Isolation of influenza viral proteins by size-exclusion and ion-exchange high-performance liquid chromatography: the influence of conditions on separation

Universal type/subtype-specific antibodies for quantitative analyses of neuraminidase in trivalent influenza vaccines

Both influenza viral hemagglutinin and neuraminidase can induce protective immune responses in humans. Although the viral hemagglutinin antigens have been quantified in influenza vaccines, the amounts of neuraminidase remain undetermined. Using comprehensive bioinformatics analyses of all neuraminidase sequences, we identified highly conserved and subtype-specific peptide epitopes within each of N1, N2 and type B neuraminidase groups. Mono-specific antibodies generated against these peptides bound to their respective subtype/type only while demonstrating remarkable specificity against the viral neuraminidase sequences without any cross-reactivity with allantoic and cellular proteins. Moreover, the subtype/type-specific antibodies were found not to interfere with one another when a mixture of vaccine samples was analysed. Importantly, immunoassay based on these antibodies can quantitatively determine neuraminidase in commercial trivalent vaccine samples. Analyses of vaccines from eight manufacturers using the same vaccine seeds revealed significant differences in neuraminidase levels. Specifically, while the ratio between neuraminidase and hemagglutinin in some products are found to be close 1/5, other products have a ratio of approximately 1/100, a level which is far below the theoretical ratio between neuraminidase and hemagglutinin in a virus. The antibody-based assays reported here could be of great value for better quality control of both monovalent and trivalent vaccines.

Field-Effect Biosensors for On-Site Detection: Recent Advances and Promising Targets

There is an explosive interest in the immediate and cost-effective analysis of field-collected biological samples, as many advanced biodetection tools are highly sensitive, yet immobile. On-site biosensors are portable and convenient sensors that provide detection results at the point of care. They are designed to secure precision in highly ionic and heterogeneous solutions with minimal hardware. Among various methods that are capable of such analysis, field-effect biosensors are promising candidates due to their unique sensitivity, manufacturing scalability, and integrability with computational circuitry. Recent developments in nanotechnological surface modification show promising results in sensing from blood, serum, and urine. This report gives a particular emphasis on the on-site efficacy of recently published field-effect biosensors, specifically, detection limits in physiological solutions, response times, and scalability. The survey of the properties and existing detection methods of four promising biotargets, exosomes, bacteria, viruses, and metabolites, aims at providing a roadmap for future field-effect and other on-site biosensors.

Challenges and opportunities of using liquid chromatography and mass spectrometry methods to develop complex vaccine antigens as pharmaceutical dosage forms

Liquid chromatographic methods, combined with mass spectrometry, offer exciting and important opportunities to better characterize complex vaccine antigens including recombinant proteins, virus-like particles, inactivated viruses, polysaccharides, and protein-polysaccharide conjugates. The current abilities and limitations of these physicochemical methods to complement traditional in vitro and in vivo vaccine potency assays are explored in this review through the use of illustrative case studies. Various applications of these state-of-the art techniques are illustrated that include the analysis of influenza vaccines (inactivated whole virus and recombinant hemagglutinin), virus-like particle vaccines (human papillomavirus and hepatitis B), and polysaccharide linked to protein carrier vaccines (pneumococcal). Examples of utilizing these analytical methods to characterize vaccine antigens in the presence of adjuvants, which are often included to boost immune responses as part of the final vaccine dosage form, are also presented. Some of the challenges of using chromatographic and LC-MS as physicochemical assays to routinely test complex vaccine antigens are also discussed.

Downstream processing and chromatography based analytical methods for production of vaccines, gene therapy vectors, and bacteriophages

Downstream processing of nanoplexes (viruses, virus-like particles, bacteriophages) is characterized by complexity of the starting material, number of purification methods to choose from, regulations that are setting the frame for the final product and analytical methods for upstream and downstream monitoring. This review gives an overview on the nanoplex downstream challenges and chromatography based analytical methods for efficient monitoring of the nanoplex production.

Qualitative and quantitative analyses of virtually all subtypes of influenza A and B viral neuraminidases using antibodies targeting the universally conserved sequences

Neuraminidase-induced immune responses are correlated with protection of humans and animals from influenza. However, the amounts of neuraminidase in influenza vaccines are yet to be standardized. Thus, a simple method capable of quantifying neuraminidase would be desirable. Here we identified two universally conserved sequences in all influenza A and B neuraminidases, one representing a novel finding of nearly 100% conservation near the enzymatically active site. Antibodies generated against the two highly conserved sequences bound to all nine subtypes of influenza A neuraminidase and demonstrated remarkable specificity against the viral neuraminidase sequences without any cross-reactivity with allantoic and cellular proteins. Importantly, employing these antibodies for the analyses of vaccines from eight manufacturers using the same vaccine seeds revealed marked variations of neuraminidase levels in addition to considerable differences between lots from the same producer. The reasons for the absence or low level of neuraminidase in vaccine preparations are complex and could be multi-factorial. The antibody-based assays reported here could be of practical value for better vaccine quality control.

Selective and Quantitative Detection of Influenza Virus Proteins in Commercial Vaccines Using Two-Dimensional High-Performance Liquid Chromatography and Fluorescence Detection

In this work, we report on the applicability of two-dimensional high-performance liquid chromatography (2D-HPLC) for the comprehensive characterization of inactivated influenza vaccine proteins. This novel procedure features minimal sample treatment and combines the on-line coupling of size exclusion HPLC to reversed-phase HPLC. A comparative analysis of commercial vaccines from three different manufacturers showed the method to be highly selective by providing characteristic reproducible chromatographic profiles for each vaccine. In addition, the method provided enhanced sensitivity for most constituents as a result of the use of native fluorescence detection in the reversed-phase HPLC step. The limits of detection (at a signal-to-noise ratio of >3) for hemagglutinin (HA) antigens were 105 and 172 ng/mL for influenza A/New Caledonia/20/99 and B/Jiangsu/10/2003 strains, respectively. The potential of this 2D-HPLC procedure in terms of quantitative antigen analysis was assessed by determination of the HA content of commercial vaccines. Results provided very good correlation with nominal HA values. The reproducibility (RSD) of the whole procedure was also evaluated and was found to be better than 2 and 3% for calculated antigen concentrations expressed as micrograms of HA per milliliter in commercial vaccines for samples of the same lot (n = 5) or different lots (n = 3), respectively. In addition, it allowed the selective detection of several influenza constituents including nucleoproteins from type A and B viruses and the highly hydrophobic matrix protein 1 from both virus strains.

Rapid and selective characterization of influenza virus constituents in monovalent and multivalent preparations using non-porous reversed-phase high performance liquid chromatography columns

The characterization of influenza vaccine composition has been approached through a novel methodology suitable for routine analysis. It is based on a two-stage process involving an initial sample processing step followed by analysis by reversed-phase HPLC with UV detection. The sample processing involves an initial concentration step carried out in the presence of a combination of detergents and organic solvents to enhance solubilization and ultimately to provide adequate detection. Conditions that provided fast, reproducible and selective separations of vaccine constituents were investigated by reversed-phase HPLC. The use of non-porous silica stationary phases was found to minimize carry-over and non-specific adsorption observed with conventional columns. An evaluation of separation parameters, including mobile phase composition and column temperature, allowed optimization of the selectivity of the method. The optimized method was suitable for the characterization of processed monovalent preparations (containing influenza virus constituents from a single strain). In addition, it allowed the simultaneous detection of the three influenza subtypes in trivalent vaccines in a single analysis. Several influenza constituents were detected including nucleoprotein, the highly hydrophobic matrix protein and the primary surface antigen, haemagglutinin (HA).

Analysis and separation of synaptosomal membrane proteins

Synaptosomal membrane proteins solubilized with 8% CHAPS-8 M urea were analyzed with two-dimensional electrophoresis (2DE). The membrane proteins were resolved up to 250 spots on a 2DE map, ranging in isoelectric points (pI) from 3.5 to 10.0 and molecular weights (MW) from 10 kDa to 200 kDa. Comparison of the mapped proteins of synaptosomal membranes with those of myelin and mitochondrial membranes revealed that synaptosomal membrane proteins were characteristic in the area of pI from 4.0 to 7.5 and MW from 20 kDa to 130 kDa, and that at least 30 spots were synaptosomal membrane-specific proteins. Most of these 30 proteins have not been previously described, named, and characterized. Serial numbers (from SY1 to SY30) were assigned to the proteins on the map in order to investigate them systematically. A preliminary attempt to separate synaptosomal membrane proteins was carried out using a reversed-phase HPLC system. Several proteins could either be isolated or enriched. SY10 (pI 4.6; MW 56 kDa) was one of these proteins, and was of particular interest for its unusual behavior on the reversed-phase column, and for its binding to an immobilized protein A-gel.

Preparative purification of functional bacteriorhodopsin by high-performance size-exclusion chromatography

High-performance size-exclusion chromatography (HPSEC) was used to produce stable bacteriorhodopsin essentially free of native lipids. The purified bacteriorhodopsin was shown to be highly functional when reconstituted into phospholipid vesicles. Purple membrane was washed in the detergent 3-[( 3-cholamidopropyl)dimethylammonio]-2,2-hydroxy-1-propanesulfonate (CHAPSO) to remove a large fraction (65%) of the membrane lipids, solubilized in Triton X-100 and purified on a Bio-Sil TSK G3000SW column using a CHAPSO mobile phase. Pooled column fractions of bacteriorhodopsin from 25-mg sample loads show a 280/548 nm absorbance ratio of 1.5-1.6 and contain less than 4% endogenous lipids. This HPSEC method requires much less expensive synthetic detergent and is much faster than open column methods [cf. L.J.W. Miercke, P.E. Ross, R.M. Stroud and E.A. Dratz, J. Biol. Chem., 264 (1989) 7531-7535].

Isolation of glycoprotein D from herpes simplex virus type 1 by gel filtration high performance liquid chromatography

Rabbit kidney (RK-13) and human jejunum and ileum (I-407) cells infected with herpes simplex virus type 1, strain F, were radiolabelled with [14C]glucosamine or [35S]methionine for 24 h. The cells were extracted with 1% Triton X-100 and the extracts were separated by gel filtration high performance liquid chromatography. Monoclonal antibody immunoprecipitation of the fractions collected from the column revealed a monomeric glycoprotein D (gD) of 52 - 56,000 molecular weight from RK-13 cells and two monomeric forms of gD, 54,000 and 58,000 molecular weight, from I-407 cells. Densitometry scanning of the autoradiograms from SDS-PAGE showed gD from the RK-13 host cells to be 98.7% pure with the [35S]methionine label and 97.0% pure with the [14C]glucosamine. On the other hand, gD from the I-407 host cells was only 78.6% with the [35S]methionine label and 96% pure with the [14C]glucosamine. This method could provide a means for the isolation of native gD for structural and immunological studies.

Protein purification

This monograph summarizes recent developments in the purification and analysis of natural and recombinant proteins. The basic strategies employed in protein purification are reviewed with regards to the characteristics of the protein of interest that may aid its isolation, choice of the starting material, and use of denaturants. Preparation of cell-free extracts followed by bulk precipitation and/or phase partition constitute the initial steps of many purification schemes. Chromatographic methods (size exclusion, ion exchange, hydroxylapatite, reversed phase, hydrophobic interaction and affinity based) utilizing either traditional, low pressure or high-performance liquid chromatography instrumentation are discussed. Electrophoretic techniques used to analyze the homogeneity of the protein product include SDS-PAGE, isotachophoresis, IEF and two dimensional gel electrophoresis.

Effect of detergents on the structure of integral membrane proteins of Sendai virus studied with size-exclusion high-performance liquid chromatography and monoclonal antibodies

The integral membrane proteins of Sendai virus, the fusion protein F (Mr = 65,000) and the haemagglutinin-neuraminidase protein HN (Mr = 68,000), were used as a model protein mixture. They were subjected to size-exclusion high-performance liquid chromatography on Superose 6HR columns with eluents containing various additives in order to solubilize the proteins. The effect of the additives on the structure of the membrane proteins was investigated with conformation-dependent monoclonal antibodies, either directed against F or HN protein, and by determination of the haemagglutinating capacity of the HN protein. The results show that the structure of the HN protein is more easily disturbed by eluents than that of the F protein. When the elution conditions are mild, e.g., 0.1% octylglucoside, the structure of both proteins is conserved but no separation is obtained. Elution with a buffer containing 0.05% sarkosyl (dodecyl methylglycine sodium salt) did not affect the structure and resulted in pure F protein. Pretreatment of the Amberlite XAD-2-treated Sendai virus envelope extract with 4% sodium dodecyl sulphate (SDS) and elution with 0.1% SDS in 50 mM sodium phosphate (pH 6.5) altered the structure of the HN protein but resulted in purification of the tetramer and the dimer of the HN protein, and the monomer of the F protein.

Column liquid chromatography of integral membrane proteins

Biological membranes have as a major function the compartmentation of biological processes in cells and organelles. They consist of a bilayer of phospholipid molecules in which proteins are embedded. These integral membrane proteins, which cross the bilayer once or several times, generally have a higher than average hydrophobicity and tend to aggregate. Detergents are needed to remove integral membrane proteins from the lipid bilayer and they have to be present during further chromatographic purification. Predominantly, four modes of HPLC have been used alone or in combination for the purification of integral membrane proteins. These are based on differences of proteins in size (size-exclusion chromatography, SEC), electrostatic interaction (ion-exchange chromatography, IEC), bioaffinity (bioaffinity chromatography, BAC) and hydrophobic interaction (reversed-phase chromatography, RPC, and hydrophobic-interaction chromatography, HIC). SEC, IEC, BAC and HIC are used under relatively mild conditions, and buffer systems generally contain a non-ionic detergent. RPC generally has a denaturing effect on the protein and should preferably be used for the purification of integral membrane proteins smaller than 50 kD.

High-performance liquid chromatography of membrane proteins

Various modes of high-performance liquid chromatography, gel filtration, ion-exchange chromatography, hydrophobic interaction chromatography, reversed-phase chromatography and metal chelate affinity chromatography, were investigated for the separation of membrane proteins. All were found applicable to membrane proteins, although the usefulness of each mode differed. For satisfactory results it was important to select appropriate elution conditions. The type and concentration of detergent was of special importance. The effects of other conditions, flow-rate, gradient steepness, type of buffer and salt, eluent pH, etc., were similar to those observed for soluble proteins.