The α-Gal epitope (Galα1,3Galα1,4GlcNAc-R) is responsible for hyperacute rejection (HAR) during transgenic pig-to-non-human primate xenotransplantation. To overcome HAR after xenografts, it is essential for the inactivation of α1,3Galactosyltransferase (GT) gene by the homozygotic knocked out of GT-/- and the isoglobotrihexosylceramide synthase (iGb3s-/-). This study was performed to investigate the generation and characterization of the α1,3GT-MCP/-MCP+iGb3-/- transgenic cells. Ear fibroblast cells from the GT-MCP/-MCP pig were cultured and used to positive control. For iGb3s knock out, the Cas9-GFP-iGb3s vector was transfected into the GT-MCP/-MCP cells. The Cas9-GFP-iGb3s transfected cells were sorted and sequenced for the selection of GT-MCP/-MCP+ iGb3s-/- cells. Among the three sorted cell lines, one transgenic cell line was homozygously deleted 3 bases and 10 bases in each chromosome, respectively. To characterize an expression of α-Gal epitope, a wild type and the transgenic cells were measured by FACS Aria using BS-IB4 lectin antibody. The expression of α-Gal epitope in GT-MCP/-MCP cells (<0.01 %) were significantly down-regulated to the range of wild type (99.4 %) fibroblast cells (p<0.05). To analyze the function of iGb3s, α -Gal epitope expressions were measured for the GT-MCP/-MCP, GT-MCP/-MCP+iGb3s-/+, and GT-MCP/-MCP+iGb3s-/-. The range was 95.8%, 94.2%, and 75.8%, respectively. Interestingly, there was a negative range (16.2%) of α-Gal epitope -/- section in GT-MCP/-MCP+iGb3s-/-, compared to 2.74% of GT-MCP/-MCP+iGb3s-/+ and 1.4% of WT, respectively. Our results demonstrated that iGb3s-/-combined with GT-/- had a function to inhibit α-Gal epitope expression in pig cells. Further studies are needed to evaluate the functions of double gene knock out to minimize a HAR response after xenotransplantation.

The α-Gal epitope (Galα1,3Galα1,4GlcNAc-R) is responsible for hyperacute rejection (HAR) during transgenic pig-to-non-human primate xenotransplantation. There are genes related to the expression of α-Gal epitope such as α1,3Galactosyltransferase gene (GT-/-) and the isoglobotrihexosylceramide synthase (iGb3s-/-). This study was performed to investigate the expression of α-Gal epitope in the skin derived from GT-/- transgenic pig. The skin (7/1000 inches) was obtained by dermatome (Zimmer® Electric Dermatome) from one month old of wildtype (WT) and GT-/- piglets, respectively. The skins were fixed, dehydrated, cleaned, and embedded. To analyze the expression of α-Gal epitope, the paraffin section of WT and GT-/- were stained with BS-IB4 lectin and isoglobotrihexosylceramide synthase antibody. There was a strong BS-IB4 lectin signal in the skin of WT, but not detected in GT-/-. However, the iGb3s positive signals were stained in the skin of both WT and GT-/-. Taken together, it can be postulated that the knocked out of GT gene may not enough to inhibit the expression of α-Gal epitope. Further studies are needed to evaluate the functions of the double knock out of GT and iGb3s on the expression of α-Gal epitope.

Human interferon alpha 2b (hIFNα-2b) is an important immune regulator widely used in clinic, for the treatment of chronic hepatitis, hairy cell leukemia, chronic myelogenous leukemia and multiple myeloma, etc. The clinically used hIFNα-2b is generally produced by E. Coli, which lacks the post-translational O-glycosylation of naturally synthesized protein, and has a short serum half-life. In this study, we report the successful generation of transgenic chickens that produce hIFNα-2b in the egg white using a feline immunodeficiency virus (FIV)-based lentiviral vector. In preliminary in vitro study, the hIFNα-2b gene under the control of CMV promoter expressed as much as 2,650 ng/㎖ in CEF-LNC-hIFNα-2bW cell. A FIV vector packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected underneath the blastoderm of freshly laid chicken eggs (stage X) to produce a hIFNα -2b transgenic chicken. Out of 187 injected eggs, 55 chicks were hatched after 21 days of incubation, and 27 of the G0 hatched chicks expressed the vector-encoded hIFNα-2b gene. The expression of recombinant hIFNα-2b in transgenic chickens constitutes an important step towards low-cost and full biological activity production of this protein drug in bioreactor. This work was supported by the Bio-industry Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and by a grant from the Next-Generation BioGreen 21 Program (No. PJ011178), Rural Development Administration, Republic of Korea.

In the present study, using a MoMLV-based retrovirus vector, we successfully generated a new transgenic chicken line expressing high levels of hEPO. A replication-defective Moloney murine leukemia virus (MoMLV)-based vectors packaged with vesicular stomatitis virus G glycoprotein (VSV-G) was injected beneath the blastoderm of non-incubated chicken embryos (stage X). One rooster was mated to wild-type hens to produce 748 G1 progeny. PCR analysis of blood samples from these progeny revealed that there were seven G1 transgenic offspring, corresponding to a 0.9% germline transmission rate. Subsequently, Southern blot analysis of the genomic DNA from three G1 transgenic chickens was carried out to verify the stable genomic integration and copy number of the transgene in the genome. Quantitative analyses of the blood samples taken from G1 transgenic chickens resulted in 4,150 ～ 10,823 IU/㎖ (34.6 ～ 90.2 ㎍/㎖) of hEPO in the blood. The biological activity of the recombinant hEPO in transgenic chicken serum was comparable to its commercially available counterpart. Red blood cell numbers were more than three-fold higher in the transgenic chickens compared to the non-transgenic chickens. Successful germline transmission of the transgene was also confirmed in G2 transgenic chicks produced from crossing G1 transgenic roosters with non-transgenic hens. We confirmed that 13 transgenic chicks of 45 G2 progeny, corresponding to a 28.9% germline transmission rate. These results will help establish a useful transgenic chicken model system for studies of embryonic development and for efficient production of transgenic chickens as bioreactors. This work was supported by the Bio-industry Technology Development Program, Ministry of Agriculture, Food and Rural Affairs, Republic of Korea, and by a grant from the Next-Generation BioGreen 21 Program (No. PJ011178), Rural Development Administration, Republic of Korea.