Repurposing histone deacetylase inhibitors (HDACi) to treat Candida glabrata infections

Candida glabrata currently accounts for 25 % of all fungal cases in UK hospitals, second only to C. albicans. This number is expected to rise given the intrinsic anti-fungal resistance of this species and the difficulty in treating it. In an effort to identify novel-anti fungal targets in C. glabrata, we used comparative genomics within Saccharomycotina yeast to predict which genes are under positive selection in this species specifically. Such genes are predicted to have influenced the adaptation of C. glabrata from a free-living microbe to a human pathogen, potentially due to functional shift(s) of the proteins they encode. Our analysis predicts that histone acetylation pathways are under positive selection in C. glabrata. Thereforewe hypothesised that we could use histone deacetylase inhibitors (HDACi) to interfere with histone acetylation levels and impact C. glabrata virulence. By treating C. glabrata withbroad spectrum HDACis we show it has a reduced capacity to form biofilms, it is less well adapted to high salt conditions typically found within a human host, and most importantly, it reverts to a more anti-fungal sensitive state. RNAseq analysis indicates that HDACi treatment interferes with the C. glabrata transcriptional response to anti-fungal treatment, rendering it incapable of combating against these drugs. Furthermore, using an in vivo worm model of candidiasis, we show that HDACi treatment in conjunction with the anti-fungal fluconazole, can increase the survival rate of individuals with C. glabrata infections. Taken together our data suggest that the health threat posed by C. glabrata might be addressed by repurposing HDACi to treat this infection.