Zinc mediated dimer of human interferon-alpha 2b revealed by X-ray crystallography

Simultaneous Purification of Human Interferon Alpha-2b and Serum Albumin Using Bioprivileged Fluorinated Ionic Liquid-Based Aqueous Biphasic Systems

Interferon alpha-2b (IFN-α2b) is an essential cytokine widely used in the treatment of chronic hepatitis C and hairy cell leukemia, and serum albumin is the most abundant plasma protein with numerous physiological functions. Effective single-step aqueous biphasic system (ABS) extraction for the simultaneous purification of IFN-α2b and BSA (serum albumin protein) was developed in this work. Effects of the ionic liquid (IL)-based ABS functionalization, fluorinated ILs (FILs; [C​2C​1Im][C​4F​9SO​3] and [N​1112(OH)][C​4F​9SO​3]) vs. mere fluoro-containing IL ([C​4C​1Im][CF​3SO​3]), in combination with sucrose or [N​1112(OH)][H​2PO​4] (well-known globular protein stabilizers), or high-charge-density salt K​3PO​4 were investigated. The effects of phase pH, phase water content (%wt), phase composition (%wt), and phase volume ratio were investigated. The phase pH was found to have a significant effect on IFN-α2b and BSA partition. Experimental results show that simultaneous single-step purification was achieved with a high yield (extraction efficiency up to 100%) for both proteins and a purification factor of IFN-α2b high in the enriched IFN-α2b phase (up to 23.22) and low in the BSA-enriched phase (down to 0.00). SDS-PAGE analysis confirmed the purity of both recovered proteins. The stability and structure of IFN-α2b and BSA were preserved or even improved (FIL-rich phase) during the purification step, as evaluated by CD spectroscopy and DSC. Binding studies of IFN-α2b and BSA with the ABS phase-forming components were assessed by MST, showing the strong interaction between FILs aggregates and both proteins. In view of their biocompatibility, customizable properties, and selectivity, FIL-based ABSs are suggested as an improved purification step that could facilitate the development of biologics.

Targeted mutations in IFNα2 improve its antiviral activity against various viruses

During viral infections, type I interferons (IFN) are induced and play a key role in counteracting initial viral spread. Twelve different human IFNα subtypes exist that bind the same receptor; however, they elicit unique host responses and display distinct potencies of antiviral activities. Our previous studies on human immunodeficiency virus (HIV) and hepatitis B virus (HBV) demonstrated that the clinically used IFNα2 is not the most effective one among the IFNα subtypes. By sequence modeling, we identified a region in helix B with mainly conserved residues at the outside facing IFNAR1, but variable residues at the inside facing the core of IFNα, potentially representing a putative tunable anchor to tune pleiotropic IFN responses. Using site-directed mutagenesis, various mutations were introduced into the IFNα2b backbone targeting sites which are important for binding to IFNAR1 and IFNAR2, the putative tunable anchor, or outside these three regions. Selected mutations were based on sequence differences to high antiviral subtypes IFNα6 and IFNα14. Treatment assays against HBV and HIV identified several critical residues for the antiviral activity of IFNα mainly in the IFNAR1 binding region. Combined mutations of the IFNα2 IFNAR1/2 binding sites or the IFNAR1 binding region plus the putative tunable anchor by those of IFNα14 further augmented activation of different downstream signaling cascades providing a molecular correlate for the enhanced antiviral activity. We describe here important functional residues within IFNα subtype molecules, which enabled us to design novel and innovative drugs that may have the potential to be used in clinical trials against a variety of different viral infections.IMPORTANCEThe potency of interferon (IFN)α to restrict viruses was already discovered in 1957. However, until today, only IFNα2 out of the 12 distinct human IFNα subtypes has been therapeutically used against chronic viral infections. There is convincing evidence that other IFNα subtypes are far more efficient than IFNα2 against many viruses. In order to identify critical antiviral residues within the IFNα subtype sequence, we designed hybrid molecules based on the IFNα2 backbone with individual sequence motifs from the more potent subtypes IFNα6 and IFNα14. In different antiviral assays with HIV or HBV, residues binding to IFNAR1 as well as combinations of residues in the IFNAR1 binding region, the putative tunable anchor, and residues outside these regions were identified to be crucial for the antiviral activity of IFNα. Thus, we designed artificial IFNα molecules, based on the clinically approved IFNα2 backbone, but with highly improved antiviral activity against several viruses.

Hepatitis B Virus Epsilon (ε) RNA Element: Dynamic Regulator of Viral Replication and Attractive Therapeutic Target

Hepatitis B virus (HBV) chronically infects millions of people worldwide, which underscores the importance of discovering and designing novel anti-HBV therapeutics to complement current treatment strategies. An underexploited but attractive therapeutic target is ε, a cis-acting regulatory stem-loop RNA situated within the HBV pregenomic RNA (pgRNA). The binding of ε to the viral polymerase protein (P) is pivotal, as it triggers the packaging of pgRNA and P, as well as the reverse transcription of the viral genome. Consequently, small molecules capable of disrupting this interaction hold the potential to inhibit the early stages of HBV replication. The rational design of such ligands necessitates high-resolution structural information for the ε-P complex or its individual components. While these data are currently unavailable for P, our recent structural elucidation of ε through solution nuclear magnetic resonance spectroscopy marks a significant advancement in this area. In this review, we provide a brief overview of HBV replication and some of the therapeutic strategies to combat chronic HBV infection. These descriptions are intended to contextualize our recent experimental efforts to characterize ε and identify ε-targeting ligands, with the ultimate goal of developing novel anti-HBV therapeutics.

Analysis of the Differential Expression and Antiviral Activity of Porcine Interferon-α In Vitro

Porcine interferon α (poIFN-α) is a crucial cytokine that can prevent and treat viral infections. Seventeen functional porcine IFN-α subtypes were found in the porcine genome. In this study, multiple sequence alignment was performed to analyze IFN-α protein structure and function. Phylogenetic tree analysis of the poIFN gene family defined the evolutionary relationship of various subtypes. PoIFN-αs, including poIFN-α1-17, were expressed in an Escherichia coli expression system. The antiviral activities of these IFN-α proteins against vesicular stomatitis virus (VSV) and pseudorabies virus (PRV) were examined in PK-15 cells. We found that the antiviral activity of different poIFN-α molecules greatly differed as follows: the poIFN-α14 and 17 subtypes had the greatest antiviral activities against VSV and PRV in PK-15 cells, poIFN-α1, 2, 3, and 8 exhibited lower biological activities, and poIFN-α4, 5, 6, 7, 9, 10, 11, 12, 13, and 16 had minimal or no effect in the tested target cell‒virus systems. Moreover, our studies demonstrated that the antiviral activity of IFN-α was positively correlated with the induction of IFN-stimulated genes, such as 2'-5' oligoadenylate synthetase 1 (OSA1), interferon-stimulated gene 15 (ISG15), myxoma resistance protein 1 (Mx1), and protein kinase R (PKR). Thus, our experimental results provide important information about the antiviral functions and mechanism of poIFN-α.

Protein quaternary structures in solution are a mixture of multiple forms

Over half the proteins in the E. coli cytoplasm form homo or hetero-oligomeric structures. Experimentally determined structures are often considered in determining a protein's oligomeric state, but static structures miss the dynamic equilibrium between different quaternary forms. The problem is exacerbated in homo-oligomers, where the oligomeric states are challenging to characterize. Here, we re-evaluated the oligomeric state of 17 different bacterial proteins across a broad range of protein concentrations and solutions by native mass spectrometry (MS), mass photometry (MP), size exclusion chromatography (SEC), and small-angle X-ray scattering (SAXS), finding that most exhibit several oligomeric states. Surprisingly, some proteins did not show mass-action driven equilibrium between the oligomeric states. For approximately half the proteins, the predicted oligomeric forms described in publicly available databases underestimated the complexity of protein quaternary structures in solution. Conversely, AlphaFold multimer provided an accurate description of the potential multimeric states for most proteins, suggesting that it could help resolve uncertainties on the solution state of many proteins.

Changes in antibody binding and functionality after humanizing a murine scFv anti-IFN-α2: From in silico studies to experimental analysis

The structural and dynamic changes introduced during antibody humanization continue to be a topic open to new contributions. For this reason, the study of structural and functional changes of a murine scFv (mu.scFv) anti-rhIFN-α2b after humanization was carried out. As it was shown by long molecular dynamics simulations and circular dichroism analysis, changes in primary sequence affected the tertiary structure of the humanized scFv (hz.scFv): the position of the variable domain of light chain (VL) respective to the variable domain of heavy chain (VH) in each scFv molecule was different. This change mainly impacted on conformation and dynamics of the complementarity-determining region 3 of VH (CDR-H3) which led to changes in the specificity and affinity of humanized scFv (hz.scFv). These observations agree with experimental results that showed a decrease in the antigen-binding strength of hz.scFv, and different capacities of these molecules to neutralize the in vitro rhIFN-α2b biological activity. Besides, experimental studies to characterize antigen-antibody binding showed that mu.scFv and hz.scFv bind to the same antigen area and recognize a conformational epitope, which is evidence of docking results. Finally, the differences between these molecules to neutralize the in vitro rhIFN-α2b biological activity were described as a consequence of the blockade of certain functionally relevant amino acids of the cytokine, after scFv binding. All these observations confirmed that humanization affected the affinity and specificity of hz.scFv and pointed out that two specific changes in the frameworks would be responsible.

Molecular and Structural Basis of Receptor Binding and Signaling of a Fish Type I IFN with Three Disulfide Bonds

In mammals, type I IFNs, which commonly contain one or two disulfide bonds, activate the JAK-STAT signaling pathway through binding to the common cell surface receptor formed by IFN-α/β receptor (IFNAR)1 and IFNAR2 subunits. Although type I IFNs are also known to be essential for antiviral defense in teleost fish, very little is known about mechanisms underlying the recognition of fish type I IFNs by associated receptors. In this study, we demonstrate that a type I IFN of large yellow croaker Larimichthys crocea (LcIFNi), belonging to a new subgroup of fish type I IFNs, triggers antiviral response via the conserved JAK-STAT pathway through stable binding with a heterodimeric receptor comprising subunits LcCRFB5 and LcCRFB2. LcIFNi binds to LcCRFB5 with a much higher affinity than to LcCRFB2. Furthermore, we determined the crystal structure of LcIFNi at a 1.39 Å resolution. The high-resolution structure is, to our knowledge, the first reported structure of a type I IFN with three disulfide bonds, all of which were found to be indispensable for folding and stability of LcIFNi. Using structural analysis, mutagenesis, and biochemical assays, we identified key LcIFNi residues involved in receptor interaction and proposed a structural model of LcIFNi bound to the LcCRFB2–LcCRFB5 receptor. The results show that LcIFNi–LcCRFB2 exhibits a similar binding pattern to human IFN-ω–IFNAR2, whereas the binding pattern of LcIFNi–LcCRFB5 is quite different from that of IFN-ω–IFNAR1. Altogether, our findings reveal the structural basis for receptor interaction and signaling of a type I IFN with three disulfide bonds and provide new insights into the mechanisms underlying type I IFN recognition in teleosts.

Disclosing the Potential of Fluorinated Ionic Liquids as Interferon-Alpha 2b Delivery Systems

Interferon-alpha 2b (IFN-α 2b) is a therapeutic protein used for the treatment of cancer, viral infections, and auto-immune diseases. Its application is hindered by a low bioavailability and instability in the bloodstream, and the search for new strategies for a target delivery and stabilization of IFN-α 2b to improve its therapeutic efficacy is crucial. Fluorinated ionic liquids (FILs) are promising biomaterials that: (i) can form self-assembled structures; (ii) have complete miscibility in water; and (iii) can be designed to have reduced toxicity. The influence of IFN-α 2b in the aggregation behaviour of FILs and the interactions between them were investigated through conductivity and surface tension measurements, and using electron microscopic and spectroscopy techniques to study FILs feasibility as an interferon-alpha 2b delivery system. The results show that the presence of IFN-α 2b influences the aggregation behaviour of FILs and that strong interaction between the two compounds occurs. The protein might not be fully encapsulated by FILs. However, the FIL can be tailored in the future to carry IFN-α 2b by the formation of a conjugate, which prevents the aggregation of this protein. This work constitutes a first step toward the design and development of FIL-based IFN-α 2b delivery systems.

Comparative Toxicity of Interferon Beta-1a Impurities of Heavy Metal Ions

Background and Objectives: Providing a proper quality control of drugs is essential for efficient treatment of various diseases minimizing the possible side effects of pharmaceutical active substances and potential impurities. Recent in vitro and in vivo studies have shown that certain heavy metalloids and metals interfere with protein folding of nascent proteins in cells and their biological function can be altered. It is unknown whether the drug impurities including heavy metals may affect the tertiary protein structure. Materials and Methods: ReciGen and Rebif are pharmaceutical interferon beta-1a (IFNβ-1a) contained in preparations that are used for parenteral administration. Heavy metal impurities of these samples have been studied by gel electrophoresis, Fourier-transform infrared spectroscopy (FTIR) and inductively coupled plasma mass spectrometry analysis (ICP MS). The concentration of heavy metals including mercury, arsenic, nickel, chromium, iron, and aluminum did not exceed permitted levels established by International Council for Harmonisation guideline for elemental impurities. Results: The ICP MS analysis revealed the presence of heavy metals, moreover zeta potential was significantly different for IFNβ-1a, which can be an indirect indication of the difference in composition of ReciGen and Rebif samples, respectively. FTIR analysis revealed very similar amide I and II bonds at 1654 and 1560 cm−1 attributed to the peptide absorption peaks of IFNβ-1a in Rebif and ReciGen. Conclusions: It was hypothesized that the IFNβ-1a complex binds heavy metals affecting the tertiary protein structure and may lead to some side effects of drug administration. Further testing of IFNβ-1a bioequivalence for parenteral application is necessary.

Electrostatics Drive Oligomerization and Aggregation of Human Interferon Alpha-2a

Aggregation is a common phenomenon in the field of protein therapeutics and can lead to function loss or immunogenic patient responses. Two strategies are currently used to reduce aggregation: (1) finding a suitable formulation, which is labor-intensive and requires large protein quantities, or (2) engineering the protein, which requires extensive knowledge about the protein aggregation pathway. We present a biophysical characterization of the oligomerization and aggregation processes by Interferon alpha-2a (IFNα-2a), a protein drug with antiviral and immunomodulatory properties. This study combines experimental high throughput screening with detailed investigations by small-angle X-ray scattering and analytical ultracentrifugation. Metropolis Monte Carlo simulations are used to gain insight into the underlying intermolecular interactions. IFNα-2a forms soluble oligomers that are controlled by a fast pH and concentration-dependent equilibrium. Close to the isoelectric point of 6, IFNα-2a forms insoluble aggregates which can be prevented by adding salt. We show that monomer attraction is driven mainly by molecular anisotropic dipole–dipole interactions that increase with increasing pH. Repulsion is due to monopole–monopole interactions and depends on the charge of IFNα-2a. The study highlights how combining multiple methods helps to systematically dissect the molecular mechanisms driving oligomer formation and to design ultimately efficient strategies for preventing detrimental protein aggregation.

Effect of backbone circularization on colloidal stability: Compaction of unfolded structures improves aggregation resistance of granulocyte colony-stimulating factor

Aggregation of protein therapeutics can lead to immunogenicity and loss of function in vivo. Its effective prevention requires an understanding of the conformational and colloidal stability of protein and the improvement of both. Granulocyte colony-stimulating factor (G-CSF), which is one of the most widely used protein therapeutics, was previously shown to be conformationally stabilized by connecting its N- and C-termini with amide bonds (backbone circularization). In this study, we investigated whether circularization affects the colloidal stability of proteins. Colloidal stability was indirectly assessed by analyzing the aggregation behavior of G-CSF variants using analytical ultracentrifugation (AUC) and small-angle X-ray scattering (SAXS). Consequently, we found that the unfolded structure of circularized G-CSF was more compact than non-circularized G-CSF, and that backbone circularization improved its aggregation resistance against chemical denaturation by guanidine hydrochloride (GdnHCl). The improved aggregation resistance suggests that the expansion tolerance of circularized G-CSF in the unfolded state increased its colloidal stability. Thus, backbone circularization is an excellent method for enhancing the colloidal and the conformational stability of protein with minimal sequence changes. It is therefore expected to be effective in extending the storage stability of protein therapeutics, enhancing their biological stability.

Interferon-Based Biopharmaceuticals: Overview on the Production, Purification, and Formulation

The advent of biopharmaceuticals in modern medicine brought enormous benefits to the treatment of numerous human diseases and improved the well-being of many people worldwide. First introduced in the market in the early 1980s, the number of approved biopharmaceutical products has been steadily increasing, with therapeutic proteins, antibodies, and their derivatives accounting for most of the generated revenues. The success of pharmaceutical biotechnology is closely linked with remarkable developments in DNA recombinant technology, which has enabled the production of proteins with high specificity. Among promising biopharmaceuticals are interferons, first described by Isaacs and Lindenmann in 1957 and approved for clinical use in humans nearly thirty years later. Interferons are secreted autocrine and paracrine proteins, which by regulating several biochemical pathways have a spectrum of clinical effectiveness against viral infections, malignant diseases, and multiple sclerosis. Given their relevance and sustained market share, this review provides an overview on the evolution of interferon manufacture, comprising their production, purification, and formulation stages. Remarkable developments achieved in the last decades are herein discussed in three main sections: (i) an upstream stage, including genetically engineered genes, vectors, and hosts, and optimization of culture conditions (culture media, induction temperature, type and concentration of inducer, induction regimens, and scale); (ii) a downstream stage, focusing on single- and multiple-step chromatography, and emerging alternatives (e.g., aqueous two-phase systems); and (iii) formulation and delivery, providing an overview of improved bioactivities and extended half-lives and targeted delivery to the site of action. This review ends with an outlook and foreseeable prospects for underdeveloped aspects of biopharma research involving human interferons.

Detailed Structure of Mouse Interferon α2 and Its Interaction with Sortilin

Interferon α (IFNα) is a type I interferon, an essential cytokine employed by the immune system to fight viruses. Although a number of the structures of type I interferons have been reported, most of the known structures of IFNα are in complex with its receptors. There are only two examples of structures of free IFNα: one is a dimeric X-ray structure without side-chain information; and another is an NMR structure of human IFNα. Although we have shown that Sortilin is involved in the secretion of IFNα, the details of the molecular interaction and the secretion mechanism remain unclear. Recently, we solved the X-ray structure of mouse Sortilin, but the structure of mouse IFNα remained unknown. In the present study, we determined the crystal structure of mouse IFNα2 at 2.1 Å resolution and investigated its interaction with Sortilin. Docking simulations suggested that Arg22 of mouse IFNα2 is important for the interaction with mouse Sortilin. Mutation of Arg22 to alanine facilitated IFNα2 secretion, as determined by flow cytometry, highlighting the contribution of this residue to the interaction with Sortilin. These results suggest an important role for Arg22 in mouse IFNα for Sortilin-mediated IFNα trafficking.

Shared and Unique Features of Human Interferon-Beta and Interferon-Alpha Subtypes

Type I interferons (IFN-I) were first discovered as an antiviral factor by Isaacs and Lindenmann in 1957, but they are now known to also modulate innate and adaptive immunity and suppress proliferation of cancer cells. While much has been revealed about IFN-I, it remains a mystery as to why there are 16 different IFN-I gene products, including IFNβ, IFNω, and 12 subtypes of IFNα. Here, we discuss shared and unique aspects of these IFN-I in the context of their evolution, expression patterns, and signaling through their shared heterodimeric receptor. We propose that rather than investigating responses to individual IFN-I, these contexts can serve as an alternative approach toward investigating roles for IFNα subtypes. Finally, we review uses of IFNα and IFNβ as therapeutic agents to suppress chronic viral infections or to treat multiple sclerosis.

Unique duplication of IFNh genes in Nile tilapia (Oreochromis niloticus) reveals lineage-specific evolution of IFNh in perciform fishes

Fish appear to harbour a complex type I IFN repertoire containing subgroups a, b, c, d, e, f, and h, and IFNh is only reported in perciform fishes. However, no multiple copies of IFNh gene has been identified in fish to date. In this study, two IFNh genes named On-IFNh1 and On-IFNh2 were cloned from Nile tilapia, Oreochromis niloticus. The predicted proteins of On-IFNh1 and On-IFNh2 contain several structural features known in type I IFNs, and estimation of divergence time revealed that these two genes may have arisen from a much recent local duplication event. On-IFNh genes were constitutively expressed in all tissues examined, with the highest expression level observed in gill, and were rapidly induced in all organs/tissues tested following the stimulation of poly(I:C). In addition, both recombinant On-IFNh1 and On-IFNh2 trigger a relative delayed but sustained induction of interferon-stimulated genes (ISGs), whereas recombinant On-IFNc elicits a rapid and transient expression of ISGs in vivo. The present study thus contributes to a better understanding of the functional properties of tilapia interferons, and also provides a new insight into the evolution of IFNh in fish.

The Role of Structure in the Biology of Interferon Signaling

Interferons (IFNs) are a family of cytokines with the unique ability to induce cell intrinsic programs that enhance resistance to viral infection. Induction of an antiviral state at the cell, tissue, organ, and organismal level is performed by three distinct IFN families, designated as Type-I, Type-II, and Type-III IFNs. Overall, there are 21 human IFNs, (16 type-I, 12 IFNαs, IFNβ, IFNϵ, IFNκ, and IFNω; 1 type-II, IFNγ; and 4 type-III, IFNλ1, IFNλ2, IFNλ3, and IFNλ4), that induce pleotropic cellular activities essential for innate and adaptive immune responses against virus and other pathogens. IFN signaling is initiated by binding to distinct heterodimeric receptor complexes. The three-dimensional structures of the type-I (IFNα/IFNAR1/IFNAR2), type-II (IFNγ/IFNGR1/IFNGR2), and type-III (IFNλ3/IFNλR1/IL10R2) signaling complexes have been determined. Here, we highlight similar and unique features of the IFNs, their cell surface complexes and discuss their role in inducing downstream IFN signaling responses.

Functional characterization of a group II interferon, IFNc in the perciform fish, Nile tilapia (Oreochromis niloticus)

Interferons are a family of class II α-helical cytokines playing vital roles in antiviral immune response, and little information is available to date regarding the interferon system of tilapia. In this study, a type I IFN gene, named On-IFNc, was identified in Nile tilapia, Oreochromis niloticus. The predicted protein of On-IFNc contains several structural features known in type I IFNs, and On-IFNc was clustered together with the known IFNc in fish into a separated clade in the phylogenetic tree. On-IFNc gene was constitutively expressed in all tissues examined, with the highest expression level observed in liver, and was rapidly induced in all organs/tissues tested following the stimulation of poly(I:C). In addition, recombinant On-IFNc has been proven to markedly induce the expression of the antiviral effectors, Mx and viperin, the signalling components, STAT1, STAT2, and IRF9, and the transcription factors, IRF3 and IRF7, as well as the tyrosine phosphorylation of STAT1 and STAT2 in fish cells. Furthermore, recombinant On-IFNc has been proven to possess antiviral activity against ISKNV. The present study thus contributes to a better understanding of the functional properties of the type I IFN system in tilapia.

Characterization of Type-I IFN subtype autoantibodies and activity in SLE serum and urine

BACKGROUND/OBJECTIVE

Type-I interferons contribute to pathogenesis in systemic lupus erythematosus, including nephritis. Interferons consist of a family of 16 proteins yet are often characterized in patients without knowledge of the specific interferon subtypes involved. Different interferons may function in the kidneys, and other organs, relative to what is often measured in patient blood. Moreover, antibodies to interferons may potentially modulate systemic or organ-specific interferon activity. The aim of this study was to characterize global interferon activity levels and identify autoantibodies to the 12 interferon α subtypes in patient serum and urine.

METHODS

Interferon activity levels in serum and urine were measured using an interferon bioassay. Anti-interferon and anti-cytokine autoantibodies were measured by ELISA. Serum and urine samples were also characterized for their ability to neutralize the biological activity of exogenously added interferons.

RESULTS

Serum interferon activity was increased in 62% of systemic lupus erythematosus patient samples, relative to healthy donor controls, whereas binding interferon α autoantibodies to at least one interferon α subtype were found in 68% of the samples evaluated. High Systemic Lupus Erythematosus Disease Activity Index scores were significantly (p = 0.001) associated with patient samples containing interferon α autoantibodies to three or more interferon α subtypes in their serum. Interferon α autoantibodies that potently block interferon activity were rare (∼5% of samples), but collectively bound to all 12 interferon α subtypes. Urine interferon activity and interferon α autoantibody profiles did not correlate with their serum counterparts, suggesting immune responses in systemic lupus erythematosus kidneys can be distinct from those measured in serum. Analysis of autoantibodies to 15 additional cytokines in serum identified higher frequencies of granulocyte-macrophage colony-stimulating factor and interleukin 17A autoantibodies, suggesting these signaling pathways may potentially contribute, with interferons, to systemic lupus erythematosus pathogenesis.

CONCLUSIONS

The measurement of autoantibodies to multiple interferon subtypes in serum and urine may provide an alternative method for following interferon-mediated systemic lupus erythematosus disease activity. The results suggest autoantibodies might be used for patient monitoring and/or identifying additional cytokine signaling pathways that are functioning in different systemic lupus erythematosus patients.

Metalation and Maturation of Zinc Ectoenzymes: A Perspective

Numerous zinc ectoenzymes are folded and activated in the compartments of the early secretory pathway, such as the ER and the Golgi apparatus, before reaching their final destination. During this process, zinc must be incorporated into the active site; therefore, metalation of the nascent protein is indispensable for the expression of the active enzyme. However, to date, the molecular mechanism underlying this process has been poorly investigated. This is in sharp contrast to the physiological and pathophysiological roles of zinc ectoenzymes, which have been extensively investigated over the past decades. This manuscript concisely outlines the present understanding of zinc ectoenzyme activation through metalation by zinc and compares this with copper ectoenzyme activation, in which elaborate copper metalation mechanisms are known. Moreover, based on the comparison, several hypotheses are discussed. Approximately 80 years have passed since the first zinc enzyme was identified; therefore, it is necessary to improve our understanding of zinc ectoenzymes from a biochemical perspective, which will further our understanding of their biological roles.

The Role of Zinc in Antiviral Immunity

Zinc is an essential trace element that is crucial for growth, development, and the maintenance of immune function. Its influence reaches all organs and cell types, representing an integral component of approximately 10% of the human proteome, and encompassing hundreds of key enzymes and transcription factors. Zinc deficiency is strikingly common, affecting up to a quarter of the population in developing countries, but also affecting distinct populations in the developed world as a result of lifestyle, age, and disease-mediated factors. Consequently, zinc status is a critical factor that can influence antiviral immunity, particularly as zinc-deficient populations are often most at risk of acquiring viral infections such as HIV or hepatitis C virus. This review summarizes current basic science and clinical evidence examining zinc as a direct antiviral, as well as a stimulant of antiviral immunity. An abundance of evidence has accumulated over the past 50 y to demonstrate the antiviral activity of zinc against a variety of viruses, and via numerous mechanisms. The therapeutic use of zinc for viral infections such as herpes simplex virus and the common cold has stemmed from these findings; however, there remains much to be learned regarding the antiviral mechanisms and clinical benefit of zinc supplementation as a preventative and therapeutic treatment for viral infections.

Zinc ions increase GH signaling ability through regulation of available plasma membrane-localized GHR

It is well known that zinc ion (Zn²⁺ ) can regulate the biological activity of growth hormone (GH). However, until now, the mechanism by which Zn²⁺ regulates GH biological activity remains unclear. In the current study, we first performed molecular docking between Zn²⁺ and porcine GH (pGH) using computational biology. We then explored the effect of Zn²⁺ on the GH signaling ability in the cell model expressing porcine growth hormone receptor (GHR). It was found that the phosphorylation levels of Janus kinase 2, signal transducers and activators of transcription 5/3/1, and GHR increased significantly under Zn²⁺ treatment, indicating that Zn²⁺ can enhance the signaling ability of GH/GHR. On this basis, we further explored how Zn²⁺ regulates the biological activity of GH/GHR. The results showed that downregulation and turnover of GHR changed under Zn²⁺ /pGH treatment. Zn²⁺ enhanced the membrane residence time of pGH/GHR and delayed GHR downregulation. Further investigation showed that the internalization dynamic of pGH/GHR was changed by Zn²⁺ , which prolonged the residence time of pGH/GHR in the cell membrane. These factors acted together to upregulate the signaling of GH/GHR. This study lays a foundation for further exploration of the biological effects of Zn²⁺ on GH.

Toll-like receptor-induced cytokines as immunotherapeutic targets in cancers and autoimmune diseases

Immune cells of the myeloid and lymphoid lineages express Toll-like receptors (TLRs) to recognize pathogenic components or cellular debris and activate the immune system through the secretion of cytokines. Cytokines are signaling molecules that are structurally and functionally distinct from one another, although their secretion profiles and signaling cascades often overlap. This situation gives rise to pleiotropic cell-to-cell communication pathways essential for protection from infections as well as cancers. Nonetheless, deregulated signaling can have detrimental effects on the host, in the form of inflammatory or autoimmune diseases. Because cytokines are associated with numerous autoimmune and cancerous conditions, therapeutic strategies to modulate these molecules or their biological responses have been immensely beneficial over the years. There are still challenges in the regulation of cytokine function in patients, even in those who take approved biological therapeutics. In this review, our purpose is to discuss the differential expression patterns of TLR-regulated cytokines and their cell type specificity that is associated with cancers and immune-system-related diseases. In addition, we highlight key structural features and molecular recognition of cytokines by receptors; these data have facilitated the development and approval of several biologics for the treatment of autoimmune diseases and cancers.

Different Interferon Beta Preparations Induce the Same Qualitative Immune Response in Human Skin

Interferon beta (IFNβ) is used as a first-line treatment for multiple sclerosis (MS) and is injected intramuscularly or subcutaneously (s.c.). The subcutaneous route is considered more immunogenic as it is associated with increased antidrug antibody-positive patients. The skin contains dendritic cells (DCs) and it is unclear whether these contribute to immunogenicity. To assess the effect of IFNβ on skin-resident cells, IFNβ was injected intradermally (i.d.) ex vivo using a human skin explant model or s.c. in vivo in MS patients. Ex vivo, intradermal IFNβ injections reduced migration and enhanced surface CD86 expression of dermal DCs, and an increased expression of HLA-DR⁺ was observed in skin biopsies taken after subcutaneous IFNβ injection (in vivo). In both models, IFNβ elevated the expression of several inflammatory cytokines when compared to the control biopsies. Our results show that 3 different IFNβ preparations, normalized in dose and injection site, induce similar immune responses, suggesting that the differences in immunogenicity are likely due to the route and frequency of administration.

Sequence analysis and characterization of type I interferon and type II interferon from the critically endangered sturgeon species, A. dabryanus and A. sinensis

In the present study, we identify three type I interferon (IFN) genes (Ad/AsIFNe1-3) and a type II IFN gene (Ad/AsIFNγ) from the Dabry's sturgeon (Acipenser dabryanus) and the Chinese sturgeon (Acipenser sinensis). Sequence analysis revealed that Ad/AsIFNe1-3 and Ad/AsIFNγ contain several conserved characteristics, including signal peptides, interferon alpha, beta, and delta (IFabd) domains, and N-glycosylation sites. Ad/AsIFNe1-3 belongs to the type I IFN group I subgroup, possessing two conserved cysteines residues (C1 and C3), and Ad/AsIFNγ contained a conserved nuclear localization sequence (NLS) motif. Ad/AsIFNe1-3 and Ad/AsIFNγ contain signature motifs indicative of their corresponding IFN group. The Ad/AsIFNe1-3 and Ad/AsIFNγ genes were found to consist of 5 exons/4 introns and 4 exons/3 introns, respectively. These IFNs were separated by four phase 0 introns (type I IFN) and three phase 0 introns (type II IFN). The sequences of IFNe1-3 and IFNγ from the Dabry's sturgeon and the Chinese sturgeon were closely aligned, suggested that these two species are closely related. Phylogenetic analysis revealed that Ad/AsIFNe1-3 and Ad/AsIFNγ clustered together with the corresponding homologous proteins from other fish species. AdIFNe1-3 were found to be high expressed in early embryonic development, suggesting that AdIFNe1-3 might indicate maternal transmission, while AdIFNγ may not mediate embryonic development. Tissue distribution analysis revealed that AdIFNe1-3 and AdIFNγ carry out biological functions in immune and non-immune tissues compartments. AdIFNe1-3 and AdIFNγ can be stimulated by polyinosinic-polycytidylic acid (poly I:C) and lipopolysaccharides (LPS). AdIFNe1-3 have stronger antiviral activity than AdIFNγ, and AdIFNγ has a stronger antibacterial activity than AdIFNe1-3. The differential responses of these genes to poly I:C and LPS suggest differences in the mechanisms of defense against viruses and bacteria.

Interferon-Inducible Myxovirus Resistance Proteins: Potential Biomarkers for Differentiating Viral from Bacterial Infections

BACKGROUND

In 2015, the 68th World Health Assembly declared that effective, rapid, low-cost diagnostic tools were needed for guiding optimal use of antibiotics in medicine. This review is devoted to interferon-inducible myxovirus resistance proteins as potential biomarkers for differentiating viral from bacterial infections.

CONTENT

After viral infection, a branch of the interferon (IFN)-induced molecular reactions is triggered by the binding of IFNs with their receptors, a process leading to the activation of mx1 and mx2, which produce antiviral Mx proteins (MxA and MxB). We summarize current knowledge of the structures and functions of type I and III IFNs. Antiviral mechanisms of Mx proteins are discussed in reference to their structural and functional data to provide an in-depth picture of protection against viral attacks. Knowing such a mechanism may allow the development of countermeasures and the specific detection of any viral infection. Clinical research data indicate that Mx proteins are biomarkers for many virus infections, with some exceptions, whereas C-reactive protein (CRP) and procalcitonin have established positions as general biomarkers for bacterial infections.

SUMMARY

Mx genes are not directly induced by viruses and are not expressed constitutively; their expression strictly depends on IFN signaling. MxA protein production in peripheral blood cells has been shown to be a clinically sensitive and specific marker for viral infection. Viral infections specifically increase MxA concentrations, whereas viruses have only a modest increase in CRP or procalcitonin concentrations. Therefore, comparison of MxA and CRP and/or procalcitonin values can be used for the differentiation of infectious etiology.

Human interferon-ϵ and interferon-κ exhibit low potency and low affinity for cell-surface IFNAR and the poxvirus antagonist B18R

IFNϵ and IFNκ are interferons that induce microbial immunity at mucosal surfaces and in the skin. They are members of the type-I interferon (IFN) family, which consists of 16 different IFNs, that all signal through the common IFNAR1/IFNAR2 receptor complex. Although IFNϵ and IFNκ have unique expression and functional properties, their biophysical properties have not been extensively studied. In this report, we describe the expression, purification, and characterization of recombinant human IFNϵ and IFNκ. In cellular assays, IFNϵ and IFNκ exhibit ∼1000-fold lower potency than IFNα2 and IFNω. The reduced potency of IFNϵ and IFNκ are consistent with their weak affinity for the IFNAR2 receptor chain. Despite reduced IFNAR2-binding affinities, IFNϵ and IFNκ exhibit affinities for the IFNAR1 chain that are similar to other IFN subtypes. As observed for cellular IFNAR2 receptor, the poxvirus antagonist, B18R, also exhibits reduced affinity for IFNϵ and IFNκ, relative to the other IFNs. Taken together, our data suggest IFNϵ and IFNκ are specialized IFNs that have evolved to weakly bind to the IFNAR2 chain, which allows innate protection of the mucosa and skin and limits neutralization of IFNϵ and IFNκ biological activities by viral IFN antagonists.

Site-specific derivatization of human interferon β-1a at lysine residues using microbial transglutaminase

Microbial transglutaminase (TGase) has been successfully used to produce site-specific protein conjugates derivatized at the level of glutamine (Gln) or lysine (Lys) residues with diverse applications. Here, we study the drug human interferon β-1a (IFN) as a substrate of TGase. The derivatization reaction was performed using carbobenzoxy-L-glutaminyl-glycine to modify Lys residues and dansylcadaverine for Gln residues. The 166 amino acids polypeptide chain of IFN β-1a contains 11 Lys and 11 Gln residues potential sites of TGase derivatization. By means of mass spectrometry analyses, we demonstrate the highly selective derivatization of this protein by TGase at the level of Lys115 and as secondary site at the level of Lys33, while no reactive Gln residue was detected. Limited proteolysis experiments were performed on IFN to determine flexible regions of the protein under physiological conditions. Interestingly, primary and secondary sites of limited proteolysis and of TGase derivatization occur at the same regions of the polypeptide chain, indicating that the extraordinary selectivity of the TGase-mediated reaction is dictated by the conformational features of the protein substrate. We envisage that the TGase-mediated derivatization of IFN can be used to produce interesting derivatives of this important therapeutic protein.

Production of bioactive liver-targeting interferon Mu-IFN-CSP by soluble prokaryotic expression

A novel liver-targeting interferon (IFN-CSP) was successfully over-expressed in our previous work. The in vitro and in vivo investigation revealed that IFN-CSP has significant anti-hepatitis B virus (HBV) effect and liver-targeting capacity. However, due to the IFN-CSP tends to form inclusion bodies in recombinant Escherichia coli (E. coli), efficient production of the soluble liver-targeting interferon is a challenge. In view of biomedical application, novel strategies for efficiently expressing liver-targeting interferon and overcoming its poor solubility are necessary and important. In the present study, a modified mu-IFN-CSP was designed base on the amino acid mutant of the native IFN-CSP. Meanwhile, the coding sequence of mu-IFN-CSP was optimized for E. coli preferred codon and the induction conditions for expression were optimized by an orthogonal test. After amino acid mutant, codon optimization and induction conditions optimization, the solubility of Mu-IFN-CSP in E. coli was up to 98.4%. The structural comparison and molecular dynamic simulation showed that the Mu-IFN-CSP formed three structure changes and were more stable than the native IFN-CSP. Tissue sections binding assays revealed that Mu-IFN-CSP was also able to specific binding to liver. In vitro anti-HBV activity assays showed that the soluble Mu-IFN-CSP has improved anti-HBV effect in HepG2.2.15 cells compared to the native IFN-CSP. The present study reports for the first time that liver-targeting interferon Mu-IFN-CSP can be expressed as soluble form, and also contributes to further support its application as liver-targeting anti-HBV medicine.

A panel of synthetic antibodies that selectively recognize and antagonize members of the interferon alpha family

The 12 distinct subtypes that comprise the interferon alpha (IFNα) family of cytokines possess anti-viral, anti-proliferative and immunomodulatory activities. They are implicated in the etiology and progression of many diseases, and also used as therapeutic agents for viral and oncologic disorders. However, a deeper understanding of their role in disease is limited by a lack of tools to evaluate single subtypes at the protein level. Antibodies that selectively inhibit single IFNα subtypes could enable interrogation of each protein in biological samples and could be used for characterization and treatment of disease. Using phage-displayed synthetic antibody libraries, we have conducted selections against 12 human IFNα subtypes to explore our ability to obtain fine-specificity antibodies that recognize and antagonize the biological signals induced by a single IFNα subtype. For the first time, we have isolated antibodies that specifically recognize individual IFNα subtypes (IFNα2a/b, IFNα6, IFNα8b and IFNα16) with high affinity that antagonize signaling. Our results show that highly specific antibodies capable of distinguishing between closely related cytokines can be isolated from synthetic libraries and can be used to characterize cytokine abundance and function.

Interferon dimers: IFN-PEG-IFN

Increasingly complex proteins can be made by a recombinant chemical approach where proteins that can be made easily can be combined by site-specific chemical conjugation to form multifunctional or more active protein therapeutics. Protein dimers may display increased avidity for cell surface receptors. The increased size of protein dimers may also increase circulation times. Cytokines bind to cell surface receptors that dimerise, so much of the solvent accessible surface of a cytokine is involved in binding to its target. Interferon (IFN) homo-dimers (IFN-PEG-IFN) were prepared by two methods: site-specific bis-alkylation conjugation of PEG to the two thiols of a native disulphide or to two imidazoles on a histidine tag of two His₈-tagged IFN (His₈IFN). Several control conjugates were also prepared to assess the relative activity of these IFN homo-dimers. The His₈IFN-PEG₂₀-His₈IFN obtained by histidine-specific conjugation displayed marginally greater in vitro antiviral activity compared to the IFN-PEG₂₀-IFN homo-dimer obtained by disulphide re-bridging conjugation. This result is consistent with previous observations in which enhanced retention of activity was made possible by conjugation to an N-terminal His-tag on the IFN. Comparison of the antiviral and antiproliferative activities of the two IFN homo-dimers prepared by disulphide re-bridging conjugation indicated that IFN-PEG₁₀-IFN was more biologically active than IFN-PEG₂₀-IFN. This result suggests that the size of PEG may influence the antiviral activity of IFN-PEG-IFN homo-dimers.

Zinc is a potent and specific inhibitor of IFN-λ3 signalling

Lambda interferons (IFNL, IFN-λ) are pro-inflammatory cytokines important in acute and chronic viral infection. Single-nucleotide polymorphisms rs12979860 and rs8099917 within the IFNL gene locus predict hepatitis C virus (HCV) clearance, as well as inflammation and fibrosis progression in viral and non-viral liver disease. The underlying mechanism, however, is not defined. Here we show that the rs12979860 CC genotype correlates with increased hepatic metallothionein expression through increased systemic zinc levels. Zinc interferes with IFN-λ3 binding to IFNL receptor 1 (IFNLR1), resulting in decreased antiviral activity and increased viral replication (HCV, influenza) in vitro. HCV patients with high zinc levels have low hepatocyte antiviral and inflammatory gene expression and high viral loads, confirming the inhibitory role of zinc in vivo. We provide the first evidence that zinc can act as a potent and specific inhibitor of IFN-λ3 signalling and highlight its potential as a target of therapeutic intervention for IFN-λ3-mediated chronic disease.

Intronless and intron-containing type I IFN genes coexist in amphibian Xenopus tropicalis: Insights into the origin and evolution of type I IFNs in vertebrates

Type I IFNs are considered to be the core IFN species in vertebrates because of their predominant antiviral effects. But, a puzzling question remains to be answered, as to how intronless type I IFN genes in amniotes might have evolved from intron-containing type I IFN genes in fish and amphibians. In this study, intronless and intron-containing type I IFNs were found in the amphibian model, Xenopus tropicalis, with a total of sixteen and five genes, respectively. The intronless IFNs can be divided into three subgroups, and the intron-containing ones into two subgroups, implying that a retroposition event might have occurred in amphibians, resulting in the generation of intronless type I IFN genes. Two models were tentatively proposed to explain the evolution of type I IFNs in vertebrates: in model A, fish should possess the most primitive multi-exon-containing type I IFNs, and intronless type I IFN genes in amphibians are the ancestor of modern intronless type I IFNs in amniotes; in model B, intronless type I IFN genes in X. tropicalis may just represent an independent bifurcation in this species or probably in amphibians, and intronless type I IFN genes in amniotes may have arisen from another retroposition event occurred in a transition period even when reptiles were diverged from amphibians. It is considered that the model B can reflect the current knowledge on the occurrence of intronless and intron-containing type I IFN genes in vertebrate lineages. This study thus contributes to a better understanding of the origin and evolution of type I IFNs in vertebrates, and of the occurrence of intronless I IFNs in higher vertebrates.

Altering the central carbon metabolism of HEK293 cells: Impact on recombinant glycoprotein quality

The accumulation of metabolic by-products remains a critical challenge in the development of mammalian cells culture processes as it impacts cellular growth, productivity and product quality. Although the overexpression of the PYC2 gene was shown to significantly improve the nutrient metabolism efficiency of mammalian cells, its impact on recombinant protein quality has not been investigated yet. In this study, we assess the effect of this metabolic engineering strategy on the quality of a recombinant therapeutic glycoprotein, the human interferon α2b (IFNα2b). As inferred from densitometry analysis of SDS-PAGE gels, PYC2-overexpressing cells sustained a higher percentage of intact glycosylated IFNα2b at the late stage of batch cultures, which was correlated with prolonged viability and reduced accumulation of waste metabolites. Contrarily to the IFNα2b produced by the PYC2 cells, LC-MS analysis confirmed the presence of less glycosylated IFNα2b as well as the occurrence of proteolytic cleavage in the IFNα2b produced in the parental cells. Taken together, these results indicate that PYC2-overexpression in mammalian cells leads to extended favorable conditions for glycosylation and offer an attractive approach to mass-produce high-quality recombinant proteins.

Effects of localized interactions and surface properties on stability of protein-based therapeutics

OBJECTIVES

Protein-based therapeutics garner significant attention because of exquisite specificity and limited side effects and are now being used to accomplish targeted delivery of small-molecule drugs. This review identifies and highlights individual chemical attributes and categorizes how site-specific changes affect protein stability based on published high-resolution molecular analyses.

KEY FINDINGS

Because it is challenging to determine the mechanisms by which the stability of large, complex molecules is altered and data are sparse, smaller, therapeutic proteins (insulin, erythropoietin, interferons) are examined alongside antibody data. Integrating this large pool of information with the limited available studies on antibodies reveals common mechanisms by which specific alterations affect protein structure and stability.

SUMMARY

Physical and chemical stability of therapeutic proteins and antibody drug conjugates (ADCs) is of critical importance because insufficient stability prevents molecules from making it to market. Individual moieties on/near the surface of proteins have substantial influence on structure and stability. Seemingly small, superficial modification may have far-reaching consequences on structure, conformational dynamics, and solubility of the protein, and hence physical stability of the molecule. Chemical modifications, whether spontaneous (e.g. oxidation, deamidation) or intentional, as with ADCs, may adversely impact stability by disrupting local surface properties or higher order protein structure.

Roles of Zinc Signaling in the Immune System

Zinc (Zn) is an essential micronutrient for basic cell activities such as cell growth, differentiation, and survival. Zn deficiency depresses both innate and adaptive immune responses. However, the precise physiological mechanisms of the Zn-mediated regulation of the immune system have been largely unclear. Zn homeostasis is tightly controlled by the coordinated activity of Zn transporters and metallothioneins, which regulate the transport, distribution, and storage of Zn. There is growing evidence that Zn behaves like a signaling molecule, facilitating the transduction of a variety of signaling cascades in response to extracellular stimuli. In this review, we highlight the emerging functional roles of Zn and Zn transporters in immunity, focusing on how crosstalk between Zn and immune-related signaling guides the normal development and function of immune cells.

Site-Specific Transglutaminase-Mediated Conjugation of Interferon α-2b at Glutamine or Lysine Residues

Interferon α (IFN α) subtypes are important protein drugs that have been used to treat infectious diseases and cancers. Here, we studied the reactivity of IFN α-2b to microbial transglutaminase (TGase) with the aim of obtaining a site-specific conjugation of this protein drug. Interestingly, TGase allowed the production of two monoderivatized isomers of IFN with high yields. Characterization by mass spectrometry of the two conjugates indicated that they are exclusively modified at the level of Gln101 if the protein is reacted in the presence of an amino-containing ligand (i.e., dansylcadaverine) or at the level of Lys164 if a glutamine-containing molecule is used (i.e., carbobenzoxy-l-glutaminyl-glycine, ZQG). We explained the extraordinary specificity of the TGase-mediated reaction on the basis of the conformational features of IFN. Indeed, among the 10 Lys and 12 Gln residues of the protein, only Gln101 and Lys164 are located in highly flexible protein regions. The TGase-mediated derivatization of IFN was then applied to the production of IFN derivatives conjugated to a 20 kDa polyethylene glycol (PEG), using PEG-NH₂ for Gln101 derivatization and PEG modified with ZQG for Lys164 derivatization. The two mono-PEGylated isomers of IFN were obtained in good yields, purified, and characterized in terms of protein conformation, antiviral activity, and pharmacokinetics. Both conjugates maintained a native-like secondary structure, as indicated by far-UV circular dichroism spectra. Importantly, they disclosed good in vitro antiviral activity retention (about only 1.6- to 1.8-fold lower than that of IFN) and half-lives longer (about 5-fold) than that of IFN after intravenous administration to rats. Overall, these results provide evidence that TGase can be used for the development of site-specific derivatives of IFN α-2b possessing interesting antiviral and pharmacokinetic properties.

A Potent In Vivo Antitumor Efficacy of Novel Recombinant Type I Interferon

Purpose: Antiproliferative, antiviral, and immunomodulatory activities of endogenous type I IFNs (IFN1) prompt the design of recombinant IFN1 for therapeutic purposes. However, most of the designed IFNs exhibited suboptimal therapeutic efficacies against solid tumors. Here, we report evaluation of the in vitro and in vivo antitumorigenic activities of a novel recombinant IFN termed sIFN-I.Experimental Design: We compared primary and tertiary structures of sIFN-I with its parental human IFNα-2b, as well as affinities of these ligands for IFN1 receptor chains and pharmacokinetics. These IFN1 species were also compared for their ability to induce JAK-STAT signaling and expression of the IFN1-stimulated genes and to elicit antitumorigenic effects. Effects of sIFN-I on tumor angiogenesis and immune infiltration were also tested in transplanted and genetically engineered immunocompetent mouse models.Results: sIFN-I displayed greater affinity for IFNAR1 (over IFNAR2) chain of the IFN1 receptor and elicited a greater extent of IFN1 signaling and expression of IFN-inducible genes in human cells. Unlike IFNα-2b, sIFN-I induced JAK-STAT signaling in mouse cells and exhibited an extended half-life in mice. Treatment with sIFN-I inhibited intratumoral angiogenesis, increased CD8⁺ T-cell infiltration, and robustly suppressed growth of transplantable and genetically engineered tumors in immunodeficient and immunocompetent mice.Conclusions: These findings define sIFN-I as a novel recombinant IFN1 with potent preclinical antitumorigenic effects against solid tumor, thereby prompting the assessment of sIFN-I clinical efficacy in humans. Clin Cancer Res; 23(8); 2038-49. ©2016 AACR.

Preparation and characterization of latex films photo-immobilized with IFN-α

We developed a biomaterial by photo-immobilizing interferon-α (IFN-α) on the surface of latex condom films for the prevention and treatment of cervicitis, cervical cancers and diseases caused by cervical virus. The IFN-α modification by photoactive N-(4-azidobenzoyloxy) succinimide was characterized on a nano-scale by spectroscopy analysis and micro morphology. The anti-bacterial, anti-cancer, and anti-viral effects of the modified bioactive latex films were evaluated by antibacterial susceptibility testing, Gram staining, flow cytometry, immunofluorescence, and Western blotting. Our results showed that the photo-immobilized IFN-α latex films effectively inhibited the growth of both Neisseria gonorrhoeae and human cervical cancer HeLa cells. Moreover, the expression of anti-viral proteins, including P56, MxA, and 2', 5'-OAS, in the human cervical epithelial cell line NC104 was significantly increased by photo-immobilized IFN-α latex films. Taken together, these results suggest that photo-immobilized IFN-α latex films may have therapeutic effects against cervicitis, cervical cancers, and cervical virus.

Soluble Prokaryotic Expression and Purification of Human Interferon Alpha-2b Using a Maltose-Binding Protein Tag

Human interferon alpha-2b (IFNα-2b) has therapeutic applications as an antiviral and antiproliferative drug and has been used for a wide range of indications. Efficient production of IFNα-2b in Escherichia coli has been difficult because the protein tends to form inclusion bodies. This obstacle has garnered interest in efficiently expressing IFNα-2b and overcoming its poor solubility. In this study, seven N-terminal fusion partners - hexahistidine (His6), thioredoxin, glutathione S-transferase (GST), maltose-binding protein (MBP), N-utilization substance protein A, protein disulfide bond isomerase (PDI), and b'a' domain of PDI - were tested for soluble overexpression of codon-optimized IFNα-2b in E. coli. Low temperature increased the expression level of all of the tagged proteins except for the GST fusion. All the tags, except for His6 and GST, improved solubility. We purified IFNα-2b from the MBP-tagged fusion using immobilized metal affinity chromatography and anion exchange chromatography, and obtained a final yield of 7.2 mg from an initial 500-ml culture. The endotoxin level was 0.46 EU/µg. Biological activity was demonstrated using a luciferase assay, which showed a dose-dependent response with a calculated EC50 of 10.3 ± 5.9 pM. Our results demonstrate that using an MBP-tagged fusion is an efficient way to produce pure IFNα-2b.

Cytokine Activation by Antibody Fragments Targeted to Cytokine-Receptor Signaling Complexes

Exogenous cytokine therapy can induce systemic toxicity, which might be prevented by activating endogenously produced cytokines in local cell niches. Here we developed antibody-based activators of cytokine signaling (AcCS), which recognize cytokines only when they are bound to their cell surface receptors. AcCS were developed for type I interferons (IFNs), which induce cellular activities by binding to cell surface receptors IFNAR1 and IFNAR2. As a potential alternative to exogenous IFN therapy, AcCS were shown to potentiate the biological activities of natural IFNs by ∼100-fold. Biochemical and structural characterization demonstrates that the AcCS stabilize the IFN-IFNAR2 binary complex by recognizing an IFN-induced conformational change in IFNAR2. Using IFN mutants that disrupt IFNAR1 binding, AcCS were able to enhance IFN antiviral potency without activating antiproliferative responses. This suggests AcCS can be used to manipulate cytokine signaling for basic science and possibly for therapeutic applications.

Structural basis of the broadly neutralizing anti-interferon-α antibody rontalizumab

Interferons-alpha (IFN-α) are the expressed gene products comprising thirteen type I interferons with protein pairwise sequence similarities in the 77-96% range. Three other widely expressed human type I interferons, IFN-β, IFN-κ and IFN-ω have sequences 29-33%, 29-32% and 56-60% similar to the IFN-αs, respectively. Type I interferons act on immune cells by producing subtly different immune-modulatory effects upon binding to the extracellular domains of a heterodimeric cell-surface receptor composed of IFNAR1 and IFNAR2, most notably anti-viral effects. IFN-α has been used to treat infection by hepatitis-virus type C (HCV) and a correlation between hyperactivity of IFN-α-induced signaling and systemic lupus erythematosis (SLE), or lupus, has been noted. Anti-IFN-α antibodies including rontalizumab have been under clinical study for the treatment of lupus. To better understand the rontalizumab mechanism of action and specificity, we determined the X-ray crystal structure of the Fab fragment of rontalizumab bound to human IFN-α2 at 3Å resolution and find substantial overlap of the antibody and IFNA2 epitopes on IFN-α2.

IFNA2: The prototypic human alpha interferon

The human interferon α2 (IFNα2) was the first highly active IFN subtype to be cloned in the early eighties. It was also the first IFN and the first cytokine to be produced and commercialized by the pharmaceutical industry. Ipso facto it became the favorite IFNα subtype for academic researchers. For this fortunate reason IFNα2 has been at the origin of most discoveries related to the mechanism of action of type I interferons.