REQUIREMENT FOR THE CANDIDA-ALBICANS FAS2 GENE FOR INFECTION IN A RATMODEL OF OROPHARYNGEAL CANDIDIASIS

The virulence of Candida albicans strains deficient in fatty acid synt hase activity by virtue of disruption/deletion of the FAS2 gene was ex amined in a rat model of oropharyngeal candidiasis. The FAS2 alleles o f C. albicans CAl4 (Delta ura3::imm434 / Delta ura3::imm434) were sequ entially disrupted with a cassette that included a portion of FAS2 fro m which a 984 bp fragment containing the FAS condensing reaction domai n was deleted and replaced with hisG-URA3-hisG sequences. Verification of fatty acid synthase inactivation was obtained from assays of enzym e activity. Strains in which a single allele was disrupted (CFD1 and C FD3) exhibited an approximately 20% reduction in activity, when compar ed to wild-type. In addition, fatty acid synthase activity was abolish ed in a FAS2 null mutant strain (CFD2), and growth of CFD2 occurred on ly when the growth medium was supplemented with Tween 40 and certain f atty acids. Strain CFD2 was avirulent in the rat model, indicating tha t fatty acid synthase activity is required for C. albicans oropharynge al infection. Strains with a single FAS2 allele disruption colonized t he oral cavity, but the number of cells recovered from infected animal s was approximately fivefold less than for the parental strain. The re sults suggest that FAS may be exploited as a possible target for the d evelopment of new antifungal agents.