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The mannose cap of mycobacterial lipoarabinomannan does not dominate the Mycobacterium-host interaction |
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| Authors: | Appelmelk B J den Dunnen J Driessen N N Ummels R Pak M Nigou J Larrouy-Maumus G Gurcha S S Movahedzadeh F Geurtsen J Brown E J Eysink Smeets M M Besra G S Willemsen P T J Lowary T L van Kooyk Y Maaskant J J Stoker N G van der Ley P Puzo G Vandenbroucke-Grauls C M J E Wieland C W van der Poll T Geijtenbeek T B H van der Sar A M Bitter W |
| Institution: | Departments of Medical Microbiology and Infection Control and;Molecular Cell Biology, VU University Medical Center, 1081 BT Amsterdam, the Netherlands.; Netherlands Vaccine Institute, 3720 AL, Bilthoven, the Netherlands.; Program in Microbial Pathogenesis and Host Defense, University of California, San Francisco, CA 94143, USA.; Département 'Mécanismes Moléculaires des Infections Mycobactériennes', Institut de Pharmacologie et de Biologie Structurale, CNRS UMR 5089, 31077-Toulouse cedex 4, France.; School of Biosciences, The University of Birmingham, Edgbaston, Birmingham B15 2TT, UK.; Department of Pathology and Infectious Diseases, Royal Veterinary College, London NW1 0TU, UK.; CIDC-Lelystad, Central Institute for Animal Disease Control, Department Bacteriology and TSEs, 8203 AA Lelystad, the Netherlands.; Alberta Ingenuity Centre for Carbohydrate Science and Department of Chemistry, University of Alberta, Edmonton, AB T6G 2G2, Canada.; Center of Infection and Immunity Amsterdam (CINIMA), Academic Medical Centre, Amsterdam, the Netherlands. |
| Abstract: | Pathogenic mycobacteria have the ability to persist in phagocytic cells and to suppress the immune system. The glycolipid lipoarabinomannan (LAM), in particular its mannose cap, has been shown to inhibit phagolysosome fusion and to induce immunosuppressive IL?10 production via interaction with the mannose receptor or DC-SIGN. Hence, the current paradigm is that the mannose cap of LAM is a crucial factor in mycobacterial virulence. However, the above studies were performed with purified LAM, never with live bacteria. Here we evaluate the biological properties of capless mutants of Mycobacterium marinum and M. bovis BCG, made by inactivating homologues of Rv1635c. We show that its gene product is an undecaprenyl phosphomannose-dependent mannosyltransferase. Compared with parent strain, capless M. marinum induced slightly less uptake by and slightly more phagolysosome fusion in infected macrophages but this did not lead to decreased survival of the bacteria in vitro , nor in vivo in zebra fish. Loss of caps in M. bovis BCG resulted in a sometimes decreased binding to human dendritic cells or DC-SIGN-transfected Raji cells, but no differences in IL-10 induction were observed. In mice, capless M. bovis BCG did not survive less well in lung, spleen or liver and induced a similar cytokine profile. Our data contradict the current paradigm and demonstrate that mannose-capped LAM does not dominate the Mycobacterium –host interaction. |
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