Production of recombinant human erythropoietin/Fc fusion protein by genetically manipulated chickens.

We previously reported the production of human erythropoietin (hEpo) using genetically manipulated (GM) chickens. The recombinant hEpo was produced in the serum and egg white of the GM chickens, and the oligosaccharide chain structures of the serum-derived hEpo were more favorable than those of the egg white-derived hEpo. In the present study, a retroviral vector encoding an expression cassette for a fusion protein of hEpo and the Fc region of human immunoglobulin G (hEpo/Fc) was injected into developing chicken embryos, with the aim of recovering the serum-derived hEpo from egg yolk through the yolk accumulation mechanism of maternal antibodies. The GM chickens that hatched stably produced the hEpo/Fc fusion protein not only in their serum and egg white, but also in the egg yolk as expected. Lectin blot analyses revealed that significant amounts of the oligosaccharide chains of hEpo/Fc produced in the serum and eggs of GM chickens terminated with galactose, and that the oligosaccharide chains of the serum- and yolk-derived hEpo/Fc incorporated sialic acid residues. Moreover, biological activity assessment using Epo-dependent cells revealed that the yolk-derived hEpo/Fc exhibited a comparable performance to the serum- and CHO-derived hEpo/Fc. These results indicate that transport of Fc fusion proteins from the blood circulation to the yolk in chickens represents an effective strategy for the production of pharmaceutical glycoproteins using transgenic chicken bioreactors.