• Login as Editor
    View Item 
    •   Yeshiva Academic Institutional Repository
    • Albert Einstein College of Medicine (AECOM)
    • Albert Einstein College of Medicine: Doctoral Dissertations
    • View Item
    •   Yeshiva Academic Institutional Repository
    • Albert Einstein College of Medicine (AECOM)
    • Albert Einstein College of Medicine: Doctoral Dissertations
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    The evolution of fungal virulence

    Thumbnail
    Date
    2003
    Author
    Steenbergen, Judith Nadine
    Metadata
    Show full item record
    Abstract
    Maintenance of fungal virulence in soil is enigmatic since mammalian infection is not necessary for the fungal life cycle. We sought to determine if soil amoebae may be involved in maintaining fungal virulence in the environment. Using both Acanthamoebae castellanii and Dictyostelium discoideum we demonstrated that soil amoebae can be infected by fungal pathogens. Cryptococcus neoformans, a saprophytic soil fungus, is phagocytosed by A. castellanii which results in killing of the amoebae and replication of C. neoformans. C. neoformans cells with attenuated virulence because of defects in capsule synthesis, melanin production, or phospholipase secretion were also avirulent to amoebae. Using both immunogold electron microscopy and immunofluorescence we demonstrated that C. neoformans cells secrete capsular polysaccharide into discrete vesicles. We also investigated the interaction of amoebae and the dimorphic fungi Histoplasma capsulatum, Blastomyces dermatitidis, and Sporothrix schenkii. Infection of amoebae with H. capsulatum, B. dermatitidis and S. schenckii yeast forms resulted in fungal growth and amoebae killing. The environmental conidial forms of H. capsulatum were determined to be infectious to amoebae. Passage of an avirulent strain of H. capsulatum with A. castellanii resulted in the recovery of virulence as determined by CFU and histopathology. Since there are a wide variety of soil amoebae, we investigated whether D. discoideum could also support C. neoformans growth. Phagocytosis of C. neoformans results in amoebae killing and fungal growth. Mice were infected with cryptococcal cells that had been passaged with D. discoideum and mouse survival time was drastically decreased, indicating a significant increase in cryptococcal virulence after amoebae passage. Time to melanization and capsule size was affected by amoebae passage while cryptococcal growth curves were unchanged. The relevance of our studies was evaluated by isolating both amoebae and C. neoformans from the same ecological niche in the Bronx. Combined these results indicate that amoebae are a host for pathogenic fungal studies and we propose that virulence of fungi is maintained in the environment through selection by amoebae and other soil predators.
    Permanent Link(s)
    https://yulib002.mc.yu.edu/login?url=http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqm&rft_dat=xri:pqdiss:3090281
    https://hdl.handle.net/20.500.12202/636
    Collections
    • Albert Einstein College of Medicine: Doctoral Dissertations [1674]

    Yeshiva University Libraries copyright © 2021  DuraSpace
    YAIR Self-Deposit | YAIR User's Guide | Take Down Policy | Contact Us
    Yeshiva University
     

     

    Browse

    AllCommunities & CollectionsBy Issue DateAuthorsTitlesSubjectsThis CollectionBy Issue DateAuthorsTitlesSubjects

    My Account

    Login as Editor

    Statistics

    View Usage Statistics

    Yeshiva University Libraries copyright © 2021  DuraSpace
    YAIR Self-Deposit | YAIR User's Guide | Take Down Policy | Contact Us
    Yeshiva University