title: B-cell epitopes in GroEL of Francisella tularensis.
abstract: The chaperonin protein GroEL, also known as heat shock protein 60 (Hsp60), is a prominent antigen in the human and mouse antibody response to the facultative intracellular bacterium Francisella tularensis (Ft), the causative agent of tularemia. In addition to its presumed cytoplasmic location, FtGroEL has been reported to be a potential component of the bacterial surface and to be released from the bacteria. In the current study, 13 IgG2a and one IgG3 mouse monoclonal antibodies (mAbs) specific for FtGroEL were classified into eleven unique groups based on shared VH-VL germline genes, and seven crossblocking profiles revealing at least three non-overlapping epitope areas in competition ELISA. In a mouse model of respiratory tularemia with the highly pathogenic Ft type A strain SchuS4, the Ab64 and N200 IgG2a mAbs, which block each other's binding to and are sensitive to the same two point mutations in FtGroEL, reduced bacterial burden indicating that they target protective GroEL B-cell epitopes. The Ab64 and N200 epitopes, as well as those of three other mAbs with different crossblocking profiles, Ab53, N3, and N30, were mapped by hydrogen/deuterium exchange-mass spectrometry (DXMS) and visualized on a homology model of FtGroEL. This model was further supported by its experimentally-validated computational docking to the X-ray crystal structures of Ab64 and Ab53 Fabs. The structural analysis and DXMS profiles of the Ab64 and N200 mAbs suggest that their protective effects may be due to induction or stabilization of a conformational change in FtGroEL.
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Zhaohua
authors: Z
authors: Lu
authors: Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Michael J
authors: MJ
authors: Rynkiewicz
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America; Department of Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Guillermo
authors: G
authors: Madico
authors: Department of Medicine, University of California, San Diego, School of Medicine, San Diego, California, United States of America.
authors: Sheng
authors: S
authors: Li
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America; Institute of Molecular Biology, National Chung Hsing University, Taichung, Taiwan.
authors: Chiou-Ying
authors: CY
authors: Yang
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Hillary M
authors: HM
authors: Perkins
authors: Medical Discovery Partners, LLC, Boston, Massachusetts, United States of America.
authors: Seshi R
authors: SR
authors: Sompuram
authors: Medical Discovery Partners, LLC, Boston, Massachusetts, United States of America.
authors: Vani
authors: V
authors: Kodela
authors: Department of Medicine, University of California, San Diego, School of Medicine, San Diego, California, United States of America.
authors: Tong
authors: T
authors: Liu
authors: Department of Medicine, University of California, San Diego, School of Medicine, San Diego, California, United States of America.
authors: Timothy
authors: T
authors: Morris
authors: Department of Medicine, University of California, San Diego, School of Medicine, San Diego, California, United States of America.
authors: Daphne
authors: D
authors: Wang
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Marly I
authors: MI
authors: Roche
authors: Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Barbara A
authors: BA
authors: Seaton
authors: Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts, United States of America.
authors: Jacqueline
authors: J
authors: Sharon
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry / Q000145:classification / Q000276:immunology; D001402:B-Lymphocytes / Q000276:immunology*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D001666:Binding Sites, Antibody; D018834:Chaperonin 60 / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D000939:Epitopes / Q000235:genetics / Q000276:immunology; D005604:Francisella tularensis / Q000276:immunology*; D051379:Mice; D008969:Molecular Sequence Data; D017354:Point Mutation; D011485:Protein Binding; D014406:Tularemia / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D001426:Bacterial Proteins; D018834:Chaperonin 60; D000939:Epitopes