Lipoarabinomannans are major mycobacterial antigens capable of modulating the host immune response; however, the molecular basis underlying the diversity of their immunological properties remain an open question. In this study a new extraction and purification approach was successfully applied to isolate ManLAMs (lipoarabinomannans with mannosyl extensions) from bacillus Calmette Gué rin leading to the obtention of two types of ManLAMs namely parietal and cellular. Structurally, they were found to differ by the percentage of mannooligosaccharide caps, 76 and 48%, respectively, and also, thanks to a new analytical method, by the structure of the phosphatidyl-myo-inositol anchor lipid moiety. A novel fatty acid in the mycobacterium genus assigned to a 12-O-(methoxypropanoyl)-12-hydroxystearic acid was the only fatty acid esterifying C-1 of the glycerol residue of the parietal ManLAMs, while the phosphatidyl unit of the cellular ManLAMs showed a large heterogeneity due to a combination of palmitic and tuberculostearic acid. Finally, parietal and cellular ManLAMs were found to differentially affect interleukin-8 and tumor necrosis factor-␣ secretion from human dendritic cells. We show that parietal but not cellular ManLAMs were able to stimulate tumor necrosis factor-␣ secretion from dendritic cells. From these studies we propose that the 1-[12-O-(methoxypropanoyl)-12-hydroxystearoyl]-sn-glycerol part is the major cytokineregulating component of the ManLAMs. It seems likely that modification of the ManLAM lipid part, which may occur in hostile environments, could regulate macrophagic mycobacterial survival by altering cytokine stimulation.Tuberculosis remains the leading cause of human death among the infectious diseases with over 3 million deaths each year (1). The decline in tuberculosis in the developed countries has been reversed by the tuberculosis cases arising in AIDS patients, among the homeless, and by the emergence of Mycobacterium tuberculosis strains resistant to the first-line drugs, which are isoniazid and ethambutol. Also, from different trials, the efficiency of BCG 1 vaccine to prevent tuberculosis was found to range from 0 to 80% (2, 3).Virulent mycobacteria survive and multiply within phagosomes of mononuclear phagocytes. Despite conflicting results, there is a consensus that phagosomes containing M. tuberculosis do not fuse with lysosomes and resist acidification (4). This survival can also be correlated with the macrophage bactericide activity, which appears to be modulated by mycobacterial cell wall components (5, 6).From a molecular point of view, cell wall lipoarabinomannans (LAMs) are clearly demonstrated to be pivotal mycobacterial antigens. They regulate TNF-␣ production by phagocyte (5) and block the transcriptional activation of INF-␥ (6), thereby influencing the intramacrophagic survival of mycobacteria. For instance, LAMs (PI-GAMs) from Mycobacterium smegmatis, a fast growing mycobacterium that does not survive inside the macrophages, were found to stimulate phagocyte TNF-␣ production ...

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Thirteen strains of Burkholderia cepacia from various origins with mucoid and non-mucoid phenotypes were assayed for exopolysaccharide (EPS) production. The EPS were characterized by glycosyl composition analysis and examination of the products resulting from lithium-ethylenediamine and Smith degradations. The results showed that all strains, including the non-mucoid strains, were able to produce EPS exhibiting the same structural features, i.e. presence of one rhamnosyl, three galactosyl, one mannosyl, one glucosyl and one glucuronosyl residues, suggesting that this EPS is representative of the B. cepacia species.