A Drosophila model of Candida albicans gastrointestinal infection

Aims

This research aims to use infection of fruit flies to identify key genes associated with the pathogenicity of Candida albicans, replacing the use of vertebrates in this research and demonstrating the utility of the approach for similar studies.

Background

The C. albicans fungus is a normal part of the gut microflora, which in rare cases can cause life-threatening bloodstream infections, particularly in immunocompromised patients. Little is known about the pathogenic attributes that allow this to happen. Libraries of mutant C. albicans have been produced to identify the genes responsible.

Around 15,000 mice would be required to screen a library of 3,000 C. albicans mutants. This research aims to demonstrate the utility of the fruit fly as an alternative model for screening for fungal pathogenicity.

Research details and methods

A recently developed fruit fly (Drosophila melanogaster) model of gastrointestinal infection by C. albicans, which uses green fluorescent protein to visualise immune system activation, will be used for screening. Under sterile conditions D. melanogaster larva are added to a 96-well plate, with each well containing an appropriate C. albicans strain from a homozygous deletion library of 3,000 strains. These are incubated and the resulting fluorescent immune activation determined.

Genes from C. albicans strains which under- or hyper-activate the fly’s immune response will be reintroduced into the mutant background and compared in the fly assay to confirm their function – the expectation is that the activation of immunity will be the same as with wild type Candida.  

Candida albicans is a commensal fungus that can cause life-threatening bloodstream infections. However, very little is known about the pathogen attributes that allow a mucosal infection to become systemic. As pathogen genomic libraries become available it is financially unrealistic and ethically problematic to individually test them in mammalian models. We have therefore developed the fruit fly Drosophila melanogaster as an alternative host. We propose to screen by gastrointestinal infection a large C. albicans homozygous deletion library to find those strains unable or hyperactive in inducing systemic immunity. This screen will reduce considerably future experiments in mice.