Lipids of ‘Mycobacterium habana’, a synonym of Mycobacterium simiae with vaccine potential

Structural studies of cord factors from Mycobacterium simiae related to the capacity for tumour necrosis factor alpha (α-TNF) induction

The structure of cord factor was studied in several strains of Mycobacterium simiae, including 'habana' TMC 5135, considered as highly immunogenic in experimental tuberculosis and leprosy. The mycolic acids liberated from cord factor were identified in all cases as α'-, α- and keto-mycolates. According to the general NMR and MS data, α'-mycolates were mono-unsaturated and contained from 64 to 68 carbon atoms, whereas α-mycolates mainly presented two 2,3-disubstituted cyclopropane rings and a chain length of 80-91 carbon atoms; keto-mycolates mostly contained one cyclopropane ring and 85-91 carbon atoms. Taking into account the (1)H-NMR results, strains varied in the ratio of the different mycolates, and the high levels of keto-mycolates found in the cord factors of TMC 5135 and ATCC 25275(T) stood out. Notably, MS revealed that the odd carbon number series of α-mycolates (C87-C89) predominated in the cord factor of TMC 5135, in contrast to the remaining studied strains, in which the even (C84-C86) and odd carbon number series appeared more equal. The fine structural differences detected among the cord factors studied did not seem to be relevant to the general capacity of these molecules to induce the secretion of tumour necrosis factor alpha, as the cord factors from several strains of M. simiae (TMC 5135, IPK-342 and ATCC 25275(T)) induced similar amounts of this cytokine in RAW 264.7 cells.

New variants of polar glycopeptidolipids detected in Mycobacterium simiae, including 'habana' strains, as evidenced by electrospray ionization-ion trap-mass spectrometry

AIMS

To determine the composition of polar glycopeptidolipids (pGPLs) of Mycobacterium simiae and, particularly, those of 'habana' strains, in a search for specific markers given the immunogenic potential of 'habana' TMC 5135 in experimental tuberculosis.

METHODS AND RESULTS

pGPLs were determined in free lipid extracts using electrospray ionization-ion trap-mass spectrometry (ESI-IT-MS), working in both negative- and positive-ion mode. In the case of TMC 5135, the presence of the previously characterized GPL-II (containing 2,4-di-O-CH(3) glucuronic acid as distal sugar in the oligosaccharide antigenic moiety) and GPL-III (containing 4-O-CH(3) glucuronic acid as distal sugar) was confirmed using MS/MS and MS/MS/MS approaches. Interestingly, some 'habana' strains presented variants of GPL-II, designated GPL-II'-A and GPL-II'-B. A di-O-CH(3)-deoxy-hexose (tentatively, 2,3-di-O-CH(3)-fucose) was identified as the penultimate sugar in the oligosaccharide moiety of GPL-II'-A, whereas in GPL-II'-B the penultimate sugar was fucose (tentative identification). On the contrary, the distal sugar of the oligosaccharide chain of pGPLs of Myco. simiae ATCC 25275(T) was identified as tri-O-CH(3)-glucuronic acid (designated GPL-sim(T)-I, with two variants: GPL-sim(T)-I-A and GPL-sim(T)-I-B), O-CH(3)-glucuronic acid (designated GPL-sim(T)-II) and di-O-CH(3)-glucuronic acid (GPL-II'-A and GPL-II'-B). The penultimate sugar of the oligosaccharide chain of GPL-sim(T)-I-A and GPL-sim(T)-II was identified as di-O-CH(3)-deoxy-hexose (tentatively, 2,3-di-O-CH(3) fucose), and that of GPL-sim(T)-I-B as deoxy-hexose (tentatively, fucose). In all strains studied, each [M-H](-) and [M+Na](+) ion was revealed as a mixture of homologous compounds varying in the number of -O-CH(3) groups present in the oligosaccharide moiety and in the length of the fatty acyl linked to the peptide.

CONCLUSIONS

The present work indicates that, within a similar general pattern of pGPLs, different strains of Myco. simiae present some variations, so that new compounds (GPL-II'-A, GPL-II'-B, GPL-sim(T)-I-A, GPL-sim(T)-I-B and GPL-sim(T)-II) were defined. Noteworthy was the fact that the 'habana' strains clearly differed from the type strain of Myco. simiae.

SIGNIFICANCE AND IMPACT OF THE STUDY

The data obtained can be used in the delineation of the 'habana' group of Myco. simiae, including the quality control of the immunogenic strain 'habana' TMC 5135.