Objective To investigate the feasibility of producing human IgG1 Fc fragment fused factor IX (FIX-Fc) in the milk of transgenic animals, for an alternative possible solution to the unmet need of FIX-Fc products for hemophilia B treatment. Results Six founder lines of transgenic mice harboring FIX-Fc cassette designed to be expressed specifically in the mammary gland were generated. FIX-Fc protein was secreted into the milk of transgenic mice with preserved biological activity (with the highest value of 6.2 IU/mL), similar to that of the non-fused FIX transgenic milk. RT-PCR and immunofluorescence analysis confirmed that FIX-Fc was specifically expressed in the mammary gland. The blood FIX clotting activities were unchanged, and no apparent health defects were observed in the transgenic mice. Moreover, the stability of FIX protein in milk was increased by the Fc fusion. Conclusions It is feasible to produce biologically functional FIX-Fc in the mammary gland of transgenic mice. Our preliminary results provide a foundation for the potential scale-up production of FIX-Fc in the milk of dairy animals.

中文翻译：

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转基因小鼠乳汁中生物活性人因子IX-Fc融合蛋白的产生

目的 研究在转基因动物的乳汁中生产人 IgG1 Fc 片段融合因子 IX（FIX-Fc）的可行性，为治疗 B 型血友病的 FIX-Fc 产品未满足的需求提供替代可能的解决方案。结果 产生了六个带有 FIX-Fc 盒的转基因小鼠的建立者系，该盒设计为在乳腺中特异性表达。FIX-Fc 蛋白分泌到转基因小鼠的乳汁中，具有保留的生物活性（最高值为 6.2 IU/mL），与非融合 FIX 转基因乳汁相似。RT-PCR 和免疫荧光分析证实 FIX-Fc 在乳腺中特异性表达。血液FIX凝血活性没有变化，在转基因小鼠中没有观察到明显的健康缺陷。而且，Fc 融合增加了 FIX 蛋白在牛奶中的稳定性。结论在转基因小鼠的乳腺中产生具有生物学功能的FIX-Fc是可行的。我们的初步结果为奶牛乳中 FIX-Fc 的潜在放大生产提供了基础。