<i>Galleria mellonella</i> as a Model System To Study <i>Cryptococcus neoformans</i> Pathogenesis

<jats:title>ABSTRACT</jats:title> <jats:p> Evaluation of <jats:italic>Cryptococcus neoformans</jats:italic> virulence in a number of nonmammalian hosts suggests that <jats:italic>C. neoformans</jats:italic> is a nonspecific pathogen. We used the killing of <jats:italic>Galleria mellonella</jats:italic> (the greater wax moth) caterpillar by <jats:italic>C. neoformans</jats:italic> to develop an invertebrate host model system that can be used to study cryptococcal virulence, host immune responses to infection, and the effects of antifungal compounds. All varieties of <jats:italic>C. neoformans</jats:italic> killed <jats:italic>G. mellonella</jats:italic> . After injection into the insect hemocoel, <jats:italic>C. neoformans</jats:italic> proliferated and, despite successful phagocytosis by host hemocytes, killed caterpillars both at 37°C and 30°C. The rate and extent of killing depended on the cryptococcal strain and the number of fungal cells injected. The sequenced <jats:italic>C. neoformans</jats:italic> clinical strain H99 was the most virulent of the strains tested and killed caterpillars with inocula as low as 20 CFU/caterpillar. Several <jats:italic>C. neoformans</jats:italic> genes previously shown to be involved in mammalian virulence ( <jats:italic>CAP59</jats:italic> , <jats:italic>GPA1</jats:italic> , <jats:italic>RAS1</jats:italic> , and <jats:italic>PKA1</jats:italic> ) also played a role in <jats:italic>G. mellonella</jats:italic> killing. Combination antifungal therapy (amphotericin B plus flucytosine) administered before or after inoculation was more effective than monotherapy in prolonging survival and in decreasing the tissue burden of cryptococci in the hemocoel. The <jats:italic>G. mellonella</jats:italic> - <jats:italic>C. neoformans</jats:italic> pathogenicity model may be a substitute for mammalian models of infection with <jats:italic>C. neoformans</jats:italic> and may facilitate the in vivo study of fungal virulence and efficacy of antifungal therapies. </jats:p>