Post-secretion neutralization of transgene-derived effect: soluble erythropoietin receptor/IgG1Fc expressed in liver neutralizes erythropoietin produced in muscle.
BACKGROUND
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.


METHODS
We tested whether the soluble human erythropoietin receptor (EpoR)/IgG(1)Fc could neutralize the rat Epo at the post-secretory level and suppress erythrocytosis.


RESULTS
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(1)Fc significantly inhibited the growth of AS-E2 cells in Epo-containing medium. To test this neutralization effect of EpoR/IgG(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(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(1)Fc injections were significantly lower than in rats that received pCAGGS-EpoR, pCAGGS-IgG(1)Fc, or no injection.


CONCLUSIONS
These results demonstrate that liver-targeted pCAGGS-EpoR/IgG(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.
Division of Clinical Nephrology and Rheumatology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachidori, Niigata 951-8120, Japan. hirokim@med.niigata-u.ac.jp
H
H
Maruyama
M
M
Higuchi
N
N
Higuchi
S
S
Kameda
M
M
Saito
M
M
Sugawa
J
J
Matsuzaki
T
T
Neichi
S
S
Yokoyama
Y
Y
Miyazaki
J
J
Miyazaki
F
F
Gejyo
D000818:Animals; D004921:Erythropoietin / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007141:Immunoglobulin Fc Fragments / Q000235:genetics / Q000378:metabolism; D007074:Immunoglobulin G / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D009132:Muscles / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism; D051381:Rats; D017467:Receptors, Erythropoietin / Q000235:genetics* / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction
D007141:Immunoglobulin Fc Fragments; D007074:Immunoglobulin G; D012333:RNA, Messenger; D017467:Receptors, Erythropoietin; D011993:Recombinant Fusion Proteins; D004921:Erythropoietin