Post-secretion neutralization of transgene-derived effect: soluble erythropoietin receptor/IgG sub(1)Fc expressed in liver neutralizes erythropoietin produced in muscle

• Published in: The journal of gene medicine Vol. 6; no. 2; pp. 228 - 237
• Main Authors: Maruyama, H, Higuchi, M, Higuchi, N, Kameda, S, Saito, M, Sugawa, M, Matsuzaki, J, Neichi, T, Yokoyama, S, Miyazaki, Y, Miyazaki, J, Gejyo, F
• Format: Journal Article
• Language: English
• Published: 01.01.2004
• Subjects: erythropoietin receptors
• ISSN: 1099-498X; 1521-2254
• DOI: 10.1002/jgm.485

The regulation of transgene expression is a key issue for the development of safe gene therapy. Various strategies have been used to regulate protein production at the levels of transgene expression, transcription, translation, and secretion. Neutralization following secretion is another important backup system to prevent super-therapeutic levels of a protein from being expressed by gene transfer. We tested whether the soluble human erythropoietin receptor (EpoR)/IgG sub(1)Fc could neutralize the rat Epo at the post-secretory level and suppress erythrocytosis. To assess whether soluble human EpoR could bind rat Epo in vitro, we used the Epo-dependent human leukemic cell line, AS-E2. EpoR/IgG sub(1)Fc significantly inhibited the growth of AS-E2 cells in Epo- containing medium. To test this neutralization effect of EpoR/IgG sub(1)Fc in vivo, we first transferred pCAGGS-Epo into rat muscle by in vivo electroporation, confirmed erythropoiesis for 3 weeks, and then delivered EpoR/IgG sub(1)Fc by liver-targeted gene transfer via tail-vein injection with hydrodynamics-based transfection. Reticulocyte counts and hematocrit levels in rats that received pCAGGS-EpoR/IgG sub(1)Fc injections were significantly lower than in rats that received pCAGGS-EpoR, pCAGGS-IgG sub(1)Fc, or no injection. These results demonstrate that liver-targeted pCAGGS-EpoR/IgG sub(1)Fc transfer by tail-vein injection with hydrodynamics-based transfection is useful for neutralizing Epo delivered by in vivo electroporation. This backup strategy at the level of post-secretion could facilitate the clinical application of gene therapy in the future.