title: Bordetella pertussis Lipid A Recognition by Toll-like Receptor 4 and MD-2 Is Dependent on Distinct Charged and Uncharged Interfaces.
abstract: Lipid A in LPS activates innate immunity through the Toll-like receptor 4 (TLR4)-MD-2 complex on host cells. Variation in lipid A has significant consequences for TLR4 activation and thus may be a means by which Gram-negative bacteria modulate host immunity. However, although even minor changes in lipid A structure have been shown to affect downstream immune responses, the mechanism by which the TLR4-MD-2 receptor complex recognizes these changes is not well understood. We previously showed that strain BP338 of the human pathogen Bordetella pertussis, the causative agent of whooping cough, modifies its lipid A by the addition of glucosamine moieties that promote TLR4 activation in human, but not mouse, macrophages. Using site-directed mutagenesis and an NFκB reporter assay screen, we have identified several charged amino acid residues in TLR4 and MD-2 that are important for these species-specific responses; some of these are novel for responses to penta-acyl B. pertussis LPS, and their mutation does not affect the response to hexa-acylated Escherichia coli LPS or tetra-acylated lipid IVA. We additionally show evidence that suggests that recognition of penta-acylated B. pertussis lipid A is dependent on uncharged amino acids in TLR4 and MD-2 and that this is true for both human and mouse TLR4-MD-2 receptors. Taken together, we have demonstrated that the TLR4-MD-2 receptor complex recognizes variation in lipid A molecules using multiple sites for receptor-ligand interaction and propose that host-specific immunity to a particular Gram-negative bacterium is, at least in part, mediated by very subtle tuning of one of the earliest interactions at the host-pathogen interface.
authors.affiliation: From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 and.
authors.forename: Nina
authors.initials: N
authors.lastname: Maeshima
authors.affiliation: From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 and.
authors.forename: Tara
authors.initials: T
authors.lastname: Evans-Atkinson
authors.affiliation: Department of Comparative Medicine, University of Washington, Seattle, Washington 98195.
authors.forename: Adeline M
authors.initials: AM
authors.lastname: Hajjar
authors.affiliation: From the Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z3 and rachelf@mail.ubc.ca.
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Fernandez
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000276:immunology / Q000378:metabolism; D000818:Animals; D015153:Blotting, Western; D001886:Bordetella pertussis / Q000276:immunology*; D002478:Cells, Cultured; D005944:Glucosamine / Q000378:metabolism; D057809:HEK293 Cells; D058507:Host Specificity / Q000276:immunology*; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D008050:Lipid A / Q000737:chemistry* / Q000276:immunology* / Q000378:metabolism; D051218:Lymphocyte Antigen 96 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000235:genetics; D011487:Protein Conformation; D015398:Signal Transduction; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D008050:Lipid A; D051218:Lymphocyte Antigen 96; D051197:Toll-Like Receptor 4; D005944:Glucosamine
keywords: Bordetella pertussis; Toll-like receptor 4 (TLR4); bacterial pathogenesis; endotoxin; host-pathogen interaction; infectious disease; innate immunity; lipopolysaccharide (LPS)
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