Early plasma interferon-β levels as a predictive marker of COVID-19 severe clinical events in adult patients

We assessed relationships between early peripheral blood type I interferons (IFN) levels, clinical new early warning scores (NEWS), and clinical outcomes in hospitalized coronavirus disease-19 (COVID-19) adult patients. Early IFN-β levels were lower among patients who further required intensive care unit (ICU) admission than those measured in patients who did not require an ICU admission during severe acute respiratory syndrome coronavirus type 2 infection. IFN-β levels were inversely correlated with NEWS only in the subgroup of patients who further required ICU admission. To assess whether peripheral blood IFN-β levels could be a potential relevant biomarker to predict further need for ICU admission, we performed receiver operating characteristic (ROC) curve analyses that showed for all study patients an area under ROC curve of 0.77 growing to 0.86 (p = 0.003) when the analysis was restricted to a subset of patients with NEWS ≥5 at the time of hospital admission. Overall, our findings indicated that early peripheral blood IFN-β levels might be a relevant predictive marker of further need for an ICU admission in hospitalized COVID-19 adult patients, specifically when clinical score (NEWS) was graded as upper than 5 at the time of hospital admission.

Structural basis for IFN antagonism by human respiratory syncytial virus nonstructural protein 2

Human respiratory syncytial virus (RSV) nonstructural protein 2 (NS2) inhibits host interferon (IFN) responses stimulated by RSV infection by targeting early steps in the IFN-signaling pathway. But the molecular mechanisms related to how NS2 regulates these processes remain incompletely understood. To address this gap, here we solved the X-ray crystal structure of NS2. This structure revealed a unique fold that is distinct from other known viral IFN antagonists, including RSV NS1. We also show that NS2 directly interacts with an inactive conformation of the RIG-I-like receptors (RLRs) RIG-I and MDA5. NS2 binding prevents RLR ubiquitination, a process critical for prolonged activation of downstream signaling. Structural analysis, including by hydrogen-deuterium exchange coupled to mass spectrometry, revealed that the N terminus of NS2 is essential for binding to the RIG-I caspase activation and recruitment domains. N-terminal mutations significantly diminish RIG-I interactions and result in increased IFNβ messenger RNA levels. Collectively, our studies uncover a previously unappreciated regulatory mechanism by which NS2 further modulates host responses and define an approach for targeting host responses.

Biocompatible Coatings from Smart Biopolymer Nanoparticles for Enzymatically Induced Drug Release

Nanoparticles can be used as a smart drug delivery system, when they release the drug only upon degradation by specific enzymes. A method to create such responsive materials is the formation of hydrogel nanoparticles, which have enzymatically degradable crosslinkers. Such hydrogel nanoparticles were prepared by ionotropic gelation sodium alginate with lysine-rich peptide sequences-either α-poly-L-lysine (PLL) or the aggrecanase-labile sequence KKKK-GRD-ARGSV↓NITEGE-DRG-KKKK. The nanoparticle suspensions obtained were analyzed by means of dynamic light scattering and nanoparticle tracking analysis. Degradation experiments carried out with the nanoparticles in suspension revealed enzyme-induced lability. Drugs present in the polymer solution during the ionotropic gelation can be encapsulated in the nanoparticles. Drug loading was investigated for interferon-β (IFN-β) as a model, using a bioluminescence assay with MX2Luc2 cells. The encapsulation efficiency for IFN-β was found to be approximately 25%. The nanoparticles suspension can be used to spray-coat titanium alloys (Ti-6Al-4V) as a common implant material. The coatings were proven by ellipsometry, reflection-absorption infrared spectroscopy, and X-ray photoelectron spectroscopy. An enzyme-responsive decrease in layer thickness is observed due to the degradation of the coatings. The Alg/peptide coatings were cytocompatible for human gingival fibroblasts (HGFIB), which was investigated by CellTiterBlue and lactate dehydrogenase (LDH) assay. However, HGFIBs showed poor adhesion and proliferation on the Alg/peptide coatings, but these could be improved by modification of the alginate with a RGD-peptide sequence. The smart drug release system presented can be further tailored to have the right release kinetics and cell adhesion properties.

IFNb of black carp functions importantly in host innate immune response as an antiviral cytokine

Type I interferons (IFN-Is) play an important role in the antiviral immune response in teleost fishes. In this study, one type I interferon (bcIFNb) from black carp (Mylopharyngodon piceus) has been cloned and characterized. The full-length cDNA of bcIFNb gene consists of 806 nucleotides and the predicted bcIFNb protein contains 188 amino acids. Basing on the cysteine number and evolutionary position, bcIFNb was classified into group II type I IFN. q-PCR analysis demonstrated that bcIFNb mRNA level varied in vivo and ex vivo in response to different stimuli. bcIFNb was detected in both the whole cell lysate and the supernatant media of HEK293T cells or EPC cells transfected with bcIFNb through immunoblot assay. IFN stimulated genes (ISGs) were greatly upregulated when the host cells were treated with the bcIFNb-containing conditioned media. EPC cells showed greatly enhanced antiviral ability when the cells were transfected with bcIFNb or treated with the bcIFNb-containing conditioned media before GCRV or SVCV infection. Glycosidase digestion analysis determined that bcIFNb was modified with N-linked glycosylation, which occurred on the Asn (N) of 92 site of this cytokine. The un-glycosylated mutant bcIFNb-N92Q presented the similar antiviral ability as that of wild type bcIFNb, which demonstrated that N-linked glycosylation did not contribute directly to the antiviral property of this fish cytokine.

Glycoengineering of interferon-β 1a improves its biophysical and pharmacokinetic properties

The purpose of this study was to develop a biobetter version of recombinant human interferon-β 1a (rhIFN-β 1a) to improve its biophysical properties, such as aggregation, production and stability, and pharmacokinetic properties without jeopardizing its activity. To achieve this, we introduced additional glycosylation into rhIFN-β 1a via site-directed mutagenesis. Glycoengineering of rhIFN-β 1a resulted in a new molecular entity, termed R27T, which was defined as a rhIFN-β mutein with two N-glycosylation sites at 80^th (original site) and at an additional 25^th amino acid due to a mutation of Thr for Arg at position 27^th of rhIFN-β 1a. Glycoengineering had no effect on rhIFN-β ligand-receptor binding, as no loss of specific activity was observed. R27T showed improved stability and had a reduced propensity for aggregation and an increased half-life. Therefore, hyperglycosylated rhIFN-β could be a biobetter version of rhIFN-β 1a with a potential for use as a drug against multiple sclerosis.

Site-specific PEGylation enhances the pharmacokinetic properties and antitumor activity of interferon beta-1b

Interferon beta (IFN-β) is widely used to ameliorate disease progression in patients with Multiple Sclerosis. IFN-β has a short half-life in humans, necessitating frequent administration for optimum effectiveness. Covalent modification of IFN-β with polyethylene glycol (PEG) improves the pharmacokinetic properties of the protein, but can adversely affect the protein's in vitro bioactivity. Random modification of lysine residues in IFN-β with amine-reactive PEGs decreased the in vitro bioactivity of the protein 50-fold, presumably due to modification of lysine residues near critical receptor binding sites. PEGylated IFN-β proteins that retained high in vitro bioactivity could be obtained by selective modification of the N-terminus of the protein with PEG. Here we use site-specific PEGylation technology (targeted attachment of a cysteine-reactive-PEG to an engineered cysteine residue in IFN-β) to identify several additional amino acid positions where PEG can be attached to IFN-β without appreciable loss of in vitro bioactivity. Unexpectedly, we found that most of the PEG-IFN-β analogs showed 11- to 78-fold improved in vitro bioactivities relative to their unPEGylated parent proteins and to IFN-β-1b. In vivo studies showed that a lead PEG-IFN-β protein had improved pharmacokinetic properties compared to IFN-β and was significantly more effective than IFN-β at inhibiting growth of a human tumor xenograft in athymic mice.

The differential antiviral activities of chicken interferon α (ChIFN-α) and ChIFN-β are related to distinct interferon-stimulated gene expression

Chicken interferon α (ChIFN-α) and ChIFN-β are type I IFNs that are important antiviral cytokines in the innate immune system. In the present study, we identified the virus-induced expression of ChIFN-α and ChIFN-β in chicken fibroblast DF-1 cells and systematically evaluated the antiviral activities of recombinant ChIFN-α and ChIFN-β by cytopathic-effect (CPE) inhibition assays. We found that ChIFN-α exhibited stronger antiviral activity than ChIFN-β in terms of inhibiting the replication of vesicular stomatitis virus, Newcastle disease virus and avian influenza virus, respectively. To elucidate the mechanism of differential antiviral activities between the two ChIFNs, we measured the relative mRNA levels of IFN-stimulated genes (ISGs) in IFN-treated DF-1 cells by real-time PCR. ChIFN-α displayed greater induction potency than ChIFN-β on several ISGs encoding antiviral proteins and MHC-I, whereas ChIFN-α was less potent than ChIFN-β for inducing ISGs involved in signaling pathways. In conclusion, ChIFN-α and ChIFN-β presented differential induction potency on various sets of ISGs, and the stronger antiviral activity of ChIFN-α is likely attributed to the greater expression levels of downstream antiviral ISGs.

An activity-independent selection system of thermostable protein variants

We describe an activity-independent method for the selection of thermostable mutants of any protein. It is based on a fusion construct comprising the protein of interest and a thermostable antibiotic resistance reporter, in such a way that thermostable mutants provide increased resistance in a thermophile. We isolated thermostable mutants of three human interferons and of two enzymes to demonstrate the applicability of the system.

Interferon-beta: Mechanism of action and dosing issues

In patients with multiple sclerosis (MS), activation of immune cells and breakdown of the blood-brain barrier (BBB) lead to demyelination and axon injury. Although repairing damage to neurons is not possible, immunomodulating therapies can reduce the inflammatory processes that lead to demyelination. Interferon-beta (IFN-beta) is a polypeptide, normally produced by fibroblasts, that has antiviral and antiproliferative effects. Binding of IFN-beta to its receptor induces a complex transcriptional response. In immune cells (the most likely target of IFN-beta's therapeutic effect in MS), IFN-beta reduces antigen presentation and T-cell proliferation, alters cytokine and matrix metalloproteinase (MMP) expression, and restores suppressor function. Therapeutic forms of IFN-beta can be produced in bacterial expression systems (IFN-beta1b) or in mammalian cells (IFN-beta1a). These forms have some differences in their amino acid sequence and posttranslational modifications, but the transcriptional response to IFN- beta1b and IFN-beta1a appears to be similar, if not indistinguishable. However, the biological response and the clinical effect do vary with changes in the dosing frequency of IFN-beta. In clinical trials, IFN-beta1a IM administered weekly elicits a transient biological response compared to IFN-beta1b administered SC every other day or IFN-beta1a (administered SC three times per week). Comparative clinical trials suggest that the differences in the biological response are clinically meaningful: more frequent IFN-beta administration produces superior clinical responses.

N-terminally PEGylated human interferon-beta-1a with improved pharmacokinetic properties and in vivo efficacy in a melanoma angiogenesis model

PEGylation of IFN-alpha has been used successfully to improve the pharmacokinetic properties and efficacy of the drug. To prepare a PEGylated form of human interferon-beta-1a (IFN-beta-1a) suitable for testing in vivo, we have synthesized 20 kDa mPEG-O-2-methylpropionaldehyde and used it to modify the N-terminal alpha-amino group of the cytokine. The PEGylated protein retained approximately 50% of the activity of the unmodified protein and had significantly improved pharmacokinetic properties following intravenous administration in rats. The clearance and volume of distribution at steady state were reduced approximately 30-fold and approximately 4-fold, respectively, resulting in a significant increase in systemic exposure as determined by the area under the curve. The elimination half-life of the PEGylated protein was approximately 13-fold greater than for the unmodified protein. The unmodified and PEGylated proteins were tested for their ability to inhibit the formation of radially oriented blood vessels entering the periphery of human SK-MEL-1 melanoma tumors in athymic nude homozygous (nu/nu) mice. In a single dose comparison study, administration of 1 x 10(6) units of unmodified IFN-beta-1a resulted in a 29% reduction in vessel number, while 1 x 10(6) units of PEGylated IFN-beta-1a resulted in a 58% reduction. Both treatments resulted in statistically significant reductions in mean vessel number as compared to the vehicle (control)-treated mice, with the PEGylated IFN-beta-1a-treated mice showing a statistically significantly greater reduction in mean vessel number as compared to the unmodified IFN-beta-1a-treated mice. In a multiple versus single dose comparison study, daily administration of 1 x 10(6) units of unmodified IFN-beta-1a for 9 days resulted in a 51% reduction in vessel number, while a single dose of 1 x 10(6) units of the PEGylated protein resulted in a 66% reduction. Both treatments resulted in statistically significant reductions in mean vessel number as compared to the vehicle-treated mice, with the PEGylated IFN-beta-1a-treated mice showing a statistically significantly greater reduction in mean vessel number as compared to the unmodified IFN-beta-1a-treated mice. Therefore, the improved pharmacokinetic properties of the modified protein translated into improved efficacy. Since unmodified IFN-beta is used for the treatment of multiple sclerosis and hepatitis C virus infection, a PEGylated form of the protein such as 20 kDa mPEG-O-2-methylpropionaldehyde-modified IFN-beta-1a may serve as a useful adjunct for the treatment of these diseases. In addition, the antiangiogenic effects of PEGylated IFN-beta-1a may be harnessed for the treatment of certain cancers, either as a sole agent or in combination with other antitumor drugs.

N-glycosylation of murine IFN-beta in a putative receptor-binding region

Human and mouse genomes contain more than 20 related genes encoding diverse type I interferons (IFNs- alpha/beta), cytokines that are crucial for resistance of organisms against viral infections. Although the amino acid sequences of various IFN-alpha/beta subtypes differ markedly, they are all considered to share a common three-dimensional structure and to bind the same heterodimeric receptor, composed of the IFNAR-1 and IFNAR-2 subunits. Analysis of available mammalian IFN-beta sequences showed that they all carry 1 to 5 predicted N-glycosylation sites. Murine IFN-beta contains three predicted N-glycosylation sites (Asn29, Asn69, Asn76), one of which (Asn29) is located in the AB loop, in a region predicted to interact with the type I IFN receptor. The aim of this work was to test if this site is indeed N-glycosylated and if this glycosylation would affect IFN antiviral activity. We showed that all three N-glycosylation sites predicted from the sequence, including Asn29, carry N-linked sugars. Mutation of individual N-glycosylation sites had a weak negative influence on IFN antiviral activity. In contrast, the complete loss of glycosylation dramatically decreased activity. Our data suggest that interaction of murine IFN-beta with the IFNAR could locally differ from that of human IFN-alpha2 and human IFN-beta.

Glycation of interferon-beta-1b and human serum albumin in a lyophilized glucose formulation. Part III: application of proteomic analysis to the manufacture of biological drugs

Glycation of interferon-beta-1b and human serum albumin was identified in a lyophilized glucose formulation by a sensitive LC-MS approach. The extent of glycation was measured by a label-free quantitation strategy. The glycation sites were determined by the accurate mass (FTICR MS) with MS/MS measurements on the corresponding tryptic peptides. The extent of glycation was measured by the ratio of the peak intensity between the glycated and the average value for three non-glycated peptides in the same run. Residues lysine 18 of interferon-beta-1b, and lysine 51, lysine 233, and lysine 545 of human serum albumin were more prone to be glycated than other sites in this lyophilized glucose formulation. Residues of lysine 51 and lysine 233 but not lysine 545 of human serum albumin are highly accessible to solvent as found in a solution storage study by Lapolla et al. The extent of glycation of both proteins and the number of glycation sites of human serum albumin were increased with the storage time at 25 degrees C. In total, two glycation sites of interferon beta-1b and 17 glycation sites of human serum albumin were identified in the lyophilized glucose formulation with a storage time at 25 degrees C of 35 days. Among the 17 glycation sites, only lysine 525 of human serum albumin has been found in vivo in diabetic patients by Shaklai et al. As expected, there was no glycation found on both interferon-beta-1b and human serum albumin in the control samples (similar lyophilized formulation but using mannitol instead of glucose).

Structure−Function Engineering of Interferon-β-1b for Improving Stability, Solubility, Potency, Immunogenicity, and Pharmacokinetic Properties by Site-Selective Mono-PEGylation

Recombinant interferon-beta-1b (IFN-beta-1b) is used clinically in the treatment of multiple sclerosis. In common with many biological ligands, IFN-beta-1b exhibits a relatively short serum half-life, and bioavailability may be further diminished by neutralizing antibodies. While PEGylation is an approach commonly employed to increase the blood residency time of protein therapeutics, there is a further requisite for molecular engineering approaches to also address the stability, solubility, aggregation, immunogenicity and in vivo exposure of therapeutic proteins. We investigated these five parameters of recombinant human IFN-beta-1b in over 20 site-selective mono-PEGylated or multi-PEGylated IFN-beta-1b bioconjugates. Primary amines were modified by single or multiple attachments of poly(ethylene glycol), either site-specifically at the N-terminus, or randomly on the 11 lysines. In two alternate approaches, site-directed mutagenesis was independently employed in the construction of designed IFN-beta-1b variants containing either a single free cysteine or lysine for site-specific PEGylation. Optimization of conjugate preparation with 12 kDa, 20 kDa, 30 kDa, and 40 kDa amine-selective PEG polymers was achieved, and a comparison of the structural and functional properties of the IFN-beta-1b proteins and their PEGylated counterparts was conducted. Peptide mapping and MALDI-TOF mass spectrometric analysis confirmed the attachment sites of the PEG polymer. Independent biochemical and bioactivity analyses, including antiviral and antiproliferation bioassays, circular dichroism, capillary electrophoresis, flow cytometric profiling, reversed phase and size exclusion HPLC, and immunoassays demonstrated that the functional activities of the designed IFN-beta-1b conjugates were maintained, while the formation of soluble or insoluble aggregates of IFN-beta-1b was ameliorated. Immunogenicity and pharmacokinetic studies of selected PEGylated IFN-beta-1b compounds in mice and rats demonstrated both diminished IgG responses, and over 100-fold expanded AUC exposure relative to the unmodified protein. The results demonstrate the capacity of this macromolecular engineering strategy to address both pharmacological and formulation challenges for a highly hydrophobic, aggregation-prone protein. The properties of a lead mono-PEGylated candidate, 40 kDa PEG2-IFN-beta-1b, were further investigated in formulation optimization and biological studies.

Linear and Branched Bicin Linkers for Releasable PEGylation of Macromolecules: Controlled Release in Vivo and in Vitro from Mono- and Multi-PEGylated Proteins

The utility of PEGylation for improving therapeutic protein pharmacology would be substantially expanded if the authentic protein drugs could be regenerated in vivo. Diminution of kinetic constants of both enzymes and protein ligands are commonly encountered following permanent bioconjugation with poly(ethylene glycol) polymers. In further development of releasable linker technology, we investigated an amino PEG anchimeric prodrug system, based on either the linear or branched bicin3 (BCN3) linkage, one promising representative of several aliphatic ester structures synthesized from N-modifed bis-2-hydroxyethylglycinamide (bicin). Protein models included an enzyme, lysozyme, and a receptor ligand, interferon-beta-1b, for preparation of linear or branched mono- and multi-PEGylated conjugates as inactive PEG-BCN3 prodrugs. The kinetics of protein release, both in plasma (in vitro) and in mice (in vivo), correlated with the number of PEG attachments, and the plasma half-lives of PEG release spanned a duration of hours to days within the therapeutically relevant window. Capillary electrophoresis, SDS-PAGE, mass determination, and enzymatic and antiviral activity determinations demonstrated regeneration of equivalent native proteins from the inactive PEG-BCN3 conjugates. Pharmacokinetic analysis of the PEGylated interferon-beta-1b administered subcutaneously in mice demonstrated an over 20-fold expansion of the area under the curve exposure of bioactive protein when compared to native protein.

Correlations between scaffold/matrix attachment region (S/MAR) binding activity and DNA duplex destabilization energy

Scaffold or matrix-attachment regions (S/MARs) are thought to be involved in the organization of eukaryotic chromosomes and in the regulation of several DNA functions. Their characteristics are conserved between plants and humans, and a variety of biological activities have been associated with them. The identification of S/MARs within genomic sequences has proved to be unexpectedly difficult, as they do not appear to have consensus sequences or sequence motifs associated with them. We have shown that S/MARs do share a characteristic structural property, they have a markedly high predicted propensity to undergo strand separation when placed under negative superhelical tension. This result agrees with experimental observations, that S/MARs contain base-unpairing regions (BURs). Here, we perform a quantitative evaluation of the association between the ease of stress-induced DNA duplex destabilization (SIDD) and S/MAR binding activity. We first use synthetic oligomers to investigate how the arrangement of localized unpairing elements within a base-unpairing region affects S/MAR binding. The organizational properties found in this way are applied to the investigation of correlations between specific measures of stress-induced duplex destabilization and the binding properties of naturally occurring S/MARs. For this purpose, we analyze S/MAR and non-S/MAR elements that have been derived from the human genome or from the tobacco genome. We find that S/MARs exhibit long regions of extensive destabilization. Moreover, quantitative measures of the SIDD attributes of these fragments calculated under uniform conditions are found to correlate very highly (r2>0.8) with their experimentally measured S/MAR-binding strengths. These results suggest that duplex destabilization may be involved in the mechanisms by which S/MARs function. They suggest also that SIDD properties may be incorporated into an improved computational strategy to search genomic DNA sequences for sites having the necessary attributes to function as S/MARs, and even to estimate their relative binding strengths.

Biological standardization of human interferon beta: establishment of a replacement world health organization international biological standard for human glycosylated interferon beta

Human interferon beta (IFN-beta) has been developed as a major biotherapeutic agent for the treatment of multiple sclerosis. Since World Health Organization (WHO) international standards (IS) for IFN-beta were established several years prior to the development of clinical grade IFN-beta products, a number of scientific issues with regard to the biological standardisation of natural and recombinant IFN-beta products have emerged. In order to address these issues, an international collaborative study to evaluate WHO IS and candidate international standards (CIS) of IFN-beta was instigated by the National Institute for Biological Standards and Control (NIBSC) in 2000 and was carried out in the succeeding year. Sixteen expert laboratories from 8 countries worldwide participated in the study. They performed titrations on 8 different IFN-beta preparations, including IS and new CIS, in a variety of mainly antiviral- but also including some antiproliferative- and reporter gene-assays, and contributed raw data from these assays to NIBSC for statistical analysis and calculation of potencies. While both intra- and inter-laboratory variation of potency estimates was evident, overall validity of the study as a whole was clearly shown by comparison of two pairs of internal coded duplicates, which gave the expected relative potency of 1 and the lowest inter-laboratory variability of potency estimates in all assay types. The CIS containing Chinese hamster ovary (CHO) cell- or human fibroblast-derived, glycosylated, IFN-beta gave similar low inter-laboratory variation in potency estimates one to another as the coded duplicates, which was significantly less than to the 2nd WHO IS of IFN-beta, human fibroblast-derived, Gb23-902-531. One of these CIS, designated 00/572, containing CHO cell-derived IFN-beta and formulated with both bovine casein and human serum albumin, could be assigned a potency, consistent for all assay types, of 40,000 international units (IU) per ampoule relative to the IU of the 2nd IS of IFN-beta, Gb23-902-531. Other CIS containing glycosylated IFN-beta, either CHO cell- or human-fibroblast-derived, could also be assigned potency values that were continuous with the IU of Gb23-902-531 and 00/572. However, greater inter-laboratory variations in estimates were evident from comparisons of Gb23-902-531 or 00/572 with either the 1st IS for E. coli-derived, non-glycosylated, IFN-beta with serine substitution at position 17 (IFN-beta Ser 17 mutein), Gxb02-901-535, or with a CIS (00/574) containing IFN-beta Ser 17 mutein. Indeed, variations in potency estimates for preparations containing IFN-beta Ser 17 mutein were sufficiently large to indicate that assays could distinguish preparations of IFN-beta Ser 17 mutein from preparations of glycosylated IFN-beta. Thus, neither the 2nd IS of IFN-beta, Gb23-902-531, containing fibroblast-derived IFN-beta, nor CIS, 00/572, containing CHO cell-derived IFN-beta, was appropriate for standardisation of preparations of IFN-beta Ser 17 mutein. Conversely, neither the IS of IFN-beta Ser 17 mutein, Gxb02-901-535, or a CIS of IFN-beta Ser 17 mutein, 00/574, was appropriate for the standardisation of preparations of glycosylated IFN-beta. CIS 00/572, containing CHO cell-derived, glycosylated IFN-beta, was clearly shown to be suitable to serve as a primary standard for glycosylated forms of IFN-beta, especially clinical grade IFN-beta-1a products. It was further shown to exhibit high thermal and long-term stability. Since the CHO cell-derived IFN-beta used for preparation of 00/572 was of a greater purity than the IFN-beta used for the 2nd IS of IFN-beta, Gb23-902-531, it was recommended by the WHO Informal Consultation on the Standardisation of Cytokines, Growth Factors and Other Endocrinological Substances, which met in October 2003, that 00/572 should replace Gb23-902-531 as the IS for glycosylated IFN-beta. This recommendation was accepted by the WHO Expert Committee on Biological Standardization (ECBS) at its annual meeting in November 2003 and 00/572 was established as the 3rd IS for human glycosylated IFN-beta with an assigned potency of 40,000 IU. As this study identified no advantage to replacing the existing 1st IS for IFN-beta Ser 17 mutein, Gxb02-901-535, WHO ECBS accepted that this should continue to serve as the IS for this material.

Solution Behavior of IFN-β-1a: An Empirical Phase Diagram Based Approach

An empirical phase diagram approach has been developed as a practical tool to aid macromolecular preformulation/formulation studies. This method employs an eigenvector based procedure to visualize and interpret complex data sets. Human Inteferon-beta-1a, an important therapeutic protein, was used to further develop the method and test its utility. The protein was characterized in solution as a function of pH (2-8), temperature (10 degrees C-85 degrees C) and ionic strength (I = 0.1 and 1.0) using intrinsic and ANS fluorescence, Far-UV circular dichroism (Far-UV CD), Fourier Transform Infrared spectroscopy (FTIR) and derivative UV absorbance spectroscopies, as well as differential scanning calorimetry (DSC) to supplement spectroscopic thermal stability studies. Derivative UV absorbance data were initially used to construct a pH-temperature phase diagram at each ionic strength. Three distinctive phases at I = 0.1 and two major phases at I = 1.0 were identified corresponding to different conformation/aggregation states of the protein. For the first time, heterogeneous data sets (i.e., data from different techniques) including Far-UV CD, fluorescence and UV absorbance results were used to generate empirical phase diagrams. Results from different data sets are compared; precautions in applying the method and its overall utility are discussed.

Crystal structure of ATF-2/c-Jun and IRF-3 bound to the interferon-beta enhancer

Transcriptional activation of the interferon-beta (IFN-beta) gene requires assembly of an enhanceosome containing the transcription factors ATF-2/c-Jun, IRF-3/IRF-7, NF-kappaB and HMGI(Y). These factors cooperatively bind a composite DNA site and activate expression of the IFN-beta gene. The 3.0 A crystal structure of the DNA-binding domains of ATF-2/c-Jun and two IRF-3 molecules in a complex with 31 base pairs (bp) of the PRDIV-PRDIII region of the IFN-beta enhancer shows that association of the four proteins with DNA creates a continuous surface for the recognition of 24 bp. The structure, together with in vitro binding studies and protein mutagenesis, shows that protein-protein interactions are not critical for cooperative binding. Instead, cooperativity arises mainly through nucleotide sequence-dependent structural changes in the DNA that allow formation of complementary DNA conformations. Because the binding sites overlap on the enhancer, the unit of recognition is the entire nucleotide sequence, not the individual subsites.

Interaction of three β-interferon domains with liposomes and monolayers as model membranes

The physicochemical properties of three peptides belonging to the beta-interferon (beta-IFN) molecule, -beta-IFN(13-20), beta-IFN(40-47) and beta-IFN(109-116)-, which have been described to be antigenic epitopes of the neutralising antibodies responsible of the failure of the Multiple Sclerosis therapy, and their palmitoylated derivatives were analysed. Peptides were synthesised by solid-phase methodologies and characterized by amino acid analysis, analytical high-performance liquid chromatography and electrospray mass spectrometry. The activity of free and derivatized peptides was determined. In order to know how the synthesised peptides were able to interact with membrane models, studies of kinetics of penetration at constant area and compression isotherms were carried out. Moreover, differential scanning calorimetry (DSC) was used to investigate the thermotropic phase properties of binary mixtures of dipalmitoylphosphatidylcholine (DPPC) or dipalmitoylphosphatidylglicerol (DPPG) with the peptides.

What do we know about the mechanism of action of disease-modifying treatments in MS?

Multiple sclerosis (MS), a chronic inflammatory disorder of the central nervous system (CNS), 2 results in damage to axons and their surrounding myelin sheath. The exact cause of inflammation remains unclear, but an autoimmune response directed against CNS antigens is suspected. MS can affect the brain, optic nerve and spinal cord, thus causing many neurological symptoms. These can include limb numbness or weakness, sensory or motor changes, ataxia, blurry vision, painful eye movements, bladder and bowel dysfunction, decreased memory, fatigue and effective disorders. This article will include a concise overview of the pathogenesis of MS in order to set the stage for subsequent discussion of the mechanisms of action of disease-modifying treatments, and whether these should influence our treatment choices. Although the exact pathogenesis of MS is not fully understood, current knowledge has already led to the development of effective treatments, namely interferon (IFN) 3 and glatiramer acetate, both of which have been shown to reduce relapse rates, while IFN 3- 1 a also reduces confirmed disability progression. Further increases in our understanding of the pathogenesis of MS are likely to assist in the identification of new targets for disease-modifying therapies and in the optimisation of current treatments..

Activity of hybrid type I interferons in cells lacking Tyk2: a common region of IFN-alpha 8 induces a response, but IFN-alpha2/8 hybrids can behave like IFN-beta

Type I interferons (IFNs) are a family of pleiotropic cytokines with antiviral, antiproliferative, and immunomodulatory properties. The type I IFN family consists of 12 IFN-alpha subtypes, IFN-beta, and IFN-omega. Cells lacking the receptor-associated protein kinase Tyk2 (U1A) are responsive only to IFN-beta and partially to IFN-alpha8. We constructed a series of IFN-alpha2/alpha8 hybrids and mutants and identified the region within IFN-alpha8 responsible for its activity in Tyk2-deficient cells. The same domain mediates the interactions between IFN and IFN-alpha receptor (IFNAR) in Tyk2-complemented and Tyk2-deficient cells (U1A). The presence or absence of Tyk2 altered the inhibitory effects of anti-IFNAR antibodies, suggesting that the IFN-alpha binding domain on IFNAR is altered by the presence of Tyk2. The activity of IFN-beta was not significantly affected by the deletion of Tyk2, and, surprisingly, one of our IFN-alpha2/alpha8 hybrids (IFN-alpha288) behaved like IFN-beta in a number of assays that distinguish IFN-alphas from IFN-beta. This suggests that this hybrid mimics the interactions of IFN-beta with the receptor and also suggests the existence of a distinct binding site(s) on IFNAR for IFN-beta and some hybrid IFN-alphas.

Optimizing the Binding Affinity of a Carrier Protein

Prolonging the circulatory half-life of low mass protein drugs can be achieved either by administration of a pro-drug or through co-injection with a carrier protein that will slowly release the active protein. The rate of release is concentration and affinity dependent. The optimal relationship between these two in prolonging the half-life of a pro-drug is the focus of this work. Interferon (IFN) beta is one of the most widely used protein drugs in the clinic. Here, we show that the circulatory half-life of IFNbeta can be significantly extended by co-administration with the extracellular domain of the IFN receptor ifnar2 (ifnar2-EC). To investigate the concentration/affinity relation, a range of tighter binding ifnar2-EC mutants was designed that bind IFNbeta, but not IFNalpha2, up to 50-fold tighter compared with the wild-type ifnar2-EC. This increased affinity is related to a slower dissociation rate, whereas the association of IFNbeta with ifnar2-EC is already near optimum. Using the wild-type and mutant receptors, we investigated their potential in occluding IFNbeta from circulation in a tissue culture assay, as well as in rats. To determine the potential of ifnar2-EC as a carrier protein, we co-administered a mixture of IFNbeta and ifnar2-EC to rats both intravenously and subcutaneously, and followed the blood plasma concentrations of IFNbeta over time. The tighter binding ifnar2-EC mutant had a clear advantage in prolonging the half-life of IFNbeta in circulation, even when lower protein concentrations were administered. A numerical simulation of the in vivo data demonstrates that the optimal binding affinity of a carrier protein is around the concentration needed to obtain optimal activity of the ligand.

Spotlight on Interferon-??-1b in Relapsing-Remitting and Secondary Progressive Multiple Sclerosis1

Interferon-beta-1b (Betaseron, Betaferon) is a non-glycosylated recombinant human interferon-beta approved for high-frequency, subcutaneous (SC) administration in the treatment of multiple sclerosis (MS). Its mechanism of action is unknown, but may involve modulation of the autoimmune pathogenic processes of MS. In a randomized, double-blind trial in patients with relapsing-remitting MS (RRMS), SC interferon-beta-1b 250 micro g (8 million International Units [MIU]) every other day reduced the annual relapse rate and increased the proportion of relapse-free patients compared with placebo. It also reduced relapse severity, hospitalizations, and disease activity assessed by magnetic resonance imaging (MRI), and increased the time to first relapse. Progression of disability showed a trend towards reduction relative to placebo and baseline, but did not reach statistical significance. SC interferon-beta-1b 250 micro g every other day was shown in a randomized trial to be superior to intramuscular (IM) interferon-beta-1a 30 micro g (6 MIU) once weekly with respect to reductions in relapse-related parameters, disability progression and MRI-assessed disease activity. In patients with secondary progressive MS (SPMS), SC interferon-beta-1b 250 micro g every other day slowed progression of the disease relative to placebo in one randomized, double-blind trial, but not in another. In both studies, interferon-beta-1b 250 micro g recipients had fewer relapses and less MRI-assessed disease activity than placebo recipients. The difference in primary outcome may reflect differences in patient entry criteria. Interferon-beta-1b is generally well tolerated and the common adverse events (e.g. injection site reactions, asthenia and an influenza-like symptom complex) are clinically manageable. In a randomized trial, the tolerability of SC interferon-beta-1b 250 micro g every other day was generally similar to that of IM interferon-beta-1a 30 micro g once weekly, except for higher incidences of injection site reactions and neutralizing anti-interferon-beta antibodies with SC interferon-beta-1b. In conclusion, SC interferon-beta-1b 250 micro g every other day reduces the frequency and severity of relapses and MRI measures of disease activity and may delay the progression of disability in RRMS. The drug appeared to be more effective than, and as well tolerated as, IM interferon-beta-1a 30 micro g once weekly. Interferon-beta-1b also has positive effects on relapse rates and disease activity in patients with SPMS, although its effects on disease progression remain uncertain. The drug is generally well tolerated, and the common adverse events are clinically manageable. Thus, interferon-beta-1b is a valuable first-line therapy for patients with RRMS and a potentially useful option in those with SPMS.

Expression and characterization of human interferon-beta1 in the methylotrophic yeast Pichia pastoris

We describe the heterologous expression of a human interferon-beta1 in the methylotrophic yeast Pichia pastoris. Biologically active recombinant human interferon-beta1 (rHuIFN-beta1) was secreted from shake-flask-grown P. pastoris cells into the medium using the Saccharomyces cerevisiae alpha-mating factor prepro-leader sequence at the level of (1-3) x 10(5) i.u. (international units)/ml (6-12 mg/litre). An rHuIFN-beta1 with an N-terminal sequence identical with that of native HuIFN-beta1 was purified and the specific activity was determined (2-3 x 10(7) i.u./mg). It was found that the secreted recombinant protein was partially N-glycosylated.

N-linked glycan structures of mouse interferon-β produced by Bombyx mori larvae

The full-length mouse interferon-beta (mIFN-beta) cDNA, including the secretion signal peptide coding region under control of the polyhedrin promoter, was introduced into Bombyx mori nucleopolyhedrovirus (BmNPV). Recombinant mIFN-beta (rmIFN-beta) was accumulated in the haemolymph of infected silkworm larvae. Western blot analysis showed isoforms of rmIFN-beta, suggesting that rmIFN-beta is glycosylated. The glycan structures of purified rmIFN-beta were determined. The N-glycans were liberated by hydrazinolysis and the resulting oligosaccharides were labeled with 2-aminopyridine. The pyridylaminated (PA) glycans were purified by gel filtration, reversed-phase HPLC, and size-fractionation HPLC. The structures of the PA-sugar chains were identified by a combination of two-dimensional PA-sugar chain mapping, MS analysis, and exoglycosidase digestions.

Gelatinase B/matrix metalloproteinase-9 cleaves interferon-beta and is a target for immunotherapy

Parenteral administration of interferon (IFN)-beta is one of the currently approved therapies for multiple sclerosis. One characteristic of this disease is the increased production of gelatinase B, also called matrix metalloproteinase (MMP) 9. Gelatinase B is capable of destroying the blood-brain barrier, and of cleaving myelin basic protein into immunodominant and encephalitogenic fragments, thus playing a functional role and being a therapeutic target in multiple sclerosis. Here we demonstrate that gelatinase B proteolytically cleaves IFN-beta, kills its activity, and hence counteracts this cytokine as an antiviral and immunotherapeutic agent. This proteolysis is more pronounced with IFN-beta-1b than with IFN-beta-1a. Furthermore, the tetracycline minocycline, which has a known blocking effect in experimental autoimmune encephalomyelitis, an in vivo model of acute inflammation in multiple sclerosis, and other MMP inhibitors prevent the in vitro degradation of IFN-beta by gelatinase B. These data provide a novel mechanism and rationale for the inhibition of gelatinase B in diseases in which IFN-beta has a beneficial effect. The combination of gelatinase B inhibitors with better and lower pharmacological formulations of IFN-beta may reduce the side-effects of treatment with IFN-beta, and is therefore proposed for multiple sclerosis therapy and the immunotherapy of viral infections.

A peptide mimetic of human interferon (IFN)-beta

Type I interferons (IFNs) are cytokines that are used clinically as antiviral and antitumour agents. The interaction of IFNs with their heterodimeric type I IFN receptor comprised of IFNAR1 and IFNAR2 is a first step to inducing biological actions. Here, we describe the successful mimicry of IFN-beta by a peptide isolated by phage-display screening using a neutralizing anti-IFN-beta monoclonal antibody. The 15-mer peptide, designated SYR6, was shown to compete with IFN-beta for binding to type I IFN receptor in a concentration-dependent manner, and was shown to elicit antiviral activity on cultured cells. This antiviral activity was not eliminated in the presence of neutralizing monoclonal antibodies to IFN-alpha, -beta and -gamma, and a low concentration of soluble type I IFN receptor, suggesting that it was not due to IFN contamination or the induction of endogenous IFNs by SYR6. This peptide might be a potent agonist to provide a mechanism of activating heterodimeric cytokine receptors.

Transcription factor YY1 binds to the murine beta interferon promoter and regulates its transcriptional capacity with a dual activator/repressor role

The induction of the beta interferon (IFN-beta) gene constitutes one of the first responses of the cell to virus infection. Its regulation is achieved through an intricate combination of virus-induced binding of transcription factors and local chromatin remodeling. In this work, we demonstrate that transcription factor YY1, known to interact with histone deacetylases (HDAC) and histone acetyltransferases, has a dual activator/repressor role during the regulation of the IFN-beta promoter activity. We show that YY1 specifically binds in vitro and in vivo to the murine IFN-beta promoter at positions -90 and -122. Overexpression of YY1 strongly repressed the transcriptional capacity of a stably integrated IFN-beta promoter fused to a chloramphenicol acetyltransferase reporter gene as well as the endogenous IFN activity of murine L929 cells via an HDAC activity. Stably integrated IFN-beta promoters mutated at the -90 site were no longer repressed by YY1, could no longer be activated by trichostatin A, displayed a retarded postinduction turn off, and a reduced virus-induced activity. Introduction of a mutation at the -122 site did not affect YY1-induced repression, but promoters with this mutation displayed a reduced virus-induced activity. Stably integrated full-length promoters (from position -330 to +20) mutated at both YY1-binding sites displayed extremely reduced promoter activities. We conclude that YY1 has a dual activator/repressor role on IFN-beta promoter activity depending on its binding site and time after infection.

Computational and in vitro analysis of destabilized DNA regions in the interferon gene cluster: potential of predicting functional gene domains

Recent evidence adds support to a traditional concept according to which the eukaryotic nucleus is organized into functional domains by scaffold or matrix attachment regions (S/MARs). These regions have previously been predicted to have a high potential for stress-induced duplex destabilization (SIDD). Here we report the parallel results of binding (reassociation) and computational SIDD analyses for regions within the human interferon gene cluster on the short arm of chromosome 9 (9p22). To verify and further refine the biomathematical methods, we focus on a 10 kb region in the cluster with the pseudogene IFNWP18 and the interferon alpha genes IFNA10 and IFNA7. In a series of S/MAR binding assays, we investigate the promoter and termination regions and additional attachment sequences that were detected in the SIDD profile. The promoters of the IFNA10 and the IFNA7 genes have a moderate approximately 20% binding affinity to the nuclear matrix; the termination sequences show stronger association (70-80%) under our standardized conditions. No comparable destabilized elements were detected flanking the IFNWP18 pseudogene, suggesting that selective pressure acts on the physicochemical properties detected here. In extended, noncoding regions a striking periodicity is found of rather restricted SIDD minima with scaffold binding potential. By various criteria, the underlying sequences represent a new class of S/MARs, thought to be involved in a higher level organization of the genome. Together, these data emphasize the relevance of SIDD calculations as a valid approach for the localization of structural, regulatory, and coding regions in the eukaryotic genome.

Application of the StrOligo algorithm for the automated structure assignment of complex N-linked glycans from glycoproteins using tandem mass spectrometry

Oligosaccharides associated with proteins are known to give these molecules specific conformations and functions. Analysis of proteins would not be complete without studying the glycans. However, high-throughput techniques in proteomics will soon overwhelm the current capacity of methods if no automation is incorporated into glycomics. New capabilities of the StrOligo algorithm introduced for this purpose (Ethier et al., Rapid Commun. Mass Spectrom., 2002; 16: 1743) will be discussed here. Experimental tandem mass spectra were acquired to test the algorithm using a hybrid quadrupole-time-of-flight (QqTOF) instrument with a matrix-assisted laser desorption/ionization (MALDI) source. The samples were N-linked oligosaccharides from monoclonal antibody IgG, beta interferon and fetuin, detached by enzymatic deglycosylation and labeled at the reducing end. Improvements to the program were made in order to reduce the need for user intervention. StrOligo strips the spectra down to monoisotopic peaks only. The algorithm first builds a relationship tree, accounting for each observed loss of a monosaccharide moiety, and then analyzes the tree and proposes possible structures from combinations of adducts and fragment ion types. A score, which reflects agreement with experimental results, is then given to each proposed structure. The program then decides which combination is the best one and labels relevant peaks in the experimental mass spectrum using a modified nomenclature. The usefulness of the algorithm has been demonstrated by assigning structures to several glycans released from glycoproteins. The analysis was completed in less than 2 minutes for any glycan, which is a substantial improvement over manual interpretation.

The x-ray crystal structure of the NF-kappa B p50.p65 heterodimer bound to the interferon beta -kappa B site

We have determined the x-ray crystal structure of the transcription factor NF-kappaB p50.p65 heterodimer complexed to kappaB DNA from the cytokine interferon beta enhancer (IFNbeta-kappaB). To better understand how the binding modes of NF-kappaB on its two best studied DNA targets might contribute to promoter-specific transcription, this structure is compared with the previously determined complex crystal structure containing NF-kappaB bound to the Ig kappa light chain gene enhancer as well as to a second NF-kappaB.Ig kappa light chain gene enhancer complex also reported in this paper. The global binding modes of all NF-kappaB.DNA complex structures are similar, although crystal-packing interactions lead to differences between identical complexes of the same crystallographic asymmetric unit. An extensive network of stacked amino acid side chains that contribute to base-specific DNA contacts is conserved among the three complexes. Consistent with earlier reports, however, the IFNbeta-kappaB DNA is bent significantly less by NF-kappaB than is the Ig kappa light chain gene enhancer. This and other small structural changes may play a role in explaining why NF-kappaB-directed transcription is sensitive to the context of specific promoters. The precise molecular mechanism behind the involvement of the high mobility group protein I(Y) in interferon beta enhanceosome formation remains elusive.

Mapping of IFN-beta epitopes important for receptor binding and biologic activation: comparison of results achieved using antibody-based methods and alanine substitution mutagenesis

The epitopes important for receptor binding and activation of human interferon-beta1a (IFN-beta1a) were mapped with monoclonal antibodies (mAb), grouped on the basis of their specificity and ability to neutralize biologic activity, and alanine scanning mutagenesis (ASM). The binding properties of nine mAb were defined, using ASM-IFN-beta mutants having alanine substituted at targeted, surface-exposed residues. The results were correlated with the mAb neutralizing potency. Of six mAb that bound either at or adjacent to the IFNAR-2 receptor chain binding site defined by the ASM epitopes, only three had measurable neutralizing activity. Two of these inhibited IFN-beta/IFNAR-2 complex formation, suggesting that steric hindrance of receptor binding constitutes their mechanism of neutralization. However, two mAb that bound to sites remote from the IFNAR-2 binding site on IFN-beta also inhibited IFN-beta/IFNAR-2 complex formation and demonstrated potent neutralizing activity. Thus, neutralizing mAb may employ mechanisms other than steric blockade to inhibit directly the binding of receptor by cytokine, limiting their usefulness as tools to define precise receptor-ligand interaction sites.

Basic studies on gene therapy of human malignant melanoma by use of the human interferon beta gene entrapped in cationic multilamellar liposomes. 1. Morphology and growth rate of six melanoma cell lines used in transfection experiments with the human interferon beta gene

Six cell lines of human malignant melanoma: A375, A375.2, G361, HMV-1, MM8.1 and WM115 were seeded at densities of 1x10(4) cells/ml, 2 x 10(4) cells/ml or 3 x 10(4) cells/ml of RPMI medium supplemented with 10% fetal calf serum and antibiotics in a humidified atmosphere of 5% CO2 at 37 degrees C. A375 cells were also grown in Dulbecco's minimum Eagle's medium (DMEM medium). The morphology was studied by phase contrast light microscopy. At 4 days after seeding the colonies of A375 cells and HMV-1 cells were oval-shaped, the cells were polyhedrical and were making contact with each other regularly. The remaining cells were scattered, more elongated, and made contact randomly. G361 cells and MM8.1 cells tended to form superposed layers before 100% confluency was achieved. There were great differences in the growth rate and doubling time of melanoma cells. The doubling time in day 1 was short (around 6-12 h) in the case of A375, G361 and HMV-1 cells, longer (around 18 h) in the case of MM8.1 cells and very long (ranging between 26 and 89 h) for A375.2 and WM115 cells. There were also differences in the doubling time of cells as a function of the cell density at seeding. On the other hand, except for MM8.1 cells, there were differences between the doubling time in day 2 compared to day 1.

Characterization and humanization of a monoclonal antibody that neutralizes human leukocyte interferon: a candidate therapeutic for IDDM and SLE

We have developed a panel of murine monoclonal antibodies that recognize human interferon alpha. One of these mononclonal antibodies binds and neutralizes, with high affinity, all of seven tested recombinant human interferon alphas. This mononclonal antibody also neutralizes the interferon activity present in two independent pools of interferon alphas prepared following stimulation of human peripheral blood leukocytes. The complementary determining regions from this murine mononclonal antibody were transferred to a human IgG2 heavy chain and to a human kappa1 light chain. In addition, six (heavy chain) and two (light chain) amino acids were transferred from the framework regions. This generated a humanized mononclonal antibody that retained the specificity of the mouse parent. The humanized anti-interferon alpha antibody is a candidate therapeutic for those diseases, such as insulin-dependent diabetes, systemic lupus erythematosis, psoriasis and Crohn's disease, which are all characterized by pathological expression of interferon alpha.

Carboxyalkylated histidine is a pH-dependent product of pegylation with SC-PEG

PURPOSE

Pegylation of therapeutic protein usually results in a mixture of monopegylated proteins with differing sites of modification. With rh-interferon-alpha2A pegylation, we have found that this heterogeneity includes two classes of pegylation site chemistry, the relative proportions of which can be adjusted by reaction pH.

METHODS

The effect of pegylation reaction pH on the relative proportion of three peaks produced was investigated. Products were purified and characterized by peptide mapping, chemical stability to neutral hydroxylamine, and biologic activity.

RESULTS

Reactions at basic pH levels produced a mixture of products pegylated at lysine residues as has been observed elsewhere. However, the dominant product of reactions at mildly acidic levels of pH showed distinct chemistry and higher cytopathic effect activity. The primary site of modification at this pH was His34. We developed a quantitative assay using sensitivity to neutral hydroxylamine to measure the proportion of urethane bonds involving carboxyalkylated histidines. This assay showed that histidine was pegylated preferentially at low pH levels with another protein, rh-Interleukin-10.

CONCLUSIONS

Reaction pH can be used to select the preferred pegylation site chemistry.

Liver targeting of interferon-beta with a liver-affinity polysaccharide based on metal coordination in mice

Frequent and high-dose i.v. injections of interferon-beta (IFN-beta) have been used clinically to treat patients with viral hepatitis despite various side effects. Because side effects are caused by the systemic effects of IFN-beta, the purpose of this study was to target the drug specifically to the liver, thus reducing the adverse events. A chelating residue, diethylenetriaminepentaacetic acid (DTPA), was introduced to pullulan, a water-soluble polysaccharide with a high affinity for the liver. Murine IFN-beta could be coordinately conjugated with the DTPA-pullulan by simple mixing in an aqueous solution containing zinc ion (Zn2+). Intravenous injection of the IFN-beta-DTPA-pullulan conjugate with Zn2+ coordination enhanced liver induction of an antiviral enzyme, 2',5'-oligoadenylate synthetase (2-5AS), to a greater extent than that by free IFN-beta, although the 2-5AS levels in the liver depended on the mixing ratio of the IFN-beta/DTPA residue of DTPA-pullulan/Zn2+. In addition, the duration of the liver 2-5AS induction by the IFN-beta-DTPA-pullulan conjugate with Zn2+ coordination was longer than that by free IFN-beta. The liver targeting of IFN-beta by DTPA-pullulan with Zn2+ coordination may be a promising IFN therapy.

Improved pharmacokinetic properties of a polyethylene glycol-modified form of interferon-beta-1a with preserved in vitro bioactivity

Interferon therapies suffer from a relatively short half-life of the products in circulation. To address this issue we investigated the effects of polyethylene glycol modification (PEGylation) on the pharmacokinetic properties of human interferon (IFN)-beta-1a. PEGylation with a linear 20-kDa PEG targeted at a single site on the N-terminal amine had no deleterious effect on its specific activity in an in vitro antiviral assay. In monkeys, PEG IFN-beta-1a treatment induced neopterin and beta2-microglobulin expression (pharmacodynamic markers of activity). Systemic clearance values in monkeys, rats, and mice decreased, respectively, from 232, 261, and 247 ml/h/kg for the unmodified IFN-beta-1a to 30.5, 19.2, and 18.7 ml/h/kg for the PEGylated form, while volume of distribution values decreased from 427, 280, and 328 ml/kg to 284, 173, and 150 ml/kg. The decreased clearance and volume of distribution resulted in higher serum antiviral activity in the PEG IFN-beta-1a-treated animals. In the rat, a more extensive set of dosing routes was investigated, including intraperitoneal, intratracheal, and oral administration. Bioavailability for the PEG IFN-beta-1a was similar to the unmodified protein for each of the extravascular routes examined. For the intraperitoneal route, bioavailability was almost 100%, whereas for the oral and intratracheal routes absorption was low (<5%). In rats, subcutaneous bioavailability was moderate (28%), whereas in monkeys it was approximately 100%. In all instances an improved pharmacokinetic profile for the PEGylated IFN-beta-1a was observed. These findings demonstrate that PEGylation greatly alters the pharmacokinetic properties of IFN-beta-1a, resulting in an increase in systemic exposure following diverse routes of administration.

Antibodies to HIV-1 gp41 recognize synthetic peptides of human IFN-alpha and IFN-beta

Based on our finding that a common epitope exists between HIV-1 gp41 and human type I interferons (IFN-alpha and IFN-beta), and increased levels of antibodies against human IFN-alpha and IFN-beta were observed in HIV-1-infected individuals, we tried to explain the mechanism of increased levels of antibodies. Mouse antisera recognizing HIV-1 recombinant soluble (rs) gp41 (aa 539-684) interacted with two synthetic peptides sequence-corresponding to the IFN-alpha/beta receptor binding site on human IFN-alpha and IFN-beta, while normal mouse serum (pooled normal sera) did not. The anti-rspg41 antisera after adsorption by IFN-beta sepharose column lost the activity of interaction with both synthetic peptides. In another experiment, rsgp41 could bind to sepharose column conjugated with anti-IFN-beta polyclonal antibodies (IgG). These results indicate that the common epitope on gp41 and type I interferons could induce antibodies recognizing the receptor binding site on IFN-alpha and IFN-beta, suggesting that increased levels of antibodies against IFN-alpha and IFN-beta in HIV-1-infected individuals could be induced by gp41.

Structural analysis of modified forms of recombinant IFN-beta produced under stress-simulating conditions

The present study focused on the investigation of the chemical stability of recombinant human interferon-beta (rhIFN-beta) tested in vitro by chemical treatments that simulate stress-induced conditions that may occur during handling, storage or ageing of protein samples. Mild oxidation and/or alkylation of the recombinant protein showed that the four methionines occurring in the interferon displayed different chemical susceptibility in that Met36 and Met117 were fully modified, whereas Met1 showed only little modification and Met62 was completely resistant. Moreover, incubation of rhIFN-beta under alkaline conditions resulted in the formation of a covalent dimeric species stabilised by an intermolecular disulphide bridge involving the free SH group of Cys17 from each polypeptide chain. Analysis of biological activity of the different IFN-beta derivatives showed that rhIFN-beta fully retains its specific activity following mild oxidation treatments whereas reaction with a high concentration of alkylating agents or incubation under alkaline conditions strongly reduce its specific antiviral activity.

Mutational and structural analysis of the binding interface between type I interferons and their receptor Ifnar2

Type I interferons (IFN) exert pleiotropic activities through binding to two cell surface receptors, ifnar1 and ifnar2. We are investigating the biophysical basis of IFN signaling by characterizing the complex of the extra-cellular domain of ifnar2 (ifnar2-EC) with IFNs on the level of purified recombinant proteins in vitro. Here, we present a detailed mutational study on the functional epitopes on both IFN and ifnar2. Kinetic and thermodynamic parameters were determined by label-free heterogeneous phase detection. On IFNalpha2, a relatively small functional epitope comprising ten amino acid residues was localized, which is nearly entirely formed by residues on the AB loop. Two hot-spot residues, L30 and R33, account for two-thirds of the total interaction energy. Comparing the anti-viral potency of the various mutants to the binding affinity towards ifnar2 revealed a proportional correlation between the two, suggesting a rate-limiting role of ifnar2 binding in IFN signaling. On ifnar2, residues T46, I47 and M48 were identified as hot-spots in the interaction with IFNalpha2. For another ten residues on ifnar2, significant contribution of interaction energy was determined. Based on these data, the functional epitope on ifnar2 was defined according to a homology model based on other members of the class II hCR family in good agreement with the complementary functional epitope on IFNalpha2. Although IFNalpha2 and IFNbeta bind competitively to the same functional epitope, mutational analysis revealed distinct centers of binding for these IFNs on ifnar2. This small shift of the binding site may result in different angular orientation, which can be critically coupled to cytoplasmic signaling.

Characterization of a soluble ternary complex formed between human interferon-beta-1a and its receptor chains

The extracellular portions of the chains that comprise the human type I interferon receptor, IFNAR1 and IFNAR2, have been expressed and purified as recombinant soluble His-tagged proteins, and their interactions with each other and with human interferon-beta-1a (IFN-beta-1a) were studied by gel filtration and by cross-linking. By gel filtration, no stable binary complexes between IFN-beta-1a and IFNAR1, or between IFNAR1 and IFNAR2 were detected. However, a stable binary complex formed between IFN-beta-1a and IFNAR2. Analysis of binary complex formation using various molar excesses of IFN-beta-1a and IFNAR2 indicated that the complex had a 1:1 stoichiometry, and reducing SDS-PAGE of the binary complex treated with the cross-linking reagent dissucinimidyl glutarate (DSG) indicated that the major cross-linked species had an apparent Mr consistent with the sum of its two individual components. Gel filtration of a mixture of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the three proteins formed a stable ternary complex. Analysis of ternary complex formation using various molar excesses of IFNAR1 and the IFN-beta-1a/IFNAR2 complex indicated that the ternary complex had a 1:1:1 stoichiometry, and reducing SDS-PAGE of the ternary complex treated with DSG indicated that the major cross-linked species had an apparent Mr consistent with the sum of its three individual components. We conclude that the ternary complex forms by the sequential association of IFN-beta-1a with IFNAR2, followed by the association of IFNAR1 with the preformed binary complex. The ability to produce the IFN-beta-1a/IFNAR2 and IFN-beta-1a/IFNAR1/IFNAR2 complexes make them attractive candidates for X-ray crystallography studies aimed at determining the molecular interactions between IFN-beta-1a and its receptor.

[Anti-viral proteins: from interferon alpha to its receptor]

The immune response against viral pathogens include specific and non specific mechanisms. Cytokines are peptides which can play a role in the non specific immunity. Type I interferons (IFNalpha/beta) are the most effective antiviral cytokines. Interferons alpha are represented by a large familly of structurally related genes while the IFNbeta is encoded by a single gene. Type I interferon genes are located on the chromosome 9, and are segregated in a "modern" and an "ancestral" group with distinctive effects onto the cells. Type I interferons consist of 5 alpha helices, 4 of which are closely held together. Type I interferons receptor is a member of the class II cytokine receptor familly. It is a heterodimer composed of polypeptidic chains naimed IFNAR-1 and IFNAR-2. The type I interferons inducers are viruses, inactivated viruses and certain synthetic molecules. The molecular mechanisms of the induction of IFNbeta have been extensively described whereas the factors that play a role in the regulation of IFNalpha are not so well characterized. Two regulating domains located on the IFNbeta gene promotor are involved. The activation of these regulating domains leads to adverse effects by interacting with two intracellular factors (IRF1 and IRF2). IRF1 enhances the synthesis of IFNbeta but other pathways may be involved as well. The different IFNalpha sub-types have not only synergistic but also antagonistic effects. The synthesis of the different subtypes depends on cell lines and IFNalpha inducers. The N terminal part of IFNalpha is a major determinant in the diversity of the biological effects of IFNalpha sub-types which probably involve changes of the conformation of the type I receptor resulting from interactions between the receptor and its ligand. The type I interferons confer resistance to viruses, especially by enhancing the synthesis of intracellular antiviral proteins.

The structure of human interferon-beta: implications for activity

Interferons (IFNs) are potent extracellular protein mediators of host defence and homoeostasis. This article reviews the structure of human IFN-beta (HuIFN-beta), in particular in relation to its activity. The recently determined crystal structure of HuIFN-beta provides a framework for understanding of the mechanism of differentiation of type I IFNs by their common receptor. Insights are generated by comparison with the structures of other type I IFNs and from the interpretation of existing mutagenesis data. The details of the observed carbohydrate structure, together with biochemical data, implicate the glycosylation of HuIFN-beta, which is uncommon among type I IFNs, as an important factor in the solubility, stability and, consequently, activity of the protein. Finally, these structural implications are discussed in the context of the clinical use of HuIFN-beta.

Solution structure of the IRF-2 DNA-binding domain: a novel subgroup of the winged helix-turn-helix family

BACKGROUND

The transcription of interferon (IFN) and IFN-inducible genes is mainly regulated by the interferon regulatory factor (IRF) family of proteins, which recognize a unique AAGTGA hexamer repeat motif in the regulatory region of IFN genes. A DNA-binding domain of approximately 100 amino acids has been commonly found in the IRF family of proteins, but it has no sequence homology to known DNA-binding motifs. Elucidation of the structures of members of the IRF family is therefore useful to the understanding of the regulation and evolution of the immune system at the structural level.

RESULTS

The solution structure of the DNA-binding domain of interferon regulatory factor-2 (IRF-2) has been determined by NMR spectroscopy. It is composed of a four-stranded antiparallel beta sheet and three alpha helices, and its global fold is similar to those of the winged helix-turn-helix (wHTH) family of proteins. A long loop (Pro37-Asp51) is found immediately before the HTH motif, which is not found in other wHTH proteins. The NMR signals of residues in this long loop, as well as the second helix of the HTH motif, are strongly affected upon the addition of the hexamer repeat DNA, suggesting that these structural elements participate in DNA recognition and binding.

CONCLUSIONS

The structural similarity of the DNA-binding domain of IRF-2 with those of proteins in the wHTH family shows that the IRF proteins belong to the wHTH family, even though there is no apparent sequence homology among proteins of the two families. The sequential structure alignment program (SSAP) shows that IRF-2 has a slightly different structure from typical wHTH proteins, mainly in the orientation of helix 2. The IRF family of proteins should therefore be categorized into a subfamily of the wHTH family. The evidence here implies that the evolutional pathway of the IRF family is distinct from that of the other wHTH proteins, in other words, the immune system diverged from an evolutional stem at an early stage.

Differences in activity between alpha and beta type I interferons explored by mutational analysis

Type I interferon (IFN) subtypes alpha and beta share a common multicomponent, cell surface receptor and elicit a similar range of biological responses, including antiviral, antiproliferative, and immunomodulatory activities. However, alpha and beta IFNs exhibit key differences in several biological properties. For example, IFN-beta, but not IFN-alpha, induces the association of tyrosine-phosphorylated receptor components ifnar1 and ifnar2, and has activity in cells lacking the IFN receptor-associated, Janus kinase tyk2. To define the structural basis for these functional differences we produced human IFN-beta with point mutations and compared them to wild-type IFN-beta in assays that distinguish alpha and beta IFN subtypes. IFN-beta mutants with charged residues (N86K, N86E, or Y92D) introduced at two positions in the C helix lost the ability to induce the association of tyrosine-phosphorylated receptor chains and had reduced activity on tyk2-deficient cells. The combination of negatively charged residues N86E and Y92D (homologous with IFN-alpha8) increased the cross-species activity of the mutant IFN-betas on bovine cells to a level comparable to that of human IFN-alphas. In contrast, point mutations in the AB loop and D helix had no significant effect on these subtype-specific activities. A subset of these latter mutations did, however, reduce activity in a manner analogous to IFN-alpha mutations. The effects of these mutations on IFN-beta activity are discussed in the context of a family of related ligands acting through a common receptor and signaling pathway.

Structural and functional differences between glycosylated and non-glycosylated forms of human interferon-beta (IFN-beta)

PURPOSE

Two recombinant IFN-beta products have been approved for the treatment of multiple sclerosis, a glycosylated form with the predicted natural amino acid sequence (IFN-beta-1a) and a non-glycosylated form that has a Met-1 deletion and a Cys-17 to Ser mutation (IFN-beta-1b). The structural basis for activity differences between IFN-beta-1a and IFN-beta-1b, is determined.

METHODS

In vitro antiviral, antiproliferative and immunomodulatory assays were used to directly compare the two IFN-beta products. Size exclusion chromatography (SEC), SDS-PAGE, thermal denaturation, and X-ray crystallography were used to examine structural differences.

RESULTS

IFN-beta-1a was 10 times more active than IFN-beta-1b with specific activities in a standard antiviral assay of 20 x 10(7) IU/mg for IFN-beta-1a and 2 x 10(7) IU/mg for IFN-beta-1b. Of the known structural differences between IFN-beta-1a and IFN-beta-1b, only glycosylation affected in vitro activity. Deglycosylation of IFN-beta-1a produced a decrease in total activity that was primarily caused by the formation of an insoluble disulfide-linked IFN precipitate. Deglycosylation also resulted in an increased sensitivity to thermal denaturation. SEC data for IFN-beta-1b revealed large, soluble aggregates that had reduced antiviral activity (approximated at 0.7 x 10(7) IU/mg). Crystallographic data for IFN-beta-1a revealed that the glycan formed H-bonds with the peptide backbone and shielded an uncharged surface from solvent exposure.

CONCLUSIONS

Together these results suggest that the greater biological activity of IFN-beta-1a is due to a stabilizing effect of the carbohydrate on structure.

Global regulatory considerations for unified assay specifications

When developing a biotechnology product for global registration, there are several aspects to evaluate in an effort to unify specifications. These include differences between the United States, Europe and Japan, and Rest-of-World (ROW) countries with regard to the respective regulatory guidelines and pharmacopoeias in force, the state-of-the-art of product testing analytical methods, and the interval between submitting a registration dossier to different countries. In terms of regulatory guidelines, one country may have a monograph or required specifications for particular tests, for example the potency that a product has to meet before clinical trials can be initiated. For pharmacopoeias, different assay methods are required for sterility, general safety, and pyrogen testing, so that one may have to test a specific lot of a product at two or three different times to evaluate the same parameter, because of specific testing differences required for each country's pharmacopoeia. In addition, the state of analytical methods is always evolving and better analytical techniques become available. Sometimes, from starting with one set of tests, and based on the time in development, new tests may be added to the existing list of release specifications, because new analytical techniques have become available. Examining the global registration approval process for Betaseron, (interferon beta-1b) illustrates when specifications were able to be unified and when they were not.