OR30

1:Swiss Tropical and Public Health Institute; 2:University of Basel; 3:Swiss Federal Institute of Technology Zürich

Early diagnosis is integral to effective Buruli ulcer (BU) control. Consequently, continued efforts are being made to improve the speed of diagnosis at the point-of-care. Mycolactone is integral to Mycobacterium ulcerans pathogenesis and is responsible for the main symptoms of the disease. This polyketide exotoxin is unique to M. ulcerans and is produced by every known strain of the bacterium, making it an ideal marker for specific BU diagnosis. The surface protein MUL_3720 is highly expressed on clinical M. ulcerans strains, and although also found in some environmental mycobacteria, is absent in typical pathogenic mycobacteria. Together, both analytes can constitute complementary biomarkers of M. ulcerans presence in clinical samples.

We have generated series of monoclonal antibodies (mAbs) against both analytes and developed antigen capture ELISAs using these mAbs for the specific detection of low nanomolar levels of mycolactone and MUL_3720 in a variety of laboratory and clinical samples. Extensive optimisation of assay parameters, particularly buffer optimisation to counteract matrix effects from serum-rich samples, allows these assays function adequately with crude samples. This makes them more amenable for point-of-care use in the typically low-resource settings that suffer the highest BU prevalence. Additionally, we have converted these ELISAs into an electrochemiluminescent (ECL) format, which is 10 – 50x more sensitive than a typical ELISA. Assessment of these assays with BU lesion samples is planned in the coming months. These assessments will, amongst other things, allow for an estimation of how much of these analytes are present in a typical BU lesion.