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Start Over Author "Giquel, B." Topic mycobacterium tuberculosis
2 results on '"Giquel, B."'

1. Neutral-red reaction is related to virulence and cell wall methyl-branched lipids in Mycobacterium tuberculosis.

Author

Cardona PJ, Soto CY, Martín C, Giquel B, Agustí G, Andreu N, Guirado E, Sirakova T, Kolattukudy P, Julián E, and Luquin M

Subjects
Animals, Bacterial Typing Techniques, Coloring Agents metabolism, Cytokines metabolism, Female, Gene Expression Regulation, Mice, Mice, Inbred C57BL, Mutation, Mycobacterium tuberculosis cytology, Mycobacterium tuberculosis genetics, RNA, Messenger metabolism, Staining and Labeling, Virulence, Cell Wall chemistry, Cell Wall metabolism, Lipid Metabolism, Mycobacterium tuberculosis metabolism, Mycobacterium tuberculosis pathogenicity, Neutral Red metabolism, Tuberculosis microbiology
Abstract

Searching for virulence marking tests for Mycobacterium tuberculosis, Dubos and Middlebrook reported in 1948 that in an alkaline aqueous solution of neutral-red, the cells of the virulent H37Rv M. tuberculosis strain fixed the dye and became red in color, whereas the cells of the avirulent H37Ra M. tuberculosis strain remained unstained. In the 1950 and 1960s, fresh isolates of M. tuberculosis were tested for this neutral-red cytochemical reaction and it was reported that they were neutral-red positive, whereas other mycobacteria of diverse environmental origins that were non-pathogenic for guinea pigs were neutral-red negative. However, neutral-red has not really been proven to be a virulence marker. To test if virulence is in fact correlated to neutral-red, we studied a clinical isolate of M. tuberculosis that was originally neutral-red positive but, after more than 1 year passing through culture mediums, turned neutral-red negative. We found that, in comparison to the original neutral-red positive strain, this neutral-red negative variant was attenuated in two murine models of experimental tuberculosis. Lipid analysis showed that this neutral-red negative natural mutant lost the capacity to synthesize pthiocerol dimycocerosates, a cell wall methyl-branched lipid that has been related to virulence in M. tuberculosis. We also studied the neutral-red of different gene-targeted M. tuberculosis mutants unable to produce pthiocerol dimycocerosates or other cell wall methyl-branched lipids such as sulfolipids, and polyacyltrehaloses. We found a negative neutral-red reaction in mutants that were deficient in more than one type of methyl-branched lipids. We conclude that neutral-red is indeed a marker of virulence and it indicates important perturbations in the external surface of M. tuberculosis cells.

Published
2006
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2. Rôle des cellules dendritiques humaines dans la tuberculose : protecteur ou non protecteur ?

Author

Jean-Louis Herrmann, Tailleux L, Nigou J, Giquel B, Puzo G, Ph, Lagrange, Neyrolles O, Hopital Saint-Louis [AP-HP] (AP-HP), Assistance publique - Hôpitaux de Paris (AP-HP) (AP-HP), Génétique mycobactérienne - Mycobacterial genetics, Institut Pasteur [Paris] (IP), Institut de pharmacologie et de biologie structurale (IPBS), Université Toulouse III - Paul Sabatier (UT3), and Université de Toulouse (UT)-Université de Toulouse (UT)-Centre National de la Recherche Scientifique (CNRS)

Subjects
MESH: Humans, MESH: Mycobacterium tuberculosis, MESH: Dendritic Cells, MESH: Antigen-Presenting Cells, Polysaccharides, Bacterial, Toll-Like Receptors, Antigen-Presenting Cells, Dendritic Cells, Mycobacterium tuberculosis, [SDV.IMM.II]Life Sciences [q-bio]/Immunology/Innate immunity, [SDV.MHEP.MI]Life Sciences [q-bio]/Human health and pathology/Infectious diseases, Humans, Tuberculosis, Lectins, C-Type, MESH: Tuberculosis, MESH: Polysaccharides, Bacterial, MESH: Lectins, C-Type, MESH: Toll-Like Receptors
Abstract

International audience; Mycobacterium tuberculosis, the cause of tuberculosis remains a pathogenic organism capable of infecting a large number of individuals and of resisting the immune response of the infected host. The main constituents of this response are the antigen presenting cells such as dendritic cells, macrophages and T lymphocytes.; IntroductionMycobacterium tuberculosis, agent de la tuberculose, reste un organisme pathogène capable d’infecter un grand nombre d’individus, et de résister à la réponse immune de l’hôte infecté. Les acteurs principaux de cette réponse immune sont les cellules présentatrices d’antigènes comme les cellules dendritiques, les macrophages et les lymphocytes T.État des connaissancesL’étude comparative des interactions entre M. tuberculosis et les cellules présentatrices d’antigène a permis de montrer que les cellules dendritiques ne permettent pas la croissance intracellulaire de M. tuberculosis, à la différence de ce que l’on observe dans les macrophages. Un compartiment intracellulaire hostile crée les conditions d’une bactériostase. M. tuberculosis st internalisé en se liant à un récepteur des cellules dendritiques de type lectine (DC-SIGN).PerspectivesCe récepteur reconnaît des composés sucrés que l’on retrouve à la surface de la paroi de M. tuberculosis. Ce lien sucres-lectine pourrait compenser le lien composés bactériens-récepteur de type Toll, inhibant partiellement la réaction inflammatoire protectrice, ou compensant une réaction inflammatoire excessive.ConclusionsCe lien favoriserait également la persistance de la bactérie à l’état quiescent dans les cellules dendritiques, et l’adaptation réciproque de l’hôte et de la bactérie au cours du temps.

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