Affiliation:
1. Departments of Microbiology and Immunology
2. Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
Abstract
ABSTRACT
Cryptococcus neoformans
is an encapsulated, environmental fungus that can cause life-threatening meningitis. Pathogenicity of
C. neoformans
for macrophages and vertebrate hosts may be a mechanism selected in evolution for protection against environmental predators. In this study, we investigated whether
Dictyostelium discoideum
could serve as an alternate host for
C. neoformans. D. discoideum
has a defined genetic system which provides significant advantages for the study of fungus-amoeba interactions. Our results show that
D. discoideum
is susceptible to infection with
C. neoformans
and that the interactions are similar to those described previously for this fungus with macrophages and
Acanthamoeba castellanii
. Acapsular
C. neoformans
cells did not replicate when coincubated with
D. discoideum
. However, incubation of acapsular
C. neoformans
with
D. discoideum
mutants defective in myosin VII synthesis resulted in infection, validating the concept that avirulent organisms can be virulent in impaired hosts even at the unicellular level. Phagocytosis of
C. neoformans
by
D. discoideum
could be inhibited with capsule-specific antibodies and various sugars. Passage of an encapsulated
C. neoformans
strain through
D. discoideum
cultures increased virulence and was accompanied by larger capsules and faster time to melanization. These results add to the evidence implicating soil ameboid predators as important factors for the maintenance of
C. neoformans
virulence in the environment and suggest that
D. discoideum
promises to be an extremely useful system for studying the interaction of
C. neoformans
with phagocytic cells.
Publisher
American Society for Microbiology
Subject
Infectious Diseases,Immunology,Microbiology,Parasitology
Cited by
137 articles.
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