title: Characterisation, cloning and sequencing of a conformation-dependent monoclonal antibody to the alphaIIbbeta3 integrin: interest for use in thrombus detection.
abstract: The detection of newly formed thrombi is of primary importance in clinical medicine. The activated platelet is a potential target for the localization of thrombotic lesions in arteries. The integrin alpha(IIb)beta(3) membrane changes conformation upon activation. A novel anti-alpha(IIb)beta(3) monoclonal antibody (MAb), XIIF9, is described which recognizes an epitope whose expression was enhanced by activation. Radioiodinated XIIF9 bound to a single class of sites on the beta(3) subunit, with 13600 +/- 2000 molecules bound per unstimulated platelet and a K(d) of 34.5 nM. Platelets stimulated with 0.5 U/ml of thrombin bound 66000 +/- 4000 molecules/cell (K(d) = 51.6 nM). Moreover, XIIF9 binding to unstimulated platelets could be increased 4-fold by treatment of the alpha(IIb)beta(3) complex with 5 mM EDTA. Thus, XIIF9 recognized an epitope on the beta(3) subunit whose accessibility was increased upon thrombin activation or EDTA treatment. Sequence analysis of the gene segment encoding the XIIF9 heavy chain revealed interesting motifs shared with cyclic CX6-7C anti-alpha(IIb)beta(3) peptides or with AC7, a published MAb specific for activated alpha(IIb)beta(3). In vivo experiments in atherosclerotic rabbits followed by immunohistological analysis, revealed a specific binding of XIIF9 on platelets engaged in thrombus formation, demonstrating real clinical potential for such MAbs in imaging.
authors.affiliation: Equipe Imagerie Médical EA 1699, Laboratoire de Biophysique, Université de Bordeaux II, 146 Rue Léo-Saignat, 33076 Bordeaux, France. michele.dabadie@u-bordeaux2.fr
authors.forename: M
authors.initials: M
authors.lastname: Dabadie
authors.forename: N
authors.initials: N
authors.lastname: Valli
authors.forename: M J
authors.initials: MJ
authors.lastname: Jacobin
authors.forename: J
authors.initials: J
authors.lastname: Laroche-Traineau
authors.forename: J L
authors.initials: JL
authors.lastname: Barat
authors.forename: D
authors.initials: D
authors.lastname: Ducassou
authors.forename: A T
authors.initials: AT
authors.lastname: Nurden
authors.forename: G
authors.initials: G
authors.lastname: Clofent-Sanchez
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry* / Q000493:pharmacokinetics*; D000915:Antibody Affinity / Q000187:drug effects; D000918:Antibody Specificity; D001665:Binding Sites / Q000276:immunology; D003001:Cloning, Molecular; D004195:Disease Models, Animal; D004492:Edetic Acid / Q000494:pharmacology; D018796:Immunoconjugates / Q000737:chemistry / Q000493:pharmacokinetics*; D007457:Iodine Radioisotopes; D008297:Male; D008969:Molecular Sequence Data; D015539:Platelet Activation / Q000187:drug effects; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000276:immunology*; D011487:Protein Conformation; D011817:Rabbits; D011877:Radionuclide Imaging; D017421:Sequence Analysis; D013917:Thrombin / Q000494:pharmacology; D013927:Thrombosis / Q000000981:diagnostic imaging
chemical_list: D000911:Antibodies, Monoclonal; D018796:Immunoconjugates; D007457:Iodine Radioisotopes; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D004492:Edetic Acid; D013917:Thrombin