title: Characterization of a unique conformational epitope on free immunoglobulin kappa light chains that is recognized by an antibody with therapeutic potential.
abstract: The murine mAb, K-1-21, recognizes a conformational epitope expressed on free Ig kappa light chains (FκLCs) and also on cell membrane-associated FκLCs found on kappa myeloma cells. This has led to the development of a chimeric version of K-1-21, MDX-1097, which is being assessed in a Phase II clinical trial for the treatment of multiple myeloma. The epitope recognized by K-1-21 is of particular interest, especially in the context that it is not expressed on heavy chain-associated light chains such as in an intact Ig molecule. Using epitope excision techniques we have localized the K-1-21 epitope to a region spanning residues 104-110 of FκLC. This short strand of residues links the variable and constant domains, and is a flexible region that adopts different conformations in FκLC and heavy chain-associated light chain. We tested this region using site-directed mutations and found that the reactivity of K-1-21 for FκLC was markedly reduced. Finally, we applied in silico molecular docking to generate a model that satisfied the experimental data. Given the clinical potential of the Ag, this study may aid the development of next generation compounds that target the membrane form of FκLC expressed on the surface of myeloma plasma cells.
authors.affiliation: School of Medical and Molecular Biosciences, University of Technology Sydney, Ultimo, NSW 2007, Australia. andrew.hutchinson@uts.edu.au
authors.forename: Andrew T
authors.initials: AT
authors.lastname: Hutchinson
authors.forename: Ralitza
authors.initials: R
authors.lastname: Alexova
authors.forename: Vanessa
authors.initials: V
authors.lastname: Bockhorni
authors.forename: Paul A
authors.initials: PA
authors.lastname: Ramsland
authors.forename: Darren R
authors.initials: DR
authors.lastname: Jones
authors.forename: Cameron V
authors.initials: CV
authors.lastname: Jennings
authors.forename: Kevin
authors.initials: K
authors.lastname: Broady
authors.forename: Allen B
authors.initials: AB
authors.lastname: Edmundson
authors.forename: Robert L
authors.initials: RL
authors.lastname: Raison
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids; D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology* / Q000627:therapeutic use*; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology*; D006801:Humans; D007134:Immunoglobulin Switch Region / Q000276:immunology; D007145:Immunoglobulin kappa-Chains / Q000737:chemistry* / Q000276:immunology*; D007700:Kinetics; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D050505:Mutant Proteins / Q000737:chemistry / Q000276:immunology; D009154:Mutation / Q000235:genetics; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000276:immunology; D017386:Sequence Homology, Amino Acid; D014357:Trypsin / Q000378:metabolism
chemical_list: D000596:Amino Acids; D000911:Antibodies, Monoclonal; D000939:Epitopes; D007145:Immunoglobulin kappa-Chains; C000598984:MDX-1097; D050505:Mutant Proteins; D011994:Recombinant Proteins; D014357:Trypsin