Buruli ulcer (BU) is a disfiguring and debilitating, yet neglected and emerging, tropical disease caused by Mycobacterium ulcerans via its unique lipid toxin, mycolactone. Before 2004, the only treatment was wide surgical excision and skin grafting. Studies in mouse footpad models first indicated the efficacy of rifampin plus streptomycin (RIF+STR). Following confirmatory clinical trials, RIF+STR for 8 wks. was endorsed by the WHO as a first-line treatment for BU. The greatest gap in BU control is now the lack of simple, rapid, point-of- care diagnostics to confirm the diagnosis at an early stage of disease, when RIF+STR is most effective. To overcome this critical bottleneck, we will develop novel, fieldable, highly sensitive methods for mycolactone detection in blood and tissue. While many have tried and failed to generate anti-mycolactone antibodies, our approach using powerful novel methods of phage and yeast display to select reproducible high-affinity antibodies from extremely large and diverse nave and patient-derived pools have already proven successful in selecting specific antibodies to mycolactone alone and mycolactone bound to a known in vivo target, WASP. Previous efforts to detect anti-mycolactone antibodies in patients or immunized animals were also based on the flawed premise that the toxin exists in a free form in vivo. Based on our prior experience with other amphiphilic biomarkers and computational modeling of mycolactone's interaction with lipid bilayers, we strongly believe that, outside host cells, mycolactone will always exist in complexes with host carriers such as high-density lipoprotein (HDL) or in association with cell membranes or membrane-derived vesicles. Therefore, our approach is to combine our knowledge of putative carriers and a discovery approach proven successful for other amphiphilic biomarkers to identify the most prevalent and relevant host mycolactone complexes and inhabited membrane architectures in vivo, select antibodies to those species and employ those antibodies in our innovative, highly sensitive and fieldable detection system. The 8-wk RIF+STR regimen requires injections with a relatively toxic agent (STR) and use of RIF, which causes many drug-drug interactions (e.g., with anti-HIV drugs). We will explore the development of shorter, simpler, entirely oral regimens based on recent advances in tuberculosis drug development and promising preliminary data in BU mouse models. We will leverage our experience in pre-clinical drug development for both diseases as well as our established relationships with the sponsors of new drugs in clinical trials. This will e carried out with tools developed with support from R01-AI082612, to comprehensively evaluate novel drug combinations for BU and prioritize them for clinical evaluation. Finally, because persistence of mycolactone in tissues during and after treatment may retard bacterial clearance and wound healing, we will exploit knowledge from our diagnostic discovery work pursue innovative antibody- and non-antibody-based anti- virulence strategies, seeking to neutralize mycolactone's toxic effects for adjunctive therapeutic benefit.
Our proposal, 'Closing the Gaps in Burul Ulcer Diagnosis, Treatment and Prevention' aims to (i) create innovative tools and approaches to develop new, highly sensitive diagnostic tests that can be used at the point-of-care to promote early diagnosis of Buruli ulcer, (ii) use established and newly developed animal models of Buruli ulcer to indicate potentially shorter, simpler or less toxic oral antibiotic treatments, and (iii) develop novel non-antibiotic treatments that improve treatment outcomes by neutralize the negative effects of the disease-promoting bacterial toxin.
|López, Cesar A; Unkefer, Clifford J; Swanson, Basil I et al. (2018) Membrane perturbing properties of toxin mycolactone from Mycobacterium ulcerans. PLoS Comput Biol 14:e1005972|
|Converse, Paul J; Almeida, Deepak V; Tasneen, Rokeya et al. (2018) Shorter-course treatment for Mycobacterium ulcerans disease with high-dose rifamycins and clofazimine in a mouse model of Buruli ulcer. PLoS Negl Trop Dis 12:e0006728|