Use of a genetically engineered strain to evaluate the pathogenic potential of yeast cell and filamentous forms during Candida albicans systemic infection in immunodeficient mice.

The pathogenesis of Candida albicans systemic infection is complex and results from the balance between its intrinsic virulence attributes and the host immune responses. Morphogenetic transitions between yeast cell and filamentous forms are considered one of the main virulence attributes in C. albicans. We have examined the pathogenesis of a genetically engineered C. albicans strain in which morphogenetic conversions can be externally manipulated in immunodeficient mice; these included B-cell deficient, nude (T cell deficient), SCID (lacking both functional T and B cells), and DBA/2N (C5 deficient with impaired neutrophil activity) mice. We also tested mice severely immunosuppressed by cyclophosphamide-cortisone acetate treatment. Mice with specific immune defects were able to survive an infection by yeast cells but not filamentous forms. However, yeast cells displayed a pathogenic effect leading to lethality in the severely immunosuppressed mice.