CHO expression of a novel human recombinant IgG1 anti-RhD antibody isolated by phage display

Replacement of the hyperimmune anti-Rhesus (Rh) D immunoglobulin, currently used to prevent haemolytic disease of the newborn, by fully recombinant hu man anti-RhD antibodies would solve the current logistic problems associate d with supply and demand. The combination of phage display repertoire cloni ng with precise selection procedures enables isolation of specific genes th at can then be inserted into mammalian expression systems allowing producti on of large quantities of recombinant human proteins. With the aim of selec ting high-affinity anti-RhD antibodies, two human Fab libraries were constr ucted from a hyperimmune donor. Use of a new phage panning procedure involv ing bromelin-treated red blood cells enabled the isolation of two high-affi nity Fab-expressing phage clones, LD-6-3 and LD-6-33, specific for RhD. The se showed a never reaction pattern by recognizing the D variants D-III, D-I Va, D-IVb, D-Va, D-VI types I and II, D-VII, Rh33 and DFR. Full-length immu noglobulin molecules were constructed by cloning the variable regions into expression Vectors containing genomic DNA encoding the immunoglobulin const ant regions. We describe the first, stable, suspension growth-adapted Chine se hamster ovary (CHO) cell line producing a high affinity recombinant huma n IgG1 anti-RhD antibody adapted to pilot-scale production, Evaluation of t he Fc region of this recombinant antibody by either chemiluminescence or an tibody-dependent cell cytotoxicity (ADCC) assays demonstrated macrophage ac tivation and lysis of red blood cells by human lymphocytes. A consistent so urce of recombinant human anti-RhD immunoglobulin produced by CHO cells is expected to meet the stringent safety and regulatory requirements for proph ylactic application.