title: Efficient tumor targeting by single-domain antibody fragments of camels.
abstract: The variable domain of functional heavy chain antibodies (VHH) devoid of light chains, found in camels, constitute the smallest intact antigen-binding domain fragment. Two camel single-domain fragments, cAb-Lys2 and cAb-Lys3, recognizing an overlapping epitope of lysozyme with a dissociation constant of 2 nM and 65 nM, respectively, and a bivalent cAb-Lys3 were investigated for their ability to target transgenic tumors expressing lysozyme on their membrane. Biodistribution studies revealed that these non-immunogenic monomeric and bivalent camel single-domain antigen binders specifically target lysozyme-expressing tumors and metastatic lesions. The excess of antibody is rapidly eliminated from the blood circulation and no cAb retention was observed in normal organs. The tumor to organ cAb-ratios at 2 and 8 hr were in the (2.1-10.8):1 and (6.2-23.7):1 range, respectively. The degree and specificity of tumor retention is independent of the affinity of the recombinant camel single-domain fragments for their antigen and from their univalent monomeric (15 kDa) or bivalent format (33 kDa). This study demonstrates the successful and specific in vivo targeting of tumors by camel single-domain fragments. It may open perspectives for their future use as tumor-targeting vehicle, due to their small size, soluble behaviour and because they are non-immunogenic and interact with epitopes that are less antigenic for conventional antibodies.
authors.affiliation: Vlaams Interuniversitair Instituut voor Biotechnologie, Vrije Universiteit Brussel, Sint Genesius Rode, Belgium.
authors.forename: Virna
authors.initials: V
authors.lastname: Cortez-Retamozo
authors.forename: Marc
authors.initials: M
authors.lastname: Lauwereys
authors.forename: Gholamreza
authors.initials: G
authors.lastname: Hassanzadeh Gh
authors.forename: Martine
authors.initials: M
authors.lastname: Gobert
authors.forename: Katja
authors.initials: K
authors.lastname: Conrath
authors.forename: Serge
authors.initials: S
authors.lastname: Muyldermans
authors.forename: Patrick
authors.initials: P
authors.lastname: De Baetselier
authors.forename: Hilde
authors.initials: H
authors.lastname: Revets
mesh_terms: D000818:Animals; D000915:Antibody Affinity; D002162:Camelus / Q000276:immunology*; D018827:Carcinoma, Lewis Lung / Q000276:immunology / Q000628:therapy*; D016207:Cytokines / Q000378:metabolism; D000939:Epitopes / Q000276:immunology; D006801:Humans; D007128:Immunoglobulin Fragments / Q000627:therapeutic use*; D007143:Immunoglobulin Heavy Chains / Q000276:immunology; D008213:Lymphocyte Activation; D016399:Lymphoma, T-Cell / Q000276:immunology / Q000628:therapy*; D051379:Mice; D008810:Mice, Inbred C57BL; D016513:Mice, SCID; D009113:Muramidase / Q000276:immunology*; D013601:T-Lymphocytes / Q000378:metabolism; D014407:Tumor Cells, Cultured; D023041:Xenograft Model Antitumor Assays
chemical_list: D016207:Cytokines; D000939:Epitopes; D007128:Immunoglobulin Fragments; D007143:Immunoglobulin Heavy Chains; D009113:Muramidase