, 2007). In addition to the above-mentioned reporter systems, gene expression of C. albicans cells in infected organs can be directly measured by quantitative real-time PCR (qRT-PCR). Sufficient fungal RNA can be extracted from infected organs to allow analysis of expression of
selected subsets of fungal genes (reviewed in Brown et al., 2007). These studies have focused mainly on virulence factors, such as secreted enzymes and adhesins, and have shown that these genes are expressed in specific niches during infection. The addition of an RNA amplification step, following extraction of RNA from fungal cells from infected kidneys, allows fungal gene expression changes during infection to be analysed by transcript profiling. In comparison with C. albicans cells NVP-BKM120 grown in vitro, fungal cells from infected mouse kidneys demonstrated altered, mostly downregulated, expression of approximately one-fifth of the genome (Andes et al., 2005). These gene expression changes reflected a switch to a filamentous growth form Olaparib clinical trial and growth in a glucose-poor environment. Emergence of fungal drug resistance in an antifungal-treated host has also been studied in mouse systemic infection models (Andes et al., 2006). In the mouse, ineffective antifungal dosing regimens
allowed the emergence of resistant isolates, where effective antifungal doses prevented this. In addition, mouse infection models have confirmed that C. albicans SB-3CT strains with specific drug resistance mutations
are more resistant to antifungal therapy, with the greatest resistance seen in strains with multiple genomic mutations (Park et al., 2005; MacCallum et al., 2010). Mouse models have been instrumental in understanding host responses during the initiation and progression of systemic Candida infection, with the advantage of allowing manipulation of the host, either through use of neutralizing antibodies, immunosuppressive treatment or by creating knockout mice. Such host manipulations allow mimicking of susceptible hosts, for example patients depleted in B cells, T cells, macrophages or neutrophils or with specific gene mutations, and allows the effects of these manipulations on host responses or susceptibility to infection to be analysed. Modelling disseminated C. albicans infection by intravenous injection in normal mice demonstrated that fungal growth was controlled in the liver and spleen, while fungal burdens increased in the kidneys (MacCallum & Odds, 2005; Lionakis et al., 2010). In the kidneys, fungal burden increases were accompanied by increasing immune infiltrates (MacCallum et al., 2009a; Castillo et al., 2011). This did not occur in other organs. Analyses of cytokine and chemokine levels in infected organs elucidated obvious organ-specific responses, with high cytokine and chemokine levels in infected kidneys, but reduced responses in the spleen (Spellberg et al., 2003; MacCallum et al., 2009a).