Pathway analysis of Candida albicans survival and virulence determinants in a murine infection model

Abstract

One potentially rich source of possible targets for antifungal therapy are those Candida albicans genes deemed essential for growth under the standard culture (i.e., in vitro) conditions; however, these genes are largely unexplored as drug targets because essential genes are not experimentally amenable to conventional gene deletion and virulence studies. Using tetracycline-regulatable promoter-based conditional mutants, we investigated a murine model of candidiasis in which repressing essential genes in the host was achieved. By adding doxycycline to the drinking water starting 3 days prior to (dox − 3D) or 2 days post (dox þ 2D) infection, the phenotypic consequences of temporal gene inactivation were assessed by monitoring animal survival and fungal burden in prophylaxis and acute infection settings. Of 177 selected conditional shutoff strains tested, the virulence of 102 was blocked under both repressing conditions, suggesting that the corresponding genes are essential for growth and survival in a murine host across early and established infection periods. Among these genes were those previously identified as antifungal drug targets (i.e., FKS1, ERG1, and ERG11), verifying that this methodology can be used to validate potential new targets. We also identify genes either conditionally essential or dispensable for in vitro growth but required for survival and virulence, including those in late stage ergosterol synthesis, or early steps in fatty acid or riboflavin biosynthesis. This study evaluates the role of essential genes with respect to pathogen virulence in a large-scale, systems biology context, and provides a general method for gene target validation and for uncovering unexpected antimicrobial targets.animal model | antifungal target | conditional expression | systemic candidiasis | virulence factor

Exploiting mitochondria as targets for the development of new antifungals

“…Importantly, and mmm1D is conditionally avirulent mutant (http://www.candidage nome.org/). 37 Another of the ERMES complex protein subunits from C. albicans is Fzo1p a GTPase protein. The fzo1D mutant had fragmented mitochondria, loss of mitochondrial genome, phospholipid alterations, as well as heightened susceptibility to azoles and peroxide.…”

Riboflavin and pantothenic acid biosynthesis are crucial for iron homeostasis and virulence in the pathogenic mold Aspergillus fumigatus

“…Lung CFU enumeration and histology show complete clearance of the fungus from the lungs 48 h after infection. Riboflavin auxotrophy also leads to avirulence in Candida albicans [6], Histoplasma capsulatum [23] and in many species of gram-negative bacteria including Mycobacteria that lack a riboflavin uptake system and are therefore totally dependent on endogenous biosynthesis [44]. Therefore, this pathway is particularly suitable for the development of antimicrobials.…”

“…Using a combination of comparative genomics, transcriptomics and metabolic flux analysis, we recently identified 64 fungal-specific targets including metabolic enzymes participating in amino acid, lipid and vitamin biosynthesis [8]. Of these, 18 targets have already been validated in the literature, including enzymes participating in the biosynthesis of aromatic amino acids [9], lysine [10,11], histidine [12] and cysteine/methionine [13] and in the biosynthesis of lipids, including phospholipids [14], fatty acids [6] and oxylipins [15]. However, the assessment of fungal-specific targets in the vitamin biosynthesis pathways and their importance during infection has not been well established.…”

Combining Proteomic Strategies and Molecular Display Technology for Development of Vaccines against Candida albicans

“…These 50 proteins were designated "FBS-induced proteins." Several previously identified virulence factors, for example, Alo1, Nag6, Phr1, Rpf2, and Sod5 [25][26][27][28][29], were included in this group, indicating that these proteins are potential virulence factors.…”