融合蛋白技术在生物医药领域中的应用

在治疗性药物的研发中,效应分子与人免疫球蛋白IgG1 Fc片段或人血清白蛋白形成的融合蛋白疗效不变,但体内半衰期明显延长、药物耐受性增加、副作用减少.在疫苗研发中,抗原分子与毒素分子或Fc形成的融合蛋白是很好的新型疫苗,并能激发细胞免疫.     

Fc融合蛋白在药学领域的研究进展

Fc融合蛋白是指利用基因工程等技术将某种具有生物活性的功能蛋白分子与Fc片段融合而产生的新型重组蛋白,其不仅保留了功能蛋白分子的生物学活性,还具有一些抗体的性质,如通过结合相关Fc受体延长半衰期和引发抗体依赖细胞介导的细胞毒性效应等。对Fc融合蛋白及其在药学领域的研究进展进行了综述。     

治疗性抗体Fc融合蛋白药物研究进展

抗体融合蛋白已成为生物工程治疗药物中最成功的一员.其中的Fc融合蛋白,是一类通过基因工程平台技术将抗体的Fc部分与药物的活性成分融合表达而产生的蛋白.虽然构建Fc融合蛋白的初衷是为了延长其半衰期,但大量研究表明,Fc部分也参与免疫调节过程,引起一些免疫效应.随着生物治疗药物研究的飞速发展,Fc融合蛋白药物研究也取得了很大进展.此文从Fc融合蛋白的设计目的、设计原理、作用机理以及质量控制方面,对治疗性Fc融合蛋白药物的研究进展做一介绍.     

以IgE/FcεRI信号通路为靶标治疗变态反应性疾病研究进展

变态反应性疾病已成为全球性的社会卫生问题,IgE与靶细胞表面高亲和力受体FcεRI结合是I型变态反应的关键步骤。针对IgE/FcεRI信号通路重要靶点进行药物设计是当前治疗变态反应性疾病药物研究的热点,主要集中在以IgE、IgE高亲和力受体FcεRI以及信号通路关键信号分子为靶点的抗体、多肽、疫苗、融合蛋白及小分子化合物等相关药物研究。本文综述了近年来以IgE/FcεRI信号通路为靶点的代表性药物在变态反应性疾病中的作用及其机制。     

一种新型融合蛋白RANKL-Fc的表达和纯化

目的:研究一种新型融合蛋白核转录因子NF-κB受体激动剂配体-免疫球蛋白Fc(RANKLFc)的表达和纯化。方法:通过聚合酶链反应(PCR)将RANKL(140~317)蛋白片段的DNA片段和人源免疫球蛋白Ig G Fc(1~232)片段的DNA片段放大,并把它们同时亚克隆到哺乳动物细胞表达载体(PCDNA3.1)。将构建好的表达载体在哺乳动物CHO细胞进行表达、纯化。通过细胞染色和流式细胞仪分析融合蛋白RANKL-Fc分别与RANKL,Fc RII相互作用。结果和结论:在CHO-K1细胞中成功表达融合蛋白RANKLFc,该蛋白纯化纯度超过90%。融合蛋白RANKL-Fc能分别与RANKL,Fc RII相互作用,结果表明该融合蛋白是以RANKL/RANK通路为靶向的潜在的活性蛋白。     

肿瘤疫苗Astuprotimut-R

黑色素瘤相关抗原-3（MAGE-3）为肿瘤特异性免疫治疗的理想靶分子。葛兰素史克公司研发的重组抗肿瘤融合蛋白疫苗Astuprotimut—R（GSK-249553），系将MAGE-3表位融合到流感嗜血杆菌蛋白D抗原的部分序列中所制得，即MAGE-3重组蛋白。     

真核表达重组小鼠IL-15/Fc融合蛋白的制备和活性鉴定

目的 制备真核表达小鼠白细胞介素15(IL-15)和IgGγ1 Fc段融合蛋白,并探讨其对抗原特异性CD8+T细胞的作用.方法 运用RT-PCR方法,从B6小鼠脾细胞中分离小鼠IL-15和IgG γ1绞链区-CH2-CH3 Fc cDNA.在IL-15 3'端和Fc 5'端引入BamH I酶切位点,将IL-15和Fc直接连接,构建小鼠IL-15/Fe融合蛋白基因,再连接到真核表达质粒载体pcDNA3.1(a+)上,转化CHO-S细胞表达、纯化后,研究其活性.结果 融合蛋白486 bp的编码由162个氨基酸组成,其中含48个信号肽氨基酸的小鼠IL-15前体蛋白和由681 bp编码227个氨基酸的IgGγ1-CH2-CH3功能区构成;表达蛋白在IL-15信号肽引导下能高效分泌到培养液中,有二聚体和三聚体两种天然结构,单体分子量约50 kDa,能特异性的结合IL-15R并抑制抗原诱导的CD8+T细胞的增殖反应.结论 成功构建了小鼠IL-15/Fc融合蛋白真核表达载体,并在CHO-S细胞中得到高效表达.此融合蛋白具有较高的生物学活性,可有效地抑制抗原特异性CD8+细胞的增殖反应.     

rhTNFR:Fc诱导降植烷诱导型关节炎大鼠滑膜细胞凋亡的研究

肿瘤坏死因子α(TNF-α)作为一种效应和调节的细胞因子,在炎症反应、免疫调节等方面重要作用[1]。类风湿性关节炎(RA)的发病机制迄今仍不十分清楚,但TNF-α在RA中起很关键的作用,RA患者关节中的巨噬细胞和淋巴细胞产生大量的TNF-α[2]。重组人肿瘤坏死因子受体融合蛋白(rhTNFR:Fc)是1个二聚体的融合蛋白,包含人75ku肿瘤坏死因子受体(TNFR)(p75)的细胞膜外配基结合部分与人IgG1的Fc片段。rhTNFR:Fc可特异性地与肿瘤坏死因子TNF-α结合,阻断其与细胞表面的TNF受体的结合[3]。对RA等自身免疫性疾病有较好的治疗效果,但其治疗机…     

SARS-CoV病毒结构蛋白的融合蛋白及其高量表达与纯化和用途

本发明中融合蛋白的结构表示为X-Y-Z，其中X选自SARS-CoV病毒结构蛋白S或M或E或N，或它们的任意截短形式；Y是由O～20个氨基酸组成连接部分；Z是Fc及其变体或其它蛋白标签。本发明还提供了在哺乳动物细胞中高量表达和纯化此融合蛋白的方法，使其可进行批量制备或产业化生产。本发明所得的融合蛋白可制备预防SARS-CoV病毒感染的基因工程疫苗，SARS-CoV病毒检测试剂盒，及筛选可抑制S蛋白与其受体ACE2结合的抗SARS-CoV病毒感染的药物。本发明发现SARS-CoV病毒的的S蛋白与ACE2的结合，引起ACE2表达下调，从而导致或加剧急性肺损伤，对S蛋白与ACE2结合的片段进行改造，可增加预防SARS-CoV病毒疫苗的安全性。     

基于中国仓鼠卵巢细胞表达的Fc融合蛋白制备工艺的优化

目的 优化基于中国仓鼠卵巢(Chinese hamster ovary,CHO)细胞表达的Fc融合蛋白制备工艺.方法 对于上游细胞培养工艺,先在摇瓶中分别对培养基配比和流加培养方案进行优化,再将优化工艺放大到生物反应器规模并确认其可行性.对于下游蛋白纯化工艺,分别对A蛋白亲和层析的洗脱条件和阴离子交换层析的平衡条件进行优化.结果 对于上游细胞培养工艺,以种子培养基∶基础培养基(CD OptiCHO)∶基础培养基(CDM4Mab)为2∶1∶1的配比配制培养基,并以3、6和9d补料的流加培养方案进行细胞培养,可获得理想的细胞密度和活率,且成本较低.对于下游蛋白纯化工艺,以pH3.3的洗脱液进行A蛋白亲和层析纯化时,Fc融合蛋白的回收率为94.7％,纯度为98.64％;以pH5.0～pH5.5的平衡液进行阴离子交换层析纯化时,Fc融合蛋白的回收率达到98％以上、纯度达到99％.结论 基于CHO细胞表达的Fc融合蛋白制备工艺的上游细胞培养和下游蛋白纯化工艺得到成功优化,这为此类抗体药物制备工艺的优化提供了思路.     

重组Exendin-4-胰高血糖素样肽1/IgG4(Fc)融合蛋白的表达和活性研究

目的  构建表达长效胰高血糖素样肽1（glucagon-like peptide 1,GLP-1）受体激动剂重组Exendin-4-GLP-1/IgG4(Fc)融合蛋白的质粒载体,并研究该融合蛋白的活性。方法  将编码Exendin-4-GLP-1/IgG4(Fc)的重组基因插入表达载体pOptiVEC™-TOPO^®来构建重组质粒Exendin-4-GLP-1/IgG4(Fc)-pOptiVEC™-TOPO^®。将构建的重组质粒转染CHO/DG44细胞并收获表达产物后,分别用亲和层析法和免疫印迹法对表达产物进行纯化和检测。通过胰岛素释放实验确认重组融合蛋白对INS-1细胞胰岛素分泌的影响,同时在CD1小鼠中研究该融合蛋白对血糖的调节作用。结果  转染重组质粒的CHO/DG44细胞可成功表达Exendin-4-GLP-1/IgG4(Fc)。蛋白质印迹法检测显示,纯化的表达产物的相对分子质量（M_r）与预期相符（重组融合蛋白单体和二聚体的M_r分别约为35 000和70 000）。胰岛素释放实验表明,在葡萄糖浓度恒定的情况下INS-1细胞分泌的胰岛素量随重组融合蛋白浓度的升高而增加。CD1小鼠实验显示,重组融合蛋白对链脲佐菌素诱导的糖尿病小鼠的血糖具有调节作用,Exendin-4-GLP-1/IgG4(Fc)处理的糖尿病小鼠的血糖明显低于对照糖尿病小鼠（F=3194,P＜0.01）。结论  Exendin-4-GLP-1/IgG4(Fc)具有天然GLP-1的活性,可作为GLP-1受体激动剂用于2型糖尿病的治疗。     

A chimeric antibody with dual Fc regions (bisFabFc) prepared by manipulations at the IgG hinge

A new chimeric antibody for therapeutic use in human cancer is described. First the derivative FabFc was prepared by linking Fab' gamma from monoclonal antibody to Fc gamma from human normal IgG1. The bismaleimide linking agent forms a thioether bond with an SH group released by reduction of SS bonds in the hinge of each constituent. It follows that one of the original two SS bonds in the Fc hinge still has both its S atoms free, and this bond is reformed by thiol-disulphide interchange. The lone free SH in the Fc hinge can now be used to join two FabFc molecules through a similar bismaleimide linker to yield bisFabFc. As regards antibody activity against target cells, bisFabFc can be univalent, bivalent, or bispecific. Its juxtaposed dual Fc regions are designed to promote cooperative binding of effectors, and bisFabFc is indeed notably more powerful than its parent FabFc molecules in promoting complement lysis and antibody-dependent cellular cytotoxicity. However it is not possible at present to distinguish the separate contributions of Fc architecture, antibody affinity and other factors towards this improvement. In the present state of development a variety of FabFc against a given neoplasm may be prepared in high yield from mouse IgG1 and IgG2a antibodies, and when convenient dimerized to bisFabFc in any combination of specificities.     

A validated,sensitive electrophoretic method for the detection of activin receptor type II‐Fc fusion proteins in human blood

New therapeutic proteins that trap circulating members of the transforming growth factor (TGF) beta superfamily (activins and growth differentiation factors) show promising effects on erythropoiesis and muscular growth. They are dimeric recombinant fusion proteins composed of the extracellular domain of a human activin receptor (ActRIIA or IIB) linked to the Fc part of human IgG1. Sotatercept (ActRIIA‐Fc) and Luspatercept (a modified ActRIIB‐Fc) in particular are now in phase 2/3 of clinical trials against anemia and included in the prohibited list established by the World Anti‐Doping Agency. To prevent a potential misuse by athletes in the near future, a robust and sensitive method of detection is needed. We validated an approach adapted from an electrophoretic method used for the detection of recombinant erythropoietins that allowed detection of various ActRIIA‐Fc and ActRIIB‐Fc proteins, including variants produced in different cell types, after a single immuno‐extraction step. After separation by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS‐PAGE), an initial testing procedure performed by single‐blotting can indicate the presence of an ActRII‐Fc (indifferently type IIA or IIB). A confirmation performed by double‐blotting using different antibodies for detection allows a more precise identification of the type of ActRII‐Fc (IIA, IIB). Starting from a few hundred microliters of serum or plasma, this method is specific, sensitive, and easy to perform. It could easily be adopted by anti‐doping laboratories.     

Chimeric proteins comprising the constant region of immunoglobulins for treating hemophilia B (WO2005001025)

The application (WO2005001025) details recombinant fusion proteins attached to the constant region of heavy chains of immunoglobulins. They are found to be particularly useful for the treatment of hemostatic disorders, such as hemophilia B. It aims at engineering chimeric proteins comprising of a single molecule of human factor IX (FIX) and the constant region (Fc domain) of one or two heavy chain(s) of human IgG (rFIXFc). cDNA for rFIXFc was generated by a PCR. rFIXFc protein was isolated and purified from stably transfected mammalian cells. The concentration and clotting activity of rFIXFc were assessed in mice, rats, monkeys, and FIX-deficient mice and dogs, after intravenous administration. The half-life of rFIXFc activity is prolonged by three to fourfold, compared with rFIX, when administered intravenously in all animals. The generation of chimeric proteins, comprised of FIX fused to the Fc domain of IgG, extends the clotting activity of the recombinant molecule. rFIXFc represents a promising candidate for the treatment of patients with hemophilia B. The application claims the methods of making recombinant chimeric proteins comprising of one biologically active molecule fused to the Fc region of the heavy chain(s) of immunoglobulins and their use for therapy.     

Chimeric proteins comprising the constant region of immunoglobulins for treating hemophilia B (WO2005001025)

The application (WO2005001025) details recombinant fusion proteins attached to the constant region of heavy chains of immunoglobulins. They are found to be particularly useful for the treatment of hemostatic disorders, such as hemophilia B. It aims at engineering chimeric proteins comprising of a single molecule of human factor IX (FIX) and the constant region (Fc domain) of one or two heavy chain(s) of human IgG (rFIXFc). cDNA for rFIXFc was generated by a PCR. rFIXFc protein was isolated and purified from stably transfected mammalian cells. The concentration and clotting activity of rFIXFc were assessed in mice, rats, monkeys, and FIX-deficient mice and dogs, after intravenous administration. The half-life of rFIXFc activity is prolonged by three to fourfold, compared with rFIX, when administered intravenously in all animals. The generation of chimeric proteins, comprised of FIX fused to the Fc domain of IgG, extends the clotting activity of the recombinant molecule. rFIXFc represents a promising candidate for the treatment of patients with hemophilia B. The application claims the methods of making recombinant chimeric proteins comprising of one biologically active molecule fused to the Fc region of the heavy chain(s) of immunoglobulins and their use for therapy.     

新型冠状病毒受体结合域-Fc融合蛋白表达及小鼠免疫原性

目的  表达制备新型冠状病毒刺突蛋白的受体结合域（receptor binding domain,RBD）-Fc融合蛋白,并评价其在小鼠模型中的免疫原性。方法  将新型冠状病毒RBD与小鼠免疫球蛋白Fc段融合基因在中国仓鼠卵巢细胞中融合表达并制备融合蛋白。将不同剂量的RBD-Fc融合蛋白分别单独或辅以氢氧化铝佐剂免疫小鼠,通过ELISA、假病毒中和试验、酶联免疫斑点试验检测诱导产生的体液和细胞免疫应答。结果  10 μg RBD-Fc融合蛋白辅以氢氧化铝佐剂能有效诱导小鼠产生良好的RBD特异性IgG抗体应答,该抗体可阻断病毒RBD与细胞表面病毒受体的结合,进一步研究表明该重组蛋白还诱导产生了针对原始毒株、Beta变异株和Delta变异株假病毒的中和抗体,中和抗体滴度分别为1 566、336和270。结论  制备的RBD-Fc融合蛋白具有较好的免疫原性,可为开发COVID-19重组蛋白疫苗提供参考。     

Possible role of microbial IgG Fc-binding proteins in rheumatoid arthritis

IgG Fc binding substances (receptors) are widespread among pathogenic microorganisms. The receptors from Staphylococcus aureus, streptococci of group A, C and G as well as Herpes-infected cells bind to the interface between the CH2 and CH3 domains i.e. to His 435, Tyr 436 and possibly also His 433 and/or 310. Most rheumatoid factors (RF) from patients with rheumatoid arthritis show a similar binding pattern. Hence, it has been shown that antibodies to microbial IgG Fc receptors (S. aureus and group A streptococci type M15) and RF are idiotypic-anti-idiotypic antibody "partners" i.e. that RF are the "internal images" of microbial IgG Fc binding proteins. Group A streptococci possessing IgG Fc receptors elicit higher titres of RF when injected in rabbits as compared to group A streptococci without IgG Fc receptors. The streptococcal IgG Fc receptors exhibit a diversity of preferences for subclasses of human IgG, some of them showing allotype preferences. Such allotypes are also recognized by certain RF. IgG RF are able to self-associate thereby forming immune complexes which can activate the complement cascade as well as stimulate release of prostaglandins and (probably) interleukin-1. Since these factors have been assigned an important pathogenic role in rheumatoid arthritis, self-aggregating IgG RF, proposed to be induced by microbial IgG Fc receptors might be an important pathogenic factor in rheumatoid arthritis because rheumatoid arthritis is the only known condition where synthesis of RF takes place in the synovia.     

The comparison of BLyS-binding peptides from phage display library and computer-aided design on BLyS–TACI interaction

BLyS antagonists have become the therapeutic reagents in the treatment of autoimmune disorders. BLyS binding peptides and their Fc fusion proteins may be alternative BLyS antagonists in such application. In this study, the activity of BLyS binding peptide 814 obtained from phage display library and peptide TA designed by computer-aided modeling on the interaction of BLyS–TACI was compared. In addition, to maintain the spatial conformation and stability of the peptides, human IgG1 Fc fragment was fused to peptides 814 and TA to form peptide-Fc fusion proteins, steady and innovative peptibodies. The prokaryotic expression plasmids pET30a-814-Fc and pET30a-TA-Fc for these peptibodies were acquired by genetic engineering, and confirmed by DNA sequencing. After the right plasmids were transformed into Escherichia coli BL21 (DE3), the fusion proteins were expressed and purified by protein A affinity column. As a result of competitive ELISA, peptides 814 and TA at 100 μg/ml displayed 52.2% and 28.6% inhibition on the interaction of TACI-Fc with BLyS respectively. Moreover, 814-Fc and TA-Fc fusion proteins could bind to BLyS in a dosage-dependent manner as TACI-Fc did, and displayed 54.7% and 26.1% inhibition on the interaction of TACI-Fc-Myc with BLyS at 100 μg/ml respectively. So 814-Fc and TA-Fc proteins had the similar bioactivity as the peptides did. Furthermore, compared with TA-Fc, 814-Fc showed two-fold inhibition effect on BLyS binding to TACI, suggesting that 814-Fc could inhibit BLyS bioactivity significantly and might serve as a potential antagonist to treat autoimmune diseases associated with BLyS overexpression.     

类风湿关节炎患者应用重组人Ⅱ型肿瘤坏死因子α受体-抗体融合蛋白联合甲氨蝶呤治疗过程中并发淋巴瘤

1例81岁男性患者因类风湿关节炎病情加重,皮下注射重组人Ⅱ型肿瘤坏死因子α受体-抗体融合蛋白25 mg,2次/周;口服甲氨蝶呤10 mg,1次/周。治疗13个月后发现左下颌下无痛性肿物,切除肿物,病理确诊为腺淋巴瘤。术后停用重组人Ⅱ型肿瘤坏死因子α受体-抗体融合蛋白及甲氨蝶呤,随访8个月淋巴瘤无复发。