title: Protective and immunochemical activities of monoclonal antibodies reactive with the Bacillus anthracis polypeptide capsule.
abstract: Bacillus anthracis is surrounded by a polypeptide capsule composed of poly-gamma-d-glutamic acid (gammaDPGA). In a previous study, we reported that a monoclonal antibody (MAb F26G3) reactive with the capsular polypeptide is protective in a murine model of pulmonary anthrax. The present study examined a library of six MAbs generated from mice immunized with gammaDPGA. Evaluation of MAb binding to the capsule by a capsular "quellung" type reaction showed a striking diversity in capsular effects. Most MAbs produced a rim type reaction that was characterized by a sharp increase followed directly by a decrease in refractive index at the capsular edge. Some MAbs produced a second capsular reaction well beneath the capsular edge, suggesting complexity in capsular architecture. Binding of MAbs to soluble gammaDPGA was assessed by a fluorescence perturbation assay in which a change in the MAb intrinsic fluorescence produced by ligand binding was used as a reporter for antigen-antibody interaction. The MAbs differed considerably in the complexity of the binding curves. MAbs producing rim type capsule reactions typically produced the more complex binding isotherms. Finally, the protective activity of the MAbs was compared in a murine model of pulmonary anthrax. One MAb was markedly less protective than the remaining five MAbs. Characteristics of the more protective MAbs included a relatively high affinity, an immunoglobulin G3 isotype, and a complex binding isotherm in the fluorescence perturbation assay. Given the relatively monotonous structure of gammaDPGA, the results demonstrate a striking diversity in the antigen binding behavior of gammaDPGA antibodies.
authors.affiliation: Department of Microbiology and Immunology/320, University of Nevada School of Medicine, Reno, NV 89557, USA. tkozel@medicine.nevada.edu
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Kozel
authors.forename: Peter
authors.initials: P
authors.lastname: Thorkildson
authors.forename: Suzanne
authors.initials: S
authors.lastname: Brandt
authors.forename: William H
authors.initials: WH
authors.lastname: Welch
authors.forename: Julie A
authors.initials: JA
authors.lastname: Lovchik
authors.forename: David P
authors.initials: DP
authors.lastname: AuCoin
authors.forename: Julpohng
authors.initials: J
authors.lastname: Vilai
authors.forename: C Rick
authors.initials: CR
authors.lastname: Lyons
mesh_terms: D000818:Animals; D000881:Anthrax / Q000276:immunology* / Q000517:prevention & control; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000627:therapeutic use; D000915:Antibody Affinity; D001408:Bacillus anthracis / Q000276:immunology; D016667:Bacterial Capsules / Q000737:chemistry / Q000276:immunology*; D004195:Disease Models, Animal; D018698:Glutamic Acid / Q000276:immunology*; D008171:Lung Diseases / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control; D051379:Mice; D008807:Mice, Inbred BALB C; D010455:Peptides / Q000276:immunology; D016133:Polymerase Chain Reaction
chemical_list: D000911:Antibodies, Monoclonal; D010455:Peptides; D018698:Glutamic Acid