title: The 2beta2-2beta3 loop of anthrax protective antigen contains a dominant neutralizing epitope.
abstract: Anthrax toxin consists of three proteins, protective antigen (PA), lethal factor, and edema factor. PA is the major component in the current anthrax vaccine, but the antigenic epitopes on it are not well-defined. We generated a pool of toxin-neutralizing anti-PA monoclonal antibodies (MAbs) to analyze the neutralizing epitopes of PA. Nine toxin-neutralizing MAbs obtained were found bound to three different domains of PA respectively, among which three MAbs with the strongest toxin-neutralizing activity recognized the same epitope within domain 2. This epitope was fine mapped to the chymotrypsin-sensitive site, (312)SFFD(315), in the 2beta(2)-2beta(3) loop of PA, using phage-displayed random peptide libraries and mutation analysis. The result demonstrated for the first time that the 2beta(2)-2beta(3) loop, which is involved in the transition of PA oligomers from prepore to pore, contains a dominant neutralizing epitope. This work contributes to the immunological and functional analysis of PA and offers perspective for the development of a new epitope vaccine against anthrax.
authors.affiliation: Department of Applied Molecular Biology, State Key Laboratory of Pathogen and Biosecurity, Beijing Institute of Microbiology and Epidemiology, 20 Dongdajie, Fengtai, Beijing 100071, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhang
authors.forename: Junjie
authors.initials: J
authors.lastname: Xu
authors.forename: Guanlin
authors.initials: G
authors.lastname: Li
authors.forename: Dayong
authors.initials: D
authors.lastname: Dong
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Song
authors.forename: Qiang
authors.initials: Q
authors.lastname: Guo
authors.forename: Jian
authors.initials: J
authors.lastname: Zhao
authors.forename: Ling
authors.initials: L
authors.lastname: Fu
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D001408:Bacillus anthracis / Q000276:immunology; D001427:Bacterial Toxins / Q000737:chemistry* / Q000235:genetics / Q000276:immunology*; D002918:Chymotrypsin / Q000378:metabolism; D016384:Consensus Sequence; D018604:Epitope Mapping; D000939:Epitopes / Q000235:genetics*; D051379:Mice; D017433:Protein Structure, Secondary; D014357:Trypsin / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D000939:Epitopes; C030325:anthrax toxin; D002918:Chymotrypsin; D014357:Trypsin