title: Internalizing antibodies to the C-type lectins, L-SIGN and DC-SIGN, inhibit viral glycoprotein binding and deliver antigen to human dendritic cells for the induction of T cell responses.
abstract: The C-type lectin L-SIGN is expressed on liver and lymph node endothelial cells, where it serves as a receptor for a variety of carbohydrate ligands, including ICAM-3, Ebola, and HIV. To consider targeting liver/lymph node-specific ICAM-3-grabbing nonintegrin (L-SIGN) for therapeutic purposes in autoimmunity and infectious disease, we isolated and characterized Fabs that bind strongly to L-SIGN, but to a lesser degree or not at all to dendritic cell-specific ICAM-grabbing nonintegrin (DC-SIGN). Six Fabs with distinct relative affinities and epitope specificities were characterized. The Fabs and those selected for conversion to IgG were tested for their ability to block ligand (HIV gp120, Ebola gp, and ICAM-3) binding. Receptor internalization upon Fab binding was evaluated on primary human liver sinusoidal endothelial cells by flow cytometry and confirmed by confocal microscopy. Although all six Fabs internalized, three Fabs that showed the most complete blocking of HIVgp120 and ICAM-3 binding to L-SIGN also internalized most efficiently. Differences among the Fab panel in the ability to efficiently block Ebola gp compared with HIVgp120 suggested distinct binding sites. As a first step to consider the potential of these Abs for Ab-mediated Ag delivery, we evaluated specific peptide delivery to human dendritic cells. A durable human T cell response was induced when a tetanus toxide epitope embedded into a L-SIGN/DC-SIGN-cross-reactive Ab was targeted to dendritic cells. We believe that the isolated Abs may be useful for selective delivery of Ags to DC-SIGN- or L-SIGN-bearing APCs for the modulation of immune responses and for blocking viral infections.
authors.affiliation: Alexion Antibody Technologies, San Diego, CA 92121, USA.
authors.forename: Naveen
authors.initials: N
authors.lastname: Dakappagari
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Maruyama
authors.forename: Mark
authors.initials: M
authors.lastname: Renshaw
authors.forename: Paul
authors.initials: P
authors.lastname: Tacken
authors.forename: Carl
authors.initials: C
authors.lastname: Figdor
authors.forename: Ruurd
authors.initials: R
authors.lastname: Torensma
authors.forename: Martha A
authors.initials: MA
authors.lastname: Wild
authors.forename: Dayang
authors.initials: D
authors.lastname: Wu
authors.forename: Katherine
authors.initials: K
authors.lastname: Bowdish
authors.forename: Anke
authors.initials: A
authors.lastname: Kretz-Rommel
mesh_terms: D000595:Amino Acid Sequence; D000915:Antibody Affinity; D000938:Antigen-Presenting Cells / Q000276:immunology; D000956:Antigens, Viral / Q000276:immunology; D015153:Blotting, Western; D015815:Cell Adhesion Molecules / Q000276:immunology*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology*; D004705:Endocytosis; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000235:genetics / Q000276:immunology*; D037181:Lectins, C-Type / Q000276:immunology*; D008213:Lymphocyte Activation / Q000276:immunology*; D018613:Microscopy, Confocal; D008969:Molecular Sequence Data; D019151:Peptide Library; D011956:Receptors, Cell Surface / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014764:Viral Proteins / Q000276:immunology; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin
chemical_list: D000956:Antigens, Viral; D015815:Cell Adhesion Molecules; D007140:Immunoglobulin Fab Fragments; D037181:Lectins, C-Type; D019151:Peptide Library; D011956:Receptors, Cell Surface; D014764:Viral Proteins; D000099215:DC-Specific ICAM-3 Grabbing Nonintegrin; C433029:CLEC4M protein, human