Recombinant production of human transferrin for cell culture

描述（由申请人提供）：转铁蛋白通过调节细胞铁的摄取、运输和利用，在控制细胞生长和存活中起着至关重要的作用，因此是用于基于细胞培养生产治疗性蛋白质和疫苗的基本培养基成分。由于担心通过使用动物/人类来源的蛋白质成分传播传染性病原体的风险增加，重组转铁蛋白是生物制药行业首选的替代血浆血清来源的人或牛转铁蛋白。在一期SBIR项目中，我们成功完成了在水稻中表达重组人转铁蛋白的可行性研究，表明重组人转铁蛋白在功能上与天然人转铁蛋白相同，具有可逆结合铁和促进细胞生长的能力。生物活性重组转铁蛋白的表达量高达水稻种子干重的0.88%，比我们的目标表达量（0.1%）高出8倍以上，比商业应用所需的阈值水平（0.01%）高出88倍。在第二阶段的建议中，我们建议将第一期选择的转基因植株进一步发展成稳定的高水平表达转铁蛋白和高产的纯合子转基因品系；对重组转铁蛋白进行全面的组成和生化分析；并将重组转铁蛋白与市产人转铁蛋白进行比较，考察其在杂交瘤细胞增殖和干细胞培养中的等效性。我们预计，作为第二阶段的结果，一种安全和负担得起的重组转铁蛋白将作为人或牛血浆来源的转铁蛋白的替代品，商业化地提供给用于生产疫苗和疗法的细胞培养市场以及用于再生疗法的干细胞研究，其价格将比目前可用的重组转铁蛋白低约20倍。这将使数以百万计的病人和包括儿童和老年人在内的大批健康人口的健康受益。

DESCRIPTION (provided by applicant): Transferrin plays a crucial role in controlling cell growth and survival by regulating cellular iron uptake, transport and utilization, and thus is an essential culture media ingredient used for cell culture-based production of therapeutic proteins and vaccines. With the concerns over the increasing risks of transmission of infectious pathogenic agents through the use of animal/human-derived protein ingredients, recombinant transferrin is preferred to replace the plasma serum-derived human or bovine transferrin by the biopharmaceutical industry. In a Phase I SBIR project, we successfully completed the feasibility study of expressing recombinant human transferrin in rice grain by showing that the recombinant transferrin is functionally equivalent to the native human transferrin in terms of their capacity of binding iron reversibly and promoting cell growth. The expression level of the bioactive recombinant transferrin is up to 0.88% of rice seed dry weight, which is over eight fold higher than our targeted expression level (0.1%) and 88 fold higher than the threshold level (0.01%) required for commercial application. In this phase II proposal, we propose to further develop the transgenic plants selected in Phase I into homozygous transgenic lines with stable high level expression of transferrin and high grain yield; perform comprehensive compositional and biochemical analysis of the recombinant transferrin; and compare the recombinant transferrin to commercial native human transferrin for examining their equivalency in proliferating hybridoma cells and culturing stem cells. We anticipate that as a result of phase II, a safe and affordable recombinant transferrin as an alternative to human or bovine plasma-derived transferrin will be made commercially available to both the cell culture market for the production of vaccines and therapeutics and the stem cell research for regenerative therapies at a price of about 20 times less than that of the currently available recombinant transferrin. This will benefit millions of patients and the health of a large population of healthy people including children and the elderly. PUBLIC HEALTH RELEVANCE: Transferrin plays a crucial role in controlling cell growth and survival by regulating cellular iron uptake, transport and utilization, and thus is an essential culture media ingredient used for cell culture-based production of therapeutic proteins and vaccines. To address the safety concerns over the increasing risks of transmission of infectious pathogenic agents through the use of animal/human-derived protein ingredients, we use rice to produce recombinant human transferrin as a safe and affordable alternative to plasmas-derived human or bovine transferrin for cell-culture-based production of vaccines and therapeutics and the stem cell-based regenerative therapies.