title: Llama single-domain antibodies directed against nonconventional epitopes of tumor-associated carcinoembryonic antigen absent from nonspecific cross-reacting antigen.
abstract: Single-domain antibodies (sdAbs), which occur naturally in camelids, are endowed with many characteristics that make them attractive candidates as building blocks to create new antibody-related therapeutic molecules. In this study, we isolated from an immunized llama several high-affinity sdAbs directed against human carcinoembryonic antigen (CEA), a heavily glycosylated tumor-associated molecule expressed in a variety of cancers. These llama sdAbs bind a different epitope from those defined by current murine mAbs, as shown by binding competition experiments using immunofluorescence and surface plasmon resonance. Flow cytometry analysis shows that they bind strongly to CEA-positive tumor cells but show no cross-reaction toward nonspecific cross-reacting antigen, a highly CEA-related molecule expressed on human granulocytes. When injected into mice xenografted with a human CEA-positive tumor, up to 2% of the injected dose of one of these sdAbs was found in the tumor, despite rapid clearance of this 15 kDa protein, demonstrating its high potential as a targeting moiety. The single-domain nature of these new anti-CEA IgG fragments should facilitate the design of new molecules for immunotherapy or diagnosis of CEA-positive tumors.
authors.affiliation: CNRS, Laboratoire d'Ingénierie des Systèmes Macromoléculaires, Marseille, France.
authors.forename: Ghislaine
authors.initials: G
authors.lastname: Behar
authors.forename: Patrick
authors.initials: P
authors.lastname: Chames
authors.forename: Isabelle
authors.initials: I
authors.lastname: Teulon
authors.forename: Amélie
authors.initials: A
authors.lastname: Cornillon
authors.forename: Faisal
authors.initials: F
authors.lastname: Alshoukr
authors.forename: Françoise
authors.initials: F
authors.lastname: Roquet
authors.forename: Martine
authors.initials: M
authors.lastname: Pugnière
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Teillaud
authors.forename: Anne
authors.initials: A
authors.lastname: Gruaz-Guyon
authors.forename: André
authors.initials: A
authors.lastname: Pèlegrin
authors.forename: Daniel
authors.initials: D
authors.lastname: Baty
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000737:chemistry / Q000276:immunology* / Q000302:isolation & purification / Q000627:therapeutic use*; D000918:Antibody Specificity; D002161:Camelids, New World / Q000276:immunology*; D002272:Carcinoembryonic Antigen / Q000276:immunology*; D045744:Cell Line, Tumor; D003429:Cross Reactions; D000939:Epitopes / Q000276:immunology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007167:Immunotherapy; D008297:Male; D051379:Mice; D008819:Mice, Nude; D008969:Molecular Sequence Data; D009369:Neoplasms / Q000276:immunology / Q000628:therapy*; D016415:Sequence Alignment; D020349:Surface Plasmon Resonance; D023041:Xenograft Model Antitumor Assays
chemical_list: D000906:Antibodies; D002272:Carcinoembryonic Antigen; D000939:Epitopes