049/jimmunol.165.1.158] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Dendritic cells (DC) can be divided into three subsets, Langerhans cells, myeloid DC (MDC), and lymphoid DC (LDC), based upon phenotypic and functional differences. We hypothesized that different DC subsets are associated with the development of protective vs nonprotective cell-mediated immune (CMI) responses against the fungal pathogen, Cryptococcus neoformans. To test this, mice were immunized with protective and/or nonprotective immunogens, and DC subsets in draining lymph nodes were assessed by flow cytometry. The protective immunogen (cryptococcal culture filtrate Ag-CFA), in contrast to the nonprotective immunogen (heat-killed cryptococci-CFA), the nonprotective immunogen mixed with the protective immunogen (cryptococcal culture filtrate Ag + heat-killed cryptococci-CFA), or controls, stimulated significant increases in total leukocytes, Langerhans cells, MDC, LDC, and activated CD4+ T cells in draining lymph nodes. The protective immune response resulted in significantly increased levels of anticryptococcal delayed-type hypersensitivity reactivity and activated CD4+ T cells at the delayed-type hypersensitivity reaction site. Draining lymph node LDC:MDC ratios induced by the protective immunogen were significantly lower than the ratios induced by either immunization in which the nonprotective immunogen was present. In contrast, mice given the nonprotective immunogen had LDC:MDC ratios similar to those of naive mice. Our data indicate that lymph node Langerhans cells and MDC are APC needed for induction of the protective response. The predominance of LDC in mice undergoing nonprotective responses suggests that lymph node LDC, like splenic LDC, are negative regulators of CMI responses. In addition to showing DC subsets associated with functional differences, our data suggest that the LDC:MDC balance, which can be modulated by the Ag, determines whether protective or nonprotective anticryptococcal CMI responses develop.
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MESH Headings
- Animals
- Antigens, CD
- Antigens, Fungal/administration & dosage
- Antigens, Fungal/immunology
- Apoptosis/immunology
- B7-1 Antigen/biosynthesis
- CD4 Lymphocyte Count
- CD4-Positive T-Lymphocytes/immunology
- CD40 Antigens/biosynthesis
- Cell Movement/immunology
- Cryptococcosis/immunology
- Cryptococcosis/mortality
- Cryptococcosis/prevention & control
- Cryptococcus neoformans/immunology
- Culture Media
- Dendritic Cells/cytology
- Dendritic Cells/immunology
- Dendritic Cells/metabolism
- Female
- Flow Cytometry
- Freund's Adjuvant/administration & dosage
- Freund's Adjuvant/immunology
- Fungal Vaccines/administration & dosage
- Fungal Vaccines/immunology
- Hematopoietic Stem Cells/immunology
- Hematopoietic Stem Cells/metabolism
- Histocompatibility Antigens Class II/biosynthesis
- Hypersensitivity, Delayed/immunology
- Hypersensitivity, Delayed/prevention & control
- Immunity, Cellular
- Immunophenotyping
- Kinetics
- Langerhans Cells/cytology
- Langerhans Cells/immunology
- Langerhans Cells/metabolism
- Lectins, C-Type
- Leukocyte Count
- Leukocytes/immunology
- Lymph Nodes/cytology
- Lymph Nodes/immunology
- Lymph Nodes/metabolism
- Lymphocyte Activation/immunology
- Lymphocyte Subsets/cytology
- Lymphocyte Subsets/immunology
- Lymphocyte Subsets/metabolism
- Membrane Glycoproteins/analysis
- Mice
- Mice, Inbred CBA
- Minor Histocompatibility Antigens
- Receptors, Cell Surface/analysis
- Survival Analysis
- T-Lymphocytes/immunology
- Vaccines, Inactivated/administration & dosage
- Vaccines, Inactivated/immunology
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Affiliation(s)
- S K Bauman
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City 73190, USA
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38
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Buchanan KL, Doyle HA. Requirement for CD4(+) T lymphocytes in host resistance against Cryptococcus neoformans in the central nervous system of immunized mice. Infect Immun 2000; 68:456-62. [PMID: 10639404 PMCID: PMC97163 DOI: 10.1128/iai.68.2.456-462.2000] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/1999] [Accepted: 10/26/1999] [Indexed: 11/20/2022] Open
Abstract
The importance of cell-mediated immunity (CMI) and CD4(+) T lymphocytes in host resistance against Cryptococcus neoformans is well documented and is exemplified by the high susceptibility to progressive infection with this pathogen of AIDS patients with reduced CD4(+) T-cell numbers. Although much has been learned about the role of CMI in the clearance of C. neoformans from the lungs and other internal organs, less is known about the protective mechanisms in the brain, the organ most frequently involved with a fatal outcome of cryptococcosis. We hypothesized that host resistance mechanisms against C. neoformans in the central nervous system (CNS) were similar to those outside the CNS (i.e., gamma interferon [IFN-gamma], CD4(+) T cells, and others). To test this hypothesis, we used a murine model of cryptococcal meningitis whereby cryptococci are introduced directly into the CNS. In experiments where mice were immunized to mount an anticryptococcal CMI response, our results indicate that immunization induced protective mechanisms that could be detected in the CNS by inhibition of the growth of viable yeast cells. Flow cytometric analyses of leukocytes in brain and spinal cord homogenates revealed that T lymphocytes, macrophages, and neutrophils accumulated in C. neoformans-infected brains of immune mice. In vivo depletion of CD4(+) T cells, but not CD8(+) T cells, resulted in significantly reduced leukocyte accumulation in the brains of immune mice. Furthermore, depletion of CD4(+) T cells or neutralization of IFN-gamma exacerbated CNS infection in immune mice, suggesting a critical role for CMI mechanisms in acquired protection in the CNS.
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Affiliation(s)
- K L Buchanan
- Department of Microbiology and Immunology, Tulane University Medical Center, New Orleans, Louisiana 70112, USA.
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39
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Blackstock R, Buchanan KL, Adesina AM, Murphy JW. Differential regulation of immune responses by highly and weakly virulent Cryptococcus neoformans isolates. Infect Immun 1999; 67:3601-9. [PMID: 10377145 PMCID: PMC116550 DOI: 10.1128/iai.67.7.3601-3609.1999] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Early inflammatory responses, delayed-type hypersensitivity (DTH) responses, and cytokine profiles were studied in mice infected by the pulmonary route with either a highly virulent isolate (NU-2) or a weakly virulent isolate (184A) of Cryptococcus neoformans. After infection, NU-2 remained in the lungs and the capsule became more pronounced during the first 24 h, whereas 184A induced an immediate inflammatory reaction and was rapidly cleared from the lungs. Cryptococcal antigen (GXM) appeared in sera early after infection with NU-2 and increased over the entire observation period. There was no detectable GXM in sera from 184A-infected mice. Both C. neoformans isolates induced anticryptococcal cell-mediated immune responses, but the responses had different profiles. DTH in NU-2-infected mice appeared at day 15 after infection and waned by day 21, whereas DTH in 184A-infected mice was present by day 5 and continued to increase. T helper 1 (Th1) cytokines (interleukin 2 [IL-2] and gamma interferon) were made by spleen cells early after infection with either isolate. NU-2-infected mice lost their ability to produce these cytokines, but 184A-infected mice retained it. IL-4, a Th2 cytokine, was not detected in infected mice. The regulatory cytokine IL-10 was made by spleen cells early but not later after infection with the highly virulent isolate and was not produced by spleen cells from 184A-infected mice. IL-10-deficient mice survived an NU-2 infection significantly longer than wild-type mice, suggesting that IL-10 is important in down-regulating the protective immune response. The induction of anergy appears to be responsible for the inability of NU-2-infected mice to control a C. neoformans infection.
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Affiliation(s)
- R Blackstock
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA.
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40
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Murphy JW, Schafer F, Casadevall A, Adesina A. Antigen-induced protective and nonprotective cell-mediated immune components against Cryptococcus neoformans. Infect Immun 1998; 66:2632-9. [PMID: 9596727 PMCID: PMC108249 DOI: 10.1128/iai.66.6.2632-2639.1998] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/1997] [Accepted: 03/16/1998] [Indexed: 02/07/2023] Open
Abstract
Mice immunized with two different cryptococcal antigen preparations, one a soluble culture filtrate antigen (CneF) in complete Freund's adjuvant (CFA) and the other heat-killed Cryptococcus neoformans cells (HKC), develop two different profiles of activated T cells. CneF-CFA induces CD4+ T cells responsible for delayed-type hypersensitivity (DTH) reactivity and for amplification of the anticryptococcal DTH response, whereas HKC induce CD4+ and CD8+ T cells involved in anticryptococcal DTH reactivity and activated T cells which directly kill C. neoformans cells. The main purpose of this study was to assess the level of protection afforded by each of the two different T-cell profiles against challenge with viable C. neoformans cells, thereby identifying which activated T-cell profile provides better protection. CBA/J mice immunized with CneF-CFA had significantly better protective responses, based on better clearance of C. neoformans from tissues, on longer survival times, and on fewer and smaller lesions in the brain, than HKC-immunized mice or control mice similarly infected with C. neoformans. Both immunization protocols induced an anticryptococcal DTH response, but neither induced serum antibodies to glucuronoxylmannan, so the protection observed in the CneF-CFA immunized mice was due to the activated T-cell profile induced by that protocol. HKC-immunized mice, which displayed no greater protection than controls, did not have the amplifier cells. Based on our findings, we propose that the protective anticryptococcal T cells are the CD4+ T cells which have been shown to be responsible for DTH reactivity and/or the CD4+ T cells which amplify the DTH response and which have been previously shown to produce high levels of gamma interferon and interleukin 2. Our results imply that there are protective and nonprotective cell-mediated immune responses and highlight the complexity of the immune response to C. neoformans antigens.
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Affiliation(s)
- J W Murphy
- Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73190, USA.
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41
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Murphy JW. Protective cell-mediated immunity against Cryptococcus neoformans. RESEARCH IN IMMUNOLOGY 1998; 149:373-86; discussion 519-22. [PMID: 9720955 DOI: 10.1016/s0923-2494(98)80761-x] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Affiliation(s)
- J W Murphy
- University of Oklahoma Health Sciences Center, Department of Microbiology and Immunology, Oklahoma City 73019, USA
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Wright TW, Johnston CJ, Harmsen AG, Finkelstein JN. Analysis of cytokine mRNA profiles in the lungs of Pneumocystis carinii-infected mice. Am J Respir Cell Mol Biol 1997; 17:491-500. [PMID: 9376124 DOI: 10.1165/ajrcmb.17.4.2851] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Severe combined immunodeficient (scid) mice lack functional CD4+ lymphocytes, and therefore develop life-threatening Pneumocystis carinii infection. However, when scid mice are immunologically reconstituted with spleen cells, including CD4+ cells, a protective inflammatory response is mounted against the organism. To determine whether these lymphocytes induce elevated cytokine mRNA levels in response to P. carinii infection, steady-state levels of cytokine mRNAs were measured in the lungs of both reconstituted and unaltered scid mice. Despite significant numbers of organisms and the presence of functional alveolar macrophages in the lungs of 8- and 10-wk-old scid mice, there was neither evidence of pulmonary inflammation, nor increased proinflammatory cytokine expression. However, when 8-wk-old scid mice were immunologically reconstituted, signs of intense, focal pulmonary inflammation were observed, and levels of interleukin (IL)-1alpha, IL-1beta, IL-3, IL-6, interferon-gamma (IFN-gamma), tumor necrosis factor (TNF)-alpha, and TNF-beta mRNAs were all significantly elevated. Cytokine expression was increased at day 10 post-reconstitution (PR), maximal at day 12 PR, and returned to baseline by day 22 PR. In situ hybridization demonstrated that at day 12 PR, increased IL-1beta and TNF-alpha expression was localized to sites of intense inflammation and focal P. carinii colonization. Many of the cells expressing high levels of IL-1beta and TNF-alpha in these regions were in direct contact with organisms, or contained degraded organisms within their cytoplasm. Thus, even though functional macrophages are present in scid mice, CD4+ T cells are required for proinflammatory cytokine expression, which is associated with the generation of a protective inflammatory response at sites of P. carinii infection.
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Affiliation(s)
- T W Wright
- Department of Pediatrics, University of Rochester School of Medicine and Dentistry, New York 14642, USA.
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Yuan RR, Casadevall A, Oh J, Scharff MD. T cells cooperate with passive antibody to modify Cryptococcus neoformans infection in mice. Proc Natl Acad Sci U S A 1997; 94:2483-8. [PMID: 9122221 PMCID: PMC20114 DOI: 10.1073/pnas.94.6.2483] [Citation(s) in RCA: 127] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/01/1997] [Indexed: 02/04/2023] Open
Abstract
Cryptococcus neoformans is an encapsulated fungus that is a major cause of meningitis in patients with AIDS. In immunocompetent mice, administration of IgG1 mAb protects against cryptococcal infection, whereas administration of IgG3 is not protective and can accelerate the infection. In beige mice with impaired natural killer cell function, the effects of IgG1 and IgG3 are similar to those observed in immunocompetent mice, suggesting that natural killer cells are not crucial for antibody-mediated modulation of cryptococcal infection. In mice lacking CD4+ T cells, IgG1 is not protective and IgG3 accelerates infection, indicating that CD4+ T cells are required for antibody-mediated protection. In mice lacking CD8+ T cells, both IgG1 and IgG3 antibodies prolong survival, indicating that acceleration of the disease process by IgG3 involves CD8+ T cells. Both IgG1-mediated protection and IgG3-mediated acceleration of infection require interferon gamma. These results reveal a functional dependence of passively administered antibody on cellular immunity in cryptococcal infection in mice and have implications for antibody-based therapies in humans in the setting of CD4+ lymphopenia.
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Affiliation(s)
- R R Yuan
- Department of Cell Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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Kudeken N, Kawakami K, Kusano N, Saito A. Cell-mediated immunity in host resistance against infection caused by Penicillium marneffei. JOURNAL OF MEDICAL AND VETERINARY MYCOLOGY : BI-MONTHLY PUBLICATION OF THE INTERNATIONAL SOCIETY FOR HUMAN AND ANIMAL MYCOLOGY 1996; 34:371-8. [PMID: 8971625 DOI: 10.1080/02681219680000671] [Citation(s) in RCA: 50] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Penicillium marneffei is one of the most important opportunistic infectious pathogens in AIDS patients in Thailand and Southeast Asia. However, very little is known about the host defence mechanisms against P. marneffei infection. In the present study, we established the first experimental murine model of chronic pulmonary and disseminated infection using P. marneffei, and examined the immunological response to such infection in euthymic and athymic mice. In this model, micro-organisms inoculated intratracheally multiplied progressively in the lungs and disseminated to the liver and spleen. However, the number of organisms decreased gradually in these organs. In contrast, congenitally athymic mice developed severe pulmonary and disseminated systemic mycosis. Pulmonary penicilliosis marneffei was associated with a marked cellular inflammatory response as evident by histological abnormalities and increased intraparenchymal leucocyte count. To confirm the importance of cell-mediated immunity in host resistance to P. marneffei infection, we transferred nylon wool non-adherent spleen cells into the athymic mice. Such treatment significantly reduced the number of yeasts in the organs of athymic mice. Taken together, our results demonstrate that the cell-mediated immunity play a central role in a host defence mechanism against infection with P. marneffei, and suggest that our new model may be a useful approach for studying the pathogenesis of this fungal disease.
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Affiliation(s)
- N Kudeken
- First Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan
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Tohyama M, Kawakami K, Futenma M, Saito A. Enhancing effect of oxygen radical scavengers on murine macrophage anticryptococcal activity through production of nitric oxide. Clin Exp Immunol 1996; 103:436-41. [PMID: 8608643 PMCID: PMC2200379 DOI: 10.1111/j.1365-2249.1996.tb08299.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We examined the roles of reactive nitrogen intermediates (RNI) and reactive oxygen intermediates (ROI) in interferon-gamma (IFN-gamma)-induced cryptococcostatic activity of murine peritoneal macrophages using N(G)-monomethyl-L-arginine (L-NMMA), a competitive inhibitor of RNI synthesis, and superoxide dismutase (SOD) and catalase, oxygen radical scavengers. IFN-gamma-activated macrophages produced nitric oxide (NO) in a dose-dependent manner, as measured by increased nitrite concentration in the culture supernatant. IFN-gamma also enhanced the suppressive effect on cryptococcal growth in a similar dose-dependent manner. The induction of killing activity and NO production by an optimal dose of IFN-gamma (100 U/ml) was virtually suppressed by 500 microM L-NMMA. These results confirmed the importance of the RNI-mediated effector mechanism in anticryptococcal activity of macrophages. SOD and catalase significantly enhanced the cryptococcostatic activity of macrophages induced by a suboptimal dose of IFN-gamma (20 U/ml). The augmenting effect of these reagents was mediated by NO, since they potentiated the production of NO by macrophages and their effects were totally blocked by L-NMMA. Our results indicate that the IFN-gamma-induced anticryptococcal activity of macrophages is dependent mostly on RNI, and suggest that the ROI system down-regulates the effector mechanism for cryptococcostasis by suppressing the RNI system.
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Affiliation(s)
- M Tohyama
- First Department of Internal Medicine, Faculty of Medicine, University of the Ryukyus, Okinawa, Japan
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