Abstract

Lipoarabinomannan (LAM) is a useful biomarker for detection of M. tuberculosis infection and disease. Related antigens can be detected in urine samples of TB patients by combinations of monoclonal anti-bodies (mAbs) directed against specific epitopes expressed in LAM. While sensitive for samples from patients with active TB disease who have HIV-1 co-infections, these assays are less effective for other populations, and there is therefore a need for more sensitive antibodies that can improve the sensitivity of these assays. Here we characterize the antigen and epitope specificities, sequence diversity and isotype dependencies of eight LAM-specific human mAbs that target five distinct arabinose- and man-nose-dependent epitopes present in LAM and lipoarabinomannan (LM). Whereas all of the mAbs rec-ognized ManLAM, only a few, including A194-01, consistently detected antigens in TB+ urine samples. Converting A194-01 from the IgG1 to the IgM isotype resulted in broader recognition of poly-Ara glycan epitopes, and increased sensitivity for clinical antigens when combined with several capture reagents, including RU95-C1, a novel antibody targeting the mannan domain of LAM. These results define novel epitopes that are differentially expressed in bacterial and urinary forms of LAM, and identify novel anti-body combinations which possess enhanced diagnostic utility for clinical forms of LAM.