Sensitive detection of hydrophobic antigens using a novel lipid-aggregate based ELISA

Competitive ELISA for the Detection and Quantification of Mycobacterium ulcerans Mycolactone

Lipids and other hydrophobic analytes are difficult to quantify by routine immunoassays due to the need to use aqueous buffers. Here, we describe an ELISA protocol suitable for the detection of mycolactone, the polyketide toxin of Mycobacterium ulcerans, the causative agent of Buruli ulcer (BU). Given that mycolactone is unique to this species and has been found in all M. ulcerans lineages, the assay herein described has the potential to be useful both as a research tool and as a diagnostic test, even in low-resource BU endemic regions. Furthermore, the triethanolamine buffer described here may also be useful in the specific detection of other lipid analytes by ELISA.

Development of an ELISA for the quantification of mycolactone, the cytotoxic macrolide toxin of Mycobacterium ulcerans

Mycolactones, macrolide cytotoxins, are key virulence factors of Mycobacterium ulcerans, the etiological agent of the chronic necrotizing skin disease Buruli ulcer. There is urgent need for a simple point-of-care laboratory test for Buruli ulcer and mycolactone represents a promising target for the development of an immunological assay. However, for a long time, all efforts to generate mycolactone-specific antibodies have failed. By using a protein conjugate of a truncated non-toxic synthetic mycolactone derivative, we recently described generation of a set of mycolactone-specific monoclonal antibodies. Using the first mycolactone-specific monoclonal antibodies that we have described before, we were able to develop an antigen competition assay that detects mycolactones. By the systematic selection of a capturing antibody and a reporter molecule, and the optimization of assay conditions, we developed an ELISA that detects common natural variants of mycolactone with a limit of detection in the low nanomolar range. The mycolactone-specific ELISA described here will be a very useful tool for research on the biology of this macrolide toxin. After conversion into a simple point-of-care test format, the competition assay may have great potential as laboratory assay for both the diagnosis of Buruli ulcer and for the monitoring of treatment efficacy.