title: Differential arabinan capping of lipoarabinomannan modulates innate immune responses and impacts T helper cell differentiation.
abstract: Toll-like receptors (TLRs) recognize pathogens by interacting with pathogen-associated molecular patterns, such as the phosphatidylinositol-based lipoglycans, lipomannan (LM) and lipoarabinomannan (LAM). Such structures are present in several pathogens, including Mycobacterium tuberculosis, being important for the initiation of immune responses. It is well established that the interaction of LM and LAM with TLR2 is a process dependent on the structure of the ligands. However, the implications of structural variations on TLR2 ligands for the development of T helper (Th) cell responses or in the context of in vivo responses are less studied. Herein, we used Corynebacterium glutamicum as a source of lipoglycan intermediates for host interaction studies. In this study, we have deleted a putative glycosyltransferase, NCgl2096, from C. glutamicum and found that it encodes for a novel α(1→2)arabinofuranosyltransferase, AftE. Biochemical analysis of the lipoglycans obtained in the presence (wild type) or absence of NCgl2096 showed that AftE is involved in the biosynthesis of singular arabinans of LAM. In its absence, the resulting molecule is a hypermannosylated (hLM) form of LAM. Both LAM and hLM were recognized by dendritic cells, mainly via TLR2, and triggered the production of several cytokines. hLM was a stronger stimulus for in vitro cytokine production and, as a result, a more potent inducer of Th17 responses. In vivo data confirmed hLM as a stronger inducer of cytokine responses and suggested the involvement of pattern recognition receptors other than TLR2 as sensors for lipoglycans.
authors.affiliation: School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, United Kingdom.
authors.forename: Arun K
authors.initials: AK
authors.lastname: Mishra
authors.forename: Joana E
authors.initials: JE
authors.lastname: Alves
authors.forename: Karin
authors.initials: K
authors.lastname: Krumbach
authors.forename: Jerome
authors.initials: J
authors.lastname: Nigou
authors.forename: António G
authors.initials: AG
authors.lastname: Castro
authors.forename: Jeroen
authors.initials: J
authors.lastname: Geurtsen
authors.forename: Lothar
authors.initials: L
authors.lastname: Eggeling
authors.forename: Margarida
authors.initials: M
authors.lastname: Saraiva
authors.forename: Gurdyal S
authors.initials: GS
authors.lastname: Besra
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D002478:Cells, Cultured; D003354:Corynebacterium Infections / Q000276:immunology* / Q000382:microbiology / Q000503:physiopathology; D048230:Corynebacterium glutamicum / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D007113:Immunity, Innate; D008070:Lipopolysaccharides / Q000276:immunology* / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D011134:Polysaccharides / Q000276:immunology / Q000378:metabolism*; D058504:Th17 Cells / Q000166:cytology* / Q000276:immunology
chemical_list: D008070:Lipopolysaccharides; D011134:Polysaccharides; C050016:lipoarabinomannan; C030080:araban