Expression and characterisation of recombinant human CD48 and isolation of a human anti‐CD48 monoclonal antibody by phage display

Human CD48, a membrane‐bound, glycosylphosphatidylinositol (GPI)‐linked glycoprotein, is a potential tumour target for the treatment of leukaemias and lymphomas. CD48 is expressed on T‐ and B‐cells, however <5% of CD34⁺ progenitor cells express CD48. A truncated, 45 kDa soluble form of the full length CD48 was expressed in Chinese hamster ovary (CHO) cells, and was shown to consist of a broad range of charge isoforms, with the most abundant isoforms between pI 4.5 and 5.0. The truncated form of CD48 was shown to bind to antibodies raised against native, GPI‐linked CD48 by surface plasmon resonance analysis. A synthetic, human, scFv immunoglobulin gene library was screened against recombinant CD48 by phage display, and an scFv antibody fragment, (designated N2A) was isolated after four rounds of biopanning. N2A was reassembled as a human IgG1 human monoclonal antibody, expressed in CHO cells and the binding of IgG1‐N2A to recombinant CD48 was confirmed by surface plasmon resonance. Flow cytometry studies of IgG1‐N2A binding to Raji cells showed the specificity of N2A for GPI‐linked CD48 was conserved, and presents the potential for IgG1‐N2A as a lead antibody candidate for the treatment of white blood cell malignancies. Copyright © 2005 Society of Chemical Industry