Cryptococcus neoformans inhibits nitric oxide synthesis caused by CpG-oligodeoxynucleotide-stimulated macrophages in a fashion independent of capsular polysaccharides

Authors

  • Gang Xiao,

    Corresponding author
    1. Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Tohoku University
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  • Akiko Miyazato,

    1. Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine
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  • Ken Inden,

    1. Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine
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  • Kiwamu Nakamura,

    1. Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine
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  • Kohei Shiratori,

    1. Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Tohoku University
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  • Kiyotaka Nakagawa,

    1. Food and Biodynamic Chemistry Laboratory, Graduate School of Agricultural Science, Tohoku University
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  • Teruo Miyazawa,

    1. Food and Biodynamic Chemistry Laboratory, Graduate School of Agricultural Science, Tohoku University
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  • Kazuo Suzuki,

    1. Department of Immunology, Inflammatory Program, Chiba University School of Medicine, Chiba, Japan
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  • Mitsuo Kaku,

    1. Department of Infection Control and Laboratory Diagnostics, Internal Medicine, Tohoku University Graduate School of Medicine
    2. CRESCENDO (Comprehensive Research and Education Center for Planning of Drug Development and Clinical Evaluation) Project, Tohoku University
    3. Infection-Control Research Center, Tohoku University Hospital, Sendai
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  • Kazuyoshi Kawakami

    1. Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Tohoku University
    2. Infection-Control Research Center, Tohoku University Hospital, Sendai
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Correspondence
Kazuyoshi Kawakami, Microbiology and Immunology, Department of Medical Technology, School of Health Sciences, Faculty of Medicine, Tohoku University, 2-1 Seiryo, Aoba, Sendai, Miyagi 980-8575, Japan. Tel: +81 22 717 7946; fax: +81 22 717 7910; email: kawakami@mail.tains.tohoku.ac.jp

*Present address: Department of Laboratory Medicine, 6th Affiliated Hospital, Sun Yat-Sen University, Guangzhou, China.

ABSTRACT

Cryptococcus neoformans is eradicated by macrophages via production of NO. Unmethylated CpG-ODN protect mice from infection with this fungal pathogen by inducing IFN-γ. The present study was designed to elucidate the effect of C. neoformans on the synthesis of NO by alveolar macrophages. For this purpose, MH-S, an alveolar macrophage cell line, was stimulated with CpG-ODN in the presence of IFN-γ. A highly virulent strain of C. neoformans with thick capsule suppressed the production of NO. Capsular polysaccharides were not essential for this suppression, because there was no difference between acapsular mutant (Cap67) and its parent strain. Physical or close interaction of Cap67 with MH-S was necessary, as shown by the loss of such effect when direct contact was interfered by nitrocellulose membrane. Similar effects were observed by disrupted as well as intact Cap67. Whereas the inhibitory effect of intact Cap67 was completely abrogated by heat treatment, disrupted Cap67 did not receive such influence. Finally, disrupted Cap67 did not show any inhibitory effect on the TLR9-mediated activation of NF-κB in a luciferase reporter assay with HEK293T cells, although the TLR4-mediated activation was suppressed. These results revealed that C. neoformans suppressed the synthesis of NO by CpG-ODN and IFN-γ-stimulated macrophages in a fashion independent of capsular polysaccharides, although the precise mechanism remains to be elucidated.

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