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

Current status, and the developments of hosts and expression systems for the production of recombinant human cytokines

Cytokines consist of peptides, proteins and glycoproteins, which are biological signaling molecules, and boost cell-cell communication in immune reactions to stimulate cellular movements in the place of trauma, inflammation and infection. Recombinant cytokines are designed in such a way that they have generalized immunostimulation action or stimulate specific immune cells when the body encounters immunosuppressive signals from exogenous pathogens or other tumor microenvironments. Recombinant cytokines have improved the treatment processes for numerous diseases. They are also beneficial against novel toxicities that arise due to pharmacologic immunostimulators that lead to an imbalance in the regulation of cytokine. So, the production and use of recombinant human cytokines as therapeutic proteins are significant for medical treatment purposes. For the improved production of recombinant human cytokines, the development of host cells such as bacteria, yeast, fungi, insect, mammal and transgenic plants, and the specific expression systems for individual hosts is necessary. The recent advancements in the field of genetic engineering are beneficial for easy and efficient genetic manipulations for hosts as well as expression cassettes. The use of metabolic engineering and systems biology approaches have tremendous applications in recombinant protein production by generating mathematical models, and analyzing complex biological networks and metabolic pathways via simulations to understand the interconnections between metabolites and genetic behaviors. Further, the bioprocess developments and the optimization of cell culture conditions would enhance recombinant cytokines productivity on large scales.

Immunoengineering approaches for cytokine therapy

Since the discovery of cytokines, much effort has been put forth to achieve therapeutic translation for treatment of various diseases, including cancer and autoimmune diseases. Despite these efforts, very few cytokines have cleared regulatory approval, and those that were approved are not commonly used due to their challenging toxicity profile and/or limited therapeutic efficacy. The main limitation in translation has been that wild-type cytokines have unfavorable pharmacokinetic and pharmacodynamic profiles, either eliciting unwanted systemic side effects or insufficient residence in secondary lymphoid organs. In this review, we address protein-engineering approaches that have been applied to both proinflammatory and anti-inflammatory cytokines to enhance their therapeutic indices, and we highlight diseases in which administration of engineered cytokines is especially relevant.

Metabolic reprogramming of terminally exhausted CD8+ T cells by IL-10 enhances anti-tumor immunity

T cell exhaustion presents one of the major hurdles to cancer immunotherapy. Among exhausted CD8⁺ tumor-infiltrating lymphocytes (TILs), the terminally exhausted subset contributes directly to tumor cell killing owing to its cytotoxic effector function. However, this subset does not respond to immune checkpoint blockades and is difficult to be reinvigorated with restored proliferative capacity. Here, we show that a half-life–extended interleukin (IL)-10/Fc fusion protein directly and potently enhanced expansion and effector function of terminally exhausted CD8⁺ TILs by promoting oxidative phosphorylation (OXPHOS), a process independent of the progenitor exhausted T cells. IL-10/Fc was a safe and highly efficient metabolic intervention that synergized with adoptive T cell transfer immunotherapy, leading to eradication of established solid tumors and durable cures in a majority of treated mice. These findings show that metabolic reprogramming by upregulating mitochondrial pyruvate carrier-dependent OXPHOS can revitalize terminally exhausted T cells and enhance the response to cancer immunotherapy.

Homogeneous production and characterization of recombinant N-GlcNAc-protein in Pichia pastoris

BACKGROUND

Therapeutic glycoproteins have occupied an extremely important position in the market of biopharmaceuticals. N-Glycosylation of protein drugs facilitates them to maintain optimal conformations and affect their structural stabilities, serum half-lives and biological efficiencies. Thus homogeneous N-glycoproteins with defined N-glycans are essential in their application in clinic therapeutics. However, there still remain several obstacles to acquire homogeneous N-glycans, such as the high production costs induced by the universal utilization of mammalian cell expression systems, the non-humanized N-glycan structures and the N-glycosylation microheterogeneities between batches.

RESULTS

In this study, we constructed a Pichia pastoris (Komagataella phaffii) expression system producing truncated N-GlcNAc-modified recombinant proteins through introducing an ENGase isoform (Endo-T) which possesses powerful hydrolytic activities towards high-mannose type N-glycans. The results showed that the location of Endo-T in different subcellular fractions, such as Endoplasmic reticulum (ER), Golgi or cell membrane, affected their hydrolytic efficiencies. When the Endo-T was expressed in Golgi, the secreted IgG1-Fc region was efficiently produced with almost completely truncated N-glycans and the N-GlcNAc modification on the glycosite Asn²⁹⁷ was confirmed via Mass Spectrometry.

CONCLUSION

This strategy develops a simple glycoengineered yeast expression system to produce N-GlcNAc modified proteins, which could be further extended to different N-glycan structures. This system would provide a prospective platform for mass production of increasing novel glycoprotein drugs.

Generation of PK-15 cell lines highly permissive to porcine circovirus 2 infection by transposon-mediated interferon-gamma gene transfer

Porcine circovirus 2 (PCV2)-associated diseases affect the swine industry worldwide. Vaccination is the major tool for the disease control, but the vaccine production is hindered by lower propagation rate of PCV2 in vitro. Previous studies showed that interferons (IFNs) can increase PCV2 yield in PK-15 cells. In the present study, we constructed a Sleepy Beauty (SB) transposon vector expressing porcine IFNg gene fused with the coding sequence for immunoglobulin G Fc domain. After dilution cloning, the transposon and transposase vectors were co-transfected into PK-15 cell clones with higher permissivity to PCV2 infection. Two transgenic PK-15 cell lines, namely PK15-IFNg^Ran and PK15-IFNg^SB which contained randomly integrated transfer vector or SB cassette without selection marker, were screened by PCR analysis. The characterization results demonstrated that the two transgenic cell lines can stably express IFNg-Fc fusion protein with potent antiviral activities. Both viral titration and quantitative PCR analyses showed that the two transgenic cell lines are highly permissive to PCV2 infection with significantly increased viral yields. These results indicate that the two transgenic PK-15 cell lines, PK15-IFNg^SB in particular, can be used for PCV2 vaccine development.

The dual effects of a novel peptibody on angiogenesis inhibition and M2 macrophage polarization on sarcoma

Inhibition of the VEGF/VEGF receptor (VEGFR) and angiopoietin-2 (Ang-2)/TEK receptor tyrosine kinase (Tie-2) pathway is a potential target for tumor angiogenesis. We previously showed that a peptide AS16 which dually inhibits VEGFR/Ang-2 could reduce the tumor growth and decrease the number of microvessels in tumor. However, its short circulating half-life in the serum limits its clinical applications. In this study, as an effort to prolong the short in vivo half-life of AS16, we designed a fusion protein containing peptide AS16 and an IgG Fc fragment. Pharmacokinetic study also revealed that AS16-Fc has a prolonged circulating half-life of about 231 min in rats. We examined the effects of treatment on the tumor vasculature and immune cell populations, tumor growth, in both the MCA-205 and S180 tumor models. We found that AS16-Fc dramatically reduced tumor volume, vascular density and tumor-associated macrophages. Macrophages were identified as potential novel targets following anti-angiogenic therapy, our findings imply a novel role for anti-angiogenic peptide AS16-Fc. These findings indicate that AS16-Fc could be more effective on inhibiting tumor growth angiogenesis and tumor immune microenvironment than that of peptide AS16.

Elimination of N-glycosylation by site mutation further prolongs the half-life of IFN-α/Fc fusion proteins expressed in Pichia pastoris

Background

Interferon (IFN)-α has been commonly used as an antiviral drug worldwide; however, its short half-life in circulation due to its low molecular weight and sensitivity to proteases impacts its efficacy and patient compliance.

Results

In this study, we present an IgG1 Fc fusion strategy to improve the circulation half-life of IFN-α. Three different forms of IgG1 Fc fragments, including the wild type, aglycosylated homodimer and aglycosylated single chain, were each fused with IFN-α and designated as IFN-α/Fc-WT, IFN-α/Fc-MD, and IFN-α/Fc-SC, respectively. The recombinant proteins were expressed in Pichia pastoris and tested using antiviral and pharmacokinetic assays in comparison with the commercial pegylated-IFN-α (PEG-IFN-α). The in vitro study demonstrated that IFN-α/Fc-SC has the highest antiviral activity, while IFN-α/Fc-WT and IFN-α/Fc-MD exhibited antiviral activities comparable to that of PEG-IFN-α. The in vivo pharmacokinetic assay showed that both IFN-α/Fc-WT and IFN-α/Fc-MD have a longer half-life than PEG-IFN-α in SD rats, but IFN-α/Fc-SC has the shortest half-life among them. Importantly, the circulating half-life of 68.3 h for IFN-α/Fc-MD was significantly longer than those of 38.2 h for IFN-α/Fc-WT and 22.2 h for PEG-IFN-α.

Conclusions

The results demonstrate that the elimination of N-glycosylation by mutation of putative N-glycosylation site further prolongs the half-life of the IFN-α/Fc fusion protein and could present an alternative strategy for extending the half-life of low-molecular-weight proteins expressed by P. pastoris for in vivo studies as well as for future clinical applications.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-016-0601-9) contains supplementary material, which is available to authorized users.

Extracellular expression and antiviral activity of a bovine interferon-alpha through codon optimization in Pichia pastoris

Interferons (IFNs) are the primary line of defense against infectious agents. In particular, IFN-α is an important antiviral cytokine and has a wide range of immune-modulating functions. Porcine and human IFN-α have been successfully prepared and play important roles in the prevention and therapy of viral diseases. To date, there has been limited applied research on bovine IFN-α. To achieve high-level expression of recombinant bovine IFN-α (bIFN-α) in Pichia pastoris for large-scale application, the bIFN-α gene was optimized and synthesized on the basis of codon bias of P. pastoris. Optimized bIFN-α (opti-bIFN-α) was successfully expressed in P. pastoris and directly secreted into the culture supernatant. The amount of extracellular soluble opti-bIFN-α was observed to be 200μg/mL in a shake flask. Expression efficiency of opti-bIFN-α was found to be about three times that of wild-type bIFN-α when the expression yield was compared at the same copies of the targeted gene. In addition, both the original cultural supernatant and purified opti-bIFN-α showed strong antiviral activity in MDBK cells (2×10(6)AU/mL and 1×10(7)AU/mg, respectively) and IBRS-2 cells (3×10(5)AU/mL and 1.5×10(6)AU/mg, respectively) against a recombinant vesicular stomatitis virus expressing the green fluorescence protein. In this study, we demonstrated high-level extracellular expression of opti-bIFN-α by P. pastoris. To the best of our knowledge, the opti-bIFN-α yield observed in this study is the highest to be reported to date. Our results demonstrated that the extracellular opti-bIFN-α with strong antiviral activity could be easily prepared and purified at a low cost and that it may be a potential biological therapeutic drug against bovine viral infections.

Expression of a novel chimeric-truncated tPA in Pichia pastoris with improved biochemical properties

Thrombolytic therapy by plasminogen activators (PAs) has been a main goal in the treatment of acute myocardial infarction. Despite improved outcomes of currently available thrombolytic therapies, all these agents have different drawbacks that may result in less than optimal outcomes. In order to make tissue plasminogen activator (tPA) more potent, while being more resistant to plasminogen activator inhibitor-1 (PAI-1) and having a higher affinity to fibrin, a new chimeric-truncated form of tPA (CT tPA) was designed and expressed in Pichia pastoris. This novel variant consists of a finger domain of Desmoteplase, an epidermal growth factor (EGF) domain, a kringle 1 (K1) domain, a kringle 2 (K2) domain, in which the lysine binding site (LBS) was deleted, and a protease domain, where the four amino acids lysine 296, arginine 298, arginine 299, and arginine 304 were substituted by aspartic acid. The chimera CT tPA showed 14-fold increase in its activity in the presence of fibrin compared to the absence of fibrin. Furthermore, CT tPA showed about 10-fold more potency than commercially available full-length tPA (Actylase(®)) and provided 1.2-fold greater affinity to fibrin. A residual activity of only 68 % was observed after incubation of Actylase(®) with PAI-1, however, 91 % activity remained for CT tPA. These promising findings suggest that the novel CT tPA variant might be an acceptable PA with superior characteristics and properties.

Fcγ1 fragment of IgG1 as a powerful affinity tag in recombinant Fc-fusion proteins: immunological, biochemical and therapeutic properties

Affinity tags are vital tools for the production of high-throughput recombinant proteins. Several affinity tags, such as the hexahistidine tag, maltose-binding protein, streptavidin-binding peptide tag, calmodulin-binding peptide, c-Myc tag, glutathione S-transferase and FLAG tag, have been introduced for recombinant protein production. The fragment crystallizable (Fc) domain of the IgG1 antibody is one of the useful affinity tags that can facilitate detection, purification and localization of proteins and can improve the immunogenicity, modulatory effects, physicochemical and pharmaceutical properties of proteins. Fcγ recombinant forms a group of recombinant proteins called Fc-fusion proteins (FFPs). FFPs are widely used in drug discovery, drug delivery, vaccine design and experimental research on receptor-ligand interactions. These fusion proteins have become successful alternatives to monoclonal antibodies for drug developments. In this review, the physicochemical, biochemical, immunological, pharmaceutical and therapeutic properties of recombinant FFPs were discussed as a new generation of bioengineering strategies.

APC targeting enhances immunogenicity of a novel multistage Fc-fusion tuberculosis vaccine in mice

Numerous studies have demonstrated that targeting immunogens to FcγR on antigen-presenting cells (APCs) can selectively uptake and increase cellular immunity in vitro and in vivo. Therefore, the present study was conducted to evaluate immunogenicity of a novel multistage tuberculosis vaccine, a combination of an early and a dormant immunogenic protein, ESAT6 and HspX, fused to Fcγ2a fragment of mouse IgG2a to target all forms of tuberculosis. Codon-optimized genes consisting of ESAT6, a linker, and HspX fused either to mouse Fcγ2a (ESAT6:HspX:mFcγ2a) or 6× His-tag (ESAT6:HspX:His) were synthesized. The resulting proteins were then produced in Pichia pastoris. The fusion proteins were separately emulsified in dimethyldioctadecylammonium bromide(DDA)-trehalose-6,6-dibehenate(TDB) adjuvant, and their immunogenicity with and without bacille Calmette-Guérin (BCG) was assessed in C57BL/6 mice. Th1, Th2, Th17, and T-reg cytokine patterns were evaluated using the ELISA method. Both multistage vaccines induced very strong IL-12 and IFN-γ secretion from splenic cells; the Fc-tagged subunit vaccine induced a more effective Th1 immune response (IFN-γ, 910 pg/mL, and IL-12, 854 pg/mL) with a very low increase in IL-17 (∼0.1 pg/mL) and IL-4 (37 pg/mL) and a mild increase in TGF-β (543 pg/mL) compared to the BCG or ESAT6:HspX:His primed and boosted groups. The production of IFN-γ to ESAT6:HspX:Fcγ2a was very consistent and showed an increasing trend for IL-12 compared to the BCG or ESAT6:HspX:His primed and boosted groups. Fcγ2a used as a delivery vehicle supported the idea of selective uptake, inducing cross-presentation and forming a proper anti-tuberculosis response in context of Th1/Th2 and Th17/T-reg balances, which is important for protection and prevention of damage.

A non-ionic surfactant reduces the induction time and enhances expression levels of bubaline somatotropin in Pichia pastoris

This study describes a simple approach for enhanced secretory expression of bubaline somatotropin (BbST) in the methylotropic yeast Pichia pastoris. A Mut(s) Pichia transformant carrying multi-copy, non-codon optimized BbST cDNA sequence, expressed and secreted the recombinant protein into the culture medium to a level of 25 % of the total proteins in the culture supernatant, after 120 h of induction. Inclusion of polysorbate-80 in the inducing medium resulted in a significant improvement in the BbST expression (up to 45 % of the total culture supernatant proteins) with concomitant reduction in the induction time to 48 h. The amount of BbST obtained was 148 mg/L, which was around fivefold higher than that obtained without the surfactant. BbST was purified to near homogeneity by FPLC on Q-sepharose FF anion-exchange column. Protein authenticity was judged by SDS-PAGE and western blot analyses. A bioassay based on proliferation of Nb2 rat lymphoma cell lines confirmed that the purified, recombinant BbST is biologically active. Use of polysorbate-80 in combination with methanol, during the induction phase, is likely to have general applicability in lowering the induction time and enhancing the secretory expression of other commercially important proteins in Mut(s) strains of P. pastoris.