PRODUCTION AND CHARACTERIZATION OF ANTI-HUMAN INTERFERON-GAMMA RECEPTOR ANTIBODY FRAGMENTS THAT INHIBIT CYTOKINE BINDING TO THE RECEPTOR

Three single-chain antibody fragments that recognize the extracellular human interferon gamma receptor alpha-chain (IFN gamma R), and inhibi t the binding of human IFN gamma, have been produced in Escherichia co li. These fragments are derived from murine anti-receptor monoclonal a ntibodies, and comprise the variable heavy (V-H) domain linked to the variable light (V-L) chain through a 15 amino acid linker [(GGGGS)(3)] . Using surface plasmon resonance technology (BIAcore), the soluble pr oteins were shown to retain a high affinity for recombinant IFN gamma R, and by radioimmunoassay to possess high inhibitory activity towards IFN gamma-binding to human Raji cells. The antibody fragments most li kely recognize epitopes that overlap the cytokine binding site on the receptor surface, Attempts to dissect further the antibodies to isolat ed V-H- and V-L-chains and to synthetic linear and cyclic peptides der ived from the individual complementarity determining regions failed to afford fragments with significant IFN gamma R binding affinity, Never theless, these native-like variable region fragments and petidomimetic s derived from them are of interest in the design of novel IFN gamma R antagonists.