Abstract
Pathogenic yeast species can cause life-threatening infections in humans. The two leading yeast pathogens, Candida albicans and Cryptococcus neoformans, cause systemic infections in >1.4 million patients world-wide with mortality rates approaching 75%. It is thus imperative to study fungal virulence mechanisms, stress response pathways, and the efficacy of antifungal drugs. This is commonly done using mammalian models. To address ethical and practical concerns, invertebrate models, such as wax moth larvae, nematodes, or flies, have been introduced over the last two decades. To address short-comings in existing invertebrate host models, we developed fifth instar caterpillars of the Tobacco Hornworm moth Manduca sexta as a novel host model for the study of fungal virulence and drug efficacy. These caterpillars can be raised at standardised conditions, maintained at 37°C, can be injected with defined amounts of yeast cells, and are susceptible to the most threatening yeast pathogens, including C. albicans, C. neoformans, C. auris, and C. glabrata. Infected caterpillars can be rescued by treatment with commonly deployed antifungal drugs and importantly, fungal burden can be assessed daily throughout the course of infection in a single caterpillar’s faeces and hemolymph. Notably, these animals are large enough so that weight provides a reliable and reproducible measure of fungal virulence. This model combines a suite of parameters that recommend it for the study of fungal virulence.