Truncated Structural Variants of Lipoarabinomannan in Mycobacterium leprae and an Ethambutol-resistant Strain of Mycobacterium tuberculosis

Abstract

Current knowledge on the structure of lipoarabinomannan (LAM) has resulted primarily from detailed studies on a few selected laboratory strains of Mycobacterium tuberculosis, Mycobacterium bovis BCG, and Mycobacterium smegmatis. Our previous work was the first to report on the salient structural features of M. tuberculosis clinical isolates and demonstrated significant structural variations. A prime effort is to correlate a particular structural characteristic with observed differences in eliciting an immunobiological response, especially in the context of CD1-restricted presentation of LAM to T cells. T cell clones derived from the cutaneous lesions of leprosy patients have been shown to recognize specifically LAM from Mycobacterium leprae and not from M. tuberculosis Erdman or H37Rv. Herein we provide further fine structural data on LAM from M. leprae (LepLAM) and a tuberculosis clinical isolate, CSU20 (CSU20LAM), which was unexpectedly recognized by the supposedly LepLAM-specific CD1-restricted T cell clones. In comparison with the de facto laboratory LAM standard from M. tuberculosis H37Rv (RvLAM), LepLAM derived from in vivo grown M. leprae is apparently simpler in its arabinan architecture with a high degree of exposed, non-mannose-capped termini. On the other hand, CSU20, an ethambutol-resistant clinical isolate, makes a vastly heterogeneous population of LAM ranging from rather small and non-mannose-capped to full-length and fully capped variants. LepLAM and CSU20LAM contain a higher level of succinylation than RvLAM, which, in the context of truncated or less elaborated arabinan, may contribute to selective recognition by T cells. LAM from all species could be resolved into discrete forms by isoelectric focusing based apparently on their arabinan heterogeneity. In the light of our current and more recent findings, we reason that all immunobiological data should be cautiously interpreted and that the actual LAM variants that may be present in vivo during infection and pathogenesis need to be taken into consideration.

Identification of serological biomarkers of infection, disease progression and treatment efficacy for leprosy

“…The native MLSA was prepared as previously described (Marques et al 1998). LAM was purified from whole M. leprae cells as previously described (Torrelles et al 2004). Certain CSU-produced recombinant proteins, native MLSA, ND-O-BSA and LepLAM are available through the Biodefense and Emerging Infections Research Resources Repository (beiresources.org/TBVTRMResearchMaterials/tabid/1431/Default.aspx).…”

Structural Differences in Lipomannans from Pathogenic and Nonpathogenic Mycobacteria That Impact CD1b-restricted T Cell Responses

“…SmegLM, TB-LM, TB-PIM, and LepLAM PurificationsSmegLM and TB-LM purifications were performed as we reported previously (4). The pure LM populations (at 1 g/l sample buffer) were analyzed by 15% SDS-PAGE followed by periodic acid silver staining.…”

Broadening Our View About the Role of Mycobacterium tuberculosis Cell Envelope Components During Infection: A Battle for Survival

“…Some studies confirmed an average of 3 fatty acids per molecule of ManLAM in positions 1 and 2 of the ns-glycerol and position 6 of the Manp unit linked to C-2 of the myo-inositol . Studies by Chatterjee and colleagues performed in an ethambutol resistant strain of M.tb supported the existence of tetraacylated ManLAM as the most common molecular form (Torrelles et al, 2004). Thus, the only fact that can be generalized is that, with the exception of the lysoforms of ManLAM (only one fatty acid in the ManLAM anchor), ManLAM at least has two fatty acids, with both fatty acids in the ns-glycerol unit, where 16:0 and TBST are at position 1 and at position 2, respectively.…”

“…Delmas et al used nuclear magnetic resonance spectroscopy to locate the succinic groups (1 to 4 per molecule) in the C-2 of the 3,5--D-Araf and/or 5--D-Araf residues in ManLAM from different Mycobacterium bovis BCG strains (Delmas et al, 1997). Later, studies performed by Chatterjee and colleagues analyzing the content of succinates in ManLAMs from different mycobacterial species and strains showed that Mycobacterium leprae, the M.tb laboratory strain H 37 R v, and a M.tb clinical isolate (CSU 20) had also succinates (Torrelles et al, 2004); where ManLAM from M. leprae, the laboratory strain H 37 R v , and CSU20 had an average number of 7, 2 and 4 succinates, respectively. The succinates biological function in ManLAM is still a question to be resolve.…”