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

Abstract

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. © 2005 Society of Chemical Industry.