title: Substitution of the Bordetella pertussis lipid A phosphate groups with glucosamine is required for robust NF-kappaB activation and release of proinflammatory cytokines in cells expressing human but not murine Toll-like receptor 4-MD-2-CD14.
abstract: Bordetella pertussis endotoxin is a key modulator of the host immune response, mainly due to the role of its lipid A moiety in Toll-like receptor 4 (TLR4)-mediated signaling. We have previously demonstrated that the lipid A phosphate groups of B. pertussis BP338 can be substituted with glucosamine in a BvgAS-regulated manner. Here we examined the effect of this lipid A modification on the biological activity of B. pertussis endotoxin. We compared purified endotoxin and heat-killed B. pertussis BP338 whole cells that have modified lipid A phosphate groups to an isogenic mutant lacking this modification with respect to their capacities to induce the release of inflammatory cytokines by human and murine macrophages and to participate in the TLR4-mediated activation of NF-kappaB in transfected HEK-293 cells. We found inactivated B. pertussis cells to be stronger inducers of proinflammatory cytokines in THP-1-derived macrophages when lipid A was modified. Most notably, lack of lipid A modification abolished the ability of purified B. pertussis endotoxin to induce the release of inflammatory cytokines by human THP-1-derived macrophages but led to only slightly reduced inflammatory cytokine levels when stimulating murine (RAW 264.7) macrophages. Accordingly, upon stimulation of HEK-293 cells with inactivated bacteria and purified endotoxin, lack of lipid A modification led to impaired NF-kappaB activation only when human, and not when murine, TLR4-MD-2-CD14 was expressed. We speculate that in B. pertussis, lipid A modification has evolved to benefit the bacteria during human infection by modulating immune defenses rather than to evade innate immune recognition.
authors.affiliation: Department of Microbiology and Immunology, University of British Columbia, Vancouver, British Columbia V6T 1Z3, Canada.
authors.forename: Nico
authors.initials: N
authors.lastname: Marr
authors.forename: Adeline M
authors.initials: AM
authors.lastname: Hajjar
authors.forename: Nita R
authors.initials: NR
authors.lastname: Shah
authors.forename: Alexey
authors.initials: A
authors.lastname: Novikov
authors.forename: Cathy S
authors.initials: CS
authors.lastname: Yam
authors.forename: Martine
authors.initials: M
authors.lastname: Caroff
authors.forename: Rachel C
authors.initials: RC
authors.lastname: Fernandez
mesh_terms: D000818:Animals; D001886:Bordetella pertussis / Q000276:immunology* / Q000472:pathogenicity; D002460:Cell Line; D016207:Cytokines / Q000096:biosynthesis*; D005944:Glucosamine / Q000378:metabolism; D006801:Humans; D008050:Lipid A / Q000737:chemistry* / Q000276:immunology*; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D051218:Lymphocyte Antigen 96 / Q000276:immunology; D008264:Macrophages / Q000276:immunology*; D051379:Mice; D016328:NF-kappa B / Q000276:immunology*; D010710:Phosphates / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000276:immunology
chemical_list: D016207:Cytokines; C495377:LY96 protein, human; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; C411728:Ly96 protein, mouse; D051218:Lymphocyte Antigen 96; D016328:NF-kappa B; D010710:Phosphates; C495345:TLR4 protein, human; C493487:Tlr4 protein, mouse; D051197:Toll-Like Receptor 4; D005944:Glucosamine