title: Structural Basis for Antibody Recognition of Lipid A: INSIGHTS TO POLYSPECIFICITY TOWARD SINGLE-STRANDED DNA.
abstract: Septic shock is a leading cause of death, and it results from an inflammatory cascade triggered by the presence of microbial products in the blood. Certain LPS from Gram-negative bacteria are very potent inducers and are responsible for a high percentage of septic shock cases. Despite decades of research, mAbs specific for lipid A (the endotoxic principle of LPS) have not been successfully developed into a clinical treatment for sepsis. To understand the molecular basis for the observed inability to translate in vitro specificity for lipid A into clinical potential, the structures of antigen-binding fragments of mAbs S1-15 and A6 have been determined both in complex with lipid A carbohydrate backbone and in the unliganded form. The two antibodies have separate germ line origins that generate two markedly different combining-site pockets that are complementary both in shape and charge to the antigen. mAb A6 binds lipid A through both variable light and heavy chain residues, whereas S1-15 utilizes exclusively the variable heavy chain. Both antibodies bind lipid A such that the GlcN-O6 attachment point for the core oligosaccharide is buried in the combining site, which explains the lack of LPS recognition. Longstanding reports of polyspecificity of anti-lipid A antibodies toward single-stranded DNA combined with observed homology of S1-15 and A6 and the reports of several single-stranded DNA-specific mAbs prompted the determination of the structure of S1-15 in complex with single-stranded DNA fragments, which may provide clues about the genesis of autoimmune diseases such as systemic lupus erythematosus, thyroiditis, and rheumatic autoimmune diseases.
authors.affiliation: From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada.
authors.forename: Omid
authors.initials: O
authors.lastname: Haji-Ghassemi
authors.affiliation: the Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany, and sml@fz-borstel.de.
authors.forename: Sven
authors.initials: S
authors.lastname: Müller-Loennies
authors.affiliation: From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada.
authors.forename: Teresa
authors.initials: T
authors.lastname: Rodriguez
authors.affiliation: the Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany, and.
authors.forename: Lore
authors.initials: L
authors.lastname: Brade
authors.affiliation: the Department of Chemistry, University of Natural Resources and Life Sciences, 1190 Vienna, Austria.
authors.forename: Paul
authors.initials: P
authors.lastname: Kosma
authors.affiliation: the Research Center Borstel, Leibniz-Center for Medicine and Biosciences, Parkallee 22, Borstel D-23845, Germany, and.
authors.forename: Helmut
authors.initials: H
authors.lastname: Brade
authors.affiliation: From the Department of Biochemistry and Microbiology, University of Victoria, Victoria, British Columbia V8P 3P6, Canada, svevans@uvic.ca.
authors.forename: Stephen V
authors.initials: SV
authors.lastname: Evans
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000096:biosynthesis / Q000737:chemistry* / Q000276:immunology; D000918:Antibody Specificity; D001201:Ascites / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology / Q000378:metabolism / Q000473:pathology; D001666:Binding Sites, Antibody; D004277:DNA, Single-Stranded / Q000737:chemistry / Q000276:immunology; D006001:Glycoconjugates / Q000096:biosynthesis / Q000737:chemistry* / Q000276:immunology; D007140:Immunoglobulin Fab Fragments / Q000096:biosynthesis / Q000737:chemistry* / Q000276:immunology; D008050:Lipid A / Q000737:chemistry* / Q000276:immunology; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011485:Protein Binding; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D055672:Static Electricity
chemical_list: D000911:Antibodies, Monoclonal; D004277:DNA, Single-Stranded; D006001:Glycoconjugates; D007140:Immunoglobulin Fab Fragments; D008050:Lipid A
keywords: autoimmunity; lipid A; lipopolysaccharide (LPS); monoclonal antibody; x-ray crystallography