Production and purification of recombinant human interleukin-5 from yeast and baculovirus expression systems

Orai inhibition modulates pulmonary ILC2 metabolism and alleviates airway hyperreactivity in murine and humanized models

Ca2+ entry via Ca2+ release-activated Ca2+ (CRAC) channels is a predominant mechanism of intracellular Ca2+ elevation in immune cells. Here we show the immunoregulatory role of CRAC channel components Orai1 and Orai2 in Group 2 innate lymphoid cells (ILC2s), that play crucial roles in the induction of type 2 inflammation. We find that blocking or genetic ablation of Orai1 and Orai2 downregulates ILC2 effector function and cytokine production, consequently ameliorating the development of ILC2-mediated airway inflammation in multiple murine models. Mechanistically, ILC2 metabolic and mitochondrial homeostasis are inhibited and lead to the upregulation of reactive oxygen species production. We confirm our findings in human ILC2s, as blocking Orai1 and Orai2 prevents the development of airway hyperreactivity in humanized mice. Our findings have a broad impact on the basic understanding of Ca2+ signaling in ILC2 biology, providing potential insights into the development of therapies for the treatment of allergic and atopic inflammatory diseases.

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.

CD52-targeted depletion by Alemtuzumab ameliorates allergic airway hyperreactivity and lung inflammation

Allergic asthma is a chronic inflammatory disorder associated with airway hyperreactivity (AHR) whose global prevalence is increasing at an alarming rate. Group 2 innate lymphoid cells (ILC2s) and T helper 2 (T_H2) cells are producers of type 2 cytokines, which may contribute to development of AHR. In this study, we explore the potential of CD52-targeted depletion of type 2 immune cells for treating allergic AHR. Here we show that anti-CD52 therapy can prevent and remarkably reverse established IL-33-induced AHR by reducing airway resistance and alleviating lung inflammation. We further show that CD52 depletion prevents and treats allergic AHR induced by clinically relevant allergens such as Alternaria alternata and house dust mite. Importantly, we leverage various humanized mice models of AHR to show new therapeutic applications for Alemtuzumab, an anti-CD52 depleting antibody that is currently FDA approved for treatment of multiple sclerosis. Our results demonstrate that CD52 depletion is a viable therapeutic option for reduction of pulmonary inflammation, abrogation of eosinophilia, improvement of lung function, and thus treatment of allergic AHR. Taken together, our data suggest that anti-CD52 depleting monoclonal antibodies, such as Alemtuzumab, can serve as viable therapeutic drugs for amelioration of T_H2- and ILC2-dependent AHR.

CD200-CD200R immune checkpoint engagement regulates ILC2 effector function and ameliorates lung inflammation in asthma

The prevalence of asthma and airway hyperreactivity (AHR) is increasing at an alarming rate. Group 2 innate lymphoid cells (ILC2s) are copious producers of type 2 cytokines, which leads to AHR and lung inflammation. Here, we show that mouse ILC2s express CD200 receptor (CD200R) and this expression is inducible. CD200R engagement inhibits activation, proliferation and type 2 cytokine production, indicating an immunoregulatory function for the CD200-CD200R axis on ILC2s. Furthermore, CD200R engagement inhibits both canonical and non-canonical NF-κB signaling pathways in activated ILC2s. Additionally, we demonstrate both preventative and therapeutic approaches utilizing CD200R engagement on ILC2s, which lead to improved airway resistance, dynamic compliance and eosinophilia. These results show CD200R is expressed on human ILC2s, and its engagement ameliorates AHR in humanized mouse models, emphasizing the translational applications for treatment of ILC2-related diseases such as allergic asthma.

ICOS:ICOS-ligand interaction is required for type 2 innate lymphoid cell function, homeostasis, and induction of airway hyperreactivity

Allergic asthma is caused by Th2-cell-type cytokines in response to allergen exposure. Type 2 innate lymphoid cells (ILC2s) are a newly identified subset of immune cells that, along with Th2 cells, contribute to the pathogenesis of asthma by producing copious amounts of IL-5 and IL-13, which cause eosinophilia and airway hyperreactivity (AHR), a cardinal feature of asthma. ILC2s express ICOS, a T cell costimulatory molecule with a currently unknown function. Here we showed that a lack of ICOS on murine ILC2s and blocking the ICOS:ICOS-ligand interaction in human ILC2s reduced AHR and lung inflammation. ILC2s expressed both ICOS and ICOS-ligand, and the ICOS:ICOS-ligand interaction promoted cytokine production and survival in ILC2s through STAT5 signaling. Thus, ICOS:ICOS-ligand signaling pathway is critically involved in ILC2 function and homeostasis.

Development of a baculovirus-based fluorescence resonance energy transfer assay for measuring protein-protein interaction

A new baculovirus-based fluorescence resonance energy transfer (Bv-FRET) assay for measuring multimerization of cell surface molecules in living cells is described. It has been demonstrated that gonadotropin-releasing hormone receptor (GnRH-R) was capable of forming oligomeric complexes in the plasma membrane under normal physiological conditions. The mouse gonadotropin-releasing hormone receptor GnRH-R was used to evaluate the efficiency and potential applications of this assay. Two chimeric constructs of GnRH-R were made, one with green fluorescent protein as a donor fluorophore and the other with enhanced yellow fluorescent protein as an acceptor fluorophore. These chimeric constructs were coexpressed in an insect cell line (BTI Tn5 B1-4) using recombinant baculoviruses. Energy transfer occurred from the excited donor to the acceptor when they were in close proximity. The association of GnRH-R was demonstrated through FRET and the fluorescence observed using a Leica TSC-SPII confocal microscope. FRET was enhanced by the addition of a GnRH agonist but not by an antagonist. The Bv-FRET assay constitutes a highly efficient, reliable and convenient method for measuring protein-protein interaction as the baculovirus expression system is superior to other transfection-based methods. Additionally, the same insect cell line can be used routinely for expressing any recombinant proteins of interest, allowing various combinations of molecules to be tested in a rapid fashion for protein-protein interactions. The assay is a valuable tool not only for the screening of new molecules that interact with known bait molecules, but also for confirming interactions between other known molecules.

Eotaxin-2 and IL-5 cooperate in the lung to regulate IL-13 production and airway eosinophilia and hyperreactivity

BACKGROUND

Eotaxin-2 is a member of the eotaxin subfamily of CC chemokines that display eosinophil-specific, chemotactic properties and has been associated with allergic disorders. However, the contribution of eotaxin-2 to the development of defined pathogenic features of allergic disease remains to be defined.

OBJECTIVE

We sought to determine whether eotaxin-2 was a cofactor with IL-5 for the regulation of pulmonary eosinophilia and to identify the combined role of these molecules in the induction of phenotypic characteristics of allergic lung disease.

METHODS

We instilled recombinant eotaxin-2 into the airways of wild-type mice that had been treated systemically with IL-5 or into IL-5-transgenic mice and characterized pulmonary eosinophil numbers, IL-13 production, and airway hyperreactivity (AHR) to methacholine. Mice deficient in the IL-4 receptor alpha-chain, IL-13, and signal transducers and activators of transcription 6 or mice treated with anti-CCR3 monoclonal antibody were also used.

RESULTS

Eotaxin-2 and IL-5 cooperatively promoted eosinophil accumulation, IL-13 production, and AHR to methacholine. Neither eotaxin-2 nor IL-5 alone induced these features of allergic disease. IL-13 production was critically dependent on eotaxin-2- and IL-5-regulated eosinophilia, which predisposed to the development of AHR. AHR was dependent on IL-13 and signaling through the IL-4R alpha-chain and signal transducers and activators of transcription 6 pathways and the presence of eosinophils in the lung.

CONCLUSION

These investigations demonstrate important cooperativity between eotaxin-2, IL-5, and IL-13 signaling systems and eosinophils for the development of hallmark features of allergic disease of the lung.

The effect of IL-5 and eotaxin expression in the lung on eosinophil trafficking and degranulation and the induction of bronchial hyperreactivity

The mechanisms regulating the selective migration and degranulation of eosinophils in the asthmatic lung and the subsequent development of airways hyperreactivity (AHR) have not been fully delineated. In this investigation, we have employed a novel transgene model to facilitate the dissection of the contributions of IL-5 and/or eotaxin to eosinophil function in the absence of complex tissue signals derived from the allergic lung. Gene transfer of IL-5 and/or eotaxin to the lungs of naive mice induced a pronounced and selective airways eosinophilia, but did not result in eosinophil degranulation or AHR. Airways eosinophilia occurred independently of the induction of a blood eosinophilia, but was markedly augmented by the coexpression of both cytokines and/or by the transient mobilization of eosinophils from the bone marrow by the administration of i.v. IL-5. However, for eosinophil degranulation and AHR to occur, the inhalation of Ag was required in association with IL-5 and eotaxin expression. Investigations in IL-5-deficient mice linked eosinophilia, and not solely IL-5 and eotaxin, with the induction of AHR. Furthermore, eosinophil degranulation and AHR were dependent on CD4+ T cells. Importantly, this investigation shows that IL-5 regulates eosinophilia within the lung as well as in the circulation and also amplifies eotaxin-induced chemotaxis in the airway compartment. Moreover, the interplay between these cytokines, CD4+ T cells, and factors generated by Ag inhalation provides fundamental signals for eosinophil degranulation and the induction of AHR.

Expression and in vitro properties of guinea pig IL-5: comparison to human and murine orthologs

Interleukin-5 (IL-5) is a key mediator of eosinophilic inflammation. The biological role of this cytokine in an allergic airway inflammatory response has been widely demonstrated in guinea pigs, yet the interaction of guinea pig IL-5 (gpIL-5) with its receptor has not been studied. Experiments were performed to quantitate the interaction of gpIL-5 with gpIL-5r and to compare this affinity with that of hIL-5 and mIL-5 and their cognate receptors. The cross-species affinity and agonist efficacy were evaluated to see if gpIL-5r had a restricted species reactivity (as is the case with mIL-5r) or did not distinguish between IL-5 orthologs (similar to hIL-5r). gpIL-5 was cloned using mRNA isolated from cells obtained by bronchoalveolar lavage. Recombinant gpIL-5 was expressed in T. ni insect cells and purified from spent media. Binding assays were performed using insect cells expressing hIL-5ralphabeta or gpIL-5ralphabeta1 as previously described (Cytokine, 12:858-866, 2000) or using B13 cells which express mIL-5r. The agonist potency and efficacy properties of each IL-5 ortholog were evaluated by quantitating the proliferative response of human TF-1 cells and murine B13 cells. gpIL-5 bound with high affinity to recombinant gpIL-5r as demonstrated by displacing [125I]hIL-5 (Ki = 160 pM). gpIL-5 also bound to hIL-5r with high affinity (Ki = 750 pM). hIL-5 and mIL-5 showed similar, high-affinity binding profiles to both gpIL-5r and hIL-5r. In contrast, gpIL-5 and hIL-5 did not bind to the mIL-5r as demonstrated by an inability to displace [125I]mIL-5, even at 1000-fold molar excess. These differences in affinity for IL-5r orthologs correlated with bioassay results: human TF-1 cells showed roughly comparable proliferative responses to guinea pig, human and murine IL-5 whereas murine B13 cells showed a strong preference for murine over guinea pig and human IL-5 (EC50 = 1.9, 2200 and 720 pM, respectively). Recombinant gpIL-5 binds to the gpIL-5r with high affinity, similar to that seen with the human ligand-receptor pair. gpIL-5r and hIL-5r do not distinguish between the three IL-5 orthologs whereas mIL-5r has restricted specificity for its cognate ligand.

Comparison of biological activities of natural and recombinant chicken interferon-gamma

In recent years, chicken interferon-gamma (ChIFN-gamma) has been identified and cloned from a chicken T cell line. In this study, recombinant ChIFN-gammma produced in the baculovirus and prokaryotic (Escherichia coli) expression systems were characterized and their activity was compared to that of naturally ChIFN-gamma produced by mitogen-activated splenic T cells. The baculovirus-derived ChIFN-gamma protein (Bac-ChIFN-gamma) proved to have physiochemical properties and biological activities similar to those of natural ChIFN-gamma. Indeed, Bac-ChIFN-gamma was able to inhibit the replication of cytolytic viruses in chicken embryo fibroblasts and to activate macrophages, as was determined by nitric oxide production. Levels ranging between 100 and 300 microg/ml of BacChIFN-gamma could be obtained in the supernatants of infected insect cells. On the other hand, yields of the E. coli produced ChIFN-gamma rarely exceeded 100 microg/ml after purification steps and although it was also able to activate the HD11 macrophage cell line in a specific manner, no anti-viral activity could be demonstrated. Therefore, the baculovirus expression system is an appropriate system for the high-level expression of biologically active ChIFN-gamma and will allow further studies of the immunomodulatory and therapeutic effects of this cytokine in vivo.

Preparation of recombinant rat interleukin-5 by baculovirus expression system and analysis of its biological activities

Rat interleukin-5 (IL-5) cDNA was subcloned from peritoneal cells collected 4 h after intraperitoneal injection of Ascaris suum antigen solution into the immunized rats. Cysteine proteinase-deleted (CPd) rat IL-5 recombinant virus was constructed by inserting rat IL-5 cDNA into CPd virus having a deletion in the cysteine proteinase gene of the silkworm Bombyx mori nuclear polyhedrosis virus. On infection with the CPd rat IL-5 recombinant virus, the silkworm B. mori larvae produced rat IL-5 as a dimeric form in hemolymph. Recombinant rat IL-5 was purified more than 95.5% by anion-exchange chromatography and hydrophobic chromatography. The purified recombinant rat IL-5 promoted the proliferation of T88-M cells in a concentration-dependent manner, and its effect was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. When bone marrow cells from normal rats were incubated with recombinant rat IL-5 in medium containing methylcellulose, the colony formation by eosinophilic cells was induced. Furthermore, when rat peritoneal eosinophils were incubated with recombinant rat IL-5, the spontaneous decrease in the eosinophil viability was inhibited in time- and concentration-dependent manners. In addition, the recombinant rat IL-5-induced eosinophil survival was inhibited by an anti-murine IL-5 neutralizing polyclonal antibody. These findings suggest that rat IL-5 acts as B-cell growth factor II (BCGF-II), eosinophil differentiation factor (EDF), and eosinophil survival-enhancing factor.

The cytokine interleukin-5 (IL-5) effects cotransport of its receptor subunits to the nucleus in vitro

Interleukin (IL)-5 is central in regulating eosinophilia in allergic disease and parasitic infections. We have recently shown that human (h) IL-5 both possesses a functional nuclear localization signal capable of targeting a heterologous protein to the nucleus and localises to the nucleus of intact receptor-expressing cells. In this study, the extracellular domains of the hIL-5 alpha- and beta-receptor subunits were expressed in baculovirus, fluorescently labelled and assayed for nuclear targeting in vitro in the absence and presence of IL-5. The beta-subunit, which lacks IL-5 binding activity, only accumulated in the nucleus in the presence of both the hIL-5 binding alpha-subunit and hIL-5. The IL-5-binding alpha-subunit showed similar results. IL-5 thus effected nuclear transport of its alpha- and beta-receptor subunits apparently through a 'piggy back' mechanism, raising the possibility that IL-5's nuclear signalling role may be to cotarget its receptor subunits to the nucleus. This is the first demonstration of nuclear protein piggy back transport in vitro.

A functional bipartite nuclear localisation signal in the cytokine interleukin-5

Interleukin (IL)-5 is central in regulating eosinophilia in allergic disease and parasitic infections. We have identified a bipartite nuclear localisation signal (NLS) within amino acids 95-111 of human IL-5 (hIL-5), also present in mouse IL-5 (mIL-5). hIL-5 and mIL-5 were labelled fluorescently, and nuclear uptake subsequent to membrane binding and internalisation by intact receptor expressing cells visualised and quantified using confocal laser scanning microscopy. hIL-5 and mIL-5 were shown to be transported to the nucleus in in vivo and in vitro nuclear protein import assays. The hIL-5 NLS was able to target a heterologous protein to the nucleus both in vivo and in vitro. Mutations within the proximal arm of the NLS abrogated nuclear targeting activity, confirming its bipartite nature. The results imply a nuclear signalling role for IL-5 additional to pathways linked to the membrane receptor system.

Eosinophilia, parasite burden and lung damage in Toxocara canis infection in C57Bl/6 mice genetically deficient in IL-5

C57Bl/6 mice genetically deficient in interleukin (IL)-5 (IL-5-/-) and mice with the normal IL-5 gene (IL-5+/+) were infected with embryonated eggs of Toxocara canis. IL-5+/+ mice developed a marked eosinophilia in their peripheral bloods and bone marrows after infection. In contrast, the number of eosinophils at these sites actually decreased during the acute phase of infection in IL-5-/- mice. A smaller number of eosinophils infiltrated the lung, liver, heart and skeletal muscle of infected IL-5-/- mice than those of infected IL-5+/+ mice. Eosinophils were not produced in cultures of bone marrow cells from either IL-5+/+ or IL-5-/- mice which were stimulated with excretory secretory antigen of T. canis larvae. The capacity of cells from the bone marrow to differentiate into eosinophils when stimulated in vitro with recombinant murine IL-5 was the same whether the cells were from IL-5+/+ or IL-5-/- mice. Taken together, these results show that an IL-5-like molecule is not produced by the T. canis larvae and that IL-5 produced by host cells is solely responsible for the eosinophilia in mice infected with this nematode. The number and location of T. canis larvae were not altered in the absence of IL-5. In contrast, lung damage in infected IL-5-/- mice was less extensive than that in infected IL-5+/+ mice, although structures resembling Charcot-Leyden crystals were seen in the lungs of both IL-5+/+ and IL-5-/- mice. These results suggest that eosinophils play a role in the pathology in mice infected with T. canis.

Relationship between interleukin-5 and eotaxin in regulating blood and tissue eosinophilia in mice

The mechanism of cooperation between IL-5 and eotaxin for the selective accumulation of eosinophils at sites of allergic inflammation is unknown. In this investigation we have used IL-5 deficient mice to define the relationship between this cytokine and eotaxin in the regulation of blood eosinophilia and eosinophil homing and tissue accumulation. Both IL-5 and eotaxin could independently induce a rapid and pronounced blood eosinophilia in wild type mice when administered systemically. In contrast, only eotaxin induced a pronounced blood eosinophilia in IL-5 deficient mice. The eosinophilic response induced by intravenous eotaxin in wild type mice did not correlate with a significant reduction in the level of bone marrow eosinophils, whereas intravenous IL-5 resulted in depletion of this store. These results suggest the existence of two mechanisms by which eosinophils can be rapidly mobilized in response to intravenous eosinophil chemoattractants; first, mobilization of an IL-5 dependent bone marrow pool, and second, an eotaxin-induced sequestration of eosinophils from tissues into the blood. Subcutaneous injection of eotaxin induced a local tissue eosinophilia in wild type mice but not in IL-5 deficient mice. Furthermore, tissue eosinophilia in wild type mice, but not in IL-5 deficient mice, was enhanced by adoptive transfer of eosinophils or the administration of intravenous IL-5. However, pretreatment of IL-5 deficient mice with intraperitoneal IL-5 for 72 h restored eosinophil homing and tissue accumulation in response to subcutaneous eotaxin. We propose that eotaxin secreted from inflamed tissue may play an important role in initiating both blood and tissue eosinophilia in the early phases of allergic inflammation. Furthermore, IL-5 is not only essential for mobilizing eosinophils from the bone marrow during allergic inflammation, but also plays a critical role in regulating eosinophil homing and migration into tissues in response to eotaxin and possibly other specific chemotactic stimuli.

Lysosomal protective protein/cathepsin A. Role of the "linker" domain in catalytic activation

Lysosomal protective protein/cathepsin A is a serine carboxypeptidase that forms a complex with beta-galactosidase and neuraminidase. The enzyme is synthesized as a 54-kDa precursor/zymogen and processed into a catalytically active 32- and 20-kDa two-chain form. We have expressed in baculovirus-infected insect cells the human one-chain precursor as well as the two separate subunits in order to establish the mode of catalytic activation of the zymogen and the assembly and activation of the two subunits. Infected insect cells synthesize large quantities of the exogenous proteins, which are glycosylated and secreted but not processed. Co-expression of the two subunits results in their assembly into a two-chain form of 34- and 20-kDa with negligible enzymatic activity. Limited proteolysis with trypsin of the 54-kDa precursor and the reconstituted 34- and 20-kDa form gives rise to a fully active 32- and 20-kDa product. These results enabled us to map the sites of proteolytic cleavage needed for full activation of the cathepsin A zymogen. They further indicate that the 34- and 20-kDa form is a transient processing intermediate that is converted into a mature and active enzyme by removal of a 2-kDa "linker" peptide from the COOH terminus of the 34-kDa subunit.

Production of lymphotoxin (LT alpha) and a soluble dimeric form of its receptor using the baculovirus expression system

Human LT alpha and a fusion protein (p60:Fc) comprised of the extracellular domain of the 60 kDa TNF receptor (TNFR60) fused to the Fc portion of human IgG1 were produced in insect cells infected with recombinant baculoviruses. The p60:Fc fusion produced in insect cells accumulates in culture supernatants to levels > 2 mg/l. Purified p60:Fc binds human TNF and LT alpha with high affinity (200-600 pM) and neutralizes TNF cytolytic activity at equimolar stoichiometric concentration. The data show that p60:Fc is an effective ligand-precipitating reagent which recognizes recombinant LT alpha produced in mammalian or insect cells and naturally occurring LT alpha produced in T cells. The levels of human LT alpha produced in baculovirus-infected insect cells is estimated to be approximately 20 mg/l. Insect cell-derived human LT alpha is biologically active in an L929 cytotoxicity assay and is efficiently neutralized by p60:Fc. These data demonstrate that the baculovirus system is useful for overexpressing biologically active LT alpha and p60:Fc and therefore, may be applicable to other oligomeric cytokines and soluble dimeric cytokine receptors.

Expression, purification and crystallization of fully active, glycosylated human interleukin-5

Recombinant human interleukin-5 (hIL-5) has been expressed at high levels and produced in large quantities in baculovirus infected Sf9 insect cells. The glycosylated protein was purified using immuno-affinity chromatography and gel filtration. Purified hIL-5 has been crystallized using standard vapour diffusion techniques with PEG as a coprecipitant. The crystals belong to the C2 space group and diffract to 2 A.

Antibody production in the baculovirus expression system

The proven ability of insect cells to produce murine and human antibodies renders the baculovirus system amenable to the synthesis of both naturally occurring antibodies and designed mutants. Study of these antibodies should provide a basis for rational antibody design useful in human therapy.