Membrane Chromatography-Based Downstream Processing for Cell-Culture Produced Influenza Vaccines

New influenza strains are constantly emerging, causing seasonal epidemics and raising concerns to the risk of a new global pandemic. Since vaccination is an effective method to prevent the spread of the disease and reduce its severity, the development of robust bioprocesses for producing pandemic influenza vaccines is exceptionally important. Herein, a membrane chromatography-based downstream processing platform with a demonstrated industrial application potential was established. Cell culture-derived influenza virus H1N1/A/PR/8/34 was harvested from benchtop bioreactor cultures. For the clarification of the cell culture broth, a depth filtration was selected as an alternative to centrifugation. After inactivation, an anion exchange chromatography membrane was used for viral capture and further processing. Additionally, two pandemic influenza virus strains, the H7N9 subtype of the A/Anhui/1/2013 and H3N2/A/Hong Kong/8/64, were successfully processed through similar downstream process steps establishing optimized process parameters. Overall, 41.3–62.5% viral recovery was achieved, with the removal of 86.3–96.5% host cell DNA and 95.5–99.7% of proteins. The proposed membrane chromatography purification is a scalable and generic method for the processing of different influenza strains and is a promising alternative to the current industrial purification of influenza vaccines based on ultracentrifugation methodologies.

A Four-Step Purification Process for Gag VLPs: From Culture Supernatant to High-Purity Lyophilized Particles

Gag-based virus-like particles (VLPs) have high potential as scaffolds for the development of chimeric vaccines and delivery strategies. The production of purified preparations that can be preserved independently from cold chains is highly desirable to facilitate distribution and access worldwide. In this work, a nimble purification has been developed, facilitating the production of Gag VLPs. Suspension-adapted HEK 293 cells cultured in chemically defined cell culture media were used to produce the VLPs. A four-step downstream process (DSP) consisting of membrane filtration, ion-exchange chromatography, polishing, and lyophilization was developed. The purification of VLPs from other contaminants such as host cell proteins (HCP), double-stranded DNA, or extracellular vesicles (EVs) was confirmed after their DSP. A concentration of 2.2 ± 0.8 × 10⁹ VLPs/mL in the lyophilized samples was obtained after its storage at room temperature for two months. Morphology and structural integrity of purified VLPs was assessed by cryo-TEM and NTA. Likewise, the purification methodologies proposed here could be easily scaled up and applied to purify similar enveloped viruses and vesicles.

Development and Validation of an Anion Exchange High-Performance Liquid Chromatography Method for Analysis of Empty Capsids and Capsids Encapsidating Genetic Material in a Purified Preparation of Recombinant Adeno-Associated Virus Serotype 5

The development of various manufacturing platforms and analytical technologies has substantially contributed to successfully translating the recombinant adeno-associated viral vector from the laboratory to the clinic. The active deployment of these analytical technologies for process and product characterization has helped define critical quality attributes and improve the quality of the clinical grade material. In this article, we report an anion exchange high-performance liquid chromatography (AEX-HPLC) method for relative and as well as absolute quantification of empty capsids (EC) and capsids encapsidating genetic material (CG) in purified preparations of adeno-associated virus (AAV) using serotype 5 as a model. The selection of optimal chromatographic buffer composition and step-gradient elution protocol offered baseline separation of EC and CG in the form of two peaks, as validated with the respective reference standards. The native amino acid fluorescence-based detection offered excellent linearity with a correlation coefficient of 0.9983 over two-log dilutions of the sample. The limit of detection and limit of quantification values associated with the total AAV5 capsid assay are 3.1E + 09 and 9.5E + 09, respectively. AEX-HPLC showed method comparability with the analytical ultracentrifugation (AUC) method for determination of relative proportions of EC and CG, supporting the reported HPLC method as an easy-to-access alternative to AUC with operational simplicity. Moreover, rapid and easy adaptation of this method to AAV8 material also demonstrated the robustness of the proposed approach.

Development of a scalable and robust AEX method for enriched rAAV preparations in genome-containing VCs of serotypes 5, 6, 8, and 9

Removal of empty capsids from adeno-associated virus (AAV) manufacturing lots remains a critical step in the downstream processing of AAV clinical-grade batches. Because of similar physico-chemical characteristics, the AAV capsid populations totally lacking or containing partial viral DNA are difficult to separate from the desired vector capsid populations. Based on minute differences in density, ultracentrifugation remains the most effective separation method and has been extensively used at small scale but has limitations associated with availabilities and operational complexities in large-scale processing. In this paper, we report a scalable, robust, and versatile anion-exchange chromatography (AEX) method for removing empty capsids and subsequent enrichment of vectors of AAV serotypes 5, 6, 8, and 9. On average, AEX resulted in about 9-fold enrichment of AAV5 in a single step containing 80% ± 5% genome-containing vector capsids, as verified and quantified by analytical ultracentrifugation. The optimized process was further validated using AAV6, AAV8, and AAV9, resulting in over 90% vector enrichment. The AEX process showed comparable results not only for vectors with different transgenes of different sizes but also for AEX runs under different geometries of chromatographic media. The herein-reported sulfate-salt-based AEX process can be adapted to different AAV serotypes by appropriately adjusting elution conditions to achieve enriched vector preparations.

Scalable Lentiviral Vector Production Using Stable HEK293SF Producer Cell Lines

Lentiviral vectors (LV) represent a key tool for gene and cell therapy applications. The production of these vectors in sufficient quantities for clinical applications remains a hurdle, prompting the field toward developing suspension processes that are conducive to large-scale production. This study describes a LV production strategy using a stable inducible producer cell line. The HEK293 cell line employed grows in suspension, thus offering direct scalability, and produces a green fluorescent protein (GFP)-expressing lentiviral vector in the 10⁶ transduction units (TU)/mL range without optimization. The stable producer cell line, called clone 92, was derived by stable transfection from a packaging cell line with a plasmid encoding the transgene GFP. The packaging cell line expresses all the other necessary components to produce LV upon induction with cumate and doxycycline. First, the study demonstrated that LV production using clone 92 is scalable from 20 mL shake flasks to 3 L bioreactors. Next, two strategies were developed for high-yield LV production in perfusion mode using acoustic cell filter technology in 1–3 L bioreactors. The first approach uses a basal commercial medium and perfusion mode both pre- and post-induction for increasing cell density and LV recovery. The second approach makes use of a fortified medium formulation to achieve target cell density for induction in batch mode, followed by perfusion mode after induction. Using these perfusion-based strategies, the titer was improved to 3.2 × 10⁷ TU/mL. As a result, cumulative functional LV titers were increased by up to 15-fold compared to batch mode, reaching a cumulative total yield of 8 × 10¹⁰ TU/L of bioreactor culture. This approach is easily amenable to large-scale production and commercial manufacturing.

Survey of delivery of prophylactic immunoglobulins following exposure to a measles case

In France, almost 23,000 cases of measles and 10 deaths have been reported between January 2008 and August 2012. French health authorities recommend delivery of human polyvalent immunoglobulins in the event of exposure to a measles case for some categories of unvaccinated persons (children under the age of 12 months, immunocompromised persons and pregnant women), within six days after exposure and following laboratory confirmation of the contact case. We carried out a postal survey among 368 French hospital pharmacies to evaluate the number of persons affected by this measure between 1 January 2010 and 31 August 2011, to describe the characteristics of these patients and to evaluate the application of the recommendations in terms of delay between exposure and immunoglobulin delivery, and confirmation of the contact case. The response rate to the survey was 73%. In total, 400 immunoglobulin deliveries were listed, most of them for children under the age of one year, and 84% of the 250 administrations with available information occurred within six days after exposure, as recommended. However, only 48% of the 209 treated contacts with available information were laboratory-confirmed when the immunoglobulins were delivered. This survey is the first evaluation of this recommendation since its introduction in 2005 and suggests that the recommendations may need to be updated.

An efficient process for the purification of helper-dependent adenoviral vector and removal of helper virus by iodixanol ultracentrifugation

The preparation of large amount of purified helper-dependent adenoviral vector material is hampered by the lack of development of downstream processes with proven records on separation and recovery efficiencies. In order to facilitate the use of clinical-grade helper-dependent virus material for large-scale in vivo studies, a three-step purification scheme consisting of (1) an anion-exchange chromatography for initial capturing of virus, (2) a shallow iodixanol density gradient ultracentrifugation for the removal of helper virus from helper-dependent virus, and (3) a size-exclusion chromatography for the removal of iodixanol and residual protein contaminants as a polishing step was developed. The use of a fast iodixanol density ultracentrifugation step was highly effective in separating infectious helper-dependent virus from contaminating helper virus. The overall downstream processing scheme gave 80% infectious particle yield. The contamination ratio of helper virus in the helper-dependent virus preparation are reduced from 2.57 to 0.03% corresponding to a reduction of helper virus by factors of 85 by two iodixanol purification steps. It was also demonstrated that size-exclusion chromatography is an excellent step for the removal of iodixanol and polishing of the final helper-dependent virus preparation.

Rapid and reliable quantification of reovirus type 3 by high performance liquid chromatography during manufacturing of Reolysin

Reolysin, a human reovirus type 3, is being evaluated in the clinic as an oncolytic therapy for various types of cancer. To facilitate the optimization and scale-up of the current process, a high performance liquid chromatography (HPLC) method has been developed that is rapid, specific and reliable for the quantification of reovirus type 3 particles. Using an anion-exchange column, the intact virus eluted from the contaminants in 9.78 min at 350 mM NaCl in 50mM HEPES, pH 7.10 in a total analysis time of 25 min. The virus demonstrated a homogenous peak with no co-elution of other compounds as analyzed by photodiode array analysis. The HPLC method facilitated the optimization of the purification process which resulted in the improvement of both total and infectious particle recovery and contributed to the successful scale-up of the process at the 20 L, 40 L and 100 L production scale. The method is suitable for the analysis of crude virus supernatants, crude lysates, semi-purified and purified preparations and therefore is an ideal monitoring tool during process development and scale-up.

Development of a suspension serum-free helper-dependent adenovirus production system and assessment of co-infection conditions

Helper-dependent adenovirus (HDAd), deleted in all viral protein-coding sequences has been designed to reduce immune response and favor long-term expression of therapeutic genes in clinical programs. Its production requires co-infection of E1-complementing cells with helper adenovirus (HAd). Significant progresses have been made in the molecular design of HDAd, but large scale production remains a challenge. In this work, a scalable system for HDAd production is designed and evaluated focusing on the co-infection step. A human embryo kidney 293 (293) derived cell line, the 293SF/FLPe was generated to produce efficiently HDAd while restricting the packaging of HAd. This cell line was adapted to grow in suspension and in serum-free medium. Multiplicity of infection (MOI) of HDAd ranging from 0.1 to 50 was evaluated in presence of HAd at a MOI of 5. Optimal MOIs for HDAd amplification were found in the range of 5-10. HAd contamination was only 1%. These results were validated in a 3 L bioreactor under controlled operating conditions where a higher HDAd yield of 2.6 x 10(9) viral particles (VP)/mL or 3.5 x 10(8) infectious units (IU)/mL of HDAd was obtained.

Validation of a high-performance liquid chromatographic assay for the quantification of Reovirus particles type 3

An anion exchange high-performance liquid chromatography (HPLC) method for the quantification of human Reovirus type 3 particles was validated according to the performance criteria of precision, specificity, linearity of calibration and working range, limits of detection and quantification, accuracy and recovery. Samples taken at various stages of Reovirus purification were used for the validation of the method. The method was specific for Reovirus which eluted around 9.8min without interference from any other component in the sample. Reovirus can be detected between 0.32E+12 and 2.10E12VP/mL by the proposed method that has the correlation coefficient of linearity equal to 0.9974 and the slope of linearity equal to 5.74E-07 area units/(VPmL).

A simple macroscopic model for the diffusion and adsorption kinetics of r-adenovirus

The diffusion of viruses toward cells is a limiting step of the infection process. To be modeled correctly, this step must be evaluated in combination with the adsorption of the virus to the cell surface, which is a rapid but reversible step. In this paper, the recombinant adenovirus (rAd) diffusion and its adsorption to 293S cells in suspension were both measured and modeled. First, equilibrium experiments permitted to determine the number of receptors on the surface of 293S (R(T) = 3,500 cell(-1)) and the association constant (K(A) = 1.9 x 10(11) M(-1)) for rAd on these cells based on a simple monovalent adsorption model. Non-specific binding of the virus to the cell surface was not found to be significant. Second, total virus particle degradation rates between 5.2 x 10(-3) and 4.0 x 10(-2) min(-1) were measured at 37 degrees C in culture medium, but no significant virus degradation was observed at 4 degrees C. Third, free viral particle disappearance rates from a mixed suspension of virus and cells were measured at different virus concentrations. Experimental data were compared to a phenomenological dynamic model comprising both the diffusion and the adsorption steps. The diffusion to adsorption ratio, a fitted parameter, confirmed that the contact process of a virus with a cell is indeed diffusion controlled. However, the characteristic diffusion time constants obtained, based on a reversible adsorption model, were eightfolds smaller than those reported in the literature, based on diffusion models that assume irreversible adsorption.

Virus-like particle and viral vector production using the baculovirus expression vector system/insect cell system: adeno-associated virus-based products

The ability to make a large variety of virus-like particles (VLPs) has been successfully achieved in the baculovirus expression vector system (BEVS)/insect cell system. The production and scale-up of these particles, which are mostly sought as candidate vaccines, are currently being addressed. Furthermore, these VLPs are being investigated as delivery agents for use as therapeutics. Recently, adeno-associated viral (AAV) vectors, which can be potentially used for human gene therapy, have been produced in insect cells using three baculovirus vectors to supply the required genes. The use of host insect cells allows mass production of VLPs in a proven scaleable system. This chapter focuses on the methodology, based on the work done in our lab, for the production of AAV-like particles and vectors in a BEVS/insect cell system.

Validation of a high-performance liquid chromatographic assay for the quantification of adenovirus type 5 particles

An anion-exchange-high-performance liquid chromatography (AE-HPLC) method for the quantification of adenovirus type 5 (Ad5) total particles was validated according to performance criteria of precision, specificity, linearity of calibration and range, limit of detection, limit of quantification, accuracy and recovery. The viral particles were detected by absorbance at 260 nm using photodiode array detector (PDA). Cesium chloride (CsCl) purified Ad5 and lysate samples were used for the validation of the method. Relative standard deviations (RSDs) for the inter-day, intra-day precision and reproducibility for both the lysate and the Ad5 standard were less than 10 and 2% for the peak area and retention time, respectively. The method was specific for Ad5 which was eluted at 8.0 min. The presence of DNA does not affect the recovery of Ad5 particles for accurate quantification. Based on the error in prediction to be less than 10%, the working range was established between 2 x 10(10) and 7 x 10(10) VP/ml with correlation coefficient of 0.99975, standard deviation of 6.14 x 10(9) VP/ml and a slope of 3.04 x 10(5) VP/ml. The recovery of the method varied between 88 and 106% in all of the lysate samples investigated which is statistically similar to 100% recovery at 95% confidence interval.

Improved high-performance liquid chromatographic method in the analysis of adenovirus particles

We developed a HPLC method on a novel continuous bed matrix (UNO Q, Bio-Rad) for the direct quantification of adenoviral type 5 (Ad5) particles produced in 293S Human Embryonic Kidney cells and compared this with an existing HPLC method on a conventional ion-exchange resin (Resource Q, Pharmacia). The 293S cell extract contained large amounts of DNA. This contaminated the viral peak on the Resource Q column and only after Benzonase treatment was it possible to quantify the viral particles in the cell extract. In contrast, the virus peak on the UNO Q column was resolved from the DNA which eliminates the need for pretreatment of the sample with Benzonase. Cross-analysis of the Ad5 fraction from the UNO Q column using a size-exclusion HPLC column revealed no additional contaminating peaks. We conclude that the purity of the Ad5 virus peak on the continuous bed matrix UNO Q column was superior to the purity of the virus on the conventional Resource Q column, which is essential for reliable quantification.

Social support processes: mediators of attachment state of mind and adjustment in late adolescence

This study examined the mediational link between attachment state of mind, social support processes and personal adjustment. The Adult Attachment Interview was administered to 62 adolescents during their college transition. At the end of high school and during their first semester in college, students completed questionnaires pertaining to primary and secondary appraisals; coping and personal adjustment were assessed through self- and peer-report questionnaires. A dismissing tendency was related to difficulty in getting assistance from peers and teachers and to peer-reported withdrawal. A preoccupied tendency was associated with stress regarding the transition, distrust in potential supporters, difficulty seeking help from teachers, and loneliness. Moreover, stress, distrust and help-seeking mediated the link between preoccupied attachment and loneliness, whereas the relation between dismissing attachment and withdrawal was not mediated by help-seeking. Cognitive and behavioral attachment processes are discussed.

Gonadotrophin storage patterns in the ewe during the oestrous cycle or after long-term treatment with a GnRH agonist

The storage pattern of gonadotrophins in the ewe pituitary was investigated during the oestrous cycle and after desensitization to GnRH using long-term treatment with a GnRH agonist, buserelin. Oestrous cycles in ewes were synchronized with progestagen sponges. Animals were allocated to two experiments. In the first, ewes were killed 36 h (before the preovulatory surge, n = 4), 48 h (end of the preovulatory surge, n = 5), 72 h (post-ovulation, n = 4) and 240 h (luteal phase, n = 3) after sponge removal. In the second experiment, another progestagen sponge was inserted in ewes 84 h after removal of the first sponge. Four ewes were infused continuously with buserelin (50 micrograms/day) for 15 days before killing. A further four ewes received no buserelin (controls). Pituitaries were collected and processed for immunocytochemistry to detect monohormonal (LH or FSH) and multihormonal (LH/FSH) cells. The percentages of LH or FSH immunoreactive cells in the pituitary were lower at the end of the preovulatory surge (7.4 +/- 0.3% and 1.2 +/- 0.3% respectively) compared with the other stages (11.4 +/- 0.5% and 5.4 +/- 0.7% respectively). Analysis of dual immunostaining showed the existence of monohormonal cells for LH and multihormonal cells (LH/FSH). No monohormonal cell for FSH was detected except at the end of the preovulatory surge when a few monohormonal FSH cells appeared (0.1 +/- 0.01% of pituitary cells). The percentage of monohormonal LH cells in the pituitary gland was similar in all studied stages of the oestrous cycle, whereas the percentage of multihormonal cells was lower at the end of the surge. In agonist-treated ewes, the percentages of LH or FSH immunoreactive cells (5.3 +/- 0.5% and 1.5 +/- 0.8% respectively) were decreased compared with controls (9.4 +/- 1% and 7.5 +/- 1.1% respectively). Analysis of the double immunostaining revealed a few monohormonal FSH cells (0.2 +/- 0.01% of pituitary cells) in agonist-treated ewes but not in controls. The percentage of monohormonal LH cells in the pituitary gland increased from 1.9 +/- 0.2% in controls to 3.8 +/- 0.3% in agonist-treated ewes, whereas multihormonal cells dropped from 7.5 +/- 1.1% to 1.3 +/- 0.7%. Our data suggest, therefore, that multihormonal cells contribute to gonadotrophin secretion, either during the preovulatory surge of the oestrous cycle or during the 'flare-up' effect initially induced by a GnRH agonist. Moreover, the appearance of monohormonal FSH cells in some conditions reflects a differential regulation of LH and FSH.

Aortic percutaneous transluminal valvuloplasty in elderly patients by balloon larger than aortic anulus

Twenty-four elderly patients (79 +/- 7 years) with long-standing calcified aortic stenosis have been divided in two comparable groups of 12. The first group was treated with 19 mm balloon percutaneous transluminal valvuloplasty, where the balloon diameter was always smaller than the aortic anulus diameter. Peak-to-peak aortic valve gradient decreased from 76 +/- 32 mmHg to 30 +/- 19 (P less than .05), and the aortic valve area, calculated by Gorlin formula, increased from 0.40 +/- 0.17 cm2 to 0.57 +/- 0.17 (P less than .05). The second group was treated with a trefoil 25 mm balloon, always larger than the aortic anulus diameter. In this second group, peak-to-peak aortic valve gradient decreased from 73 +/- 34 mmHg to 23 +/- 15 (P less than .05), and aortic valve area increased from 0.47 +/- 0.14 cm2 to 0.88 +/- 0.36 (P less than .05), increasing thus more than in group I (P less than .05). Clinical tolerance to balloon inflation was not the same according to individual patients but was similar between the two groups; complications were comparable in the two groups. These results suggest that aortic valvuloplasty by trefoil balloon larger than aortic anulus can provide wider aortic valve area without increasing complication rate.

A General Method of Four-Bar Linkage Mobility Analysis

The problem of mobility associated with four-bar linkages is addressed in this paper. The mobility analysis is reduced to finding the global extrema of a quadratic function on a cylinder, which then leads to the geometric problem of finding the intersections of a circle and a hyperbola. The method proposed here produces an efficient mobility analysis that can be readily integrated into any suitable optimization algorithm.

Opening snap and isovolumic relaxation period in relation to mitral valve flow in patients with mitral stenosis. Significance of A2--OS interval

In 15 patients with pure or predominant mitral stenosis and in a control group of 11 patients without mitral stenosis the blood flow velocity through the mitral valve orifice was recorded by means of a directional Doppler ultrasound velocity catheter introduced transeptally and positioned in the orifice of the mitral valve. A simultaneous surface phonocardiogram was obtained. The timing of the mitral opening snap in relation to the blood velocity record of the flow through the valve supported the hypothesis that the opening snap is due to a sudden tensing of the valve leaflets by the chordae tendineae. Determination of the exact time of mitral valve opening, made possible by the blood velocity record, led to the division of the classical A2-0S interval (aortic valve closure to opening snap) into two components representing respectively the diastolic isovolumic relaxation period and the time of excursion of the mitral valve cusps. The durations of the isovolumic relaxation period were compared with those in the control patients and were found to correlate with the severity of the mitral stenosis, whereas those of the excursion time of the mitral cusps were influenced by the presence or absence of mitral valve calcification.

Diagnosis and evaluation of mitral valve disease using transseptal Doppler ultrasound catheterization

In 33 patients with confirmed mitral valve disease, the mitral valve flow velocity traces were recorded by means of a directional Doppler ultrasonic velocimeter using the transseptal route, and correlated with the clinical and haemodynamic data. In all cases, characteristic anomalies of the mitral flow velocity patterns were noted and could be related to the type of lesion, stenosis, regurgitation, or a combination of these. Furthermore, specific patterns of the flow velocity traces were shown to correlate satisfactorily with the degree of severity of the disease. The authors propose a pathophysiological interpretation of the anomalies of the velocity patterns, based on turbulence for stenosis and backward flow wave for regurgitation. They conclude that the transseptal directional Doppler catheterization provides a new reliable method for establishing the diagnosis and grading the severity of mitral valve disease using pattern recognition, and, moreover, offers a new approach to the understanding of mitral haemodynamic disturbances on a beat-to-beat basis.

Normal pattern and physiological significance of mitral valve flow velocity recorded using transseptal directional Doppler ultrasound catheterization

In 10 cardiac patients in whom an organic lesion of the mitral valve was exluded by standard investigation procedures during which a diagnostic transseptal catheterization for pressure measurements in the left heart was performed, the authors placed a directional Doppler ultrasonic catheter tip velocimeter at the site of the mitral ring and recorded the mitral flow velocity traces. The pattern of these normal curves is presented and a physiological interpretation proposed. The relation between the mitral flow velocity and low volume curves is discussed in the light of present experimental data on mitral valve flow velocity profiles and variations in size of the mitral orifice. The authors concluded that the flow velocity curves obtained by the Doppler technique constitute a valid physiological reference system for the study of the mitral valve flow velocity tracings that can be recorded in the various forms of mitral valve disease.

SYPHILITIC ULCERATIONS WITH THE HISTOLOGICAL PICTURE OF A PRICKLE CARCINOMA CURED BY ANTI-LUETIC TREATMENT

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