Mycolactone-Mediated Virulence in M. ulcerans

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DESCRIPTION (provided by the applicant): Mycobacterium ulcerans is the causative agent of Buruli ulcer, a severe persistent skin infection which has been recently designated an emerging infection in West Africa. The disease has a unique pathology. Despite extensive tissue damage and the presence of a heavy bacterial load, there is little acute inflammatory response to the organism. A single Buruli ulcer may cover 15 percent of a person's body surface; the only cure is surgery and skin grafting. A polyketide-derived macrolide toxin designated mycolactone has been identified in M ulcerans. Macrolides are produced as secondary metabolites by soil bacteria and fungi. They have enormous pharmaceutical value as cytostatins, immunosuppressants, antifungal agents, antihelminthic agents and antibiotics. Mycolactone is the first macrolide identified from a pathogen. Evidence suggests that mycolactone is responsible for most of the pathology in Buruli ulcer. Mycolactone-mediated phenotypes include cell cycle arrest, immunosuppression and death via apoptosis. Neither the genetics of mycolactone synthesis nor its mechanism of action are known. The goals of this proposal are: 1) to clone and sequence genes for mycolactone biosynthesis, 2) to construct mutants defective in mycolactone production, and 3) to begin characterizing events in the cellular pathways involved in mycolactone mediated cell death and immunosuppression using micro-array gene-expression technology. Results from these studies should have a significant impact on the treatment and prevention of Buruli ulcer as well as provide insight into potential role of polyketides in other mycobacterial diseases such as tuberculosis. In addition, this work may provide useful insight into macrolide cell biology.