Purification and characterization of human IL-10/Fc fusion protein expressed in Pichia pastoris

Interleukin (IL)-10 is an anti-inflammatory cytokine that could be potentially applied for clinical therapy. However, its short circulating half-life in the serum limits its clinical applications. In this study, we designed a fusion protein containing human IL-10 and an IgG Fc fragment (hIL-10/Fc), and expressed it in Pichia pastoris. This hIL-10/Fc fusion protein was purified from the culture supernatant using MabSelect affinity chromatography and size-exclusion chromatography. The hIL-10/Fc yield was about 5mg/L in shake flasks, with purity exceeding 95%. In addition, the hIL-10/Fc fusion protein suppressed the phytohemagglutinin-induced IFN-γ production in human peripheral blood mononuclear cells. Pharmacokinetic study also revealed that hIL-10/Fc has a prolonged circulating half-life of about 30h in rats. More importantly, the hIL-10/Fc fusion protein displayed highly specific biological activity, which was slightly higher than that of the commercial recombinant human IL-10 (rhIL-10). Therefore, P. pastoris is useful in the large-scale production of hIL-10/Fc fusion protein for both research and therapeutic applications.     

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。     

Monomeric IgG1 Fc molecules displaying unique Fc receptor interactions that are exploitable to treat inflammation-mediated diseases

The IgG1 Fc is a dimeric protein that mediates important antibody effector functions by interacting with Fcγ receptors (FcγRs) and the neonatal Fc receptor (FcRn). Here, we report the discovery of a monomeric IgG1 Fc (mFc) that bound to FcγRI with very high affinity, but not to FcγRIIIa, in contrast to wild-type (dimeric) Fc. The binding of mFc to FcRn was the same as that of dimeric Fc. To test whether the high-affinity binding to FcγRI can be used for targeting of toxins, a fusion protein of mFc with a 38 kDa Pseudomonas exotoxin A fragment (PE38), was generated. This fusion protein killed FcγRI-positive macrophage-like U937 cells but not FcγRI-negative cells, and mFc or PE38 alone had no killing activity. The lack of binding to FcγRIIIa resulted in the absence of Fc-mediated cytotoxicity of a scFv-mFc fusion protein targeting mesothelin. The pharmacokinetics of mFc in mice was very similar to that of dimeric Fc. The mFc's unique FcγRs binding pattern and related functionality, combined with its small size, monovalency and the preservation of FcRn binding which results in relatively long half-life in vivo, suggests that mFc has great potential as a component of therapeutics targeting inflammation mediated by activated macrophages overexpressing FcγRI and related diseases, including cancer.     

hK-Fc融合蛋白的改良、表达及其生物活性的分析

为了延长人激肽释放酶(hK)的血清半衰期,提高分泌蛋白的产率,制备了重组激肽释放酶-IgG1 Fc融合蛋白(hK'-Fc)。采用PCR扩增hK基因和IgG1的Fc序列,用鼠源信号肽序列替换hK基因原有的信号肽序列,构建改良型融合蛋白hK'-Fc以及天然型融合蛋白hK-Fc的表达载体,转染中国仓鼠卵巢细胞(CHO)细胞,筛选稳定分泌融合蛋白的细胞株,通过Western blotting鉴定信号肽改造效果,利用Protein A+G亲合层析柱纯化融合蛋白,酶学实验检测融合蛋白的体外活性。结果表明:成功构建了pcDNA-hK'-Fc以及pcDNA-hK-Fc重组表达载体;获得了稳定表达融合蛋白的细胞株,产量达11mg/L以上;信号肽改造后融合蛋白的分泌效率提高约5～10倍;融合蛋白能水解其特异性的底物S-2266,具有生物学活性。本研究为进一步探讨融合蛋白的体内半衰期打下了坚实基础,也为研制治疗脑梗塞疗效更好的第二代hK蛋白和其他药用蛋白的改良提供新的线索。     

Pharmacokinetic properties of IgG and various Fc fusion proteins in mice

Fusion to an IgG Fc region is an established strategy to extend the half-life of therapeutic proteins. Most Fc fusion proteins, however, do not achieve the long half-life of IgGs. Based on findings that scFv-Fc fusion proteins exhibit a shorter half-life than the corresponding IgG molecules, we performed a comparative study of different antibody-derived Fc fusion proteins. We could confirm that fusion of single-chain Fv (scFv) and single-chain diabody (scDb) molecules to an Fc region yields in fusion proteins with substantially extended half-lives compared with the single-chain versions. However, even fusion proteins with a size similar to that of IgG, e.g., scDb-Fc, did not have a half-life as long as an IgG molecule. Binding to the neonatal Fc receptor (FcRn) under acidic and neutral conditions was similar for IgG and all Fc fusion proteins. However, we observed differences between IgG and the Fc fusion proteins for dissociation of FcRn-bound proteins induced by shifting from acidic to neutral pH, reflecting the physiological release mechanism, further supporting a contribution of the kinetics of pH-dependent release from FcRn to the pharmacokinetic properties of IgG and Fc fusion proteins.     

Atrial natriuretic peptide-Fc, ANP-Fc, fusion proteins: semisynthesis, in vitro activity and pharmacokinetics in rats

Atrial natriuretic peptide (ANP) may be a useful molecule for the treatment of cardiovascular diseases due to its potent natriuretic effects. In an effort to prolong the short in vivo half-life of ANP, fusions of the peptide to the Fc domain of IgG were generated using a semisynthetic methodology. Synthetic ANP peptides were synthesized with thioesters at either the N- or C-termini of the peptide and subsequently linked to the N-terminus of recombinantly expressed Fc using native chemical ligation. The linker length between the ANP and Fc moieties was varied among 2, 11, or 16 amino acids. In addition, either one ("monomeric") or two ("dimeric") ANP peptides were linked to Fc to study whether this modification had an effect on in vitro activity and/or in vivo half-life. The various constructs were studied for in vitro activity using a cell-based cGMP assay. The ANP-Fc fusion constructs were between 16- and ～375-fold weaker than unconjugated ANP in this assay, and a trend was observed where the most potent conjugates were those with longer linkers and in the dimeric configuration. The pharmacokinetics of several constructs were assessed in rats, and the half-life of the ANP-Fc's were found to be approximately 2 orders of magnitude longer than that of the unconjugated peptide. There was no significant difference in terminal half-life between the monomeric and dimeric constructs (2.8-5.5 h), but a trend was observed where the C(max) of the monomeric constructs was approximately 3-fold higher than that of the dimeric constructs, although the origin of this effect is not understood. These novel ANP-Fc fusion constructs hold promise for future therapeutic application in the treatment of cardiovascular diseases.     

Monomeric IgG1 Fc molecules displaying unique Fc receptor interactions that are exploitable to treat inflammation-mediated diseases

The IgG1 Fc is a dimeric protein that mediates important antibody effector functions by interacting with Fcγ receptors (FcγRs) and the neonatal Fc receptor (FcRn). Here, we report the discovery of a monomeric IgG1 Fc (mFc) that bound to FcγRI with very high affinity, but not to FcγRIIIa, in contrast to wild-type (dimeric) Fc. The binding of mFc to FcRn was the same as that of dimeric Fc. To test whether the high-affinity binding to FcγRI can be used for targeting of toxins, a fusion protein of mFc with a 38 kDa Pseudomonas exotoxin A fragment (PE38), was generated. This fusion protein killed FcγRI-positive macrophage-like U937 cells but not FcγRI-negative cells, and mFc or PE38 alone had no killing activity. The lack of binding to FcγRIIIa resulted in the absence of Fc-mediated cytotoxicity of a scFv-mFc fusion protein targeting mesothelin. The pharmacokinetics of mFc in mice was very similar to that of dimeric Fc. The mFc''s unique FcγRs binding pattern and related functionality, combined with its small size, monovalency and the preservation of FcRn binding which results in relatively long half-life in vivo, suggests that mFc has great potential as a component of therapeutics targeting inflammation mediated by activated macrophages overexpressing FcγRI and related diseases, including cancer.     

Single-chain Variable Fragment Albumin Fusions Bind the Neonatal Fc Receptor (FcRn) in a Species-dependent Manner: IMPLICATIONS FOR IN VIVO HALF-LIFE EVALUATION OF ALBUMIN FUSION THERAPEUTICS*

Albumin has a serum half-life of 3 weeks in humans. This has been utilized to extend the serum persistence of biopharmaceuticals that are fused to albumin. In light of the fact that the neonatal Fc receptor (FcRn) is a key regulator of albumin homeostasis, it is crucial to address how fusion of therapeutics to albumin impacts binding to FcRn. Here, we report on a detailed molecular investigation on how genetic fusion of a short peptide or an single-chain variable fragment (scFv) fragment to human serum albumin (HSA) influences pH-dependent binding to FcRn from mouse, rat, monkey, and human. We have found that fusion to the N- or C-terminal end of HSA only slightly reduces receptor binding, where the most noticeable effect is seen after fusion to the C-terminal end. Furthermore, in contrast to the observed strong binding to human and monkey FcRn, HSA and all HSA fusions bound very poorly to mouse and rat versions of the receptor. Thus, we demonstrate that conventional rodents are limited as preclinical models for analysis of serum half-life of HSA-based biopharmaceuticals. This finding is explained by cross-species differences mainly found within domain III (DIII) of albumin. Our data demonstrate that although fusion, particularly to the C-terminal end, may slightly reduce the affinity for FcRn, HSA is versatile as a carrier of biopharmaceuticals.     

Expression of bovine inhibin beta subunit in Escherichia coli.

1. A DNA fragment encoding the beta subunit of bovine inhibin was amplified using the polymerase chain reaction and was cloned in plasmids pUC8 and pUR291. 2. Cultures of Escherichia coli TG2 harbouring pKDK37, a pUR291-derived recombinant plasmid, produced a novel protein with a molecular weight of 130,000 corresponding to a beta-galactosidase-inhibin beta fusion protein. 3. The fusion protein was purified from inclusion bodies by solubilization in 8 M urea followed by an ion-exchange and gel permeation chromatography. 4. Analysis by immunoblotting and competitive radioimmuno assay revealed that the fusion protein was recognized by a monoclonal antibody raised against a chemically synthesized peptide for amino acid residues from +82 to +114 of the beta subunit of the bovine inhibin thereby confirming its identity.     

Rationale-Based Engineering of a Potent Long-Acting FGF21 Analog for the Treatment of Type 2 Diabetes

Fibroblast growth factor 21 (FGF21) is a promising drug candidate for the treatment of type 2 diabetes. However, the use of wild type native FGF21 is challenging due to several limitations. Among these are its short half-life, its susceptibility to in vivo proteolytic degradation and its propensity to in vitro aggregation. We here describe a rationale-based protein engineering approach to generate a potent long-acting FGF21 analog with improved resistance to proteolysis and aggregation. A recombinant Fc-FGF21 fusion protein was constructed by fusing the Fc domain of human IgG1 to the N-terminus of human mature FGF21 via a linker peptide. The Fc positioned at the N-terminus was determined to be superior to the C-terminus as the N-terminal Fc fusion retained the βKlotho binding affinity and the in vitro and in vivo potency similar to native FGF21. Two specific point mutations were introduced into FGF21. The leucine to arginine substitution at position 98 (L98R) suppressed FGF21 aggregation at high concentrations and elevated temperatures. The proline to glycine replacement at position 171 (P171G) eliminated a site-specific proteolytic cleavage of FGF21 identified in mice and cynomolgus monkeys. The derived Fc-FGF21(RG) molecule demonstrated a significantly improved circulating half-life while maintaining the in vitro activity similar to that of wild type protein. The half-life of Fc-FGF21(RG) was 11 h in mice and 30 h in monkeys as compared to 1-2 h for native FGF21 or Fc-FGF21 wild type. A single administration of Fc-FGF21(RG) in diabetic mice resulted in a sustained reduction in blood glucose levels and body weight gains up to 5-7 days, whereas the efficacy of FGF21 or Fc-FGF21 lasted only for 1 day. In summary, we engineered a potent and efficacious long-acting FGF21 analog with a favorable pharmaceutical property for potential clinical development.     

Design of a modular immunotoxin connected by polyionic adapter peptides

Immunotoxins are genetically engineered fusion proteins of an antibody Fv fragment and a toxin from bacteria or plants, which function as anti-cancer therapeutics. Here, we describe a new generation of immunotoxins in which both proteins do not form a single fusion protein but are coupled specifically via cysteine-containing polyionic fusion peptides. The engineered Pseudomonas exotoxin PE38 was N-terminally fused to the peptide E(8)C. In combination with the disulfide-stabilized Fv fragment of the tumor-specific antibody B3, which was extended by the peptide R(8)CP, the fusion peptides ensured a specific and covalent coupling of the Fv fragment and the toxin. The resulting immunotoxin was as active and as specific as an immunotoxin consisting of a fusion protein of the same antibody fragment connected to the toxin.     

Preparation and characterization of a novel exendin-4 human serum albumin fusion protein expressed in Pichia pastoris.

A novel recombinant exendin-4 human serum albumin fusion protein (rEx-4/HSA) expressed in Pichia pastoris was prepared and characterized. Ex-4 is a 39-amino acid peptide isolated from the salivary gland of the lizard Heloderma suspectum and is thought to be a novel therapeutic agent for type 2 diabetes. But to gain a continued effect, the peptide has to be injected twice a day owing to its short plasma half-life (t(1/2) = 2.4 h). To extend the half-life of Ex-4 molecule in vivo, we designed a genetically engineered Ex-4/HSA fusion protein. Between Ex-4 and HSA, a peptide linker GGGGS was inserted and the fusion protein was expressed in methylotrophic yeast P. pastoris with native HSA secretion signal sequence. The recombinant protein was secreted correctly and was obtained with high purity (typically > 98%) by a three-step purification procedure. cAMP assay demonstrated that the fusion protein had a bioactivity similar to Ex-4 for interaction with GLP-1 receptors in vitro. Results from oral glucose tolerance test indicated that rEx-4/HSA could effectively improve glucose tolerance in diabetic db/db mice. Pharmacokinetics studies in cynomologus monkeys also showed that rEx-4/HSA had a much longer plasma half-life. Therefore, rEx-4/HSA fusion protein could potentially be used as a new recombinant biodrug for type 2 diabetes therapy.     

Cloning, expression, and purification of a highly immunogenic recombinant gonadotropin-releasing hormone (GnRH) chimeric peptide

To design an anti-gonadotropin-releasing hormone (GnRH) vaccine capable of eliciting strong immunogenicity, a gene fragment encoding a chimeric peptide was constructed using polymerase chain reaction and ligated into a novel expression vector for recombinant expression in a T7 RNA polymerase-based expression system. The chimeric peptide called GnRH3-hinge-MVP contained three linear repeats of GnRH (GnRH3), a fragment of the human IgG1 hinge region, and a T-cell epitope of measles virus protein (MVP). The expression plasmid contained the GnRH3-hinge-MVP construct ligated to its fusion partner (AnsB-C) via an unique acid labile Asp-Pro linker. The recombinant fusion protein was expressed in an inclusion body in Escherichia coli under IPTG or lactose induction and the target peptide was easily purified using washing of urea and ethanol precipitation. The target chimeric peptide was isolated from the fusion partner following acid hydrolysis and purified using DEAE-Sephacel chromatography. The purified GnRH3-hinge-MVP was determined to be highly homogeneous by IEF analysis and the N-terminal sequencing. Further, immunization of female mice with the recombinant chimeric peptide resulted in generation of high-titer antibodies specific for GnRH. The results showed that GnRH3-hinge-MVP could be considered as a candidate anti-GnRH vaccine.     

rhEPO-L-Fc融合蛋白的表达、生物活性和初步药动学分析

为了延长人促红细胞生成素(hEPO)体内半衰期以达到更好的药效,制备通过柔性接头相连接的重组人红细胞生成素-IgG1 Fc融合蛋白(rhEPO-L-Fc),并对其生物学活性和体内药动学进行初步研究.利用PCR技术构建rhEPO-L-Fc融合基因,克隆至表达载体pOptiVEC-TOPO ,在二氢叶酸还原酶缺陷型中国仓鼠卵巢细胞(CHO-dhfr-)表达.Protein A亲合层析柱纯化融合蛋白,SDS-PAGE、质谱、Western blotting鉴定表达产物,细胞增殖实验检测融合蛋白的体外活性,动物实验检测融合蛋白的体内活性和半衰期.成功构建pOptiVEC-TOPO -rhEPO-L-Fc重组子,实现了在CHO细胞表达,纯化后的rhEPO-L-Fc融合蛋白经鉴定,其分子量和特异性均与理论值相符,能刺激体外培养的EPO依赖型细胞生长,ED50为2 ng/mL,且明显增加大鼠外周血网织红细胞数,体内消除半衰期达到27 h.rhEPO-L-Fc融合蛋白能延长hEPO体内半衰期,为其临床研究奠定了基础.     

TPO模拟肽与人IgG1Fc融合蛋白在毕赤酵母中的表达及活性鉴定

构建TPO模拟肽与人IgG1Fc融合蛋白的酵母表达体系。利用PCR技术,从重组质粒pET28a-TMPFc中,扩增TPO模拟肽与人IgG1Fc 的DNA片段,连入pPICZαA酵母表达载体,电激法转化毕赤酵母。用MDH和MMH筛选具有正确表型的重组转化子,PCR、蛋白质印迹鉴定融合基因。MTT法鉴定TMPFc对Ba/F3mpl细胞生长的促进作用。构建的重组毕赤酵母实现了TMPFc的分泌表达,表达量占外分泌蛋白质的65%。表达蛋白质的相对分子量约64kD,对Ba/F3mpl生长具有促进作用。TMPFc酵母表达体系表达出可观的二价模拟肽,为二价TMP活性的定量研究奠定基础。     

Inducing specific reactivity against B cells in mice by immunizing with an Fc fusion protein containing self-Igβ

A recombinant chimeric fusion protein, muIgbeta-hugamma4.Fc, composed of the extracellular domain of mouse Igbeta (CD79b) and the CH2-CH3 domains of human IgGgamma4.Fc (hugamma4.Fc), linked via an immunologically inert flexible peptide, was prepared. The fusion protein was evaluated for its ability to induce specific auto-reactive immune response against Igbeta and to modulate B cell activity in Balb/c mice. Upon immunization with muIgbeta-hugamma4.Fc, mice developed immunoglobulin (IgG) against self-Igbeta, which could bind to the cells of a mouse B cell line expressing Igbeta on the cell surface. The proportion of B cells in mononuclear cells in the peripheral blood (PBMC) of treated mice decreased as compared to that of mice immunized with hugamma4.Fc without the Igbeta component. Furthermore, mice immunized against muIgbeta-hugamma4.Fc displayed a reduced antibody response against an irrelevant antigen. The implications of employing the present approach in developing a therapeutic strategy for regulating B cell activity has been discussed.     

Engineered Soluble Monomeric IgG1 CH3 Domain: GENERATION,MECHANISMS OF FUNCTION,AND IMPLICATIONS FOR DESIGN OF BIOLOGICAL THERAPEUTICS*

Most of the therapeutic antibodies approved for clinical use are full-size IgG1 molecules. The interaction of the IgG1 Fc with the neonatal Fc receptor (FcRn) plays a critical role in maintaining their long half-life. We have hypothesized that isolated Fc domains could be engineered to functionally mimic full-size IgG1 (nanoantibodies) but with decreased (10-fold) size. Here, we report for the first time the successful generation of a soluble, monomeric CH3 domain (mCH3). In contrast to the wild-type dimeric CH3, the mCH3 exhibited pH-dependent binding to FcRn similar to that of Fc. The binding free energy of mCH3 to FcRn was higher than that of isolated CH2 but lower than that of Fc. Therefore, CH3 may contribute a larger portion of the free energy of binding to FcRn than CH2. A fusion protein of mCH3 with an engineered antibody domain (m36.4) also bound to FcRn in a pH-dependent fashion and exhibited significantly higher neutralizing activity against HIV-1 than m36.4-Fc fusion proteins. The m36.4-mCH3 fusion protein was monomeric, stable, soluble, and expressed at a high level in Escherichia coli. We also found that engineering an additional disulfide bond in mCH3 remarkably increased its thermal stability, whereas the FcRn binding was not affected. These data suggest that mCH3 could not only help in the exploration of the dual mechanisms of the CH3 contribution to Fc functions (dimerization and FcRn interactions) but could also be used for the development of candidate therapeutics with optimized half-life, enhanced tissue penetration, access to sterically restricted binding sites, and increased therapeutic efficacy.     

Biophysical property and broad anti-HIV activity of albuvirtide, a 3-maleimimidopropionic acid-modified peptide fusion inhibitor

Albuvirtide (ABT) is a 3-maleimimidopropionic acid (MPA)-modified peptide HIV fusion inhibitor that can irreversibly conjugate to serum albumin. Previous studies demonstrated its in vivo long half-life and potent anti-HIV activity. Here, we focused to characterize its biophysical properties and evaluate its antiviral spectrum. In contrast to T20 (Enfuvirtide, Fuzeon), ABT was able to form a stable α-helical conformation with the target sequence and block the fusion-active six-helix bundle (6-HB) formation in a dominant-negative manner. It efficiently inhibited HIV-1 Env-mediated cell membrane fusion and virus entry. A large panel of 42 HIV-1 pseudoviruses with different genotypes were constructed and used for the antiviral evaluation. The results showed that ABT had potent inhibitory activity against the subtypes A, B and C that predominate the worldwide AIDS epidemics, and subtype B', CRF07_BC and CRF01_AE recombinants that are currently circulating in China. Furthermore, ABT was also highly effective against HIV-1 variants resistant to T20. Taken together, our data indicate that the chemically modified peptide ABT can serve as an ideal HIV-1 fusion inhibitor.     

TPO模拟肽与人IgG1 Fc片段的融合表达及其生物学特性研究

依据本室获得的人TPO模拟肽序列,合成了该模拟肽的DNA序列,分别连接至4种不同长度的人IgG1 Fc基因片段的5′端,并克隆至质粒表达载体pET28a( ),转化大肠杆菌BL21（DE3）,筛选获得了4种重组工程菌,其中3种分别高效表达了3种不同长度的融合蛋白,而第4种工程菌未表达,表达的3种融合蛋白的分子量分别约为28kD,12kD和12kD。表达量约占菌体蛋白总量的30％左右,纯化获得了3种TPO模拟肽融合蛋白,3种融合蛋白均有较好的体外活性,维持TPO依赖细胞Ba/F3-mp1生长的EC50分别为：13,10,10nmol/L,用血小板减少症小鼠动物模型,测定了它们的体内活性,3种融合蛋白均有升高血小板和缩短血小板恢复时间的功能,分别比TPO模拟肽活性提高了18,8,8倍,而对白细胞及红细胞无显著影响,分别用3种融合蛋白免疫BALB／c小鼠,均未刺激小鼠产生抗TPO模拟肽抗体,并显示了较好的应用潜力。     

Improving therapeutic properties of protein drugs through alteration of intracellular trafficking pathways

Although intracellular trafficking processes can play a central role in the physiological function of a protein, these same processes can also limit the benefit of the protein when it is taken out of its physiological context and used as a protein drug. Therefore, the properties of certain protein drugs may be improved by manipulating their trafficking pathways to suit their therapeutic function. A detailed consideration of the factors that govern how protein traffic is routed among different cellular destinations can be used to ascertain molecular design criteria for engineering a protein drug so as to alter its trafficking pathway in a beneficial manner. In this review, we summarize studies that have applied this approach to achieve the following three improvements in protein drug function: (1) half-life extension of the Fc fragment of IgG, (2) half-life extension of granulocyte colony-stimulating factor, and (3) increase in cellular association of transferrin.