Development of recombinant protein-based influenza vaccine. Expression and affinity purification of H1N1 influenza virus neuraminidase

Production of Influenza Virus Glycoproteins Using Insect Cells

The baculovirus/insect cell expression system is a very useful tool for reagent and antigen generation in vaccinology, virology, and immunology. It allows for the production of recombinant glycoproteins, which are used as antigens in vaccination studies and as reagents in immunological assays. Here, we describe the process of recombinant glycoprotein production using the baculovirus/insect cell expression system.

Optimization of an Inclusion Body-Based Production of the Influenza Virus Neuraminidase in Escherichia coli

Neuraminidase (NA), as an important protein of influenza virus, represents a promising target for the development of new antiviral agents for the treatment and prevention of influenza A and B. Bacterial host strain Escherichia coli BL21 (DE3)pLysS containing the NA gene of the H1N1 influenza virus produced this overexpressed enzyme in the insoluble fraction of cells in the form of inclusion bodies. The aim of this work was to investigate the effect of independent variables (propagation time, isopropyl β-d-1-thiogalactopyranoside (IPTG) concentration and expression time) on NA accumulation in inclusion bodies and to optimize these conditions by response surface methodology (RSM). The maximum yield of NA (112.97 ± 2.82 U/g) was achieved under optimal conditions, namely, a propagation time of 7.72 h, IPTG concentration of 1.82 mM and gene expression time of 7.35 h. This study demonstrated that bacterially expressed NA was enzymatically active.

A Novel Recombinant Influenza Virus Neuraminidase Vaccine Candidate Stabilized by a Measles Virus Phosphoprotein Tetramerization Domain Provides Robust Protection from Virus Challenge in the Mouse Model

Current seasonal influenza virus vaccines do not induce robust immune responses to neuraminidase. Several factors, including immunodominance of hemagglutinin over neuraminidase, instability of neuraminidase in vaccine formulations, and variable, nonstandardized amounts of neuraminidase in the vaccines, may contribute to this effect. However, vaccines that induce strong antineuraminidase immune responses would be beneficial, as they are highly protective. Furthermore, antigenic drift is slower for neuraminidase than for hemagglutinin, potentially providing broader coverage. Here, we designed stabilized recombinant versions of neuraminidase by replacing the N-terminal cytoplasmic domain, transmembrane, and extracellular stalk with tetramerization domains from the measles or Sendai virus phosphoprotein or from an Arabidopsis thaliana transcription factor. The measles virus tetramerization domain-based construct, termed N1-MPP, was chosen for further evaluation, as it retained antigenicity, neuraminidase activity, and structural integrity and provided robust protection in vivo against lethal virus challenge in the mouse model. We tested N1-MPP as a standalone vaccine, admixed with seasonal influenza virus vaccines, or given with seasonal influenza virus vaccines but in the other leg of the mouse. Admixture with different formulations of seasonal vaccines led to a weak neuraminidase response, suggesting a dominant effect of hemagglutinin over neuraminidase when administered in the same formulation. However, administration of neuraminidase alone or with seasonal vaccine administered in the alternate leg of the mouse induced robust antibody responses. Thus, this recombinant neuraminidase construct is a promising vaccine antigen that may enhance and broaden protection against seasonal influenza viruses. IMPORTANCE Influenza virus infections remain a high risk to human health, causing up to 650,000 deaths worldwide every year, with an enormous burden on the health care system. Since currently available seasonal vaccines are only partially effective and often mismatched to the circulating strains, a broader protective influenza virus vaccine is needed. Here, we generated a recombinant influenza virus vaccine candidate based on the more conserved neuraminidase surface glycoprotein in order to induce a robust and broader protective immune response against a variety of circulating influenza virus strains.

Reduce, Reuse and Recycle in Protein Chromatography: Development of an Affinity Adsorbent from Waste Paper and Its Application for the Purification of Proteases from Fish By-Products

In the present study, we report the development of a cellulose-based affinity adsorbent and its application for the purification of proteases from fish by-products. The affinity adsorbent was synthesized using cellulose microfibers as the matrix, isolated from recycled newspapers using the acid precipitation method. As an affinity ligand, the triazine dye Cibacron Blue 3GA (CB3GA) was used and immobilized directly onto the cellulose microfibers. Absorption equilibrium studies and frontal affinity chromatography were employed to evaluate the chromatographic performance of the adsorbent using as model proteins bovine serum albumin (BSA) and lysozyme (LYS). Absorption equilibrium studies suggest that the adsorption of both proteins obeys the Langmuir isotherm model. The kinetics of adsorption obey the pseudo-second-order model. The affinity adsorbent was applied for the development of a purification procedure for proteases from Sparus aurata by-products (stomach and pancreas). A single-step purification protocol for trypsin and chymotrypsin was developed and optimized. The protocol afforded enzymes with high yields suitable for technical and industrial purposes.

NAction! How Can Neuraminidase-Based Immunity Contribute to Better Influenza Virus Vaccines?

Neuraminidase is one of the two surface glycoproteins of influenza A and B viruses. It has enzymatic activity that cleaves terminal sialic acid from glycans, and that activity is essential at several points in the virus life cycle. While neuraminidase is a major target for influenza antivirals, it is largely ignored in vaccine development. Current inactivated influenza virus vaccines might contain neuraminidase, but the antigen quantity and quality are varied and not standardized. While there are data that show a protective role of anti-neuraminidase immunity, many questions remain unanswered. These questions, among others, concern the targeted epitopes or antigenic sites, the potential for antigenic drift, and, connected to that, the breadth of protection, differences in induction of immune responses by vaccination versus infection, mechanisms of protection, the role of mucosal antineuraminidase antibodies, stability, and the immunogenicity of neuraminidase in vaccine formulations. Reagents for analysis of neuraminidase-based immunity are scarce, and assays are not widely used for clinical studies evaluating vaccines. However, efforts to better understand neuraminidase-based immunity have been made recently. A neuraminidase focus group, NAction!, was formed at a Centers of Excellence for Influenza Research and Surveillance meeting at the National Institutes of Health in Bethesda, MD, to promote research that helps to understand neuraminidase-based immunity and how it can contribute to the design of better and broadly protective influenza virus vaccines. Here, we review open questions and knowledge gaps that have been identified by this group and discuss how the gaps can be addressed, with the ultimate goal of designing better influenza virus vaccines.

Expression and Characterization of Recombinant, Tetrameric and Enzymatically Active Influenza Neuraminidase for the Setup of an Enzyme-Linked Lectin-Based Assay

Developing a universal influenza vaccine that induces broad spectrum and longer-term immunity has become an important potentially achievable target in influenza vaccine research and development. Hemagglutinin (HA) and neuraminidase (NA) are the two major influenza virus antigens. Although antibody responses against influenza virus are mainly directed toward HA, NA is reported to be more genetically stable; hence NA-based vaccines have the potential to be effective for longer time periods. NA-specific immunity has been shown to limit the spread of influenza virus, thus reducing disease symptoms and providing cross-protection against heterosubtypic viruses in mouse challenge experiments.

The production of large quantities of highly pure and stable NA could be beneficial for the development of new antivirals, subunit-based vaccines, and novel diagnostic tools. In this study, recombinant NA (rNA) was produced in mammalian cells at high levels from both swine A/California/07/2009 (H1N1) and avian A/turkey/Turkey/01/2005 (H5N1) influenza viruses. Biochemical, structural, and immunological characterizations revealed that the soluble rNAs produced are tetrameric, enzymatically active and immunogenic, and finally they represent good alternatives to conventionally used sources of NA in the Enzyme-Linked Lectin Assay (ELLA).

Development of a surface plasmon resonance assay to measure the binding affinity of wild-type influenza neuraminidase and its H274Y mutant to the antiviral drug zanamivir

Influenza is one of the most common infections of the upper respiratory tract. Antiviral drugs that are currently used to treat influenza, such as oseltamivir and zanamivir, are neuraminidase (NA) inhibitors. However, the virus may develop resistance through single-point mutations of NA. Antiviral resistance is currently monitored by a labelled enzymatic assay, which can be inconsistent because of the short half-life of the labelled product and variations in the assay conditions. In this paper, we describe a label-free surface plasmon resonance (SPR) assay for measuring the binding affinity of NA-drug interactions. Wild-type (WT) NA and a histidine 274 tyrosine (H274Y) mutant were expressed in High Five™ (Trichoplusia ni) insect cells. A spacer molecule (1,6-hexanediamine) was site-specifically conjugated to the 7-hydroxyl group of zanamivir, which is not involved in binding to NA, and the construct was immobilized onto a SPR sensor Chip to obtain a final immobilization response of 431 response units. Binding responses obtained for WT and H274Y mutant NAs were fitted to a simple Langmuir 1:1 model with drift to obtain the association (ka ) and dissociation (kd ) rate constants. The ratio between the binding affinities for the two isoforms was comparable to literature values obtained using labelled enzyme assays. Significant potential exists for an extension of this approach to test for drug resistance of further NA mutants against zanamivir and other antiviral drugs, perhaps paving the way for a reliable SPR biosensor assay that may replace labelled enzymatic assays.

Expression of functional recombinant hemagglutinin and neuraminidase proteins from the novel H7N9 influenza virus using the baculovirus expression system

The baculovirus expression system is a powerful tool for expression of recombinant proteins. Here we use it to produce correctly folded and glycosylated versions of the influenza A virus surface glycoproteins - the hemagglutinin (HA) and the neuraminidase (NA). As an example, we chose the HA and NA proteins expressed by the novel H7N9 virus that recently emerged in China. However the protocol can be easily adapted for HA and NA proteins expressed by any other influenza A and B virus strains. Recombinant HA (rHA) and NA (rNA) proteins are important reagents for immunological assays such as ELISPOT and ELISA, and are also in wide use for vaccine standardization, antibody discovery, isolation and characterization. Furthermore, recombinant NA molecules can be used to screen for small molecule inhibitors and are useful for characterization of the enzymatic function of the NA, as well as its sensitivity to antivirals. Recombinant HA proteins are also being tested as experimental vaccines in animal models, and a vaccine based on recombinant HA was recently licensed by the FDA for use in humans. The method we describe here to produce these molecules is straight forward and can facilitate research in influenza laboratories, since it allows for production of large amounts of proteins fast and at a low cost. Although here we focus on influenza virus surface glycoproteins, this method can also be used to produce other viral and cellular surface proteins.

Enhanced expression of secretable influenza virus neuraminidase in suspension mammalian cells by influenza virus nonstructural protein 1

Influenza neuraminidase (NA) is a major target for anti-influenza drugs. With an increasing number of viruses resistant to the anti-NA drug oseltamivir, functionally active recombinant NA is needed for screening novel anti-NA compounds. In this study, the secretable NA (sNA) head domain of influenza A/Vietnam/DT-036/05 (H5N1) virus was expressed successfully in human embryonic kidney (HEK-293T) cells and shown to be enzymatically active. The inclusion of a plasmid encoding nonstructural protein 1 (NS1) of influenza A/Puerto Rico/8/34 virus with the sNA plasmid in the cotransfection demonstrated an increase in H5N1 sNA expression by 7.4 fold. Subsequently, the sNA/NS1 cotransfection protocol in serum-free 293-F suspension cell culture was optimized to develop a rapid transient gene expression (TGE) system for expression of large amounts of H5N1 sNA. Under optimized conditions, NS1 enhanced H5N1 sNA expression by 4.2 fold. The resulting H5N1 sNA displayed comparable molecular weight, glycosylation, K(m) for MUNANA, and K(i) for oseltamivir carboxylate to those of H5N1 NA on the virus surface. Taken together, the NS1-enhancing sNA expression strategy presented in this study could be used for rapid high-level expression of enzymatically active H5N1 sNA in suspension mammalian cells. This strategy may be applied for expression of sNA of other strains of influenza virus as well as the other recombinant proteins.

A screening assay for neuraminidase inhibitors using neuraminidases N1 and N3 from a baculovirus expression system

CONTEXT

Development of inexpensive and safe enzymatic assays to screen for putative neuraminidase inhibitors.

OBJECTIVE

Validate the use of recombinant neuraminidase expressed in baculovirus located on the viral surface capsule to develop a neuraminidase inhibitor screening assay.

MATERIALS AND METHODS

Recombinant baculovirus particles displaying neuraminidase N1 and N3 were used as enzyme sources. The assay set-up required the use of 2'-(4-methylumbelliferyl)-α-D-acetyl neuraminic acid as substrate and oseltamivir carboxylate as benchmark inhibitor.

RESULTS

The assay was set up in a standard 96-well plate. The within- and between-assay coefficients of variation were, on average, less than 10%. The 50% inhibitory concentration values of the inhibitor were in good agreement with those determined by independent kinetic experiments.

DISCUSSION AND CONCLUSIONS

The assay showed satisfactory within- and between-assay repeatability. The obtained results suggest that recombinant baculovirus expressing neuraminidase located on the virus membrane capsule can be used to set up affordable and reliable neuraminidase inhibitors screening assays.

A generic system for the expression and purification of soluble and stable influenza neuraminidase

The influenza surface glycoprotein neuraminidase (NA) is essential for the efficient spread of the virus. Antiviral drugs such as Tamiflu (oseltamivir) and Relenza (zanamivir) that inhibit NA enzyme activity have been shown to be effective in the treatment of influenza infections. The recent ‘swine flu’ pandemic and world-wide emergence of Tamiflu-resistant seasonal human influenza A(H1N1) H₂₇₄Y have highlighted the need for the ongoing development of new anti-virals, efficient production of vaccine proteins and novel diagnostic tools. Each of these goals could benefit from the production of large quantities of highly pure and stable NA. This publication describes a generic expression system for NAs in a baculovirus Expression Vector System (BEVS) that is capable of expressing milligram amounts of recombinant NA. To construct NAs with increased stability, the natural influenza NA stalk was replaced by two different artificial tetramerization domains that drive the formation of catalytically active NA homotetramers: GCN4-pLI from yeast or the Tetrabrachion tetramerization domain from Staphylothermus marinus. Both recombinant NAs are secreted as FLAG-tagged proteins to allow for rapid and simple purification. The Tetrabrachion-based NA showed good solubility, increased stability and biochemical properties closer to the original viral NA than the GCN4-pLI based construct. The expressed quantities and high quality of the purified recombinant NA suggest that this expression system is capable of producing recombinant NA for a broad range of applications including high-throughput drug screening, protein crystallisation, or vaccine development.

Design and preclinical development of a recombinant protein and DNA plasmid mixed format vaccine to deliver HIV-derived T-lymphocyte epitopes

Coordinated interactions between helper and cytotoxic T-lymphocytes (HTL and CTL) are needed for optimal effector cell functions and the establishment of immunological memory. We, therefore, designed a mixed format vaccine based on the use of highly conserved HIV-derived T-lymphocyte epitopes wherein the HTL epitopes were delivered as a recombinant protein and the CTL epitopes which were encoded in a DNA vaccine plasmid. Immunogenicity testing in HLA transgenic mice and GLP preclinical safety testing in rabbits and guinea pigs were used to document the utility of this approach and to support Phase 1 trial clinical testing. Both vaccine components were immunogenic and safely co-administered.

Combinatorial de novo design and application of a biomimetic affinity ligand for the purification of human anti-HIV mAb 4E10 from transgenic tobacco

Monoclonal anti-HIV antibody 4E10 (mAb 4E10) is one of the most broadly neutralizing antibodies against HIV, directed against a specific epitope on envelope protein gp41. In the present study, a combinatorial de novo design approach was used for the development of a biomimetic ligand for the affinity purification of mAb 4E10 from tobacco transgenic extract in a single chromatographic step. The biomimetic ligand (4E10lig) was based on a L-Phe/beta-Ala bi-substituted 1,3,5-triazine (Trz) scaffold (beta-Ala-Trz-L-Phe, 4E10lig) which potentially mimics the more pronounced electrostatic and hydrophobic interactions of mAb 4E10-binding sequence determined by screening of a random peptide library. This library was comprised of Escherichia coli cells harboring a plasmid (pFlitrx) engineered to express a fusion protein containing random dodecapeptides that were inserted into the active loop of thioredoxin, which itself was inserted into the dispensable region of the flagellin gene. Adsorption equilibrium studies with this biomimetic ligand and mAb 4E10 determined a dissociation constant (K(D)) of 0.41 +/- 0.05 microM. Molecular modeling studies of the biomimetic ligand revealed that it can potentially occupy the same binding site as the natural binding core peptide epitope. The biomimetic affinity adsorbent was exploited in the development of a facile mAb 4E10 purification protocol, affording mAb 4E10 of high purity (approximately 95%) with good overall yield (60-80%). Analysis of the antibody preparation by SDS-PAGE, enzyme-linked immunosorbent assays (ELISA), and western blot showed that the mAb 4E10 was fully active and free of degraded variants, polyphenols, and alkaloids.

Evaluation of recombinant Onchocerca volvulus activation associated protein-1 (ASP-1) as a potent Th1-biased adjuvant with a panel of protein or peptide-based antigens and commercial inactivated vaccines

Alum, the only adjuvant approved for clinical applications, can induce strong humoral (Th2) but weak cellular (Th1) immune responses. It is necessary to develop safe and effective adjuvants capable of inducing both humoral and cellular immune responses. We previously showed that activation-associated protein-1 (ASP-1) derived from Onchocerca volvulus has potent adjuvant activity. In this study, we have further evaluated the adjuvanticity of recombinant ASP-1 using a panel of recombinant proteins or synthetic peptide-based antigens, including ovalbumin (OVA), synthetic HIV peptide (HIV-p), recombinant HIV gp41 (rgp41) and HBV HBsAg, as well as three commercially available inactivated vaccines against haemorrhagic fever with renal syndrome (HFRS), Influenza and Rabies. Our results indicate that ASP-1 induced significantly higher IgG1 (Th2-associated) and IgG2a (Th1-associated) responses than alum adjuvant against OVA antigen, HIV-p, and rgp41. Consistently, it induced similar level of IgG1 responses as alum but higher level of IgG2a and IFN-gamma-producing T cell responses than alum adjuvant against HBsAg. Further, ASP-1 improved both IgG1 and IgG2a responses to three commercial inactivated vaccines when used separately or in combination. In conclusion, the recombinant ASP-1, unlike alum adjuvant, is able to induce both Th1 and Th2-associated humoral responses and Th1 cellular responses, suggesting that it can be further developed as a promising adjuvant for subunit-based and inactivated vaccines.

Influenza vaccines and vaccination strategies in birds

Although it is well accepted that the present Asian H5N1 panzootic is predominantly an animal health problem, the human health implications and the risk of human pandemic have highlighted the need for more information and collaboration in the field of veterinary and human health. H5 and H7 avian influenza (AI) viruses have the unique property of becoming highly pathogenic (HPAI) during circulation in poultry. Therefore, the final objective of poultry vaccination against AI must be eradication of the virus and the disease. Actually, important differences exist in the control of avian and human influenza viruses. Firstly, unlike human vaccines that must be adapted to the circulating strain to provide adequate protection, avian influenza vaccination provides broader protection against HPAI viruses. Secondly, although clinical protection is the primary goal of human vaccines, poultry vaccination must also stop transmission to achieve efficient control of the disease. This paper addresses these differences by reviewing the current and future influenza vaccines and vaccination strategies in birds.

Affinity chromatography for the purification of therapeutic proteins from transgenic maize using immobilized histamine

Plant molecular pharming is a technology that uses plants as bioreactors to produce recombinant molecules of medical and veterinary importance. In the present study, we evaluated the ability of histamine (HIM), tryptamine (TRM), phenylamine (PHEM) and tyramine (TYRM) coupled to Sepharose CL-4B via a 1,4-butanediol diglycidyl ether spacer to bind and purify human monoclonal anti-HIV antibody 2F5 (mAb 2F5) from spiked maize seed and tobacco leaf extracts. Detailed studies were carried out to determine the factors that affect the chromatographic behaviour of mAb 2F5 and also maize seed and tobacco leaf proteins. All affinity adsorbents showed a reduced capacity to bind and a reduced ability to purify proteins from tobacco extract compared to maize extract. Under optimal conditions, HIM exhibited high selectivity for mAb 2F5 and allowed a high degree of purification (>95% purity) and recovery (>90%) in a single step with salt elution (0.4 M KCl) from spiked maize seed extract. Analysis of the purified antibody fraction by ELISA and Western blot showed that the antibody was fully active and free of degraded variants or modified forms. The efficacy of the system was assessed further using a second therapeutic antibody (human monoclonal anti-HIV antibody mAb 2G12) and a therapeutic enzyme (alpha-chymotrypsin). HIM may find application in the purification of a wide range of biopharmaceuticals from transgenic plants.